Neoleptastacus indicus ( Rao, 1967 ), 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 : 22-24

publication ID	https://doi.org/ 10.11646/zootaxa.5525.1.1
publication LSID	lsid:zoobank.org:pub:7F2F59B2-E0FB-4E17-BAF1-31228DB9428E
DOI	https://doi.org/10.5281/zenodo.14042367
persistent identifier	https://treatment.plazi.org/id/627EC678-F773-FFA8-FF4E-FF3E7FC0FAD9
treatment provided by	Plazi
scientific name	Neoleptastacus indicus ( Rao, 1967 )
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Neoleptastacus indicus ( Rao, 1967) View in CoL

Arenopontia indica Rao, 1967 View in CoL

Arenopontia (Neoleptastacus) indica Rao, 1967 View in CoL : Itô (1978: 52), Bodin (1979: 124)

Arenopontia (Neoleptastacus) sakagamii Itô, 1978 View in CoL : Wells & Rao (1987: 163)

Neoleptastacus indicus ( Rao, 1967) Sak et al. (2008: 412) View in CoL

Original description. Rao (1967): 129–131, Figs 1 View FIGURE 1 and 2 View FIGURE 2 (1) [adults]; 131–136, Figs 2 View FIGURE 2 (2–7) and 3 [developmental stages].

Additional descriptions. Itô (1978 —as A. (N.) sakagamii ): 47–55; Figs 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 ; Table 1 View TABLE 1 . Wells & Rao (1987): 163–165; Figs 132–133; Table 9. Rao (1989a): 64–65.

Type locality. India, Andhra Pradesh, Vishakhapatnam (= Waltair), Palm Beach ; intertidal zone; salinity 24– 34‰.

Body length. 560–600 μm (♀), 540–580 μm (♂) [ Rao 1967]; 450–480 μm (♀), 430–470 μm (♂) [ Itô 1978]; 380–600 μm (♀) [ Wells & Rao 1987]; 520–560 μm (sex not specified) [ Rao 1989a, 1991]; 520–540 μm (sex not specified) [ Rao 1993].

Remarks. Rao (1967) showed two setae on the antennary exopod of N. indicus , a character he claimed to be already expressed at copepodid I stage. A similar condition was reported by Cottarelli (1973a: Fig. 14 View FIGURE 14 ) for the closely related N. gussoae ( Cottarelli, 1973a) . Both reports are based on observational errors since the shorter outer element is a mere extension of the distal corner of the segment and can be variable in length among members of the genus. Wells & Rao (1987) and Rao (1989a, 1991) noted that the spur illustrated by Rao (1967) on the outer lateral surface of the caudal ramus [and which was considered potentially homologous with seta I by Itô (1978)] in reality arises from the medial surface [as already suspected by Mielke (1987: 334)]. Unfortunately, Wells & Rao (1987) also introduced an error with regard to the P1 which was described (cf. setal formula) and illustrated (their Fig. 133a) with two geniculate setae and one spine on enp-2. Similarly, they illustrated the inner apical seta of P4 enp-2 as distinctly shorter than the outer apical one (their Fig. 133d) while it is consistently longer in all other members of the gussoae -subgroup.

Cottarelli (1973a) discussed the close relationship between N. indicus and N. gussoae , pointing out differences in mandibular palp segmentation, abdominal hyaline frill structure, morphology of P5 and caudal ramus, number of eggs contained in the egg-sac, and body length. Itô (1978) expanded the discussion on the gussoae -complex by including N. longiremis and a new species—originally described as Arenopontia (Neoleptastacus) sakagamii Itô, 1978 —from Kita Harbour on Hahajima in the Bonin Islands (= Ogasawara Gunto), Japan. He maintained all four species as distinct taxa based on a comparison of five characters: (1) caudal ramus with/without medial spur, (2) anal spinous processes straight/recurved, (3) P5 inner spinous process naked/bipinnate, (4) P 6 ♂ with two setae/one seta and one spine, and (5) sixth pair of legs in ♂ forming a common plate/separated opercula. Itô’s (1978) type material of A. (N.) sakagamii lacks the spur on the caudal rami and displays recurved anal processes, a naked spinous process on P5 of both sexes, and separated male sixth legs bearing two setae each.

Wells & Rao (1987) compared their material of N. indicus from the Andaman Islands (Middle Andaman, South Andaman and Little Andaman) and Car Nicobar Island with the types from Vishakhapatnam (= Waltair) and found the same range of variability in both sets of specimens (see their Table 9). As a result of their comparative study, they concluded that the different “setation” of the antennary exopod was the only diagnostic difference separating N. indicus and N. sakagamii , and consequently sank the latter as a junior subjective synonym of the former. However, Mielke’s (1982 b, 1987) detailed studies of the gussoae -“Verwandtschaftskreiss” in Central and South America suggest that the extensive interspecific variability of N. indicus documented so far should be re-evaluated before Wells & Rao’s (1987) conclusions can be accepted. In particular the variability observed in body length and caudal ramus morphology, including the ratio of length of the terminal process to the basal portion of the ramus (1.88– 2.21:1) and degree of curvature of the former, may be indicative for the existence of potentially sympatric cryptic species and calls for examination of a larger number of individuals from Andhra Pradesh and the Andaman Islands. Other sources of variability are the shape and ornamentation of the inner spinous process on P5, the shape of the inner element on the male P6 and curvature of the paired spinous processes on the anal somite. Neoleptastacus indicus differs from other members of the gussoae -subgroup by the relative lengths of the endopodal segments of P1 (enp-1:enp-2 = 1.65 vs 1.25–1.45), the elongate female P5 (length:maximum width 2.7) and caudal ramus process (55% of ramus length) ( Table 4 View TABLE 4 ). The body size given by Rao (1967) is significantly larger than that reported for its congeners in this subgroup ( Table 4 View TABLE 4 ).

Rao (1967) recorded highest densities near half-tide level, with a preference for medium particle size 300–500 μm. Breeding shows a peak in summer and the species appears to feed on detritus, bacteria and diatoms. The egg-sac contains 5– 9 eggs (36–42 μm in diameter) arranged in one or two rows. Rao (1967) described six naupliar and six copepodid stages and noted that development under laboratory conditions was completed in about 25–30 days (the naupliar phase takes about 10–12 days). Sex differentiation is possible from copepodid IV onwards. The serrate setae on P2 enp-2, P4 exp-3 and P4 enp-2 first appear as spindle-shaped elements in copepodid V. The species occurs in very high numbers (> 12,000 ind.10 cm-2) in sandy beaches of the Chennai coast ( Mantha et al. 2012).

In addition to the type locality ( Rao 1967, 1973; Rao & Clausen 1970), the coasts of Odisha (formerly Orissa) (Rao 1970, 1989a; Nagabhushanam 1972; Pati et al. 2009) and Chennai ( Mantha et al. 2012), and Manamelkudi in Palk Bay ( Sugumaran & Padmasai 2019), all located on mainland India, N. indicus has also been recorded from three archipelagos in the Indian Ocean: Lakshadweep (= Laccadive Archipelago), Andaman Islands and Nicobar Islands ( Table 3 View TABLE 3 ). Kazmi & Naushaba (2000) claimed to have found N. indicus in a sandy beach in Karachi, Pakistan. It is impossible to verify this record since it is based on a single copepodid IV (their Fig. 8 View FIGURE 8 ). Silva (2006) recorded A. (N.) indica as one of the three dominant harpacticoid species of Maracaípe beach in Pernambuco State, Brazil, but this record probably refers to another member of the acanthus -group.