Subfamily Trogloplacinae Guinot, 1986

Australocarcinus riparius [A.J. Francis in P. Davie 2002: 503]

Museums

Regional Maps

• Trogloplacinae Guinot, D. 1986. Description d'un Crabe cavernicole aveugle de Nouvelle-Bretagne (Papouasie Nouvelle-Guinée), Trogloplax joliveti gen. nov. sp. nov., et établissement d'une sous-famille nouvelle, Trogloplacinae subfam. nov. Comptes Rendus (Hebdomadaires) des Séances de l'Academie des Sciences. Série D. Sciences Naturelles 3 303(8): 307-312 [307].

  Type genus:

   Trogloplax Guinot, 1986.

Introduction

The Trogloplacinae Guinot, 1986, was originally described for a single monotypic genus, Trogloplax Guinot, 1986, as a subfamily of the Goneplacidae (sensu lato). Davie & Guinot (1996) added Australocarcinus, including three species, and pointed out a relationship to the Chasmocarcininae Serène, 1964, a marine, mostly subtidal group of goneplacids. In both subfamilies the penis lies in either an enclosed or an open groove in sternite 8, such that sternite 8 has an intercalated plate anteriorly. However, in spite of the similarity in the coxosternal plate between the Trogloplacinae and the Chasmocarcininae, there are some notable differences between the two taxa which warrant their separation. A major difference is that in the Chasmocarcininae the basal antennular segment is very swollen and completely fills the antennular fossa, such that the flagellum is excluded and cannot be folded. Also, the male second gonopod (G2) of Chasmocarcininae is noticeably shorter than the first (G1) with the flagellum more or less short, whereas in the Trogloplacinae G2 is as long or slightly longer than G1, and the flagellum occupies about half, or slightly more, of the length. Finally, Trogloplacinae are only known from freshwater and upper estuarine environments, and Australocarcinus, at least, has evolved direct development through to juvenile crab stage, a characteristic completely lacking in other Goneplacidae. While its affinities seem to be with the Goneplacidae, a family status is preferred for this unusual group of freshwater crabs.

Diagnosis

Carapace rounded; sometimes poorly calcified; anterolateral margin cristate, entire or toothed; front with or without shallow median indentation, without latero-external notch. Eyes relatively small. Antennules folded completely into fosset. Antenna lying in orbital hiatus. Buccal frame quadrangular; third maxillipeds wide, almost completely closing buccal cavity; exopod broad, with flagellum. Thoracic sternum very broad, with all sutures interrupted; large part of sternite 8 exposed; supplementary transverse suture in middle of sternite 8, parallel to suture 7/8, forming supplementary plate. Sterno-abdominal cavity deep. Male abdomen with segments 3–5 fused. Abdominal locking mechanism in normal position. Vulvae of female very large, occupying position near extremity of sternal suture 5/6. Penis very long, lying in covered channel on sternite 8, only uncovered next to the coxa of last leg, finally protruding as long soft papilla. Chelipeds with minor heterochely and heterodonty. Male first gonopod stout, moderately tapered, with an apical aperture; second gonopod about as long as first, with flagellum about same length as peduncle. (After Davie & Guinot 1996).

General References

Davie, P.J.F. & Guinot, D. 1996. Two new freshwater crabs in Australocarcinus Davie, with remarks on Trogloplacinae Guinot and Goneplacidae MacLeay (Crustacea: Decapoda: Brachyura). Memoirs of the Queensland Museum 39(2): 277-287

Serène, R. 1964. Redescription du genre Megaesthesius Rathbun et définition des Chasmocarcininae, nouvelle sous-famille des Gonoplacidae (Decapoda Brachyura). Crustaceana 7(3): 175-187

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