Neoleptastacus africanus ( Chappuis & Rouch, 1961 ), 2008

Sak, Serdar, Karaytuğ, Süphan & Huys, Rony, 2024, Review of Neoleptastacus Nicholls, 1945 (Harpacticoida, Arenopontiidae), including an updated key to species and proposal of Phreatipontia gen. nov., Zootaxa 5525 (1), pp. 1-66 : 21

Neoleptastacus africanus ( Chappuis & Rouch, 1961)

Arenopontia africana Chappuis & Rouch, 1961

Arenopontia (Neoleptastacus) africana Chappuis & Rouch, 1961 : Wells (1967: 324)

Arenopontia (Neoleptastacus) africana f. africana Chappuis & Rouch, 1961 : Kunz (1971: 358)

Neoleptastacus africanus ( Chappuis & Rouch, 1961) Sak et al. (2008: 412)

Original description. Chappuis & Rouch (1961): 606–607; Figs 1–8 .

Type locality. Ghana, Greater Accra Region, Accra ; in front of lighthouse .

Body length. 380 μm (♀); unknown for ♂.

Remarks. Neoleptastacus africanus belongs to the trisetosus -group based on (1) P1 exp-1 without outer spine, (2) distal segment (exp-3, or exp-2 when exopod 2-segmented) with only one outer spine, (3) P2 exp-2 with very long outer setiform element (extending far beyond distal margin of exp-3), (4) P2–P3 endopods 1-segmented with reduced armature (010), and (5) outer seta of P4 enp-2 reduced. Within this group it is morphologically most similar to its geographically closest member, N. angolensis comb. nov., with which it shares the 3-segmented condition of the P1 exopod, a distinctly elongate P4 exopod, the reduced armature on the fifth legs, and the presence of a middorsal process on the anal operculum. Kunz (1971) listed seven differences between N. africanus and N. angolensis comb. nov. but at least five of them appear unreliable or incorrect, e.g. (1) Kunz (1971) claimed that the outer spine on P1 exp-1 is present in N. africanus but the short outer element figured by Chappuis & Rouch (1961) appears too small to be a genuine spine (when present, its size invariably approaches that of the outer spines on exp-3) and is interpreted here as a spinule (as found in the same position in other species of the genus); (2) according to Kunz (1971), P4 enp-2 has only one seta but Chappuis & Rouch (1961) clearly stated (and illustrated) that the long distal seta is accompanied by “... une fine soie au bord externe”; (3) the difference related to the antennary exopod (represented by seta vs unisetose segment) is ambiguous because Chappuis & Rouch (1961) were not explicit about its condition (“Exopodite de l’antenne II, une soie courte et mince”; and (4) the pinnules bordering the anal operculum in N. africanus are not part of the opercular ornamentation but a misinterpretation of the underlying incised anal frill. Both species require thorough redescription but can be distinguished at present by the shape/curvature of the P5 and caudal rami. The number of spiniform armature elements on the P5 is reduced in both species, being one in N. angolensis comb. nov. and none in N. africanus . The species is known only from the type locality.

Figures

FIGURE 1. Neoleptastacus acanthus (Chappuis, 1954) (♀): (A) habitus, dorsal; (B) habitus, lateral; (C) rostrum, dorsal.

FIGURE 2. Neoleptastacus acanthus (Chappuis, 1954): (A) habitus (♂), dorsal; (B) anal somite and caudal rami (♀), dorsal; (C) anal somite and left caudal ramus (♀), lateral; (D) antenna (♀), medial; (E) antennary endopod (♀), outer. [Lateral spines of antennary endopod indicated by arrows in D–E]

FIGURE 3. Neoleptastacus acanthus (Chappuis, 1954): (A) antennule (♀), dorsal; (B) antennule (♂), ventral. [spatulate setae indicated by arrows]

FIGURE 4. Neoleptastacus acanthus (Chappuis, 1954) (♀): (A) P1, anterior; (B) P2, anterior; (C) P3, anterior; (D) P4, anterior.

FIGURE 5. Neoleptastacus acanthus (Chappuis, 1954): (A) urosome (♀), ventral [caudal ramus seta V figured at full length in inset]; (B) urosome (♂), ventral.

FIGURE 6. Neoleptastacus emendatus sp. nov. (♀): (A) habitus, dorsal; (B) habitus, lateral; (C) anal somite and caudal rami, dorsal; (D) anal somite and right caudal ramus, lateral.

FIGURE 7. Neoleptastacus emendatus sp. nov. (♀): (A) urosome, ventral; (B) antennule, dorsal; (C) antenna, outer; (D) antennary endopod, medial; (E) rostrum, dorsal; (F) midventral hook-like processes [indicated by arrows] on pedigerous somites; (G) hook-like process, lateral. [lateral endopodal spines indicated by arrows in C–D]

FIGURE 8. Neoleptastacus emendatus sp. nov. (♀): (A) P1, anterior; (B) P2, anterior; (C) P3, anterior; (D) P4, anterior.