Lepidarchus
A remarkable genus of tiny African characoid fishes, outstanding from its relatives in having only one cycloid scale on either side at the anterior part of anal fin base, and two or three modified scales forming a short bony canal for the lateral line, lying immediately in front of the pseudotympanum, whereas it is otherwise scaleless. The premaxillary and dentary each have a single row of conical teeth; the maxillary is toothless.
Synonym
Lepidarchus adonis signifer Isbrücker, 1970
Type species
Lepidarchus adonis Roberts, 1970 by monotypy.
Currently, Lepidarchus is monospecific.
Bibliography
Lepidarchus adonis Roberts, 1966
Type and type locality
Lepidarchus adonis Roberts, 1966: 209-216, fig. 1-11. Type locality: “Road to Half-Assimi, W. Ghana”. Holotype: CAS-SU 63546. Paratypes: MRAC 154701-154702; CAS-SU 63460-63461, 63462; USNM 202502 (ex CAS-SU 63462).
Common names
Danish: Adonistetra
English: Adonis characin/Adonis tetra (USA), Jellybean tetra (USA, Global)
Estonian: Adoonistetra
Finnish: Adonistetra
German: Adonissalmler
Description
Diagnosis: body depth 3.5-4.2 and head length 3-3.5 in standard length. Slightly prominent lower jaw or jaws roughly equal. Parietal fontanel present. Dental formula: [16-17 (upper jaw), 20-21 (lower jaw)] in a single row and all of them are unicuspidate. Unpaired rays non-filamentous. Dorsal fin: II,7-9 (rarely 7). Anal fin: II,9-10. Gill rakers on the lower limb of the first gill arch: 12. Body naked except for one scale located on both side of the flanks at anal fin origin. Lateral line absent except for a tube near gill-slit.
Lepidarchus adonis: main morphometric data.
Maximum reported size: 21 mm SL.
Colour: translucent body in live specimen. Male: two dozen crimson blotches or more, on the posterior half of the body and caudal fin lobes. Pelvic and anal fins with crimson or black blotches and bars. Female: without any black spots.
Remark: in 1970, Isbrücker described a new subspecies from Liberia, Lepidarchus adonis signifier. According to the author himself, L. a. signifier differs from L. a. adonis mainly in colouration. Morphometrically the two subspecies cannot be separated clearly, except there seems to be a tendency towards a shorter head in L. a. signifer. Faced with so few arguments, we consider that there are several populations. So, L. a. signifer must be synonymysed with L. a. adonis.
Distribution
Small coastal basins in the southern areas of Ghana, Côte d'Ivoire and Liberia (see also Faunafri).
The species is currently known from about six to five locations in the southern areas of Ghana, Côte d’Ivoire and Liberia. There is no data on continuing decline in population or quality of habitat, however the species is potentially threatened by pollution from agriculture, industry and domestic sources.
Major threats: there is a potential threats to this species include invasive aquatic weeds and increasing levels of agrochemicals from farming activities in areas around the water bodies, and effluents from mining activities in the upper reaches of these coastal rivers especially the Ankobra and Tano. These effluents may contain heavy metals like arsenic, mercury and compounds like cyanide. Also, the removal of vegetation pertaining to mining activities, and commercial timber felling, may cause increasing sediment loads, and its attendant problems to the life of the fish. Timber felling is an especially important threat in the Tano. Another major threat is pollution of the water bodies by inadequately treated human waste and by domestic discharges.
Bibliography
