Calastacus Faxon, 1893

Ngoc-Ho, Nguyen, 2003, European and Mediterranean Thalassinidea (Crustacea, Decapoda), Zoosystema 25 (3), pp. 439-555 : 457-459

Genus Calastacus Faxon, 1893

TYPE SPECIES. — Calastacus stilirostris Faxon, 1893 , by monotypy.

DIAGNOSIS. — Rostrum slender, pointed at tip, margin unarmed and continuous to gastric region. Anterolateral margin of carapace unarmed. Gastric region convex, fine median dorsal carina present, cervical groove well defined dorsally. Telson longer than wide, lacking dorsal carinae; posterior border rounded, median spine absent.

Eyestalk short, cornea flattened. Antennal acicle prominent, elongated.

P1 slightly unequal, P3 and P5 coxae with gonopore. Hermaphroditic.

Exopod on Mxp1-3; single epipod on Mxp2, Mxp3 and P1-4; single podobranch (rudiment) on Mxp3 and P1-3; rudiment of arthrobranch on Mxp2, paired arthrobranch on Mxp3 and P1-4. No pleurobranch.

Plp1 uniramous, two-segmented, distal segment spatulate, bearing rudiment of appendix interna. Plp2 biramous with small appendix interna and with appendix masculina presumably fused to endopod. Uropodal exopod with transverse suture.

Calastacus laevis de Saint Laurent, 1972 ( Fig. 5 )

Calastacus laevis de Saint Laurent, 1972: 348 , figs 1- 10. — Kensley 1989: 961; 1996: 161. — Sakai & de Saint Laurent 1989: 60. — Noël 1992: 79. — d’Udekem d’Acoz 1999: 152. — ° Türkay 2001: 289.

TYPE MATERIAL. — Holotype: Northern Spain, 43°43.5’N, 4°27’W, hermaphroditic (MNHN Th

152). MATERIAL EXAMINED. — France. Capbreton, south of

Bay of Biscay, 43°37,78’N, 1°43,91’W, NO Côtes de la Manche, CNRS-INSU , stn K, 639-645 m, mud, SEDICAN I Exp., 20. V.2000, 1 spec. damaged cl. 10 mm (Sorbe, personal collection).

Northern Spain. 43°43.5’N, 4°27’W, 950-1000 m, mud, Thalassa Exp. , stn 377, 7.X.1970, 1 spec. cl. 14.5 mm, tl. 39 mm, holotype, right P1, P2 present (MNHN Th 152).

DISTRIBUTION AND ECOLOGY. — Bay of Biscay, SW France, northern Spain, in mud, 639-1000 m.

DIAGNOSIS (from de Saint Laurent 1972) Carapace ( Fig. 5C ) laterally compressed, dorsally rounded; cervical groove weakly defined dorsally, very faint on sides. Rostrum ( Fig. 5B ) slender, lateral margin unarmed, continuous posteriorly to short lateral carina bearing large spine at base. Fine dorsal carina from base of rostrum to cervical groove with faint tubercle near anterior third. Abdominal somites ( Fig. 5A ) unarmed, pleura rounded ventrally, third somite largest; thoracic sternite of P4 with minute spine. Telson ( Fig. 5A ) about 1.5 times as long as wide, unarmed, posterior border rounded.

Eye hardly mobile ( Fig. 5B ) nearly fused to carapace, cornea slightly flattened anteriorly, unpigment- ed. A2 acicle slender, reaching approximately middle of fourth article of A2 peduncle. Mxp2 ( Fig. 5F ) as figured. Mxp3 ( Fig. 5G ) with two lower distal spines on merus.

Right P1 ( Fig. 5D ) long and stout. Merus with five lower spines, larger distally, and upper subdistal spine. Carpus unarmed. Propodus with upper subdistal spine; external surface of palm with spinule behind articulation with dactylus. Fixed finger and dactylus about as long as palm, strongly curved at tip. P2 ( Fig. 5E ) much smaller than P1, unarmed.

Gonopores wide open on coxae of P3 and P5.

Branchial formula (from de Saint Laurent 1972): single epipod on Mxp2, Mxp3 and P1-4; single podobranch (rudiment) on Mxp3 and P1-3; rudiment of arthrobranch on Mxp2, paired arthrobranch on Mxp3 and P1-4.

Plp1 ( Fig. 5H ) of two articles, distal dilated with bunch of minute hooks on mesioproximal border representing vestigial appendix interna. Plp2 ( Fig. 5I ) endopod of two articles with short appendix interna articulated at base of second article, latter more densely setose proximally than on distal half. Plp3-5 ( Fig. 5J ) appendix interna articulating near midlength of endopod.

Uropods ( Fig. 5A ) about as long as telson, lateral border of endopod and exopod with one and two distal spinules respectively; a suture near posterior border of exopod.

Colour

Unknown.

Size

Holotype of cl. 14.5 mm, tl. 39 mm (de Saint Laurent 1972); other material: cl. 10 mm.

REMARKS

De Saint Laurent (1972) reported that the holotype bears numerous setae and remnants of egg envelopes on the pleopods indicating that it was ovigerous shortly before capture.

Figures

FIG. 5. — Calastacus laevis de Saint Laurent, 1972, holotype hermaphroditic from Northern Spain (MNHN Th 152) (figures from de Saint Laurent 1972); A, dorsal view; B, C, anterior part of carapace, dorsal and lateral view; D, E, pereopod 1 and 2; F, G, maxilliped 2 and 3; H-J, pleopod 1-3. Scale bars: 2 mm.