Zaireichthys lacustris

Zaireichthys lacustris, an amphiliid catfish;
a possibly inquiline species found with the cichlid Maylandia livingstonii
in Lanistes snail shells in Lake Malawi;
photo by W. E. Burgess, used by permission of T.F.H. Publications

Zaireichthys rotundiceps, an amphiliid catfish;
a near relative of the endemic Z. lacustris
found in Lake Malawi; illustration from Jubb (1967), used by
permission of A. A. Balkema Publishers

Zaireichthys lacustris
by Michael K. Oliver, Ph.D.
A small amphiliid catfish, formerly placed in the genus Leptoglanis but currently (Snoeks, 2004b; Eccles et al., 2011) classified in the genus Zaireichthys, is found in Lake Malawi (top photograph above). This catfish, now know to be a Lake Malawi endemic, was recently given a scientific name: Zaireichthys lacustris Eccles, Tweddle, & Skelton, 2011. Previously, this species was known only as a member of the Zaireichthys rotundiceps species complex and was designated Zaireichthys sp. 3 (Snoeks, 2004b, who misspells the genus 'Zaireichtys'). Z. rotundiceps itself, the "Spotted sand catlet," is shown in the lower illustration above. A comparison of the two illustrations shows that, although the fish in the photo (upper image) is much smaller (as seen by the relatively large eye and short snout and the transparency of the body), both fishes share very similar pigmentation patterns. There is one additional nomenclatural complication: it has been controversial if Zaireichthys and Leptoglanis belong in the family Amphiliidae or the family Bagridae. However, in his comprehensive checklist of catfishes, Ferraris (2007) assigned Zaireichthys to the Amphiliidae. Extensive study of the phylogeny of catfishes continues, and a more stable familial classification can be expected eventually.
To my thinking, the Lake Malawi species (Z. lacustris) apparently resembles even more closely the species seen at right — the diminutive "Chobe sand catlet," once known as Zaireichthys cf. dorae. Its confirmed range is well to the west of Lake Malawi, and includes the Okavango, Kwando, Chobe, and Upper Zambezi systems (Skelton, 1993). I am uncertain which one of the two species (Z. pallidus and Z. conspicuus) that Eccles et al. (2011)) described from the Chobe system is the "Chobe sand catlet" illusrated here.
Lake Malawi's Z. lacustris catlet has only been collected from the empty shells of large dead Lanistes nyassanus snails on sandy shores of the lake and was long thought to live as an inquiline or "house guest" with the cichlids Maylandia livingstonii or M. lanisticola in these shells (Burgess, 1976c). Eccles et al. (2011: 14) argue, however, that a symbiotic relationship between the catfish and the cichlid
"... is unlikely since Z. lacustris is also found in shells of Bellamya spp., which are too small to be used by P. lanisticola. It is more likely that the co-existence of the two fish species in one shell is fortuitous and that the catfish occupies the upper part of the shell which the cichlid cannot reach."
The Z. rotundiceps complex as a whole is distributed from Kenya and Tanzania through Zambia and Zimbabwe to South Africa. In its typical, shallow-water habitat in rivers, Z. rotundiceps itself "[o]ccurs over sand, usually buried with just the eyes protruding. Feeds on minute organisms. Eggs few (12-16) and large (3-5 mm diameter) suggesting possible parental care" (FishBase).
Credits: The top photograph above, by Dr. W. E. Burgess, is reproduced from Burgess (1976c) by permission of T.F.H. Publications, Inc.; special thanks to Dr. Sven Kullander for providing a copy of this article. The same photo also appears in the large T.F.H. book by Konings (1990a: 478). The black & white illustration above, a drawing by Hilda M. Jubb, is from Jubb (1967), and is used by kind permission of Mr. A. T. Balkema of A. A. Balkema Publishers, Rotterdam. Finally, the color painting of the Chobe sand catlet, by Dave Voorvelt, is copyright © by the South African Institute for Aquatic Biodiversity (formerly known as the J.L.B. Smith Institute of Ichthyology). It is reproduced here from Skelton (1993) with the kind permission of Prof. P.H. Skelton.

The Cichlid Fishes of Lake Malawi, Africa: MalawiCichlids.com