Ink particles injected into the hemolymph of the American lobster (Homarus americanus), spiny lobster (Panulirus interruptus), crayfish (Procambarus clarkii), and ridgeback prawn (Sicyonia ingentis) were rapidly removed from circulation, and most were sequestered within nodules in the gills. The morphology of the gills and the nodules were examined from the time of injection until the following molt. The process by which ink was cleared from the gills was the same in all four species. Nodules formed within 10 min after injection and were composed of hemocytes loosely attached to one another and binding small quantities of ink. Within one week, nodules became spherical and more compact with accumulations of ink surrounded by layers of flattened hemocytes. By one month, hemocytes in the nodules had degenerated leaving melanized masses which lay between the gill epithelium and the exoskeleton. Following molting, the gills of both trichobranchiate and dendrobranchiate species were clean or had very reduced numbers of nodules, and melanized masses were seen attached to the inner surface of the shed exoskeletons. A similar mechanism for cleaning the gills has been reported in crustaceans infected with parasites and in necrotic gill tissue caused by exposure to toxic heavy metals. We, therefore, suggest that the ability of the gill epithelium to wall off foreign material so that it is lost during the following molt is a general mechanism to prevent occlusion of the gill and maintain its role in ion regulation and respiration.

Although crayfishes can locomote effectively on land, their walking performance may be affected by ambient temperatures and by their body size and hydration state. We used a racetrack timing system and videotaping to monitor the speeds, stride lengths, and stride frequencies of Orconectes rusticus in relation to body mass at temperatures of 15, 20, 25, 30, and 35°C. We similarly evaluated the locomotor performances of crayfish subjected to desiccating conditions at 25°C. Speed increased significantly with body mass with a scaling exponent of 0.18. This resulted primarily from a significant size-related increase in stride length. Walking speeds were greatest at the intermediate temperatures (25 and 30°C). This relationship was almost entirely due to thermally dependent adjustments in stride frequency. The crayfish were relatively intolerant of water loss, and locomotion ceased at a mean loss of only 9% of their initial body mass. Walking speed decreased significantly with increasing water loss, due almost entirely to a progressive reduction in stride frequency. The risk of desiccation is a serious constraint to sustained terrestrial locomotion. This is especially true for small individuals, although the risk, relative to that of larger animals, is lessened somewhat by the shallow scaling of the speed versus mass relationship. Crayfish might also lessen exposure risk by restricting overland movements to favorable climatic conditions (i.e., moderate to warm temperatures and high humidities).

Preliminary studies have shown that males and females of the freshwater crayfish Parastacus brasiliensis (von Martens, 1869) have an intersexed internal genitalia characterized by the existence of genital ducts of both sexes that connect to a gonad with male or female components, according to the sex. To determine the type of sexuality of this species, specimens (n = 92) from 11.7 to 40.0 mm carapace length were collected at Mariana Pimentel municipality, Rio Grande do Sul, Brazil (30°20′39″S, 51°22′39″W). Anatomical and histological analysis of the gonads disclosed the existence of three sexual forms: (1) intersexed males (n = 36), (2) transitionals between male and female sex (n = 8), and (3) intersexed females (n = 48). The transitionals present the following common morphological features: both genital apertures are present, but the female apertures are closed, as is usual in males; coexistence of oocytes and testicular acini in the same gonad (ootestis); and a longitudinal collecting tubule, large in diameter in the testicular region. The ovarian component of the gonad includes previtellogenic and primary vitellogenic oocytes. Of the 44 individuals classified as males by the analysis of the aspect of the genital apertures, 18.2% were transitionals, suggesting the existence of primary males that never change sex and a sexual system that is known as partial protandry. The existence of small females suggests that some females never go through a male phase. The histology of the gonads and genital ducts is described, and the germ cells are identified in each sex. The possible reasons for the existence of hermaphroditism in the studied population are discussed based on theoretical models.

Symbioses between cyanobacteria (or eukaryotic algae and their plastids) and protists or invertebrates are well known and are important in evolution and ecology. However, no such symbioses have been previously reported in arthropods. An ultrastructural study of a branchiopod crustacean (Daphnia obtusa) from temporary ponds consistently revealed plastids inside gut endocytes. Plastids were most frequent in animals from shaded woodland ponds. Ultrastructure indicated that plastids in D. obtusa (a) are sequestered cyanobacteria and plastids from eukaryotic algae, and (b) senesce, suggesting that these generalist grazers have not closely coevolved with a plastid source. Daphnia obtusa (and other cladocerans?) in temporary ponds may benefit from plastid presence in several ways (nutrition, oxygen, calcium availability); daphnids inhabiting permanent waters may be less selected for plastid uptake. This paper represents an extension of plastid endosymbiosis into the Arthropoda, and indicates more sophisticated evolutionary and ecological interactions between these important crustacean herbivores and their food than previously recognized.

The effect of unilateral and bilateral eyestalk ablation on molting and reproduction of the estuarine crab Chasmagnathus granulata was studied, during the prereproductive (PRE), reproductive (R), and postreproductive (POST) periods under constant laboratory conditions. The effect of the laboratory conditions themselves was also evaluated by comparing the control intact crabs maintained in the laboratory with an intact outdoor group. Bilateral ablation was a stronger inducer of molting than was unilateral ablation. The former treatment induced in both sexes the highest percentages of molting (65–100%) in shorter times, as well as a higher size increment at molting, regardless of the period when it was performed. During POST period, unilateral-ablated and intact crabs from both sexes also molted, females in a higher percentage than males. No spawning was recorded in females that had undergone bilateral ablation. Unilateral-ablated and intact females first spawned and then molted during R. Unilateral ablated females also had, during R period, up to two spawnings before molting, whereas the laboratory control crabs had only one. The laboratory-control and unilateral-ablated females spawned during PRE period, while none of the outdoor control did during that period. We conclude that: (1) bilateral ablation is a very strong inducer of molting for both sexes during any season of the year, (2) unilateral ablation increases the female reproductive output during the reproductive period, and (3) the laboratory conditions used in this study are capable of inducing spawning during the prereproductive period.

The female genital structures of nineteen species of the subfamily Paradiaptominae (Diaptomoidea, Diaptomidae) were studied using light and scanning electron microscopy (SEM). They exhibit a common organization characterized by the absence of seminal receptacles and by the presence of a ventral genital operculum covering the paired gonopores, confirming the general pattern of the Diaptomoidea. The taxonomic value of these structures is analyzed: the shape, size and position of the genital operculum on the genital somite is proposed as a new diagnostic character for the subfamily. The Paradiaptominae species are characterized by a peculiar placement of the spermatophore on the female, in dorsal or laterodorsal position on the urosome. The observations lead to a new hypothesis on the mode of fertilization of the females via a fertilization tube.

South American species of the freshwater copepod genus Boeckella are distributed in the Andean region, which corresponds to southwestern South America below 30° south latitude, also extending along the Andean highlands north of this latitude, and comprises the Subantarctic, Central Chilean, Patagonian, and Paramo-Puna subregions. Based on a track analysis, five generalized tracks were found: Subantarctic (involving some Subantarctic islands, the Falklands, Tierra del Fuego, and the southern portion of continental Chile and Argentina): B. brevicaudata, B. poppei, B. vallentini, and B. michaelseni; Patagonian (in the southern Patagonia plateau): B. brasiliensis, B. silvestrii, and B. longicauda; Mid-southern Andes: B. gibbosa and B. diamantina; Paramo-Punan (in the central and northern Andes, from northwestern Argentina to western Colombia): B. calcaris, B. palustris, and B. occidentalis; and Neotropical (mainly in the Neotropical region, but reaching also Patagonia and the Puna): B. meteoris and B. bergi. Two nodes have been determined: one in southern Chile and Argentina, where the Subantarctic, Patagonian, and Neotropical tracks intersect, and the other in the central Andes, where the Paramo-Punan and Neotropical tracks intersect.

Two new Cletocamptus species, C. axi and C. schmidti, collected from lagoons of the Islands of Santa Cruz and Floreana, Galápagos Archipelago, are described and illustrated. A careful morphological analysis established a close relationship, or even the identity, with the widely distributed species C. deitersi. The two forms differ slightly from each other in their body ornamentation and in the chaetotaxy of the exopodites of pereiopods 3 and 4. Nevertheless, they fit well in the often-documented variability of C. deitersi. Their co-occurrence at one study site, however, suggests the existence of two distinct species, without intermediates, in the Galápagos Islands. A map showing the distribution of both species known so far in the area of investigation is provided.

Newly recovered fossils from the Eocene Hoko River Formation of western Washington, USA, constitute the first recognized occurrence of the Cheiragonidae Ortmann in the fossil record. The Cheiragonidae are recognized as a distinct family and are clearly distinguished from the Atelecyclidae Ortmann based on numerous characteristics of the dorsal carapace, appendages, sternum, and chelipeds. The genus Montezumella Rathbun is removed from the Atelecyclidae and placed within the Cheiragonidae. The reassignment of Montezumella to the Cheiragonidae extends the known occurrence of the family into the late Eocene. Montezumella eichhorni n. sp., Trichopeltarion granulosa n. sp. are recognized from Tertiary rocks of Washington, and Trichopeltarion merrinae n. sp. is recognized from late Miocene rocks of New Zealand.

The Japanese freshwater crab Geothelphusa exigua Suzuki and Tsuda, 1994, is sympatric with Geothelphusa dehaani (White, 1874) in riverine habitats in Ohsumi Peninsula, Kagoshima Prefecture, southern Kyushu, Japan. We examined a number of biological characteristics of both crabs in two rivers in Ohsumi Peninsula to elucidate the factors maintaining their sympatric distribution. Results showed few biological differences between the two species, except for maximum body sizes and habitat preference. Geothelphusa exigua is smaller than G. dehaani in the maximum body size and lives mainly in water (aquatic), whereas G. dehaani may live both in water and on land (amphibious).

The complete larval development of Philyra platychira de Haan, 1841, from hatching to the megalopal stage, was obtained by laboratory rearing. Three zoeal and one megalopal stages are described and illustrated in detail. In the subfamily Philyrinae, it is unusual that the zoea has a lateral swollen protuberance on the carapace that in the third stage develops into a spine. The Philyra zoeae could be easily distinguished from the zoeae Arcania and Myra by having no lateral carapace spine, 2 1 setae on the endopod of the maxilla, and three small teeth on the posterolateral margin of the telson. In the family Leucosiidae, Philyra is as advanced as the leucosiines, whereas Arcania and Myra are the most ancestral group, based on the zoeal characteristics. Therefore, it is considered that the subfamily Philyrinae might be a significantly heterogeneous group.

The euphausiids, Euphausia pacifica Hansen, 1911, Thysanoessa inermis (Kröyer, 1846), T. longipes Brandt, 1851, T. raschi (M. Sars, 1864), and T. spinifera Holmes, 1900, were found to be infested with the ellobiopsid Thalassomyces fagei (Boschma, 1949) in Prince William Sound (PWS), south-central Alaska. Thysanoessa longipes and T. spinifera are reported for the first time as hosts for the parasite Thalassomyces fagei. Plankton samples were collected in May, August, and October 1997, and in July 1998 from northern, central, and southern study areas in PWS. Density of ellobiopsids on all species of euphausiids in each study area ranged from 0 to 2.0·m⁻², while density of adult-size euphausiids of all species ranged from 6.7 to 263.4·m⁻². The prevalence of ellobiopsids on adult-size euphausiids ranged from 0 to 31.3% by species and from 0 to 7.5% by sampling area. In general, parasite density was highest where euphausiid density was lowest. Of the 20,760 adult-size euphausiids examined, 1.49% were infected with the ellobiopsid parasite T. fagei.

Metopograpsus thukuhar is a very common grapsid in the Indo-Pacific mangroves but is found only occasionally in a non-mangrove environment. Field observations investigated its spatial and temporal strategies and clarified its predatory abilities. Gut-content analysis was used to assess its natural diet. Metopograpsus thukuhar was mainly active during low tide, although many crabs were seen at high tide moving on the mangrove roots above the water level. It lived largely among the roots of the seaward Rhizophora mucronata and concentrated its activity within a definite area of the root apparatus of a single tree, appearing to be faithful to one or two specific crevices. The diet of M. thukuhar was principally based on macroalgae; mangrove leaves were also present, but animal items were rare. However, direct field observations of the crab's predatory behavior indicate that this grapsid is an opportunistic feeder with a certain degree of behavioral plasticity.

The fouling community at Algeciras Bay exhibits the general features of other warm-temperate fouling communities in which the bryozoan Bugula neritina is a major competitor for space during summer. This bryozoan was sampled in order to study spatio-temporal changes of the peracaridan fauna of Algeciras Bay (Strait of Gibraltar). The results of this work point out the relevance of studying the life cycle patterns of both the living substratum and its associated fauna prior to analyzing the possible classification or ordination of the stations. There was a good correlation between the height of B. neritina and temperature and between the colony dry mass and the number of peracaridan individuals.

Numerical analyses allowed the identification of two groups of stations based on the distribution and abundance of the peracaridan faunas in Algeciras Bay, the internal and the external stations. The external stations had higher diversity, regarding both evenness and species richness, than in the internal stations, where some species, e.g., Jassa marmorata, Phtisica marina, Ischyrocerus inexpectatus, were strongly dominant. Seasonal variation of the substratum, Bugula neritina, and the peracaridan fauna which lives on it minimized the differences between external and internal stations. The ability to utilize B. neritina as living space can be a key to the success of some peracaridan species such as Jassa marmorata, Ischyrocerus inexpectatus, and Podocerus variegatus. Moreover, the temporal and spatial offset in the maximal density shown by some amphipod species might indicate the existence of biological relationships such as competition or predation.

Developing embryos proved to be a suitable source of cells for advanced cytological investigations on Amphipods. Conventional karyotyping, Ag- and fluorochrome-staining, C-banding, endonuclease digestion, fluorescent in situ hybridization (FISH) and nuclear DNA flow cytometric assay were tested in the Ischyroceridae Jassa marmorata. The karyotype consists of 6 chromosome pairs of which 5 are metacentric and 1 subtelocentric. The rDNA/FISH revealed that major ribosomal cistrons are located on the telomeric regions in the short arm of pair 6. A marked size variation of hybridization signals was observed. Silver and fluorochrome staining enhanced no chromosome regions. Constitutive heterochromatin was scarce and limited to tiny, pericentromeric blocks as revealed by C-banding and three different restriction enzymes. The diploid genome size (1.90 pg) and the Adenine-Thymine base-pair nuclear DNA relative amount (28.85%) of J. marmorata are by far the lowest encountered in Amphipoda and Crustacea, respectively.

Nucleotide sequences for a 315-base-pair segment of the mitochondrial COI (cytochrome c oxidase subunit I) gene were compared among 76 individuals from 29 populations of the genus Ishizakiella. Resulting molecular phylogenetic trees consistently supported both the species assignment based on morphological data and the closest relationship between I. miurensis and I. ryukyuensis. However, these trees were equivocal as to the position of I. supralittoralis among the four ingroup species, i.e., it clustered as either sister group of I. novaezealandica or of both I. miurensis and I. ryukyuensis. The close relationship between I. miurensis and I. ryukyuensis was further supported by the fact that the two species share serration on the copulatory duct. The phylogenetic relationship, fossil record, and geographical distributions suggested that the ancestor of I. supralittoralis was the first to have separated from the common ancestor of the three Japanese species and arrived in the Japanese Archipelago before the Pleistocene. Then, the ancestor of I. miurensis was separated from that of I. ryukyuensis, with the former having migrated to the Japanese Archipelago to dominate over I. supralittoralis. The Sea of Japan populations of I. miurensis formed a paraphyletic group, suggesting that ancestors of I. miurensis migrated to the Japanese Archipelago at least twice. The formation of landbridge was perhaps important in the separation and migration of the populations. The large genetic distance between two populations of isolated islands observed for I. ryukyuensis indicated that open sea also acts as a notable barrier preventing gene flow.

The sequence of 18S rDNA was used to analyze the phylogenetic relationship of three thecostracans, Verruca spengleri, Paralepas palinuri, and Dendrogaster asterinae, with respect to other thecostracan crustaceans whose 18S rDNA sequences were reported previously. The ascothoracidan Dendrogaster is grouped with the other ascothoracidan, Ulophysema. Verruca, a representative of the Verrucomorpha, is located among Ibla, Calantica, and the four balanomorphs analyzed. Our finding that Verruca clusters within the Balanomorpha does not agree with the suggestion that the Verrucomorpha and the Balanomorpha evolved independently and that the order Sessilia is a biphyletic taxon. Paralepas, which belongs to the Heterolepadomorpha (pedunculate cirripeds lacking shell plates) that were regarded as presenting plesiomorphic features of the pedunculates, is placed internally within the Lepadomorpha. This raises the possibility that the Heterolepadomorpha do not represent plesiomorphic features of cirripeds. Accordingly, Paralepas may be regarded as a true lepadomorph in which the loss of shell plates is apomorphic. Our study emphasizes the importance of molecular data in understanding thecostracan evolution.

The phylogeny of select Thoracican barnacles was estimated from 18S rDNA sequences. Six new sequences were included, Semibalanus cariosus, Tamiosoma aquila, Balanus glandula, Balanus nubilus, Megabalanus californicus, and Pollicipes polymerus. These were combined with previously published sequences from Genbank. Our maximum likelihood analysis of the data is congruent with previous morphological analyses but differs from the earlier analyses based on 18S sequences, especially in the position of Ibla. We also obtained greater resolution with a gene often considered too slowly evolving to be useful at higher taxonomic levels. Sessile barnacles appear to be monophyletic, but pedunculate barnacles may not be, with the Scapelloidea being the sister taxa to the sessile ones. The Balanidae also appears to be monophyletic, while the enigmatic Heterolepidae is strongly associated with the pedunculate barnacles Lepas and Octolasmus.

Cannibalism occurs in snow crab and has been observed both in the wild and in the laboratory, but crabs larger than 60 mm CW are not killed by large male adult snow crabs either in the wild or in laboratory experiments. We tested the hypothesis that cannibalism failed to occur as smaller snow crabs became large enough to resist the force of larger male snow crabs. Chela force and resistance of the cuticle to loading were compared. Chela, merus, and carapace cuticles differed markedly in mechanical properties. The chela was hard compared to the merus which was the most flexible cuticle. Strength of the cuticle generally increased with size of crab, but decreased markedly at molting and remained low for several months past molting. The mechanical advantage (MA) of the chela was larger in adult than in non-adult snow crabs of similar size. The force of the chela was calculated from MA and previously documented size and contractile force of the closer muscle. Closing force at the first denticle on the dactyl of large male adult snow crabs was large enough to break the cuticle of non-adult and adult snow crab of any size. Only crabs less than 60 mm CW, however, were vulnerable to forces delivered at the tip of the dactyl of large adult, but not of large non-adult, snow crabs. Factors other than strength of the cuticle may explain size-selective cannibalism.

Eighty-three specimens of the bythograeid crab Austinograea williamsi Hessler and Martin, 1989, were collected from hydrothermal vent sites of the Mariana Trough. Of these, seventy-two specimens were examined for this study, including thirty-five males, thirty-six females, and one of unknown sex. Heterochely was observed, with one dactylus blunter and larger (the crusher type) than the other and one dactylus sharper and smaller (the cutter type) than the other. Females had cutters for both chelipeds, except one large female. Sixty percent of males (fifteen specimens) had a right crusher and a left cutter, and the others had two cutters. Morphometric analyses of the chela, abdomen, and carapace indicated male chelipeds were proportionally larger than female chelipeds, while female abdomens were proportionally larger than male abdomens. This sexual dimorphism was considered to be a secondary sexual characteristic related to different reproductive patterns between sexes. Additionally, using SEM, we studied the morphology of gonopods (first and second pleopods in males), which are systematically diagnostic for crabs.