Pasiphaea alcocki ( Wood-Mason & Alcock 1891 )

Kuberan, G., Chakraborty, Rekha Devi, Purushothaman, P. & Maheswarudu, G., 2018, Record of the deep sea shrimp Pasiphaea alcocki (Wood-Mason & Alcock, 1891) (Crustacea: Decapoda: Pasiphaeidae) from the southwestern coast of India, Zootaxa 4532 (4), pp. 597-600 : 598-599

Pasiphaea alcocki ( Wood-Mason & Alcock 1891) Fig. 1 (A–G)

Parapasiphae alcocki Wood-Mason & Alcock 1891: 196 (Type locality: Arabian Sea, 1732 m).

Phye alcocki Wood-Mason, 1892 : pl. 3-fig. 5.

Pasiphaea (Phye) Alcocki Wood-Mason & Alcock 1893 ; Alcock & McArdle 1901,pl.52,fig. 6.

Pasiphaea alcocki— De Man 1920, p.6; George & Rao 1966, p. 328; Mohamed & Suseelan 1973, P. 619; 1985: pl. 8- fig 8-

10; Hayashi, 2006a: 197, figs. 1, 2A-P, 3A-E; Komai et al., 2012 (figs. 4, 21B, C).

Material examined: Specimens deposited in the Marine Biodiversity Referral Museum at Central Marine Fisheries Research Institute: Arabian Sea, (ED.8.4.3.1) Sakthikulangara, off Kollam8°56'60.78"N / 76°32'34.27"E, Kerala, India, 200–300 m depth, November 2013, 3 males (CL 20-23 mm) with TL 78 mm.

Diagnosis: Body laterally compressed. Rostrum with postfrontal spine strongly elevated. The carapace of the dorsal midline is most bluntly carinate in the anterior half; branchiostegal tooth sub marginal exceeding well beyond anterolateral margin; antennular peduncle long with a pointed stylocerite reaching anterior margin; 3 rd maxilliped as long as scaphocerite. First to fifth abdominal somite rounded dorsally; the sixth somite bluntly carinate dorsally. Telson shorter than the sixth somite shallowly grooved in dorsal midline; posterior margin deeply forked, each terminal margin with 8-10 spines including prominent one located at a posterolateral angle. 1 st pereiopod overreaching scaphocerite by about half of its chela, its merus armed with 2-3 spines on posterior margin, 2 nd pereiopod slightly longer than 1 st, merus armed with 10-11 spines; carpus of 1 st and 2 nd legs very short, 3 rd to 5 th pereiopods slender; uropod long, subequal, extending beyond telson (modified from Komai et al. 2012).

Coloration: Body almost entirely transparent with some scattered red chromatophores and eyes dark brown.

Remarks: The present specimens agrees with the description provided by ( Alcock & McArdle 1901; Suseelan 1985; Hayashi 2006a; Komai et al. 2012). Pasiphaea alcocki is widely distributed in the Indian Ocean, Bay of Bengal, 922 fathoms: Gulf of Mannar, 406 fathoms: Arabian Sea, off the Sind coast, 947 fathoms: southern region of Cochin, Off Alleppey in 185 fathoms (Alcock 1901; George & Rao 1966; Suseelan 1985). In the present study, the specimen was obtained in the lesser depth range of 200-300 m from the southern region of Quilon bank, off Kollam along the Arabian Sea. Earlier, three species under the genus Pasiphaea named P. sivado ( Risso 1816) , P. unispinosa ( Wood-Mason, 1892) and P. alcocki ( Wood-Mason and Alcock, 1891) are recorded. These species differ from each other in the following characters: carapace not carinate dorsally in P. sivado , merus of 1 st pereiopod unarmed, that of 2 nd pereiopod armed with a single spine on the posterior border in P. unispinosa and merus of 1 st pereiopods armed with 3-4 and 12-14 spines in the 2 nd pereiopod in P. alcocki from Indian Exclusive Economic Zone (EEZ) as described in the earlier records. But in the present material P. alcocki , all three male specimens showed 2-3 spines on the merus of 1 st pereiopod and 10-11 spines on the merus of 2 nd pereiopod ( Fig. 1 , E-F). Moreover, presence of a mid-dorsal carina on the carapace forms an important character of this species particularly in the present male specimens, while ( George & Rao 1966) in a female specimen such carina was not examined ( Suseelan 1985) but however one female specimen with distinct carina extending clearly extends to almost the posterior border of the carapace was reported.

The gene sequences obtained were deposited in GenBank (COI: MG748565 ; 16S DNA: MG748566 ). The nine species of COI and twenty two species of 16S including one intraspecies sequences of P. alcocki are retrieved from NCBI database. COI: P. sivado ( KP759488 & JQ306265 ), P. telacantha ( KP759492 ), P. multidentata ( JQ305978 , FJ581855 & KF931036 ), P. planidorsalis ( KP759483 ), P. sirenkoi ( KP759484 ), P. tarda ( DQ882139 , JQ305981 & AF125439 ), P. merriami ( MF197272 ), P. pacifica ( DQ882135 ) and P. hoplocerca ( JQ306169 ). 16S: P. sivado ( MF279526 & KP725631 ), P. telacantha ( KP725635 ), P. multidentata ( MF279519 ), P. planidorsalis ( KP725624 ), P. levicarinata ( MF279517 & GQ131899 ), P. japonica ( MF279516 ), P. sirenkoi ( MF279525 & KP725625 ), P. merriami ( MF197216 & EU868700 ), P. mclaughlinae ( MF279518 ), P. americana ( MF279511 ), P. acutifrons ( MF279508 ), P. sinensis ( MF279524 ), P. diaphana ( MF279512 ), P. aequus ( MF279509 ), P. falx ( MF279514 ), P. romenskyi ( MF279522 ), P. gelasinus ( MF279515 ), P. scotiae ( MF279523 ), P. orientalis ( MF279520 ), P. pseudacantha ( MF279521 ) and P. exilimanus ( MF279513 ). The level of interspecific divergence was observed for COI and 16S sequence, P. alcocki exhibited high genetic distance range of 18.5% to 27.9% with COI, while with 16S sequences the genetic distance was a comparatively lesser range of 7.4% to 26.4%. Pasiphaea sirenkoi which showed minimum genetic variation (16S: 7.4% & COI: 18.5%) with the present isolate, P. alcocki among all the species retrieved. Morphologically, the present specimen showed 10-11 spines on the merus of the 2 nd pereiopod and P. sirenkoi differed by having 1 spine ( Fig. 1 , C, F). Intraspecies divergence among P. alcocki (16S: MF279510 ) showed a genetic distance of 21.2%.

Figures

FIGURE 1. A. Pasiphaea alcocki Wood-Mason & Alcock, 1891, male specimen (CL: 23 mm); B. lateral view of rostrum; C. lateral view of carapace; D. lateral view of first three abdomens; E. MS-Merus spines, right first pereiopod, F. MS- Merus spines, second right pereiopod; G. Telson tip with marginal spines.