Complete larval development of the mountain river prawn, Macrobrachium latimanus (Von Martens, 1868), is described and illustrated from laboratory-reared material. The larval development comprises eleven zoeal and one decapodid stages. The larval stages each are easily distinguished by the morphology of the pereiopods and/or the pleopods, and by the uropod setation. Among Japanese Macrobrachium species, the first zoeal morphology of M. latimanus is most similar to that of M. equidens (Dana, 1852), but differs in the chromatophore patterns of the third and fourth abdominal segments. The morphology and developmental pattern of the subsequent larval stages (the second to final zoeal stages) of M. latimanus and other 16 amphidromous congeners, whose larval development was previously described, are reviewed. The zoeal morphologies of Macrobrachium species can be separated into two groups by the presence/absence of pair of posterolateral spines on the fifth abdominal segments in the second to final zoeal stages. Macrobrachium latimanus belongs to the group that has no spines on the fifth abdominal segment.

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We used a scanning electron microscope to study the minor claw and the first and second maxillipeds of Uca vocans and Uca tetragonon. Uca vocans had a slender, narrow minor claw with a wider gape, while U. tetragonon had a stout, broad claw with a narrower gape. In both species, sexual differences were slight in the lengths of the dactyl and propodus, and breadth of the minor claw. However, males of both species had deeper chelae than the females. Uca vocans had larger maxillipeds, appendages adapted to process large amounts of substratum, than U. tetragonon. Both species had spoonshaped setae on the inner side of the merus of the second maxillipeds, although U. vocans had more numerous setae, with larger spoon-shaped heads, than U. tetragonon. In both species, females scooped substratum more frequently using both chelipeds than the males, and produced a larger number of sand pellets. However, no sexual dimorphism was detected in the sizes and structures of the first and second maxillipeds.

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Social behaviors were observed in the field for six grapsoid crabs living under different habitat conditions from exposed to sheltered conditions, i.e. Helice tridens, H. japonica, H. leachi, Chasmagnathus convexus of the family Varunidae, and Chiromantes dehaani, and Perisesarma bidens of the family Sesarmidae. Fighting behaviors in these six species, cheliped-displays in H. tridens, H. japonica and P. bidens, and copulatory behaviors in H. tridens, C. dehaani and P. bidens were described. Elements of fighting behavior varied among species irrespective of taxonomic group. The three species that showed cheliped-displays occurred in more exposed habitats compared to the other species, suggesting the importance of habitat conditions in the evolution of such displays. Copulatory behaviors were observed in three species, but precopulatory courtship was absent.

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A new species of the genus Ilyograpsus is described from the Ryukyu Islands. Ilyograpsus paantu, new species, can be easily distinguished from all congeners by its longitudinal postfrontal cristae and relatively longer carapace. Ilyograpsus nodulosus was originally described from damaged juveniles, there had been no information on adult males. Present study provides diagnosis of the species based on topotypic specimens, including adult males, and compares the species with all congeners.

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The decorating behavior of 17 newly molted individuals of the majid crab Hyastenus diacanthus (De Haan, 1837) was recorded on VTR. The crabs attached various living materials to hooked setae on the carapace and walking legs after careful selection by the chelae and processing with the mouthparts. The crabs used chelipeds in a fixed way in the attachment process. Except for the horn and spots on the carapace, the crabs attached materials using the chelipeds of the opposite side. Newly molted crabs had almost finished attachment within 2 hours, but the crabs continued to work sporadically for another 1 or 2 hours. The average frequency of attachments was 91 (N=7). The hooked setae cover only a portion of the body, and other areas, except for the tips of the chelae, are covered with barbed setae. The barbed setae hold the materials, which grow outside of the hooked setae sites. The crabs were indifferent to the settlement of larvae of sessile animals, such as barnacles, and did not remove them. Consequently, portions of the crabs were covered with sessile animals. The slender setae on the dactyl of walking legs and the short setae in the pits of chelae are likely sensory organs to detect suitable materials for attachment.

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At least 25 species of oplophorid shrimp have been collected in the Gulf of Mexico and Caribbean Sea. Of these, 21 are pelagic and four commonly are found in samples taken at or near the sea floor. Acanthephyra pelagica and Heterogenys microphthalma are reported for the first time from the Gulf of Mexico. Acanthephyra acutifrons, A. stylorostratis, Meningodora marptocheles, Ephyrina benedicti and Notostomus elegans are reported for the first time from the Caribbean Sea. We provide comments on the morphology of A. curtirostris, A. eximia, A. pelagica, Hymenodora spp. and Meningodora mollis.

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Two new species of leucosiid crabs of the genera Alox and Ebalia are described. Alox uru, new species, is distinguished from all eight congeners by the shape of the carapace. Alox rugosum is perhaps most similar to the new species, but Alox uru differs in its carapace shape and the distally swollen male first gonopod. Alox zalion too has distally swollen male first gonopod, but A. uru differs from A. zalion in having the male first gonopod distally spinose. Ebalia stellaris, new species, is distinguished from E. humilis by the characters of the carapace and the cheliped. Ebalia stellaris can be also differentiated from Nursia species by a combination of carapacial characters-lack of dorsal ridge, a salient junction of anterolateral and posterolateral margins, and a distinctly wider carapace.

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