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Scheel Letters: Aphyosemion cognatum
Courtesy of
ARK - Arizona Rivulin Keepers
The Scheel Letters, No. 10
Aphyosemion cognatum
This handsome "red" Aphyosemion was found by the Belgian Dubois and imported
by Hartel, Cresden and Griem, Hamburg 1950. Meinken described this fish as a new
species in 1951 using material form the importations. Later, in 1955, Werner from
Muenchen had another importation (another variation, possibly). My stock came from
Griem in 1954, but in 1956 I got a new stock from the USA which now is mixed up into
the "old" stock. Meinken wrote that this fish possibly was closely related to Aphyosemion
striatum and Aphyosemion calliurum, but it may also stand close to the "cameronensis" and "schoutedeni".
Both sexes will grow up to 50 mm, rarely more than 60 mm. The shape of the
body is like "australe", also the fins remind you of "australe" but even as the
caudal fin very often has prolonged upper and lower rays, these never form a "lyretail"
as in "australe". Also the hindmost part of the anal fin is less pointed. The male is
overall reddish on body and on fins. On the body the red color comes from small,
red dots on practically all scales on the sides. In some of the importations the
males did not have so many red dots (easily seen from the various photos in literature),
but in my present stock only very few scales have no red dot. The ground color
also is reddish yellowish. The vertical fins often have an overall reddish to
pure yellow color and lots of red dots. The dorsal, anal and caudal fin have thin
red edges, by far not as marked as in most other Aphyosemion. The common bluish
to greenish brilliance on the sides of the male you only may see on the gill covers.
The female like other females in this genus is plain brownish but she has many dark
brown dots on the scales, just the same regular pattern as we find in the male, and
you easily may take out any female of "cognatum" from a mixed population of Aphyosemion.
Her anal fin often shows a bluish cast.
The species have only been caught near Leopoldville in Belgian Congo.
Werner bought this stock from the Negroes in the village of Kinsuka, near Leopoldville.
They brought him the fishes in bottles, but he did not see the place where it was caught.
The Belgian zoologist and connoisseur of the fish fauna of Belgian Congo, Dr. M. Poll,
writes that the fish is common around Leopoldville. An unnamed German collector
caught this fish in small pools, ditches and creeks, near Leopoldville. He also
found the species on deep waters in the Stanley Pool in drifting plants. Stanley
Pool has rather soft water - maximum 2 German degrees, pH 6.4-6.7 and a brownish
color from humus. In the forest creeds the water very often is more acetic, pH
values down to 3.4 are found according to the information of the collector Pierre
Brichard (Tropical Fish Hobbyist Oct. 58). We certainly feel a need of further
chemical information about the River Congo. The landscape around Leopoldville has
a rather even mean temperature of about 25.5 C. The annual rainfall is not very
big - 1340 mm a year. The dry season falls in the months June-July-Aug., and July
and August together only have 5 mm. There are two maxima: March (193) and Nov.
(218 mm). In the Stanley Pool the water level changes about 4 meters within the
year. The geological conditions are not very easy to survey and in some places
there are marine deposits. Water conditions may change very much within local
geological formations.
The "cognatum" used to be a very shy fish during the first days or weeks
after the transfer to a new tank. Very often the fishes are terror struck in a
way that in a panic they rush around in the tank and -just like the "labarrei"
(calabaricus and others)- take their own lives by wounds from rocks, stones and
gravel. If peat bottom is used, they will dive into this soft material and rest
there for some days and after this they get more and more accustomed to the tank
and also they may be a little tame in time. If you want to accustom this fish to
the life on mineralic bottom layer, you certainly should keep the fish for some
time in tanks without any bottom layer at all. The male "cognatum" you very often
will find at a certain place in the tank - under some Cryptocorynes, in a corner
and at other dark places. Young fishes often are not very shy and if you keep quite
a lot, you often will see many swimming around in the "free" water. "Cognatum"
is an excellent jumper and he will find any small leak at the aquarium cover. A
leap of 15-20 cm vertically he easily will make during night. Like (all?) other
Aphyosemion it very easily may be accustomed to live in very lighted tanks if it
has some dark places to hide itself. You will often see it out in the bright sunshine.
The "cognatum" very often is swimming in a particular way, he will swim a very short
distance and then stop, then swim again and so on, jerking through the tank. He is a
very good swimmer indeed.
This species will take any food offered - dry food or live food. I have
raised several good stocks on dry food, with only one feeding of live food a week.
But dry food very often will make the water cloudy, and like most other Aphyosemion
it does not like this and folds its fins. Then also often the Oodinium will make an
attack. In 1955, I had some old males in a tank which was placed in the sun and had
lots of green algae. This stock was found to be infected with the severe internal disease,
Ichthyophonus, and I had to kill some of the diseased fish. This showed me that the
intestine often was filled up with green algae, so possibly this food may play a role
in the nourishment of this species.
It stands temperatures from 18-23 C very well, but both colder or hotter
waters will not hurt it. I have kept some stock in alkaline waters (pH above 7.6,
below 8.2, temporary hardness about 15 German degrees) and I certainly was able to
keep the stock alive. But no doubt this water type is not the best one for this
rain forest fish. The "cognatum" is a rather peaceful fish, I do not remember any
difficulties even when many adults were kept in small tanks.
This species is very easy to spawn. My half grown females (in the various
cossings on perlon where eggs always are counted) gave away up to 60 eggs in each
spawning of 2-4 hours. At least you may get about 10 eggs per female and day on good
feeding. The egg is one of the biggest among aquarium kept Aphyosemion - 1.4-1.5 mm.
The surface of the membrane has many thin filaments. In one pole of the egg the filaments
seem to be more concentrated and prolonged. The spawning act takes place among fine plants
or roots near the surface or near the bottom. Spawning may take place just over the bottom
mud. Eggs hatched after 10 to 21 days at room temperature. I never saw any "resting eggs"
or "resting fry", but the German breeders report that at least some "resting fry" often occur
in their spawnings. The eggs are rather tough and you may collect them using your fingers,
I prefer to cut them out of the perlon. My fry measured about 5.0 mm just after the
hatching. During the first few days I often found the fry near or at the surface,
but soon they were seen everywhere in the tank. As they are rather big they will
take big food as newly hatched brine shrimp (Artemia salina), micro worms, etc.
I use to feed a little small sized dry food every day in order to accustom the
fry to this food. The spawning takes place at all temperatures above 18 C. I
breed at 22 C. You should keep the water very clear as the fry does not like
cloudy water at all. Oodinium may then be a problem. During the first weeks
the fry grows rather quickly, but after the beginning of maturity, which is seen
in rather small fishes in this species, the growth is very slow. As in most other
killies the growth of a certain brood is very irregular and some fry very quickly
grow to a size making them able to eat their younger or smaller brothers. But very
often I had broods unsorted and I never saw any of the bigger fry trying to eat their smaller brothers.
Crossings:
This species I have tried in many different crosses because during the
winter of 1957/58 I had a female that spawned with all males I placed her together with.
Aphyosemion calliurum ahli male / Aphyosemion cognatum female: (this was
one of the males imported from Nigeria) 10 Sep. 57: 34 eggs. I had to go away
for about 14 days and had to keep the eggs dry on moist perlon for that time.
25 Sep. 57 they were placed in water. No fry hatched. 27 Sep. 57 I added dry food.
From 9 ripe eggs 9 sound fry hatched out within 10 hours. Only 2 were able to live.
One was a normally developed fry and grew up to be a big male "lab/cog", but did
not have the handsome caudal fin of this hybrid, nor the same brilliance as these.
The other fry had badly deformed under-jaw and this jaw grew out to form a spoon.
He could not close his mouth. He learned to eat using his gills and grew up to
be a very handsome male. The body colors were the same as in his brother, but
(possibly, or no doubt from the "ahli" father) he had a handsome yellow (very
bright) color in the upper part of the dorsal fin, the lower part of the anal
fin and at the upper and lower parts of the caudal fin. He was much more
handsome than his brother, but more feeble. He lived for more than half a
year. 90 days old he measured 27 mm.
Aphyosemion calliurum calliurum / Aphyosemion cognatum female (also an
imported male from Nigeria) 30. Oct. 57: 58 eggs in one spawning. Fry hatched
without any help like this: 14 Nov. 3 fry, 15 Nov. 11 fry, 16 Nov. 12 fry,
17 Nov. 21 fry, plus 11 and after some days 1 fry. 26 fry were placed in one
16 liter all glass tank (usual conditions) on 22 Dec. 57 only 12 were still
alive. Of these only 3 had a normally developed underjaw. The other ones were
"spoon-jawed". The smallest measured 7-8 mm, the biggest 21-22 mm. The other
part of this brood was kept in another 16 liter tank. On 22 Dec. 57 these were
also caught. 25 fry (have been 43 fry) 9 normally developed fry, 13 fry clearly
"spoon jawed". This tank also had some fry of the same cross type (10 fry from
a spawning on 08 Nov. 57, hatched 23-29 Nov. 57). After 45 days the biggest fry
began to show colors. About 24 mm. Later all deformed fry died (Oodinium and
weakness) but many of the normal ones lived to maturity and some were sent alive
to Amsterdam. I now keep only one (05 May 59) of these hybrids. About 55 mm.
None of these many males had any yellow color in their fins. They were like the
biggest fry of one cross. They often suffered from attack by Oodinium. All these
fry grew up to be true males (in coloration) but all were 100% sterile.
On 01 May 58 I had only about 8 of these hybrids left from hatching of about 80 fry. Very bad indeed.
Aphyosemion australe male / Aphyosemion cognatum female (still the same female)
14 Nov. 57: 32 eggs. 07 Dec. 57: many of these eggs have developed a small embryo,
but this is not at all normal to look at. Cannot possibly live. 17 Dec. 57. Only
a few eggs left, embryos dead in all eggs, one embryo taken out of its egg. 1.2-1.3 mm,
preserved. 27 Dec. 57: not a single unbroken egg left in the glass. 30 Nov. 57: 35 eggs
(perhaps another male used). No eggs got fungus. Much better development of fry inside
the eggs, also much better development of blood system.
Second cross "australe" male / "cognatum" female: apparently no egg was attacked
by fungus. 27. Dec. 57 embryos in eggs are apparently dead. Took one fry out of the egg
using needles. Fry is not quite dead, slow circulation of blood elements, movements
of pectorals. Fry measured 2.5--2..6 mm, died on 29 Dec. 57. No fry came out of this cross.
Aphyosemion labarrei male / Aphyosemion cognatum female: (same female as in the
other crosses) 05. Dec. 57 50 eggs spawned within a few hours. 09. Dec. 57: embryo
moves his tail in egg, no eggs got fungus. 16 Dec. 57: very fine development of embryo.
18 Dec. 57: they seem to be ready for hatching. 22 Dec. 57: 4 fry hatched without any help.
24 Dec. 57: 3 fry. 25 Dec. 57: 1 fry, then added dry food: after 2 hours 9 fry, after
2 1/2 hours (totally): 4 fry, after 3 hours 4 fry, later 6 fry. Once more in "dry food water"
on 26 Dec. 57: 17 fry hatched. Totally 48 fry. The fry measured 5.0 mm, all had that size.
These fry had "shining eyes" as have fry of labarrei. 17 Mar. 58 the fry were caught and
counted, I found 44 sound fry. They looked like young "cognatum". These hybrids grew up
to be very sound fishes, no diseases at all, also they were most handsome, possibly the
most handsome of all Aphyosemion. Most were males, the rest were not females as none
ever spawned a single egg. These "intersexes?" were colored in same way as young males
"cognatum" but like the real males there were by far not so many red dots on the sides.
The males took on that very brilliant blue cast on the whole body which we find in
matured "labarrei". But they were all "Haplochilus" as "cognatum" (dorsal fin inserted
behind anal fin). In particular the caudal fin was of very fine shape and very close
to the shape and colors we find in "schoutedeni". Live and preserved specimens were
mailed to Dr. Hoedemann. I still keep (29 may 59) some of the males and a few "females"
which tomorrow will be mailed to Dr. Foersch to be photographed. Several males and
"females" were tried in back crosses to females "cognatum" and "labarrei" but I did
not see any fertile eggs. So possibly these hybrids were as sterile as most other
hybrids in Aphyosemion. 1 7 Dec. 57: same cross 5 eggs. First fry hatched on 03 Jan. 58.
Epiplatys chaperi male / Aphyosemion cognatum female: (same female)
01 Feb. 58: 7 eggs spawned, 03 Feb. 58 one egg got fungus, 6 eggs are fine.
06 Feb. 58 5 eggs left, these show very promising development, the development
of blood system is very fine. 08 Feb. 58 all eggs are OK, the eyes are now fully
pigmented. 11. Feb. 58 now some of the eggs apparently stop the development and
the development is not at the same state in the eggs. 15 Feb. 58 all 5 embryos
are alive, the heads are deformed, they possibly will not live for any long time.
7 Feb. 58 embryo dead in one of the eggs, other embryos are dying: preserved.
Aphyosemion (?) petersi male / Aphyosemion cognatum female (same female)
18 Jan. 58 7 eggs. 21 Jan. 58 one egg inspected. Embryo "180 degrees", transparent.
Eyes unpigmented. 26 Jan. 58 the eye is pigmented, the development of blood system
is very weak. 29 Jan. 58 development of blood system is much better now.
01 Feb. 58 the circulation of blood elements has stopped, the egg was preserved.
Aphyosemion sjoestedti male / Aphyosemion cognatum (same old female) Indeed
I was not very optimistic because the male was much larger than the female and
"sjoestedti" does not like to spawn on perlon. But the good old female at once
invited the big male and certainly after a few minutes this grotesque "pair" was
spawning normally. After a few hours I cut 57 eggs out of the peron.
17 Feb. 58 53 eggs were lifted out, not fertile. 4 eggs may be fertile, but
they are all very green from the Euflavine/Methyleneblue mixture.
19 Feb. 58 only one egg left in the glass. The yolk ball is unbroken and has
not taken up the green color. This egg was then kept until 22 Apr. 58 and inspected on 21, 25, 28 Feb.,
13 Mar. and so on. But it did not change. There was a formless mass of cells over 180 degrees of the yolk.
Crosses in which "cognatum" male was used will be referred to in connection with the female species used.
