Congo Killies - PageSuite

oon. It is not unlikely that the change
in the direction of flow of the Dja,
which originally drained to the Atlantic
coast, was originally responsible for
the spread of Raddaella into the Congo
Basin via the Ngoko, a tributary of
the Likouala. Raddaella then spread
upstream in an easterly direction. That
wouldn’t have been difficult—in this region
the Congo has a drop of only 328
feet (100 m) over a distance of 1,242
miles (2,000 km), so it is more like a
lake than a river.
“Aphyosemion” escherichi from Mayombe,
collected by A. Van Deun (May 2011) in Bas Congo.
TOP: K. STEHLE; BOTTOM: H. OTT
Aphyosemion sensu stricto
This group contains the majority of the
Aphyosemion s. l. species of the Congo
Basin. They are broadly identical in
morphology but differ considerably in
the coloration of males and in their
DNA. Eighteen species are currently
recognized. The distribution of most
species is very complex and exhibits a
mosaic-like, parapatric pattern. They
sometimes also occur sympatrically,
that is, in the same river system. However,
in only a few cases to date are two
species known to be syntopic (found at
the same site).
Aphyosemion castaneum (Myers 1924) was described
by the author from preserved material collected by an
American expedition to the Congo. He established that
the genus used in those days for more slender killifishes
of Africa, Haplochilus (Aplocheilus, now restricted to Indian
and Asian species), didn’t constitute a homogenous
group, and straightaway described the genus Aphyosemion.
His newly described species A. castaneum was
designated the type species of the genus. Authors such
as Scheel, Radda, and Wildekamp regard A. castaneum as
a synonym of A. christyi, but it has recently been shown
that the occurrence of A. christyi is restricted to the
eastern part of the Congo Basin at altitudes of 1,640 feet
(500 m) and up, and that A. castaneum represents a valid
species (Van der Zee & Huber 2006).
Aphyosemion chauchei (Huber & Scheel 1981) is
a “blue” species with blue dorsal and caudal fins and
a yellow anal fin, found in a very limited area in the
Congo Republic. In the west and south it is replaced by
a “yellow” species with yellow fins, shown on the map
as A. “schioetzi.” The body forms of A. “schioetzi” and
A. chauchei are identical. They are relatively small and
slender Aphyosemion species, unlike A. schioetzi, which is
a comparatively robust species. Aphyosemion schioetzi and
A. “schioetzi” are separated by a large distributional gap,
and we believe that they do not represent a single species.
Whether A. “schioetzi” is an as-yet-undescribed species
Aphyosemion castaneum (HZ 85/8), north of Kisangani.
remains unclear at present (see also A. decorsei). With
one exception, all known locations for A. chauchei lie in
the southern Likouala basin. A population from Olombo,
which differs in color pattern from the Likouala populations,
lives in the Alima drainage.
Aphyosemion christyi (Boulenger 1915) is restricted to
the Ituri forest region northeast of Bafwassende. Aphyosemion
margaretae (Fowler 1936) is regarded as a synonym
(Van der Zee & Huber 2006). Wild-caught specimens of
this species have a very typical violet coloration. Even in
poor-quality photos the species can be easily identified on
this basis. Aphyosemion christyi is very widespread in the
Okapi Faunal Reserve. Several collections have been made
there recently by Emmanuel Vreven (RMCA) and his
colleagues. So far, this is the only species of the A. elegans
group that can be identified by its meristics (countable
traits), as on average it has more rays in the dorsal fin
than the other species.
Aphyosemion cognatum (Meinken 1951) has a very
large distribution in the southern Congo. The distance
from west to east is almost 559 miles (900 km). At the
same time, the species exhibits numerous different phenotypes.
The DNA of an aquarium strain of one of the
eastern populations (Lake Fwa) was studied by Murphy
& Collier (1999). It turned out that were no differences
between the Lake Fwa and the Kinsuka populations (Van
der Zee & Sonnenberg 2011). Hence it is possible that
AMAZONAS
27