Registered users receive a variety of benefits including the ability to customize email alerts, create favorite journals list, and save searches.
Please note that a BioOne web account does not automatically grant access to full-text content. An institutional or society member subscription is required to view non-Open Access content.
Contact firstname.lastname@example.org with any questions.
We describe three diploid gynandromorphs in Artemia. Two belong to A. parthenogenetica and represent the first report of gynandromorphy for the species. One specimen was a female with a globular brood-pouch and gynandromorphic second antennae, whilst the other was a female with a closed malformed brood-pouch filled with live nauplii, and a long, mobile, penis-like structure projecting from the left side of the genital segments. Offspring from the latter parthenogenetic gynandromorph developed as normal all-female parthenogenetic Artemia. The third gynandromorph belongs to the zygogenetic species A. franciscana, being a female with claspers as previously reported in the same taxon. The occurrence of parthenogenetic gynandromorphs is best explained in light of sex determination mechanisms supporting the view that gynandromorphy might be triggered by a mitotic chromosomal mutation during early embryonic development.
A structure resembling the lacinia mobilis in Peracarida (Malacostraca) is described for the coxal gnathal edge of the mandibles in the halocyprid ostracode Spelaeoecia capax. The lacinia mobilis is present at the distal portion of the gnathal edge close to and articulated with the incisor process. Proximal and closely associated with the lacinia, two processes are present. In the center of the gnathal edge, a flat process partly covers two comb-like spines. A molar process (masticatory pad) is present at the proximal end of the gnathal edge. The lacinia mobilis described herein resembles the peracarid lacinia in possessing a number of cusps similar to the cusps of the incisor process, its orientation parallel to the incisor process and the presence of an articular condyle at the basis of the lacinia. The described similarities, however, concern only the left mandible of certain Peracarida where the mandibles are asymmetrical. In Spelaeoecia capax, the mandibles are symmetrical. The lacinia mobilis in certain ostracodes may have evolved independently from that in Peracarida. The term lacinia mobilis is used as a descriptive term only, not implying homology.
This study investigates the influence of gender on feeding and habitat niches in the ocypodid sentinel crabs Macrophthalmus convexus and M. definitus feeding on a mudflat in the Wakatobi Marine National Park, Indonesia. Male M. convexus possess sub-equal chelae that are considerably larger than those of females and of those of both genders of M. definitus. Habitat location, food (Chl a) biomass index in microalgae and seagrass mats on muddy sediments, faecal material, and feeding rates were analysed in females and males of both species throughout the lunar cycle in July and August 2002. Food biomass content was significantly higher in the upper than in the lower mudflat (P = 0.008). The particle size of faecal material did not vary between species or between genders of M. definitus, but the faeces contained larger particles in males of M. convexus compared with females and both gender of M. definitus. Macrophthalmus convexus predominantly inhabited pools on the upper and mid mudflats, whereas M. definitus was found in muddy sea-grass substrates on the mid and lower mudflats. Crabs were observed to emerge for feeding only on ebb tide during daylight. Macrophthalmus convexus showed significantly higher scoop rates than M. definitus (P < 0.05) during full and new moon. Feeding rates in male M. convexus were also significantly lower than of females (P < 0.001) throughout the lunar cycle. In contrast, feeding motions in M. definitus were generally variable and not gender-specific. However, males showed significantly reduced scoop rates in this species on the lower mudflat during the first quarter moon (P < 0.001). Scoop rate is not the only process affecting potential ingestion rate, however, in that several ‘pinches’ of sediment may be made by the chela before it is lifted towards the mouthparts.
The distribution of the prawn species belonging to the genus Palaemonetes is not well defined in the Mediterranean, especially in the south of France where controversy exists concerning taxonomic identification at the species level. A molecular diagnostic technique allowed us to determine without any doubt the presence of Palaemonetes varians in the Camargue. These basic results allowed us to undertake the ecological study of the species, which took place in the context of a massive 100-year flood during the winter 1993/94, leading to a rapid and major fall in salinity that remained low until 1997, before increasing. The impacts of low salinity on the catch and life history traits of Palaemonetes varians in the lagoon were investigated from 1993 to 1999. There was a positive correlation between catches and salinity. Although we observed a major decline in recruitment between the years 1993 and 1994, reproduction parameters and growth did not seem to be affected by low salinity. A comparative study of various life history traits between Mediterranean and northern environments populations was also conducted.
Asymmetry in mutual predation can be important in species replacement between native and invasive species. Mutual predation between the endangered Japanese native crayfish species Cambaroides japonicus and the North American invasive crayfish Pacifastacus leniusculus was studied to assess the potential impact of P. leniusculus on C. japonicus. We made laboratory experiments to examine mutual predation (i) between individuals in pairs of the same and different species and (ii) among a group comprising single and mixed species. We also made field surveys to clarify the frequency of cannibalism of the two species. In laboratory experiments, the frequency of cannibalism was low by both two species, but predation by P. leniusculus on C. japonicus was severe and most P. leniusculus survived both in different species pairs and in mixed species groups. In field surveys, remains of the two crayfish species, which may have been caused by predation by the same species, i.e., cannibalism, were scanty. The results suggest that asymmetry in mutual predation can be an important cause of species replacement of the native C. japonicus by the invasive P. leniusculus in the field.
This paper describes seasonal changes (summer vs. winter) in reproductive traits (fecundity in relation to female body size and dry mass, egg size, egg weight and reproductive output) of the semiterrestrial crab Sesarma rectum from a mangrove area (23°29′S, 45°09′W) on the northern coast of the State of São Paulo, Brazil. Regression analyses using log-transformed data were used to test size-dependent relationships, which were compared between the breeding periods by means of ANCOVA. During winter, the eggs produced were heavier and larger; therefore, no trade-off between egg number and female size was observed. The mean size of ovigerous females remained fairly constant across the seasons. In contrast, the reproductive output and mean dry weight of females decreased in summer. These trends may indicate the seasonal variation of energy allocate for reproduction. The ecological implications of the observed seasonal trends are discussed in the context of the temporal variation of environmental and biological factors in the region.
Overlap was found between habitats of Helice tridens, primarily an occupant of the upper and lower part of the intertidal areas between MTL (mean tidal level) and MHWS (mean high water spring), and H. japonica, usually restricted to the lower part of the intertidal area of the Shigenobu River Estuary, in southwest Japan. While immature individuals and large-sized adults of H. tridens occurred over the intertidal areas, the young adults of H. tridens were found only in the upper part of the intertidal area. This difference in the pattern of distribution between the young adults and the immature individuals of H. tridens seemed to be derived from interspecific competition or intraguild predation between H. tridens and H. japonica and/or intraspecific interactions within each species. These two species have the same of detritivore and carnivore food habits, and conspecific predation within and/or intraguild reciprocal predation between them were frequently observed in the field. In the present study, we performed field caging experiments to examine the dependence of predation ability on size between the two species. When individuals were ≦7.0 mm carapace width (CW), H. japonica had a higher ability to prey on members of H. tridens of the same size than H. tridens had on those of H. japonica. When individuals were ≧8.0 mm CW, there was no difference between the two species in terms of predatory ability, and the predation rate itself decreased. Therefore, H. japonica can exclude H. tridens from the lower habitats. However, the large sized individuals of H. tridens may intrude into the lower part of the intertidal area from the upper part. They can be against H. japonica, and can prey on the small sized individuals of H. japonica. However, thick sediment set in the cages increased the survival rate of the small individuals of H. japonica, because burrows dug in the sediment could be refuges for those of H. japonica from the intraguild predation by the large sized individuals of H. tridens. These refuges for the small individuals of H. japonica can be refuges also for those of H. tridens. However, burrows cannot be refuges from intraguild predation between similar-sized individuals of two species of the genus Helice. We can conclude that intraguild predation by H. japonica excluded the immature individuals of H. tridens in the lower habitat and restricted the young adults of H. tridens to the upper habitats in the estuary.
The first description of the larval stages of a representative of the family Paguridae from the SE Pacific coast of South America is presented. Larvae of Pagurus edwardsii, a common hermit crab from the rocky intertidal environment of the Chilean coast, were reared in the laboratory from hatching through the molt to juvenile stage I. Culture conditions included water temperature of 11 ± 1°C, salinity 32 ± 1‰, 12h:12h light : dark photoperiod, and feeding with Artemia sp. nauplii. The larval development of P. edwardsii included four zoeal stages (ZI–ZIV) and one megalopal stage; the duration in days for each zoeal stage was: ZI: 18.9 ± 0.5, ZII: 12.8 ± 0.8, ZIII: 5.9 ± 0.2, ZIV: 5.6 ± 0.6; and 9.1 ± 0.4 days for the megalopal stage. Descriptions and detailed illustrations are presented for each of the larval stages. Morphological comparisons made between P. edwardsii and other congeneric species with larval desciptions showed the main characteristics for the diagnosis of zoeal stages are: a) setation of antennal endopod and scaphocerite; b) spination and setation pattern of the basal endite of the maxilulle; c) setal formula of the endopodite of maxilliped 1; d) the segmentation model of the sixth pleomere; and e) the formula for the processes in the posterior margin of the telson. In contrast, the megalopal larva can be recognized by the number of setae on the endopod of maxilliped 3 and the absence of apical hooks on the appendix interna of the pleopods.
Cheliped parts of the fossil mud shrimp Callianopsis (Callianassa) clallamensis (Thalassinidea) were first recovered in the mid-nineteenth century from Oligocene marine rocks at Clallam Bay on the northern coast of the Olympic Peninsula, Washington State and described in 1924 as Callianassa clalllamensis. A second species, C. twinensis, was identified in 1926 from cheliped pieces found in rocks of similar age in the Twin Rivers area 20 kilometers southeast of Clallam Bay. Both fossil localities are in the Pysht formation of the Twin River Group. In 1997 these two species were reassigned to Callianopsis, and C. clallamensis is now recognized as the male and C. twinensis as the female of that species. An extensive collection of this fossil thalassinidean at the Burke Museum, University of Washington, particularly in calcite-cemented concretions, and commonly as disassociated parts, contains almost all anatomical hard-parts of the species. Study of this collection has made it possible to render a nearly complete morphological reconstruction of both the male and female of the species and to compare these specimens to the holotype, as well as photographs and original diagrams of varied specimens. This composite confirms sexual dimorphism and close morphological similarity to the extant species Callianopsis goniophthalma that lives at slope depths from the Gulf of Alaska to Baja California, Mexico. Sedimentary and paleontological features indicate that the fossil mud shrimp-bearing strata were deposited in upper slope to bathyal water depths.
The currently accepted reproductive cycle of Alaskan female Dungeness crab (Cancer magister) is that females molt and mate during summer and fall, extrude eggs in the fall, and incubate eggs through the winter until larval hatching in May and June. In this cycle, molting and mating are coincident with ovarian maturation. In this study, we quantified circulating concentrations of hemolymph ecdysteroids (molting hormones) in laboratory and field sampled crabs using an enzyme-linked immunosorbent assay (ELISA), for molt status assessment of individuals. Captive female crabs from southeastern Alaska (mean CW = 134.8 mm; n = 48) had a typical crustacean molt cycle profile of circulating ecdysteroids. Concentrations of ecdysteroids were low during intermolt (20.3 ± 0.7 ng/ml), maximal during premolt (1886.5 ± 186.2 ng/ml) 15 days before ecdysis and precipitously declined to low levels (< 90 ng/ml) 5 days prior to ecdysis. The duration of premolt was 150 days. Crabs held in captivity either molted (67%), extruded eggs (7%), or demonstrated no reproductive or molting activity (26%). Peak molting occurred in November for crabs held in the laboratory. Most (98%) of the female crabs sampled (n = 579) in Port Frederick, Alaska during the expected premolt period (May-July), had intermolt ecdysteroid concentrations. The capability to predict ecdysis 150 days prior to ecdysis by measuring ecdysteroid concentrations provides a useful tool to assess the molt status and timing of ecdysis in Alaskan Dungeness crab populations.
The evolutionary relationships among the six nominal genera within the spinicaudate clam shrimp family Limnadiidae, as well as the validity of the limnadiid genus Eulimnadia, have been much debated in the literature with little consensus emerging. The lack of resolution on these topics impedes evaluations of limnadiid biodiversity, phylogeny, and character evolution. To address these issues, we used Bayesian and parsimony methods to analyze DNA sequences from three genetic loci (28S, 12S, cytb) that were obtained from representatives of five nominal limnadiid genera and one undescribed limnadiid species. These analyses confirm the monophyly of Eulimnadia and the most taxonomically inclusive phylogenetic analysis (28S) produces the following tree topology: (((((Eulimnadia, Metalimnadia), undescribed limnadiid), Imnadia), Limnadopsis), Limnadia). This topology is inconsistent with prior estimates of limnadiid inter-generic relationships. Maximum likelihood-based constraint analyses demonstrate that the above topology is significantly better than prior hypotheses of limnadiid relationships, and support the monophyly of Eulimnadia. Morphological character optimization on this topology suggests that the postulated close relationship between Limnadia and Eulimnadia is based on shared ancestral characteristics rather than synapomorphies. Furthermore, the discovery of the genetically distinct undescribed limnadiid lineage strongly supports the necessity of efforts to better evaluate limnadiid biodiversity, especially those in poorly collected zoogeographic regions.
The systematics of the Calappa lophos species group is clarified using morphological and molecular data. The phylogeny of some Indo-Pacific species of Calappa is discussed. Two species, C. quadrimaculataTakeda and Shikatani, 1990, and C. guerini (Brito-Capello, 1871), previously synonymised with C. lophos (Herbst, 1782), are shown to be valid species using morphological and molecular data. A new species in the group, C. acutispina, is described from Madagascar. The usefulness of Bayesian inference in elucidating the phylogenetic relationships of some of the species of Calappa based on partial cytochrome oxidase I (COI) sequences is examined.
Two new monotypic genera of Cylindropsyllidae (Copepoda, Harpacticoida), Boreovermis and Bolbotelos, are described from subtidal sandy sediments in the Southern Bight of the North Sea. Boreovermis bilobata new genus, new species is primarily characterized by its conspicuous sexual dimorphism on P2 and P3. Bolbotelos longisetosus, new genus, new species is unique in its vermiform body morphology, bi-laterally compressed bulbous caudal rami, loss of inner basal spine on P1 and secondarily elongated geniculate setae on both P1 rami. Both genera are related to NavaloniaHuys and Conroy-Dalton, 1993 and WillemsiaHuys and Conroy-Dalton, 1993, with which they form a well supported clade of vermiform taxa within the Cylindropsyllidae. The relationships within this Navalonia-clade are analysed and apomorphic character states for each internal node and terminal taxon are discussed.
A new species of the deep-sea sponge-associated shrimp genus SpongicoloidesHansen, 1908, S. iheyaensis, is described and illustrated on the basis of 6 specimens (3 sexual pairs) collected from the North Knoll of the Iheya Ridge at depths of 988-1051 m, Ryukyu Islands, southern Japan. This is the fourth species of the genus known from the Pacific Ocean. The new species is similar to S. hawaiiensis from Hawaii and S. novaezelandiae from New Zealand, but is distinguished by the differences in spination of carapace, sixth pleonal somite, and third pereiopod. It is suggested that the egg number of the new species is greater than that of other congeneric species. Sexually dimorphic characters are discussed. A key to the Pacific species of Spongicoloides is provided.
Two new species of Axioidea were found amongst the deep-sea material recently collected from New Caledonia. Meticonaxius dentatus sp. nov. is unique among members of the genus by the presence of the teeth on the rostrum and the merus of the large cheliped. Oxyrhynchaxius tricarinatus sp. nov. is the third species known in the genus and is unique in bearing three dorsal ridges on the abdomen.
A new species of freshwater crab Microthelphusa viloriai, from the Andean range of Venezuela is described and illustrated. The type species of the genus, M. rodriguezi is redescribed on the following examination of the single specimen so far known. Data on the geographical and altitudinal distribution of the species of Microthelphusa are also presented.
A recent collection of freshwater crabs of the family Potamonautidae from central Angola included two species of PotamonautesMacLeay, 1838, P. anchietae (Brito-Capello, 1871), and P. kensleyi, new species, which are described. In addition, Potamonautes adeleaeBott, 1968, is recognized as a valid species, and the taxonomic status and biogeographic affinities of other species of freshwater crabs that have been reported from Angola are discussed. The addition of P. kensleyi and P. adeleae raises the number of species of freshwater crabs known to occur in Angola to seven.