Mariaplax granulifera ( Campbell & Stephenson, 1970 ), 2014

Rahayu, Dwi Listyo & Ng, Peter K. L., 2014, New genera and new species of Hexapodidae (Crustacea, Brachyura) from the Indo-West Pacific and east Atlantic, Raffles Bulletin of Zoology 62, pp. 396-483 : 438-442

Mariaplax granulifera ( Campbell & Stephenson, 1970)

( Figs. 34–36 )

Hexapus granuliferus Campbell & Stephenson, 1970: 286 (part), fig. 49 (not fig. 49G, H = Mariaplax daviei , new species); Ng et al., 2008: 86.

Hexapus ? granuliferus – Serène & Soh, 1976: 25, fig. 26, pl. 7, fig. C Hexapinus granuliferus – Manning & Holthuis, 1981: 169 (not fig.

32c, d); Davie, 2002: 232.

Material examined. Holotype: female (6.5 × 3.8 mm) (QM- W3108), Red Buoy , Moreton Bay , Queensland, Australia , coll. 24 April 1968 (photographs examined). Others: Australia: 1 male (6.2 × 4.5 mm), 2 females (6.1 × 4.4 mm, 5.9 × 4.4 mm) ( QM-W8299 ), Middle Bank North Moreton Bay, sandy mud, 105 feet, coll. S. Cook, 29 September 1972.

Diagnosis. Carapace subquadrate, about 1.4 times as broad as long; dorsal surface covered by tubercles; regions indistinct ( Figs. 34A , 35A ). Anterolateral margin arcuate; posterolateral corner with angled prominence over base of posterior pereopods ( Figs. 34A , 35A , 36A ). Eye small, slightly movable, cornea globular ( Fig. 34B ). Pterygostomial region with row of long and short, oblique striae and with scattered tubercles ( Figs. 34B , 35C ). Third maxillipeds relatively broad, almost completely covering buccal cavity ( Figs. 34B , 35B, C , 36E ); ischium of third maxillipeds noticeably longer than merus, mesial margin straight; combined length of dactylus, propodus and carpus shorter than that of merus and ischium; exopod relatively narrow, 0.4 width of ischium, flagellum well developed. Chelipeds stout, unequal; major chela ( Fig. 36F ) with gap when fingers closed; dactylus with shallow groove on outer surface, groove present on outer surface of fixed finger distally; palm slightly wider than long, surface with sparse tubercles; minor chela ( Fig. 36G ) with wider gap between closed fingers, dactylus and fixed finger with shallow longitudinal groove medially. P2–P4 relatively long ( Fig. 34A ) merus of P4 2.9 times as long as broad; dactylus of P2 upcurved ( Fig. 36H ). Male thoracic sternum broad ( Figs. 35B , 36B, C ), covered by tubercles; sternites 1 and 2 fused, separated from sternite 3 by distinct ridge; sternite 3 separated from sternite 4 by distinct tuberculate ridge laterally, thoracic sternal groove wide, short, directed anteriorly, extends from sternoabdominal cavity to base of sternite 3 ( Figs. 35C , 36C ); sternite 8 exposed, rectangular, slightly longer than abdominal somite 1; sternoabdominal cavity not reaching base of sternite 3 ( Fig. 36B ). Male abdomen relatively wide ( Figs. 35B , 36D ); somites 1 and 2 free, somites 3–5 fused, wider than somite 6, lateral margin rounded; somite 6 sligthly shorter than length of somites 3–5, lateral margin slightly expanded medially forming blunt triangular projection; telson with distal margin rounded, sparsely setose. G1 ( Fig. 36I, J ) stout, slightly S-shaped, distal part tapered, basal part swollen, row of spines on midlength mesially, sparse short setae laterally and mesially, distal part not concealed under abdomen, exposed on thoracic sternal groove, obscured by setae of telson. Female abdomen with 6 free somites and telson ( Fig. 34C ).

Colour. Not known.

Remarks. The holotype of Hexapus granuliferus is a female from Moreton Bay, Queensland, while the paratypes are one male and one female from Port Jackson, New South Wales. Campbell & Stephenson (1970) described and figured the holotype female (6.5 × 3.8 mm, in the QM) and a paratype male (15.5 × 9.1 mm, in the Australian Museum). Manning & Holthuis (1981) assigned this species to Hexapinus on the basis of the short, oblique male thoracic sternal groove.

Interestingly, when we examined specimens from eastern Australia that had been assigned to H. granuliferus , we found there were in fact two kinds of G1 structures. A male from Moreton Bay (QM-W8299) had a relatively stouter G1 with the inner margin gently serrated medially ( Fig. 36I, J ) while the male from Tasmania (WAM C23270) (which is also in southeastern Australia like Port Jackson) had a more slender G1 with a smooth inner margin ( Fig. 31H, I ). They clearly belong to two separate species. Campbell & Stephenson (1970) stated that the tip of the G1 of the paratype male (their fig. 49G, H) is probably broken, but this is incorrect; the G1 of the present Tasmanian male ( Fig. 31H, I ) is almost identical to that in their figure. Mariaplax granulifera is here restricted for the Moreton Bay material; while the specimens from southeastern Australia (including the paratype of Hexapus granuliferus ) are referred to another species, M. daviei , new species.

Mariaplax granulifera and M. daviei are very close in general appearance of the carapace, but some differences are noticeable: the male sixth abdominal somite of M. granulifera is slightly shorter than the length of somites 3–5, and distinctly longer than telson ( Fig. 36D ) while in M. daviei the somite 6 is distinctly shorter than somite 3–5 and nearly as long as telson ( Fig. 31E ); and the ischium of the third maxilliped of M. granulifera is slightly longer than that of M. daviei ( Fig. 36E versus Fig. 31D ). Furthermore the form of G1 is certainly different, being slightly S shaped in M. granulifera ( Fig. 36I, J ) versus slightly curved in M. daviei ( Fig. 31H, I ). In the form of their third maxillipeds and pereopods, however, both species are clearly referable to Mariaplax .

The “ Hexapus ? granuliferus ” of Serène & Soh (1976) from Queensland, Australia, is assigned to this species because of the shape of the third maxilliped and female abdomen (cf. Serene & Soh, 1976, fig. 26; Fig. 26C ).

Type locality. Red Buoy , Moreton Bay, Australia .

Distribution. Moreton Bay, Australia. Subtidal, 35 m.

Figures

Fig. 34. Mariaplax granulifera (Campbell & Stephenson, 1970), holotype female (6.5 × 3.8 mm) (QM-W3108).A, overall view of carapace and P2–P4; B, frontal view of cephalothorax; C, abdomen and telson.

Fig. 35. Mariaplax granulifera (Campbell & Stephenson, 1970), male (6.2 × 4.5 mm) (QM-W8299). A, dorsal view of carapace; B, ventral view of cephalothorax, showing abdomen and telson; C, anteroventral view of cephalothorax showing third maxillipeds and sternoabdominal cavity.

Fig. 36. Mariaplax granulifera (Campbell &Stephenson, 1970), male (6.2 × 4.5 mm) (QM-W8299). A, dorsolateral margin of carapace; B, thoracic sternites 1–5, showing sternoabdominal cavity and thoracic sternal groove; C, thoracic sternites 1–5, showing thoracic sternal groove and telson; D, male abdomen and telson; E, left third maxilliped; F, major chela; G, minor chela; H, left P4; I, J, G1. Scale bars = 1.0 mm

Fig. 31. Mariaplax daviei, new species. A–I, holotype male (6.0 × 4.5 mm) (WAM C23270); J, paratype female (6.2 × 4.9 mm) (WAM C23270). A, dorso-lateral margin of carapace; B, thoracic sternites 1–5, showing sternoabdominal cavity and thoracic sternal groove; C, thoracic sternites 1–5, showing thoracic sternal groove and telson; D, right third maxilliped; E, male abdomen and telson, F, major chela; G, minor chela; H, I, G1; J, female abdomen and telson. Scale bars = 1.0 mm.

Fig. 26. Mariaplax chenae, new species, paratype male (5.3 × 3.6 mm) (ZRC 2012.1022).A, thoracic sternites 1–5, showing sternoabdominal cavity and thoracic sternal groove; B, thoracic sternites1–5, showing thoracic sternal groove and telson; C, male abdomen and telson; D, left third maxilliped; E, F, G1. Scale bars = 1.0 mm.