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The microstructure of denticles in paired extant and fossil specimens of CallinectesStimpson, 1860, and Scylla de Haan, 1833, is examined and compared to the cuticle from the remainder of the claw. Denticles of Scylla serrata and Callinectes sapidus are differentiated from the surrounding cuticle by differences in the number of pore canals, tegumental canals, density, microhardness, and phosphorous content. Differentiated denticles can be observed in fossil Scylla and Callinectes on the basis of structure and phosphorus content. Increased hardness of denticle-type cuticle functions to resist abrasion encountered during durophagy and to resist the high forces generated by the denticles as a result of their geometry. Infolds along the lateral margins of the denticles are hypothesized to allow denticles to develop beneath the old cuticle before the molt, and then to emerge and expand after the molt. Future chemical and mineralogical work involving crustaceans should take into account the presence of denticle-type cuticle and not treat the cuticle of chelae as homogeneous tissue. Because denticle-type cuticle can be recognized in the fossil record, the emergence, variation, and phylogenetic trends of this adaptation can be tested. The increased calcification of claw tips and denticles may make them even more durable than the chelae.
This research examines the life cycle of the parasitic cymothoid isopod Glossobius hemiramphi and its role as a symbiont with its fish host, ballyhoo (Hemiramphus brasiliensis). Samples of H. brasiliensis were collected from July 1997 to October 1998 in nearshore waters of south Florida. Fish were randomly culled from a commercial lampara net fishery, and independent of the fishery, fish were collected with cast nets or hook and line. The average parasite prevalence was 10.1%, observed in 2,928 fish collected year round. Monthly prevalence ranged from 4.6 to 18.2% and was highest in the summer on small young-of-the-year fish. Prevalence declined with fish size from a high of 38.0% for fish 11-16 cm to a low of 3.3% for fish 28-29 cm. Ovigerous females were observed throughout the year and no within-brood mortality was evident. Marsupiumites developed through five distinct ontogenetic stages, and the final marsupial stage (manca) was likely immediately infestive upon release. Diminutive males (2.8-12.4 mm) were attached to the host's gill arches, and larger females (16.9-35.6 mm) occupied the buccal cavity. Only a single fish older than age-1 was infested. These results indicate that Glossobius hemiramphi is a protandric hermaphrodite with an annual life cycle. There was no evidence of a parasitic effect on the host fish condition (weight-length), but we cannot exclude the possibility that infested fish have a higher mortality rate than uninfested fish, at least temporarily (∼1 year).
Caridean shrimps are unique among decapod crustaceans in showing a great diversity of sexual systems, including gonochorism, protandry, protandry with primary females and simultaneous hermaphroditism. Crangon franciscorum (Stimpson, 1859) (Crangonidae), an ecologically and economically significant species from the Pacific coast of North America, has been assumed to be gonochoristic. Earlier population studies concluded that average lifespan is longer in females than in males, and that the latter die in or emigrate from estuaries after mating. This was believed to explain a recurrently observed “shrinking” of average male size starting during the fall of the first year of life. We investigated an alternative hypothesis according to which this species is a protandric hermaphorodite, and disappearance of large males from the population reflects sex change rather than death or emigration. We present several pieces of evidence in support of the alternative hypothesis: (i) ovarian development in males undergoing sex change, (ii) presence of atrophied vas deferens in secondary females, and (iii) observation of sex change in individuals kept in captivity. Our results are supported by histological study of the gonads, careful description of secondary sexual characters, and monthly sampling of an estuarine population (Grays Harbor, Washington). Tracking an identifiable year-class (1980) and combining field and laboratory data allowed us to assemble a life history schedule, including growth and a calendar of significant reproductive events. We discuss the implications of our results for the interpretation of survey data and studies on population dynamics.
The porcellanid crab Allopetrolisthes spinifrons, a symbiont of the sea anemone Phymactis papillosa, shows a suspension-feeding behavior related to flow oscillations (repetitive changes of flow direction). Individual crabs oriented their filter appendages (third maxillipeds) to maintain a concave face upstream, showing a higher frequency of maxilliped movements (flexion) at the start of inverted flow. The crab is primarily a suspension feeder that can ingest host mucus and feces. Contrary to free-living porcellanids, the symbiotic life-style offers access to exposed sites in the intertidal and subtidal environments that are favorable for passive suspension-feeding activities and consequently, an alternative feeding mechanism is not necessary.
The population biology of the black land crab, Gecarcinus ruricola (Linnaeus, 1758), was studied in the San Andres Archipelago in the western Caribbean. Investigations were conducted on the islands of San Andres (SA), and Old Providence/Santa Catalina (OP). On both islands the mean size differed little between the sexes, but males reached a larger maximum size by ∼5 mm CW. Crabs of both sexes reached greater mean and maximum sizes on OP than on SA (by ∼10 mm CW): this is tentatively attributed to the higher human population and heavier crab exploitation on the latter. The density of crabs was higher on OP than on SA. In natural ‘forest’ habitats it averaged 2174 crabs Ha−1 in the former, and 804 crabs Ha−1 in the latter. On both islands the densities were higher in watersheds adjacent to the coastlines where breeding females migrate to the sea, and to which returning larvae recruit. The total population estimates were about 3 million crabs on OP, and 800,000 on SA. The lower density and population size on SA can be attributed to a combination of environmental degradation and heavy exploitation. The relative growth patterns showed no unusual features. The species is heterochelic, without preferential handedness. The growth patterns of the chelae resulted in modest levels of both heterochely and sexual dimorphism; this has implications for the pattern of exploitation.
Nucleotide sequence data of the mitochondrial cytochrome oxidase I (COI) gene, were compared among 17 specimens of Sacculina carcini parasitising three portunid hosts as a preliminary assessment of haplotype structure in a poorly understood species for which there are few morphological characters on which to base taxonomic analysis. S. carcini parasitising Carcinus maenas (from Sweden, England and Denmark) were compared with S. carcini parasitising Liocarcinus marmoreus (from Ireland) and Liocarcinus holsatus (from Wales). Specimens of three congeneric sacculinid species and one confamilial species were included in the comparison as outgroups. The comparison confirmed that specimens of S. carcini from different hosts and different regions are all the same species. The data also suggested geographically consistent sequence differences among sampled sites, high levels of similarity within sites and very large differences between species, all of which suggests that analysis of the COI gene sequence could be a useful method for resolving population genetics and taxonomy of rhizocephalans.
A total of 3142 specimens of Pagurus comptus (White, 1847) were collected on the kelp beds in the Beagle Channel, Argentina, during 1999-2001. Fifteen of these hermit crabs were infested by a bopyrid provisionally identified as Anathelges cf. hyptius (Thompson, 1902). Of these parasites, 10 were attached to their hosts' pleons, whereas the remaining five were found inside the branchial chambers of the hermit crabs. All branchial parasites were immature females though one of them harboured a male. This is the first time that a postlarval stage of Anathelges is recorded inside the branchial chamber of its host. Whether this location is normal or erratic is unknown. This collection of Anathelges has made it possible for us to describe and illustrate four sequential female stages of this parasite, to extend the geographic range of distribution of this genus to the southern tip of South America, and to discuss the taxonomic value of some of the characters used to distinguish species in this genus.
A new harpacticoid copepod species of Apolethon (Laophontidae) from the intertidal zone of a subarctic bay in southeastern Alaska is described and illustrated. Apolethon hippoperus n. sp. is distinguished from its three congeners (A. fumator, A. trigonus, A. bilobatus) by paired pleural glands on the third urosomite. Adult Apolethon hippoperus bear conspicuous ovoid mucin structures located laterally on the double genital somite, originating from the pleural glands. Based on the description of A. hippoperus generic affinities become problematic. An examination of the apomorphies (P1 morphology, type of sexual dimorphism of male P3, P2-P4 with 2-segmented endopods; setation on A2 exopod, maxillular arthrites and basis, setation of mandibular palp) defining the Laophontoidea sensu Huys 1990 suggests that Apolethon is a laophontoidean but not a laophontid. Currently, we cannot place Apolethon with certainty in any known family of the Laophontoidea and recommend that Apolethon is placed as genus incertae sedis in Laophontoidea. This is the first taxonomic report of the genus Apolethon from the western hemisphere.
A new family of stenopodidean shrimp, Macromaxillocarididae, is described from an anchialine cave in Great Guana Cay, Exuma Cays, Bahamas. Macromaxillocaris bahamaensis new genus, new species, is the sole representative of the family. The new taxon clearly belongs to the infraorder Stenopodidea. However, the presence of a massive third maxilliped, pereiopods that increase in length posteriorly, an epistome with two fang-like projections, and a reduced branchial formula distinguish the new family from the rest of the taxa in the infraorder. Moreover, a bifid palp of the first maxilla and an unsegmented palp of the first maxilliped, which are characters not present in the other two known families in the infraorder, support the separate status of the new family. Diagnostic characters of both, the Stenopodidae and Spongicolidae, are found in M. bahamaensis also, being the new taxon morphologically more similar to the Stenopodidae. Diagnoses for the infraorder and the three families, and a key to the families are presented.
A new alpheid shrimp genus, Richalpheus, new genus, is established for R. palmeri, new species, from Panglao, Philippines, and based on a single specimen collected from a presumed thalassinidean burrow in a shallow lagoon. Richalpheus appears to be most closely related to Amphibetaeus Coutière and Leptalpheus Williams (sensu lato). Richalpheus and Amphibetaeus share the presence of a non-functional fossa-tooth system on the fingers of the major cheliped, but the new genus differs from Amphibetaeus by the absence of pereiopodal epipods and the presence of only four segments in the carpus of the second pereiopod. The syntypes of Amphibetaeus jousseaumei, a species not collected since the original description by Coutière, remain untraceable except for one major cheliped. Amphibetaeus jousseaumei is redescribed based on the original descriptions and illustrations of Coutière scattered in older French publications, and on the newly rediscovered, diagnostic major cheliped, which is designated as lectotype of A. jousseaumei.
The taxonomic status of the six Japanese species of Caridina described by W. Stimpson (1860) is clarified on the basis of fresh specimens from the type localities. Caridina grandirostris, which has long been synonymized under C. longirostris H. Milne Edwards, 1837, is shown to be a distinct species; C. leucosticta is redescribed; C. multidentata is the senior synonym of C. japonica De Man, 1892; C. acuminata and C. brevirostris are regarded as junior synonyms of Atyoida pilipes (Newport, 1847); and C. exilirostris is synonymized with C. typus H. Milne Edwards, 1837. Neotypes for the six species are designated to stabilize their taxonomy, all of which are redescribed and figured. The various nomenclatural problems associated with these species are discussed.
During deep-sea trawling in Taiwanese waters, four species of galatheids belonging to the genus Munidopsis were collected at two stations deeper than 3000 m. Three species represent new records from Taiwan: M. panamae Baba, 2005, M. profundaBaba, 2005, and M. teretisBaba, 2005, all recently described and known from very limited material. The other is a new species, Munidopsis tafrii, which resembles M. ceratophthalmaAlcock, 1901, and M. orcinaMcArdle, 1901, but clearly differs in characters of the carapace. The specimens of M. profunda from 4430-4455 m are the deepest record for marine animals from Taiwanese waters.
Aspects of the tail flip, escape response of a thermosbaenacean, Tethysbaena argentarii, were examined with the aid of S-VHS video. The first part of the escape action involves a 180° shift in orientation, where head and tail change position within 2/50 to 4/50 sec. This shift is caused by two successive, tail flips: first a ventral movement, which brings the tail region close to the thorax; then a dorsal motion, which causes the thorax/head region to flip backwards because of greater water drag in the tail region (tail fan). The 180° change in orientation is sometimes followed by a number a forceful dorso-ventral tail flips that promote rapid swimming in the new direction. The type of escape reaction in Tethysbaena argentarii is different from the ‘jet’stream' type of escape reaction seen in various shrimp, euphausids, and mysids, but it bears some similarity to that seen in stomatopods and in various crayfish where a 180° shift in orientation is also seen.
The complete mitochondrial DNA sequence is now recorded for the commercially important shrimp northern, or pink, shrimp, Pandalus borealis. The 15,905 bp genome is circular and consists of the genes known for other metazoans and with the same gene order as for Penaeus and Drosophila among others.