Neoleptastacus longiremis ( Chappuis, 1955 ), 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 : 20-21

Neoleptastacus longiremis ( Chappuis, 1955)

Arenopontia longiremis Chappuis, 1955

Arenopontia (Neoleptastacus) longiremis Chappuis, 1955 : Wells (1967: 324)

Arenopontia (Neoleptastacus) acantha longiremis Chappuis, 1955 : Kunz (1971: 356)

Neoleptastacus longiremis ( Chappuis, 1955) Sak et al. (2008: 412)

Original description. Chappuis (1955): 54–55; Figs 38–47.

Additional description. Wells (1967): 326–327; Text-Fig. 66M–P.

Type locality. Madagascar, Toamasina Province (east coast), Ambila Lemaitso ; sandy beach; muddy fine sand near high-tide mark.

Body length. 390 μm (♀ and ♂) [ Chappuis 1955].

Remarks. The linear egg-sac contains three eggs ( Chappuis 1955). The sexual dimorphism in shape and form of the P5 is remarkable but was not commented upon by Chappuis (1955). The fifth legs not only differ profoundly in general shape between both sexes but also in the relative length of the setal elements. Since such dimorphism has not been recorded elsewhere in the Arenopontiidae , it calls for confirmation whether the females and males recorded from Madagascar belong to the same species. Chappuis (1955) reported “quelques males et femelles” but did not expressly designate a holotype or syntypes. According to ICZN Art. 72.1.1, in the absence of such (or subsequent) designation, all specimens examined by Chappuis are syntypes and collectively constitute the name-bearing type. Since no name-bearing type specimen is believed to be extant or traceable we consider it desirable at present to designate such a specimen to define the nominal taxon objectively in the likely event that females and males attributed to N. longiremis turn out to be non-conspecific. Consequently, we here designate the male specimen illustrated in Chappuis (1955: Figs 41–43, 46–47) as the lectotype selected from the specimens that Chappuis had at his disposal in accordance with ICZN Art. 74.4.

The only potentially reliable records outside Madagascar are by Chappuis (1955) who recorded a single male from Anjouan ( Comoro Islands) and by Wells (1967) who distinguished two varieties in littoral material from Ilha dos Portuguesos and Inhaca Island (Ponta Torres) in Mozambique. The long variety has an elongate caudal ramus resembling the type material, the short variety has a much shorter caudal ramus, more like that of N. acanthus . Re-examination of this material is required before these forms can be attributed with confidence to N. longiremis or, alternatively and more likely, be considered closely related sympatric species. It is noteworthy that the paired anal processes are laterally displaced and distinctly straight in Chappuis’s types but dorsally recurved in the Inhaca material [J.B.J. Wells, pers. comm. in Itô (1978)]. The validity of Chappuis & Delamare Deboutteville’s (1956) record from North Bimini (Sharktown beach) in the Bahamas (see also Renaud-Debyser 1963) was rightly questioned by Lang (1965), and Rouch’s (1962) record from Mar del Plata in Argentina is probably equally unreliable. Chappuis & Rouch’s (1961) material from Ghana belongs to N. accraensis ( Lang 1965) which is treated here as a species inquirenda (see below). Rao (1980) listed “ Arenopontia longiremis Chappuis ?” in his list of interstitial meiofauna species of the Andaman and Nicobar Islands but it is likely that this material refers to atypical populations of N. indicus (cf. Wells & Rao 1987: 165).

Although Wells (1967) advocated a close relationship between N. acanthus and N. longiremis , it is clear that the latter belongs to a different subgroup that unites at least seven closely related species characterized by the presence of only one distal element on P3 enp-2 ( Table 2 ). Within this gussoae -subgroup, N. longiremis shares with N. rectus sp. nov. the straight outline of the backwardly directed paired spinous processes on the anal somite but can be differentiated from this species by (1) the shorter P1 endopod (enp/exp length ratio 1.15 vs 1.30) and (2) the length/maximum width ratio of the female (3.0 vs 1.7) and male (3.5 vs 2.25) P5.