Gastroptychus perarmatus ( Haig, 1968 )

Hendrickx, Michel E., 2012, Squat lobsters (Crustacea: Decapoda: Galatheoidea and Chirostyloidea) collected during the TALUD XIV cruise in the Gulf of California, Mexico, and rediscovery of Gastroptychus perarmatus (Haig, 1968) in the eastern Pacific, Zootaxa 3418, pp. 28-40 : 30-32

Gastroptychus perarmatus ( Haig, 1968)

( Figs.2 , 3 )

Chirostylus perarmatus Haig, 1968: 272 , figs. 1–3. — Wicksten 1989: 315 (list).

Gastropthychus perarmatus . — Baba 1977: 205. — Baba and Haig 1990: 859 (key). — Baba 2005: 212 (key), 214 (list). — Fierro et al. 2008: 4 (list). — Baba et al. 2008: 23 (list).

Material examined. TALUD XIV, Station 4 (28°10'05"N, 112°31'59"W), 7 Apr 2011, 1 male (CL 38.4 mm), 2 females (CL 20.7 and 34.2 mm), 1 ovigerous female (CL 32.6 mm), and 2 juveniles (CL 14.3 and 15.7 mm), benthic sledge, 435–451 m, rocky bottom (EMU-8919). Same station, 2 males (CL 38.3 and 43.0 mm), and 2 ovigerous females (CL 36.5 and 37.6 mm) (EMU-8920). Same station, 1 male (CL 38.2 mm), and 3 ovigerous females (CL 35.6–41.8 mm) (EMU-8921).

Color. Fresh specimens were examined onboard and color photographs ( Fig. 2 ) of freshly collected individuals allow for a precise color description. Carapace white, tips of large spines orange; rostrum white with blush of orange at about mid-length; antenna and antennula dark orange. Chelipeds and walking legs dark orange, tips of large spines white.

Size and fecundity. Compared to the 10 specimens reported by Haig (1968) in the original description, the sample from the TALUD XIV cruise is larger and includes much larger specimens: largest male, 43.0 mm CL vs. 26 mm for the male holotype; largest female, 41.8 mm vs. 21.2 mm for the paratypes. No ovigerous females were reported by Haig (1968), but our sample includes six females, with CL ranging from 32.6 to 41.8 mm. Number of eggs per individual is as follow: 139 (CL 32.6 mm); 251 (CL 37.6 mm); 87 (CL 36.5 mm; female partly spent); 174 (CL 35.6 mm); 301 (CL 36.9 mm); 259 (CL 41.8 mm). Egg size of largest female: 1.96 mm (average based on 20 measurements).

Ecology. The material of G. perarmatus reported herein was collected in 435–451 m depth, in a relatively cold (6.84 °C) and severely hypoxic (0.21 ml O2/l) environment (Table 1). These 14 specimens were collected incidentally. Indeed, the sampling area was selected based on the assumption that the bottom was muddy. Although the sampling device was recovered safely after the trawl, there were clear signs of damages when examined on deck, and the front section of the collecting net was severely torn. Large and small pieces of rock were found in the net, thus indicating that the equipment had been trawled at least for a period of time on hard bottom. Haig (1968) noted that G. perarmatus was collected from green mud, in 229 m depth. Video footage taken by a Remote Operated Vehicle (ROV) in the Gulf of California ( JASON dive) are currently being studied and show G. perarmatus associated with a gorgonian, probably of the genus Callogorgia ( Fig. 3 ), fixed on a rocky bottom.

Remarks. According to Baba et al. (2008), the genus Gastroptychus contains 21 species: two in the Indian Ocean, five in the Atlantic and 16 in the Pacific. Of the 16 species with records in the Pacific Ocean, only five have been found in the eastern Pacific (west coast of America): G. milneedwardsi (Henderson, 1885) , from the Straits of Magellan, Chile; G. c a v i m u r u s Baba, 1977, from off Ecuador and Peru; G. defensus ( Benedict, 1902) from the Galapagos Islands; G. iaspis Baba & Haig, 1990 , from off British Columbia to western Mexico; and G. perarmatus ( Haig, 1968) , from off California ( Hendrickx & Harvey 1999; Baba et al. 2008). Gastroptychus perarmatus was described from a small series of 10 specimens collected north of Anacapa Island, California, at a depth of 125 fm (ca 230 m) and was never found again until now, although it is a large animal (TL is over 21 cm in the largest male examined).

The material examined herein fits very well with the original description of Haig (1968), including: the presence of many small spines and the position, size and number of large spines on the carapace; the relative size and orientation of the rostrum; the shape of the sternal plates as well as the position and size of the sternal spines; the length of the chelipeds and the proportion of the joints; and the spination of the walkings legs. The carapace of largest specimens is particularly fragile and somewhat flexible. In largest specimens also the postcervical portion of the carapace is more elevated ( Fig. 2 C) than in the holotype illustrated by Haig (1968: fig. 2).

Baba (2005) discussed the affinities among species of Gastroptychus , noting that the genus can be divided into two groups. The first features a pair of third maxillipeds widely separated at their base and the anterior end of the sternal plastron somewhat concave and with a row of spines; the second group has the third maxillipeds closely set and the anterior end of the sternal plastron is medially ridged, sloping, and with a pair of spines behind it. Considering that G. spinifer should be included in the group with gaping third maxilliped (K. Baba, pers. comm. May 2011), there are nine species in the former group and 11 in the latter (including G. perarmatus ) (see Baba 2005). Gastroptychus meridionalis de Melo-Filho & de Melo, 2004, available after K. Baba’s monograph was in print, features a row of spines on the anterior portion of the sternal plate and the bases of the third maxillipeds are widely gapping, thus indicating it belongs to the first group of species as defined by Baba (2005).

Gastroptychus perarmatus was omitted by Schmitt (1921) in his catalogue of Californian marine decapod crustaceans, and by Austin (1985) in his checklist of marine invertebrates of the cold temperate north-eastern Pacific. It was not reported by Martin & Zimmerman (1997) in their survey of the Santa Maria Basin and the Western Santa Barbara Channel, California.

Figures

FIGURE 2. Gastropthychus perarmatus (Haig, 1968), male, TALUD XIV, Station 4 (CLr ca 38 mm) (EMU- 8920). A, dorsal view. B, same, detail of carapace. C, same, lateral view of carapace.

FIGURE 3. Gastropthychus perarmatus (Haig, 1968) on a specimen of the gorgonian Callogorgia sp. JASON dive J 2 - 337, northern Gulf of California, ca 700 m depth.