Pinnotheroidea, De Haan, 1833 [in De Haan, 1833-, 1850

GUINOT, DANIÈLE, TAVARES, MARCOS & CASTRO, PETER, 2013, Significance of the sexual openings and supplementary structures on the phylogeny of brachyuran crabs (Crustacea, Decapoda, Brachyura), with new nomina for higher-ranked podotreme taxa, Zootaxa 3665 (1), pp. 1-414 : 134

Superfamily Pinnotheroidea

The male gonopore opens on the sternum ( Figs. 33B, C , 58C, D ). Although very poorly documented, even unknown, in the various taxa of the group, the male gonopore is located rather far from the P5 coxa and close to or variously distant from suture 7/ 8 in pinnotherids, e.g., Ostracotheres tridacnae , Pinnotheres pisum ( Guinot 1979a: 212, figs. 24D, 53G), Pinnixa transversalis , and in aphanodactylids, e.g., Aphanodactylus loimiae , Gustavus mecognathus (see Ahyong & Ng 2009a: figs. 1F, G, 4I) and Uruma ourana (see Naruse, Fujita & Ng 2009: 60, 66, fig. 2c), however apparently adjacent to suture 7/ 8 in Aphanodactylus panglao (see Ng & Naruse 2009: fig. 3c). It was described “with medially directed roof” in Pinnixa lata Komatsu & Takeda, 2009 ( Komatsu & Takeda 2009: 202). The male thoracic sternum is only exceptionally described among the more than 300 pinnotherid species, thus cannot be used in higher taxonomic ranks. The sternal plate seems to vary from moderately wide ( Fig. 33B ) to widened ( Ahyong & Ng 2009a: figs. 1F, 2C, 4I, 5I), with all the sutures interrupted. The sternite 3 is hypertrophied in the typical taxa with highly modified mxp3 (see e.g., Parapinnixa glasselli Garth, 1939 , see Garth 1939: pl. 9, fig. 2) as well as in the family Aphanodactylidae , which, however, lacks this chief synapomorphy of Pinnotheroidea ( Ahyong & Ng 2009a: 33, fig. 1F; Naruse & & Maenosono 2012: fig. 1b). The disposition of sternites 1, 2 needs to be studied in Pinnotheroidea . The P5 may be substantially reduced in Pinnotheridae , e.g., in Pinnixa White, 1846 ( Wicksten 2012: figs. 58, 59) and in some Aphanodactylidae ( Ahyong & Ng 2009a: figs. 4A, H, 5A, H, 7; Naruse & Maenosono 2012: fig. 1a, c, d).

The Pinnotheridae , raised to suprafamilial status ( Ng, Guinot & Davie 2008: 247), traditionally seen as Catometopa and a thoracotreme family (e.g., Guinot 1978a; Števčić 1998; Martin & Davis 2001; Ng, Guinot & Davie 2008), was interpreted as having a coxo-sternal condition and thus assigned to Heterotremata by Guinot & Richer de Forges (1997: 496, table 1) and Guinot & Bouchard (1998: 654). According to Schubart (in Martin & Davis 2001: 55), Schubart, Neigel & Felder (2000a: 826, 827, fig. 1), and Wetzer et al. (2009: 486, fig. 1, as Pinnotheridae ) the traditional thoracotreme condition of Pinnotheroidea was evident from DNA sequencing. The larval data, on the contrary, appears to show a close relationship with Leucosiidae ( Lebour 1928b; Gurney 1938, 1942) and with the Hymenosomatidae ( Aikawa 1937; Gurney 1938; Wear 1967, 1968; Lucas 1971; Wear & Fielder 1985) so that according to Rice (1980: 347) it seemed inconceivable that the similarities between them “could have evolved independently” (see discussion by Clark & Ng, 2010, about the actually superficial similarity of larvae in small crabs, as in the case of the first zoea of Domecia glabra Alcock, 1899 , which is similar to that of Pinnotheridae ). The alternative possibility, that of a possible close ancestor shared with Hymenosomatoidea as has been suggested by Gurney (1942), Scotto & Gore (1981) and Rice (1980), but finally discounted by Rice (1983), is discussed here (see Monophyletic Thoracotremata; Position of the Cryptochiroidea and Pinnotheroidea within the Brachyura ). The gills of Pinnotheridae were considered close to those of Hymensomatidae ( Claus 1886).

A monophyletic Pinnotheroidea is not supported by adult morphology (e.g., Campos 1996), and study of combined sequence data has demonstrated its polyphyly ( Palacios-Theil et al. 2009, as Pinnotheridae ). The suite of characters introduced by Bürger (1895), then traditionally used by taxonomists ( Ahyong & Ng 2007a, b), do not include the thoracic sternum of the rarely collected males. Uncertainties remain about the phylogenetic relationships of the group with other Brachyura despite numerous taxonomic studies (e.g., Marques & Pohle 1995, 1996a, b; Pohle & Marques 1998 a, b; Ng & Manning 2003; Bolaños et al. 2004, 2005; George & Boone 2003; Ahyong & Brown 2003a; Ahyong & Ng 2005, 2007a, b, 2009a; Thoma et al. 2009; Komatsu & Ohtsuk 2009; Campos 2009; Becker & Türkay 2010; Ocampo et al. 2010; Campos & Hernández-Ávila 2010; Ahyong 2010).

Figures

FIGURE 33. Thoracotreme disposition. A, Plagusia squamosa (Herbst, 1790) (Plagusiidae), male cw 55.0 mm (dissected), French Polynesia (MNHN-B8889): trajectory of vas deferens directly connecting gonad to sternal gonopore. B, Ostracotheres tridacnae (Rüppell, 1830) (Pinnotheroidea), male, 9.0 × 8.6 mm, Egypt, Suez (MNHN-B10578): thoracic sternum; C, Pinnotheres pisum (Linnaeus, 1767) (Pinnotheroidea), male 4.7 × 4.6 mm, Bay of Biscay, La Rochelle (MNHN-B10604): male gonopore (B, C, after Guinot 1979a: figs. 24D, 53G respectively). cx5, P5 coxa; g, sternal gonopore; j, lateral extension of sternite 4 resulting in incomplete thoracic sternum/pterygostome junction; m.l., median line; mxp3, external maxillipeds; p, penis; t, telson; v.d., vas deferens; 3–8, thoracic sternites 3–8; 4/5–7/8, thoracic sternal sutures 4/5–7/8. Scale bar: 1 mm (A).

FIGURE 58. Male reproductive system in Hymenosomatoidea (A, B, E), Pinnotheroidea (C, D), and male gonopores in Cryptochiroidea (F). A, B, dissection of Odiomaris pilosus (A. Milne-Edwards, 1873), male 11.0 × 14.0 mm, New Caledonia, Wé Waalu River (MNHN-B32604): ejaculatory duct and penis (highlighted in B); C, D, dissection of Dissodactylus crinitichelis Moreira, 1901, male 4.6 × 7.0 mm, Brazil (MZUSP 24231): ejaculatory duct (highlighted in D). E, testis and vas deferens as seen through the transparent carapace of Trigonoplax unguiformis (De Haan, 1839), male 6.1 × 7.3 mm, Western Australia (USNM 184973); F, Utinomiella dimorpha (Henderson, 1906): male gonopores perforating sternite 8 far from suture 7/8 (modified from Henderson 1906: pl. 8, fig. 8, as Cryptochirus dimorphus). cx1, cx5, P1, P5 coxae; e.d., ejaculatory duct; g, gonopore; p, penis; t, testis; 4–8, thoracic sternites 4–8; 4/5–7/8, interrupted thoracic sternal sutures 4/5–7/8. Scale bars: 1 mm (A, B); 4 mm (C, D).