Cyclic GMP is a ubiquitous intracellular second messenger produced by guanylyl cyclases (GCs). The enterotoxin/guanylin receptor type membrane GC (designated as GC-C in mammals) is activated by exogenous ligands such as heat-stable enterotoxins (STa), small peptides secreted by some pathogenic strains of Escherichia coli which cause severe secretory diarrhea and also activated by endogenous ligands such as guanylin and uroguanylin. The STa/guanylin receptor type membrane GC, as well as other type membrane GCs, is composed of an extracellular domain, a single transmembrane domain, and an intracellular region comprising a kinase-like domain and a catalytic domain. The STa/guanylin receptor type membrane GC is identified in various vertebrates including fishes, amphibians, reptiles, and birds, implying that it serves some important and undefined physiological roles in the intestine of non-mammalian vertebrates, e.g. the regulation of water and salt absorption. In mammals, only a single membrane GC (GC-C) is known to be the STa/guanylin receptor. On the contrary, two membrane GC cDNAs are cloned from the intestine of the European eel Anguilla anguilla (GC-C1 and GC-C2) and the medaka fish Oryzias latipes (OlGC6 and OlGC9). OlGC6 and OlGC9 are structurally distinct and show different ligand responsibility. Accumulated evidences indicate that the transcriptional regulatory mechanism of the human GC-C gene is different from that of the corresponding medaka fish GC gene; the human GC-C gene is regulated by Cdx2 and/or HNF-4, and the medaka fish OlGC6 gene is regulated by OlPC4, which is a medaka fish homologue of the mammalian transcriptional positive co-factor 4 (PC4). Furthermore, the transcriptional regulatory mechanism of the OlGC9 gene is different from those of both the OlGC6 and human GC-C genes, indicating that the study on these two medaka fish GCs will be useful for further understanding of the STa/guanylin receptor type membrane GC in the vertebrates.

The compact genome of the ascidian Ciona intestinalis has been sequenced. Chromosome karyotype and mapping of the genome sequence information on each of the 14 pairs of chromosomes are essential for genome-wide studies of gene expression and function in this basal chordate. Although the small chromosome size (most pairs measuring less than 2 μm) complicates accurate chromosome pairing based on morphology alone, the present results suggest that 20 chromosomes are metacentric and 8 are submetacentric or subtelocentric, and two pairs of large chromosomes (#1 and #2) were defined. The characterization of chromosomes by FISH and staining with propidium iodide indicated that 18S/28S ribosomal gene repeats are present in the short arms of three pairs of chromosomes and that the short arms of these pairs show remarkable size polymorphism. In addition, each chromosome was characterized molecular cytogenetically by mapping representative BAC clones with FISH. The present study is therefore a first step in expanding the karyotype analysis and entire physical mapping of the genome sequence of Ciona intestinalis.

The Japanese rosy bitterling, Rhodeus ocellatus kurumeus, has been affected not only by the invasion of another subspecies, R. o. ocellatus, from China, but also by habitat fragmentation. In this study, the effects of habitat fragmentation on the fitness of R. o. kurumeus were investigated. Owing to exclusion by R. o. ocellatus, R. o. kurumeus in Honshu and Shikoku has disappeared entirely, except for small populations in isolated man-made ponds in Osaka and Kagawa. In Kyushu it still occupies open water systems, into which R. o. ocellatus has only recently invaded. Meristic and genetic data show that the diversity of R. o. kurumeus is significantly lower in the isolated Osaka and Kagawa populations than the non-isolated Fukuoka population. The Osaka population is inferior to the Fukuoka population in terms of viability and growth. The viability of reciprocal inter-population hybrids between the Osaka and Fukuoka populations was, however, as high as that of the Fukuoka population. In addition to the high scores of band sharing index (BSI) in RAPD-PCR analysis, acceptance of transplanted scales among individuals, irrespective of natal pond, indicates that the Osaka population forms a highly inbred line. These results suggest that low genetic variation is associated with inbreeding depression in the small isolated Osaka populations. Consequently, the management of ponds, including the free movement of individuals, in addition to measures to prevent the invasion of R. o. ocellatus, is necessary for the conservation of R. o. kurumeus.

The Western Ghats of Southwestern India are known as one of the world's “hotspots” of biodiversity. We collected frog specimens from the family Ranidae and investigated the phylogenetic relationships among ranid species, particularly among the Fejervarya, a genus whose morphological diagnostic characteristics and phylogenetic features remain little known. We analyzed partial sequences of the mitochondrial 12S (428 bp) and 16S rDNAs (549 bp). Results showed that the members of Fejervarya form a monophyletic group with the genera Hoplobatrachus and Euphlyctis among ranid genera. This confirms the recent allocation of Fejervarya, including it within the subfamily Dicroglossinae. The mitochondrial rDNA data in our study also appeared to be useful as a marker to distinguish Fejervarya species without morphological differences. The phylogenetic tree based on the 16S rDNA sequence showed a correlation between Fejervarya phylogenies and their geographic distributions. Lastly, our results suggested the recent occurrence of a radiation event of Fejervarya species in the Indian-Sri Lankan region.

The planarian brain has an inverted-U shaped structure with functional regionalization. To investigate how each region in the brain connects to each other, we traced neural projections by microin-jection of fluorescence dye tracers. We found that external light and olfactory/taste signals received in the head region are conveyed in the main lobes (sponge region) of the brain. Chemosensory neurons distributed in the lateral branches project to the peripheral region of the sponge and visual neurons project to the medial region of the sponge. Parts of the sensory neurons project directly to the corresponding sensory neurons on the opposite side of the brain. However, all of the dye labeled brain neurons in the left and right lobes connect to each other via commissural neurons in the central region of the sponge. In addition to these observations, we detected regional differences in the planarian visual neurons. Posterior visual neurons have ipsilateral projection, but anterior visual neurons project to the contralateral side of the brain. A pair of longitudinal ventral nerve cords (VNC) connect to the brain on the ventral side, suggesting that they transmit signals which are integrated and processed in the brain. We also detected the direct connection of neurons in the brain and those of the pharynx, even though most pharynx neurons connect to VNC neurons. Here, we report for the first time on neural connections in the planarian central nervous system after overcoming technical difficulties specific to flatworms.

High-accuracy location data of wildlife telemetry using conventional satellite location systems are difficult to obtain. However, such data are necessary to clarify the nature of movements and home range sizes of animals. In order to measure the high-accuracy location data, we developed new GPS-Argos Platform Terminal Transmitters (PTTs) which transmit both the conventional location and GPS location simultaneously. Two experiments, one in an artificial rearing pond and the other in the open sea, were performed. First, two hawksbill turtles were tracked with the PTTs in a 5 ha breeding pond in Thailand. Their home ranges using both data were calculated and found to be 2.96 ha and 0.93 ha by the GPS data, and 156,740 ha and 184,478 ha by a conventional data. Secondly, a female green turtle attached with the GPS-Argos was released from the coast of Pangnga Province, Thailand. There was a relationship between depth and speed of travel based on the GPS data. The data from the PTT showed that the turtle moved south along the coastline at the depth of less than 20 m for 5 days, and then stayed at a depth of less than 10 m for 4 days. However, we could not find any clear relationship using conventional data. Only a meandering movement at a variety of depths was observed. The results of the two experiments indicated the PTTs have an enormous potential for enhancing our understanding of fine-scale movement patterns and home ranges of marine turtles.

Telmatochromis temporalis is a bi-parental substrate brooding cichlid endemic to Lake Tanganyika. Paired males were always larger than their mates and had territories around nests against con-specific males. However, males smaller than the paired females were found in 18% of the nests. Here we report a reproductive tactic of these small males. The small males had as heavy gonads as paired males, and the gonad somatic index (GSI) of the small males was much higher than that of the latter. The examinations of the paternity and maternity using microsatellite-DNA as a genetic marker revealed that the small males were not genetically related to the pair members, and sired some young in 3 of 5 nests. These small males did not guard the broods, suggesting that they are likely to perform reproductive parasitism as sneakers. Paired males could not enter their spawning nests due to their large size, which made it difficult to chase out sneakers once they entered the nest. Some males as small as the sneakers were found outside the territories of paired males, and their gonads were quite small. Circumstantial evidence suggests that small males have two alternative investment patterns: investing in gonad to be sneakers, and investing in growth to probably be territorial males.

We presented the tachinid fly Exorista japonica with moving host models: a freeze-dried larva of the common armyworm Mythimna separata, a black rubber tube, and a black rubber sheet, to examine the effects of size, curvature, and velocity on visual recognition of the host. The host models were moved around the fly on a metal arm driven by motor. The size of the larva, the velocity of movement, and the length and diameter of the rubber tube were varied. During the presentation of the host model, fixation, approach, and examination behaviours of the flies were recorded. The fly fixated on, approached, and examined the black rubber tube as well as the freeze-dried larva. Furthermore, the fly detected the black rubber tube at a greater distance than the larva. The rubber tube elicited higher rates of approach and examination responses than the rubber sheet, suggesting that curvature affects the responses of the flies. The length, diameter, and velocity of host models had little effect on response rates of the flies. During host pursuit, the fly appeared to walk towards the ends of the tube. These results suggest that the flies respond to the leading or trailing edges of a moving object and ignore the length and diameter of the object.

Chlamydomonas has two actin genes: one encoding a conventional actin (90% amino acid identity with mammalian actin) and the other a highly divergent actin (NAP; 64% identity). The expression of the two genes is regulated in a mutually exclusive manner. Thus, ida5, a mutant that lacks the conventional actin (CrA) gene, expresses NAP abundantly, whereas wild-type cells express NAP only negligibly under normal conditions. To explore the physiological significance of the two actins, chimeric genes with the 5′ upstream region of one gene replaced by that of the other were constructed and used to transform ida5. The transformant (TF5) with a chimeric clone comprising the 5′-untranslated region from the NAP gene and the CrA-encoding sequence recovered the dyneins missing in ida5 and showed almost normal motility. After deflagellation of this transformant, however, only about 30% of cells grew flagella, unlike wild-type cells, >80% of which displayed reflagellation. Transformant TF10, which contains the CrA upstream region and NAP coding region, underwent reflagellation normally, as did the parent strain, ida5. In TF5, the mRNA level of both CrA and NAP was increased greatly during reflagellation. In light of the recent finding that NAP mRNA is expressed transiently upon reflagellation in wild-type cells, the described results suggest that 1) the expression of NAP mRNA is indispensable for flagellation and 2) robust expression of CrA may inhibit proper flagellation by interfering with the function of NAP in the early stages of reflagellation.

One species of Hemichordata, Balanoglossus misakiensis, is then acorn worm originally reported from the intertidal zone of the Miura Peninsula on the Pacific Ocean side of Japan. We histologically examined the reproductive cycle of the population of this species, which inhabits only the sublittoral zone in the Sea of Japan. Testes and ovaries began to develop at the beginning of May 2003 and were almost mature in the latter half of June in males and in the first half of July in females in the same year. Subsequently, spermiation and spawning followed in the latter half of July in males and in the first half of August in females. Progress in maturation appeared to be related to increases in the water temperature. Although some experiments were conducted in aquariums to identify the conditions responsible for the synchronization of the occurrence of spontaneous spawning/spermiation, no clues were obtained. During the experiments, however, 11, 2, and 4 individuals out of the 67 used achieved spawning/spermiation on separate days. The occurrence of spawning/spermiation in the laboratory corresponded to the latter half of the switch from high tide to low tide on those days. Also in the field, it was known that they released the gametes according to this specific schedule. Therefore, it was suggested that, in the Japan Sea population of this species, the tide level may be a condition for synchronized spawning/spermiation.

In the territorial damselfly Calopteryx atrata Selys, length of the hindwing, the wing areas and the aspect ratio did not differ significantly among age classes during the pre-reproductive period, while the body mass of males increased about 2.5 times. This is due primarily to increase in mass of thorax and abdomen. The flight muscle mass accounted for the great part of the thorax mass, and began to increase from early in the pre-reproductive period and continued increasing until sexual maturation. The average flight muscle mass of sexually matured males was about 2.4 times of that of the youngest immature ones. On the other hand, the abdomen mass and total lipids increased remarkably in the latter half of the pre-reproductive period. The average total lipid content of mature males was about tenfold of that of the youngest immature ones. The maximum lift production per flesh body mass was positively correlated with the flight muscle mass and total lipid content. Such an increase in flight muscle mass and lipid reserves resulted in the increase of maximum lift force, and probably enhanced flight performance.

This study reported the isolation and characterization of eight polymorphic microsatellite loci in endangered forest musk deer Moschus berezovskii. An improved enrichment protocol was used to isolate microsatellites, and polymorphism was explored with samples from wild musk deer population collected in Miyalo of Sichuan Province in China. Approximately 70% of clones from the genomic library constructed in current study contained dinucleotide (AC) repeats. Eight microsatellite loci amplified were highly polymorphic within forest musk deer population. The number of alleles per locus ranged from 6 to 14, and the observed and expected heterozygosities ranged from 0.41~1.0 and from 0.8~0.9, respectively. The average polymorphic information content (PIC) value for these markers was 0.82. This demonstrated that the eight microsatellite loci developed here are highly polymorphic, and can be used as genetic markers for further investigation of musk deer. Also, the results showed that the musk deer distributed in Miyalo had a relatively higher level of genetic variation.

A new draconematid nematode species of the genus Dinetia Decraemer and Gourbault, 1997 is described from the subtidal sediments and small logs from the eastern coast of South Korea. Dinetia orientalis n. sp. mainly differs from D. nycterobia Decraemer and Gourbault, 1997 by the following characters: large number of cephalic adhesion tubes (38–42 in male and 37–40 in female), number of posterior sublateral adhesion tubes (9–11 in male and 13–14 in female) and posterior subventral adhesion tubes (17–22 in male and 19–24 in female), the buccal cavity (narrow and armed with a dorsal and two weak ventrosublateral teeth), spicules (strongly arcuated and with a pair of strongly dilated gubernaculums around distal part of spicules), and higher “c” value (8.3–10.4 in male and 8.5–10.7 in female). This is the first report on free-living marine nematodes from South Korea, and the first record of the genus Dinetia in the Northwest Pacific.