The interaction of freshwater, seawater, and limestone creates the unique environment of the anchialine cave. Anchialine cave systems are characterized by the presence of several strong density interfaces that isolate the cave system into components: regions of freshwater at the surface, a hydrogen sulfide layer, and a warm oceanic intrusion that is devoid of oxygen. These unusual physical parameters provide a challenging environment for the organisms that reside there. Within the hypoxic and anoxic regions of the cave system, a unique community of macrofauna has adapted to cope with constant low oxygen conditions and a depauperate food supply. We examined respiration rates and proximate compositions of individuals representing seven orders of troglobitic crustaceans collected from two Bahamian anchialine caves. In addition, we examined the physical conditions of both caves to determine ambient oxygen concentrations. Mass-specific respiration rates of the troglobites were more than an order of magnitude lower than those of comparably sized pelagic crustaceans. When compared to organisms residing in oxygen minimum zones, respiration rates of the troglobites were similar, or in some cases, lower. Enzymes of the troglobites were anaerobically poised with lactate dehydrogenase activities exceeding those of citrate synthase in all species. Malate dehydrogenase activities were greater than lactate dehydrogenase activities, indicating further evolutionary adaptations to an anaerobic environment.

The cyst deposition behaviour of Streptocephalus torvicornis is described as the first documented case of active cyst deposition in Anostraca. The functional morphology of the brood pouch of S. torvicornis is described and illustrated using both Light Microscopy and Scanning Electron Microscopy. The brood pouch is an elongated tube-like structure with a subterminal crescent-shaped opening. During cyst deposition, the females insert this structure into the sediment to a depth of almost 10 mm, and deposit the resting cysts, analogous to an insect ovipositor. The opening mechanism of the genital pore is explained by contraction of a branched longitudinal muscle. The adaptive value of laying cysts into the soil and possible dispersal strategies are discussed.

Branchipodopsis buettikeri, a new fairy shrimp species (Anostraca, Branchipodidae) collected from shallow desert temporary ponds in the Sultanate of Oman, is described. It is the first species of the genus Branchipodopsis found in the Arabian Peninsula. The new species is mainly distinguished from other species of the genus by the shape of the second antennae of the male, and by the shape of the clypeus outgrowths. Biogeographical implications are discussed.

That some barnacles are obligate commensals of sea turtles has long been known; however, little attention has focused on understanding the details of this association. In particular, early life-history traits of turtle barnacles, which may be key to establishing the association, have not been well studied. Here we present the first complete description of larval development in a turtle barnacle. Embryos were collected from Chelonibia testudinaria, a cosmopolitan and conspicuous species, and reared through metamorphosis in the laboratory. We followed sequential molting and described each stage using light microscopy. Development proceeded over nine days at 25°C and the characteristic cirriped pattern of six naupliar stages followed by a cyprid larva was observed. Implications for the association of barnacles with sea turtles are discussed relative to spatio-temporal aspects of cyprid attachment and the life history of sea turtles. Barnacle reproduction typically involves cross-fertilization between hermaphrodites but small complemental males occur in some species. In C. testudinaria, small individuals attached to hermaphrodites were confirmed to be exclusively male. They were located in the external depressions between the shell plates of hermaphrodites, within pits perhaps specialized for their settlement. This attachment location, external to and below the orifice of the hermaphrodite shell, is unique for complemental males. It is not known whether the males of C. testudinaria remain small permanently or eventually grow to become hermaphroditic, as do protandric complemental males in C. patula. Their small size may provide advantages in reducing drag and their attachment location may afford protection from removal.

The female of Haplostoma brevicauda (Canu, 1886) is redescribed primarily based on specimens living in the Ascidian Aplidium argus which is the type host. Three other Aplidium species have been confirmed to be parasitized by H. brevicauda. The redescription indicates that H. mizoulei Monniot, 1962, is synonymous with H. brevicauda. Subgroup 1 of Haplostoma, which consists of H. brevicauda and 10 congeners, exhibits at least four patterns (I–IV) of armature formulas for legs 1–4; H. brevicauda has pattern II. In this paper, the male of H. brevicauda is described for the first time based on specimens living in A. turbinatum and one other Aplidium species. A male that Canu (1892) reported as the male of H. brevicauda will be assigned here as the male of Botryllophilus ruber Hesse, 1864. The present material was obtained by the author at Roscoff, France, in 1992.

Few animals of marine origin are found living successfully in the high littoral fringe of tidal shores, which thus can be regarded as an extreme environment for such animals. In Iceland, a notable exception is the semiterrestrial Orchestia gammarellus (Pallas, 1766) (Amphipoda: Talitridae). The discovery of the harpacticoid Itunella muelleri (Gagern, 1922) in cultures of O. gammarellus prompted us to investigate the harpacticoid further. Qualitative samples were obtained from a number of locations around Iceland, as well as from Norway and Scotland. The samples were collected from habitats where O. gammarellus was present or at similar tidal levels where this species was absent. Two of the sampling sites in Iceland were under the influence of warm freshwater springs. Itunella muelleri was generally common in the upper part of the littoral fringe of rocky shores in Iceland and was found in similar habitats in Norway and Scotland. To estimate the vertical distribution of I. muelleri, a transect was taken along the shore in Hvassahraun, southwestern Iceland. On the transect, I. muelleri was restricted to the uppermost stations, being the only identifiable harpacticoid found at the highest station, well above the level of highest predicted tides. Animals living successfully in the high littoral fringe must be able to tolerate a degree of desiccation and a wide range of salinities and temperatures. Laboratory experiments showed that I. muelleri thrived in high humidity out of water and also in 8 ppt and 32 ppt seawater, at both 7° and 20°C. The animals survived for months in fresh water, but they only fed sparsely and did not reproduce. The tolerance of I. muelleri to extreme environmental conditions could make this species useful for experimental purposes or as food for fish larvae in aquaculture.

All known specimens of the presumed extinct freshwater shrimp species Syncaris pasadenae, formerly known from the Los Angeles River and other lowland stream sites in southern California, were examined. Existing specimens are housed in the Natural History Museum of Los Angeles County, California Academy of Sciences, or U.S. National Museum of Natural History, Smithsonian Institution, Washington, D.C. Syncaris pasadenae is diagnosed and redescribed and compared to its only congener, Syncaris pacifica, an extant species restricted to a few small coastal streams in northern California (Marin, Napa, and Sonoma counties). Syncaris pacifica is also redescribed. Salient and consistent differences between the species are the dorsal dentition of the rostrum and the number of pereopods bearing exopods, a character often associated with higher-level taxonomic differences in the past. The distribution of the species and the position of the genus within the family Atyidae are discussed.

The presence of Eualus pusiolus (Krøyer, 1841) in the northeastern Pacific is confirmed, and a new species that has often been confused with E. pusiolus is described and illustrated. Eualus butleri, n. sp., is found inside hexactinellid sponges and is distinguished by an elongated basal article of the antennular peduncle that exceeds the stylocerite, slender pereopods, and pronounced sexual dimorphism, with males larger than females and bearing enlarged third maxillipeds. A key to all known northeastern Pacific species of Eualus is included.

The modifications of the first two pleopods in male shrimp have long been considered to serve in insemination of the female. The role of pleopods 1 and 2 in mating in a protandric simultaneous hermaphroditic shrimp, Lysmata wurdemanni, were investigated. Results indicate that the modified endopod of pleopod 1 is not needed to transfer sperm in both male-phase (MP) and euhermaphrodite-phase (EP) shrimp. Absence of pleopod 2 does not affect the sperm-transfer success in both MP and EP shrimp. Removal of pleopod 1 also has no impact on fertilization in the MP shrimp; however, sperm transfer is affected by removal of pleopod 1 in some EP shrimp. Even when both pleopods 1 and 2 are completely ablated, about 20% of the shrimp can still fertilize successfully and another 20% partially successfully.

Fertilization is external in some crustaceans and internal in others. In the nineteenth century, it was reported that the American lobster (Homarus americanus) fertilized its eggs externally using spermatozoa stored in the seminal receptacle. Later investigators questioned this assumption, noting that the spermatophoric mass is sealed inside the seminal receptacle by an impervious sperm plug that prevents the spermatozoa from exiting the seminal receptacle via the orifice. This led to suggestions that fertilization in homarid lobsters is internal via transitory connectives that form between the seminal receptacle and the ovary/oviduct at the time of oviposition. Supporting evidence was obtained from studies in which fertilization occurred even when the orifice of the seminal receptacle was sealed with epoxy. We here report selective occlusion studies that resolve this conundrum. At spawning, spermatozoa leave the seminal receptacle not through the sealed orifice, but via two grooves located posterior and lateral to the orifice. Occluding these posterolateral grooves as well as the orifice of the seminal receptacle prevents fertilization, whereas occluding only the orifice does not. This explains why earlier attempts to prevent fertilization by occluding the orifice of the seminal receptacle were unsuccessful, and confirms that fertilization in the American lobster is external.

From 1997 to 2001, the effects of female size (cephalothorax length [CL]) and reproductive status on egg size (diameter, dry weight) and larva CL at hatching were investigated in two Homarus americanus populations in the Gulf of St. Lawrence (Îles-de-la-Madeleine, Anticosti) and one at Grand Manan (Bay of Fundy), Canada. The estimated size at 50% maturity was used to identify small (likely primiparous) females for each population. Multifactor, mixed-hierarchical ANOVA models were used to investigate the variability of eggs and stage I CL among years and populations. In all comparisons, the main source of variability in the egg and stage I larva size was females (within and among). Nevertheless, for the Îles-de-la-Madeleine population in each year except 2001, the mean stage I larva sizes from small (CL < 79 mm), probably primiparous females were significantly smaller (P < 0.0085) than the mean larva sizes from larger females. However, female CL per se explained very little of the variance in mean larval size at hatching (r² = 0.23, P < 0.05 and r² = 0.12, P = 0.22 in 2000 and 2001, respectively, when the entire size range of reproductive females was considered). Hatching larvae tend to be smaller in primiparous females or females maturing at a small size; however, over the entire size range of reproductive females, larval size at hatching is almost independent of female size (CL). It is as if, above a minimum viable size, there is a constant small range of egg/larval sizes produced in H. americanus. Conservation measures dealing with the imposition of a minimum legal size may be a means of increasing the number of females that will spawn at least once or twice within a population. However, the impacts of first-time spawning on quality of eggs and larvae need to be fully investigated to assess the response of the population's egg production and recruitment potential of this measure.

The reproduction of the alien crayfish species Pacifastacus leniusculus inhabiting Lake Shikaribetsu, Hokkaido, Japan, was studied from August 2002 to August 2003. Spawning was for a short period after mating in mid October. The eggs developed to eyed stage in June the following year and hatched in mid July. After remaining with their mother for several weeks, the juveniles became independent between late July and August. The egg numbers attached to pleopods of this crayfish significantly increased with the female body size. The time of spawning in Lake Shikaribetsu was similar to that of this crayfish living in North America and Europe reported by previous studies, but the time of egg hatching was later in Lake Shikaribetsu compared with some populations in North America and Europe. A comparison of our results of the reproduction of P. leniusculus with that of the endangered Japanese endemic crayfish species Cambaroides japonicus reported by previous studies showed that P. leniusculus has a markedly higher reproductive ability than C. japonicus in terms of egg numbers.

The premoult stages of Carcinus maenas (L.) megalopae were described from laboratory-reared larvae. Characterization of the premoult stage sequence was based upon a time sequence of morphological modifications of the distal segment of the second maxilliped, the uropod, and the telson. An intermoult plus seven premoult stages were identified, following a sequence of morphological modifications similar to the one described in previous studies of brachyuran decapods. The later premoult stages D₃ and D₄ mentioned by Drach were not observed, possibly owing to both the low calcification of the megalopae cuticle and the short duration of these moult stages. The knowledge of the time series of moult events will assist in the evaluation of the development state and competence of megalopae throughout the several phases of dispersal and recruitment, based on the observation of their morphological characters.

The influence of methyl farnesoate (MF) in the regulation of molt and gonad development in the crab Oziotelphusa senex senex was investigated. Injection of methyl farnesoate into female and male crabs significantly (P < 0.0001) increased mean oocyte diameter (236.37%) and testicular follicle diameter (25.72%) as well as mean gonad indices (females 1304.35%; males 38.00%) and also accelerated the molting (females 80%; males 100%). These results provide strong evidence that methyl farnesoate is involved in the control of both molting and reproduction in crabs.