Sphaerodromia nux Alcock 1899
Creators: name: Mclay, Colin L.
Publisher: name: Zenodo
Year: 2001
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Dromiidae
Sphaerodromia
Sphaerodromia nux

description: Sphaerodromia nux Alcock, 1899
Sphaerodromia nux Alcock, 1899: 154; 1901: 40, pl. 4, fig. 19. — Ihle 1913: 92 (list). — Lewinsohn 1984: 115, pls 3B, 4C, D. — McLay 1991: 463; 1993: 127.
MATERIAL EXAMINED. — Philippine Islands. Northern Mindanao, Albatross Expedition, stn D 5516, 8°46’N, 123°32.30’E, 321 m, 9.VIII.1909, 1 30.2 × 28.0 mm (USNM).
SIZE. — Maximum size for females 41.7 × 36.0 mm and for males 67.0 × 58.0 mm. Lewinsohn (1984) noted that larger specimens tend to have a higher cw/cl ratio.
DEPTH AND HABITAT. — Type locality is Gulf of Martaban, 128 m. Previously known depth range of 100-150 m, is greatly extended by the Philippine specimen taken from 321 m. Other species of Sphaerodromia also come from deeper water with the maximum depth known being 400-450 m for S. ducoussoi from the Tuamotu Archipelago.
DISTRIBUTION. — Burma, Seychelles, Madagascar and Reunion. The Philippine specimen represents a considerable eastward range extension.
DESCRIPTION
Carapace wider than long, globose, strongly convex, rising steeply above anterior and lateral margins, covered by short velvety tomentum. Branchio-cardiac grooves distinct, joined by faint groove marking anterior cardiac area border to make H-shape pattern. Anterior to pattern are pair of deep pits. Branchial groove represented by line of pits not reaching lateral margin. Otherwise carapace smooth. Rostrum bilobed, lateral teeth blunt, no frontal groove. Supraorbital margin straight, slightly thickened around postorbital margin. Supraorbital tooth absent. No fissure separating supra-and infraorbital margins. Infraorbital margin triangular, not visible dorsally. Sub-hepatic area slightly concave, bearing many small conical tubercles. Anterolateral margin begins beneath suborbital margin, evenly rounded, without teeth but bearing many small conical tubercles. Posterolateral tooth absent, no division of lateral carapace margin into antero- and posterolateral sections.
Epistome triangular, lateral margins distinct. Crista dentata with 15 large uniform teeth.
Pereopods covered with short setae, margins fringed with longer stiff setae, limbs fitting tightly against carapace. Chelipeds well-developed, merus triangular in cross-section, borders bearing small tubercles. Upper margin of carpus carinate, surface granular. Outer face, upper and lower borders of propodus have small tubercles arranged roughly in longitudinal rows. Fingers long, pearly white, cutting margin armed with five blunt, interlocking teeth as well as five small- er proximal teeth which do not meet.
P2-p3 shorter than chelipeds, smooth, laterally compressed, acute distal spine on propodus. Inner margins of dactyli armed with six or seven short spines all of similar size. Dactyli shorter than propodi, ratio= 0.77. P4-p5 similar, but much shorter than p2-p3, last pair slightly longer. Dactyl of p4 opposed by three or four unequal propodal spines, no spines on outer propodal margin, inner margin of dactyl armed with four short spines. Dactyl of p5 opposed by four short propodal spines, none on outer propodal margin, three small spines on inner margin.
Female sutures 7/8 end apart behind p3. Epipods on p1-p4 and podobranchs on p1-p3. Podobranchs decrease in size posteriorly. Abdominal locking mechanism uses serrated ridges on coxae of p2-p3.
Female telson slightly wider than long, male telson longer than wide. No median abdominal ridge. Uropods large, visible externally, occluding one-third of penultimate abdominal segment from lateral margin in male, but two-thirds in female. Five pairs of pleopods in both sexes, first pair uniramous and reduced, rest biramous in female. Second male gonopod has an exopod, third to fifth pleopods vestigial and bifid.
DISCUSSION
The re-description by Lewinsohn (1984) is amended and details of the mature female from the Philippines are added above. The key provid- ed by McLay (1993), to identify the species of Sphaerodromia, is modified herein to include S. lamellata Crosnier, 1994 from New Caledonia. Genus Dromidiopsis Borradaile, 1900 DIAGNOSIS. — Carapace as long as wide or longer than wide, surface smooth. Rostrum tridentate, lateral teeth rounded, not prominent. Coxae of third maxillipeds usually separated by a narrow gap and inserted close to the tip of the sternum. Female sternal sutures 7/8 end on tubercles either apart or together, behind chelipeds. Cheliped with an epipod. Legs not knobbed or ridged. Propodi and dactyli of first two pairs of legs equal in length, inner margins of dactyli armed with five or fewer small spines. Dactyl of third leg opposed by one propodal spine with up to two spines on the outer propodal margin. Fourth leg may be as long as second leg, dactyl opposed by up to two propodal spines, usually one spine on the outer propodal margin and another on the outer margin of the dactyl itself. Uropods usually welldeveloped, visible externally and used in the abdominal locking mechanism by fitting in front of serrated flanges on the bases of the first pair of legs. Last two segments of the abdomen maybe fused or freely movable. First male gonopod a simple semi-rolled tube, sharply tipped and densely setose, second gonopod simple needle-like, no exopod on basis (modified after McLay 1993).
description: Published as part of Mclay, Colin L., 2001, Dynomenidae and Dromiidae (Decapoda, Brachyura) from Guam, Philippine Islands, Tonga and Samoa, pp. 807-856 in Zoosystema 23 (4) on pages 821-822, DOI: 10.5281/zenodo.4689208