Akira Asakura

HEMIGRAPSUS TAKANOI, NEW SPECIES, A SIBLING SPECIES OF THE COMMON JAPANESE INTERTIDAL CRAB H. PENICILLATUS (DECAPODA: BRACHYURA: GRAPSOIDEA)

Abstract The two forms of Hemigrapsus penicillatus (de Haan, 1835), recently distinguished on the basis of electrophoresis and differences in the size of the setal patches on the male chelae, are here recognized as two distinct species. The individuals having smaller setal patches are H. penicillatus, whereas those with larger setal patches are described herein as a new species. Living and fresh material of the two species are also clearly separated by the size and distribution of dark spots on the cephalothorax, abdomen, third maxillipeds, and chelipeds. Morphology of the male first pleopod is different between the two species. Females of the two species are morphologically identical and cannot be easily separated once colour has faded.

Distribution, reproduction and shell utilization patterns in three species of intertidal hermit crabs on a rocky shore on the Pacific coast of Japan

Abstract The spatial distribution, reproduction, and shell utilization patterns of three species of common intertidal hermit crabs Pagurus geminus McLaughlin, Pagurus lanuginosus De Haan and Clibanarius virescens (Krauss) on a rocky shore of Kominato, Boso Peninsula, Japan, are described. Although the distribution of each species greatly overlapped, Pagurus geminus mainly inhabited the middle intertidal zone, with Clibanarius virescens occupying a lower and Pagurus lanuginosus the lowest zone. This pattern was maintained over a 1-yr period with a few minor changes. Female Pagurus geminus generally inhabited a lower zone than males, ovigerous female Clibanarius virescens were distributed slightly lower than males, whereas a distinct sexual difference in the distribution was not seen in Pagurus lanuginosus. The ovigerous period of Pagurus geminus extended from October to August and is the longest reproductive season reported for a rocky intertidal decapod in Japanese waters. Pagurus lanuginosus became ovigerous from December to May and Clibanarius virescens, from April to December. The sex ratio was biased toward females in each case. Shell utilization patterns differed significantly between the three species, with Clibanarius virescens using the greatest variety of shells (33 species). Within species, sexual differences in shell utilization were seen in Pagurus geminus and Clibanarius virescens.

Population ecology of the sand-dwelling hermit crab Diogenes nitidimanus Terao. 5. Ecological implications in the pattern of molting

ABSTRACT Patterns of molting of the hermit crab Diogenes nitidimanus were observed in the laboratory. Data were obtained for 5-day periods after the time of the collection throughout the course of 1 year. The frequency of molting exhibited a bimodal pattern with 1 peak in spring and another in fall, though there was a slight difference between sexes. In both sexes, molting occurred more often in the reproductive season than in the nonreproductive season. Females molted more often than males during the reproductive season. Growth increments became smaller as the size of the crabs increased; this reduction was more marked in females. Females often did not increase or even became smaller at molting, in particular during the reproductive season. Such cases were very rare in males. Shell-size adequacy was assessed for molted crabs by comparing the size of shells actually used by the crabs with those chosen by crabs from shell sets with a wide size range. Females occupied shells smaller than those preferred, whereas males had optimum-sized shells. Zero or negative growth in females may result from the effects of utilizing smaller shells as well as higher energy requirement for ovaries than testes. The growth mode of this species was considered to be indeterminate, with egg laying during some instars, and one or more layings per instar.

Hermit crabs perceive the extent of their virtual bodies

A flexible body image is required by animals if they are to adapt to body changes and move effectively within a structurally complex environment. Here, we show that terrestrial hermit crabs, Coenobita rugosus, which frequently change shells, can modify walking behaviour, dependent on the shape of the shell. Hermit crabs walked along a corridor that had alternating left and right corners; if it was narrow at the corner, crabs rotated their bodies to avoid the wall, indicating an awareness of environmental obstacles. This rotation increased when a plastic plate was attached to the shell. We suggest that the shell, when extended by the plate, becomes assimilated to the hermit crabs own body. While there are cases of a tool being assimilated with the body, our result is the first example of the habitat where an animal lives and/or carries being part of a virtual body.

Infraorder Anomura MacLeay, 1838

This chapter briefly discusses that the Infraorder Anomura Macleay, 1838. Anomura, of all the decapod infraorders, has had a particularly unstable taxonomic history, with groups such as the dromiacean crabs and the thalassinidean shrimps being variously included and excluded over the years. The name for the group has also been vigorously debated. The monophyly of Anomura is now well established, as is its sister group relationship to the infraorder Brachyura; together forming the Meiura of Scholtz & Richter. Anomura, as currently conceived, comprises 7 superfamilies, 20 families, over 200 genera, and 2200 species. Anomura exhibit a great diversity in body form. In the asymmetrical hermit crabs (Paguroidea: Paguridae, Diogenidae, Coenobitidae, Parapaguridae, and Pylojacquesidae), the pleon is generally soft, membranous, and dextrally twisted. In the hermit crab family, Pylochelidae, however, the pleon is well developed and symmetrical, and the segmentation is clearly defined, so that the general appearance is more crayfish-like. Keywords: dromiacean crabs; hermit crab family; Infraorder Anomura Macleay; infraorder Brachyura; pleon; thalassinidean shrimps

A NEW HERMIT CRAB OF THE GENUS CALCINUS FROM MICRONESIA, INCLUDING NEW INFORMATION ON C. REVI (DECAPODA: ANOMURA: DIOGENIDAE)

Calcinus kurozumii, new species, is described and illustrated based on specimens from the northern Mariana Islands, Micronesia. It is a member of the group in which the dactyls and propodi of the third pereiopods have dense brush-like setae on the ventral face. The new species is distinguished from other Indo-West Pacific species of the group by the armature of the left cheliped. The new species is compared with a similar species from Polynesia, C. revi Poupin and McLaughlin, 1998. Calcinus revi is rediagnosed based on new material from the Izu-Ogasawara-Mariana Arc, and growth-related morphological variations and color are reported. A key to the Indo-West Pacific species of Calcinus with the brush of setae is provided.

Hermit crabs of the genus Calcinus Dana 1851 (Crustacea Decapoda Anomura Diogenidae) with a brush of setae on the third pereopods, from Japanese and adjacent waters

Eight species of hermit crabs of the genus Calcinus Dana 1851 with a brush of setae on the third pereopods are recorded from tropical Japan and the Mariana islands, Micronesia. New information on color variations in C. morgani Rahayu & Forest 1999 and C. elegans (H. Milne Edwards 1836) is reported. Color pattern differences between Japanese and Australian representatives of C. argus Wooster 1984 has been found. Special structures on the chelipeds of each species are reported. The systematic positions of C. anani Poupin & McLaughlin 1998 and C. sirius Morgan 1991 are reconsidered and discussed. The taxonomic confusion in the literature between C. morgani and C. gaimardii (H. Milne Edwards 1848), is clarified

Diogenes holthuisi, a new species of hermit crab (Decapoda, Anomura, Diogenidae) from shallow waters of the Ogasawara (Bonin) Islands, Japan

This chapter describes and illustrates Diogenes holthuisi , a new species of hermit crab from shallow waters of the Ogasawara (Bonin) Islands, Japan. The new species is characterized by the bifid shaped antennal acicles and presence of a few very strong spines posterior to the spine row on the branchiostegite. By these characters, the new species is easily distinguished from other species among the species group of Diogenes with a simple intercalary rostral process and the antennal peduncles longer than the ocular peduncles. The systematics of the new species is also discussed in detail. Keywords: Diogenes holthuisi ; hermit crab; Japan; Ogasawara Islands; shallow waters; systematics

Pagurixus nomurai, New Species, and Additional Record of Pagurixus maorus (Nobili, 1906), Hermit Crabs from Kume-jima Island, the Ryukyus, Japan (Decapoda: Anomura: Paguridae)

Two pagurid species of the genus Pagurixus Melin, 1939, P. nomurai, new species, and P. maorus (Nobili, 1906), are described and illustrated in detail on the basis of material from Kume-jima Island, the Ryukyus, Japan. Among the 12 known species of the genus, the new species appears closest to P. maorus, and the material at hand permits an adequate evaluation of the differences between the two taxa. The present record of Pagurixus maorus greatly extends its known biogeographical range north and west. The hermit crab genus Pagurixus Melin, 1939, now contains 12 species known from the cool temperate to tropical regions of the Indo-West Pacific (McLaughlin and Haig, 1984; Gunn and Morgan, 1992; Morgan, 1993). Three of these species, i.e., P. anceps (Forest, 1954), P. boninensis (Melin, 1939),

BONINPAGURUS ACANTHOCHELES, A NEW GENUS AND SPECIES OF HERMIT CRAB (DECAPODA: ANOMURA: PAGURIDAE) FROM SHALLOW WATERS OF THE OGASAWARA (BONIN) ISLANDS, JAPAN

Abstract Boninpagurus acanthocheles, a new genus and new species of hermit crab (Decapoda: Anomura: Paguridae) from shallow waters of the Ogasawara (Bonin) Islands, Japan, is described and illustrated. The new genus is characterized by the following characters: in males, the coxa of the right fifth pereopod has a straight or slightly curved, elongate sexual tube that is about 2–3 times the coxal length, directed laterally or posterolaterally, the proximal portion of the tube being stout and opaque and the distal portion transparent; the coxa of the left fifth pereopod has a short protrusion of vas deferens; females have paired gonopores and lack first pleopods. The new genus is similar to Anapagrides in several diagnostic features, from which it is distinguished by morphology of the male sexual tubes, the fourth pereopods, and female gonopores.