Four large (Type I) interneurons with cell bodies in the anterior cluster of the brain and decussating axonal processes in an oesophageal connective initiate antennular withdrawal behavior in Callinectes sapidus. Recurrent neurites from the oesophageal process of each interneuron project into antennal and lateral antennular neuropils. These recurrent processes have varicosities on their terminal processes that are hypothesized to possess output synapses onto antennular withdrawal motoneurons. Secondary neurites of Type I interneurons in the medial antennular neuropil receive tertiary branches from antennal and lateral antennular neuropils. These secondary neurites in the medial antennular neuropil also receive short latency, excitatory input from mechanosensory afferent fibers from the antennule base. Intracellular depolarization of Type I interneurons produces antennular withdrawal ipsilateral to the descending axonal process. Intracellular recordings from identified withdrawal motoneurons during depolarization of Type I interneurons produces excitatory postsynaptic activity in these motoneurons that is of short latency. Hyperpolarization tests of Type I interneurons during stimulus-evoked fictive antennular withdrawal show that each is sufficient but not necessary for the production of withdrawal. Type I interneurons in Callinectes are morphologically and physiologically similar to interneurons previously described in Carcinus maenas.

Enzyme extracts were used to characterize α-amylase-, trypsin-, and nonspecific-esterase-specific and total activities during the early life-history stages of the red swamp crayfish Procambarus clarkii. Significant increases in the specific activities of all three digestive enzymes were observed prior to the onset of feeding, suggesting that digestive competence is attained prior to feeding and appears to be controlled genetically. After the onset of feeding, the digestive-enzyme-specific and total activity increased steadily through the 42^nd day of development, after which point activity did not change significantly. We hypothesize that the observed increase in specific activity reflects the maturation of the hepatopancreas, as greater amounts of digestive enzymes are being produced per unit weight of tissue. As individuals exceeded approximately 100 mg in total weight, specific activity was variable and did not change substantially. Further increases in total enzyme activity (total digestive capacity) were dependent primarily on increases in the weight gain of the individual. We suggest that the first four to six weeks of development may represent a crucial stage in the development of the hepatopancreas and that perturbations that occur during this stage of development may impact future growth. The pattern of digestive enzyme expression in Procambarus clarkii indicates little or no change in nutritional requirements and is different from the patterns observed in decapod crustaceans that have planktotrophic life-history stages. The digestive enzyme activities indicate that crayfish can digest and utilize primarily carbohydrates, proteins and, to a lesser extent, lipids as macronutrients during early growth.

Antibacterial activity of Fenneropenaeus indicus hemolymph was mediated by Agglutinin (Ag), a protein of molecular weight 181 kDa with two subunits 97 kDa and 84 kDa. Agglutinin was purified by gel filtration chromatography, PAGE, and SDS-PAGE, and polyclonal antibodies (anti-Ag) were raised in rabbits. In a double immunodiffusion test, single precipitin lines were found between the center well containing immune serum and surrounding wells containing purified Ag and crude hemolymph. The IgG fraction was purified from anti-Ag immune serum and used to develop ELISA. The Ag standard curve was linear over a range of 17.8–8,900 ng. The sensitivity of the ELISA was 178 ng/ml. Agglutinin-free hemolymph yielded background optical density values, confirming the specificity of the assay. Serial dilutions of agglutinin-rich hemolymph produced sample titration curves that are parallel to the Ag standard curve. Thus, the ELISA is suitable for quantification of Ag in hemolymph.

The mating behavior and fertilization capacity of three different ontogenetic stages of male rock shrimp Rhynchocinetes typus were examined. The first ontogenetic stage is the typus morphotype, which is similar in morphology to the female. The last ontogenetic stage, the robustus morphotype, is characterized by extremely long third maxillipeds and powerful chelae. During ontogenetic development between these two morphs, males undergo several intermediate molts, which are termed “intermedius.” In mating experiments with pairs of single males and females, all ontogenetic male stages (typus, intermedius, robustus) behaved in a similar manner. First, they followed the female, then embraced it with the second pereiopods and held it beneath their bodies, encaged by the pereiopods, the 3^rd maxillipeds, and the abdomen. Various stimulating and checking behaviors preceded the placement of the first spermatophore, which usually coincided with the start of the spawning process. Most spermatophores were placed during the first 30 minutes of spawning. Following spermatophore placement, males guarded the females during almost the entire spawning process, which could last longer than 120 minutes. The number of spermatophore transfer events during the mating process varied significantly between the two extreme ontogenetic male stages, being typus greater than robustus. No significant differences were found in the percentage of eggs lost by females that were fertilized by the three ontogenetic male stages. These results suggest that all male stages have the same potential to mate successfully with females in a competition-free environment. However, we propose that male mating success may change drastically when different ontogenetic male stages compete directly for access to reproductive females.

Male size at maturity is important information for management of crab fisheries. Morphometric and/or gonadal maturity, which have been used to estimate size at maturity for many male crustaceans, were examined as potential indicators of functional maturity using small, unfished stone crab Hapalogaster dentata as a model species. Morphometric size of maturity as estimated by the change of the allometric relationship between carapace length (CL) and chela height was 5.2 mm CL. The size at gonadal maturity as estimated by histological examination of the gonad and vasa deferentia was 5.3 mm CL. The functional size at maturity as estimated by observing precopulatory guarding pairs in the field was 9.5 mm CL, much larger than the former two estimates. Size-assortative mating was observed between guarding males and guarded females. Female choice for larger males and advantage of the larger males in mating fights may be the reasons why such discrepancy between morphometric and/or gonadal maturity and functional maturity exist. We suggest that minimum legal size limit for decapod crustaceans should be determined by the functional maturity—actual size to participate in mating—and that the size of functional maturity is useful information for conservation-oriented management.

The effect of salinity on embryonic development of Chasmagnathus granulata and Cyrtograpsus angulatus (Crustacea: Decapoda: Grapsidae), the most common estuarine crabs of the southwestern Atlantic Ocean, was studied by means of an in vitro culture technique. Ovigerous females and, consequently, embryos inhabit Mar Chiquita, a coastal lagoon characterized by wide daily and seasonal changes of salinity. Larvae of both species are exported to the open sea and do not tolerate low salinities. Chasmagnathus granulata embryos synchronously completed development in vitro from 12 to 44 psu, exhausting yolk reserves, having an aspect and mobility similar to those observed in vivo. In spite of antibiotic treatment, C. angulatus egg cultures became infected by filamentous bacteria and fungi after a few days, and the embryonic development could not be completed. Nevertheless, in vitro cultures allowed study of salinity effects on early embryos of both species. One day old embryos of C. granulata and C. angulatus were able to develop at salinities between 12 and 40 psu, although the mortality varied widely among broods from different females. Outside this range, embryos of C. angulatus died; those of C. granulata could survive at 6, 44, and 50 psu although the development was arrested. Tolerance of embryos of both species to extreme salinities (3 and 44 psu) was acquired after two or three days following egg extrusion. Successful hatching rarely happened in C. granulata embryos cultured in vitro, and this was probably related to the lack of some female's contact-factor during the 48 h before hatching. The possibility of a correlation between the development of salinity resistance, the formation of egg external membranes, and the behaviour of ovigerous females is discussed.

Limnadia lenticularis, a well-known representative of the Conchostraca Spinicaudata in Europe, was generally accepted as a parthenogenetic species. During an intensive faunistic study of Austrian conchostracans, four of a total of 364 collected L. lenticularis specimens were males. This paper provides the collection localities, compares the sex ratios of the five conchostracan species found in Austria, and describes the general morphology of L. lenticularis males, focussing on SEM of the male claspers.

Rhizocephalan barnacles of the genus Lernaeodiscus Müller, 1862, are uncommon external parasites of galatheid and porcellanid crabs, and most species are poorly known. Based on a thorough review of the literature and examination of new material, we summarize taxonomic and biogeographic knowledge about this genus. We report significant geographic range extensions and new hosts and correct or complete several identifications of both hosts and parasites previously reported in the literature. We present evidence that L. crenatus Boschma, 1969, is synonymous with L. porcellanae Müller, 1862, and that Atlantic and Pacific specimens of L. porcellanae are probably different species. Lernaeodiscus tableta n. sp. is described from specimens parasitizing the porcellanid Aliaporcellana suluensis from Indonesia.

The ultrastructure of the integument in a parasitic copepod Ophioika sp., which may be a new species, is described using SEM and TEM of specimens both in situ and dissected out of their brittlestar host, Ophiocoma scolopendrina. The parasite is found embedded in host connective tissue at the base of the arm. The surface of the parasite's integument facing the host has knob-like projections, some of which have long microvilli-like endings. Whether these structures have an absorptive function and play a role in the parasite's feeding is discussed.

Specimens of a monstrilloid copepod of the genus Monstrilla collected (1908) by the U.S. Fisheries steamer Albatross in the Sulu Sea, west coast of Mindanao, Philippines, and deposited in the U.S. National Museum of Natural History were taxonomically restudied. Specimens were originally identified as females of Cymbasoma longispinosum Bourne, 1890, by C. B. Wilson. Reexamination revealed that besides a single female of C. longispinosum, three other specimens were present in the same vial. One of these was identified as a new species of Monstrilla and is described herein. The new species can be distinguished by a combination of characters but mainly by having very long antennules and a bilobed fifth leg with two long setae on each lobe. The other two individuals are females of M. elongata Suárez-Morales, 1994. This species has been previously recorded only from the Caribbean Sea. This record in the Philippines represents a significant range extension for this species. This one and the new species represent an interesting addition to the Asiatic monstrilloid fauna. Regional records of Monstrilla in the Far East are also presented herein. The Philippines and east Indonesia seem to be the most speciose areas for this genus in the entire region.

Two new species of the crangonid genus Philocheras, P. gemmaceus and P. fujinoi, are described and illustrated from East Asian waters. Both were previously treated insufficiently; one was erroneously referred to Pontophilus candidus Kemp, and the other, Pontophilus sp. of Fujino and Miyake (1970), was left unnamed, because only a single, mutilated specimen was available. The first new species, P. gemmaceus, is more closely related to P. planoculminus Bruce than to P. candidus (Kemp). Philocheras gemmaceus is readily distinguishable from them by the combination of the wider rostrum, the presence of the median gastric spine in females and the bud-like appendix interna of the endopod of the second to fifth pleopods in males. More complete material from the northern South China Sea confirms the validity of the latter new species, P. fujinoi, which is distinguished from other members of the genus by the presence of one gastric spine, three frontal spines on the postorbital carina, two spines situated behind branchiostegal spine, the minute spine just mesial to the antennal spine, and the movable thumb of the first pereiopod.

The redclaw crayfish Cherax quadricarinatus is a freshwater species native to northern Australia, but it has been widely translocated overseas for aquaculture. Its gill complement consists of 21 trichobranchiate gills and a rudimentary epipod bearing tubular gill filaments. Gill size decreases from the outer layer of the podobranchs to the inner layers of the arthrobranchs and pleurobranchs. Most gill filaments have a thick epithelium and rounded apex, while a few are thinner and have pointed or hooked tips. The gross structure of the fused epipods and podobranchs from the anterior to posterior limbs suggests a serial pattern of morphological development. The redclaw crayfish has passive gill-cleaning mechanisms using the multidenticulate setae on epipods, setobranchs, scaphognathites, and the inner surface of branchiostegites. Limb motion causes the epipodal and setobranch setae to be jostled, scraping gill surfaces, and agitating the podobranchs whose outer filaments are picked and brushed by the branchiostegal setae. Multidenticulate scaphognathite setae have a minor role in gill cleaning due to a reduced number and limited reach to the gills. The compound epipodal setae contact the adjacent limb coxae and epipodal bases. Small lamellar protrusions from the arthrodial joint of the pereiopods bear setae of various types, which may serve as a filter screen for the respiratory water entering the branchial chamber. The same filtering function is ascribed to the dense pappose setae fringing the limb bases. The redclaw crayfish displays “limb rocking” by frequently moving its limbs when at rest, thereby jostling the setiferous processes and the gills inside the branchial chamber. This behavior is perceived to result in passive gill cleaning. The adaptive value and phylogenetic implications of the gill-cleaning mechanisms are discussed.

Collection of new fossils from the west coast of North America has resulted in additions to the Carpiliidae, Goneplacidae, Panopeidae, and Pilumnidae in the fossil record. Features of the dorsal carapace of members of each of these families, as defined using modern biological classification techniques, are useful in assigning the new fossil taxa to these four families. Description of new taxa and reassignment of several previously described taxa have resulted in a reevaluation of the fossil record of those groups on the west coast of North America. New species include Orbitoplax tuckerae, Panopeus prosakrolophos, and Panopeus torus. New combinations include Branchioplax carmanahensis (Rathbun, 1926), Orbitoplax weaveri (Rathbun, 1926), Panopeus baldwini (Kooser and Orr, 1973), Panopeus olearis (Rathbun, 1926), and Panopeus soledadensis (Rathbun, 1926).

Investigations into morphological and genetic differentiation of the potamonautid fauna of southern Africa revealed the presence of two morphotypes collected from the Drakensberg, KwaZulu-Natal. Both forms have been regarded as Potamonautes depressus in museum collections. The taxonomic status of the two forms was investigated genetically and morphometrically using samples from five localities. The two morphotypes could be distinguished on the basis of colour, with the northern morphotype being bright orange in colour, slightly smaller, and with a more thickly set carapace than the brown to green-brown southern morphotype. Allozyme electrophoresis utilizing 21 presumptive loci showed the two morphotypes to separate at a genetic identity value of 0.599. Five loci proved to be diagnostic between the two forms, with strong heterogeneity present at a further three loci. Discriminant functions analysis of seven carapace variables showed the two morphotypes to be morphometrically distinct. The southern morphotype was identified as Potamonautes depressus s. str., and it was concluded that the northern morphotype represented an undescribed species, described here as Potamonautes clarus sp. nov. The new species is compared to known Potamonautes species from South Africa.

Genetic relationships among 37 local populations of Geothelphusa dehaani from southern Kyushu, Japan, were examined by electrophoretic analysis at 15 loci encoding 12 enzymes and a general protein. Local populations from the mainland of Kagoshima Prefecture, southern Kyushu, were genetically interrelated, independent of body coloration (red, blue, or two-tone types). Populations from the islands neighboring the Kagoshima mainland were differentiated into two genetic groups, which are distantly related to each other, also independent of body coloration, except for the populations from the Koshikijima Islands, west of Kagoshima mainland. One group of island populations was genetically associated with the mainland populations, both forming a clade of a mainland lineage. The other group, recognized as an island lineage, was highly differentiated from the mainland lineage. Both lineages, mainland and island lineages corresponding to blue and red color types, respectively, were sympatrically distributed on Koshikijima Islands, thus possibly suggesting a secondary contact. It is suggested that the observed genetic differentiation among local populations of G. dehaani in southern Kyushu possibly resulted from geographic isolation, consistent with the past geological process of island formations in the region.

We compared seasonal patterns of habitat use by the prawn Palaemonetes paludosus and the crayfish Procambarus alleni in Blue Cypress Marsh Conservation Area, Florida. Prawn densities were similar to those found in other oligotrophic wetlands of southern Florida, whereas crayfish densities were much greater than reported previously for other wetlands in the area. Prawns and crayfish had strikingly different patterns of habitat use. Prawn density and biomass were similar in wet prairies and sloughs, whereas crayfish density and biomass were significantly higher in wet prairies. Within habitats, the abundance of prawns and crayfish generally increased with increasing structural complexity and the abundance of crayfish generally decreased with increasing water depth. Differences in risk of predation, frequency of agonistic encounters, food availability, and other factors likely contributed to observed patterns of habitat use. Because of differences in their ability to burrow and avoid concentration into dry-season refugia, prawns and crayfish responded very differently to seasonal variation in hydrologic conditions. Prawn densities were initially low (following a severe drought) and then increased during much of the study period, whereas crayfish densities were relatively stable throughout the study period. Overall, it appears that prawns are more responsive to antecedent hydrologic conditions and crayfish are more responsive to the availability of suitable habitats such as wet prairies.

The occurrence of dark brown melanized spots indicative of the presence of crayfish plague fungus (Aphanomyces astaci Schikora) was investigated in three Finnish lakes inhabited by the introduced American signal crayfish (Pacifastacus leniusculus Dana) in 1979, 1983, 1985–1988, 1990, 1993, and 1994. The crayfish were caught with crayfish traps during August–September, 7–8 weeks after the moult. In one lake in which P. leniusculus population had developed from juveniles imported from Sweden in 1971, the crayfish showed no signs of infection. The lake also contained a population of the native noble crayfish (Astacus astacus L.). The coexistence of the two species for nearly 30 years in the same habitats in this small lake indicates the absence of crayfish plague. In two lakes P. leniusculus populations originated from adults imported from Lake Tahoe, U.S.A., in 1969. In 1979 the prevalence of infected P. leniusculus in the lakes (n = 1,841) was high, 52% in Lake Karisjärvi and 47% in Lake Iso-Majajärvi. By 1988 the prevalence had decreased to only 11% and 12%, respectively. During the 1990s, the number of infected specimens began to increase, reaching 24% in Lake Karisjärvi in 1993, and 18% in Lake Iso-Majajärvi in 1994. The black spots most commonly occurred on the walking legs (40% and 39%, respectively) and the chelae (28% in both lakes). The mean number of spots per crayfish was 2.0 and 2.4; many (43% and 36%, respectively) were > 3 mm in diameter. Crayfish plague does not appear to have affected the P. leniusculus populations in the study lakes in any way, nor have any mortalities been reported in either lake.

Shell resource utilization in two common species of hermit crabs, Calcinus latens (Randall) and Calcinus gaimardii (H. Milne Edwards), from intertidal and subtidal zones at Kenting, southern Taiwan, was studied. Field data were compared with laboratory results in shell-selection tests. Shell parameters examined included shell length, shell width, aperture length, aperture width, and weight in sea water. Crab parameters examined included carapace length, shield length, and wet weight. Most intertidal C. latens did not use the most abundant shell type in the field, but showed a strong preference for the most abundant shell type in shell-selection tests. The small size of the most abundant shell type in the field appeared to be responsible for this pattern. The results of shell-fit tests showed that most crabs lived in adequate shells at least in terms of internal volume. Shell-selection tests, however, proved that larger crabs (carapace length > 5 mm) are more shell-limited than smaller ones by SAI (shell adequacy index) values. Larger crabs would select much larger shells if they were available. Differences in shell utilization between the subtidal C. latens and C. gaimardii are discussed.

A total of 24 morphological abnormalities associated with the Runt-Deformity Syndrome (RDS) is reported for the first time in 17- to 18-mo old F₃ generation Penaeus monodon (>40 mm CL) belonging to three breeding families. Although diagnosed as positive for the infectious hypodermal and hematopoietic necrosis virus (IHHNV), the shrimp appeared normal at 9 to 10 mo when they were procured from a commercial facility in Antique, central Philippines, in September 1996. The abnormalities affected either specific shrimp organs and appendages (e.g., rostrum, antennae, uropods) or the whole body (e.g., shell color and hardness). A two-way analysis of variance was used to evaluate differences in the morphometric characters rostral length (RL), carapace length (CL), abdominal length (AL), body length (BL), total length (TL), carapace width (CW), 1^st abdominal segment width (AS₁W), and body weight (BW) and the morphometric ratios RL:CL, CL:AL, and CW:AS₁W by sex and stock (3 families and wild controls). Female P. monodon had significantly larger CL, AL, BL, TL, CW, and BW than males, regardless of stock. Wild females had longer BL and TL than cultured ones, whereas wild male shrimp had shorter CL, CW, and BW than cultured male P. monodon. Cultured shrimp had significantly higher CL:AL and CW:AS₁W ratios and lower RL:CL ratio compared to wild P. monodon. The shorter and narrower abdomen relative to the carapace gave the shrimp a “runted” or dwarf appearance characteristic of RDS earlier described in Litopenaeus vannamei with IHHNV. Confirmed by parallel studies, IHHNV infection of the cultured P. monodon may account for their cuticular deformities, slower growth, and smaller sizes. The appearance of deformities in older (and bigger) P. monodon suggests that RDS expression is dependent on age and size. Examination for external abnormalities and evaluation of the three morphometric ratios may complement existing screening protocols for diseases and growth rates in shrimp breeding programs. Cultured giant tiger prawn also had lower sperm count, greater proportion of dead and abnormal sperm, and lower incidence of mating (absence of sperm in thelyca) compared to wild P. monodon.

The difficulties which meet the systematist are but little understood or appreciated by those engaged in other fields of biological work. The morphologist, the embryologist, the physiologist give him but little encouragement and sympathy…. The path is not always easy nor the way clear (Richardson, 1904a).