Glyptelasma carinatum ( Hoek, 1883 )

Young, Paulo S., 2001, Deep-sea Cirripedia Thoracica (Crustacea) from the northeastern Atlantic collected by French expeditions, Zoosystema 23 (4), pp. 705-756 : 720-723

Glyptelasma carinatum ( Hoek, 1883)

( Figs 10C, D ; 12 )

Poecilasma carinatum Hoek, 1883: 44 , pl. 1, figs 8-10, pl. 2, fig. 1, pl. 7, figs 6-7. — Weltner 1895: 289; 1897: 243. — Gruvel 1902c: 157, pl. 17, figs 9-16; 1902d: 45, 49; 1905: 115, fig. 130. — Hoek 1907a: 4, pl. 1, fig. 1; 1908: 111; 1914: 4. — Gruvel 1920: 37.

Megalasma (Glyptelasma) carinatum – Pilsbry 1907a: 93; 1907b: 416. — Calman 1918a: 401, figs 1-3; 1919: 370. — Barnard 1924: 54. — Zevina 1972: 61; 1982: 92, fig. 82.

Poecilasma (Glyptelasma) carinatum – Nilsson-Cantell 1921: 258.

Glyptelasma carinatum – Broch 1931: 32, fig. 11. — Southward 1998: 13. — Young 1999: 612, fig. 2a.

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Megalasma carinatum – Ciurea et al. 1933: 14. — Hutchins 1952: 194.

Non Megalasma carinatum – Foster 1978: 26, pl. 3b, fig. 12 (= Glyptelasma hamatum Calman ).

MATERIALEXAMINED. — SEAMOUNT 2, stn TS 267, 34°22.50’N, 30°22.50’W, 2225 m, 1 specimen, tl (cl) 21.2 (20.1) mm (MNHN Ci 2842).

REMARKS

Comparing the description of G. carinatum with that of G. hamatum ( Calman 1918a, 1919), I list some differences in the external characters of the capitular plates as follows. G. hamatum has a scutum with the basal margin straight and forming a right or obtuse angle with the occludent margin whereas G. carinatum has its basal margin form- ing an even curve with the occludent margin. But the specimens of G. carinatum figured by Hoek (1907a) show the basal margin as described for G. hamatum by Calman (1919). Hoek’s figure from specimens taken by the Challenger Expedition ( Hoek 1883) also has a straight basal margin forming an angle with the occludent margin.

Calman (1918a) observed a well-marked umboapical ridge, curved and distant from the occludent margin for G. carinatum and in 1919 he observed a submarginal umbo-carinal ridge, straight or curved for G. hamatum . He noted a relation between the carinal and occludent margins of tergum of one-third to half for G. hamatum and only half for G. carinatum .

Nilsson-Cantell (1928: fig. 11) figured a specimen of G. hamatum with a conspicuous apicobasal ridge and an angle between the occludent and basal margins of the scutum.

Young (1999: 612) also observed an apicobasal ridge on the scutum of G. carinatum which was collected off the Brazilian coast.

Dissecting all the Glyptelasma sampled I found a large number of G. hamatum but only one specimen of G. carinatum . I tried to observe the external characters of these two species to evaluate the differences cited by Calman (1918a, 1919) and others. All the specimens have an angle between the basal and occludent margins of the scutum ( Fig. 10A, C ). The scutum of G. carinatum did not have an apico-basal ridge, but rather a wellmarked lateral ( Fig. 10A, C ). Therefore the development of an apicobasal ridge on the scutum is variable in both species. The relationship of half between the carinal and occludent margins of the tergum of G. carinatum may change if more specimens are examined. I cannot observe any external character which could be used to separate these species.

Certainly, the best character to separate both species is the number of filamentary appendages on the dorsal margin of the prosoma: G. carinatum has two rows of numerous fine and long filamentary appendages and G. hamatum has only two short projections, which Calman (1919: 372) named dorsal hooks ( Fig. 10B, D ).

G. carinatum and G. hamatum were collected at the same station on the axes of gorgonians.

The general distribution of both species of Glyptelasma are similar: mainly North Atlantic and Indo- Malayan. Glyptelasma hamatum is also found from East Africa, south to Australia and New Zealand ( Fig. 11 ) and G. carinatum from the South Atlantic, Japan and near the Galapagos Island ( Fig. 12 ).

Figures

FIG. 10. — A, B, Glyptelasma hamatum (Calman, 1919), SEAMOUNT 2, stn DW 267; A, left lateral view; B, dorsal filamentary appendage on prosoma; C, D, Glyptelasma carinatum (Hoek, 1883), SEAMOUNT 2, stn DW 267; C, left lateral view; D, dorsal filamentary appendages on prosoma. Scale bars: A, C, 5 mm; B, D, 2 mm.

FIG. 12. — Geographic distribution of Glyptelasma carinatum (Hoek, 1883).

FIG. 11. — Geographic distribution of Glyptelasma hamatum (Calman, 1919).