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Ever since the first individuals of the class Remipedia were discovered, it has been suggested that these animals are capable of injecting their prey with a venomous or digestive substance using the fang on their maxillules. In this study, we investigate the functional morphology of the putative injecting apparatus of Speleonectes tanumekes. Serial sectioning of specimens shows a pair of well-developed glands in the anterior part of the trunk. Spatial interpretations of serial sections suggest that extensions of the glandular cells collectively continue as ducts that lead to the distal segments of the maxillules where a complex of apodemal muscles, associated with a bulbous reservoir, serve to facilitate injection. Different components of the supposedly injectable substance appear to be separated throughout the apparatus.
We describe Cryptocorynetes longulus n. sp. as the second species assigned to the genus. Cryptocorynetes longulus is a relatively large species (up to 34.5 mm long with 38-39 trunk segments) that occurs in sympatry with species of the two other remipede genera Speleonectes and Godzilliognomus. It was collected from Big Fountain, an anchialine cave on Cat Island, Bahamas. The new species is distinguished from Cryptocorynetes haptodiscus in particular by its larger size and more robust habitus, higher number of trunk segments, shape of the head shield, and number of antennular articles; moreover, the prehensile cephalic limbs differ remarkably in shape and size from those described for Cryptocorynetes haptodiscus.
We report on the morphology and occurrence of the “mystax,” an overlooked cephalic structure found in males of certain Notostraca. The mystax is a conspicuous, protuberant, dark-brownish sclerodermal stripe located on the anteroventral flange of the carapace. Histological sections show the mystax as an expansion of the exoskeleton formed by the exocuticle. Examination of exuviae revealed that the old mystax remains intact in the shed cuticle. In some Triops populations of México and Japan, large individuals bearing ovisacs exhibit a “pseudomystax,” which consists of a dark-brownish band in nearly the same position as the mystax, but it does not form a protuberant stripe. A total of 661 males and 6402 ovisac-bearing individuals from four continents were examined. The mystax was found in males of Triops australiensis from Australia, T. granarius from Japan, Triops sp. from North America, Triops sp. from Africa, and Triops sp. from Asia. The mystax is absent in all ovisac-bearing individuals of all species analyzed and in all males of Triops cancriformis (Africa, Europe, and Japan), and in all males of the genus Lepidurus. Practical and systematic implications of the mystax are discussed.
In some crustaceans, compounds that weakly stimulate peripheral chemoreceptor cells elicit disproportionately large behavioral responses. Here, we investigated whether this is the case in the crayfish Procambarus clarkii. Resting animals were exposed to either a blank or ammonium, glucose, glutamate, glycine, maltose, or trehalose at predicted final concentrations of 200 μM to 2 mM. Glycine significantly increased the time spent walking. Maltose increased the time spent walking and the number of clasps of the small claws (dactyl clasps). Trehalose triggered leg probing/waving and dactyl clasping. Ammonium and glutamate failed to elicit responses. These results are consistent with the varied efficacies of those compound in stimulating leg chemoreceptor cells as determined previously with physiological methods. Glucose, however, elicited all three behaviors that we quantified - a result inconsistent with the earlier finding that glucose fails to elicit action potentials in the leg's nerve. To determine whether glucose-sensitive chemoreceptor cells are present in the legs, 150 μl of glucose or trehalose, at concentrations of 10 μM or 100 μM, was applied focally to crayfish legs and dactyl-clasp frequency was determined. At a concentration of 100 μM, glucose elicited a significantly higher dactyl-clasp frequency than at 10 μM. Trehalose elicited high dactyl-clasp frequencies at both concentrations. Crayfish legs are, therefore, sensitive to glucose but they are more sensitive to trehalose. Overall, behavioral responses to single compounds largely paralleled the relative abilities of those compounds to stimulate leg chemoreceptor cells.
We examined the fouling organisms on the exoskeleton of 762 adult male snow crabs (Chionoecetes opilio) from 10 sampling stations situated in the southern Gulf of St. Lawrence (SGSL) and the Scotian Shelf (SS) off the eastern coast of Canada. A total of twenty-one sessile invertebrate families were observed on the exoskeleton of crabs. Epibiotic families occurring on 10% or less of crabs were considered minor foulers, while families occurring in 50% or more were considered major foulers. Nine minor and 3 major families were observed in the SGSL. The most important taxa were the bryozoans Alcyonidium spp. (87.5%) and Hippothoa spp. (77.5%), as well as the polychaetes Spirorbis spp. (68.8%). Eight minor and 3 major families were observed in the SS. The principal taxa belonged to the cirripeds Balanus spp. (89.1%), the bryozoans Alcyonidium spp. (78.2%) and the polychaetes Spirorbis spp. (77.2%). The relative abundance of each of the taxa observed on crabs suggests that differences in the structure of the community exist between the two studied regions and within a given region. These differences were confirmed by multivariate analyses (e.g., MDS plot, ANOSIM and SIMPER analyses). Variations between the fouling communities are mainly driven by the presence/absence of bryozoans and barnacles. Our results also tend to show that the Cape Breton region may act as a transition zone between the SGSL and the SS. Results are discussed in a general ecological context. Potential stock management implications are also underlined.
Adolescent and mature female red king crab Paralithodes camtschaticus were captured by scuba divers and held in seawater tanks at the Kodiak Fisheries Research Center at ambient temperatures. Over three separate years, we monitored dates of embryo extrusion, timing and length of the hatching period, duration of embryological developmental, total degree-days, and volume and number of larvae released on a daily basis. Primiparous females extruded their embryos on a mean date of 3 February, two months prior to extrusion by multiparous crab. Mean hatching date for primiparous females occurred 16 days prior to that of multiparous females in 2001, and 12 days earlier in 2003. Primiparous females required a mean of 365 days and 2601 degree-days for complete embryonic development, whereas multiparous females required significantly less time, with a mean of 328 d, and 2482 degree-days. Although multiparous females were significantly larger than primiparous females, there was no significant difference between reproductive types in the time required for complete hatching (mean 32 days), total volume (mean 308 mL) or number of larvae released (mean 106, 884). Multiparous female crabs held in filtered or unfiltered (raw) seawater showed no differences in hatch timing, hatching days, or volume released. Virtually all larvae (91-95%) were released in the 4 hour period between 1800 and 2200 hours, and 50% were released in the first half-hour of darkness. Extended hatching exhibited by red king crabs is not synchronous with the occurrence of planktonic food sources, but may be an adaptation to the uncertainty of food availability. Shorter development times for multiparous embryos are necessary to complete the reproductive cycle prior to obligatory molting before extruding the next batch of eggs. This information was incorporated into a conceptual model of the first 3 years of reproduction for red king crab.
Home range, movements and zonation of Arenaeus cribrarius and Callinectes ornatus were analyzed in Ensenada de La Vela, in the Venezuelan Caribbean, using acoustic telemetry. Transmitters were attached to the carapace of 11 A. cribrarius and 11 C. ornatus, which were tracked during five campaigns between October 2002 and December 2003. The positions of each crab were registered every 12 hours, for periods of up to 10 days, and data were obtained on geographical localizations, distances traveled, speed, depth, perpendicular distance to the beachline, as well as type of bottom and physicochemical variables of the water. We found significant differences between the two species regarding home range size (sensu lato), movements, distance to the coastline, depth and the type of sediment where they appeared. Callinectes ornatus had a larger home range (x̄ = 72,475 m2) than A. cribrarius (x̄ = 16,625 m2) and presented one to three centers of activity, while individuals of A. cribrarius had only one center, with a few exceptions. Both species used intensively about half of their home range. Arenaeus cribrarius preferred the foreshore, while C. ornatus inhabited more distant waters; however, a certain degree of habitat interpenetration was observed. Callinectes ornatus was more active (x̄ = 74.6 m/12 hours, SE = 6.6) than A. cribrarius (x̄ = 56.6 m/12 hours, SE = 6.5), but a high variability in the movement rates existed even within an individual. Arenaeus cribrarius was associated with bottoms conformed by very fine mixed sands and low contents of organic matter, whereas C. ornatus appeared in silty bottoms with higher organic contents. New elements on the zonation of these swimming crabs are included in this study, complementing the patterns found in previous works.
Many porcelain crabs have an unusual claw (cheliped) form that is broad, flat and thin. This seemingly flimsy form suggests claws may be used more for display than for feeding or aggressive interactions. However, in the flat-topped porcelain crab Petrolisthes cinctipes, one of the most abundant intertidal crustaceans on the Pacific coast of North America, we observed a high proportion of individuals with puncture wounds on their claws. Claws therefore do appear to be used in intra-specific aggression. To examine factors that might influence injury prevalence, samples of P. cinctipes were collected from four sites in Barkley Sound, two wave-exposed, and two protected. In addition, laboratory experiments examined the effects of density and crab size on the incidence of puncture wounds. Crabs from wave-exposed, high-density sites and smaller crabs both exhibited significantly higher proportions of puncture wounds. Although not statistically significant, laboratory experiments revealed a trend towards a higher incidence of puncture wounds in high-density groups. Wound frequency did not differ between the sexes, so these injuries are not likely a result of intra- or inter-sexual interactions. Puncture wounds were concentrated on claw fingers (either the dactyl or propus), and along the ventral margin of the manus, both of which are likely to be nearest an opponent during shoving interactions. Overall, these data suggest that the claws of P. cinctipes mediate intra-specific competitive interactions that frequently escalate to injury.
The life history and reproduction of the amphipod Jassa slatteryi were investigated monthly for one year on a seagrass bed (Zostera marina L.) in Gwangyang Bay, southern Korea. The standing crop of seagrass showed two peaks in spring and fall. Population dynamics of J. slatteryi was closely correlated with the standing crop of seagrass, suggesting that there is biological interaction between these two species. The life-history pattern was annual and iteroparous with two principal periods of juvenile recruitment during the year; in spring (March to May) and fall (October to December). Overall sex ratio was female-biased. The mean body length of adults and brood size was larger in the spring breeding period than in the fall. There was a positive relationship between the brood size and body length of ovigerous females. The mean egg volume was more than 0.03 mm3 in fall breeding periods, but in other periods it was less than 0.03 mm3. Egg volume was positively related to body length of ovigerous females. At any given female size, egg volume was significantly higher in the fall than in the spring, whereas brood size in the spring was significantly larger than that in the fall. The reproductive output of females was much greater in the fall than that in the spring, suggesting higher reproductive effort during the fall breeding period.
The presence of small trout together with fairy shrimp (Chirocephalus diaphanus) in isolated corrie lakelets in the French Pyrenees suggests that the fish might be agents of dispersal of the shrimp, if resting eggs could survive ingestion and freezing. Resting eggs in ovigerous females of Chirocephalus diaphanus can pass through the digestive tract of a trout and be subsequently frozen without losing their viability. Subsequently fecal pellets were collected from each fish. The gut passage time of C. diaphanus eggs were up to 4 days. Resting eggs recovered from fecal pellets were counted, frozen and then incubated. Hatching of nauplii began after 32 days, and 50.9% (sd. 29.4) hatched over the following 7 days. Ovigerous females of lab cultured C. diaphanus were administered to four trout Salmon trutta kept in separate tanks. Therefore, fish can aid upstream dispersion of these fairy shrimp.
San Francisco Bay and its estuary is a heavily invaded region due to organisms arriving in ballast water and on fouled ships, as well as with the intentional release of non-native species. Recent crab invasions rendered previous means to identify crab larvae unusable. We provide an illustrated dichotomous key with descriptions of stage I zoeae, and to facilitate identification use external characters that remain definitive through all zoeal stages. Crab zoeae included in this key are as follows: Cancer antennarius, Cancer gracilis, Cancer magister, Cancer productus, Carcinus maenas, Eriocheir sinensis, Hemigrapsus nudus, Hemigrapsus oregonensis, Lophopanopeus bellus, Rhithropanopeus harrisii, Pachygrapsus crassipes, Pyromaia tuberculata, and the family Pinnotheridae. This work aims to provide a tool to aid in the understanding of brachyuran zoeae of the San Francisco Bay and estuary.
Megalopal and first crab stage morphology of Cyrtograpsus angulatus Dana was studied in specimens from Mar Chiquita Lagoon, Argentina and an identification key for the megalopae of the four southwestern Atlantic varunid crabs is proposed. Some anomalous first crabs were observed that differed in the carapace shape and in the orientation of the ocular peduncle. These crabs survived in laboratory cultures, molting to the following stage with normal aspect. An anomalous Chasmagnathus granulatus first crab was also found in the field. We speculate that these odd crabs appeared after a complete, but defective, ecdysis. Since the ultimate body structures to be separated from the exuvia are probably the cephalic appendages and the eyes, their survival in the field would be difficult since vision may help them to detect predators.
Nine specimens of retroplumid crabs collected from the late early or early middle Eocene Tallahatta Formation in southern Alabama form the basis for description of a new species, Costacopluma grayi. The discovery confirms the extension of the range of the genus into the Eocene and represents the first occurrence of Costacopluma in the United States. As a result of the geologic range extension, the genus is now known to be contemporary with two other retroplumid genera, Retrocypoda, and Retropluma.
The hypothesis of monophyly in Paguroidea and the relationship of this superfamily to the other three superfamilies of Anomura have been reassessed using current cladistic methods and computer generated analysis. In the analysis, 79 external morphological characters were examined for an in-group consisting of the seven paguroid families, Pylochelidae, Coenobitidae, Diogenidae, Pylojacquesidae, Paguridae, Parapaguridae, and Lithodidae (divided into the subfamilies Lithodinae and Hapalogastrinae), three hippoid families, Blepharipodidae, Albuneidae, and Hippidae, five galatheoid families, Galatheidae, Chirostylidae, Kiwaidae, Aeglidae, and Porcellanidae, and the Lomisoidea's monotypic Lomisidae. The out-group was comprised of Neoglyphea inopinata, representing Fractosternalia, and the families Dromiidae and Dynomenidae representing Brachyura. This analysis has shown that Anomura indeed is a monophyletic infraorder, as is Hippoidea a monophyletic superfamily. However, while six of the paguroid families form a cohesive clade, the two subfamilies of Lithodidae form a distinct clade more closely related to the superfamily Hippoidea than to the other paguroids. Galatheoidea, as presently constituted, is polyphyletic. Aeglidae, like Lithodidae, is more closely related to Hippoidea than to the galatheoid clade formed by the families Galatheidae, Chirostylidae, and Porcellanidae. Kiwaidae is also distinct from Galatheoidea sensu stricto, but its relationship, and that of Lomisoidea, to the remainder of the anomuran taxa are unresolved in the present analysis. As a result of this reappraisal, we propose that Lithodidae be removed from Paguroidea sensu lato and elevated to superfamily rank with families Lithodidae and Hapalogastridae. Similarly, we propose that Galatheoidea be restricted to the families Galatheidae, Chirostylidae, and Porcellanidae, whereas Kiwaidae and Aeglidae are each to be elevated to superfamily rank. Anomura will then consist of seven superfamilies, Hippoidea, Lithodoidea, Aegloidea, Lomisoidea, Kiwaoidea, Galatheoidea sensu stricto, and Paguroidea sensu stricto.
A new species of pennellid (Pennellidae, Copepoda), Sarcotretes longirostris n. sp., is described based on specimens collected from bluefin driftfish (Psenes pellucidus Lütken) found in the stomach of short-finned pilot whale (Globicephala macrorhynchus Gray) caught in the western North Pacific off central Honshu, Japan. The new species differs from its congeners in the possession of 1) a long proboscis (longer than the cephalothorax); 2) a pair of blunt, lateral cephalothoracic processes (holdfast); and 3) a long neck that is distinctly longer than the trunk. This is the first species of copepod parasite reported from a representative of the genus Psenes.
A review of the isopod genus ChiridoteaHarger, 1878 is presented. Five species are recognized from the eastern United States and the northern Gulf of Mexico (Chiridotea almyra, C. arenicola, C. coeca, C. excavata and C. tuftsii). C. nigrescens is regarded as a junior synonym of C. coeca. Diagnoses and descriptions are given for each species, neotypes are selected for C. coeca and C. tuftsii, and a key for species identification is presented.
A new species is described from the coast of Chile, Anchistylis watlingi. The new species can be discriminated from all other species of Anchistylis by the presence of a scalloped ridge from the dorsum to the anteroventral corner. The new species is most similar to A. notusLomakina 1968 from Argentina, and A. waiteiHale 1945 from Australia. The new species has been collected from multiple locations, from the south of Chile to the north, corresponding roughly to the Peru-Chile marine biogeographic province, in depths from 0-30 m. A key to the species of Anchistylis is included.
Chalarostylis elegansNorman 1879 was described in 1879 from a single adult male specimen collected in the Porcupine Bight off the coast of Ireland. Recent collections in this area retrieved an additional specimen, a sub-adult female. The original specimen is in poor shape, soft with the first and second pereiopods broken. The original description (Norman, 1879) did not include any figures, although the holotype was deposited in the British Museum of Natural History. Chalarostylis elegans is redescribed and illustrated based on the new female material and reexamination of the male holotype. The new female specimen is entire with a robust first pereiopod (missing on the holotype) with a group of long setae terminally, identical to the first pereiopod in Dasylamprops Reyss 1978. Based on these observations Dasylamprops is considered a junior synonym of Chalarostylis. Dasylamprops guanchi is transferred to Chalarostylis becoming the second species within the genus.
Large branchiopod crustaceans inhabiting ephemeral ponds are well adapted to their highly unpredictable habitat with a life cycle that includes a short-lived adult stage and a long-lived, desiccation-resistant egg stage. One well studied large branchiopod is the clam shrimp Eulimnadia texana, an androdioecious species with populations comprised of males and self-compatible hermaphrodites. Likely due to the harsh environments in which the eggs are found, e.g., dry areas with high heat and high irradiation, extraction of DNA from individual eggs for genetic analyses can be problematic. Here we report a number of modifications that we have tested allowing for increased efficiency and success in extracting high quality DNA from the eggs, nauplii, and adults of E. texana that may prove useful for similar studies of other species of large branchiopods.