Gonadotropin-releasing hormone (GnRH) plays a central role in the control of reproductive function in vertebrates. In salmonids, salmon GnRH (sGnRH) secreted by preoptic GnRH neurons regulates gonadal maturation through stimulation of synthesis and release of pituitary gonadotropins (GTHs). In addition, several lines of our evidence indicate that sGnRH is involved in spawning behavior, and serves to integrate the gonadal maturation with the reproductive behavior. A growing number of studies show that the effects of GnRH are mediated by multiple subtypes of GnRH receptors, successive multiple signaling pathways, and finally multiple transcription factors which act cooperatively to stimulate transcription of GTH subunit genes. This complex regulatory system of the action of GnRH may serve as a molecular basis of divergent physiological strategies of reproductive success in various vertebrate species. In this article, recent data on the molecular mechanisms of action of GnRH are reviewed with special reference to the regulation of synthesis and release of GTHs in the pituitary of salmonids to elucidate the multifunctional action of GnRH.

Broadcast-spawning corals expel eggs and sperm, and the fertilized eggs develop into planulae in the water column. As these sessile corals generally disperse during the planktonic larval stage, their larval characteristics (e.g., survival and settlement rates) are thought to be important for their dispersal. Although some studies of coral larval dispersal have focused on the maximum time that larvae can remain viable and settle, the relevance of this maximum settlement competency period for long distance dispersal remains unclear. To examine the relationship between competency periods and genetic differentiation, we performed laboratory experiments to investigate settlement rates of planulae and determine the degree of genetic differentiation in Acropora digitifera in the Ryukyu Archipelago, southern Japan. In addition, we compared our findings to published data for A. tenuis, which was studied using our methods. Our results indicated that the maximum settlement competency period was lower in A. digitifera planulae (54 days) than in A. tenuis (69 days) planulae. The mean survival rates at 45 days and 59 days after spawning were less than 10%. Furthermore, percentages of planulae that remained viable and settle at 30 days after spawning (survival rate × settlement rates at 30 days) were approximately 18% and 25% in A. digitifera and A. tenuis, respectively. By contrast, gene flow (N_em: number of migrations per generation) was significantly higher in A. digitifera (7.8 to 41.4) than in A. tenuis (3.1 to 22.5). These results indicate that the settlement competency period and survival rates are unlikely to be robust predictors of gene flow. Overall, we detected significant genetic differentiation between Kerama and Okinawa in A. digitifera. As direct observation of planula dispersal between Kerama and Okinawa has been reported, we concluded that genetic mixing is not complete, but that some localized planulae may disperse from Kerama to Okinawa via a specific current depending on reef or locality.

Sequence analyses of the non-coding, control region (CR) and coding region of the ND4-tRNA^Ser genes in the mitochondrial DNA (mtDNA) were conducted for populations of the ayu Plecoglossus altivelis altivelis and the Ryukyu-ayu P. a. ryukyuensis. The level of genetic differentiation between the two subspecies evaluated from the CR data was substantially low, when comparing with that estimated from ND4-tRNA^Ser gene region data, as well as those from nuclear genome data sets. By contrast, the differentiation between subspecies in the ND4-tRNA^Ser gene region was substantial, being consistent with the results from the previous nuclear genome analyses. Results of UPGMA and minimum spanning network analyses also implied the unexpected ceiling of genetic differentiation in the CR. These results suggest that the CR does not reflect accurately the level of overall genetic differentiation between the populations of the ayu, but other coding regions of the mtDNA do reflect it so that the mtDNA on the whole may function as a rich source of useful markers for genetic assessment of populations of this species.

Nine species of psychrolutids kept in the Marine Zoology of Hokkaido University were found to carry eight species of copepod parasites. The parasites and their hosts are: Bobkabata kabatabobbus Hogans and Benz, 1990 on Malacocottus zonurus Bean; Chondracanthus parvus n. sp. on Eurymen gyrinus Gilbert and Burke; Chondracanthus yabei n. sp. on Dasycottus setiger Bean and M. zonurus; Ch. yanezi Atria, 1980 on Psychrolutes phrictus Stein and Bond; Caligus similis n. sp. on Neophrynichthys latus (Hutton); Clavella adunca (Strøm, 1762) on M. zonurus; Neobrachiella amphipacifica Ho, 1982 on Ambophthalmos angustus (Nelson), Cottunculus sp., D. setiger, Ebinania brephocephala (Jordan and Starks), E. vermiculata Sakamoto, and P. phrictus; and Naobranchia occidentalis Wilson, 1915 on D. setiger and M. zonurus. Chondracanthus parvus is closest to Ch. deltoideus Fraser, 1920, but differs from it in having only one pair of small knobs on the head and carrying a pair of lateral processes on the second pediger. Chondracanthus yabei resembles Ch. yanezi Atria, 1980, but can be distinguished from it by the presence of three, low protrusions on the mid-dorsal surface of the trunk; besides, maxillule also shows difference. As the name indicates, C. similis resembles several species of Caligus that bear a short abdomen and a formula of I; IV on the exopod of leg 4. However, it can be separated from them by the combination of the following characters: a genital complex distinctly smaller than the cephalothoracic shield, a pair of relatively short caudal rami, a smooth dentiform process on maxillule, and a pair of truncate tines on sternal furca.

Analysis of the occurrence of Chondracanthus on the psychrolutid fishes shows that the phylogeny of Chondracanthus is in congruence with that of the Psychrolutidae. It implies that parasitism of Chondracanthus occurred after the Dasycottus clade diverged off the main stock of the Psychrolutidae and the occurrence of Ch. yabei on D. setiger is resulted from a later colonization.

Mitochondrial DNA cytochrome b (cyt b) and control region (CR) nucleotide sequences were used to study the molecular phylogeny of the genus Syrmaticus. We found that the substitution rates among the three codon positions of cyt b were heterogeneous and the transition-transversion ratio was highly biased. As to CR sequences of the genus, most variable sites were in the peripheral domains. All molecular phylogenetic trees based on the two genes showed that: 1) the Syrmaticus was monophyletic and included five species with the following cladistic relationship: (S. reevesii, (S. soemmerringii, (S. mikado, (S. humiae and S. ellioti)))). Using the TN genetic distance of cyt b, we inferred the divergence time of the five species according to putative molecular clock and found that values were largely in agreement with the geological scenarios. The origin and speciation processes of the studied group were inferred by combining molecular and biogeographical evidences.

Females and males often have different roles when attending young. The factors responsible for shifts in the balance of effort when both sexes provision their young are not clear. This study asked if sex-specific behaviour and provisioning rules in barn swallows (Hirundo rustica) were dependent on individual body-state or affected by the state of their provisioning partner. To assess this male and female barn swallows underwent overnight warming manipulations whilst provisioning 10–14 day old nestlings, a time when energetic demands are maximal. The overnight warming treatment reduced thermoregulatory costs and provided birds with extra energy reserves at dawn. Only one member of a pair was manipulated in this way, whilst their partners were left un-manipulated to assess their response to their partner's elevated body-state. The energetic and behavioural responses to these manipulations were followed over the subsequent 24-h. I found that warmed male and female barn swallows increased their energy expenditure and nest visitation rates to the same extent after manipulation, implying a trade-off in resource allocation, which was biased towards reproductive effort. There was no effect of gender. Males paired with manipulated females showed no energetic or behavioural adjustments, however, females paired with manipulated males tended to increase both energy expenditure and nest visitation. This study provides evidence that energy reserves constrain behaviour, and that male and female swallows normally follow the same state-dependent rules when provisioning young.

The relationship between externally measured condition (mass × length⁻³) and the mass of internal major organs in the caecilian Gegeneophis ramaswamii is investigated, based on a collection of 67 specimens from three southern Indian localities in the early and mid-monsoon. Condition in juveniles (< 90 mm total length) is higher than in subadults (90–170 mm) and adults (> 170 mm). The relationship between condition and total length is consistent in subadults, but variable in adults, and these differences indicate that the delimitation of these ontogenetic stages has some biological meaning. Adult females have fat bodies which fluctuate in mass, but not in relation to their body size. On average, adult females have heavier fat bodies and lighter gut contents than adult males, but there are no significant differences between subadult males and females. Gravid females are predicted to have a notably greater condition. There is no consistent relationship between condition and any major internal organ, but there is some significant variation among samples grouped by sampling time and locality. More sampling throughout the year is required to clarify the complex relationships between condition and internal organs, and before externally measured condition from ecological studies of living animals can be readily interpreted. However, its utility in helping to differentiate between ontogenic classes may be of immediate use.

Vitellogenin (VTG) produced in male fish has been used for a biomarker to study endocrine disrupters. However, the characteristics of VTG produced in male fish have not been studied well. In this study, we investigated the localization of VTG in the liver and the testis of male medaka (Oryzias latipes) treated with 17β-estradiol (E2) and p-nonylphenol (NP). The male fish were exposed to 1 μg/L E2 and 500 μg/L NP for 1–12 days. Control groups were kept in water including only vehicle. The frozen sections of the liver and the testis were stained with immunohistochemical methods using an antiserum against medaka VTG as the first antibody. In the E2 and NP treated liver, the hepatocytes showed immunoreactivity. In particular, the cytoplasm close to the cell membrane surrounding the sinusoids was strongly immunopositive. In the testis of both treatments, the interstitial tissues and the cells (spermatocytes) in the seminiferous tubules were immunopositive. The concentration of VTG became gradually higher in both tissues with longer treatments. These results suggest that germ cells in the testis treated with E2 and NP are able to incorporate and accumulate VTG.

External genitalia are the reproductive organs necessary for efficient copulation and internal fertilization in various mammalian species. Their morphogeneses display significant morphological and developmental differences among species. The house musk shrew, Suncus murinus (hereafter described as suncus) is a species of the order Insectivora, which has been considered as primitive and one of the earliest eutheria phylogenetically. Comparative anatomical analyses of phylogenetically different mammals will contribute to the better understanding of morphological diversity of external genitalia. This study performed various anatomical and histological analyses concerning the organization of the external genitalia of male suncus. It was shown that the external genitalia of suncus possessed a muscular structure, which we proposed as musculus ischiocavernosus dorsalis of suncus. The musculus ischiocavernosus dorsalis is originated from the inner surface of the tuber ischiadicum and was allocated adjacent to the corpus cavernosum penis. In addition, a pair of α-smooth muscle actin positive muscles was located bilaterally to the urethra. This unique morphology of the external genitalia of suncus males may provide a unique model system to investigate genital morphogenesis.

Anterograde and retrograde transport of horseradish peroxidase was used to examine the afferent and efferent projections of the glossopharyngeal and vagal nerves in the lamprey, Lampetra japonica. Except for the ganglion cells and motoneurons, the distribution patterns of HRP-positive elements differed little between the two nerves. Afferent fibers mainly terminated in the ipsilateral cerebellar area, medial octavolateralis nucleus, and between the ventral octavolateralis nucleus and descending tract and nucleus of the trigeminal nerve (dV). In the cerebellar area, most of the labeled fibers were located in the molecular zone, but some penetrated into the granular zone. In the rostral part of the medial octavolateralis nucleus, labeled fibers coursed from the middle to the lateral area, and in the caudal part, they were localized in the dorsal area of the nucleus. In the area between the dV and ventral octavolateralis nucleus, labeled fibers coursed near the dorsal margin of the rostral part of the dV, and in the caudal part, they shifted dorsally. Ganglion cells and motoneurons of each nerve were also labeled.

Two species of cyclopoid copepods, Ochridacyclops kenyaensis sp. nov. and O. nepalensis sp. nov. are described as the first records of this genus from Kenya and Nepal, respectively. Ochridacyclops kenyaensis can easily be distinguished from its congeners by having a rounded and blunt distal end of the outer terminal seta (IV) on the caudal rami, and by the inner terminal spine being about equal in length to the outer terminal spine on the endopod of leg 4. Ochridacyclops nepalensis can easily be distinguished from other members of the genus by having two spines on exopodal segment 3 of leg 1, and by the proportions of the caudal rami, which are 3.4 times longer than wide.

A molecular phylogenetic survey was conducted using mtDNA sequences of 12S and 16S rRNA, and cyt-b genes to examine taxonomic relationships among populations of the Pan-Oriental microhylid, Microhyla ornata, from India, Bangladesh, Thailand, Laos, China, Taiwan, and the Ryukyu Archipelago of Japan. Two discrete clades are recognized within this species, one consisting of populations from India and Bangladesh, and the other encompassing the remaining populations. In the latter clade, populations from the Ryukyu Archipelago are clearly split from the rest (populations from Taiwan and the continent) with considerable degrees of genetic differentiations. Each of the three lineages is judged to represent a good species, and the name Microhyla ornata is restricted to the South Asian populations. For the populations from Taiwan and a wide region from China to Southeast Asia, the name Microhyla fissipes should be applied, whereas the Ryukyu populations are most appropriately referred to as Microhyla okinavensis, although further substantial genetic differentiations are recognized among some island group populations within this last species.