courtesy of
ARK - Arizona Rivulin Keepers
The Scheel Letters, No. 52
Identification of West African Rivulins
For many years I have been faced with the problems concerning identification of
live or preserved individuals belonging to West African Rivulins. As you may know,
there are about one hundred and twenty nominal species (including subspecies) in
this group in Rivulinae. The last review concerning all (or most) known forms was
published back in 1915 by Boulenger. Up to that time only 36 nominal species had
been described by zoologists. All the remaining more than eighty species descriptions
for this reason are to be found here and there in numerous articles in the zoological
and aquaristic literature.
The problem of identification starts when you receive some live or preserved individuals
belonging to this group of Rivulins. If you are not familiar with this form you
need a "name" to place on these fish. You now may look up one description of one
of the West African Rivulins in literature and compare the data (measurements and
counts, colors, color patterns etc.) of your sample with those of the description.
Very often you will realize that your individuals are in rather fine agreement with
the data of the description and you may identify your fish as belonging to that
particular species. Well, sometimes you are not quite sure that this "identification"
was good enough and you look up a second description in literature and also in this
case you often will find rather fine agreements between your data and those of the
description. Indeed sometimes you may find that your material corresponds to up to
seventy different descriptions of West African Rivulins. It all depends on the
variation of morphological characters found in your analysis of your material and
those published for the nominal species.
You may indeed try to solve your problem in the way that you compare your material
with the standard for various species in question. These standards are the "types"
which are stored in zoological museums. These standards however are not to be seen
in a single museum. They are scattered all over the zoological Museums of the Old
and the New World. As these standards normally are not sent out of museums you
have to go to see the types where they are stored. Sometimes your consultation
of the type will solve your problem, but very often you will realize that the types
themselves are not very informative because through time and the frequent use for
identification they have lost most scales and fin rays and also rather often their
original colors and color patterns are no longer visible. Also it may be that
the types -and in particular the older ones- appear rather badly deformed from
improper conservation or by shrinkage. Some liquids used for preservation deform
the material more than other liquids. As the oldest types have been preserved
in 70% alcohol, they will be more deformed than those preserved in formole or 30-40%
isopropanole. Preservation in formole however will destroy all red and yellow
pigments and also may develop black color patterns that will not develop during
preservation in alcohol. Individuals preserved in isopropanole will be "flabby"
and difficult to handle without damage to the type. If identification has to be
based too often on the type material we soon will have no informative type material
left.
This situation demands that descriptions of West African Rivulins should be prepared
in such a way that they can be used as standards for identification. For the
present, most descriptions of these fishes do not at all fulfill this claim as
they can not be used for identification. A revision of all descriptions and
redescriptions is badly needed. This however claims that recollection at the type
localities (if known!!) is needed to prepare an analysis of the "characters" used
in descriptions. Some of the about one hundred and twenty forms have been described
as subspecies or "varieties". For the present time some of the nominal subspecies
apparently are representing good species, whereas some of the nominal species indeed
may represent subspecies. For this reason I will consider all names so far created
for West African Rivulins as representing nominal species. Also forms which have
been placed as synonyms for other names will here be treated as nominal species
because at least some of the synonyms are not correct. All these nominal species
have been placed in several genera and most have been placed in the genera Epiplatys
and Aphyosemion. These groupings may prove to be correct for most forms, however in
the following analysis of characters, there is no need to consider genera as it is
impossible for the present to place all forms under consideration in known genera.
The group "West African Rivulins" has been used here in a rather wide sense. The
group here studied contains nominal species found in the Senegal, the Niger, the
Congo River drainages and in the smaller river systems west of these major river
systems. Also the Chad drainage is taken into consideration. This geographical
limitation excludes most forms in Nothobranchius and all forms in Pachypanchax.
All information on these forms has been collected on loose leaves for each nominal
form. To this information from the original descriptions I have added reliable data
from other publications concerning these forms and my own measurements and counts
on my own material and material which I had the opportunity to inspect. When this
has been done it is possible to study each character used in the ordinary description
of a West African Rivulin and to calculate the "value" of each character in taxonomy.
As these characters have been used to demonstrate differences between a "new species"
and older ones, the value of the character will depend on the ability to fulfill
this claim. This value again will depend on the variation of that character within
a single species, compared with the total variation for the whole group plus the
distribution of the data for each species within the total range of variation.
If the specific variation (species variation) is great compared with the group
variation, the "value" of that character will be low and in particular if the data
for most species are heaping up near the average value for variation.
Before such comparisons are made the morphological characters should be studied
in order to see if the data have been collected in just the same way by different
authors. Various zoologists however use various methods for counting and measurements.
When counting fin rays some count all rays which stand isolated from other rays at
the root of the fin. Other zoologists do not consider "small rays" and often the
two last rays of the fin are considered as a single ray ("branched ray"). These
differences in methods may render differences of up to three or four rays when
the methods are used on just the same material. Also when counting scales different
methods are in use (have been in use) and the same is true for most measurements of
body proportions.
Some species have been redescribed by zoologists. Redescriptions based on the
type material have disclosed gross inconsistencies in the original descriptions.
As an example I should like to give the data that Ahl (author) and Holly published
for some of the types of Ahl's West African Rivulins.
| Species | Ahl | | Holly |
| D | A | D | A |
| Fundulus beauforti (1924) | 9 | 12 | 12 | 16 |
| Fundulus riggenbachi (1924) | 11-13 | 11-13 | 13-15 | 13-14 |
| Panchax elberti (1924) | 6-7 | 11-12 | 11-12 | 16-17 |
| Fundulus tessmanni (1924) | 8 | 15 | 12 | 17 |
| Fundulus normani (1928) | 6-7 | 11-12 | 11-12 | 16-17 |
These differences however probably are not the result of different methods used
for these counts, as Holly (1930) found himself in agreement with the corresponding
counts for other species described by Ahl from 1924-28. Holly's corrections of Ahl's
type descriptions not only concern counts, but also various measurements of body
proportions. Such disagreements between the data published by different zoologists
for the same material are not only found in Ahl's descriptions and Holly's redescriptions,
but occur -less marked- when Meinken's and Boulenger's data were studied.
Often redescriptions include new material, identified as belonging to the form in
question. Some of these redescriptions however published data concerning two different
species. Boulenger's data for SEX (Catalogue III/1915) contain data (and individuals)
of CHA. His description of CHA probably is based mostly on individuals belonging to
DAG etc. I have not used such redescriptions for the analysis.
The data for body proportions sometimes are given with more accuracy than measurements
are able to render. For example Meinken in his description of MUC was using live
individuals. However, for these individuals he gave data with an accuracy of 1/4
millimeter (on up to 13 mm, that is "13 1/4 mm"), whereas for his preserved material
he had an accuracy of 1/8 mm. Such accuracy indeed appears to be beyond what can be
obtained.
Other data are given with less accuracy than easily could be obtained from the material.
For the position of the anterior-most dorsal fin ray in proportion to the anal fin, the
description often says that the first dorsal fin rays stand above the middle of the
anal fin, regardless that it is evident that the author did not think of the geometrical
center of the root for that fin.
Most descriptions of new species (names) have been published without any picture
showing the type. Such pictures indeed are valuable for identification if they
have been prepared on fresh material. A good picture indeed may give away more
information than pages of written descriptions.
Most new species have been based on a very limited material. About 27% of the
species have been based on a single individual only. About 18% have been based
on two individuals, about 11% on three individuals, and about 13% on four. This
means that almost 70% of these nominal species have been based on less than five
individuals. Also about 70% of the nominal species have never been recaptured
in nature!!!
As you will realize in the section dealing with the crossings, Rivulins are indeed
rather variable fish in measurements and in counts. A few individuals, often from
a single deme (local population) will not give any idea of the true variation of
data. As most of these fish live in small, often more or less isolated bodies of
water, the exchange of genes between these micropopulations will not be absolutely
free and local differences may accumulate. Also there are reasons to believe that
some of ...(can not read the last line of page 181!!!) ... important to the fish
itself and not the object for severe selection, as conspicuous variation is found
even within the deme. Such characters indeed are not very important in taxonomy.
All nominal species have been based on differences from other known species only.
However, apparently no attempt has been made to calculate the degree of differences
that would support such claimed "differences" between two forms. Generally the
"differences" which have been used for the separation of two or more forms are
smaller (often much smaller) than the real differences between two individuals
belonging to a single deme of a single species. Also differences in color patterns
have been used to support the creation of new species. However the nature of the
different color patterns and color markings within these Rivulins has not been
discussed. As measurements and counts are highly variable even on demes' level,
also the color patterns undergo variation if many individuals are compared. The
use of differences in these characters should be based on a study of this type of
variation also. Many of these species are polymorphic in males ("yellow" and "blue"
males, etc.). About 1924-30 the collections of West African Rivulins in the largest
museums permitted a study of the variation within species, but apparently no such
study has been prepared.
Within Europe, the descriptions of new West African Rivulins have been rather
standardized within this century. Most zoologists used the characters used by
Boulenger. At the time when this system of Boulenger was prepared, only about
twelve different species belonging to this group were known. Boulenger's system
indeed is capable to contain much more than a hundred species, sufficiently separated
in morphology from each others, by at least one character.
Fowler used a somewhat different system for his descriptions of West African Rivulins.
This system contains more characters than Boulenger's system. It is however difficult
to compare Fowler's descriptions with those prepared by the Boulenger system because
Fowler's new characters are not known for the whole lot of forms described in Europe
and also Fowler expresses his findings in measurements and counts in a somewhat
different way which makes comparisons difficult.
Boulenger used the following factors suited for a statistic study:
1) the standard length of the body/the greatest depth of the body
2) the standard length of the body/the length of the head
3) the diameter of the eye/the length of the snout
4) the length of the head/the diameter of the eye
5) the interorbital width/the diameter of the eye
6) the number of dorsal fin rays
7) the number of anal fin rays
8) the position of the dorsal fin to the anal fin
9) the least length of the caudal peduncle/the least depth of the caudal peduncle
10) the number of scales in a longitudinal series
11) the number of scales around the body in front of the ventrals
12) the maximum length of the body (without caudal)
Further characters used by Boulenger and others will be considered later on in this report.
1) Standard length/greatest depth of body
The data for this character normally will be given as two numbers indicating the
variation found by the author. Many descriptions, however, have been based on
semiadults and juveniles and for this reason the variation might be considerable
and not very useful for use in taxonomy. For my own measurements I have used well
fed, full grown individuals only. These fish have been kept for some time in aquarium
so that they should be able to develop full length of fins etc. All measurements
are taken from close up photos, prepared in the way that the fish stands at a right
angle to the optical axis. Also these measurements show much variation, depending
on the sex of the individual, the number of eggs in females and individual variation
probably of genetic origin. Individuals which have been preserved in formole
normally will not deform much, whereas those preserved in alcohol often will be
badly deformed by shrinking. For comparison I prefer the maximum value for this
characteristic, thus taking only in consideration the individual which shows the
greatest depth of the body. For newly hatched fry from most (all?) forms and for
very small juveniles this character is rather constant and value 4.8-5.3.
Here are the minimum values for the forms under consideration:
5.8: MAG
5.5: LIB
5.4: GER
5.0: BEL, BUA, CAS, CHA, DUB, FLV, MAE, MEI, TAE, UNC
4.9:
4.8: CHI, FAL, MIC, NII, ORN, PRE
4.7: ACU
4.6: SPM
4.5: ANN, AUS, BAT, BIT, CAM, CAR, ELB, ELE, ESC, INF, LOB, LOL, MAT, NIG, NOR, OBS, PAP, PAS, PET, POL, SAN, SIN, SUP
4.4: COG, LAB
4.3: BAU, GUI, LON, MAR, MEL, NDE, NYO, OGO, RUS, VEX
4.2: DAG, MAC, ZEN, ZIM
4.1: BEA, HOL, SRE
4.0: ANS, BIF, BRU, CHE, CHR, CIN, DEF, DOR, EXI, GAR, JAC, JAU, LOE, LOU, LUJ, MUC, MUF, NIG, NIM, LOB, RIG, ROL, RUF, SEX, SJO, SPP, SPL, SPU, STR, TES, UNS
3.9: GRA, LAM, SEN, SHE
3.8: BOU, CAB, FAS, CUS, KIY
3.7: ARN, BIV, DEC
3.6: WAL
3.5: AHL, CAL, GUL
3.4:
3.3: COE, GAM, THI
3.2: FIL
2.6: RUR
Fowler probably used not the standard length, but the total length for his measurements
on MAG type. The published data do not correspond to the figure.
The descriptions cannot be used for a judgment of the specific variation (variation
within a well known species). My own measurements however indicate that a specific
variation of 1.1 is natural (well fed individuals of adult size differed from 0.7
to 2.2 "units"). If a "separation value" of 1.1 is used for separation of two forms
we might have 711 different separations from this character. As about 7000 separations
are needed, if all forms should be "separated" by a single morphological character,
this character gave about 10% of the separations that are needed. As the ratio of
the group variation to the specific variation is 3.3/1.1 = 3, the efficiency of this
character is rather low, also because most forms are heaping near the center of
variation 79% of all forms are concentrated within the specific variation.
2) Standard length/length of head
This character is highly variable. The group variation 2.6 (between 2.8 and 5.3).
The specific variation for the best known forms are:
CAL: 3.3-5.3 = 2.1
GRA: 3.0-4.8 = 1.9
CIN: 3.3-5.0 = 1.8
BIV: 3.0-4.6 = 1.7
SHE: 3.2-4.8 = 1.7
BOU: 3.0-4.5 = 1.6 (types)
ROL: 3.5-5.0 = 1.6
FAS: 3.0-4.4 = 1.5
NIG: 3.2-4.6 = 1.5
SEX: 3.3-4.6 = 1.4
I assume that the specific variation will be 1.7 at least. This means that
the ratio of group variation to specific variation is 2.6/1.7 = 1.5 and we will
not expect a high number of "separations". I found a total of 280 separations.
This means that this character is not very useful in taxonomy indeed. For this
reason I will only give the distribution of the forms near the extremes of the
group variation:
5.3: CAL
5.2: CAL, GER
5.1: CAL, GER
5.0: CAL, CHR, CIN, GER, ROL
4.9: CAL, CHR, CIN, GER, ROL
4.8: CAL, CHR, CIN, COG, GER, GRA, ROL, SHE
4.7: AUS, CAL, CHR, CIN, COG, GER, GRA, POL, ROL, SHE
2.9: ARN, DEF, NDE
2.8: DEF
3) Diameter of eye/length of snout
Most descriptions do not publish exact information on this ratio. It is said "
that the snout is longer (equal to or shorter) than the eye". For 31 different
species that I kept alive in my tanks I calculated this character. The group
variation was 0.8-2.5 and I found these specific variations:
BIF: 1.0-2.0 = 1.1
BIV: 1.2-2.2 = 1.1
SEN: 1.0-2.0 = 1.1
SEX: 0.9-1.8 = 1.0
LUJ: 1.6-2.5 = 1.0
CHR: 1.4-2.2 = 0.9
COG: 1.4-2.2 = 0.9
FIL: 1.2-2.0 = 0.9
Three more species had a variation of 0.8 and five more species had 0.7. As my material was rather limited, I assume that the specific variation will be 1.0 or 1.1. As the group variation was only 1.8, it is evident that also this character cannot be of any importance in taxonomy. Not even a differentiation between nominal Aphyosemion and nominal Epiplatys was noticed.
4) Head/eye
From what has already been said about the variation of the eye and of the length of
the head, it is likely that also this character will not be important in systematics
of West African Rivulins. The group variation is 2.5-4.7 = 2.3 only. The specific
variation could be calculated from these data:
ARN: 2.5-4.5 = 2.1
RUR: 2.6-4.4 = 1.9
COE: 3.1-4.7 = 1.7
BIF: 2.5-4.0 = 1.6
SHE: 2.9-4.3 = 1.5
GRA: 2.5-3.8 = 1.4
Apparently the "Nothobranchius-Fundulopanchax-like" forms differ more than Epiplatys
and the usual Aphyosemion forms. For this reason I assume that the specific variation
could be 1.4, more or less. However, this specific variation gives only 209 separations.
If a specific variation of 1.5 had been used, the number of separations would be 100 only.
A specific variation of 1.6 only gives 72 separations. The grouping of nominal
species near the extremes for the group variation:
4.7: COE
4.6: COE
4.5: ARN, COE, GAM, GUI
4.4: ARN, COE, GAM, GUI, ROL, RUR
4.3: ARN, COE, GAM, GUI, ROL, RUR, SHE
4.2: ARN, COE, GAM, GUI, NIG, ROL, RUR, SJO, SHE
2.7: ANN, ARN, BIF, BIV, DUB, GRA, RUR
2.6: ARN, BIF, BIV, GRA, RUR
2.5: ARN, BIF, GRA
5) Interorbital width/diameter of eye
I did not measure these data on my own material. Descriptions give data that can
be used in statistics.
RUR: 1.1-2.8 = 1.8
FIL: 1.2-2.0 = 0.9
GER: 1.2-2.0 = 0.9
GUI: 1.7-2.4 = 0.8
PET: 1.4-2.0 = 0.7
BIV: 1.3-1.8 = 0.6
BOU: 1.0-1.5 = 0.6
CAM: 1.5-2.0 = 0.6
ESC: 1.5-2.0 = 0.6
I assume that the specific variation will be 0.8, but it is likely that a study
on more material will raise this value considerably. The distribution of the forms
near the extremes of the group variation is:
2.8: RUR
2.7: RUR
2.6: RUR
2.5: RUR
2.4: GUI, RUR
2.3: GUI, RUR
2.2: GUI, RUR
2.1: GUI, RUR
1.2: ARN, BIT, BOU, FIL, GER, GUS, RUR, RUS, THI
1.1: BIT, BOU, RUR, THI
1.0: BIT, BOU, THI
This grouping shows that almost all forms are heaping within the range from
1.3 to 2.0 = the specific variation. The number of separations for this reason
is very low: 151 separations only and also most of these "separations" come from
RUR. This character probably is without any importance in systematics.
6) Number of dorsal fin rays
Apparently this character has been considered as very important in taxonomy of
West African Rivulins and indeed this character gives many more separations than
any of the previously mentioned characters. The group variation runs between 6
and 22 dorsal fin rays. The specific variation however is larger than estimated
in descriptions. Using my own counts on more than 3000 individuals and the reliable
data from descriptions and redescriptions the following specific variations were found:
FAS: 10-15 = 6
BIF: 06-10 = 5
BIV: 09-13 = 5
COE: 14-18 = 5
NIG: 12-16 = 5
ROL: 11-15 = 5
RUR: 16-20 = 5
WAL: 12-16 = 5
AUS: 09-12 = 4
ARN: 15-18 = 4
CAB: 09-12 = 4
CHE: 07-10 = 4
CHR: 08-11 = 4
FIL: 14-17 = 4
GRA: 07-10 = 4
GUL: 15-18 = 4
LAM: 10-13 = 4
LON: 07-10 = 4
MUF: 08-11 = 4
NIC: 07-10 = 4
PET: 07-10 = 4
SCH: 08-11 = 4
SEN: 09-12 = 4
SEX: 09-12 = 4
SHE: 10-13 = 4
SJO: 19-22 = 4
I assume that the specific value of variation will be "5 rays". This specific
variation will give 1798 "separations" if the total variation within each species
is taken into consideration. If only the data published in descriptions are used
the number of separations will be 1242. I found this grouping of the forms along
the axis of variation:
22: SJO
21: SJO
20: RUR, SJO
19: RUR, SJO
18: ARN, COE, GUL, RUR, SJO
17: ARN, COE, FIL, GUL, RUR, SJO, SPL
16: ARN, COE, FIL, GAM, GUL, GUS, NIG, RUR, SRE, SPL, SPU, WAL
15: ARN, BAT, BEA, CIN, COE, FIL, FAS, GAM, GER, GUL, GUS, KIY, NIG, RIG, ROL, SPL, SRE, SPU, WAL
14: BAT, CIN, COE, DOR, FAL, FAS, FIL, GER, GUI, KIY, LAB, NIG, RIG, ROL, SPU, WAL
13: BIV, BRU, CIN, FAL, FAS, GAR, GER, GUI, HOL, KIY, LAB, LAM, NIG, RIG, ROL, SEX, SHE, SPU, WAL
12: AUS, BEL, BIV, BRU, CAB, CAM, ELB, ESC, FAS, GAR, GUI, HOL, LAB, LAM, LOE, MEI, NIG, NOR, OLB, PAP, PAS, ROL, RUF, SEX, SHE, THI, WAL, ZIM
11: ANS, AUS, BEL, BIV, BOU, BUA, CAB, CAM, CAR, CHR, DAG, ELB, ESC, FAS, HOL, INF, LAM, LIB, LOE, LOU, LUJ, MAE, MAC, MIC, MUF, NII, OBS, OGO, OLB, PAS, POL, PRE, ROL, RUF, RUS, SCH, SEN, SEX, SHE, SPI, SPP, STR, TES, THI, UNS, ZIM
10: ACU, AHL, AUS, BIF, BIT, BIV, BOU, CAB, CAL, CHE, CHR, CON, DAG, DUB, FAS, FER, GRA, LAM, LON, LUJ, MAC, MAG, MUC, MUF, NDE, NIG, OGO, OLB, PET, POL, RUF, RUS, SCH, SEN, SEX, SHE, SPI, SPM, STR, UNS, COG
09: ACU, AHL, AUS, BIF, BIT, BIV, BOU, CAB, CAL, CHE, CHR, COG, CON, DAG, DEC, DUB, GRA, JAU, LOL, LON, MAC, MAT, MUF, NIC, NIM, ORN, PET, SAN, SCH, SEN, SEX, SIN, STR, TAE, UNC, VEX, ZEN
08: BAU, BIF, CAL, CAS, CHE, CHI, CHR, COG, DEF, DEC, ELE, EXI, GRA, LOB, LOL, LON, MAC, MAR, MAT, MUF, NIC, NYO, PET, SCH, SEN, SIN, TAE
07: ANN, BIF, CHA, CHE, DEF, FLV, GRA, LON, MAR, MEL, NIC, PET, SEN, SUP, TAE,
06: BIF, JAC
There are two maxima. One large maximum is found at 10 dorsal fin rays. 46 nominal
species -at least- may develop this number of dorsal fin rays. There is a smaller
maximum at 15 dorsal fin rays, produced by Callopanchax, Fundulopanchax and Nothobranchius.
7) Number of anal fin rays
The group variation of this character is more narrow than found for the dorsal fin.
The variation goes from 10 to 20 fin rays. The specific variation however reaches
just the same magnitude as found for the dorsal fin. For this reason we should
expect less separations from this character.
BIF:
FAS: 14-19 = 6
SEX: 15-20 = 6
WAL: 14-19 = 6
BIV: 14-19 = 6
GRA: 11-15 = 5
NIG: 14-18 = 5
ROL: 14-18 = 5
RUR: 16-20 = 5
SEN: 15-19 = 5
SHE: 14-18 = 5
ARN: 15-18 = 4
BOU: 14-17 = 4
CAM: 14-17 = 4
CHE: 13-16 = 4
COE: 16-19 = 4
DAG: 14-17 = 4
FIL: 14-17 = 4
GUI: 14-17 = 4
GUL: 16-19 = 4
LAB: 14-17 = 4
LAM: 14-17 = 4
LON: 15-18 = 4
MAC: 15-18 = 4
MUF: 14-17 = 4
NIC: 13-16 = 4
I assume that the specific variation will be "5 rays". This value however gives
only 497 separations. The reason for this poor result is found in the distribution
of the nominal species around the mean value for anal fin rays. 63 nominal species
may develop 15 anal fin rays and 56 and 57 nominal species may develop 14 or 16 anal
fin rays. For this reason I only give the distribution of species near the extremes
of the group variation:
20: FAS, RUR
19: BIF, COE, FAS, GRA, GUL, RUR, SEN, SEX, SJO, WAL
18: ARN, BIF, COE, DOR, FAS, GRA, GUL, LON, MAC, NDE, NIG, ROL, SRE, SEN, SEX, SHE, SJO, WAL
12: AHL, BIT, BIV, CAL, EXI, JAC, LOE, RUS, UNC
11: BIV, JAC, RUS
10: MEL, RUS
8) Position of the anteriormost dorsal fin ray
I have already mentioned that this important character normally is not published
with sufficient accuracy in descriptions. In my opinion it is evident that this
particular character is the most important in the systematics of West African Rivulilns.
The group variation of this character covers 19 fin rays (measured on the anal fin base)
and thus exceeds the group variation of the dorsal fin rays by two rays. However,
in this character the distribution of the nominal species is more even within the
whole range of variation thus indicating that many "separations" are possible.
Not very much information on the specific variation can be harvested from descriptions
and redescriptions. For this reason I prepared my own measurements on my close-up photos
and on preserved material. I project the base of the anterior-most dorsal fin ray -along
scale rows- to the base of the anal fin. I then find the anal fin ray that comes closest
and count "backwards" to the anterior-most anal fin ray. In case that the anterior-most
dorsal fin ray stands in front of the anterior-most anal fin ray (ARN, FIL, GAM, SJO,
KIY, RUR) I project the latter on the dorsal fin base and give the value in "negative
anal fin rays".
On my material I found these specific variations:
COE: 01-06 = 6 rays
DAG: 06-11 = 6 rays
FAS: 08-13 = 6 rays
ARN: 01-05 = 5 rays
BIV: 02-06 = 5 rays
FIL: 01-05 = 5 rays
NIG: 03-07 = 5 rays
ROL: 04-08 = 5 rays
SEX: 08-12 = 5 rays
SHE: 06-10 = 5 rays
I assume that the specific variation will be 5 (or 6) rays. I count this grouping
of the nominal forms along the axis of....(?)
15: ORN
14: GRA, ORN, PET
13: BOU, FAS, GRA, NIM, PET, SEN, SIN, SUP
12: BOU, CHE, CHR, DAG, FAS, GRA, LON, MAC, MUF, PET, SEN, SEX, SIN, TAE
11: ACU, BAU, BIF, BOU, CHA, CHE, CHI, CHR, DAG, FAS, GRA, LON, MAC, MUF, PET, SEN, SEX, ZEN
10: ACU, BAU, BIF, BOU, CHE, CHR, COG, CON, DAG, FAS, MAR, MUF, NIC, PET, SAN, SEN, SEX, SHE, ZEN
09: AUS, BIF, CAL, CHR, COG, CON, DAG, DEF, DUB, ELB, FAS, JAC, LAM, MAR, MUF, NDE, NOR, PET, SEX, SHE, VEX
08: ANN, AUS, CAL, CAM, CAR, CAS, CHR, COG, CON, DAG, DUB, ELB, ELE, FAS, JAC, LAB, LAM, LOB, LOL, LUJ, MAE, MUF, NOR, NYO, OBS, OLB, PET, ROL, RUF, SEX, SHE, SPI, SPM, VEX
07: AHL, AUS, CAB, CAL, CAM, CAS, CHR, DAG, DOR, DUB, ELE, FER, FLV, INF, JAU, LAB, LAM, LOB, LOL, LOU, LUJ, MAE, MAT, MAG, MIC, NIG, OBS, OGO, OLB, ROL, SHE, SPI, SPM, STR
06: AHL, BIV, CAB, CIN, COE, DAG, EXI, FER, GUI, LAB, MAT, MAG, NIG, OGO, OLB, PAS, ROL, SHE, STR, UNC
05: BEL, BIV, BRU, BUA, CAR, CIN, COE, DAG, ESC, GUI, LAB, LIB, MEI, MEL, NIG, OGO, PAS, PRE, ROL, STR, TES
04: BEL, BIV, BRU, CIN, COE, GER, LIB, NIG, ROL
03: BIT, BIV, COE, HOL, NIG, NII, SPP
02: BEA, BIT, BIV, COE, GAR, MUC, NII, RUS, SRE, SJO, SPL, SPU, WAL
01: ARN, BAT, COE, FAL, FIL, GUL, GUS, LOE, PAP, RIG, RUR, SJO, SPL, THI, UNS, ZIM
-2: ARN, FIL, GUL, KIY, RUR, SJO
-3: ARN, FIL, GUL, SJO
-4: ARN, FIL, GUL, SJO
-5: ARN, FIL, GAM, SJO
On this base 2963 different separations between nominal species were prepared.
This amount of "separations" however would increase if more information on the
specific variation had been published. Indeed this character gives more separations
than any other purely morphological character. The distribution of the nominal
species along the axis of variation develops two distinct maxima. One large maximum
is seen at D/A=7-8 anal finrays and a smaller one as D/A=1 anal fin ray. There
might be a third maximum near D/A=10-12 also.
These maxima indeed indicate a grouping in taxonomy that probably corresponds to
the Fundulopanchax (including however also species in Callopanchax and Fundulosoma
plus Nothobranchius) and a certain group in Epiplatys (D/A=10-12 A).
9) Ratio of measurements for the caudal peduncle
Most descriptions do not publish exact values for this character. It is said
that the caudal peduncle is (much) longer (shorter) than deep. From my own measurements
on close-up photos of adult well fed individuals I realized that the specific variation
of this character is rather limited compared to the characters previously mentioned.
Indeed this specific variation includes also the slight differences in this character
sometimes found between the two sexes.
BIV: 1.4-2.0 = 0.7
ROL: 1.3-1.9 = 0.7
RUR: 1.1-1.7 = 0.7
SHE: 0.9-1.4 = 0.6
SPL: 1.5-2.0 = 0.6
AUS: 1.3-1.7 = 0.5
CAL: 1.3-1.7 = 0.5
ARN: 1.7-2.2 = 0.6
GAB: 1.7-2.2 = 0.6
CAM: 1.5-2.0 = 0.6
CIN: 1.7-2.1 = 0.5
DUB: 1.4-1.8 = 0.5
FIL: 1.3-1.7 = 0.5
GRA: 1.2-1.6 = 0.5
CHR: 1.5-2.0 = 0.5
COG: 1.3-1.8 = 0.6
GAM: 1.0-1.5 = 0.6
GUI: 1.0-1.4 = 0.5
NIG: 1.5-1.9 = 0.5
SEX: 1.0-1.4 = 0.5
I assume a specific variation of 0.6 units. A study of more material probably
will raise this figure to 0.7. The group variation runs from 0.9 to 2.2 = 1.4 units.
2.2: ARN, CAB
2.1: ARN, CAB, CIN
2.0: ARN, BEL, BIV, CAB, CAM, CHR, CIN, CON, ESC, LIB, LOU, LUJ, MEI, MIC, SRE, SPL,
1.9: ARN, BEL, BIV, CAB, CAM, CHR, CIN, CON, ELE, ESC, LOE, LUJ, MIC, NIG, NOR, ROL, SPL, ZIM
1.8: ARN, BEL, BIV, CAB, CAM, CHR, CIN, COE, COG, CON, DUB, ELB, ESC, GER, LOU, LUJ, MIC, NIG, NYO, ROL, SAN, SPL
1.7: ANN, ARN, AUS, BIV, CAB, CAL, CAM, CAR, CAS, CHR, CIN, COE, COG, DUB, FER, FIL, GER, GUS, JAC, JAU, LOU, LUJ, MAE, NIG, OBS, POL, PRE, ROL, RUR, SPP, SPL
1.6: AUS, BIF, BIV, CAL, CAM, CHR, COE, COG, DUB, FIL, GER, GRA, GUL, LAB, NIG, POL, ROL, RUR, SPP, SPL
1.5: AHL, AUS, BEA, BIF, BIT, BIV, BRU, CAL, CAM, CHI, CHR, COG, DEC, DUB, EXI, FIL, FLV, GAM, GER, GRA, HOL, LAB, LOB, LOL, MUC, NIG, NIM, PAP, PAS, POL, ROL, RUF, RUR, SJO, SPP, SPL, SUP, TES, UNC, UNS
1.4: AHL, AUS, BIF, BIV, CAL, CHE, COG, DUB, FAS, FIL, GAM, GRA, GUI, ROL, RUR, SEX, SHE, SJO,
1.3: AHL, AUS, BAT, BIF, CAL, CHE, COG, DAG, FAS, FIL, GAM, GRA, GUI, LAM, MAC, MIC, ORN, RIG, ROL, RUR, RUS, SEX, SHE, SJO, STR, WAL
1.2: DAG, FAS, GAM, GRA, GUI, LAM, LON, NIC, RUR, SEN, SEX, SHE, WAL
1.1: BOU, DAG, FAS, GAM, GUI, LAM, LON, NIC, RUR, SEN, SEX, SHE, SPU, WAL
1.0: ACU, ANS, BAU, DAG, DEF, DOR, FAL, GAM, GAR, GUI, KIY, LAM, MAR, MUF, NII, NIC, OLB, PET, SEN, SEX, SHE, SIN, SPI, TAE, THI, ZEN
0.9: SHE
The four maxima (0.1-1.3-1.5-1.7) do not indicate taxonomic units. They are produced
by the inaccuracy of the data of descriptions (1-1 1/4-1 1/2-1 3/4 or 1 2/3). The
species in nominal Aphyosemion are concentrated at the higher values, whereas the
species in nominal Epiplatys are concentrated at lower values. Among nominal Epiplatys
only GRA reaches the value of 1.6 (DUB is not a true Epiplatys). From this distribution
and a specific variation of 0.6 I had 1617 separations. This result indicates
that this character should be taken into consideration in the systematics of this
group of Rivulins.
10) Scales in a longitudinal series
I am not quite sure that the data published for scales in a longitudinal series
in various descriptions and redescriptions are comparable as this character can
be counted in different ways. If scales situated on the caudal fin are not taken
into consideration, differences between the different methods should be not be
important. For my own counts of scales I start from the scale that is situated
just above the upper part of the root of the pectoral fin and count in a median
series (usually the row which has pits, if pits are present). I always count both
sides in order to have an idea of the individual variation of this character.
The specific variation given on the next page is based on my own counts for most
species. The variation found in COE and GUL is very large, probably because in these
species the development of the scales often is very irregular and small and larger
scales occur on the body sides. The variation found in GUL is that of a single deme
from Ago-Iwoye of SW Nigeria. The data for CAM, RUR (types only), BEL (types only),
BRU and GAR have taken from literature.
COE: 31-37 = 7
GUL: 29-35 = 7
ARN: 24-29 = 6
BIV: 24-29 = 6
CAM: 29-34 = 6
CHA: 25-30 = 6
NIG: 29-34 = 6
RUR: 29-34 = 6
SEX: 27-32 = 6
SHE: 25-30 = 6
BEL: 30-34 = 5
BIF: 25-29 = 5
BRU: 30-34 = 5
CAL: 27-31 = 5
CHE: 27-31 = 5
DAG: 25-29 = 5
DEC: 28-32 = 5
FAS: 27-31 = 5
FIL: 24-28 = 5
GAR: 28-32 = 5
GRA: 26-30 = 5
The specific variation for GUI, LAM, LON, LUJ, SPM also reaches 5 scales. The
specific variation probably will not be below 6 scales. This value gives 1366
separations. A specific variation of 5 scales only (which I assumed one year ago)
would give 2181 separations.
The following distribution of species was found:
37: COE, SPL
36: BEA, COE, GUS, SPL
35: BAT, COE, GUL, GUS, SRE, SJO, SPL
34: BAT, BEL, BRU, CAM, COE, FAL, GER, GUI, GUL, GUS, MEI, NIG, RUR, SRE, SJO, SPL
33: BAT, BEL, BRU, CAM, CIN, COE, GER, GUI, GUL, LIB, NIG, POL, RUR, SRE, SJO, SPL
32: AUS, BEL, BRU, BUA, CAM, CIN, COE, DEF, ELE, ESC, FER, GAM, GAR, GER, GUI, GUL, LAB, LAM, LIB, LUJ, MIC, NIG, PET, POL, ROL, RUR, SEX, SJO, SPU, VEX, ZIM
31: ANS, AUS, BEL, BRU, CAL, CAM, CHE, CHR, CIN, COE, COG, CON, DEC, ELB, ELE, ESC, FAS, FER, GAM, GAR, GER, GUI, GUL, LAB, LAM, LOU, LUJ, MIC, NIG, OBS, OGO, PAS, PET, POL, ROL, RUR, SAN, SEX, SPU, STR, ZIM
30: AHL, ANS, AUS, BEL, BRU, CAB, CAL, CAM, CAR, CAS, CHA, CHE, CHR, CIN, COG, CON, DEC, ELB, ELE, ESC, FAS, FER, GAM, GAR, GRA, GUI, GUL, JAU, LAB, LAM, LUJ, MAC, MAE, MAT, MEL, MUF, NIG, NII, NIC, NIM, NOR, OGO, OLB, PAS, PET, PRE, ROL, RUF, RUR, SCH, SEX, SHE, SPL, SPU, STR, TES, WAL, ZEN, ZIM
29: ACU, AHL, ANN, AUS, BIF, BIV, BOU, CAL, CAM, CHA, CHE, CHR, COG, CON, DAG, DEF, DEC, ELB, ELE, FAS, FLV, GAR, GRA, GUL, HOL, LAM, LON, LUJ, MAC, MAT, MEL, MUF, NIG, NIC, NIM, OGO, OLB, ORN, RIG, ROL, RUF, RUR, SCH, SEN, SEX, SHE, SPM, SPU, TAE, WAL, ZEN
28: ACU, ANN, BIF, BIT, BIV, BOU, CAL, CHA, CHE, CHR, DAG, DEF, DEC, DOR, EXI, FAS, FIL, GAR, GRA, HOL, INF, JAC, LAM, LOE, LON, LUJ, MAC, MAR, MAT, MUF, NIC, NYO, OLB, RIG, RUF, RUS, SCH, SEN, SEX, SHE, SIN, SPM, TAE, WAL
27: ACU, ANN, BIF, BIT, BIV, CAL, CHA, CHE, CHI, DAG, FAS, FIL, GRA, JAC, LOB, LOE, LOL, LON, MAC, MAR, MUF, NDE, NIC, RUF, RUS, SEN, SEX, SHE, SIN, SPI, SPM, SPP, SUP, TAE, THI, UNS, WAL
26: ACU, ARN, BIF, BIV, CHA, DAG, DUB, FIL, GRA, KIY, LOE, LOL, LON, MAG, MUC, NDE, PAP, RUS, SEN, SHE, SPI, SPM, SPP, THI, UNC, UNS
25: ARN, BAU, BIF, BIV, CHA, DAG, DUB, FIL, LOL, LON, MAG, SHE, UNS
24: ARN, BIV, FIL
A very marked maximum occurs at 29-30 scales. 59 different nominal species may
develop 30 scales. The Fundulopanchax species group is concentrated at values
for high scale counts, except for the small ARN-FIL group that reaches the minimum
values of this character. The variation for nominal Epiplatys is smaller ranging
from 25 to 31 (32) scales. Statistics for this character are given in the section
on crossings for species of which many individuals have been to my disposal.
11) Scales round the body in front of ventrals
Boulenger counted scales round the body in front of the ventrals and so did most
zoologists of his time. Other zoologists counted scales in transverse series,
e.g. from the first dorsal fin ray to the first anal fin ray. I have not been
able to convert (some of these) counts into the system used by Boulenger. In
Boulenger's system I found a variation from 16 to 34 scales. In other systems
the group variation was 6 to 12 scales. Species described after Boulenger's
system are heaping near the variation of 20 to 22 scales. 46 species might develop
20 such scales and 52 species develop 22 scales. I have not prepares such counts
of scales around the body myself and I have to base my idea on the specific
variation on information in literature:
RUR: 24-30 scales = 7
SPL: 28-34 scales = 7
BIV: 20-24 scales = 5
CAM: 20-24 scales = 5
GAR: 22-26 scales = 5
WAL: 20-24 scales = 5
The species described in accordance with Boulenger are distributed like this:
34: SRE, SPL
33: SRE, SPL
32: GUS, SRE, SPL
31: GUS, SRE, SPL
30: BEA, COE, FAL, GUS, MEI, RUR, SPL
29: COE, FAL, GUS, RUR, SPL
28: COE, FAL, GUI, RUR, SPL
27: GUI, RUR
26: BAT, BRU, GAR, GUI, NII, RUR, SPU
25: BAT, BRU, CHR, GAR, RUR, SPU
24: BAT, BEL, BIT, BIV, BRU, CAM, CAR, CHR, CON, ELB, GAM, GAR, HOL, JAU, KIY, LAB, MIC, MUC, OGO, RUR, RUS, SCH, SPU, TES, WAL, VEX, ZIM
19: DAG, MAC, MAR
18: ANS, BAU, BIF, DUB, MAC, MAR, SPM
17: BIF
16: BIF
A specific variation of 6 scales will give 789 separations. If this character
(scales round the body in front of ventrals) was known for all nominal species,
indeed the number of separations would increase considerably.
For various nominal species these counts of scale rows were published:
12: DEC
11: DEC, SJO
10: RUF
09: RUF
08: MAT, MEL
07: MEL, NDE
06: MAG, MEL
A specific variation of 6/2 = 3 scales will give 9 separations and the total number
of separations produced by this character will be 789+9 = 798.
The study of the eleven characters of Boulenger's "standard description" gave these results:
1) SL/max depth of body 711 separations (10.2%)
2) SL/length of head 280 separations (4.0%)
3) eye/snout few separations
4) head/eye 209 separations (3.0%)
5) interorbital width/eye 151 separations (2.2%)
6) dorsal fin count 1798 separations (25.7%)
7) anal fin count 497 separations (7.1%)
8) D/A ratio 2963 separations (42.4%)
9) caudal peduncle ratio 1617 separations (23.1%)
10) scales long 1366 separations (19.5%)
11) scales trans 798 separations (11.4%)
10390 149%
If about 7000 of these 10390 separations (one species from another) all were
different then each nominal species would be sufficiently (?) separated from
all other nominal species by at least one morphological character. Much less
than 7000 different types of separations were harvested from this analysis, as
some form (RUR, ARN, GUS, PET, etc) were separated from most nominal species
by eight characters -more or less- whereas other forms (SCH, INF, TES, PAS, etc. etc.)
could not be separated from very many nominal species by a single character.
When this analysis was prepared some years ago, I prepared an analysis of the
10648 different separations that I had at that time (the "scales long" gave
1744 separations at that time because I calculated the specific variation to
be 5 scales only). This analysis gave the following result: the figure given
for each species or group of species indicates the number of nominal species
from which that species (or group of species) could not be separated:
00: RUR
01: ARN
04: GUS, PET
05: FIL, GUI, SPL
06: COE, FAL, GAM
07: SRE, SJO
08: BEA, BIV, FAS
10: GUL, KIY
11: GRA, LAM, THI
12: CAL, WAL
13: ZIM
14: MEI
15: BAT
18: NIG, LOE, GAR
19: GER, MAG, UNS
21: BOU
22: AUS, ORN, RIG, RUS
23: LIB
24: PAP
25: CAB, DUB, ROL
26: BIT, SEN
27: DOR, SHE
29: LAB, NII, SIN, SPU
30: BEL, CAM, MUC, SEX
31: CIN
32: MUF
34: BAU, BIF, TAE
35: LOL, SUP
36: SPP
37: BRU, CHR
38: DEC, MAC
39: LON, NIM
40: JAC, MEL
41: ACU, OLB
42: ESC, LUJ, SPI, ZEN
43: AHL, CHA, LON, NIC
44: MAR
45: ANS
48: DEF, ELE, MIC
49: LOU
50: ANN, NYO
52: CAS, ELB, HOL
53: POL
54: FER
56: MAE
57: NOR, OBS
59: COG
60: CAR, CHE, CHI, JAU, UNC
61: OGO
62: MAT, PRE
63: LOB, NDE, STR
64: BUA
66: EXI
67: RUF, SPM
68: VEX
69: FLV
72: PAS
74: TES
79: INF
80: SCH
This means that TES cannot be separated from 74 different nominal species by one
single of the eleven morphological characters studied above. Only RUR (Nothobranchius)
can be separated from all nominal species at least by one character. There are
three major reasons why a certain nominal species cannot be separated from other
nominal species by morphological characters:
1) All characters for this particular species group near the center of variation
for the group variation for these characters. This is the "average" species (for example TES)
b) The description for that particular species has been based on a single individual
or on a few individuals only. For this reason the specific variation of the characters
is low (for example TES)
c) The description does not correspond to "Boulenger's standard" description and
the data of the description cannot be compared with data for species described
after Boulenger's system. Or the description lacks important data (for example RUF).
Boulenger's "standard description" contains data which are not suited for a
statistical analysis. These data however can be used for certain separations.
Position of the dorsal fin
Most descriptions publish data for the position of the dorsal fin. This
character is related to the "D/A ratio" (dorsal fin/anal fin ratio = no. 8) and
in some way also to the "number of dorsal fin rays". This character however may
be calculated in different ways that makes comparisons difficult or even impossible.
Boulenger, Pellegrin, Ahl and others used to express this character in this way:
first the distance between the anterior-most dorsal fin ray and the root of the
caudal fin is taken as a unit of measurement. Then the "position of the dorsal
fin" is published as the "number of times" that this unit of measurement reaches
from the first dorsal fin ray to some point of the anterior part of the fish.
This point of measurement may be the end of the snout, the anterior, central or
posterior part of the eye, the end of the head or the root of the pectoral fin.
Such a system is suited for identifications, but not for comparison and statistics
as the various points of measurements of the head vary in individuals in relation
to the standard length.
Poll uses a somewhat different system. He uses the distance between the
anterior-most dorsal fin ray and the root of the caudal fin as a unit of
measurement as in Boulenger's system. Poll however fixes a certain point of
measurement on the head (the end of the head) and for this reason his figures
for this character normally are not whole numbers but a fraction. As the length
of the head varies, these data cannot easily be converted into measurements that
use the standard length as unit.
Lambert uses the same system as Poll. Lambert's fixed point of the head however
is not the end of the head but the end of the snout. For this reason his data
are easily converted into data which use the standard length as a unit. Also Ahl
used this system for his description of ROL, whereas for other species he used
Boulenger's system.
Fowler used a different system. He said that the first dorsal fin ray was situated
above some fraction of the standard length. His data are easily converted into
percent of SL, measured from the end of the snout.
I use to project the root of the anterior-most dorsal fin ray -along scale rows-
on the central line through the median body side and to express the position of
that dorsal fin ray in percents of the standard length measured from the end of
the snout. For these measurements close-up photos of live or preserved individuals
are used. In order to convert the data given by Boulenger, Poll etc. into percents
of SL, calculations have to be used. The following formulae can be used:
R: is the number of times (whole number or fraction) that the distance from the
first dorsal fin ray to the root of the caudal fin reaches into the distance from
the first dorsal ray to "the point of measurement on the anterior part of the fish".
Normally R = 1 or 2 or 3.
b: is the standard length of the body divided by the length of the head.
c: is the length of the head divided by the diameter of the eye.
d: is the diameter of the eye divided by the length of the snout.
%SL = 1/R+1 . (100.R) for "end of snout"
%SL = 1/R+1 . (100.R + 100/b.c.d) - "anterior border of eye"
%SL = 1/R+1 . (100.R + 100/b.c.d + 50/b.c) for "center of eye"
%SL = 1/R+1 . (100.R + 100/b.c.d + 100/b.c) for "posterior border of eye"
%SL = 1/R+1 . (100.R + 100/b) for "end of head"
When the "point of measurement" is the root of the pectoral fin, it is impossible
to calculate the position of the first dorsal fin ray, as the position of the pectoral
fin is not given in descriptions.
"b", "c" and "d" are not constant figures as these characters vary in descriptions.
For this reason mean values were calculated, as only the extremes were published.
Also R varies in Poll's system.
I admit that such calculations are complicated, but I found no other way to evaluate
the data of descriptions, but to calculate in accordance to the formula. I had these
results:
84%: DAG
83%: DAG, SHE
82%: DUB, SHE
81%: DUB
80%: DUB
79%: CHE, DUB, NIM
78%: NIM, ORN
77%: ACU, BIF, CHI, LON, MUF, NIC, SEN, TAE, ZEN
76%: ACU, BAU, JAC, MAC, MUF, SAN
75%: JAC, JAU, MAT, SUP
73%: BOU, NYO, SPI
72%: ANN, FAS, MAR, NIC, NOR, OLB
71%: AHL, ANS, CON, DEF, EXI, GRA, LOB, OBS, PET, SIN, STR, VEX
70%: DOR, ELE, MAE, PAS, PET, POL, UNC
69%: AUS, CAL, CAM, CAR, CHR, COG, DEC, FLV, LON, LOU, LUJ, MEI, MIC, PRE, STR
67%: BRU, GAR
66%: BRU, BUA, CAB, CAS, DOR, ELB, GAR, MEL, ROL
65%: BEA, BRU, GAR, GUL, HOL, MUC, NII, ROL, SPP, SPU, UNS
64%: BIT, FAL, GAR, GUL, HOL, MUC, ROL, SPP, SPU
63%: BIT, FAL, GAR, GUL, HOL, SPU
62%: GUL
56%: BAT, BIV, GER, LOE, PAP, RIG
55%: BIF, BIV, RIG
54%: ARN, BIV, FIL, RIG, SPL
53%: BIV, CHA, FIL
52%: BIV, FIL
51%: BIV, FIL
50%: BIV, FIL
The distribution of the nominal species is not even within the range of variation
for the whole group. The reason for this grouping may reflect certain taxonomic
units or that the different systems used to publish this character are not sufficiently
exact and favor certain figures. From my close-up photos up to spring 1964 I
had these data:
79%: SEN
78%: LON, SEN
77%: LON, SEN, SEX
76%: BIF, DAG, GRA, LON, SEN, SEX
75%: BIF, CHE, DAG, FAS, GRA, LON, MAC, SEN, SEX, SHE
74%: BIF, DAG, FAS, LON, SEN, SEX, SHE
73%: BIF, FAS, LAM, OLB, SEN, SEX, SHE
72%: BIF, CHR, FAS, LAM, OLB, SEX, SHE
71%: BIF, CHR, FAS, LAM, SEX, SHE
70%: BIF, CAL, CHR, FAS, LAM, SEX, SHE
69%: CAL, FAS, SEX, SHE
68%: AUS, CAL, COG, FAS, ROL, SEX, SHE
67%: CAL, COG, FAS, ROL
66%: COE, COG, LAB, NIG, ROL
65%: COE, COG, DUB, LAB, NIG, ROL
64%: BIV, CIN, COE, LAB, NIG, ROL, STR
63%: BIV, CIN, COE, NDI, NIG, ROL, STR
62%: BIV, CAB, CIN, COE, NDI, NIG, ROL, STR
61%: BIV, CAB, CIN, COE, NDI, NIG, ROL
60%: BIV, CIN, COE, GUL, NDI
59%: BIV, COE, FIL, GUL
58%: ARN, BIV, COE, FIL, GUL, SJO
57%: ARN, BIV, COE, FIL, SJO
56%: ARN, FIL, SJO
55%: ARN, FIL, SJO
54%: ARN, FIL, SJO
53%: ARN, SJO
Also this distribution of the nominal species shows some maxima. However,
different taxonomic groups grade one into the other. DUB (65%) is separated
from the main lot of Epiplatys (67-79%) which grades into the Aphyosemion
subgenus (62-72%). The true Fundulopanchax exceeds between 53 and 66%, whereas
the Callopanchax range from 53 to 68%.
The distribution of nominal species as calculated from descriptions had no species
corresponding to the range 57-61% of standard length. The distribution of species
according to my own measurements does not show any such extreme minimum at these
figures. The reason for the uneven distribution from 57 to 61% SL probably is
caused by the fact that the distance between the end of the head and the posterior
border of the eye is rather large in most species and the individual variation
of the length of the head is not able to "compensate" for this. The specific
variation of this character probably will be 8 to 10 units. As the group variation
is 27units (32 units according to descriptions) rather many "separations" will
be possible if this character is used in systematics of West African Rivulins.
However, as I said before, this character is not independent of two other
characters (D/A and D).
The corresponding character for the anterior-most anal fin ray normally is not
given in descriptions. I measured this character on my close-up photos and found
a group variation for the species at hand to be from 54 to 67% of the standard
length (SL). The specific variation was 7 or 8 units and for this reason not
very many separations could be had from this particular character. Also most
forms group within the range from 58 to 60% SL.
Length and shape of the caudal fin
Most descriptions publish data concerning the length of the caudal fin. However,
normally these data are not very exact (and probably normally they can not be
exact, as these fin rays easily break) as it is said that this fin is (much)
longer or shorter than the head, or equal to the head. As the length of the
head is rather variable, these data cannot be used for comparison without calculations
that will make the results even more inexact.
As my photos show large adults with unbroken fins, I have been able to make more
exact measurements of the length of this fin. These measurements show that in
Epiplatys (and Aplocheilus) individuals normally develop (much) longer caudal
fin rays (central rays) than in Aphyosemion and Nothobranchius. For these measurements
females are suited as in some species the male develops very long rays in this fin.
On males and females I had these measurements in "% of SL" (maximum values for
this character).
Central rays:
44%: BIV (males)
43%: BIF, SEX
42%: unidentified Epiplatys of the GRA-MAC group
40%: LON
39%: SHE
38%: CHE, COE
37%: SEN
36%: DAG, GRA
34%: FAS
33%: OLB
32%: DUB, MAC +
31%: FIL
30%: GUL
29%: AUS, COG
28%: CAL, LAM
27%: ARN, NIG
26%: NDI, ROL, SJO
25%: CAB, CHR
24%: CIN, STR
23%: LAB
BIV and COE develop very long central rays in males (in BIV only in some strains).
If the data published in descriptions are used we have this distribution
(figures probably are not very exact). Also in this character DUB comes in
between Epiplatys and Aphyosemion.
42%: BAU
36%: DEF
33%: ANS, BOU, BRU, CHI, FAS, GRA, LON, MAT, ZEN
32%: LAM
30%: BIF, DUB, EXI, MAR, MUF, NII, NIC, OLB
29%: BIV, CHE, CHR, DAG, DEC, JAC, LOB, LOL, LUJ, MAC, NOR, PET, ROL, SEN, SHE
28%: BEA
27%: BEL, CAS, DOR, FER, NYO, OBS, UNC
26%: CON, MAE, NIM, ORN, SAN, THI
25%: CAM, CAR, CHA, ESC, JAU, LIB, MIC, PAS, PRE, SUP
24%: BUA, CAB, GUL
18%: MEI
The values for BRU, ROL and CHR probably are too large. The value for CHA is too small.
Also the shape of the caudal fin (in males) is published in most descriptions.
Within West African Rivulins the shape of this fin in females divides the whole
lot of nominal species in two or three groups. In Epiplatys (and Aplocheilus),
in both sexes, the central rays produce a short lobe that is very distinct in
all species which I have seen alive, except for DUB in which the produced central
rays do not develop the distinct lobe. Also this character develops less in a
pronounced way in the group Fundulopanchax (relatives of COE), but not in Callopanchax,
Nothobranchius and Aphyosemion Aphyosemion. This particular "lobe", formed by
the produced central rays in some species, very rarely is mentioned in descriptions.
In the male of some nominal Aphyosemion and Epiplatys some of the rays in the
lower part of the caudal fin produce, forming a "sword" or "streamer". This
development is rare in Epiplatys and in species I have seen, only DAG, CHA, SHE,
SEX and CHE developed this character. In Aphyosemion also the upper rays produce
normally or (STR) only these rays produce in males. "Streamers" apparently do
not occur in the Callopanchax group of Aphyosemion (SJO, GUI, ROL, LIB, CAB,
MAE, MEL, PET etc.), whereas this character is very common in the Fundulopanchax
group of this genus, however in forms which grade between Fundulopanchax and
Aphyosemion Aphyosemion (NIG, GAR, NDI, CIN etc.) the streamers are shorter or
almost absent. In the subgenus Aphyosemion this character is highly variable,
as the caudal fin is rounded in some males, truncate in other species and provided
with long streamers in still other males.
Central rays of caudal fin produce (forming a distinct lobe?):
ACU, ANN, BIF, CHE, DAG, DEC, FAS, GRA, LON, MAC, MIC, MUF, NIC, NIM, ORN, PAS,
SEN, SEX, SHE, TES, according to descriptions.
The caudal fin is "pointed" in these species:
ANS, BAU, CAL, CHI, DEF, FLV, LOE, MAR, MAT, MEL, NDE, NIM, NOR, NYO, OLB, RIG,
SUP, UNC, according to descriptions.
The caudal fin is "subacuminate" in these species:
DAB, DUB, FER, SAN, according to descriptions.
The caudal fin is "rounded-pointed" in these species:
BEA, BEL, CAL, CAM, DOR, ESC, JAU, OBS, PAS, SHE, according to descriptions.
The development of "streamers" in males may differ considerably when males of
different demes are compared. In Stenholt Clausen's....
and bred in my tanks, very long streamers developed in all males of the Ijebu
Ode strain, whereas all males of the Meko strain developed very short prolongations
of these rays or (most males) no prolongations at all. Also in CAL and FIL this
character is very variable in males. For this reason this character probably is
not very useful in systematics.
According to the descriptions the following different shapes "related to streamers"
occur in the nominal species:
Trilobate: AUS, COE, NII, POL, ZIM
Lyre: ARN, BAT, BIV, CAS, ELE, FAL, FIL, GAR, LOE, LUJ, MUC, OGO, RUF, SIN, SPP, SPL
Truncate: GUL, LAB, NIG, SCH, THI
Rounded truncate: BEA, CAB, CIN, GUI, ROL, SPU
Rounded with one streamer (at top of the fin): STR
Indeed these groupings of species according to the shape of the caudal fin is
not very useful in systematics. More details are given in the section dealing
with the crossings.
Position of ventral fins
Most descriptions publish data concerning the position of the ventrals or pelvics.
These data however are not very exact. For 52 species it is said that the ventrals
are situated midway between the root of the caudal fin and the end of the snout.
This information probably is not to be considered as absolute, as my information
indicates that the specific variation of this character ranges about "8 %" of the
SL and that these fins normally are not situated midway between the root of the
caudal fin and the end of the snout, but closer to the latter than to the former.
I found this distribution of species:
52% SL: OLB
51% SL: COE, FAS, OLB, SEN, SEX
50% SL: CIN, COE, FAS, LAM, LON, NIG, OLB, SEN, SEX
49% SL: CIN, COE, FAS, FIL, GUL, LAM, LON, NIG, OLB, SEN, SEX, SHE, SJO
48% SL: ARN, BIF, BIV, CAL, CIN, COE, DAG, FAS, FIL, GUL, LAB, LAM, LON, NDI, NIG, OLB, ROL, SEN, SEX, SHE, SJO, STR
47% SL: ARN, BIF, BIV, CAL, CHE, CIN, COE, DAG, FAS, FIL, GRA, GUL, LAB, LAM, LON, NDI, NIG, ROL, SEN, SEX, SHE, SJO, STR
46% SL: ARN, AUS, BIF, BIV, CAL, COE, COG, DAG, FAS, FIL, GRA, LAB, LAM, MAC, NDI, NIG, ROL, SEN, SEX, SHE, SJO, STR
45% SL: ARN, BIF, BIV, CAL, CHR, COE, COG, FAS, FIL, GRA, LAB, NDI, NIG, ROL, SEX
44% SL: ARN, BIF, BIV, CAB, CAL, CHR, DUB, FAS, GRA, NIG, SHE
43% SL: BIF, BIV, CAB, CHE
42% SL: BIF, BIV, CAB
41% SL: CAB
40% SL: CAB
For this rather limited material I found these specific variations:
FAS: 8
BIF: 7
BIV: 7
NIG: 7
SEX: 7
SHE: 7
SEN: 6
ARN: 5
CAB: 5
CAL: 5
FIL: 5
LAM: 5
OLB: 5
As the group variation is 13 units only it is likely that not very many separations
can be obtained from this character. I found no coherence between this character
and the length of the head, whereas some coherence probably exists between the
position of the ventrals and the position of the anterior-most anal fin ray.
Descriptions published this information:
Distance from end of snout to base of ventrals in percents of SL:
<<50%: LOL, SAN
< 50%: BAU, BEL, CAR, CON, JAC, MIC, NYO, ORN, PAS, RIG, SUP, TES, UNS
<=50%: BIV, BOU, CAM, ELE, ESC, MEL, NOR, SIN, TAE
=50%: ANS, ARN, AUS, BAT, BIF, BIT, BRU, BUA, CAB, CAL, CHI, CHR, DEF, DOR, ELB, EXI, FAL, FAS, FER, FLV, GAR, GRA, GUL, GUS, JAU, LIB, LOB, LOE, LON, LUJ, MAC, MAE, MAR, MUC, MUF, NII, NIC, NIM, OBS, OLB, PAP, PET, POL, PRE, ROL, RUS, SCH, SJO, SPP, SPU, STR, THI, UNC, VEX, ZEN, ZIM
>50%: BEA, COG
If this character should be taken into consideration in the systematics of West African
Rivulins the data for this character should be more exact, as the data mentioned
above do not support any differentiation between nominal species.
Length of rays in pectorals, ventrals, dorsal and anal fin
Most descriptions publish information concerning the length of the pectorals and
the ventrals and the longest ray in the dorsal and anal fin. The length of the
pectorals often is given as the relative length compared with the length of the
head and also it is said that this fin reaches (or does not reach) the root of
the ventrals. The length of the ventrals is given in relation to the anterior-most
anal fin ray (reaches this ray or does not reach this ray). I do not think that
the length of the pectoral fin has much importance in the systematics of these fish.
Indeed some rays of this fin produce considerably in some species, but the individual
variation is large. In Fundulopanchax the males often use this fin to guide the
female in pre-mating display and for this reason the lower rays often produce.
Produced pectoral rays as occur in Epilatys. In ANN (Monrovia and Kasewi strains)
the male may develop very long pectoral rays. In a still unidentified relative
of BIF the male may develop extremely long pectoral rays that may reach beyond
the last ray of the anal fin. Such development however is rare and this character
probably only has importance as a supplemental character.
The length of the ventrals in males probably is more important. This fin does
not produce in Aphyosemion and Nothobranchius (except for SPL). Also in Epiplatys
this development is rare. In SEX from Nigerian localities west of the Cross River
drainage males normally develop long ventrals. Apparently males of SEX from
Cameroon and Gabon never develop long ventrals. Produced ventrals also occur in
LON and LAM and in some derivates of FAS. In African Rivulins produced ventral
fin rays occur in males only, whereas in Aplocheilus (LIN and DAY) this character
occurs in both sexes.
Dorsal and anal fin rays may produce in males of Aphyosemion and Epiplatys. As
I have already mentioned for the streamers of the caudal fin, produced dorsal
and anal fin rays often are an individual character of the deme. BIF from the
Niger drainage normally does not develop streamers at the anterior corner of the
anal fin, whereas this character is common in BIF from the Volta drainage and in
Sierra Leone demes. In the common aquarium strain of DAG (the E. dageti monroviae
subspecies) males do not develop a much-pointed anal fin. Stenholt Clausen's strain
1965 of this form, caught at the locality from where the old (1908) aquarium strain
probably originated, indeed develops such streamers in some males. As I already
pointed out for Stenholt Clausen's 1962 strain of BIV from S. Nigeria, large
variation in the development of produced rays of the caudal fin is evident. This
is also true for the posterior rays of the anal and the dorsal fin in this species.
On my own material I measured maximum lengths of produced dorsal and anal fin rays
in males (given in percent of standard length of the body):
| Dorsal | Anal |
| 88%: BIV | 63%: BIV |
| 32%: FIL | 42%: BIF |
| 31%: CAL | 38%: CHR |
| 30%: CHR | 35%: LON |
| 23%: AUS, LON | 30%: SHE |
| 22%: ARN, COE, GUL, NIG, SEX, SHE, STR | 29%: DAG, SEX |
| 21%: BIF, COG, FAS | 28%: OLB |
| 20%: NDI, OLB, ROL | 26%: GUL |
| 19%: CAB, DUB, SJO | 25%: CHE, FIL |
| 18%: DAG, LAB | 23%: ARN, COE, SJO, STR |
| 17%: SEN | 22%: CAL |
| 16%: CHE, CIN, GRA, LAM | 21%: AUS, DUB, FAS, NIG |
| 15%: MAC | 20%: COG |
| 19%: LAM, ROL, SEN |
| 18%: NDI |
| 17%: CIN, LAB |
| 16%: CAB, GRA |
| 15%: MAC |
Further characters of "Boulenger's standard description"
For most species it is said that "the head is flat above", "the mouth is directed
upwards", "the lower jaw is projecting". This information probably has no systematical
importance at all. It is also said that "the preorbital is very narrow", but so
it is in all nominal species (character of this subfamily). Most descriptions also
say that "the lateral line is represented by an interrupted series of pits". Also
this character probably is of no importance in this group of Rivulins. No descriptions
publish any information on the very well developed lateral line system of the head.
It is a pity that rather many descriptions do not publish information concerning the
exact locality from which the types originated, as this "character" probably has
more importance than any other information given in descriptions. About 20% of
the nominal species have been based on aquarium kept individuals of unknown origin
and "West Africa" or "Tropical Africa" is the only information given on the type
locality. "Colors and color patterns" are considered later.
Conclusion
This formal study of information given in descriptions of West African Rivulins
has made quite clear to me that the principles on which most nominal species have
been based are not sufficient to support the maintenance of rather many of the
nominal species. I have based this study on "typological thinking" in the sense
of E. Mayr (Evolution and Animal Species, 1963) and I have taken it for granted
that "species are characterized by their differences from other species".
These findings may be used in one of two ways. One may make a lot of nominal
species synonyms of previously described (also ill defined) species or one may
try to disclose further reliable characters to support the maintenance of at
least some of the nominal species which can not be maintained on the criteria
so far used. From the point of view of an engineer, E. Mayr's definition of the
word "species" is just what we want. Mayr says: "groups of actually or potentially
interbreeding natural populations which are reproductively isolated from other such
groups". Not a single word is said about "differences" in morphology in this
definition of the "unit": the species. As crossings may give away certain information
about "reproductive isolation from other forms" I should like to inform you on
the results of the crossings which I studied since 1957.