Molecular data are used to test whether (1) Phreatoicidea are the earliest derived living isopods, and (2) the long-tailed isopod morphology is the derived condition within the Isopoda. Small and large subunits of the mitochondrial ribosomal genes (12S- and 16S rDNA), and cytochrome oxidase c subunit I (COI) are used as a case study for exploring the boundaries of applicability of these genes at this taxonomic level. I evaluate three data sets, compare three differently weighted alignments, test data partitions for congruence and phylogenetic structure, and evaluate the topologies of individual and combined data partitions. The 12S- and 16S rDNA partitions are not incongruent. However, the incongruence between ribosomal and COI partitions is significant. The study provides new data for addressing generic, familial, and subordinal relationships of this large, morphologically and ecologically diverse taxon. For the three data sets investigated here, the addition of taxa increases bootstrap values at nodes, more nodes have bootstrap support greater than 50%, and clade topologies are comparable when taxa are added. These mitochondrial genes corroborate isopod clades previously recognized on morphological grounds, and in other instances, suggest relationships not previously proposed, i.e., valviferans had a sphaeromatid ancestor, and oniscids and sphaeromatids may be more closely related than previously thought.

We examined the distribution of 44 morphological characters for 16 extant species of an ostracode genus, Gomphocythere, in Africa, to test hypotheses concerning character development and speciation patterns. Using heuristic searches conducted with the phylogenetic reconstruction program PAUP (beta version, 4.0), we found 2 trees of 98 steps (CI = 0.56). The skewness of tree length distribution reveals significant phylogenetic structure in the data. Nodes are supported by 1 to 11 character-state changes, and these character changes are sometimes reversed or paralleled elsewhere, accounting for much of the homoplasy in the reconstructions. By systematically removing both hard- and soft-part characters in separate analyses, hard-part characters were found to be far more homoplasious in their distribution across the phylogenetic tree, while soft parts are minimally homoplasious, suggesting that they are far more conservative while the hard parts are more prone to ecophenotypic variation. This phylogeny provides the basis for evaluating speciation mechanisms and the role of ecological factors in the diversification of ostracodes in this lake system.

During an ongoing systematic revision of the Decapoda Grapsoidea (here defined as including the families Gecarcinidae, Grapsidae s. str., Plagusiidae, Sesarmidae, and Varunidae; see Schubart et al., 2000a), it became evident that adult and larval morphology of two Central American genera, Glyptograpsus and Platychirograpsus, differs greatly from that of all other genera within this superfamily. Several important morphological characters are shared by these two genera and represent synapomorphies when compared to the other grapsoids. Both of these genera lack a pleurobranch on the sixth thoracic segment. Adult males of Glyptograpsus and Platychirograpsus are all strikingly heterochelous with the major chela being conspicuously flattened anteriorly and showing a subproximal articulation with the carpus. The distal portion of the male gonopod is uncinate, with a narrowed, elongate terminus. The anteriormost portion of the sternum consists of a narrow, fused sternite terminated in a distinctly flanged tip inserted between the mouth appendages. The male abdomen exhibits immobility in the joints between segments 3 to 5 and very limited mobility in the joint between segments 1 and 2. Zoeae of the two genera show a 1,2 setation pattern on the maxillar endopod. A molecular phylogeny of the Grapsoidea, based on 16S mtDNA and including type genera of the five recognized families, confirms that the species of Glyptograpsus and Platychirograpsus together form a well-defined monophyletic unit that is distinct from all other taxa within the Grapsoidea. We therefore describe a new family, the Glyptograpsidae, to accommodate these two genera of crabs.

The present investigation was undertaken to study the effect of an abrupt change in the salinity of the medium on the oxygen consumption and ammonia-N excretion of the marine penaeid shrimp Metapenaeus monoceros (Fabricius). Results showed that in both low-saline (5‰) as well as high-saline (35‰) acclimated shrimps the respiratory rates were significantly lower in midrange salinities (20‰ and 25‰) and significantly higher in both low (5‰, 10‰, and 15‰) and high (30‰ and 35‰) salinities. A significant increase in ammonia-N excretion was observed when high-saline acclimated shrimps were abruptly exposed to different grades of low-saline media. Exposure to different grades of high-saline media on the other hand induced a significant decrease in ammonia excretion rate of low-saline acclimated shrimps. The O:N ratio (ratio of oxygen consumed to nitrogen excreted in atomic equivalents) showed a decreasing trend when the high-saline acclimated shrimps were abruptly exposed to low-saline media, indicating a shift towards protein dominated metabolism. A reverse trend could be observed in the O:N ratio when the shrimps were exposed to high-saline media indicating a shift towards lipid dominated metabolism in high salinities. Thus, there appears to be a shift in energy substrate utilization in these shrimps from protein dominated metabolism in low salinities (5‰, 10‰, 15‰ and 20‰) to lipid/carbohydrate dominated metabolism in high salinities (25‰, 30‰ and 35‰).

To investigate factors associated with the distribution of an intertidal crab, Hippa pacifica Dana, which is common in the swash zones of reflective subtropical and tropical sandy beaches, we examined the effect of sediment size on burrowing rates of a wide size range of individuals. We also examined aspects of swash behavior in field conditions, including drift time, distance and velocity of individual crabs. Hippa pacifica burrowed very rapidly (in 0.3 to 2.7 s) in laboratory and field conditions. Burrowing time increased significantly with increasing crab size in all sediments tested but did not differ between male and female crabs nor between ovigerous and non-ovigerous crabs. There were no significant differences in burrowing times among five sediments ranging from very fine sand to gravel, suggesting that this species is a sediment generalist whose distribution is not limited by sediment size. Individual crabs released in the swash zone of a reflective beach oriented, swam and/or drifted for 1.2 to 3.8 seconds before contacting substrate and burrowing. Drift times were similar for all sizes of crabs. However, drift distance (ranging 0.10 m to 1.16 m) and drift velocity (ranging 0.11 m/s to 0.45 m/s), decreased with increasing crab size, suggesting a possible mechanism for size-specific zonation patterns reported in this species. Burrowing times observed in H. pacifica in this study were faster than reported for other sandy beach macrofauna, including tropical forms. This burrowing ability, in combination with the characteristics of substrate generalist and well-oriented swash behavior, appear to be a key to the ability of H. pacifica to inhabit reflective coarse sand beaches.

In South Carolina, two species of fiddler crab, Uca pugilator and U. pugnax, often feed in droves on the sand flats of smooth cordgrass salt marshes. Another fiddler crab, U. minax, does not drove, but large males of this species occasionally move onto sand flats and prey on members of the other smaller species. Successful predatory attacks entail a pounce, entrapment of prey in ambulatory appendages, reorientation of the predator to the supine position, maneuvering of the prey between the dactyl and propodus of the major cheliped, killing the prey by piercing or crushing its carapace with the major cheliped, and consumption. Females are successfully attacked with higher frequency than males. The frequency of predatory attacks declines exponentially as the composition of droves becomes biased towards larger males. This may indicate that predators face injury when attacking large males because only males possess potentially defensive claws and claw length increases with the square of body width. Uca pugilator individuals form pods in response to the approach of a predator. Pods are tight clumps of fleeing individuals that may function as mini-selfish herds. Pod composition is biased towards individuals most susceptible to U. minax predation, females and males of small body size, suggesting that pod formation is a selectively advantageous behavior.

Fiddler crabs Uca uruguayensis were collected monthly in Punta Rasa, at the southern end of the Samborombón Bay, Río de la Plata, Argentina, from February, 1995, to March, 1996. Throughout the study, 1,115 of 12,033 crabs (9.3%) were infested by different developmental stages of the branchial bopyrid Leidya distorta, which is herein reported for the first time as infesting U. uruguayensis. The distribution of this parasite, previously known from New Jersey to Rio de Janeiro, is now extended even farther south, to the mouth of the Río de la Plata. Prevalence of L. distorta increased as a function of crab size. The newly settled cryptoniscus larvae were found in the space between contiguous gill lamellae after invading a previously uninfested branchial chamber. The cryptoniscus larva transformed into an early juvenile and, after molting one or more times, migrated to the roof of the branchial chamber, where it grew and finally reached the ovigerous condition. Female parasites usually carried cryptonisci or males, eventually both, on their bodies. Males were found in different positions on the females as the latter developed. Crabs housing a mature female parasite frequently bore an unpigmented area on the lateral wall of the branchial chamber. An additional faded area was sometimes observed on the bottom of the eye orbit. Adult female parasites usually produced a subtle lateral swelling on the carapace of the host, this deformation being more marked in smaller crabs than in larger ones. The major chela of the male crabs parasitized by adult females was, on average, 6.5% shorter than that of unparasitized ones. Alterations of the gills of the host were noticed: the adult female parasite had a strong dorsal carina that fitted between the fourth and fifth gills of the crab, displacing them laterally and making contact with the floor of the branchial chamber. The inner surface of the crab branchiostegite bore a large horizontal vessel from which the parasite presumably obtained hemolymph. Besides the bopyrid isopod forming the subject of this report, we found 61 crabs harboring a nematode larva, identified as Skrjabinoclava sp., among the internal organs of the crab.

The structure of a decapod crustacean community on a littoral detritic bottom (coarse sand, fine gravel, Amphioxus sand, and abundant bioclastic remains) of Southern Spain (Barbate Bay, near the Straits of Gibraltar), at 15–24-m depth, from October 1993 to August 1995, has shown annual changes. These changes could be due to natural factors (river flow as consequence of differences in pluviometry between years) and anthropogenic disturbances happening in front of the sampling area during a second period (namely the dredging and enlargement of the harbour and the restoration of a beach), which affected directly or indirectly (through the movement of particulate matter) the structure of decapod community. As a result, there was a decrease in the total abundance and in the number of specimens of the dominant species (mainly Diogenes pugilator and Galathea intermedia) some of them associated with seaweed (G. intermedia and Pisidia longicornis), a reduction of the seasonality, and fluctuations in the values of the richness and diversity indices. However, before and during the disturbances, the dominant species remained the same, with only slight modification in the dominance order. In addition, the accumulative total annual values of the diversity indices are very similar. All these results could mean the existence of higher resistance to disturbances (none strong) in the decapod community from hydrodynamic areas. On the other hand, the strong currents increase the dispersion of the sediments, reduce the turbidity, and facilitate a more rapid return to the previous conditions, increasing the elasticity of the system, in which the decapod community presents a cyclic structure.

Migrations play a key role in the life history of the spider crab Maja squinado (Herbst, 1788) and affect fishery catches. Migrations involve important changes in depth and in the environment. Ultrasonic telemetry has a number of drawbacks due to the difficulties in the continuous tracking of crabs while they are moving to deep waters. The recent introduction of electronic data storage or archival tags permits continuous monitoring of depth and temperature in crab's habitat and reconstruction of the movement patterns using baseline data on habitat characteristics. On the Galician coast (NW Spain) we calibrated and used electronic tags as a tool to study spider crab migrations. In the summer of 1996, 17 crabs were tagged with both ultrasonic transmitters and electronic tags. Tracking was carried out discontinuously at intervals of approximately 1 wk. We obtained a recapture rate of approximately 70%. The information provided by telemetry and electronic tags indicates autumn migrations along the bathymetric gradients (from <10 m down to 100 m) within short periods (mean = 5.7 d, range = 1.3–13.6). During these movements crabs travel through habitats characterized by different temperatures and substrates. Bathymetric and oceanographic data as well as localisation records from the electronic tags make the reconstruction of the animal tracks possible.

The marsupial development of a population of Americamysis (= Mysidopsis) bahia from the Gulf of Mexico was examined at 16°C, 20°C, and 29°C from oviposition to the juvenile stage. Three phases of development, divided into five stages, occurred during in vitro culture of larvae. The embryonic phase (Stage 1) is spherical and surrounded by the egg membrane. The nauplioid phase begins with hatching from the egg membrane and consists of an early (Stage 2) and late (Stage 3) stage. The early nauplioid stage, which is divided into three substages, elongates into a comma-shaped larva and ends with the appearance of thoracic chromatophores. Stage 3 begins with the formation of eye pigment and ends with the shedding of the naupliar cuticle. The subsequent postnauplioid phase has two stages. Stage 4 is characterized by the formation of a yolk protuberance anterodorsal to the carapace. Stage 5 begins with enclosure of the yolk in the carapace and ends with release of the larvae from the marsupium and a molt to the juvenile stage. Following liberation of young at night, the female molts, and usually mates and extrudes another brood of eggs. Survival rates of A. bahia larvae in vitro increased with age and with decreasing temperature. Average brood durations of larvae were 15.5 days at 16°C, 10.4 days at 20°C, and 4.6 days at 29°C. Observations of brood release, spatial organization within the marsupium, and adoption of larvae are discussed.

The larval development of Megalobrachium roseum is completely described and illustrated on the basis of laboratory-reared material obtained from four ovigerous females captured on rocky bottoms of shallow waters in the southeastern Caribbean Sea. Megalobrachium roseum hatches as a prezoea of less than 120 minutes duration, and then molts through two subsequent zoeal stages of 5–7 and 6–8 days duration, respectively, at 25°C and 37‰ salinity, before attaining megalopal stage. Morphology of the zoeal and megalopal stages of M. roseum is compared with those of the three other species of Megalobrachium for which the larval development has been described (i.e., M. pacificum, M. poeyi, and M. soriatum).

The life history and population structure of the amphipod Synchelidium lenorostralum were studied monthly for one year in the sandy shore at Dolsando, southern Korea. The life-history pattern was annual and iteroparous, with two dominant recruitments in fall (October to December) and spring (March to May). The sex ratio was female-biased, especially during breeding periods. The maximum size of females was 10.8 mm and 1.4 times larger than that of males. The mean body length of adults and brood size were greater 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 of stage I was more than 0.04 mm³ in December and March, but in other months it was less than 0.03 mm³. Egg volume was positively related to body length of ovigerous females and increased significantly at the phase between stage I and II. However, no significant relationship between egg volume and brood size was found. At any given female size, egg volume was significantly higher in the fall breeding than in the spring, whereas brood size was not different between the two main breeding periods, suggesting higher reproductive effort during the fall breeding period.

Several peracarid crustaceans have been shown to engage in extended maternal care for their growing offspring after the juveniles hatch from the brood pouch of the female. In this study, we describe the maternal care of the epibenthic gammaridan Parallorchestes ochotensis Brandt and examine its ecological implications. The juveniles stayed in the female's expanded brood pouch for at least seven weeks after hatching. The duration of extended maternal care of P. ochotensis was comparatively longer and the growth of P. ochotensis juveniles slower than reported for other epibenthic peracarids. The juveniles molted at least twice whilst in maternal care. This species probably has an annual life span, and they reproduce only once a year. In P. ochotensis, maternal care was shown to constrain juvenile growth in the experimental predator-free conditions, contrary to other epibenthic peracarids. Most epibenthic peracarid species with extended maternal care are suspension feeders, but P. ochotensis is an herbivore so probably maternal care of this species limits juvenile feeding opportunities and results in a decrease of juvenile growth. However, where normal predation exists, maternal protection contributes significantly to juvenile survival. In P. ochotensis, to enhance relatively low fecundity in conditions where predation pressure is high, extended maternal care for relatively long periods is necessary to protect offspring even if it constrains juvenile growth.

The sesarmid Perisarma guttatum is the most abundant crab species inhabiting the lower mangrove areas at Inhaca Island, and presumably an ecologically important species in this habitat. Among the scarce available information on its population ecology, this species is known to follow a semilunar rhythm of larval release, with breeding probably extended year-round. In this study, a population of P. guttatum was examined, from which estimates of sexual maturity were carried out for both sexes, and breeding activity was monitored to describe short-term variation of reproductive intensity. In an attempt to relate reproductive cycles with recruitment patterns of young, a systematic random sampling design was used to quantify and describe the juvenile population. Reproductive parameters in adults and density estimates for juveniles were obtained from samples taken at 4-d intervals over a 3-mo period. Reproductive activity increased over the study period. Females released larvae around the new and full moon, but lunar variation of the ovigerous ratio with peaks preceding full moon periods indicated that different breeding groups may account unevenly for the reproductive output of the population. Very young recruits made up the larger fraction of the juvenile population, and their density increased from the beginning to the end of the sampling season. Density variation pattern of first-crab stages followed fortnight cycles, but slow growth prevented recruitment pulses to be tracked in size-frequency distributions. Polymodal distributions corresponded to recent recruits and older juveniles originating from previous settlement seasons. Growth rates of identified age groups suggest that sexual maturity in females is likely to be achieved after 2 years or more.

The reproductive cycle and recruitment period of a ghost crab population from Ubatuba, São Paulo, Brazil were investigated by means of examining the developmental stages of gonads of breeding crabs and the ingress of young recruits to the studied population. Monthly collections over a one-year period were carried out during nocturnal low-tide periods at “Vermelha” beach. The morphology of the abdomen and pleopods was used for sex determination. All captured crabs were measured for carapace width and dissected for the determination of the development stage of the gonads. A total of 582 specimens was captured: 271 males, 241 females, and 70 juveniles. Size ranged from 8.5 to 37.5 mm for males, from 9.5 to 39.2 mm for females, and from 5.8 to 12 mm for early juveniles. Median size of males and females did not differ statistically. The frequency of ovigerous females was markedly low. The onset of sexual maturity in females is achieved at around 23 mm of carapace width. Mature females with advanced gonad stages were not recorded from May to September. Recruitment of young was highest during summer, but the presence of early and late juvenile specimens throughout the year indicates that continuous recruitment is taking place in the studied population.

Morphological variation in resting-egg pattern is examined in 43 populations of Chirocephalus diaphanus carinatus from the Balkan area and is discussed in relation to geographic location. In spite of a great variation in male and female key-characters, even at the individual level, distinct and apparently constant resting-egg patterns was revealed for each population, irrespective of distribution. Such a contrasting situation stresses the need for further research at genetic or molecular level in order to ascertain the validity of the subspecies ranking, previously put into question by Belk and Brtek.

Hyalella azteca is a species complex distributed in North, Central, and northern South America. The identity of the species has always been a problem, especially because the original description by Saussure (1858) from a “cistern” in Vera Cruz, Mexico, is poor, and the figures are not clear. Since then, mention of the type material or specimens from the type locality has not been made by investigators using the name H. azteca. Ecological and genetic information available today suggests that there are several species in the complex commonly referred to as H. azteca. The subtle morphological differences among the populations have made the problem of defining these species very complicated. To aid in this process, we present here the morphological description of H. azteca based on the syntype series established by Saussure and deposited in the Muséum d'Histoire Naturelle, Ville de Genève, Switzerland.

The Asian shore crab Hemigrapsus sanguineus is recorded for the first time in two European localities, Le Havre in France and the former estuary “Oosterschelde” in the Netherlands. While breeding populations occur in the former, only two male specimens were found in the latter. In both places, this alien species was mixed with the common shore crab Carcinus maenas.

The amphipod Crangonyx floridanus and the isopods Caecidotea racovitzai and Asellus hilgendorfii were discovered in the Sacramento/San Joaquin Delta, California, U.S.A. We applied Chapman and Carlton's (1994) criteria for determining introduced species to test whether these species are non-indigenous to the delta. The majority of the attributes scored positive, indicating that these species are non-indigenous. These populations appear to be firmly established, as they occurred at a variety of freshwater wetland habitats throughout a one-year study. The species are briefly described, and distinguished from similar native and non-indigenous species known to exist in the surrounding area.

Notopoides latus is recorded from Ducie Island at the extreme eastern end of the Tuamotu-Mangareva-Pitcairn chain of island groups in the eastern South Pacific. Hence, N. latus is now known to be an Indo-Pacific species ranging from East Africa and the western Indian Ocean, through Indonesia and the Philippines to the Northwest and Central Pacific, to eastern Australia, Norfolk Island, and across to the eastern South Pacific. Henderson's original 1888 figure shows N. latus, in dorsal view, with an urn-shaped carapace rather than the symmetrically-ovate carapace seen in all modern figures. This puzzling anomaly has been resolved by examination of Henderson's type series, and other available material, showing that Henderson's artist had drawn his specimen with the carapace tilted backwards rather than in the conventional horizontal position. Henderson's figured male specimen in The Natural History Museum, London, is designated the lectotype.

We collected Nyctiphanes simplex in Barkley Sound, Canada (48°54′N, 125°6′W) between May and September 1998. This was during the most intensive ENSO (El Niño Southern Oscillation) event recorded and when southward current velocities were anomalously low. This is a range extension of about 330 km NNW of where N. simplex was collected previously by plankton sampling gear and about 65 km NNW of where it was found in fish stomachs. Animals ranged between 10 and 20 mm total length and were at various states of maturity. We present length-frequency and maturity stage distributions as well as length-mass relationships. Results from an ongoing herring diet monitoring programme showed that they did not feed on N. simplex.