Keiji Wada - Academia.edu (original) (raw)

Papers by Keiji Wada

Publications of the Seto Marine Biological Laboratory, 1987

In a mangrove forest of southern Thailand, underground vertical distributions of macrofauna and r... more In a mangrove forest of southern Thailand, underground vertical distributions of macrofauna and root biomass were investigated to a depth of 1 m. While smaller roots were distributed more or less evenly, larger roots were restricted to shallower layers. Animals were more abundant in shallower layers, but some of them penetrated into the deepest. Relation between the distribution of animals and that of larger roots is discussed.

Publications of the Seto Marine Biological Laboratory, 1981

Publications of the Seto Marine Biological Laboratory, 2001

Shells of the intertidal gastropod Turbo coronatus coreensis at Tanabe Bay, central Japan, were f... more Shells of the intertidal gastropod Turbo coronatus coreensis at Tanabe Bay, central Japan, were fouled predominantly by the green alga Cladophora conchopheria, the latter being more abundant on these snails higher up the shoreline. The abundance of C. conchopheria on the shells of large snails (shell length> 10 mm) showed no significant seasonal changes, although the alga was recorded on small snails (shell length< 10 mm) from June to October and December but not in February or April. C. conchopheria was less abundant on T. coronatus coreensis shells inhabited by hermit crabs than on the shells of living snails. Increments of C. conchopheria coverage were not correlated with shell growth of individual snails. Under laboratory conditions, the coverage of C. conchopheria on snail shells decreased, and the rate of such not differing among early dead snails, later dead snails and shells inhabited by hermit crabs. The survival rates of T. coronatus coreensis in the laboratory was similar between snails fouled heavily or not at all by C. conchopheria.

Japanese Journal of Benthology, 2014

The present status and problems of threatened benthic animals in the tidal flats of Japan are dis... more The present status and problems of threatened benthic animals in the tidal flats of Japan are discussed. These issues came to light during the editing process of Threatened Animals of Japanese Tidal Flats: Red Data Book RDB of Seashore Benthos Japanese Association of Benthology, 2012. In this book, 651 species 462 molluscs, 138 arthropods, 21 polychaetes, and 30 other invertebrates were designated as threatened benthic animals and categorized as follows; one Extinct, 38 Critically Endangered, 76 Endangered, 168 Vulnerable, 291 Near Threatened, 67 Data Deficient, and 10 Threatened Local Populations. Among various combinations of distributional ranges in Japan, the largest numbers of RDB species were recorded from the area of Amami Islands and southwards , i.e. 108 of the 651 species, 15 of the total. The major reasons for RDB listing were habitat degradation and population decline for molluscs, rarity for arthropods, and population decline and habitat degradation for polychaetes. The relatively high percentage of parasitic and symbiotic RDB species 10.4 of molluscs, 18.1 of arthropods, and 14.3 of polychaetes indicates that the conservation of their host species must also be taken into account. In conclusion, the following actions are recommended: 1 reinforcement of the publishing of Red Lists RL and Red Data Books by both national and local governments; 2 expansion of benthic research through various means, including appropriate publicity; 3 compilation of other RL/RDB species besides the invertebrate benthos of tidal flats e.g., fish or seagrasses of tidal flats, and benthos of rocky shores , and eventual reappraisal of the RDB status of the species covered in Japanese Association of Benthology 2012 ; and 4 development and appropriate maintenance of specimen collections,and encouragement of popular understanding and governmental support in allocating appropriate human resources and adequate financial resources for the institutions that manage these collections.

Journal of Molluscan Studies, 1999

Population structure and spatial distribution with growth of the direct-developing gastropod, Bat... more Population structure and spatial distribution with growth of the direct-developing gastropod, Batillaria cumingi, were investigated on two shores of differing substrata. Sand-mud shore and rocky shore populations differed in size structure; first-year snails were ca. 7 mm in shell length (SL) in both populations, whereas second-year snails, merging with older cohorts, measured 15-25 mm SL in the sand-mud shore population and ca. 15 mm SL in the rocky shore population. Egg distribution matched adult distribution in the sand-mud shore population, but was more restricted than that of adults in the rocky shore population. The distribution of newly-hatched juveniles (0-1 mm SL) was restricted in both populations, but the growth stage at which snails extended their distribution differed between the two populations; 1-2.5 mm SL on the sand-mud shore and Ͼ 5 mm SL on the rocky shore. Floating achieved by early juveniles (ca. 2 mm SL), was commonly observed in the sand-mud population, but rarely in the rocky shore population. The sudden expansion in distribution of the 1-2.5 mm SL growth stage in the sand-mud shore population is considered to have been caused by floating, while expansion of the distribution of older growth stages (Ͼ 5 mm SL) in the rocky shore population probably occurs by crawling.

BENTHOS RESEARCH, 1997

A small ocypodid crab, Ilyoplax pingi, was found to cohabit with another, larger ocypodid crab, M... more A small ocypodid crab, Ilyoplax pingi, was found to cohabit with another, larger ocypodid crab, Macrophthalmus banzai, by two means: lodging in the burrows of M. banzai or occupying their own burrows connected with those of M. banzai. In the former case, the number of 1. pingi observed emerging from a burrow of M. banzai was 4.0 on average and at most 16. In the latter case, the number of I. pingi burrows connected with one burrow of M. banzai was 2.8 on average and at most 10. The main activity of I. pingi utilizing M. banzai burrows was feeding (or feeding and waving). The activity spaces of several I. pingi either from the same M. banzai burrow or from their own burrows connected with the same M. banzai burrow overlapped considerably. Fifteen to 28% of I. pingi utilizing M. banzai burrows began to wander within 5 min of exitting the burrow. It appears that M. banzai burrows are utilized by wandering I. pingi as temporary shelters.

Journal of Experimental Marine Biology and Ecology, 1990

Publications of the Seto Marine Biological Laboratory

Spatial distributions and population structures of Scopimera globosa De Haan and Ilyoplax pusillu... more Spatial distributions and population structures of Scopimera globosa De Haan and Ilyoplax pusillus (De Haan) (Decapoda: Ocypodidae) were investigated at four stations established on the intertidal flat of Waka River Estuary, middle Japan. In S. globosa, large males tended to be restricted to the upper level, while small males and juveniles were distributed more evenly. This feature is explained in connection with repulsive interactions between individuals. Juveniles of l. pusillus showed higher densities at upper levels inhabited by many conspecific sexable crabs, and the spatial associations between these juveniles and sexable crabs within the upper levels were highly positive. These spatial features of juvenile I. pusillus are attributable to their special habit that they can dwell in the adult burrows together with the adults. At the stations inhabited by both S. globosa and l. pusillus, juvenile S. globosa appeared to be restricted within rather upper levels, although no such tendency was detected at the stations devoid of I. pusillus. Thus, it is suggested that the distribution patterns of these two species are influenced by intraspecific or interspecific relations.

Publications of the Seto Marine Biological Laboratory, Jan 31, 1983

Journal of Crustacean Biology

Journal of the Marine Biological Association of the United Kingdom, 2013

The genetic relationship between fiddler crab Uca crassipes populations from the continental coas... more The genetic relationship between fiddler crab Uca crassipes populations from the continental coast, continental islands, and oceanic islands in the west Pacific was investigated using 1039 bp (base pairs)-long combined 12Sr-RNA–16Sr-RNA sequences and a 504-bp mitochondrial DNA control region. The combined 12Sr-RNA–16Sr-RNA sequences indicated that the Vietnamese population, located along the continental coast, and the Chichi-jima population, which is located on an oceanic island north of the Northern Mariana Islands, formed different clades than populations from the other Ryukyu Islands and Moorea Island. Conversely, the Ryukyu Islands and Moorea Island populations exhibited a close genetic relationship, although the mtDNA control region indicated significant differentiation between the Ryukyu Islands and Moorea Island populations. The isolated Vietnam and Chichi-jima populations exhibited higher genetic diversity in the control region than the other populations.

Crustaceana, 2006

The small ocypodoid crab, Ilyoplax pusilla exhibits a subtle territorial behaviour termed barrica... more The small ocypodoid crab, Ilyoplax pusilla exhibits a subtle territorial behaviour termed barricade building. The barricades are made of mud. To better understand the evolution of this behaviour, the responses to artificial earthen structures built near the crabs' burrows were compared between I. pusilla and two other species, Ilyoplax deschampsi and Scopimera globosa, of the same family, that do not build barricades. Ilyoplax pusilla broke the structure less frequently than did S. globosa and more frequently avoided it than did I. deschampsi. These results suggest that I. pusilla is more disposed to avoid the earthen structure, which would favour the evolution of barricade building. RÉSUMÉ Le petit crabe Ocypodidae, Ilyoplax pusilla montre un comportement territorial subtil nommé construction de barricades. Les barricades sont faites de boue. Afin de mieux comprendre l'évolution de ce comportement, les réponses à des structures artificielles de terre construites près des terriers de crabes ont été comparées entre I. pusilla et deux autres espèces, Ilyoplax deschampsi et Scopimera globosa, de la même famille, qui ne construisent pas de barricades. Ilyoplax pusilla a détruit la structure moins fréquemment que S. globosa et l'évitait plus fréquemment que I. deschampsi. Ces résultats suggèrent que I. pusilla est plus disposé à éviter la structure de terre, ce qui favoriserait l'évolution de la construction de barricade.

Shell utilization patterns of the intertidal hermit crab Pagurus filholi were compared between tw... more Shell utilization patterns of the intertidal hermit crab Pagurus filholi were compared between two distant local populations from Oura Bay, Shimoda, central Japan, and Hakodate Bay, Hakodate, northern Japan, in conjunction with the shell resource availability and shell utilization patterns of sympatric hermit crabs. Gastropod species of shells dominantly utilized by P. filholi differed between Oura Bay and Hakodate Bay, and shell utilization patterns did not correspond to the availability of shells in both study localities. Between P. filholi and other sympatric hermit crabs, there were some clear differences in shell species utilized in both localities, and values of niche overlap indices in shell and habitat utilizations between P. filholi and other crabs were higher in Hakodate Bay than in Oura Bay. The rich supply of shell resources in Hakodate Bay compared to Oura Bay is considered to be a factor responsible for the difference in the degree of niche overlapping between the two localities.

Journal of Crustacean Biology, 2011

Male fiddler crabs either produce lateral or vertical waves. The function of lateral waves is wel... more Male fiddler crabs either produce lateral or vertical waves. The function of lateral waves is well documented, but vertical waves have been largely unexplored. Here we explore the function of vertical claw-waving by the Japanese fiddler crab Uca arcuata by examining the context in which males produced both directed waves (the waver is facing a nearby crab) and undirected waves (waving when no other crabs are present). There are two types of mating in this species: burrow mating (the male chases a female to his burrow and they mate underground); and surface mating (the male holds the female down and they mate on the surface). Attempted burrow matings were more likely to be preceded with directed waving at the female than were attempted surface matings (83% vs. 50%). All successful burrow matings were preceded by directed waving at the female, while only 50% of successful surface matings were preceded by directed waving. Undirected waving was given in the absence of a nearby crab. The frequency of undirected waving was not related to the number of males within a 60 cm radius around the male, but was negatively related to the number of females within that distance. This suggests that undirected waving acts as a long-range female attractant.

Crustacean Research, Dec 1, 2011

The rare macrophthalmine crab, Euplax leptophthalmus H. Milne Edwards, 1852, is recorded from Jap... more The rare macrophthalmine crab, Euplax leptophthalmus H. Milne Edwards, 1852, is recorded from Japan for the first time. Numerous specimens were obtained from tidal muddy mangrove creeks on Amami-Oshima Island. Variation is discussed with regard to sexual and size differences. Differences with the allied E. dagohoyi (Mendoza & Ng, 2007) from the Philippines are also discussed.

A rare thoracotreme crab, Pseudogelasimus foii Ser6ne, 1981, originally described from Nhatrang, ... more A rare thoracotreme crab, Pseudogelasimus foii Ser6ne, 1981, originally described from Nhatrang, Vietnam, is recorded from the estuary of the Thu Bon River, Hoi An, Vietnam. A description and illustrations for the new specimen are provided. A molecular phylogenetic analysis based on mtDNA sequences confirms its taxonomic placement in the family Dotillidae.

Journal of Crustacean Biology, 2008

The dotillid crab Ilyoplax pusilla performs waving displays during the reproductive season. When ... more The dotillid crab Ilyoplax pusilla performs waving displays during the reproductive season. When a female approaches a male, he often directs his waving at her. More often, however, males do not direct their waves at any particular individual. We conducted a field experiment that manipulated neighbors' sex to clarify whether either of the sexes was more often the target of waving displays. Waving frequency by males with male neighbors was significantly higher than that of males with female neighbors. Waving frequency was correlated with the number of active male neighbors but not with the number of active female neighbors. These findings suggest that waving display of I. pusilla is performed through male to male competition.