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Two new species of fairy shrimp from North America, Streptocephalus henridumontis and Streptocephalus thomasbowmani, are diagnosed and figured. A brief account on the conservation status of the New World species of the genus and an updated species identification key are included. Streptocephalus thomasbowmani n. sp., endemic to New Mexico, U.S.A., is morphologically similar to S. dorothae. Streptocephalus henridumontis n. sp., whose populations occur along the Sonoran desert in northwestern México and southwestern United States, is morphologically similar to S. mackini. The peduncle of the antennal distal outgrowth of the two new species is of the long type. Streptocephalus thomasbowmani has uniramous ovaries, whereas S. henridumontis has biramous ovaries. With the inclusion of the new taxa, the number of species of the genus recorded from the American continent is 15. Seven (S. dorothae, S. henridumontis, S. linderi, S. mackini, S. sealii, S. similis, and S. texanus) have a wide geographical distribution and seem to be under no immediate threat. Conversely, eight species have a restricted distribution. Thus, S. antillensis, S. kargesi, and S. potosinensis can be considered as Critically Endangered (CE), and S. thomasbowmani, S. guzmani, S. mattoxi, S. moorei, and S. woottoni as Endangered species (EN), following the IUCN red list criteria.
We report the first two records of the fairy shrimp Streptocephalus moorei from the United States, previously known only from its type locality in southeastern Chihuahua, México. An updated morphological diagnosis and habitat data are provided. Streptocephalus moorei, previously considered as a critically endangered species under the IUCN red list criteria, is now assessed as an endangered species on the basis of the following criteria: area of occupancy estimated to be less than 500 km2, known to exist at no more than five locations, and extreme fluctuations in the number of mature individuals. Appropriate measures should be taken to protect this species, such as additional survey efforts and monitoring of extant populations.
We sampled female Nannopus palustris Brady, 1880, from the North Inlet Estuary, South Carolina, U.S.A., monthly for a year to determine seasonal variation in a female polymorphism previously described. Two fat morphs (one with a notched and one with a straight basal region of the terminal seta of the caudal ramus) and a thin-bodied, previously unknown, morph were present sympatrically in different relative frequencies throughout the year. Total abundances peaked in February and were lowest in the summer. All three morphs differed significantly in width, but only females with notched terminal setae were significantly shorter in body length than thin and fat females. Genetic analyses of mitochondrial (cytochrome b) and nuclear (D3 expansion segment of 28S rDNA) genes demonstrated that the females with notched terminal setae were distinct from the thin and fat females with straight terminal setae, and the latter two shared common alleles. Concordance between mitochondrial and nuclear gene trees supports that notched females are a separate species from the thin and fat forms with straight terminal setae. We have yet to find a male with a notched basal region of its principle terminal setae or any male sharing alleles in common with notched females.
We studied feeding site selection and impacts by benthic fish (flounder and skates) on the amphipod Corophium volutator, an ecologically-important species in muddy intertidal communities. We determined that benthic fish foraged mainly in areas that had high densities of amphipods, on a mudflat in Nova Scotia, Canada. This observation was based on recording sediments displaced by benthic fish in areas where samples of amphipods also were taken. From gut-content analysis, we found that benthic fish fed almost entirely on C. volutator, and most consumed smaller amphipods than expected based on samples of amphipods collected from the substrate. Benthic fish also fed on male amphipods more than expected. We determined that daily foraging pressure by benthic fish on amphipods was low (about 0.3% per day) by measuring the new appearance of feeding traces made by fish. Nonetheless, fish are expected to have substantial impacts on demography of C. volutator due to the length of the fish foraging season and because fish appear to contribute to extreme female-biased sex ratios typically seen in this species.
A new genus and species of gnathiid isopod, Tenerognathia visus, is described on the basis of three male specimens sampled from coral rubble infauna in the Ryukyus, Japan. The dorsal view of the gnathiid, having small mandibles, large eyes, and a slender body, is more similar to larvae than adult males of other gnathiid species. The pylopod of Tenerognathia resembles that of Caecognathia, Elaphognathia, and Gnathia in the number of articles, but is distinctly more elongated. Morphologies of the mandibles, cephalon, and thorax are compared with these three genera.
Stimuli involved in sexual attraction to and recognition of receptive females by males were investigated in the shrimp Palaemonetes pugio. Newly molted, prespawning (postmolt parturial) females are receptive and attractive to males. Males that make physical contact with a postmolt parturial female, usually with the long antennal flagella, react immediately and dramatically with copulatory behavior. Experiments using females sealed in glass containers suggest that visual stimuli are not important in mate recognition. To test the role of cuticular texture in sex attraction, males were exposed to females and males of different molting and reproductive states; copulatory responses were recorded. Males copulated with postmolt parturial females in a majority of replicates. Newly molted but nonparturial females, as well as newly molted males, evoked little copulatory response from males. Thus, the soft texture of a newly molted cuticle does not appear important in sex attraction. The duration of attractiveness of postmolt parturial females was measured by exposing them to males at known intervals after molting. There was a steady decline in attractiveness, with copulation in 80% of females within 2 h of the parturial molt, decreasing to 30% in 6–8 h after the molt. The behavioral evidence suggests that males are responding to an insoluble substance (contact sex pheromone) in or on the exoskeleton of the postmolt parturial female. Attempts were made to remove the substance mechanically by rubbing the exoskeleton of postmolt parturial females with small latex sponges, but males showed no response in bioassays. Cuticular hydrocarbons, glycoproteins, or other compounds secreted on the surface through pore canals or tegumental gland openings might serve as sex attractants. A contact sex pheromone in P. pugio and other carideans might also be a substance involved with sclerotization, calcification, or other such chemical changes occurring in the cuticle of the early postmolt parturial female.
The relationship between rhythms of circadian periodicity (i.e., from 20 to 28 h) and ultradian periodicity (i.e., less than 20 h) was studied in the burrowing decapod Nephrops norvegicus at the level of its cardiac activity. Animals were kept over a month under constant darkness (DD) interrupted by a few days of light-darkness regime (LD) at the beginning of the experiment. Time series (beats per 10 min) were subdivided into stages of similar numbers of days. A general mean waveform was computed per stage by averaging 24 h segments of different time series per corresponding 10 min intervals. Marked fluctuations were observed at the beginning of tests in DD, being disrupted during animals' exposure to LD. Fluctuations progressively recovered over following stages of DD. The activity part of a rhythm (α) was computed in mean waveforms of different time series per each stage. Resulting values were averaged at corresponding stages. A significant increment of mean α was observed from DD to LD, decreasing over the following prolonged DD exposure. Periodogram analysis was used to assess periodicities of time series at each stage. Fourier analysis was undertaken to assess the transformation of cardiac rhythms over consecutive stages not only in terms of periodicity but also as amplitude. Both analyses showed the presence of different circadian and ultradian (i.e., 12 h and 18 h) rhythms varying in their amplitude at different stages of testing. A preponderance of time series with ultradian periodicities took place in the first stage of DD. Under LD, the number of time series showing 18 h periodicity increased, but their amplitude of fluctuation was lower compared to the previous stage. In contrast, the circadian periodicity present in the first stage of DD disappeared in LD, to be restored over prolonged DD exposure. Present results suggest that a disruption of the circadian rhythm in cardiac activity generated ultradian periods when controlling oscillators became uncoupled. Results are discussed in the context of the ecology of the species, and a model based on the phase decoupling of circadian oscillators is presented to account for the generation of ultradian 12 h and 18 h periodicities.
The purpose of this study was to determine whether female American lobsters (Homarus americanus) inhabiting different offshore areas reached sexual maturity at different sizes. We determined the sexual maturity of 734 lobsters captured in three different offshore locations (North: Georges Bank and offshore Gulf of Maine; Middle: southern New England shelf and slope and; South: offshore Rhode Island to New Jersey) using a combination of methods including abdominal width : carapace length ratios, cement gland examination, and ovarian staging. Lobsters that experienced the most degree-days > 8°C (dd) reached sexual maturity at smaller sizes. The size at which 50 percent of the lobsters were mature was 79 mm CL for the South (annual dd = 808), 82 mm CL for the Middle (999 dd), and 92 mm CL for the North (234 dd). This regional difference in size at maturity was also manifested in the average size, and range of sizes, of berried females captured in each location. These data will likely be of use when developing appropriate regulations for managing the offshore fishery.
The stygobitic crayfish Procambarus cavernicola and Procambarus oaxacae reddelli and the epigeal crayfish Procambarus olmecorum were maintained in laboratory conditions in order to compare their oxygen consumption rates by measuring the decreasing oxygen concentration. These closely related species belong to the same subgenus and live in nearby caves and surface streams located in the same karstic region found in northern Oaxaca, Mexico. The consumption rates were monitored in laboratory conditions during fifteen hours in water maintained at 20°C without food. Significant differences among the species were found. Although these species live in similar conditions of total darkness during their life cycles, P. cavernicola had the higher oxygen consumption rate; this is a result of being slightly conditioned to oxygen partial pressures of the experimental bottle. Procambarus oaxacae reddelli showed a lower oxygen consumption rate strongly correlated to the oxygen partial pressure of the water. The epigeal P. olmecorum was used as a control and showed a consumption rate slightly conditioned to oxygen partial pressures that was lower than the consumption rate of P. cavernicola. The differences in consumption rates between the stygobitic species in relation to the characteristics of the caves where they live and their adaptation degree to cave life are discussed.
Ambiguity in the purported diagnostic attributes utilized to identify species of the poorly known “Troglopagurus group” of the hermit crab genus Diogenes prompted a review and critical reassessment of the morphological characters used to differentiate the nine recorded taxa. For this, an analysis was conducted based on 122 individuals including the majority of type specimens. The data clearly showed that the intraspecific variation inherent in these taxa rendered the presumably diagnostic characters ineffective in differentiating among the seemingly distinct species. As a result of the investigation, Diogenes setocristatus and Diogenes stenops were found to be junior subjective synonyms of Diogenes jousseaumei. Similarly, Diogenes platyops proved to be a junior subjective synonym of Diogenes jubatus. The incorrectly interpreted D. manaarensis was reappraised, based on the remaining syntype, herein designated the lectotype, and variations in the morphologies of the inadequately described D. persicus and D. mercatoris were explicated. Diogenes crosnieri has been retained as a valid taxon in the “Troglopagurus group”, at least until such time as more material becomes available.
A presumed hybrid mud crab of the genus Scylla was examined. The presumed hybrid could not be easily separated morphologically from the three Japanese Scylla species, S. serrata, S. paramamosain, and S. olivacea. An analysis of the first internal transcribed spacer (ITS-1) of the nuclear DNA revealed that the hybrid carried genomic DNA from both S. serrata and S. olivacea. Analysis of the maternally inherited 16S rDNA of the mitochondrial DNA demonstrated that the presumed hybrid carried S. olivacea mtDNA. Based on these results, we conclude that the examined animal is indeed the hybrid offspring of a female S. olivacea and a male S. serrata. The degree of genetic isolation among these species, and the possible causes of hybridization are discussed.
Reconsideration of all fossils formerly referred to the Trapeziidae Miers, 1886, suggests that both the Trapeziidae and the morphologically similar Domeciidae Ortmann, 1893, are represented in the fossil record. Two fossil species formerly considered to be trapeziids are referred to the domeciid genus JonesiusSankarankutty, 1962. New combinations include J. oligocenicus (Beschin et al., 2001) and J. planus (Müller, 1996); thus, the recognized geologic record of the Domeciidae extends from the Oligocene to Recent. The Trapeziidae is known from three Eocene genera, including the new genus and species described here, Archaeotetra inornata. Other Eocene occurrences include two species of EomaldiviaMüller and Collins, 1991, and one species of TetraliaDana, 1851. A few Miocene species of TrapeziaLatreille, 1828, and a Pleistocene occurrence have been reported. Members of both families are symbiotic with cnidarians, and this relationship appears to have been established by the Eocene in the case of the Trapeziidae and the Oligocene for the Domeciidae, based upon the tropical to subtropical distribution and the occurrence of the fossils in each family in coral-bearing rocks. Coevolutionary processes appear to have resulted in high degrees of specialization in some genera within the Trapeziidae.
Male sand-bubbler crabs Scopimera globosa perform a waving display during their reproductive season, but waving is not used when a male is paired with a female. A male grasps and brings a female into his burrow for mating. We conducted this study to clarify the function of the waving display of S. globosa. The frequency of waving was correlated with male size, and males that paired successfully underground waved significantly more often and were significantly larger than their neighbors. Females that were released in front of waving males either approached or fled from the waving male or they made no response. All the females that approached waving males completed underground pairing without resisting capture by the male, but most females that fled or did not respond resisted capture. Females that approached waving males had more developed ovaries compared to females that fled. These results suggest that waving in S. globosa functions as part of courtship behavior and that waving males detect females with ripe gonads according to how the female responds to the displaying male.
The complete larval development of a terrestrial crab from West Africa, Cardisoma armatum Herklots, 1851, was studied in laboratory rearing experiments carried out at various salinities ranging from 0.2‰ to 45‰. Six zoeal stages and one megalopa are described and illustrated. Our experimental results showed that zoeal stages of C. armatum are fairly euryhaline, zoea I to IV tolerating a salinity range of 15–45‰, and 15–35‰ during later development. However, salinity 15‰ tended to cause higher mortality and a significantly delayed development in most stages, while 25‰ allowed for maximum survival through metamorphosis. These observations suggest that C. armatum follows a limited export strategy, where the adults may live in brackish or even freshwater habitats, while a successful larval development is possible only in estuarine or coastal waters with higher salinities, presumbly with an optimum in the lower parts of estuaries with 25‰. Before this study, only an incomplete description of the first zoeal stage of C. armatum was available, and complete larval development had been known only for C. carnifex and C. guanhumi. In the present paper, the larval morphologies of these three congeneric species are compared. Within the Gecarcinidae, the complete larval development has been described also for Discoplax hirtipes and Gecarcinus lateralis, while only data for the morphology of the first zoeal stage are available for the other two genera of this family, Epigrapsus and Gecarcoidea. Hence, there are at present no sufficient data, in particular on megalopal morphology, to allow for conclusive intergeneric comparison and identification of familial characters. Gecarcinid zoeal morphology, as far as this is known, is briefly discussed in relation to that in other grapsoid families.
Numerous taxa have the ability to autotomize parts of their bodies to increase survivorship in dangerous or stressful situations. Effects of autotomy on a surviving individual's subsequent ecological function is not well understood for most species. In this study, we provide the first quantification of autotomy patterns within a population (frequency of injured individuals) and within an individual (frequency of missing pereopods, or limbs) of the Asian shore crab Hemigrapsus sanguineus. This crab, member of the family Grapsidae, is a recent introduction to the eastern coast of North America. Of 95 crabs sampled, 42% were missing at least one limb, with larger crabs missing more limbs than smaller crabs. Of the sample, 16% were missing at least one cheliped, with chelipeds more likely to be lost than walking limbs. These rates of limb loss are comparable to those of other crabs in their native ranges. Limb loss patterns affected feeding rate and size of prey consumed. Crabs missing one cheliped fed slower than those with both chelipeds, but consumed a similar ratio of small to large prey as crabs with both chelipeds. Crabs with no chelipeds, which fed at the slowest rate, consumed a larger ratio of small to large prey than crabs with either one or two chelipeds. These feeding results suggest that frequency of limb loss in H. sanguineus autotomy levels has potential to affect several population- and community-level processes.