The ecology of an atyid shrimp Caridina japonica was studied in the Shiwagi Rivulet. Yuki Town, Tokushima Pref. This species is amphidromous in nature. The juveniles migrate upstream from the sea exclusively during the night and can be seen climbing a vertical wall, where the rivulet water is trickling down. From field observation, rheotaxis seems, to be the most important orientation mechanism for the upstream migration of juveniles. The peak month of egg incubation was June. The mean duration of incubation was 40 days at 20℃ in aquaria. From these values and with known information on the duration of larval life, it was estimated that the period of upstream migration starts in August. Most males die within two years after metamorphosis, however, many females survive for more than two years.
Oxygen consumption rates in first-stage zoea larvae of an estuarine population of Macrobrachium nipponense, characterized by laying small eggs, was maximal at the lowest and highest salinities examined (3.6 and 32.0‰ S), and minimal in the intermediate range. Reduced oxygen consumption rate at intermediate salinities was also observed in larvae of a riverine population of this species, characterized by laying large eggs. However, larvae of the riverine population did not show any significant increment of the consumption rate at higher salinities, implying that they have lost the tolerance to high environmental salinity. The pattern of oxygen consumption at various salinities in the riverine population of M nipponense was recognized to be in the intermediate state between the estuarine population of this species and a riverine population of Palaemon paucidens De HAAN.
Chromosome numbers of six species of the Palaemonidae were determinated using mocified air-dry methods applied to the tesis, the regenerating biastema of the 2nd pereopod, and the ovary after the eyestalk ablation. As shown in Table 2 of the results, chromosome numbers of four species of Macrobrachium range 2n=102 and 118, and that of two species of Palaemon 2n=108 and 136. Most of the chromosomes in the examined species were metacentric and submetacentric types. And the fundamental numbers of chromosomes had wide range between these species. Considering from these results, the specific differentiation of Palaemonidae would be characterized by some possible consequence of both Robertsonian fragmentation-fusion and chromosomal rearrangements.
Dark/light adaptational changes in the eye of the Jamaican freshwater shrimp Macrobrachium heterochirus involves distal and proximal pigment migrations as well as changes in cellular shapes. A small lens-like structure at the distal tip of the rhabdom is described for the first time in a shrimp. Rhabdoms are enlarged at night. Individuals are usually nocturnal and it is believed that under dim light conditions, larger crabs have a double-advantage over small ones: not only are they stronger: they also see better in the dark. It is finally suggested that tapetal cells may respond directly to light without hormones getting involved.
Spawned eggs of Trachypenaeus curvirostris were incubated under-laboratory condition in order to examine their early life history and to compare their embryonic development with those of other penaeid species. As development progressed, samples of embryo were collected, photomicrographed and preserved in 4% formaldehyde/seawater solution buffered with sodium tetraborate. The breeders started to spawn between 21:00-00:00h. Fecundities ranged between 6,400 to 106,700 eggs. The derived correlation equation between fecundity and carapace length of breeders was Y=log(-352.215+18.6561X) (r=0.94^*). Egg size enlarged from 223μm at spawning to 400μm just before hatching. After 15h 13min at 26±0.2℃ and 32.5 ppt, 56.49% of the eggs hatched as first nauplius larvae covered with amnion-like sac. However 19.9% of the nauplius stage remained embryonized and 10.3% hatched when they reached first protozoea stage after 60h 13min. This is the first time that embryonized nauplius and protozoea stages have been reported in the ontogeny of species in the Family Penaeidae.
The lobsterette Nephropsis stewarti beronging to the family Nephropidae, were reared in the aquarium to observe habitat behavior of redused eye crustacea. Observations carried out during 1982 to 1984. All the specimens collected at 350-400m depth of Suruga Bay, off Heda Mura. Shizuoka prefecture, Japan were carried to Shimoda Marine Station Nihon University, Shimoda-Shi. Shizuoka and reared in the 1000 liter round shaped tank with running sea water. Water temperature kept at 10-12℃. The bottom of reared tank covered with fine sand. Alive starfish caught simultaneously, frozen fish and krill, alive seaurchin, artificial diet for carp were fed. Four lobsterette specimens were reared and most longest surviving period was 112 days. Remarkable habitat were, they did not show any respons to the light and walked around on the bottom through day and night but never burrowed like other animal of the Family Nephropidae. Of the diets examined, only the starfish was fed by animals. Although the feeding behavior was not observed directly.
Burrows of the Japanese crayfish Cambaroides japonicus (DE HAAN, 1841) in a stream in Sapporo, Hokkaido are described. The density of number of openings averaged 4.5/m^2 in ten reserch stations around the banks. The diameters of dominant particles were 0.125-0.400 mm at the central part of stations. Six resin casts of burrows showed that this species excavated a semistraight tunnel with two openings near the water surface of the stream. This tunnel was almost horizontal and was semicylindrical in cross-section with the floor flat. Some were also observed Y or T shaped burrows.
Crayfish in Lake Mashu, Hokkaido, Japan, were captured with tangle nets in the summer of 1992. All specimens, 171 males and 517 females, had intermediate diagnostic character between two subspecies, Pacifastacus leniusculus leniusculus and P, l. trowbridgii. Although three very large individuals of unidentified crayfish were captured in this lake by poachers of trout in 1975 and 1985, there is no certain confirmation because of illegal samplings. One of the present authors took a chance to measure one of them, a fresh male crayfish with very large chelae, in 1975 when he was 11 years old and recorded only its giant size, i.e. 47 cm carapace length. However, the largest P. leniusculus collected in this study was 5.7cm in c. l. Neoteny may have occurred because there is no secondary sexual character on chelae of adult P. leniusculus males. This lake has no river. Age of the lake is estimated as about 2000 years old. Further, all species of fish and crustaceans in the lake were artificially introduced from other waters. Of crayfish, only P. leniusculus occurs and was introduced from Portland, Oregon, U.S.A., in 1930. From these, the unidentified gigantic crayfish seems to have been P. leniusculus grown to a giant size.
The external changes with molting of a crayfish, Cambaroides japonicus (DE HAAN, 1841), were studied in aquaria. Softening and transparency of the exoskeleton, appearance of the gelatinous substance, and darkening of the body color were observed in molting. These changes appeared from five days before molting to twelve days after it. Four molting phases based on these changes and the period of them seemed to be useful to estimate the molting times in the natural habitat.
The distributions of the phyllosoma and nisto larvae of Scyllarus kitanoviriosus HARADA were investigated in the Seto Inland Sea, Japan, in use of a small beam trawl net that was towed at 17 stations in daytime, during the period from December 1986 to November 1987. The stations were placed along isobaths of every 5 m of depth in an area shallower than 30 m in depth. Eightythree phyllosoma larvae (stages III-VIII) were caught in the season from August to November, and 32 nisto larvae only in September and October. The distribution of the stage VIII phyllosoma was identical to that of the stages III to VII. The nisto larvae appeared significantly in shallower area than the phyllosoma. Neither juvenile nor adult was caught with the trawl employed. The gillnet operated near rocky shore however, caught adults, of which the females were all ovigerous in September. This fact suggests that the last stage phyllosoma metamorphoses into the nisto in 15-25 m deep in September to October, and then metamorphoses into early juvenile stage after the settlement onto the rocky bed.
The secondary sexual characteristics of Metacrangon angusticauda were investigated. The secondary maturation sign appeared in abdomen size in females. The number of eggs per female increases with increase of abdomen width. The number of segments of the outer and inner flagella were larger in males than in females.
Polyester resin casts of burrows of the thalassinidean ghost shrimp, Callianassa japonica ORTMANN, were collected on an intertidal sand flat in west Kyushu, Japan. One burrow cast obtained in September 1989 and another, obtained in September 1990, had a thin "branch" originating from the stout adult burrow cast. Evidence pointed to such branches being inhabited by newly recruited individuals of C. japonica. It is believed that settling larvae and/or newly settled juveniles had entered the surface openings of the adult burrows to later branch off independently.
Dardanus imbricatus (H. MILNE EDWARDS, 1848) is newly added to Japanese anomuran fauna, based on the single specimen collected in Okinawa Island. This hermit crab was previously recorded from Australia, New Zealand, Ceylon, the Gulf of Thailand and Vietnum. The locality recorded by the present paper is located in the northern limit of the distributional range of this species.
Field study of reproductive activity in the ocypodid crab Ilyoplax pusilla was carried out at Tanabe Bay (33°41′N, 135°24′ E). Ovigerous females were found from April through August and most abundant in June-July. Males' sexual behaviors were observed from May through July or August and most frequent in June-July. Females were suggested to spawn or release their larvae around spring tide. Daily frequency of males' sexual behaviors did not fluctuate according to tidal condition of spring to neap tides. Proportions of waving males and wandering crabs declined in the late breeding to the nonbreeding season, indicating relation of waving and wandering to reproductive activity.
Geographic distributions of two ocypodid crabs of the genus Ilyoplax : I. pusilla and I. deschampsi are summarized from the occurrence records in literatures and unpublished data. I. pusilla is distributed along the coast of mainland Japan and Okinawa, while I. deschampsi ranged along the continental coast of Bo Hai (Gulf of Chihle), Yellow Sea and northern East China Sea. The distributions of the two spesies overlap only at the southern coast of Korea and a part of northern Kyushu of Japan, and both species do not extend into the Japan Sea coast. Along the coast of Ariake Bay in Kyushu, Japan, where both species occurred, their distributions were investigated in detail. I. deschampsi was distributed on the innermost coast, while I. pusilla was on the coast of outer part of the bay, showing clear segregated distributions between them. In habitat conditions, there were some differences between the two species : soil hardness and coarseness of substratum, and salt content of underground water were, on the average, higher in the habitat of I. pusilla than in that of I, deschampsi.
Twenty-one sexually paired hair crabs, Erimacrus isenbeckii (Brandt) were collected from the northwestern North Pacific, off Kushiro during August 1986 〜 July 1991. The paired hair crabs acted the precopulatory guarding behavior. Size distributions were unimodal for each ,sex but with few overlap in their carapace length (CL). The mean CL of male and female were 89.4 mm and 56.2 mm respectively. Other than the fact that males were invariably larger than females, there was no correlation between size of the male and size of the female with which it was paired. Sizes distribution of females paired with small (CL< 90 mm) and large (CL≧90 mm) size males were the same. Based on these data, we discussed size assortative mating and sexual dimorphism on the hair crab. In this species, male size is not correlated with female size in sexual pairs. However, cleary sexual dimorphism is observed.
The settlement mechanism of Plagusia dentipes megalopae to the intertidal zone of rocky shore was investigatec. The megalopae and crabs were collected by hand every three days from April to June 1 2, 1990. To detect the main mechanism by which the megalopae were driven to the intertidal habitat from offshore, the following weather and tidal conditions were recorded: the lunar cycle, surface water temperature, wind direction and velocity. There was no apparent relationship between the number of megalopae that settled and the lunar cycle or the water temperature. Whereas, there existed strong relationship between settlement of megalopae and the prevailing north wind.
The morphological characteristics of the exoskeleton in the abult and juvenile stages of the female Japanese mitten crab, Eriocheir japonicus were recorded with reference to the shape of the abdomen, the exposure of the edges of the thoracic sternums, and the growth of hairs in the margin of the abdomen, 1st〜4th thoracic sternums, and abdominal appendages. External changes which take place during molting were also examined. During the juvenile stage (carapace measuring less than 70 mm in width), the abdomen was found to grow relatively larger, both in length and in width gradually, during pre-puberty molting. However, when the crabs were reaching the abult stage (carapace greater than 35 mm in width), the abdomen was found to drastically grow larger during puberty molting, until it nearly covered the thoracic sternums.
American edible crab, Callinectes sapidus RATHBUN has recently been obtained from Sagami Bay. Up to now there are two reports on the occurrence of this crab in Japanese waters. The first record was accounted by SATAKI in 1976, on the basis of the specimens obtained by a fisherman in 1975 at the Hamana Lake, Shizuoka prefecture. The second one was given by ARIYAMA in 1985. He described briefly on a female crab obtained from Osaka Bay in September of 1984. This short report deals with a brief account on the third record of this crab from Japanese waters.
The xanthid crabs, Leptodius exaratus and Cycloxanthops truncatus, Atergatis floridus, Etisus laevimanus, Pilumnus vespertilio prey on the hermit crabs. The five species of the crab employed the chelae and the ambulatory legs to capture the hermit crabs. The xanthid crabs break shell species occupied by hermit crab, Pagurus geminus.
The present paper provides an annotated list of decapod fauna of Hokkaido, northern Japan, mainly based on previous biogeographical works. It includes 196 species ranging 40 families, and several new records to Hokkaido are recognized.
Hypertypic regeneration was induced by wounding of the rostrum in the crayfish, Procambarus clarkii. A slightly projecting structure was formed at the site of the wound on the rostrum rim at the third molt after the rostrum rim at the third molt had been wounded. The structure elongated at each molt for three or four consecutive molts.
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