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Scheel's Letters: West African Rivulins: Epiplatys sheljuzhkoi Poll 1953
courtesy of
ARK - Arizona Rivulin Keepers
The Scheel Letters, No. 50
West African Rivulins: Epiplatys sheljuzhkoi Poll 1953; Draft (Aquarium Journal)
In the previous article on Epiplatys dageti we tried to encircle the West African
Rivulins that could be considered to be identical with Haplochilus chaperi as
described by Sauvage in 1882. We attempted to prove that Epiplatys dageti Poll
1953 and in particular the variant known as Epiplatys "chaperi" had to be acquitted
of being identical with Sauvage's species. We also expressed some suspicion that
Epiplatys sheljuzhkoi Poll 1953 maybe could be the one that we were searching for.
There are reasons, however, also to acquit E. sheljuzhkoi, at least provisionally.
The best defense that E. sheljuzkhoi is able to lay out is its number of dorsal
rays. Whereas Sauvage's species, according to the description, has D 7/A 15,
E. sheljukhoi has D 11/ A 16, according to the description, and D 11-12/A 15-18,
according to our measurements. This means that for the present we are not able
to identify any Rivulin known from southern Ivory Coast and Ghana with Sauvage's
species. The type material first should be inspected.
Even though E. sheljuzkhoi was not described as a zoological species until 1953,
preserved individuals belonging to this species had been present in the collections
of museums. The British Museum in London, for instance, possesses a big collection
of specimens collected at various localities in Ghana. We have examined all these
individuals and found that they all belong to Poll's species and not to Epiplatys
sexfasciatus Gill as was hitherto supposed. E. sexfasciatus, from all appearances,
does not extend its distribution to the west of the rainforests bordering the
frontier between Dahomey and Nigeria. It was unable to pass through the dry landscape
which extends southwards from the northern savannas of West Africa and which reaches
the coast in Dahomey and Togo.
The similarity of these two Epiplatys is very pronounced so we had to prepare
crossings to clear up the affinities. The hybrids were more or less viable, but
as they also were functionally sterile, we might consider E. sheljuzhkoi and
E. sexfasciatus as two distinct species.
It is, however, very easy to distinguish between these species when microscopical
examination is directed towards the side line pores of the head. This method
will soon be published in a zoological paper by Stenholt Clausen, and, as it is
not suited for aquarist use, we will try to define the species from other points
of view.
Towards the east, E. sheljuzhkoi probably extends its range as far as the forests,
that is, to the mountains at the frontier between Togo and Ghana. We recently
had preserved material from that part of Ghana. To the north, it seems as if the
extension follows the border of the forest. In the central part of Ivory Coast,
the forest line steeply turns off towards the south because a wedge of savanna
pushes forward deep into the forest. Centered in the northern part of this wedge,
the city of Bouake is situated. From this locality, in 1960, Arnoult described
his Epiplatys spillmanni which at some localities lived in swamps with acidic
and very brown water. On the basis of the description we are unable to separate
this species from neither Epiplatys sheljuzhkoi Poll nor from Epiplatys dageti
Poll. We consider it to be most likely that this species represents one of the
many variations inside E. sheljuzhkoi.
The extension of E. sheljuzhkoi towards the west is not known at present. Reliable
reports west of Abidjan do not exist. There are however several reports of the
occurrrence of both E. sexfasciatus and E. ansorgei in western Ivory Coast and
in the forest more westwards. As we do not believe that neither E. sexfasciatus
nor E. ansorgei exist west of Dahomey, these reports may cover other Epiplatys or
Aphyosemion, known to exist in the western part of the Guinean rainforest. The
preserved material on which these reports have been based have to be examined
first. At present, we are only able to control one report. In 1936, E. Roloff
from Karlsruhe collected specimens of a Rivulin at Kissy, near Freetown in Sierra
Leone. These specimens were described as Epiplatys sexfasciatus leonensis by Ahl
in 1937. During his stay in Sierra Leone in 1962 Roloff again collected specimens
of this form near the type locality and kindly sent us live and preserved material.
Ahl's subspecies was soon found to be identical with the true Epiplatys fasciolatus
Guenther.
The material on which Poll based his description of Epiplatys sheljuzhkoi in 1953
was collected by Dr. L. Sheljuzhko. This was the same expedition where he also
collected the material on which the description of E. dageti was based. The
collector wrote that, in his collection area, E. sheljuzhkoi was abundant and
was discovered in most localities. From Abidjan, which is the type locality,
and up to a distance of approximately 50 miles north of this city, the species
was found to live under various ecological conditions. The live material, when
distributed in Germany first was named E. macrostigma. Roloff however sent individuals
to Dr. M. Poll who in 1953 described the form as E. sheljuzhkoi. For our research
on this species Dr. Poll kindly lend us preserved specimens.
Our material of live specimens originated from 4 populations from SW Ghana collected
by H.S. Clausen in 1962 and one population from Central Ghana collected by Ulf Hannerz
in 1963. The westernmost population derived from a locality near Tikawbo near the
coast. The next population was found approximately midway between Cape Three Points
and Half Assinie at a place called Aiyenasi, approximately 4 miles from the coast.
One population lived in the rainforest (80-85 inches of rain) on tertiary sediments,
in clear brown water with electrical conductivity of 23 rec. megohms (very much like
distilled water) with soap hardness of only 0.5 German degrees and a pH approximately
at 5. The water of the second population measured 27 reciprocal megohms. Both
localities are situated within a part of the SW Ghana rainforest which most probably
has supported tropical rainforest during the last one million years. The soil of
this area is highly leaked and belongs to the type of soil named oxysols. The surface
layer of this soil is very acidic and has a pH of 4.0-4.5, however on the tertiary
sediments the pH of 3.5-4.0 is more common. The pH increases when one analyses the
deeper layer of soil and reaches approximately pH 5.2 at a depth of six feet.
Together with the specimens of E. sheljuzhkoi, also specimens of Afronandus sheljuzhkoi
and a Micropanchax were collected. These two populations of Epiplatys sheljuzhkoi
apparently are very close to Poll's types in every visible respect.
Further towards the east, individuals from two populations were collected around
Angona, some 10 miles north of Cape Three Points. These specimens are very much
like the type material from Abidjan when the counts and measurements are compared,
but they differ markedly in coloration and in color patterns. Both populations
were taken in rainforest (approximately 75 inches of rain per year), on parent
rock covered by a soil belonging to the oxysol-ochrsol type that is less acidic
and less leached than the pure oxysol. The water measured 80-100 rec. megohms,
soap hardness was 1.5 German degrees and the pH approximately 6.1. Epiplatys
sheljuzhkoi lived in brooks and small swamps at these localities. Here and there
precipitations of iron at the bottom could be seen.
Ulf collected his live material near Kumasi approximately 100 miles from the coast
and inside the Ashanti forests. This forest is called the moist semi-deciduous
forest type and stands on a soil of the ochrosol type. This soil has a pH of 5.5-7.0
and at the surface but at a depth of 6 feet the pH measures approximately 5.2,
approaching the same pH which also was measured at that depth inside oxysols.
The annual rainfall is approximately 60 inches in this area and the length of the
dry season is greater. This area probably is not able to support a tropical rainforest
during the arid periods which are known to occur in this part of Africa in connection
with the glacial and interglacial periods of Europe. The Kumasi population differs
in coloration and in color patterns from the populations previously mentioned.
A fourth form we only know from color and black/white photos sent to us by Dr. W. Foersch
in 1960. This strain was imported into Germany in 1960 together with Epiplatys
bifasciatus and Fundulosoma walkeri and derived from Ghana. A few notes on this
importation were published in the DATZ 1960 by Meinken. As we do not know the
locality of this form here we call it "1960" strain.
These six populations of E. sheljzhkoi divide into four variations of the E. sheljuzhkoi
phenotype that may or may not represent geographical units or subspecies. The differences
between the four strains however are only found in the coloration and in the pattern
of dark crossbars on body sides.
Juveniles of E. sheljuhkoi all develop black crossbars on body sides. The number
of such bars differs somewhat from one population to another but it is rather
constant in a certain population, apart from the Kumasi population which is variable
in this respect. The females retain these dark crossbars also after maturing. When
frightened or sometimes also during spawnings the bars may disappear more or less.
The males normally loose their crossbars after maturing. This feature is often
seen within Epiplatys more or less markedly, but in E. sheljuzhkoi we find perhaps
the most complete loss of male's crossbars. No wonder that Poll, in the description
of this species, wrote that the male had no dark crossbars at all. If two ripe
males are placed together in a tank we soon will realize that the crossbars still
are present. These males very soon will fight each other and during the fight
the crossbars are very conspicuous indeed and just as marked as those of the females.
During spawning the male does not show its crossbars at all. Females as usual in
this genus tend to double their black crossbars. The tendency to double crossbars
is very much as within E. sexfasciatus and far below that of some populations of
E. dageti.
A dark longitudinal band, from the gill covers to the root of the caudal fin, may
develop on both sexes, in particular if the individual is suddenly taken from one
tank and placed into another. Such bands may occur also on spawning females that
however normally do not loose their crossbars when the longitudinal band is visible.
It seems as if the common system of spawning signals (crossbars contra longitudinal
band) is less developed within this species if we compare it with such species as
E. senegalensis and E. longiventralis.
Individuals of E. sexfasciatus may show what may be called a "reversed system of
crossbars". When colored like this, the individual shows light crossbars on a dark
background of body colors. This color system is linked to the night coloring and
appears when one suddenly puts light on a dark tank containing these fishes. After
a few minutes this color pattern fades away and may reverse into the normal system
of dark crossbars on a light background of body colors. This odd color pattern
also has been seen on a single individual of E. sheljuzhkoi. The dark ground color
of this male reached the gill covers and covered the hindmost part of this.
More dark pigmentations are seen on the throat and it is likely that these patterns
represent "signals of approach". Very small juveniles of this species develop a
narrow red line just behind the lower lip and following the line of small side-line
pores. This red line is seen on all juvenile individuals of West African Rivulins
so far inspected. Behind this red line very often red pigments are seen on the
throat back to a line between the corners of the mouth. This pigmentation tends
to concentrate to a narrow red line from one corner of the mouth to the other.
On juvenile E. sheljuzhkoi these red pigmentations however are weakly developed.
During maturing the red pigmentations are replaced or covered by black pigments.
Primarily the dark pigmentation takes place on the area between the lower lip and
the line between the corners of the mouth. On males, however, the area more backwards
develops melanophores covering the whole throat and lower parts of the gill covers.
The dark pigmentation of the anterior part of the throat often tends to split up
into two dark bars across the throat, one behind the lower lip, the other one between
the corners of the mouth. When the individual is not activated, there is no conspicuous
difference between the throat pattern of the two sexes. During fight and spawning
however the male changes its throat pattern by the way that the whole throat back
to the posterior edge of the gill covers develops a uniform bluish black color, just
the same "pattern" as mentioned for Aphyosemion cinnamomeum and which also is used
by male Epiplatys senegalensis, E. fasciolatus and Aphyosemion australe. During
spawning the female to some extend transforms its throat pattern by the way that
the whole area in front of the line between the corners of the mouth develops a
more or less uniform very dark color, whereas the posterior part of the throat
remains nearly uniformly white. Such temporary throat pattern signals seem to be
very common among Old World Rivulins. Beside the species mentioned above, Aphyosemion
roloffi and Aplocheilus dayi also use throat signals of this type. Fundamentally
such signal patterns differ markedly from those developed by species like Epiplatys
dageti, Aphyosemion nigerianum, etc. The systems of these species are permanent,
they do not change their nature during fights and spawnings, and they permanently
provide a conspicuous difference between the two sexes when seen from ahead.
We consider such color patterns not only to be of a certain interest to the aquarist,
but also to possess a certain systematic value because probably several genes of
inheritability are responsible for the development and the deciphering of such signals.
Mature specimens of E. sheljuzhkoi do not show any red pigmentation on the throat,
however under the microscope one may or may not find traces of red pigments.
The dark crossbars on the body side seem to belong to just the same system which we
find in Epiplatys sexfasciatus. The latter develop six dark crossbars normally, at
least on juveniles and on young males. There are also one or two such bars on the
head, but these are not considered here. The anterior bar develops just behind
the pectorals and for this reason we use to call it the "P bar". The next bar
sits over the root of the ventrals (more or less replaced) and is called the "V bar".
The other four bars normally develop at equal intervals on the area between the
first ray of the anal fin and the root of the caudal fin. These we call the "A bar".
The P bar is present on the type female, on all individuals of the Tikawbo-Aiyenasi
populations and is not present (normally) on individuals from the Abra-Angona, the
Kumasi and the "1960" populations. However, among approximately 100 individuals of
the Abra-Angona strain we have seen one individual (a male) that developed such
bars on one side only. Among the offspring of this male no individual had such
bars however. Also among individuals from the Kumasi population very rarely the
P bar may develop on one side of the body. The V bar was present on one of the
females that Poll lent us. It is normally present on individuals from the Kumasi
population. In the first generations and the imported individuals from the
Tikawbo-Aiyenasi populations not a single individual developed this bar, however
in one strain from the offspring several individuals developed this bar. The
Abra-Angona (and "1960") populations normally have neither a P nor a V bar on the
body sides. Among the numerous offspring from the populations first mentioned
there was a single male which developed one V bar. This male belongs to the offspring
of the "single P bar male".
As we mentioned before, the females from the Kumasi strain tend to double their dark
crossbars. The extra bars normally are A bars and they normally are not permanent
but come and go according to the temper of the fish. Doubling of the crossbars rarely
occurs on the females of the other populations. It does not seem that the doubling
of crossbars has any meaning as signals exchanged between individuals of this species.
Dark pigments may develop along the free edges of males' fins. These pigmentations
normally are not at all conspicuous as on many strains of E. sexfasciatus and in
particular on male E. dageti. The pectorals also may develop a dark edge.
The metallic brilliance of the male differs markedly when different populations
are considered. Males from the Abidjan populations and those from the Tikawbo-Aiyenasi
populations develop a very strong brilliance not only on the whole area of the sides
but also on the unpaired fins. Also the edge of the pectorals develops much brilliance.
The color is bluish green when the fish is seen in incident light from above.
The "yellow" males of the Abra-Angona populations also may develop a strong brilliance
that is lemon, probably caused by the strong development of yellow pigments within
this strain. Males of the Kumasi, the "1960" and the "red" males of the Abra-Angona
populations develop a very reduced brilliance probably because the various red and
black pigments dominate and transform the color of the body and the fins into a
red, or brown of very dark tinge. The Kumasi males have also an odd violet tinge
on body and fins. The "1960" male has a weak brilliance on body sides whereas the
fins are colored like the Abidjan males.
The reason why the 1952-53 aquarium strain imported from Abidjan was named
Epiplatys macrostigma seems to be based mostly on the development of red dots
along male's body sides. The development of these red dots differs markedly from
one population to another. The Abidjan, Tikawbo and Aiyenasi populations develop
big rather rounded red dots on male's body sides. Towards the back the dots however
tend to form red edges of the scales. The Abra-Angona males develop red dots that
are less conspicuous and the tendency to form red scale edges on the back appears
to be stronger. The red dots on males from Kumasi and the "1960" male are rather
big and conspicuous, however the tendency for the development of red scale edges
is much stronger than inside the other populations. The red dots are vertically
oblong and the red reticulated pattern on the back is more perfect. These strains
take in a position somewhat in between the Epiplatys that develop perfectly rounded
red dots on body sides and those that develop a complete reticulated pattern produced
by red scale edges. Such variations, but by far less developed, also exist in the
populations of E. sexfasciatus from Nigeria.
The very conspicuous differences of the colors of the fins of males from different
populations probably depend on the interaction of brilliance versus pigmentation.
The strong brilliance of the Tikawbo-Aiyenasi males seems to be linked with the
marked concentration of the pigment colors. On the body sides these pigments
are concentrated mostly inside the big red dots that may or may not possess a
black edge. In the fins the pigments seem to concentrate as narrow reddish black
lines situated on the membrane between the fin rays. This concentration of pigments
leaves open a large unpigmented area for the development of brilliance. However,
these narrow red lines often break up into lines of red dots in particular in the
dorsal fin (all populations) and inside the upper part of the caudal fin, or more
rarely also in the lower part of this fin (Angona-Abra and "1960"). Only in the
Tikawbo-Aiyenasi (and Abidjan) populations the red lines of the anal fin break up
into red points and mostly only near the fin root and in the most posterior part
of the fin. This breaking up of the red lines produces a marked effect as the
rows of red dots are much more conspicuous than the unbroken red lines. Thus the
pattern of the fins is changed markedly but the basis for this transformation only
seems to be a minor change of the development of red pigments.
The fins of the Abra-Angona males look very yellow, orange or even red. This change
of the fin color is produced by a dispersing of the red (and yellow) pigments out
from the narrow red line centered in between the fin rays. In the anal fin this
dispersion produces an almost uniform red color on red males. In the caudal fin
the dispersion normally is not complete and the fin rays are uncolored. Also in
this case a minor change of the red pigmentations produces a marked effect on the
color of the fins. The same effects are produced on the body sides when the red
(and black) pigments disperse and cover the brilliant areas.
We have used the terms "yellow" and "red" males for males of the Abra-Angona populations.
It seems as if at least some males are able to change their general coloration
from a brilliant lemon yellow into a deep orange red color of the whole body and
the fins. Young males normally are yellow only. Old males may look lemon or deep
orange. We do not know if an orange male may change its color back to lemon. One
nature caught male was orange when imported and it remained unchanged for its whole
life. Orange and yellow males are very handsome aquarium fishes indeed.
The upper edge of the dorsal fin is provided with a brilliant white edge on males
of the Kumasi and "1960" strains. This edge contrasts markedly with the dark body
color of Kumasi males. All strains have more or less developed milky white edges
of the upper part of the caudal fin.
The females have very little metallic brilliance, as only the lower edge of the anal
fin develops some bluish shine. The red dots on the body sides are smaller than on
males and the reticulated pattern of dark scale edges is more marked. The shape
of the body and the fins is seen on photos.
A remarkable feature is the prolongation of some of the lower rays of the caudal
fin that takes on a shape not unlike that of male E. dageti. The development of
this "sword" varies somewhat from one population to another and also in a certain
population. Normally such prolongations do not develop on male E. sexfasciatus,
however now and then very old aquarium kept males may develop a very short sword
indeed.
In order to prove if the variations of natural populations as mentioned above were
linked also to differences in the reproduction we made some crossings. Some of
these crossings only gave very few fry, as we had several difficulties to find a
water type suited for safe development of eggs. All offspring from such crossings
so far gave fertile individuals of both sexes and this indicates that all forms are
very closely related.
Angona male (the one with a single P bar) to Aiyenasi female gave two fry which
both were males. Both had a single P bar, but odd enough this bar developed not
on the same side of the body as that of the father. A normal Angona male however
gave a single fry which also was a male and which did not develop a P bar. These
three mixture males in their coloration represented a compromise between the other
colors and patterns. All had the very characteristic big red dots on the upper
parts of the anal fin (originated from the Aiyenasi population) and a rather weakly
developed overall yellow color on body and fins (Angona population).
The Kumasi female and the Aiyenasi male produced numerous offspring that also were
fertile in both sexes. As the former normally has two V bars and two P bars, whereas
the latter has just the opposite we were interested to see if the offspring would
develop both P and V bars. Many individuals indeed developed this "sexfasciatus like"
pattern either on one side or on both sides of the body. Some individuals developed
neither P nor V bars.
This means that neither the typical pattern of Ayinasi nor that of the typical Kumasi
strain developed. As the Kumasi strain itself is very variable, the results of this
crossing are not easy to survey. In order to try to develop a handsome aquarium
strain, the Angona/Ayinasi mixed male was crossed to the Kumasi female. The offspring
developed a highly variable pattern of crossbars.
As mentioned under E. dageti, the hybrids between this species and the E. sheljuzhkoi
species were not viable. Bruce's strain and the Kumasi strain however gave hatching
of apparently viable fry which however could not be raised, whereas the Monrovia strain
with the Angona strain gave embryos which died before they were fully grown in the eggs.
The fry all died from a blocking up of the blood system. With Aplocheilus lineatus
we only had a single egg, but this developed a blastula, but then the development
stopped and after a few days the egg died. The best result was obtained with Nigerian
Epiplatys sexfasciatus. 26 fertile eggs developed and hatched normally. First hatching
took place after only 10 days and that fry had no yolk left. If we compare Rivulins
living west of the Dahomey gap with those living east of that barrier, the western
species normally have a more rapid development inside their eggs. The male was a
Benin City individual whereas the female belonged to the Aiyenasi strain. 16 juveniles
died during the first weeks in spite of our best care of these hybrids. 10 individuals
were raised to maturity, but only 5 of these were strong fishes that developed sexual
characters. 2 males and 3 females reached a total length of some 50 mm. The two males
differed as one lost its dark crossbars very early in life and never again was seen
so colored, whereas the other male kept its black bars through its whole life. Females
and the barred male all had four A bars, however one female was lacking the two midmost
bars. This particular female also did not develop any black bars in front of the anal
fin. The other females all developed a P bar on both sides. Only the biggest female
and the barred male developed the complete E. sexfasciatus bar system. Females often
developed the black longitudinal band from the gill covers to the root of the caudal
fin. It was impossible to get a single egg from these females and the males gave
sterile eggs in back crosses.
The crossing results indicate that E. sheljuzhkoi is somewhat closer related to
E. sexfasciatus than E. dageti. This idea is supported by the results of the
electrophoresis analysis which say that the E. sheljuzhkoi has the very same spectrum
(6 lines type) as have the E. sexfasciatus and E. longiventralis which seem to represent
a certain group inside the genus Epiplatys. Meinken has supposed (Aquarienfische
in Wort und Bild) that Epiplatys chevalieri and E. sheljuzhkoi are subspecies of
Boulenger's Epiplatys macrostigma. We are not able to support this idea as at present
we consider each of these three species as belonging to its own group of species
inside the genus. At present we are not able to link the "sexfasciatus-longiventralis-sheljuzhkoi
group" to any other group of Epiplatys.
From the aquarist's point of view the Abra-Angona strains of E. sheljuzhkoi are very
handsome fishes and may become popular aquarium fishes if it was not for the behavior
of these fishes. Like all known strains of this species, the individual when matured
is very stagnant. Also the adults rest nearly all day long at the surface of the water.
Towards members of its own and related species it is very brutal and perhaps you will
find it even more brutal than adults of E. sexfasciatus. On the other hand, this
species is a very handy one and seems to live in all types of aquaria usually used
by aquarists. Best breeding results however are obtained in soft, slightly acidic
water loaded with extracts from peat. The eggs measure 1.2-1.35 mm. They are transparent
without any color and have long slimy filaments. The surface of the membrane may or
may not have a reticulated pattern, weakly developed.
If we compare the variation in morphology and color patterns found within populations
of E. sexfasciatus from Nigeria-Northern Cameroon with the variation described here
for a restricted number of populations of E. sheljuzhkoi originating from a rather
restricted area of western Ghana, we certainly find that the variations of color and
color patterns are much greater in the latter than in the former species. It may be
so that these variations are linked to the ecological conditions of the various
populations studied.
However, also other reasons may be found. We have studied the prehistoric development
of climates for this part of Africa in order to discover some explanation for some
differences in genetics discovered among populations of Aphyosemion bivitattum and
A. nigerianum. Also we found it somewhat difficult to understand that the Rivulin
fauna of the rainforests of Ghana apparently was poor in species. This study in
literature indicates that the extension of the western parts of the Guinean rainforest
(west of the Cameroon Mts.) has varied strongly in connection with the changes of
climates that were produced by the glacial and interglacial periods of Europe. The
geological and pedeological research in this part of Africa shows rather convincingly
that during Pleistocene there have been very marked periods of aridity and of higher
rainfall than today. There are however different opinions on the coherence of the
events in Europe and those of this part of Africa. In our opinion the theory that
links the arid periods of this part of Africa to the climax of the glacial seems
to be the best founded. This theory says that the icecap on northern Europe will
displace the climatic zones to a more southernly position and in this way the arid
zones advance towards the Guinean coast. During these arid periods the Guinean
rainforest of this area will be forced against the coast and it is likely that the
forest is subjected to fragmentation. The forest and freswater fishes linked to
this biotope will survive here and there along the coast where favorable conditions
for an increased rainfall exist. Such areas probably are found, in particular,
on the southern and western slopes of the mountains. If this is true, the Rivulins
of these forests are split up into isolated populations for some length of time.
As such isolated relict forests most likely will support only a rather limited number
of individuals inside each population, causal mutations may more easily establish
themselves inside such populations, forcing that population to develop some traits
which are not developed inside other populations. Our many crossing experiments in
African Rivulins indicate that in this group of fish some mechanisms governing the
development of the embryo and the reproduction of the species as a whole are likely
to develop mutations more often than the genes which govern the general morphology
of the species. When the ice retreats from Europe and the climate of that part of
the world becomes warmer, the climatic zones of Western Africa again will move northwards.
The rain will fall again and the relict forests will expand. The isolated populations
of the rainforest Rivulins again will be able to exchange their genes if such an
exchange still is possible. Such exchange seems to be rather difficult or even
quite impossible between different populations of A. bivittatum, A. nigerianum and
between A. arnoldi and A. filamentosum. In the known populations of E. sheljuzhkoi
such exchange however still seems to be possible and also very easy if individuals
from different populations are brought together.
It may be so that more than one population of E. sheljuzhkoi survived as an isolated
unit after the last glacial period of Europe. During postglacial time the isolated
populations reunited and exchanged genes more or less forming different combinations
from which the present populations developed their different color patterns. As we
said before, a rather small part of SW Ghana is covered by a particular type of soil
which indicates that this part of Ghana and also some parts of eastern Ivory Coast
have supported a forest also during the arid periods mentioned above. French botanists
and soil scientists during recent time published detailed maps showing the various
types of soils and forest types and pointed out that in Ivory Coast there is a marked
connection to be found between these two factors. On the soils that represent
the oxysols in this area the number of tree species is much higher than on other
soil types, thus indicating that the oxysols or like soils represent the areas
where relict forests survived during the arid periods. They also show that in
the western part of Ivory Coast and some parts of eastern Liberia there is another
area which probably supported forest during the arid times. Rather limited parts
of the mountainous landscape of eastern Ghana (Togo Hills) are covered by types of
soil that indicate that also in this area some relict forest survived the last
glacial period. Until more populations have been studied we are not able to deal
with the probable history of development in E. sheljuzhkoi.
