The vertical movements of one Mekong giant catfish Pangasianodon gigas were monitored for 3 days in August 2004 using a depth-temperature micro data logger. The logger was recovered using an innovative time-scheduled release system and located by searching for VHF radio signals. The logger was found approximately 2.2 km away from the release point and provided (n=705,128) depth and temperature data collected over a period of 98 hours following the release. The fish spent more than 99% of its time at less than 3 m below the surface. The maximum swimming depth was 5.6 m. No sharp thermocline was present during the experiment. Temperature did not have any detectable effect on the pattern of vertical movement of the fish. The dissolved oxygen concentration (DO) was stratified, with a concentration of >60% saturation in the first 3 m below the surface falling to 10% saturation at depths lower than 4 m. This specific DO stratification was found to limit the vertical movement of the catfish.

DNA methylation is an important epigenetic factor that participates in silencing genes. Genomic approaches to studying DNA methylation promise to be particularly fruitful, since DNA methylation is involved in global control of gene expression in many organisms. With its draft genome completed and a large quantity of available cDNA data, Ciona intestinalis is newly emerging as an invaluable model organism for investigating genome-wide gene expression and function. Here we examine the effects of 5-aza-2′-deoxycytidine (5-aza-CdR), a chemical that blocks CpG methylation, on the gene expression profile of early C. intestinalis embryos, using oligonucleotide-based microarray analysis. Embryos treated with 5-aza-CdR show delayed gastrulation and are developmentally arrested at the neurula stage. They subsequently lose cellular adhesion and finally die. Apoptosis was not detected in these embryos by TUNEL staining at 12 h, indicating that the defects observed did not result from 5-aza-CdR-induced apoptosis. Gene expression profiles of 12-h-old 5-aza-CdR-treated embryos compared to wild-type revealed 91 upregulated genes and 168 downreg-ulated genes. Although nearly half of these encoded proteins with unknown functions, several encoded cell-signaling molecules and transcription factors. In addition, genes associated with the stress response and cell defense were upregulated, whereas genes involved in cell adhesion were downregulated.

Gekkonid geckos, representing more than 85 percent of the gekkotan genera, are found on all major land masses and almost all oceanic islands in the tropics and subtropics. Intergeneric relationships of the Gekkonidae have been far more difficult to resolve than those among other gekkotan families. Our data set consists of a large number of complete mitochondrial 12S rRNA gene sequences and partial nuclear C-mos gene sequences for 33 genera of geckos, two genera of pygopods and two genera of eublepharids. Maximum parsimony (MP) and maximum likelihood (ML) trees were generated based on unweighted analysis using PAUP 4.0b10. Bayesian inference (BI) analyses trees were generated by MrBayes 3.0B4. All phylogenetic trees supported the monophyly of Gekkonidae with great confidence. The 12S data and combined data (12S and C-mos) place Sphaerodactylus deeply within gekkonine geckos, whereas Teratoscincus Pristurus are the sister group of the remaining gekkonids. However, it is known that 12S may be positively misleading when dealing with older divergences. Therefore, the conflict between the results in this study and the latest conclusions based on C-mos (Han et al., 2004) points to the need for future focus on the phylogenetic position of both Sphaerodactylus and Teratoscincus.

To elucidate the phylogenetic position of Lefua loaches from Aichi and Shizuoka Prefectures of Honshu Island, Japan, we determined their nucleotide sequences for the mitochondrial D-loop region and compared these to sequences from four other Lefua species: L. costata, L. nikkonis, L. echigonia, and L. sp. Loaches identified as L. sp. on the basis of morphology comprised a clade (the L. sp. Tokai population) that grouped together with L. echigonia; hence, the processes involved in evolution within the genus Lefua were unclear. We performed randomly amplified polymorphic DNA (RAPD) analyses to obtain genetic information on nuclear DNA. The RAPD patterns of the L. sp. Tokai population differed from those of the local L. echigonia and L. sp. populations. The L. sp. Tokai population was similar to L. echigonia with regard to mitochondrial DNA but differed from L. echigonia and L. sp. with respect to nuclear DNA; this indicated that the evolutionary background of the L. sp. Tokai population was unique. We suggest that introgression of mitochondria occurred from L. echigonia to the L. sp. Tokai population, and speculate on the process of evolution of the latter population of Lefua. As with six L. echigonia populations and two L. sp. populations, we regard the L. sp. Tokai population as an evolutionary significant unit (ESU) that qualifies for protection as an endangered loach.

The dietary items of five migratory shorebirds, Dunlin (Calidris alpina), Red-necked Stint (C. ruficollis), Grey Plover (Pluvialis squatarola), Whimbrel (Numenius phaeopus) and Black-headed Gull (Larus ridibundus), were examined by analyses of fecal droppings during the birds' migration or wintering and by surveys of macrobenthic fauna around their foraging sites on the tidal flats of Fujimae-higata, Nagoya, central Japan. Body parts of nereidid, capitellid, and spionid polychaetes and crustaceans were found in fecal droppings from all of these shorebirds. Two nereidid species (Hediste diadroma and Neanthes succinea) with relatively large body sizes seemed to be the majority dietary items. At one site, H. diadroma was dominant in terms of biomass (40–370 g/m²) throughout year except, for less than 1 g/m² in March and May (within or just after reproduction of this species). Monthly changes in the occurrence of food items in fecal droppings of C. alpina were examined in 1999 and 2000. Most (85–100%) of the fecal droppings contained nereidid body parts, including Hediste-specific simple chaetae from November to April, whereas only 23% of the droppings contained them in May. Chaetae of capitellid or spionid polychaetes were frequently found from January to April (38–86% of droppings). Crustacean body parts, including amphipod appendages, were frequently found from March to May (86–100% of droppings). The relationship between foraging habits of the shorebirds and the life history of their major prey nereidid species is discussed.

A cDNA encoding prepro-thyrotropin-relaesing hormone (ppTRH) in chicken (Gallus gallus) was isolated and the sites of expression in the brain were determined. The chicken ppTRH cDNA encodes 260 amino acids, including four TRH progenitor sequences (-Lys/Arg-Arg-Gln-His-Pro-Gly-Lys/Arg-Arg-). It is interesting to note that chicken ppTRH harbors four TRH progenitor-like sequences. According to the hydropathy profile of chicken ppTRH, not only the TRH progenitor sequences but also the TRH progenitor-like sequences are localized in hydrophilic regions. The TRH progenitor-like sequences might be related to structural conservation in the evolution of ppTRH, although they cannot be processed into TRH due to the mutation of several amino acids. According to the alignment of the deduced amino-acid sequences of known vertebrate ppTRHs and the molecular phylogenetic tree we constructed, we speculate on the molecular evolution of ppTRH in vertebrates. In situ hybridization demonstrated experession of the ppTRH gene in the nucleus preopticus periventricularis, nucleus preopticus medialis, regio lateralis hypothalami, paraventricular nucleus, nucleus periventricularis hypothalami, and nucleus ventromedialis hypothalami in the chicken brain.

Wild-type medaka are known to have remarkable capabilities of fin, or epimorphic, regeneration. However, a hypothyroid mutant, kamaitachi (kmi), frequently suffers from injury in fins, suggesting an important role of thyroid hormone in fin regeneration. This led us to examine the relationship between thyroid hormone and fin regeneration using medaka as a model. For this, we first set up a medaka experimental system in which the rate of regeneration was statistically analyzed after caudal fin amputation under normal and hypothyroid conditions. As expected, the regeneration of amputated caudal fins was delayed in hypothyroid kmi –/– mutants. We then examined wild-type medaka with thiourea-induced hypothyroidism to evaluate the requirement of thyroid hormone during epimorphic fin regeneration. The results demonstrate that the growth rate of regenerates was much reduced in severely hypothyroid medaka throughout the regeneration period. This reduction in regenerative rate was recovered by exogenous administration of L-thyroxine. The present study is thus the first to report the direct involvement of thyroid hormone in teleost fin regeneration, and provides a basic framework for future molecular and genetic analyses.

The shell-less, endoparasitic gastropod, Asterophila japonica Randall and Heath, 1912, was collected from two species of sea star, Leptychaster anomalus Fisher, 1906 and Ctenodiscus crispatus (Retzius, 1805) in Toyama Bay, Japan. All observed individuals were located on the aboral side of the host's disk (except one specimen parasitizing the arm) between the epidermis and the coelomic epithelium. More than one large individual frequently co-occur on a single host. The body plan of A. japonica is surprisingly modified from that of general gastropods; organs unrelated to digestion and reproduction are greatly reduced, simplified or completely lost. Dimorphism of body size is striking between males and females: males are much smaller than females and are attached to the surface of the pseudopallium of females. Females deposit and brood an egg mass(es) in the pseudopallial cavity until the eggs develop to veliger larvae. At the late developmental stage, brooded larvae reduce the velum and develop the foot for crawling, suggesting lecithotrophic development with or without a short planktonic stage. It is uncertain as to how the larvae can find and parasitize the next generation of the host. The systematic placement of Asterophila in the family Eulimidae is supported by three characters, viz. parasitism on echinoderms, smooth hydrophobic protoconch, and the enclosure of the visceral mass with the pseudopallium.

Peripheral neuronal somata are scattered throughout the enteric nervous system (ENS) in Aplysia. We found that somata on the outer surface of the digestive tract were more densely distributed on the stomatogastric ring and the posterior gizzard than on other regions. In preparations with or without the central nervous system, two types of synchronous bursting activity were recorded from the nerves of the ENS. Some of the synchronous bursts were recorded from nerves on the crop and stomatogastric ring, whereas others were recorded from nerves on the crop, stomatogastric ring, and gizzard. Experiments using preparations in which the different regions were separated suggested that the former bursts originated in neurons on the crop and the latter originated in neurons on the gizzard. Axonal projections of neurons on the different regions were examined by backfilling and analysis of the direction of impulse conduction. Blocking chemical synapses in separated gizzards depressed EPSP-like potentials and eliminated the bursting activities. When chemical synapses on the crop and stomatogastric ring but not on the gizzard were blocked in a whole digestive tract preparation, bursting activity recorded from nerves on all the regions was decreased, although the frequency of the bursting rhythm did not change. Stimulation of a neuron on the crop elicited bursts in nerves on the gizzard. These results suggest that chemical synaptic connections and a feedback loop along the digestive tract coordinate the synchrony of bursting activity originating in the gizzard.

The Y chromosome has recently come into the spotlight as a new and efficient genetic marker for tracing paternal lineages. We reconstructed cetacean phylogeny using a 1.7-kbp fragment of the non-recombining Y chromosome (NRY), including the SRY gene and a flanking non-coding region. The topology of the Y-chromosome tree is robust to various methods of analysis and exhibits high branch-support values, possibly due to the absence of recombination, small effective population size, and low homoplasy. The Y-chromosome tree indicates monophyly of each suborder, Mysticeti and Odontoceti, with high branch support values (BS≥86%; PP≥98%). In the Odontoceti clade, three superfamilies, Physeteroidea, Ziphioidea, and Delphinoidea, diverged soon after the split between Mysticeti and Odontoceti. Our analysis allows resolution of this rapid radiation and indicates that Physeteroidea is basal in the Odontoceti clade (BS, 99%; PP, 100%; MBS, 61%). The major split within the superfamily Delphinoidea is between the Delphinidae clade and the Monodontidae Phocoenidae clade. The phylogenetic relationships among delphinid species are ambiguous, probably because of the rapid radiation of this family. In the Mysticeti clade, the first major split is between Balaenidae and Balaenopteridae; within Balaenopteridae, a Balaenoptera acutorostrata B. bonaerensis (minke whales) clade forms a sister clade with the other balaenopterid species. Megaptera novaeangliae is nested within Balaenoptera, making the latter paraphyletic. The low homoplasy exhibited by the Y-chromosome data presented here suggests that an extended data set incorporating longer sequences would provide better resolution of cetacean lower-level pylogeny.

A new ice bug species, Galloisiana odaesanensis sp. nov., is described from Mt. Odae, Pyeongchang-gun, Gangwon-do, South Korea. This species resembles the G. yuasai group in having a short body (less than 20 mm), distinct compound eyes, fewer than 35 antennomeres, and seven or eight cercomeres. The species is, however, clearly distinguished from the G. yuasai group by the following characters: slightly curved supra-anal plate with dull apical margin; rectangular pronotum that is straight on the posterior; 3rd antennomere 1.7 times as long as the 2nd. The distribution of the genus Galloisiana is discussed and a key for Galloisiana species is presented.

We conducted an electrophoretic survey to examine systematic relationships of a lotic-breeding salamander Hynobius okiensis endemic to Dogo Island of the Oki Islands, Japan, with several lentic and lotic-breeding Japanese species. Genetically H. okiensis with 2n=56 chromosomes was closer to the lentic-breeding H. nebulosus group (H. nebulosus and H. dunni) with the same chromosome number than to the lotic-breeding H. naevius group (H. naevius and H. kimurae) and H. boulengeri with 58 chromosomes. Chromosome number reduction from 58 to 56, possibly accompanied with a change in breeding environment from streams to still waters, is estimated to have first occurred in the nebulosus group of Hynobius. A reversal only in breeding habits then seems to have followed in steep, montane environments of the small island of Dogo, resulting in the speciation of H. okiensis.

We studied morphological and allozymic variation in populations of Japanese salamanders, Hynobius boulengeri and H. stejnegeri. Adult H. boulengeri showed sexual dimorphism, and juveniles differed greatly from adults in many morphological characters. From the results of multivariate analyses of morphological characters, the populations were divided into four groups: (I) H. boulengeri from Honshu, (II) H. boulengeri from Shikoku, (III) H. boulengeri from the Sobo-Katamuki Mountains of Kyushu and H. stejnegeri, and (IV) H. boulengeri from the Amakusa Islands and the Osumi Peninsula. Phenotypic relationships among the four groups were identical to relationships clarified by allozymic analyses, except for group IV, which was included in group III in the allozyme tree. Some morphometric characters were significantly correlated with environmental variables. We consider H. stejnegeri to be a valid species based on its unique color pattern, morphometric characters, and allelic composition, even though it was nested within group III of H. boulengeri by both morphological and allozymic analyses. We propose that group I from Honshu and group II from Shikoku should be treated as H. boulengeri sensu stricto and H. hirosei, respectively. Resolving the taxonomic status of the remaining populations of groups III and IV from Kyushu requires further study.