Pollimyrus castelnaui has been given the colorful name
"Dwarf stonebasher" (from its feeding motions, I suspect)
among English-speaking southern Africans.
This is indeed the smallest mormyrid known from Lake Malawi,
reaching only 7 cm (2¾ inches) in standard length
(without caudal fin). It is distributed from the Cunene River on Africa's
Atlantic coast eastward to Tanzania. I include the species in this
listing because Skelton (1993) states
that it is "...found in northern areas of Lake Malawi."
No details of the lakeshore localities are available in Skelton or in
FishBase.
Except for its usual habitat, "dense vegetation along margins of
rivers and floodplain lagoons" (Skelton), nothing is known of its
biology.
Pollimyrus castelnaui was classified in the genus
Marcusenius until 1971. Around Lake Malawi it is most
likely to be confused with
Petrocephalus catostoma,
but P. castelnaui is the only mormyrid in the area
to share all of the following characteristics
(adapted from Skelton, 1993: 92-93):
Length of dorsal fin base shorter than anal fin base;
Chin without a swelling;
Mouth small and subterminal (located only slightly below the middle
of front of head); and
Anterior and posterior nares (nostrils) on each side of head are
separated by more than the diameter of each.
