Neocallichirus darwinensis Sakai, 1988

Poore, Gary C. B., 2023, New records and one new species of Callichiridae (Crustacea, Axiidea) from the Indo-West Pacific, with keys to species of Corallianassa, Lepidophthalmus and Neocallichirus, Memoirs of Museum Victoria (Mem. Mus. Vic.) 82, pp. 71-95 : 85

Neocallichirus darwinensis Sakai, 1988

Figure 9a, b

Neocallichirus darwinensis Sakai, 1988: 62–65 , figs 5, 6.— Sakai, 2011: 455 (synonymy).

Neocallichirus caechabitator Sakai, 1988: 67–68 , figs 9, 10.— Sakai, 1999: 96.— Davie, 2002: 461.— Sakai, 2011: 454–455 (type locality, Australia, NT, Darwin). Syn. nov.

Material examined. Australia, NT, Mindi Beach , NTMAG Cr000090 (holotype female, 24 mm) .

Diagnosis. Antenna peduncle exceeding antennule peduncle by all of article 5. Cornea reduced to small pigmented area; eyestalk distal lobes truncate, with distolateral sharp corner. Uropodal endopod posterior margin moderately oblique, angle with anterior margin about 30°. Telson clearly tapering from subproximal width to rounded corner between well-defined posterolateral margin and convex-straight posterior margin. Maximum cl. 24 mm.

Distribution. Sahul Shelf ( Australia, NT [type locality: Darwin]).

Remarks. Neocallichirus darwinensis Sakai, 1988 was taken in the same region as N. caechabitator Sakai, 1988 , and N. horneri Sakai, 1988 , type species of the genus. The female holotype, the only specimen known, lacks the major cheliped, and is 2.7 times as long as the type and only specimen of N. caechabitator (24 mm vs 9 mm). Both specimens are unusual in having reduced cornea; they have almost identical maxilliped 3, pereopod 3 and telson. The minor cheliped of N. caechabitator is narrower than that of N. darwinensis , but this may be a sex-related difference. Sakai (1988) stated the holotype of N. caechabitator is an immature female but figured immature male pleopods 1 and 2. The minor cheliped of males is narrower than that of females in N. grandimana ( Gibbes, 1850) ( Felder and Manning, 1995; Ayón-Parente et al., 2014) and in N. mericeae ( Manning and Felder, 1995) , and is narrow in juveniles, e.g. N. sulfureus ( Lemaitre and Felder, 1996) . This may be true for all species of Neocallichirus , but both sexes and a wide size range have been illustrated for few species. Neocallichirus caechabitator is here synonymised with N. darwinensis .

Neocallichirus darwinensis is also twice as long as the types of N.horneri . Neocallichirus horneri has a fully developed cornea but some differences between the two species noted by Sakai (1988) may also be size-related. The antenna is relatively longer than the antennule in N. darwinensis than it is in N. horneri , and the propodus and dactylus of N. darwinensis are narrower than those of N. horneri (cf. fig. 9b, d). The uropodal endopod exopod of N. darwinensis is almost semicircular, whereas that of N. horneri is fan-shaped (cf. fig. 9a, c). Some of these differences fall within the variability seen in other species of Neocallichirus ( Dworschak, 2008, 2011a, 2011b, 2018) but without more specimens the synonymy of these species is uncertain. All species are known only from type specimens.