Gandoa brevipes (H. Milne Edwards, 1853)

Ng, Peter K. L. & Rahayu, Dwi Listyo, 2016, On the genera Selwynia Borradaile, 1903, and Gandoa Kammerer, 2006, with descriptions of two new species from Papua New Guinea and French Polynesia (Crustacea: Decapoda: Brachyura: Aphanodactylidae), Zootaxa 4092 (3), pp. 339-370 : 365-369

Gandoa brevipes (H. Milne Edwards, 1853)

( Figs. 17–20 )

Pinnixa brevipes H. Milne Edwards, 1853: 220 ; A. Milne-Edwards 1873: 320; Tesch 1918: 284 (footnote); Schmitt et al. 1973: 103.

Voeltzkowia zanzibarensis Lenz, 1905: 364 , pl. 47, fig. 9; Schmitt et al. 1973: 135; Ng et al. 2008: 247.

Aphanodactylus brevipes —Serène 1964: 277, 278; Ng et al. 2008: 247.

Gandoa zanzibarensis —Kammerer 2006: 270; Ahyong & Ng 2009: 38.

Gandoa brevipes —Ng & Naruse 2009: 288, figs. 6, 7.

Material examined. Lectotype: ovigerous female (7.6 × 5.3 mm, carapace soft) (MNHN B-10616), Mayotte, coll. Cloué. Others: 1 female (7.2 × 5.0 mm) (ZSM 1277/1) [holotype of Voeltzkowia zanzibarensis Lenz, 1905 ], Kokotoni, Zanzibar, coll. July 1889.

Redescription (female lectotype). Carapace ( Fig. 17 A) oval, about 1.4 broader than long; dorsal surface smooth, region poorly demarcated. Front ( Figs. 17 A, B) deflexed, medially concave in dorsal view. Orbit ( Figs. 17 D, 18B) transverse; margins entire, unarmed; lateral margin of supraorbital forming triangular groove joining lateral margin of carapace; inner edge of each supraorbital margin continuing on dorsal surface of carapace between epi-, protogastric regions, forming distinct groove. Ocular peduncles ( Figs. 17 A, B, 18B) short, movable. Anterolateral margin ( Fig. 17 A, B) entire, convex laterally, not cristate, continuous with posterolateral margin. Antennule ( Figs. 17 D) folding slightly obliquely. Epistome ( Fig. 17 D) short, medially triangular partially sunken.

Third maxillipeds ( Fig. 18 A) covering approximately half of buccal cavern when closed; ischium subquadrate, longer, broader than merus; merus rounded; palp attached to distolateral angle of merus; exopod relatively stout, reaching proximal half of merus.

Thoracic sternites 1, 2 completely fused, broadly angular anteriorly; sternites 2/3 demarcated by shallow groove; sternites 3/4 fused, laterally unarmed; sternites 4–8 in poor condition.

Chelipeds ( Figs. 17 A, D, 18C) short, equal; surfaces distinctly punctate; merus, carpus short, unarmed, with plumose setae. Merus triangular in cross section, dorsal, ventral margins setose. Carpus smooth, inner angle absent. Outer surface of chela ( Figs. 17 D, E, 18C), notably area at bases of fingers, covered with short, stiff setae, palm about as long as dactylus; outer proximal surface of immovable finger densely pubescent, with weakly sinuous cutting edge, cutting edge convex medially, lined with small teeth; movable finger with cutting edge concave on distal half.

Ambulatory legs (P2–P5) ( Figs. 17 A, 18D–F) short; P2–5 similar in shape, P3 longest, P5 shortest; extensor margin glabrous, short stiff setae on flexor margins, surfaces of propodus, short stiff setae on flexor margin of carpus, merus. Merus as long as or slightly longer than combined length of respective propodus, dactylus, extensor margin unarmed, flexor margin armature of P2–P5 as follows: P2 0+0/-, P3 1+0/1+0, P4 1+0/1+0, P5 1+0/1+0. Flexor margin of basis-ischium of P5 unarmed. Dactylus very short, claw-like.

Abdomen ( Fig. 17 C) with telson, all somites freely articulating, widest at somite 4. Vulva ovate, maximum width not exceeding half width of sternite 6.

Colour. Unknown.

Remarks. The holotype of Voeltzkowia zanzibarensis is in good condition and agrees with the holotype of Pinnixa brevipes in the proportions and characters of the carapace ( Figs. 19 A, 20A), front ( Figs. 19 A, 20A), orbit ( Figs. 19 A, B, 20A, B, D), eyes ( Figs. 19 A, B, 20A, B, D), antennule ( Figs. 19 B, 20B), epistome ( Figs. 19 B, 20B), chelipeds ( Fig. 19 D), abdomen ( Fig. 20 H), and vulva ( Fig. 19 C). The structures of the third maxillipeds ( Fig. 20 C) are also very similar although the exopod flagellum is missing on both sides (probably broken off). The form of thoracic sternites 1–4 is the same, and its sternites 4–8 are demarcated by narrow grooves, with those separating sternites 4–7 incomplete medially and without a longitudinal median groove. The characters of the thoracic sternites 4–7 are not easily discernible on the poorly preserved lectotype of P. brevipes . The ambulatory legs have the same proportions and armature ( Figs. 19 A, 20A, E–G).

Distribution. Known only from Zanzibar and Mayotte, western Indian Ocean.

Biology. It is not known which hosts the two specimens were collected from but considering the habits of aphanodactylids, they were probably obtained from a polychaete worm.

Figures

FIGURE 17. Selwynia brevipes (H. Milne Edwards, 1853), ovigerous female lectotype (7.6 × 5.3 mm, carapace soft) (MNHN B- 10616), Mayotte. A, overall habitus; B, frontal regions of carapace; C, ventral view of cephalothorax; D, frontal view of cephalothorax; E, outer view of left chela.

FIGURE 18. Selwynia brevipes (H. Milne Edwards, 1853), ovigerous female lectotype (7.6 × 5.3 mm, carapace soft) (MNHN B- 10616), Mayotte. A, right third maxilliped; B, right orbit and eye; C, right chela; D, right P 3; E, left P 4; F, left P 5. Scale: A, B = 0.5 mm; C – F = 1.0 mm.

FIGURE 19. Gandoa zanzibarensis (Lenz, 1905), female holotype (7.2 × 5.0 mm) (ZSM 1277 / 1), Zanzibar. A, overall habitus; B, frontal view of cephalothorax; C, ventral view of cephalothorax showing sternum and vulvae; D, outer view of left cheliped.

FIGURE 20. Gandoa zanzibarensis (Lenz, 1905), female holotype (7.2 × 5.0 mm) (ZSM 1277 / 1), Zanzibar. A, overall habitus; B, frontal view of cephalothorax; C, left third maxilliped; D, right orbit and eye; E, right P 2; F, right P 3; G, left P 5; H, abdomen. Scales = 1.0 mm. A, B, G after Lenz, 1905: pl. 47, fig. 9.