Gill-cleaning mechanisms of the burrowing mud shrimp Laomedia astacina De Haan, 1849, were examined based on morphology and behavioral observations. The gill complement consists of 13 arthrobranchs and 5 podobranchs, with flattened gill filaments of the phylloid trichobranch type. Gill cleaning is based on passive mechanisms involving setal systems on the scaphognathite, epipods, setobranch, and pereiopodal coxae. Multidenticulate scaphognathite setae (MSS) bearing digitate scale setules project into the gill chamber, lying over gill filaments. Proximal setules of the MSS incline to the setal base while distal setules incline to the tip; the transition zone of setule inclination is marked with an annulus. Setiferous epipods on the limb bases, except on fifth pereiopods, are armed with serrate setae, which contact adjacent gill filaments and coxal surfaces. Multidenticulate setobranch setae are found only on the coxae of third maxillipeds, thus limiting their gill cleaning functions to the anterior gills. Pereiopodal coxae bear tufts of short serrate setae together with a few multiple double-prong setae that are morphologically atypical in decapods. Active gill cleaning by pereiopodal brushes, as in callianassids and upogebiids, and limb rocking, as in astacideans, were not observed. Among thalassinideans, gill-cleaning mechanisms of laomediids appear more closely allied to those of thalassinids than callianassids and upogebiids, whereas those of axioids possibly indicate an ancestral condition.

The mating behavior and season, with no form alternation, of the Japanese crayfish, Cambaroides japonicus (De Haan, 1841) (Cambaridae), was observed in Lake Komadome, Hokkaido, Japan, from 1993 to 1995. Mating pairs and females with spermatophores were found in September and October in all three years, when water temperature decreased from 20.0° to 12.5°C. Females spawn the following year, and there are six months between mating and spawning. The lengths of each mating pair were similar for both male and female. Mean carapace length in males was 21.7 mm (range: 18.6–24.9), and in females it was 20.9 mm (18.4–22.9). The male lies ventral side up below the female. The male does not use his chelae to hold the female, but rolls his tail over the abdomen of the female. Cambaroides japonicus is placed in the family Cambaridae. All members of Cambaridae in North America have form alternation (cyclic dimorphism), but C. japonicus exhibited no form alternation in its natural habitat.

The body size-specific fecundity of Scyllarides squammosus is described based on the numbers of eggs carried externally on the pleopods of “berried” (ovigerous) females collected during June 1999, at Maro Reef, located mid-chain in the Northwestern Hawaiian Islands (NWHI). Fecundity was positively and nonlinearly related to “tail” (abdomen) width (TW); fecundity ranged from 53,807 to 227,489 eggs in 43 females spanning 52–77-mm TW. The smallest berried female encountered at Maro Reef in 1999 was larger than the smallest berried female observed during most previous years' (1986–97) lobster research cruises. Fecundity of the median-sized (60-mm TW) female caught at Maro Reef in 1999 by the NWHI commercial lobster trap fishery was an estimated 89,660 ± 3,980 (SE) eggs. Brooded eggs averaged 0.67 ± 0.006-mm diameter (range: 0.61–0.77 mm), equivalent to 0.17 and 0.13–0.24 mg, respectively. Egg size was unrelated to female body size. Fecundity and egg size estimates and their body size relationships are briefly compared with other scyllarid lobsters.

The large percentage of nonovigerous adult female crabs in situ gave rise to the question of whether egg extrusion occurs annually in Dungeness crabs in Alaskan waters as is reported for lower-latitude populations. Accordingly, we studied seasonal variation in gonadal development for 280 male, nonovigerous female, and ovigerous female crabs, reared in flow-through tanks from October 1997 through October 1998. Gonadosomatic indexes (GSI) were determined monthly from March through October 1998 for nonovigerous females, ovigerous females, and males. Oocyte area was also measured for females over the same period. Approximately 10 crabs from each treatment group were sampled monthly. Male GSI increased significantly over time. Nonovigerous females had significantly higher GSI and oocyte areas than ovigerous females. The GSI in October decreased significantly from the GSI in September among nonovigerous females in the laboratory and field, suggesting resorption of gonads. Most mature females do not extrude eggs annually in southeastern Alaska; however, under laboratory conditions, some females can extrude eggs in consecutive years.

In coastal environments, salinity variations may affect phases in crustacean reproductive cycle. Brown shrimp Crangon crangon Linnaeus, 1758 (Decapoda) are known to undertake breeding migrations between the sea and coastal waters (lagoons, estuaries). After a major flooding, the salinity of the Vaccarès coastal lagoon (Rhône River delta, France) dropped from 15‰ to 5‰ in a few days and remained low during following years. The aim of this study was to assess the impact on this environmental change on the reproduction of brown shrimp. We first tested whether females C. crangon had the ability to become ovigerous at a salinity as low as 5‰. Furthermore, the question whether salinity had an impact on fecundity was addressed. Experiments in aquaria were carried out for 180 days in the laboratory, with three replicates at three salinities (5, 15, and 25‰ respectively), keeping local photoperiod and temperature. Mortality was significantly higher in tanks at 5‰ than in those at higher salinities. Females reared at 25‰ salinity started to become ovigerous after 32 days; at 15‰ ovigerous females were only recorded after 80 days. No female became ovigerous at 5‰. A brackish salinity (15‰) would delay ovarian development in C. crangon, whereas a low salinity (5‰) seemed to inhibit maturation. Fecundity was higher in females reared at 25‰ than in those reared at 15‰. Results are explained and discussed taking into account eventual trade-off between reproduction and maintenance activities. Experimental data suggest that a too-low salinity in brackish lagoons may affect reproductive success of migratory natant decapods, such as C. crangon.

The present study was undertaken to establish the effect of salinity and acclimation time on the oxygen consumption of juvenile white shrimp Litopenaeus vannamei through evaluation of the mechanisms involved in adjustments of respiratory metabolism during acclimation and the effects on the apparent heat increment (AHI). Four experiments were conducted to assess the effect of acclimation time on oxygen consumption of shrimp exposed to salinity changes between 30‰ to 5‰. The effects of a change of salinity were recorded immediately in the first hour and 24 h after change. The results showed that L. vannamei juveniles are well adapted to tolerate salinity changes when they are subjected to sudden change in salinity or are acclimated to salinity change. The effect of salinity on the apparent heat-increment coefficient (AHI-%) in shrimp acclimated over time was also tested. The fasting and feeding oxygen consumptions were increased according to a reduction in salinity, with high values in 5‰ and lower values in 30‰. Although at 15‰ salinity the animals require energy to maintain homeostasis, we believe the juveniles acclimated at that salinity could be more efficient than those acclimated at 5‰ or 30‰ salinity because in that salinity shrimp consumed 1.22 and 1.69 more food than that observed in shrimp acclimated at 30‰ and 5‰, respectively, and without an excessive increase in the costs associated with AHI-%.

The growth increment and molt frequency of the American lobster (Homarus americanus) ranging in size from 46 to 154 mm of carapace length (C_L) from the southwestern Gulf of St. Lawrence (sGSL) were investigated by tagging and trap studies. The main molting period for lobster in sGSL was from early July to early September. Evidence for two molting seasons was observed only for male lobsters in Malpeque Bay, Prince Edward Island, and Baie des Chaleurs (Northeastern New Brunswick), but there was little evidence of double molting (< 0.2%). Evidence of animals skipping their annual molt was observed throughout sGSL. The percentage of growth increment for lobsters of the same sex tagged in premolt was significantly less than lobsters tagged in postmolt. The lower average percentage of growth increment observed for lobsters tagged in premolt is believed to be related to tagging trauma which is likely greater for lobsters actively developing a new carapace prior to molting. Male lobsters had significantly larger molt increments than females. Comparison between Malpeque Bay and Baie des Chaleurs yielded significant differences in the growth for male and female lobsters but not for berried females. The lowest average percentage of growth increment (12%) was observed for berried females. Furthermore, no relationship was observed between the growth increment and C_L.

Study on the size at maturity of male American lobster (Homarus americanus) has traditionally been done based on a linear relationship between chelae size vs. body size assuming that a sharp change in slope occurs at onset of maturity. We analyzed this sexual dimorphism by standard log-linear transformations and bivariate allometric plots as well as by multivariate Principal Components Analysis (PCA) in order to verify the validity of this approach for determining size at maturity. These analyses showed that onset of maturity cannot be detected efficiently by claw morphometry because this secondary sexual character gradually changes from early juvenile stages, contrary to what has been believed. Observation of the presence of spermatozoa in the vasa deferentia (gonadal maturity) showed that 50% gonadal maturity occurred at 49.8 mm of carapace length for male lobster from the southern Gulf of St. Lawrence. However, gonadal maturity does not necessarily correspond to the ability to mate (behavioral maturity) in many crustacean species. Therefore, further studies are needed to assess the behavioral maturity to determine the size at maturity for male lobsters.

The major claw of male fiddler crabs, reaching up to 40% of the individual's total body weight, may impose a cost on males when escaping from predators. To test this hypothesis, 38 males (18 without the major claw) and 19 females were randomly captured and placed, individually, in a straight track. After a five-minute adaptation period, an observer walked toward the crab and triggered its escape reaction. Each crab was subjected to 10 trials with 5-minute intervals between them. The central area of the track was video-recorded with a camera from a height of 1.30 m, pointing to the ground at a 90° angle. Females ran significantly faster than males with claw, but the escape velocity of males without claw did not differ significantly from that of intact males or females. Speed was strongly correlated with air temperature. The distances at which males and females reacted to and hid from approaching humans did not differ. These results are discussed in an ecological and evolutionary perspective.

Coho salmon (Oncorhynchus kisutch) and rainbow trout (Oncorhynchus mykiss) are commercially cultured in net-pens in Onmae Bay, Onagawa, Miyagi Prefecture, Japan, for eight months from November to the following July. Eight monthly samples of five rainbow trout and three bimonthly samples of five coho salmon were taken from two adjacent net-pens in this bay to study the infestation patterns of salmon louse (Lepeophtheirus salmonis). The results indicate that (1) rainbow trout was highly susceptible to salmon louse, (2) coho salmon harbored only the adult and preadult stages of the salmon louse, (3) the parasite reproduced twice on rainbow trout during the study period, and (4) the prevalence and mean intensity of infestation increased steadily into the harvest time (in July) on both species of salmonids. It is concluded that, aside from the resistance of coho salmon to infestation by salmon louse, the farmers' practice of rearing only the young fish and harvesting the fish in less than a year of culture accounts for the mitigation of salmon louse problem in Japan.

The Rhopalophthalmus mediterraneus population of the Guadalquivir Estuary (SW Spain) was sampled monthly from January 1998 to December 1999. Density, population structure, brood size, and standing stock were recorded during both years. The estuarine population of R. mediterraneus was concentrated in the outer 20 km of the estuary. There were considerable seasonal changes in the mysid abundance, with minima observed in winter and maxima in spring and summer. Such spatio-temporal distribution seemed to be related to estuarine environmental conditions: salinity was primarily responsible for the horizontal distribution of the species within the estuary, while its seasonal trend was determined primarily by water temperature. The population was characterised by a clear dominance of adults on all sampling dates and sites, with females (66.8%, on average) significantly more abundant than males (23.8%, on average), and the proportion of adult males and females changed significantly among sampling sites, being higher at the outer area (ANOVA; SNK test, P < 0.01). Gravid females were collected throughout the year, with maximal reproductive activity occurring in spring and summer. The population has a complex life cycle, being probably multivoltine and iteroparous. The brood size was significantly dependent on female size and season. The mean length of adults of both sexes varied negatively with temperature: smaller sizes occurred in summer.

Diel, lunar, and seasonal abundance, as well as population structure, of the free-swimming stage of the pea crab Pinnotheres bidentatus Sakai, 1939, from tidal waters off the west coast of central Taiwan were examined. A total 5,123 specimens were collected from tidal waters of the Kaomei coastal flat. These crabs were found year-round but mostly during fall to early winter (October to December 1994 and September 1995), with a peak in early December 1994. Numbers of crabs dropped sharply in mid-December 1994 and remained low during the months of January to April 1995, with slightly increasing numbers during mid-May to September of the same year. Daily abundance of the crab appeared to be related to new and full moon phases, indicating a semilunar pattern of swimming activity. Moreover, pea crabs were only collected during nighttime flooding tides, suggesting a nocturnal swimming activity which may have advantages for avoiding fish predators. Size structure of the crab indicates that P. bidentatus has life-history characteristics of which males die in the hard stage and females subsequently lose their swimming hairs and become commensal with their host. The overall sex ratio was 1:1.3 (2,206 males and 2,917 females) and varied according to month and size. The continuous occurrence of small individuals (1-mm size class) year-round indicates a long period of recruitment which may be a consequence of the long reproductive period of P. bidentatus.

The inheritance of 65 RAPD markers obtained from 15 arbitrary primers has been tested in two sexual populations of the ostracod Heterocypris incongruens. The markers were selected using the criteria of reproducibility and banding-pattern clarity from the amplification products yielded by 40 primers. The expected inheritance model was inferred from the progeny banding pattern and tested with the appropriate statistics. All 65 markers followed a Mendelian pattern of inheritance and indicated that the Spanish and the Italian populations studied are genetically different.

Limited understanding of the morphological variation and genetics of the genus Lepidurus have caused confusion for workers attempting to determine North American species of this genus. In addition, preliminary culturing data suggests that food quality affects the form of structures previously used as specific characters. Morphological comparisons between Lepidurus packardi Simon, 1886, and the type material of L. couesii Packard, 1877, demonstrate that populations of Lepidurus occurring in the Sierra Nevada, the Cascade Mountains, and the Great Basin regions of northeastern California and south central Oregon, previously reported as L. couesii, “L. couesii-1”, or as the “Modoc Plateau Tadpole Shrimp”, conform to the L. packardi morphotype. The results of my work and King and Hanner's (1998) genetic data demonstrate the presence of a cryptic species within the L. packardi morphotype, described here as Lepidurus cryptus n. sp. Specific diagnoses and a key to North American Lepidurus are presented.

There is often more genetic diversity in a given ecosystem than is represented by current taxonomy. Historical patterns of isolation among populations play an important role in studying the variation in behavior, habitat, and other ecological interactions among different populations of a species or species group. Idotea balthica (Isopoda: Valvifera) is a common intertidal grazer of the North Atlantic which has been well-studied in Europe for intraspecific differentiation. Using DNA sequence data from a mitochondrial protein-coding gene (cytochrome c oxidase I), I studied the relationships among different populations of I. balthica in European and American coastal populations. It is apparent that there are at least three historically isolated populations of I. balthica on the North American coast, while the European Atlantic coast contains populations that are closely related to each other and to one of the North American populations. It appears that populations of I. balthica on the North American coast represent both recently arrived colonists from Europe as well as populations which have survived recent glacial maxima.

Two new hairy species of caprellid amphipod, Caprella monai and Caprella takeuchii, are described based on specimens from the Strait of Gibraltar. Caprella takeuchii was found on algae and intertidal sediment under rocks from Tarifa, Southern Spain, while Caprella monai was collected clinging to the hydroid Nemertesia antennina and living on sediments from Ceuta, northern Africa. The most outstanding characteristic for both species is the presence of dense setae along the body. Caprella takeuchii is very similar to Caprella acanthifera Leach, 1814, except for the presence of dense setae in the male and the differences in upper and lower lips. Caprella monai is closely related to the poorly known Caprella grandimana Mayer, 1882. In the present paper we also redescribe C. grandimana on the basis of specimens from the Strait of Gibraltar.

Amphipods in the genus Chelorchestia are inhabitants of marshes and semiterrestrial environments of principally tropical regions of the world. Only three species are currently assigned to the genus but many undescribed species apparently exist. Along the coasts of Florida and Louisiana populations of Chelorchestia have been known for some time, all presumably representing undescribed species. A population recently discovered living in oligohaline/freshwater swale habitat on Sanibel Island, Florida, has been compared with the two other described species and differs in several consistent ways, principally in the combination of fewer articles of the flagellum of antenna 2, short pereopods 3–5, absence of pellucid lobes on the female gnathopod 1, and the structure of the propod and dactyl of the male gnathopod 2. Notes on the other two species, C. costaricana (Stebbing, 1906) and C. vaggala (Bowman, 1977) are provided. Observations on other possibly conspecific populations of the new species occurring along the Gulf coasts of Florida, Alabama, Louisiana, Mississippi, and Texas and another undescribed species occurring in southeastern Florida are presented and discussed.

For two callianassid shrimps, Nihonotrypaea japonica (Ortmann) and N. harmandi (Bouvier), morphometric character variations [carapace length (CL), eyestalk width (EsW), cornea width (CoW), and rostrum angle (RA)] were examined based on the materials collected from sandflats in western Kyushu, Japan. Allometric relationships were established between each combination of two morphometric characters for each species, in which CL was fixed on the abscissa as a reference variable. The values of EsW and CoW linearly increase with the CL value, with the slopes similar for EsW between the two species and a steeper slope for CoW in N. harmandi. By using the combination of (CoW/EsW) ratio vs. CL and that of RA vs. CL, bivariate discriminant analyses were run to establish an appropriate function separating the two species in each combination. The relatively smaller cornea size in N. japonica and more acute rostrum angle in N. harmandi were confirmed as the two effective characters that separate the two species. On the basis of the overall misclassification probabilities, the linear discriminant function using (CoW/EsW) ratio and CL was regarded as best to correctly separate the two species for practical use.

Descriptions are provided for Athanas dentirostris, new species, and Chelomalpheus crangonus, new species, two alpheid shrimps collected from the burrows of the upogebiids Upogebia aff. takaoensis Sakai and Türkay, 1995, and Upogebia edulis Ngoc-Ho and Chan, 1992, respectively. Athanus dentirostris, known only from northern Vietnam, is unique among all Alpheidae in having the superior margin of the rostrum dentate. Adult males of C. crangonus are immediately recognizable by the peculiar, subcheliform first pereiopods, which show superficial resemblance to the chelipeds of Crangonidae.

A new family, Pylojacquesidae, is proposed for Pylojacquesia colemani, new genus and species. Although the new family, with its monotypic genus, exhibits characters of both superfamilies of the Section Paguridea, it is tentatively assigned to the Paguroidea until additional material becomes available that would permit a more detailed study. The new family Pylojacquesidae is diagnosed, and its type genus and species are described and illustrated. The possible phylogenetic relationships of the new genus are discussed. A key to all the families of hermit crabs is presented.