Nothobranchius elucens

biology_ecology

Ecology. The northern highlands of Uganda experience a mean annual rainfall of around 1500 mm concentrated with two peaks in May and August (Hughes & Hughes 1992). Wetlands are at their lowest levels in January, when seasonal streams and most temporary habitats are dry. At the type locality, Nothobranchius elucens was the only fish species found. The accompanying fauna consisted of tadpoles of unidentified species. The type locality is a large temporary pool formed on the floodplain of the seasonal Aringa River (Fig. 6). The habitat belongs to category 1.1, as defined by Watters (2014), representing an isolated pool in a shallow depression on a floodplain, formed primarily as a result of natural processes. At the end of the first peak of the rainy season, the habitat was a large and shallow pool more than 50 m long and about 30 m wide, and about 1 m at the deepest point. At the type locality, all collecting took place in the same general habitat. Aquatic vegetation comprised Nymphea sp., whereas the edge of the habitat was partially overgrown with grass. The water was turbid, the bottom of the pool was not visible. The water temperature around noon was 33.6 ° C, the pH was 7.8 and

Nothobranchius elucens, a new species of seasonal killifish from the upper Nile drainage in Uganda (Cyprinodontiformes: Nothobranchiidae)

description

Description. General body features illustrated by Figures 2 – 4. Morphometric and meristic characters of holotype and paratypes summarised in Table 1. Relatively small-sized Nothobranchius species, maximum observed length of specimens examined 35.7 mm SL. General body shape robust, laterally compressed and deep. Greatest body depth at vertical passing through pelvic-fin origin: 28.4 – 33.8 % SL. Greatest body width at pectoral-fin base with body progressively narrowing towards caudal-fin base. Dorsal profile convex from tip of snout to base of last dorsal-fin ray; postdorsal profile straight to slightly concave on caudal peduncle. Ventral profile convex from lower jaw to base of last anal-fin ray; postanal profile straight to slightly concave on caudal peduncle from insertion of posteriormost anal-fin ray to caudal-fin base. Caudal peduncle shallow, length 1.45 – 1.52 times of its depth. Anus just anterior to anal-fin origin. Head moderately long (29.5 – 33.1 % SL), laterally compressed, deeper than wide (head width 66 – 72 % of its depth). Snout slightly pointed, smaller than eye diameter. Mouth supraterminal, slightly oblique in profile. Jaws subequal, lower jaw longer than upper

Nothobranchius elucens, a new species of seasonal killifish from the upper Nile drainage in Uganda (Cyprinodontiformes: Nothobranchiidae)

diagnosis

Diagnosis. Nothobranchius elucens is distinguished from all other members of the genus by the following characters in males: body colouration golden-grey with brown scale margins creating irregular vertical stripes on trunk; anal fin yellow with brown spots proximally, with slender brown median band, followed by a slender light blue subdistal band and a slender black distal band; caudal fin brown proximally and medially, followed by a slender light blue subdistal band and a slender black distal band; dorsal fin golden with irregular brown blotches and stripes, with narrow light blue subdistal band and narrow black distal band. Furthermore, it differs from N. taiti by the morphometric characters of having a smaller head length of 29.5 – 33.1 % SL (vs. 35.0 – 38.6 %); smaller prepectoral length of 31.2 – 33.9 % SL (vs. 34.2 – 38.6 %); greater head depth of 81 – 87 % HL (vs. 71 – 80 %); greater interorbital width of 43 – 49 % HL (vs. 31 – 40 %); and greater caudal peduncle length of 145 – 152 % of its depth (vs. 134 – 143 %).

Nothobranchius elucens, a new species of seasonal killifish from the upper Nile drainage in Uganda (Cyprinodontiformes: Nothobranchiidae)

distribution

Distribution. Nothobranchius elucens is currently known from a temporary swamp formed in the floodplain of the seasonal Aringa River system (Fig. 5). The Aringa flows into the Pager, which is a tributary of the Achwa within the upper Nile drainage in northern Uganda.

Nothobranchius elucens, a new species of seasonal killifish from the upper Nile drainage in Uganda (Cyprinodontiformes: Nothobranchiidae)