Masako Kawane

Adaptive evolution of sexual systems in pedunculate barnacles

How and why diverse sexual systems evolve are fascinating evolutionary questions, but few empirical studies have dealt with these questions in animals. Pedunculate (gooseneck) barnacles show such diversity, including simultaneous hermaphroditism, coexistence of dwarf males and hermaphrodites (androdioecy), and coexistence of dwarf males and females (dioecy). Here, we report the first phylogenetically controlled test of the hypothesis that the ultimate cause of the diverse sexual systems and presence of dwarf males in this group is limited mating opportunities for non-dwarf individuals, owing to mating in small groups. Within the pedunculate barnacle phylogeny, dwarf males and females have evolved repeatedly. Females are more likely to evolve in androdioecious than hermaphroditic populations, suggesting that evolution of dwarf males has preceded that of females in pedunculates. Both dwarf males and females are associated with a higher proportion of solitary individuals in the population, corroborating the hypothesis that limited mating opportunities have favoured evolution of these diverse sexual systems, which have puzzled biologists since Darwin.

Genetic population structure of local populations of the endangered saltmarsh sesarmid crab Clistocoeloma sinense in Japan.

During recent decades, over 40% of Japanese estuarine tidal flats have been lost due to coastal developments. Local populations of the saltmarsh sesarmid crab Clistocoeloma sinense, designated as an endangered species due to the limited suitable saltmarsh habitat available, have decreased accordingly, being now represented as small remnant populations. Several such populations in Tokyo Bay, have been recognised as representing distributional limits of the species. To clarify the genetic diversity and connectivity among local coastal populations of Japanese Clistocoeloma sinense, including those in Tokyo Bay, mitochondrial DNA analyses were conducted in the hope of providing fundamental information for future conservation studies and an understanding of metapopulation dynamics through larval dispersal among local populations. All of the populations sampled indicated low levels of genetic diversity, which may have resulted from recent population bottlenecks or founder events. However, the results also revealed clear genetic differentiation between two enclosed-water populations in Tokyo Bay and Ise-Mikawa Bay, suggesting the existence of a barrier to larval transport between these two water bodies. Since the maintenance of genetic connectivity is a requirement of local population stability, the preservation of extant habitats and restoration of saltmarshes along the coast of Japan may be the most effective measures for conservation of this endangered species.

GENETIC POPULATION STRUCTURE AND LIFE HISTORY CHARACTERISTICS OF THE RARE BRACKISH-WATER CRAB DEIRATONOTUS KAORIAE MIURA, KAWANE AND WADA, 2007 (BRACHYURA: CAMPTANDRIIDAE) IN WESTERN JAPAN

ABSTRACT Ecological and phylogeographical investigations were made of disjunct populations of Deiratonotus kaoriae Miura, Kawane and Wada, 2007 in the Kumanoe (Miyazaki Prefecture) and Miyagawa (Mie Prefecture) Rivers, so as to compare life history patterns and elucidate genetic relationships between them. The relationship of carapace width with sex and occurrence of ovigerous females revealed a similar life history pattern throughout, new recruits occurring in spring and summer, reaching maturity the following autumn, and breeding in winter and spring. Large-sized individuals disappeared before the next breeding season, indicating longevity to be around 1.5 years. However, genetic analysis suggested an absence of present-day larval migration between the two populations. Two genetic groups present in the Miyagawa population were estimated to have diverged from the Kumanoe population in the Pleistocene.

A New Species of Deiratonotus (Crustacea: Brachyura: Camptandriidae) Found in the Kumanoe River Estuary, Kyushu, Japan

Abstract Camptandriid crabs collected in the Kumanoe River Estuary, Kyushu, Japan were studied on the basis of morphological characters and molecular analysis. As a result, a new species, Deiratonotus kaoriae, was recognized. These crabs were found mainly in a creek of the sandy tidal flat within the Kumanoe River Estuary. The new species shares a very diagnostic character, the presence of a transverse ridge on the carapace, with D. cristatus (de Man, 1895) and differs markedly from the other congeners that lack this feature. The new species, however, differs from D. cristatus in the absence of harpoon-shaped setae on the subdistal end of the first gonopod and the presence of an extremely reduced second abdominal segment. According to a molecular analysis based on 12S+16S mitochondrial rRNA gene sequences, with Cleistostoma dilatatum (de Haan, 1833) and Camptandrium sexdentatum Stimpson, 1858 as outgroups, Deiratonotus kaoriae is more closely related to D. cristatus than to D. japonicus (Sakai, 1934).

Taxonomic re‐examination of the two camptandriid crab species Deiratonotus japonicus (Sakai, 1934) and D. tondensis Sakai, 1983, and genetic differentiation among their local populations

Morphological and genetic characteristics were investigated for two allied brachyuran species, Deiratonotus japonicus (Sakai, 1934) and D. tondensis Sakai, 1983 (family Camptandriidae), occurring in upstream brackish water areas of western Japan. Our observations on over 400 crab specimens from 13 localities, including the types, revealed that there were many specimens that could not be identified morphologically as either species by their diagnostic characters indicated in original descriptions. We grouped specimens into three morphological types of “D. japonicus”, “D. tondensis” and species‐unknown. Specimens of three morphological types were often found even in the same localities. Moreover, there was no correspondence between the morphological types and mitochondrial DNA haplotypes (COI, 540 bp), which was revealed by phylogenetic analyses using maximum likelihood methods and a statistical‐parsimony haplotype network constructed with the TCS computer program. In addition, genetic distance between “D. japonicus” type and “D. tondensis” type (0–1.7%) were in the intraspecific range of Crustacea. Thus, D. japonicus and D. tondensis ought to be treated as the same species and the latter nominal species as a junior synonym of the former. Significant genetic differentiation was recognized among populations with a positive correlation between geographic and genetic distances, suggesting isolation by distance. In consequence, a redescription of the newly defined Deiratonotus japonicus is presented, taking into account the newly recognized morphological variability in this species. Present address: Katsutoshi Watanabe, Graduate School of Science, Kyoto University, Sakyo‐ku, Kyoto, Japan

Population Subdivision of the Brackish-Water Crab Deiratonotus cristatus on the Japanese Coast

We investigated the genetic structure of populations of the brackish-water crab Deiratonotus cristatus (de Man, 1895) (family Camptandriidae) on the Japanese coast, together with morphological and the ecological variations. Genetic characteristics of the local populations based on mitochondrial DNA COI sequence data have revealed genetic differentiation between many populations, with the haplotype networks forming three geographical clades: a clade occurring on the Pacific coast, one occurring predominantly in northern Hokkaido, Kyushu and the Seto Inland Sea, and a third occurring in the Ryukyu Islands. Male pleopod morphology, carapace length relative to carapace width, and carapace width of adult crabs varied inconsistently among the geographic groups corresponding to the three clades. Life history traits were similar throughout, although differences in the breeding season were apparent between populations on the Pacific coast, and in the Seto Inland Sea and the Ryukyu Islands.

A new record of the Kumamoto oyster Crassostrea sikamea in the Seto Inland Sea, Japan

We collected 138 Kumamoto like oyster specimens in and around the Nakatsu tidal flat to monitor species diversity. The mitochondrial large subunit of ribosomal DNA (LSrDNA) and the nuclear ribosomal internally transcribed spacer-1 (ITS-1) region were amplified by polymerase chain reaction and restriction fragment length polymorphism analysis, leading to the discovery of the Kumamoto oyster Crassostrea sikamea in the Nakatsu tidal flat. A more accurate species identification using the nucleotide sequences for cytochrome c oxidase subunit I and ITS-1 confirmed the presence of the oysters. These results provide the first evidence of C. sikamea in the Seto Inland Sea of Japan.

New record of Sargassum denticarpum Ajisaka (Fucales, Phaeophyceae) from Iriomote Island (Ryukyu Archipelago, Japan)

Abstract The brown macroalgal genus Sargassum forms beds around the Japanese coast; these beds are important for marine ecosystem functioning and fisheries. In recent years, a northward shift in the distribution patterns of southern Sargassum spp. has been postulated as a result of warming in the western Pacific. To examine this theory, we surveyed species richness and diversity of genus Sargassum algae around the Ryukyu Islands, Japan, which is the northern limit of selected Sargassum species native to tropical and subtropical regions. We collected from Iriomote Island (Ryukyu Archipelago) specimens of a species resembling Sargassum denticarpum, which is endemic to Vietnam. The specimens had the following morphological characteristics in common with S. denticarpum: (1) terete or slightly compressed primary branches, (2) simple lanceolate primary and lateral leaves with dentate margins in all stages, (3) spherical-to-elliptical vesicles with or without spines and wings, (4) monoecious, and (5) compressed receptacles with spines on the margins. In addition, internal transcribed spacer 2 (ITS2) sequences of the Ryukyu specimens and of S. denticarpum collected in Vietnam clearly showed that the two are closely related. On the basis of these morphological and molecular characteristics, we present the first report of S. denticarpum in Japan.

Age and growth of three rockfish species, Sebastes inermis, S. ventricosus and S. cheni, in the central Seto Inland Sea, Japan

Inter-specific comparison of growth was conducted among three Sebastes species (Sebastes inermis, Sebastes ventricosus and Sebastes cheni) which have previously been treated as a single species before the 2008 taxonomic review. Fish were collected in April 2010 for DNA analysis and each month from June 2011 to May 2012 for growth analysis in the central Seto Inland Sea, southwestern Japan. AFLP analysis of each of the three Sebastes species confirmed significant frequency differences in fragments. The result supported the identification of the three Sebastes species based on the morphological characters. Analysis of otoliths from a total of 94 S. inermis, 125 S. ventricosus and 71 S. cheni showed that an opaque zone at the outer margin of the sagittal otolith increased from April to October and the zone was validated as an annual ring. Growth of the three Sebastes species was estimated using the von Bertalanffy growth formula. There was no significant difference in the growth formulas between males and females within each species. The growth patterns among the three Sebastes species were significantly different and S. inermis grows slower than S. ventricosus and S. cheni in the central Seto Inland Sea.