Danièle Guinot

Spermatozoal ultrastructure in three species of hydrothermal vent crab, in the genera bythograea, austinograea and segonzacia (Decapoda, Brachyura, Bythograeidae)

The ultrastructural investigation of the spermatozoal morphology of the hydrothermal vent crabs, Bythograea thermydron, Austinograea alayseae and Segonzacia mesatlantica (family Bythograeidae) reveals a consistent familial sperm type and a close similarity between the three genera and the deep water trapeziid, Calocarcinus africanus. Association of the bythograeids with Calocarcinus is supported (apart from general similarity) by three synapomorphies: modification of the xanthid ring, development of a well developed periopercular rim (weakly shared with some xanthid and potamid members) and, as a particularly striking link, the unique spiral configuration of the contents of the outer acrosome zone. Calocarcinus is distinguished by shortening of the posterior dense zone into a true xanthid ring and, less so, by a flatter operculum. Bythograea and Segonzacia are apomorphic in the independent loss of the ragged outer acrosome profile. Their sister genus Austinograea has no distinct apomorphies (with the possible exception of an apical perforation in the operculum). The similarity between the spermatozoa of Calocarcinus and the investigated bythograeids and the dissimilarity between Calocarcinus and other trapeziids is evidence for possible inclusion of Calocarcinus in the Bythograeidae. This hypothesized relationship of Calocarcinus within the Bythograeidae sensu lato and its deep water distribution suggests origin of hydrothermal bythograeids from Calocarcinus-like deep water xanthoids which may have entered the hydrothermal system in or after the Eocene. Further investigation of somatic morphology is required to test this putative relationship.

The spermatozoon of Calocarcinus africanus (Heterotremata, Brachyura, Crustacea): ultrastructural synapomorphies with xanthid sperm

Summary Features of the spermatozoon of Calocarcinus africanus which are general for heterotremes and endorse its inclusion in the Heterotremata are: extension of the subacrosomal chamber almost to the anterior apex of the sperm, presence of an acrosome ray zone, and presence of a thickened ring where the capsule surrounds the base of the subacrosomal chamber. A feature shared with “higher” heterotremes is the restriction of cytoplasm to the periacrosomal region, the arms being nuclear only, in contrast with invasion of their chromatin with cytoplasm and microtubules in majids; and loss of a posterior median process, containing chromatin, which is present in majids as in raninids and homolids. The relationship of Calocarcinus with xanthids is unequivocally supported by (1) presence of a posterior circumperforatorial zone, the xanthid ring; (2) the precise form of the acrosome ray zone which is wide anteriorly and sends a long slender extension posteriorly to meet the ring; (3) the irregular external margi...

Contrasting spermatozoal ultrastructure in two thoracotreme crabs, Cardisoma carnifex (Gecarcinidae) and Varunu litterata (Grapsidae) (Crustacea: Brachyura)

Despite its terrestrial mode of life, Cardisoma carnifex (Gecarcinidae) returns to the sea to breed, and its spermatozoon displays all of the diagnostic features of thoracotreme sperm: absence (clearly loss) of the acrosome ray zone; presence of an apical button filling an opercular perforation; concentric lamellation of the outer acrosome zone; and the near-horizontal accessory opercular ring. In contrast, Varuna litterata (Grapsidae, subfamily Varuninae), a freshwater species, though again returning to marine (or estuarine) conditions to breed, shows only a negative state, absence of acrosome rays (other than a questionable presence of concentric lamellae) which would place it in the Thoracotremata. It does not display the grapsid synapomorphy, loss of the thickened ring. The distinctness spermatologically of Varuna from other grapsids is susceptible to a number of explanations among which are: (1) it is not a grapsid but a thoracotreme descended from a stock which had not yet developed typical thoracotreme spermatozoal ultrastructure; (2) it is a grapsid which has lost typical thoracotreme spermatozoal ultrastructure; (3) it is a heterotreme which has developed a thoracotreme configuration of genital pores independently of true thoracotremes. Of these alternatives, (3) is considered unacceptable, but the choice between (1) and (2) is difficult, although classical taxonomy would favour alternative (2). Absence of a recognizable acrosome ray zone, in Varuna sperm, presence of which is a typical heterotreme feature is also noted for the heterotremes Potamonautes, Potamon (Potamidae), and Australocarcinus (Goneplacidae), all of which are freshwater genera.

Ultrastructure of the spermatozoa ofCorystes cassivelaunus (Corystidae),Platepistoma nanum (Cancridae) andCancer pagurus (Cancridae) supports recognition of the Corystoidea (Crustacea, Brachyura, Heterotremata)

A combination of characters, not individually unique, possessed by the corystid,Corystes cassivelaunus, and the two cancrids,Platepistoma nanum andCancer pagurus, defines a corystoid-type of spermatozoon: the basally bulbous, anteriorly narrowing perforatorium, the extent of this almost to the plasma membrane through a widely perforate operculum, and the simple inner acrosome zone, lacking an acrosome ray zone. The sperm of the two cancrids are closely similar, that of the corystid differing, for instance, in the less pointed, and less tapered, form of the perforatorium. This relative uniformity of spermatozoal ultrastructure in the cancrid+corystid assemblage so far investigated supports inclusion of the two families in the superfamily Corystoidea by Guinot (1978). The combination of perforation of the operculum and absence of an acrosome ray zone (at least in a clearly recognizable form) are features of the Potamidae which possibly indicate that the latter family, modified for a freshwater existence, is related to the cancrid+corystid assemblage. Some elongation of the centrioles, apparent at least inCorystes, may be a further link with potamids in which they are greatly elongated. The coenospermial spermatophores of cancridoids are a notable difference from the cleistospermia of potamids; but the latter is probably an apomorphic modification for fertilization biology.

Podotreme affinities of Raninoides sp. and Lyreidus brevifrons: evidence from spermatozoal ultrastructure (Crustacea: Brachyura: Raninoidea)

Spermatozoal synapomorphies which singly or collectively distinguish Raninoidea are: (1) the presence of single (Ranina, Raninoides) or multiple (Lyreidus) keel-like projections of the acrosomal capsule; (2) a very large, weakly electron-opaque peripheral acrosomal zone (Ranina, Raninoides) and an homologous large outer zone in Lyreidus; (3) poor differentiation of the operculum from the capsule (autapomorphy); (4) a very well developed, perforate subopercular zone, of variable form; (5) presence of unique inward longitudinal projections (septa or corrugations) in the wall of the subacrosomal chamber (autapomorphy). Shared, presumably synapomorphic characters of Ranina and Raninoides but not of Lyreidus within the Raninidae, are: (1) branching of some of the subacrosomal septa (unbranched in Lyreidus); (2) the subspheroidal form of the acrosome in Ranina with a length: width ratio (L:W) of 0.76, and, although slightly more depressed, in Raninoides (L:W 0.73), considered apomorphic relative to the more depressed form in Lyreidus (L:W 0.52); (3) single or multiple coiled perforatorial filaments (Ranina, Raninoides) contrasting with a capitate perforatorium with “amoeboid” head in Lyreidus; (4) division of the capsule wall to give one posterior (Ranina) or multiple enclaves, plesiomorphically (?) absent in Lyreidus. Similarities of Lyreidus with other podotremes include the capitate perforatorium, questionably related to the radiate spiked-wheel structure of homolids in which acrosome proportions are similar or less closely to the bilateral capitate perforatorium of dromiids and dynomenids, and basal capsular projections as in the dromiid Stimdromia (=Petamolera) lateralis and in cyclodorippoids. No spermatozoal synapomorphies support a sister-group relationship of raninoids and heterotreme-thoracotreme crabs.

Non-indigenous freshwater crabs in France: a new occurrence of a potamid near Nice

The presence of a crab in the Cagne River, in south-eastern France near Nice (Alpes-Maritimes), has been known since about 1985 (M. Pascal 2000, personal communication). A brachyuran crab of the genus Potamon Savigny, family Potamidae Ortmann, referred to by locals as the ‘‘blue crab’’, was first observed in 2000 ( J.-L. Teyssie 2002, personal communication) and then collected in this river in 2000 and the following years. The occurrence of the crab was confirmed in 2005 by new field observations by one of us (P. Noel) and also documented by canyoning enthusiasts and fishermen (Barla 2005, Teyssie 2005). This crab is totally dependent on freshwater, even if it is located not very far from the sea (about 10 km); it shows a direct development without freeswimming larvae and has no recognizable close relatives in the sea. The species has been presumably introduced with Turkish imported crayfish, Astacus leptodactylus (Eschscholtz) in the 1960s and 1970s, but its precise origin in Turkey is unknown. There is no doubt that the crab introduced into France belongs to the genus Potamon (type species: Potamon fluviatile Savigny, junior subjective synonym of Cancer potamios Olivier; nec Cancer fluviatilis Herbst), the only genus which occurs around the Mediterranean Basin, in North Africa and

Spermatozoal ultrastructure in four genera of Homolidae (crustacea, decapoda): Exemplified byHomologenus sp.,Latreillopsis sp.,Homolomannia sibogae andParomolosis boasi

The spermatozoa ofHomologenus sp.,Latreillopsis sp.,Homolomannia sibogae andParomolopsis boasi confirm characteristics of a distinctive homolid spermatozoon previously established forHomola sp.,Paromola sp. andParomola petterdi. Homolid features are (1) moderate anteroposterior depression of the acrosome (ratio of length: width 0.4–0.6) as in lyreidine raninids (0.5), depression being greater in dromiids and dynomenids (both 0.3); (2) the capitate form of the perforatorium, shared with dromiids, dynomenids and lyreidine raninids; (3)the autapomorphic spiked-wheel form of the anterior expansion of the perforatorium; (4) horizontal zonation of the acrosome is possibly a unique synapomorphy of homolids with dromiids and dynomenids, and therefore an autapomorphy of the dromioid-homolid assemblage. In dromiids the posterior zone is proportionately the larger, while in homolids the anterior zone is the larger. The anterior zone is complexly subdivided in dynomenids; (5) the autapomorphic presence of numerous radial arranged extension of the acrosomal operculum into the perforatorium; (6) presence of nuclear arms, a symplesiomorphy of all investigated crabs, but small or questionably sometimes absent in Dromiidae; (7) absence of microtubules from the nuclear arms, as in dromiids, raninids, higher heterotremes and thoracotremes; (8) transient presence of a posterior median process of the nucleus. The process is not seen in dromiids but occurs in anomurans and lower heterotremes; (9) apical perforation of the operculum, also seen, apparently symplesiomorphically, in dromiids, raninids, and lower heterotreme families; (10) absence of an acrosome ray zone, probably homoplasic with absence in raninids; (11) location of most of the cytoplasm, including tortuous membranes and degenerating mitochondria, below the acrosome, also seen inLyreidus; (12) presence, in at least some species, of centrioles, unknown in dromiids and raninids and variable in occurrence in heterotremes.

Relationships of the Cyclodorippoidea Ortmann: evidence from spermatozoal ultrastructure in the genera Xeinostoma, Tymolus and Cymonomus (Crustacea, Decapoda)

Summary The spermatozoa of two genera and species of Cyclodorippidea, Xeinostoma richeri (Xeinostominae) and Tymolus sp. (Cyclodorippinae), and one species of Cymonomus sp. (Cymonomidae) are found to constitute a distinctive cyclodorippoid sperm-type characterized by (1) sperm anteroposteriorly depressed, mean ratio of length to width 0.54–0.63; (2) operculum extending to the lateral limits of the acrosome (autapomorphy of cyclodorippoids) and centrally perforate or (Cymonomus sp.) thinner; (3) contents of acrosome vesicle with two major horizontal zones, as in homolids and dynomenids, including a dense lower (posterior) zone; (4) perforatorium very wide (0.3 width of acrosome), anteriorly rounded, not capitate, lacking radiate projections; (5) acrosomal capsule with external projections over its posterior half; (6) slender dense filaments extending into the perforatorium from its walls, their bases associated with corrugations of its basal wall; (7) nucleus, cupping the acrosome and cytoplasm, with well-...

The ultrastructure of the spermatozoon ofParadynomene tuberculata Sakai, 1963 (Crustacea, Brachyura, Dynomenidae): Synapomorphies with dromiid sperm

The dynomenid spermatozoon, exemplified here byParadynomene tuberculata, resembles the spermatozoa of the Dromiidae, Homolidae and lyreidine raninoids and differs markedly from those of other crabs (the heterotreme, thoracotremes, raninines and raninoidines) in the depressed, discoidal form of the acrosome and the capitate form of the perforatorium. Four or five apparent dynomenid—dromiid sperm synapomorphies are recognizable. (1) Dynomenids (P. tuberculata) and dromiids differ from homolids and lyreidines in the greater depression of the acrosome (ratio of length to width=0.3); (2) the capitate head of the perforatorium is bilaterally prolonged inP. tuberculata as in dromiids though symmetrical in homolids; (3) dynomenid and dromiid sperm lack the—albeit variably developed—posterior median process of the nucleus seen in homolids, anomurans, raninoids and lower heterotremes; (4)P. tuberculata, like dromiids and less distinctly homolids, has an apical protuberance of subopercular material through the opercular perforation, unknown in other crabs, being distinct from the apical button of thoracotreme sperm; (5) a less certain synapomorphy is the anterolateral electron-pale peripheral zone of the acrosome. These synapomorphies endorse a sister-group relationship of dynomenids and dromiids,P. tuberculata sperm differs notably from the sperm of dromiids in the more complex zonation of the acrosome. The perforatorium lacks the radial rays (“spiked wheel”) of homolid sperm and does not show the “amoeboid” form seen in lyreidines. Absence of internal corrugations of the perforatorial chamber is a major difference from all examined raninids. Centrioles are only very tentatively identifiable. Nuclear arms are absent in glutaraldehyde fixed spermatozoa ofP. tuberculata and have not been observed in the dromiidPetalomera lateralis but are present as three small radial vertices in the dromiidDromidiopsis edwardsi and in homolids.P. tuberculata resemblesPetalomera lateralis in the large size of the sperm nucleus relative to the acrosome compared withD. edwardsi and homolids.

Mithracites takedai, a new homoloid crab (Decapoda, Brachyura) from the Lower Cretaceous (Aptian) of Colombia

A new homoloid crab, Mithracites takedai, is described on the basis of two specimens from Colombia, preserved in a limestone nodule of early Aptian (Early Cretaceous) age, as dated by co-occurring ammonite species. The new species differs from the type species, M. vectensis, by a distinctly sulcate front, a narrower anterior mesogastric process, and a differently shaped cardiac region. The status of the family Mithracitidae Stevcic, 2005, is revised and an emended diagnosis is provided; the appearance of the linea homolica in extinct homoloids is discussed.