Paralomis spinosissima Birstein & Vinogradov, 1972

Olguín, Nicole, Ocampo, Emiliano H. & Farias, Nahuel, 2015, New record of Paralomis spinosissima Birstein & Vinogradov (Decapoda: Anomura: Lithodidae) from Mar del Plata, Argentina, Zootaxa 3957 (2), pp. 239-242 : 240-241

Paralomis spinosissima Birstein & Vinogradov, 1972

( Figs. 1–2 )

Material examined. Mar del Plata, Argentina, station L42 of the Talud II campaign, 37°59.11’S, 54°41.136’W, Slope II, 877 m, (25.V.2013), R/V Puerto Deseado, 1 male (juvenile) cl = 13.61 mm, cw = 12.63 mm, MACN-In 39716.

Diagnosis. Carapace subpentagonal or pyriform, slightly longer than wider, covered with long conical spines ( Fig. 1 ). Juveniles have mushroom shape tubercles, with spiniform setae surrounding at the apex. Gastric region with a prominent spine. Branchial regions with acute spines. Lateral and posterior surface with small spines. Rostrum acute trispinose, overreaching the ocular peduncle; paired dorsal spines divergent, directed obliquely upwards, slightly shorter than the central, with a small spine between them ( Fig. 2 A). Ocular peduncle with a longest dorsal spine overreaching the cornea; with scattered smaller spines along its length; some spines with several apical setae ( Fig. 2 A, B). Scaphocerite slender, armed with a long central acute spine, two lateral smaller spines and one short inner spine ( Fig. 2 B). Chelipeds and walking legs densely covered with long and acute spines; dorsal margin with prominent spines; ventral margin armed with blunt spines, in juveniles specimens have blunt tubercles with a tuft of long and rigid setae ( Fig. 2 C, D, E).

Distribution. Southeast Atlantic, Scotia Sea, South Georgia Island ( Birstein & Vinogradov 1972), and between the Burwood Bank and the Malvinas Islands ( Macpherson 1988a), and now from Mar del Plata. Depth range: 132 and 877 m.

Remarks. The specimen examined agrees with the description by Birstein & Vinogradov (1972) except for the armature of the scaphocerite, which has two pairs of lateral spines, and in the specimen analyzed here, just one spine on the inner side. However, Macpherson (1988b) noted that in the holotype, the inner side of the scaphocerite has three spines; this character may be variable in juvenile and adult specimens. The variations of this new specimen could be related to its juvenile stage.

The species is distinguished from all other described species of Paralomis by the armature of the carapace, chelipeds and walking legs that are densely covered by acute spines. Eleven species share this character ( Guzmán 2009), but only P. erinacea Macpherson, 1988 , P. sonne Guzmán, 2009 closely resemble P. spinosissima because they are more densely covered with spines than, for instance, P. f or m os a Henderson, 1888 and P. spectabilis Hansen, 1908 . Moreover, these spines are not as long as in P. phryxa Macpherson, 1992 , P. hystrix (de Haan, 1844) and P. hystrixoides Sakai, 1980 .

The differences between P. erinacea and P. spinosissima were discussed by Macpherson (1988b) and are based mainly on the presence of thick spines in the gastric and branchial regions in the latter species. Our specimen is agree with the Macpherson’s observations in the presence of thick spines in the gastric and branchial regions. On the other hand, the rostrum of P. spinosissima differs from P. sonne in the shape and number of the spines; P. sonne bears two pairs of lateral spines and just one in P. spinosissima . Other differences are in the armature of the pereiopods, more densely covered in P. spinosissima than P. sonne ( Guzmán 2009) .

The present specimen from Mar del Plata extends significantly the distribution of the species northwards.

Figures

FIGURE 1. Paralomis spinosissima Birstein & Vinogradov, 1972, male, cl 13.61 mm, dorsal view (MACN-In 39716).

FIGURE 2. Paralomis spinosissima, male, cl 13.61 mm (MACN-In 39716). A, anterior part of the carapace, dorsal view; B, anterior part of the carapace, lateral view; C, right cheliped; D, right cheliped, dorsal view; E, third left walking leg. Scale bar = 1 mm.