Dromia, sensu McLay, 1993

Guinot, Danièle & Quenette, Gwenaël, 2005, The spermatheca in podotreme crabs (Crustacea, Decapoda, Brachyura, Podotremata) and its phylogenetic implications, Zoosystema 27 (2), pp. 267-342 : 287-288

[ Dromia ] dormia (Linnaeus, 1763)

Female, 107 mm carapace length, New Caledonia, Tabu Recif, Laboute coll. (MNHN-B 26439). A new genus to be erected (Guinot unpubl. data).

The very long female sternal sutures 7/8 (total length about 50 mm) converge gradually but diverge slightly near the end at the level of the chelipeds. They end together in the middle of sternite 4, being only separated by a smooth ridge. Each suture 7/8 opens in a pit, which is ovate (length about 10 mm) and unperforated, with very thin external and internal edges, not so calcified as the median part, which corresponds internally to the spermathecal tube (Guinot unpubl. data). The pit corresponds to the level where phragma 7/8 rises to the surface ( Figs 8A ; 9 ). As a result, the spermatheca is devoid of the terminal circular aperture found in the species of Dromia . The whole sternal part that bears these pits slopes backwards and upwards at an angle of about 45°, while the anterior part of the sternite 4 is horizontal. Since only extremely large individuals of [ Dromia ] dormia were examined, there is some doubt about the structure shown by small sized adult individuals (Guinot unpubl. data).

The bulb of the spermatheca ( Fig. 8B ) is elongated, not very globular, and shows a raised part that forms a flat area in the posterior corner; it bears a small anterior prominence. The inner wall of the chamber has a soft inferior part, while the superior one is more rigid. The remains of sperm are visible inside the chamber. The basal thickening is marked. The tube is long (as long as the suture 7/8 which is about 50 mm length), thick, and its extremity raises progressively, with two weakly calcified zones on each side at the level of the external pit ( Fig. 9 ). The tube is not perforated at its end but is opened in its terminal length, the phragma 7/8 itself becoming exposed and constituting the aperture of the spermatheca.

Figures

FIG. 8. — [Dromia] dormia (Linnaeus, 1763), female 107 mm carapace length, New Caledonia (MNHN-B 26439); A, thoracic sternum; B, detailed part view of spermatheca, skeletal parts removed. Abbreviations: b, bulb; b.t., basal thickening; c1, soft part of spermathecal chamber; c2, rigid part of spermathecal chamber; cx3, P3 coxa; e4, e5, episternites 4, 5; g, female gonopore; p, pit; r, ridge between the two pits; 4-8, sternites 4-8; 4/5-7/8, thoracic sternal sutures 4/5 to 7/8. Scale bar: A, 1 cm.

FIG. 9. — [Dromia] dormia (Linnaeus, 1763), female 88 × 105.8 mm, New Caledonia (MNHN-B 26438); A, anterior part of thoracic sternum (see Fig. 8A), showing terminal part of sutures 7/8 forming two pits; B, detailed view of pits; C, schematic section at level of the pits. Abbreviations: cx1, P1 coxa; e4, episternite 4; l, weakly calcified lateral parts of the pits; p, pit; r, ridge between the two pits; t, location of spermathecal tube; 4, sternite 4; 7/8, thoracic sternal suture 7/8. Scale bars: 5 mm.