Scientists have undertaken a revision of the Synodontis catfish of Lake Tanganyika in East Africa and have identified 11 species, three of which are new to science.
Jeremy Wright and Larry Page of the University of Florida studied 312 museum specimens of Synodontis recorded from Lake Tanganyika and recognised 11 species as valid.
Their findings have recently been published in the Florida Museum of Natural History Bulletin.
Synodontis dhonti, S. granulosus, S. irsacae, S. melanostictus, S. multipunctatus, S. petricola, S. polli and S. tanganicae are regarded as valid species, while S. grandiops, S. ilebrevis and S. lucipinnis are described in the paper as new species.
Synodontis grandiopsSynodontis grandiops is very similar in appearance to the Cuckoo catfish, Synodontis multipunctatus, whose eggs are brooded in the mouths of mouthbrooding cichlids - a reproductive method known as brood parasitism.
Unlike S. multipunctatus, S. grandiops has a larger eye - measuring 64.2-81.0% of the snout, compared to 44.9-62.0% of the snout in multipunctatus. It also has seven pectoral fin rays, rather than the eight typically seen in multipunctatus.
Synodontis grandiops, which has previously been confused with S. multipunctatus by previous scientists, also remains much smaller - reaching just 15cm/6", compared to the maximum size of 28cm/11" recorded for multipunctatus.
The fish is bright silver-white in colour, with an irregular pattern of large dark irregularly shaped spots and blotches, as well as a dark black bar on each lobe of the caudal fin.
Wright and Page believe that grandiops is common in Lake Tanganyika (though less common than multipunctatus) and lives on shell, sand and mud bottoms in the littoral and benthic parts of the Lake.
Synodontis lucipinnisThe petricola-like Synodontis lucipinnis is believed to be the same species sold in the aquarium trade under the Dwarf petricola common name.
Reaching a size of up to 10cm/4" TL (some 3.5cm smaller than the largest petricola), morphometrically it differs very little from petricola, making the fish somewhat tricky to tell apart.
Synodontis lucipinnis can be distinguished from petricola by the lack of an axilliary pore and the presence of "light-coloured windows" at the bases of the rayed fins.
It is known only from the Musende Rocks of Mpulungu in Zambia, at the southernmost tip of the Lake.
Synodontis ilebrevisThe third new species, Synodontis ilebrevis, is most similar to Synodontis polli. It is difficult to tell apart from polli.
"Synodontis ilebrevis differs from S. polli in having a short gut (0.8-1.4 times TL vs 4.0-5.5 times TL in S. polli), no hindgut chamber, slightly shallower body (body depth 18.2-20.1% SL vs 20.2-27.0 in S. polli), short flat papillae on the skin (vs villous papillae in S. polli), and small, round, widely spaced spots on the skin (vs moderate to large, irregular, more closely spaced spots in S. polli".
It reaches a maximum size of 15cm TL (around 12cm/5" SL), slightly smaller than the maximum recorded size for S. polli at 18cm TL.
S. ilebrevis is only known from the Cape Chaitika area in the southern part of the Lake, and is believed to inhabit fairly shallow rocky coastal areas, like other small-bodied Tanganyikan Synodontis.
Tanganyikan SynodontisThe study recognises 11 species of Lake Tanganyika Synodontis, ten endemic and three new to science. It also brings Synodontis irsacae and S. melanostictus (the only non-endemic species) out of synonymy.
Wright and Page believe that the group is also monophyletic (descended from a single common ancestor) on account of their distinctive rayed-fin colour pattern, and the present of folds in the fishes' skin.
All species live mainly on the rocky shorelines of the Lake, but are also found over sand and shell bottoms.
Lake Tanganyika is over 1400m deep in places, but most species are confined to relatively shallow depths due to the lack of oxygen deeper down.
The Synodontis species are believed to live at maximum depths of 50-100m in the northern end of the Lake, and as deep as 240m in the southern end.
ChecklistThe study recognises the following species as valid:
Synodontis dhonti
Synodontis grandiops n. sp.
Synodontis granulosus
Synodontis ilebrevis n. sp.
Synodontis irsacae
Synodontis lucipinnis n. sp.
Synodontis melanostictus
Synodontis multipunctatus
Synodontis petricola
Synodontis polli
Synodontis tanganaicae
The Synodontis genus now contains over 118 species. It is one of eight genera in the family Mochokidae.
For more details see the paper: Wright, JJ and LM Page (2006) Taxonomic revision of Lake Taganyikan Synodontis (Siluriformes: Mochokidae). Florida Mus. Nat. Hist. Bull. 46(4):99-154.