Mutsumi Nishida

Geographic Variation in the Molecular, Morphological and Reproductive Characters of the Ayu Plecoglossus altivelis (Plecoglossidae) in the Japan-Ryukyu Archipelago

In an attempt to clarify geographic variation in the ayuPlecoglossus altivelis, the molecular, morphological and reproductive characters of populations from various localities in the Japan-Ryukyu Archipelago were examined. An electrophoretic analysis of enzymes encoded by 18–28 loci and univariate and multivariate analyses of 12 meristic and 17 morphometric characters indicated that there are two distinct groups of ayu in the archipelago: that of the Japan Islands and that of the Ryukyu Islands. Within the Japan Islands group, a landlocked population of Lake Biwa was found to diverge somewhat from other amphidromous populations genetically and morphologically. The Lake Biwa population was noted as being by far the most fecund, departing from a north-south cline of fecundity observed in amphidromous populations. Though no virtual divergence was observed among amphidromous populations in the Japan Islands in molecular data, divergence among these populations was considerable in morphological and fecundity data. Differences in geographic variation patterns are attributed to qualitative differences inherent in molecular and organismal characters: organismal characters are responsive to selection and also directly altered by environmental influences in part but molecular characters are hardly so. The evolution of different characters may have proceeded at different rates among geographic populations of ayu.

The Social and Mating System of the Maternal Mouthbrooder Tropheus moorii (Cichlidae) in Lake Tanganyika

Territorial behaviour, reproduction and migration of the epilithic algal eater,Tropheus moorii, were investigated in Lake Tanganyika, Africa. Adults of both sexes had individual feeding territories which adjointed each other. Males, who occupied higher rocks than females, usually stayed at the same sites for more than 5 months. Females left their territories to pair with males in the males’ territories. Paired females actively foraged under the protection of their mates for up to 3 weeks prior to spawning. After spawning, females usually settled in a site unoccupied by territory-holders to mouthbrood the offspring for a month. An examination of the ovaries and a removal experiment of dominant males suggest that females cannot attain fully mature ovaries in their own territories and choose males whose territories can provide enough food to satisfy their nutritive demand. The evolution of a number of local colour morphs in this fish is briefly discussed in relation to social selection.

A new subspecies of the ayu,Plecoglossus altivelis, (Plecoglossidae) from the Ryukyu Islands

A new subspecies of the ayu,Plecoglossus altivelis ryukyucnsis, is described on the basis of specimens from Amami-oshima and Okinawa Islands, the Ryukyu Islands, Japan. This new subspecies is distinguished fromP. altivelis altivelis by the fewer numbers of pectoral fin rays, longitudinal scales and scales above and below the lateral line, and also by the unique electrophoretic mobilities of several enzymes.

Revision of the systematics of the cardinalfishes (Percomorpha: Apogonidae) based on molecular analyses and comparative reevaluation of morphological characters

Molecular analyses were conducted based on 120 of the estimated 358 species of the family Apogonidae with 33 of 40 genera and subgenera, using three gobioids and one kurtid as collective outgroups. Species of Amioides, Apogon, Apogonichthyoides, Apogonichthys, Archamia, Astrapogon, Brephamia, Cercamia, Cheilodipterus, Fibramia n. gen., Foa, Fowleria, Glossamia, Gymnapogon, Jaydia, Lachneratus, Nectamia, Ostorhinchus, Paroncheilus, Phaeoptyx, Pristiapogon, Pristicon, Pseudamia, Pterapogon, Rhabdamia, Siphamia, Sphaeramia, Taeniamia, Verulux, Vincentia, Yarica, Zapogon and Zoramia were present in the molecular analyses; species of Bentuviaichthys, Holapogon, Lepidamia, Neamia, Paxton, Pseudamiops and Quinca were absent from the analyses. Maximum-likelihood (ML), Bayesian (BA), and Maximum parsimony (MP) analyses based on two mitochondrial (12S rRNA-tRNAVal-16S rRNA, ca. 1500 bp; COI, ca. 1500 bp) and two nuclear DNA (RAG1, ca. 1300 bp; ENC1, ca. 800 bp) fragments reproduced two basal clades within the monophyletic family: one including a single species, Amioides polyacanthus, and the other comprising species of Pseudamia. All the other apogonid species formed a large well-established monophyletic group, in which almost identical 12 major clades were reproduced, with phylogenetic positions of four species (Glossamia aprion, Ostorhinchus margaritophorus, Pterapogon kauderni, and Vincentia novaehollandiae) left unsettled. Apogon sensu lato and recent Ostorhinchus (excepting O. margaritophorus) were divided into six and three major clades, respectively. Each of the recognized clades in the family was then evaluated for morphological characters to identify synapomorphies. Based on the results of the molecular analyses and the reevaluation of morphological characters, four subfamilies were proposed within the family: Apogoninae (including most of the species in the family), Amioidinae new subfamily (including Amioides, and based on morphology, Holapogon), Paxtoninae new subfamily (including Paxton, based only on morphology) and Pseudamiinae (including Pseudamia). Within the largest subfamily Apogoninae, twelve new tribes were proposed based on the 12 molecular clades and associated morphology: Apogonichthyini, Apogonini (mainly including species of Apogon sensu stricto), Archamiini, Cheilodipterini, Gymnapogonini, Ostorhinchini (including striped species of recent Ostorhinchus), Pristiapogonini, Rhabdamiini, Sphaeramiini (mainly including barred species of traditional Ostorhinchus, such as Apogonichthyoides, Jaydia and Nectamia), Siphamiini, Veruluxini, and Zoramiini. Two additional tribes are proposed based only on morphology: Glossamiini and Lepidamiini. For each of the 14 tribes, morphological characters were described. One new genus, Fibramia, type species Apogon thermalis, recently in Ostorhinchus, was described supported by morphology and molecular trees. A key to all genera is provided and all valid and uncertain status species are allocated to tribes and genera.

Genetic relationship among Japanese sentinel crabs (Decapoda: Ocypodidae: genus Macrophthalmus).

Seven species (eight populations) of sentinel crabs (genus Macrophthalmus) from the Japan coast and Uca vocans and Ocypode ceratophthalma, were examined electrophoretically for genetic variations in 13 enzymatic and one non-enzymatic protein comprising 17 loci. Most species were highly differentiated from each other (Neis genetic distance, 0.29-1.63). The least genetic distance was found between M. japonicus and M. banzai, the genetic distinctiveness of the two taxa being supported by three divergent loci with no common allele. The genetic relationships among Macrophthalmus species differed greatly from those inferred from morphological features, with a UPGMA tree suggesting that the sub-genus Macrophthalmus is polyphyletic.

Comparative phylogeography of diadromous and freshwater daces of the genus Tribolodon (Cyprinidae)

Far Eastern daces, genus Tribolodon (Cyprinidae), are thought to have diversified and developed unique diadromous life histories under changing conditions in the Sea of Japan and the surrounding environment. To examine the relationships between life history traits, distribution, and genetic population structures, we conducted a comparative phylogeographic analysis using partial mtDNA sequence data from samples collected over almost the full ranges of all four Tribolodon species. Phylogenetic analyses revealed several intraspecific haplotype groups that differentiated in the early Pleistocene to the Pliocene with or without geographic overlaps. A time-calibrated phylogeny suggested that the relatively smaller geographic ranges of the strictly freshwater species, T. sachalinensis and T. nakamurai, were explained not by the recent origins of these species, but by their limited dispersal abilities and smaller historical population sizes. The wider-ranging diadromous species, T. brandtii and T. hakonensis, exhibited similar major phylogeographic structures in their distributions, but the chronological order and timing of formation of this structure largely differed between the two species. In addition to those differences, the overlapping patterns of the differentiated intraspecific lineages in these species suggest dynamic, but somewhat restricted dispersal during the Plio-Pleistocene. Tribolodon hakonensis, one of the most widespread species of East Asian freshwater fishes, included both common and unique phylogeographic patterns compared to other fish species; the unique patterns (i.e., its wide range across freshwater biogeographic boundaries like the sea and mountains) would reflect its ecological features as a remarkable generalist inhabiting lakes, upper and lower reaches of rivers, and even coastal areas.