Poupinia hirsuta Guinot, 1991

Guinot, Danièle & Quenette, Gwenaël, 2005, The spermatheca in podotreme crabs (Crustacea, Decapoda, Brachyura, Podotremata) and its phylogenetic implications, Zoosystema 27 (2), pp. 267-342 : 304-308

Poupinia hirsuta Guinot, 1991

Female 54 × 41 mm, allotype, French Polynesia, Raiatea (MNHN-B 24346).

It was possible to observe partly the skeleton and the spermatheca of this female without immersion in a bath of potassium hydroxyde. Its carapace was partly detached from the rest of the body, and the spermatheca was visible only on one side. The thoracic sternum ( Fig. 20 ) is relatively wide, medially with a large, flat, and translucid horizontal area. All sutures are lateral, except for suture 6/7, which forms a transverse ridge throughout most of its course, but bends sharply backwards and slightly inwards at the level of the P3 coxae (Guinot 1991: pl. 3F). At each extremity of its horizontal course, suture 6/7 shows a marked spine in the male, while there is only a prominence in the female. Sternite 8 is longitudinally divided by a very short median line, and the sternoabdominal notch is deep. As in the Homolidae , the sternal plate bears large and well delimited sterno-coxal depressions at the level of the P2, P3 and P4 (sterno-coxal depressions 5, 6, 7).

Sternites 5, 6 and 7 of Poupinia hirsuta bear paired formations looking like setiferous cupules ( Figs 20 ; 21 ). Each cupule (small cup) comes in contact with the basal region of the corresponding coxa, specifically with its inflated supracondylar part, which shows a different texture and is covered by a very short, worn tomentum, mixed with longer setae along the margins. These cupules exist only in the female, while they are absent in the male, which shows similar P2-P4 coxae, with inflated and tomentose supra-condylar areas.

The axial skeleton of Poupinia is very peculiar, and such a disposition had never been described. There is a wide and short intertagmal phragma (i n c o n t r a s t t o l o n g i t u d i n a l l y e x t e n d e d i n Homola ranunculus , Fig. 18 ), but the center of the body is empty ( Fig. 22 ). This means that the short endopleurites and endosternites exclusively join laterally and do not present the median connections (by interfingering) seen in the other Homolidea. Poupinia lacks the median mass that constitutes the transverse binding between the two lateral endopleural parts, either by interfingering ( Homolodromiidae , Homolidae , Latreilliidae ) or by fusion ( Dromiidae , Dynomenidae, Cyclodorippoidea, Raninoidea , all Eubrachyura). Nevertheless, careful examination revealed that the external surface of the lateral endosternites were covered by irregular elongated structures, contrasting with the smooth surface of the intertagmal phragma ( Fig. 22B ). These structures actually correspond to the digitations (presumably corresponding to extremities of interosternites) that normally constitute the transverse, median binding by interfingering in the Homolidea. Here they are displaced to the sides so that Poupinia , as in the other Homolidea, actually presents interdigitations, but in a different location. We speculate that these digitations will ultim a t e l y f u s e w i t h e n d o p l e u r i t e s i n a n o t h e r evolutionary stage. The original condition of the Poupiniidae is now completed by this unusual skeletal organization. The skeletal data support the views pointed out by Guinot (1995) that Poupiniidae is unique to the Podotremata . However, if placement of the family Poupiniidae in the Homolidea remains unquestioned, this newly presented character does not permit to surely interpret it as a basal or advanced condition in this subsection. We will have to wait pending a more thorough investigation into the skeletal morphology and diversity in the Anomura, the Astacidea Latreille, 1802, and the Palinura Latreille, 1802. It is true that the relationships of the Archaeobrachyura (as a whole or partly) remain debatable.

Externally, the spermatheca occupies approximately the two-thirds of suture 7/8 and lies far from transversal suture 6/7. There is an extended aperture corresponding to the wole membranous area, which is relatively simple ( Fig. 20 ). Internally, the chamber is very inflated on its inner side and is filled by sperm.

CONCLUSIONS FOR THE HOMOLIDEA

In the Homolidea the sternum around the sutures 7/8 is modified to form the external part of the spermathecae, with distinct membranous areas belonging either to sternite 7, or to sternite 8, or to both. The relatively large spermathecal apertures are always situated on a level with female gonopores on the P3 coxae. The internal organization is rather similar among the genera and species, always with a chamber never far from the aperture and directly opening on the exterior.

Figures

FIG. 20. — Poupinia hirsuta Guinot, 1991, female 54 × 41 mm, allotype, French Polynesia (MNHN-B 24346), thoracic sternum. Abbreviations: cmxp1-mxp3, articular condyles of mxp1-mxp3; cu, cupule; cx1-cx4, coxae of P1-P4; g, female gonopore; s, spermathecal membranous part; p, prominence on each side of suture 6/7; s.p., inflated supra-condylar area of the coxa; 2-8, thoracic sternites 2-8; 3/4-7/8, sternal sutures 3/4 to 7/8. Scale bar: 1 cm.

FIG. 21. — Poupinia hirsuta Guinot, 1991, female 54 × 41 mm, allotype, French Polynesia (MNHN-B 24346), detail of sternal cupules and supra-condylar areas of corresponding coxae. Abbreviations: cu, cupule; cx2-cx3, coxae of P2, P3; g, female gonopore; p, prominence on each side of suture 6/7; s.p., inflated supra-condylar area of the coxa; 5/6, 6/7, sternal sutures 5/6, 6/7. Scale bar: 5 mm.

FIG. 18. — Homola ranunculus Guinot & Richer de Forges, 1995, female 41.4 × 38.1 mm, New Caledonia (MNHN-B 19869), axial skeleton. Abbreviations: br, transverse bridge; cx3, P3 coxae; i, connections by interfingering; i.p., intertagmal phragma; l.m., median line; s, location of the spermathecal chamber. Scale bar: 1 cm.

FIG. 22. — Poupinia hirsuta Guinot, 1991, female 54 × 41 mm, allotype, French Polynesia (MNHN-B 24346); A, thoracic axial skeleton, oblique view to show exclusively lateral location of phragmae; B, detailed view to show surface of endopleurites covered by digitations. Abbreviations: d, digitations; e, empty part of the body, without median connections; i.p., intertagmal phragma; P1-P5, pereopods P1-P5. Scale bar: A, 1 cm.