Lithodes galapagensis, Hall, Sally & Thatje, Sven, 2009

Hall, Sally & Thatje, Sven, 2009, Four new species of the family Lithodidae (Decapoda: Anomura) from the collections of the National Museum of Natural History, Smithsonian Institution, Zootaxa 2302, pp. 31-47 : 42-45

Lithodes galapagensis n. sp.

( Figs 7 , 8)

Material examined. Galapagos Archipelago: Johnson Sea-Link II Cruise station 3101, Cabo Douglas, Fernandina Island, 00°17’30”S, 091°39’36”W, 17.07. 1998, 648m: male holotype, CL 114 mm; female paratype, CL 84 mm, Seymour Island, 00°21’42”S, 090°15’00”W, 25.07. 1998, 740 m (all USNM 1122586).

Etymology. This species is named after its type locality, the Galapagos Islands.

Description of the holotype. Carapace roughly pyriform in outline ( Fig. 7 d); as wide as long when measured at maximal width of carapace. Dorsal regions well defined; covered uniformly with small spinules more or less acute at apex, without setae ( Fig. 7 b). Gastric region convex and slightly more inflated than branchial and cardiac regions. One pair of slender spines 7 mm in length, emanating from the mid part of this region — level with hepatic spines on lateral margin. Spinules sparse on apex of gastric region and very few around base of prominent spines. Cardiac region depressed and separated from gastric region by smooth, wide, and saddle-shaped groove. Cardiac region depressed anteriorly, and more inflated posteriorly around single pair of long, slender spines in this region. A pair of acute spinules directly anterior to this pair. Triangular cardiac region separated from branchial regions by grooves which converge posteriorly, and then diverge close to the margin to describe posterior of branchial regions. Branchial regions each with single long, slender spine at apex; a few large, acute spinules posteriorly. A pair of conical spines in intestinal region almost on posterior margin.

Exterior orbital spine just surpassing length of eyestalks; anterolateral spine about equal in length or slightly smaller. Hepatic spines slightly inflated at base, with long slender spine reaching 20 mm. Two spines on anterior portion of each branchial lateral margin, and several much smaller, conical spines interspersed between them and on posterolateral margins.

Rostrum with long, straight median projection rising dorsally from surface of carapace and terminating in pair of spines. Mid way along length of median projection emanate a pair of dorsal lateral spines of about the same length as terminal bifurcation. Base of rostrum narrow, without granulation. Ventrally, with long, smooth spine curving gently upward, terminating approximately at level of corneae.

Eyestalks prominent and without granulation, but with crenulation of dorsal edge of the corneal margin (Fig. 8b).

Second segment of antennal peduncle with long slender spine on exterior aspect. Antennal acicle reduced to very small conical process.

Cheliped merus and carpus with several strong spines on terminal border and poorly defined rows of short spines on dorsal, interior and exterior surfaces. Palm with several poorly defined rows of short spines on dorsal border and two rows on exterior surface leading to articulation with movable finger. Fingers 0.4 × total length of right hand, and 0.5 of left hand. Fingers bearing few tufts of short setae.

Walking legs long and slender. Merus of pereiopod 3 about 0.8 × length of carapace, and 0.2 × as high as long. Covered densely with spinules on dorsal/posterior surface, and smooth on ventral surface ( Fig. 7 c). Two or three rows of larger conical spines along length of merus and long spine on terminal border. Carpus of walking legs with spinulation on dorsal surfaces and smooth ventral surfaces, as well as two very long spines at proximal and distal ends of dorsal border. Propodus sparsely covered with irregular rows of spinules. Dactyli of walking legs over half length of merus and equal to length of carpus; very sharp, slender spines on dorsal border to tip; few or no spines on ventral border; no tufts of setae present.

Abdomen of a form typical of Lithodes , with nodules in the medial portion of segments 3–5; separate marginal and lateral plates well-calcified (Fig. 8f). Second abdominal segment with medial and lateral plates fused; marginal plates almost joined or with suture visible. Surface of abdominal plates with several warty tubercles on edges but no spines decorating surface.

Variations. The female paratype of this species is slightly smaller than the male. It differs from the holotype in having less acute spinules on the dorsal surface, and the less prominent spines on the proximal and distal angles of the walking-leg carpi.

Remarks. This species is distinguished from all other members of this genus, except Lithodes wiracocha Haig , from Peru, in that it has carapace and dorsal surface of the walking legs densely covered in spinules. This species differs from L. wiracocha in the following ways:

The spines on the dorsal surface are less dense in L. galapagensis than in L. wiracocha .

The walking legs of L. galapagensis have spinules only on the dorsal and not on the ventral surfaces of

the walking-leg segments, whereas L. wiracocha has densely packed spinules covering the surface of

all segments.

In the holotype, and somewhat on the paratype of L. galapagensis , certain spines on the dorsal surface

and on the walking legs are very long and slender, unlike the stout conical spines in L. wiracocha .

The rostrum of L. galapagensis is very long and slender — similar in this respect to Lithodes

megacantha Macpherson, 1991 from the central Pacific; however, the rostrum of L. wiraconcha is

rather stout in comparison.

There are no acute spinules on the dorsal base of the rostrum in L. galapagensis , whereas spines cover

the proximal part of all of the lateral spines in L. wiracocha .

No spines on the surface of the abdominal plates in L. galapagensis . Instead, plates are covered with

low tubercles.

Other species close to this location include Lithodes panamensis Faxon from Panama and Peru, and Lithodes santolla Macpherson (1988b) , from Patagonia, both of these are readily distinguishable from the present species because of the peculiar spination of Lithodes galapagensis in which a dense coverage of acute spinules are combined with the few very long spines and long rostrum.

FIGURE 8. Lithodes galapagensis n. sp. a–h, male holotype, 114 mm CL (USNM 1122586), Galapagos Archipelago, Cabo Douglas, Fernandina Island, 00°17’30”S, 091°39’36”W, 648 m. (a) left chela, lateral. (b) ocular peduncle, frontal. (c) right chela, lateral. (d) anterior carapace, lateral. (e) second abdominal segment, posterior. (f) abdominal plates. (g) dactylus 3rd walking leg, posterior. (h) rostral spines, dorsal. Scale bar = 10 mm for a, c–h; 1 mm for b.

Figures

FIGURE 7. Lithodes galapagensis n. sp. a – d, male holotype, 114 mm CL (USNM 1122586), Galapagos Archipelago, Cabo Douglas, Fernandina Island, 00 ° 17 ’ 30 ” S, 091 ° 39 ’ 36 ” W, 648 m. (a) carapace, lateral. (b) dorsal carapace spine, lateral. (c) left walking leg 3, posterior. (d) whole organism, dorsal (note damage to carapace on the left branchial region). Scale bar = 10 mm for a, c, d; 1 mm for b.