Afropinnotheres Manning, 1993

Ng, Peter K. L. & Kumar, Appukuttannair Biju, 2015, A new species of Afropinnotheres Manning, 1993 (Crustacea, Brachyura, Pinnotheridae) from southwestern India, the first record of the genus from the Indian Ocean, with a review of the Pinnotheridae of India and adjacent seas, Zootaxa 3947 (2), pp. 264-274 : 265-266

Genus Afropinnotheres Manning, 1993

Afropinnotheres Manning, 1993: 130 .

Remarks. Manning (1993) substantially changed the generic system for the species placed in Pinnotheres Bosc, 1802 , differentiating genera mainly on the basis of the structure of the MXP3 (notably the structure of the dactylus and its point of articulation with the propodus) and the proportions of their P2–P5 (notably the dactylus). Using these and characters of the carapace in some instances, over a dozen genera are now recognised (see Ng et al. 2008).

In reviewing the generic status of many of the Atlantic species, Manning (1993) established a new genus, Afropinnotheres , for species that share the following characters: a rounded to subovate carapace, the propodus of the P2–P5 are laterally flattened and appear expanded; the P2–P5 dactyli are subequal; propodus of the MXP3 is distinctly coniform and is shorter than the carpus; dactylus of the third MXP3 is elongated, extending beyond the tip of the propodus and articulates near the base of the propodus; all the male abdominal somites are free; and the male first gonopod is simple and slender. Afropinnotheres is similar to Pinnotheres Bosc, 1802 s. str., and Nepinnotheres Manning, 1993 , but in these genera, the propodus of the MXP3 is distinctly more elongated (much longer than the carpus), with the dactylus either long, reaching to or over-reaching the tip of the propodus and inserted at or near the middle or the proximal third of the propodus ( Nepinnotheres ), or the MXP3 is shorter, not reaching the tip of the propodus and inserted near the base of the propodus ( Pinnotheres s. str.). Another character shared by all Afropinnotheres species is the proportionately slender male abdomen. The known male abdomens of Pinnotheres and Nepinnotheres are proportionately broader, with the first few somites much wider, giving the structure a more triangular appearance (see Ahyong & Ng 2007).

Four species of Afropinnotheres have been described, all from western Africa: A. crosnieri Manning, 1993 ( Congo; type species); A. guinotae Manning, 1993 ( Angola) ; A. larissae (Machkevskiy, 1992) ( Senegal, Guinea, Ivory Coast); and A. monodi Manning, 1993 ( Morocco, Mauritania).

Ng & Manning (2003) subsequently transferred a number of species of holothurian-dwelling Pinnotheres to a new genus, Holotheres , members of which share carapace and ambulatory leg characteristics with Afropinnotheres . In addition to their host preference (all Afropinnotheres are from bivalves), however, Holotheres can be separated by the elongated propodus of the MXP3 (much longer than the carpus) and a more distinctly spatulate dactylus which is as long as or longer than the propodus; the male abdomen is more triangular in shape and the G1 is gently sinuous (cf. Ng & Manning 2003: fig. 1B, H, I).

Afropinnotheres also closely resembles species of Pinnaxodes Heller, 1865 , with regard to the carapace shape and symmetrical P2–P5. The MXP3 of Pinnaxodes is superficially similar to that of Afropinnotheres except that the propodus is elongated and much longer than the carpus (rather than short and conical in Afropinnotheres ) and the more spatuliform dactylus is inserted on the proximal one-third or middle of the propodus (cf. Garth 1958: figs. 10D, 11B; Wells & Wells 1961: fig. 2F, G; Campos et al. 1998: fig. 2B, D; Takeda & Prince Masahito 2000: figs. 2C, E, G, 4C; Ng & Manning 1993: figs. 6B, F, 7A, B; De Melo & Boehs 2014: fig. 4). The male abdomen of Pinnaxodes species is also relatively wider and more triangular in shape and the telson may be expanded such that it is wider than somite 6 (cf. Garth 1958: fig. 11A; Wells & Wells 1961: fig. 1F; Campos et al. 1998: fig. 3A, C; Takeda & Prince Masahito 2000: figs. 4B, 5L; De Melo & Boehs 2014: fig. 6).

There has been some discussion about the taxonomy of Pinnaxodes Heller, 1865 , and Holothuriophilus Nauck, 1880 . Although Takeda & Prince Masahito’s (2000) suggestions on these genera were provisional, De Melo & Boehs (2004) followed their arguments for transferring the Japanese Pinnaxodes mutuensis Sakai, 1939 , to Holothuriophilus and placed the South American P. tomentosus Ortmann, 1894 , there as well. Ng & Manning (2003) showed that Pinnaxodes and Holothuriophilus are easily separated by the carapace shape (ovate in Pinnaxodes , transversely subrectangular in Holothuriophilus ) and form of the MXP3 (i.e. presence of a faint suture separating the ischium and merus in Pinnaxodes ; completely fused ischium and merus in Holothuriophilus ) (see also Ahyong & Ng 2007; Campos et al. 2012); and retained P. mutuensis in Pinnaxodes . Six species are now recognised in Pinnaxodes : P. chilensis (H. Milne Edwards, 1837) (= Pinnaxodes hirtipes Heller, 1865 ) [ Chile to Per]; P. f l o r i d e ns i s Wells & Wells, 1961 [Florida, USA]; P. gigas Green, 1992 [Sonora, Mexico]; P. m a j o r Ortmann, 1894 [ Japan and northeastern Russia]; P. m ut uensis Sakai, 1939 [ Japan and northeastern Russia]; P. tomentosus Ortmann, 1894 [ Brazil] (Ng et al. 2008).

The matter of fusion between the MXP3 ischium and merus requires discussion. Of the many genera associated with Pinnotheres s. lato in the past, only Pinnaxodes Heller, 1865 , has these two structures separated by a suture, faint or otherwise (see Manning 1993: 128). Takeda & Prince Masahito (2000) noted that while it is present, they regard it as a less important character since it is not always apparent and can be hard to see. Ng & Manning (2003) noted that it was always present but may be shallow, with the suture more pronounced on the inner surface of the MXP3 and best observed under transmitted light. All known species of Pinnaxodes possess this suture. The present new species from India, Afropinnotheres ratnakara n. sp., also has a trace of this suture. There is a faint suture visible under transmitted light between the merus and ischium in the larger female specimens ( Fig. 2 D), but it is not distinct even on the inner surface of the structure unlike Pinnaxodes . This suture is even less distinct in the smaller males ( Fig. 3 B) and may be absent. Manning (1993) did not report any trace of a suture for the four African species of Afropinnotheres he studied, but he may have overlooked this feature; the MXP3 of the African Afropinnotheres require restudy.

The discovery of the present new species from India is noteworthy because all other Afropinnotheres species have previously been reported from the eastern Atlantic ( Manning 1993). The characters of Afropinnotheres ratnakara n. sp., however, are distinct for the genus. As discussed earlier, there are affiliations with Pinnaxodes as well, but this genus is also not known from the Indian Ocean. While it is possible that the presence of the new species in India is a consequence of introduction from the Atlantic, the fact remains that it may be the same species as specimens of Pinnotheres sp. reported by Doflein (1904) and Tirmizi & Ghani (1996) from South Africa and Pakistan, respectively (see species discussion), many years earlier. Another possibility of course is that the host Perna perna may have been introduced from Africa to India decades or even centuries ago with the crab. This mussel has a rather disjunct distribution, occurring in East and South Africa as well as southwestern India; and the Perna in India may have come from South Africa, especially since Doflein’s (1904) Pinnotheres sp. is probably conspecific with Afropinnotheres ratnakara n. sp. In any case, the current evidence suggests that Afropinnotheres is naturally present in the western Indian Ocean.

Figures

FIGURE 2. Afropinnotheres ratnakara n. sp. A, C – E, holotype female (8.89 × 8.10 mm) (ZSI / WGRC / IR / INV. 4148); B, paratype female (8.61 × 7.27 mm) (DABFUK / ZRC). A, overall habitus; B, epistome, antennae, antennules and orbit; C, left MXP 3; D, outer view of left chela; E, female abdominal somites 5, 6 and telson. Scales = 1.0 mm.

FIGURE 3. Afropinnotheres ratnakara n. sp., paratype male (5.69 × 5.23 mm) (DABFUK / ZRC). A, dorsal view of carapace; B, left MXP 3 (setae not drawn); C, anterior thoracic sternum and sternoabdominal cavity; D, male abdomen; E, right G 1; F, right G 2; G, outer view of left chela. Scales: A – D = 1.0 mm; E, F = 0.5 mm.