Steroidogenic factor-1 (SF-1) and liver receptor homolog-1 (LRH-1) belong to the nuclear receptor superfamily and are categorized as orphan receptors. In addition to other nuclear receptors, these play roles in various physiological phenomena by regulating the transcription of target genes. Both factors share very similar structures and exhibit common functions. Of these, the roles of SF-1 and LRH-1 in steroidogenesis are the most important, especially that of SF-1, which was originally discovered and named to reflect such roles. SF-1 and LRH-1 are essential for steroid hormone production in gonads and adrenal glands through the regulation of various steroidogenesis-related genes. As SF-1 is also necessary for the development of gonads and adrenal glands, it is also considered a master regulator of steroidogenesis. Recent studies have clearly demonstrated that LRH-1 also represents another master regulator of steroidogenesis, which similarly to SF-1, can induce differentiation of non-steroidogenic stem cells into steroidogenic cells. Here, we review the functions of both factors in these steroidogenesis-related phenomena.

Parental behaviors that vary by sex and breeding stage facilitate the survival of offspring in birds. Females invest in reproducing according to the level of direct and/or indirect benefits provided by males. Males face trade-offs from defending territories or nests, providing for the young, and seeking additional mating opportunities. We examined whether post-mating sexual behaviors such as courtship display and nest-building were associated with reproductive investments made by males and females in the current study. The oriental stork (Ciconia boyciana) is known as a solitary breeder that nests in tall trees and provides biparental care with long post-hatching development. We filmed parental behaviors in seven stork pairs in captivity for 655 hours (245 hours during nest-building, 218 hours during incubation, 328 hours during nestling, and 192 hours during the fledgling period). We found that paired mating behaviors such as synchronous allopreening and bill-clattering were highly skewed to the pre-incubation period. Males participated in nest-building more than females although both sexes shared similar parental care during the incubation and nestling period. Male nest-building was negatively correlated with male nest attentiveness only during the nestling period. Our results suggest that male oriental storks with higher nest-building effort might spend more time taking precautions against conspecific intruders or nest predators near the nests with chicks while the females were attending the nests in the form of biparental care.

We examined the effects of predator-prey distance (PPD) and trajectory of the predator on the body patterns that the pharaoh cuttlefish, Sepia pharaonis, shows in response to a predator. A model predator moving in three different trajectories was presented to the cuttlefish: T1, approached the cuttlefish but bypassed above; T2, approached directly toward the cuttlefish; T3, bypassed the cuttlefish both vertically and horizontally. We divided the body patterns that the cuttlefish expressed into seven categories, i.e., “uniform light”, “disruptive”, “center circle”, “dark square”, “vertical stripe”, “all dark” and “eyespots”. In T1, the number of individuals that showed “dark square” increased as the model approached the cuttlefish, whereas the number of individuals that showed “disruptive” decreased. In T2, the number of individuals that showed “all dark” and “eyespots” increased as the model approached the cuttlefish. In T3, the number of individuals that showed “dark square” and “vertical stripe” increased as the model approached the cuttlefish, and it tended to decrease as the model receded from the cuttlefish. These results demonstrate that S. pharaonis changes its body patterns according to PPD and the trajectory of the predator, which would affect predation risk and/or predator perception.

Coelomocytes are the first line of immune defense in marine animals. Their distributions are greatly variable even in the close animal species. In this study, we used lectin staining to aid in the classification and purification of these cells for further investigation of SOD distribution among coelomocytes of H. scraba. We classified coelomocytes into four types: type 1, lymphocytes; type 2, phagocytes; type 3, spherulocytes; and type 4, giant cells. Among four lectins used, Con A appeared to give a broad reactivity against most coelomocytes, except for giant cells. In addition, phagocytes usually engaged the highest fluorescent intensity with most lectins, with the exception of PNA, for which spherulocytes possessed the highest fluorescent intensity. Using FACS for fraction collection, it was found that F1 fraction contained the purest phagocyte population (> 95%), which was highly reactive with anti- superoxide dismutase (SOD) as revealed by immunoblotting and immunofluorescence staining, although some minor staining was also detected in spherulocytes. Our results thus provide a fundamental platform for comparing alterations that may happen to the population and SOD contents of coelomocytes when the sea cucumber is subjected to environmental changes that would activate their immune responses.

Whip scorpions (Thelyphonida), comprising an order in the class Arachnida, are distributed from tropical to temperate zones. Two species occur exclusively in Japan and Taiwan, but the border of their distributional ranges is ambiguous in the Central Ryukyus (Japan). We collected new specimens from the Central Ryukyus and revealed that the border of distribution of the two species lies between the Central and Southern Ryukyus, i.e., the Kerama Gap. Moreover, the estimated divergence time (15.8 Mya) of the two species, based on the mitochondrial COI gene, was older than the recently estimated time (1.55 Mya) of formation of the Kerama Gap. These results highlight the risks of a priori assumption solely on the basis of geological data for applying it as a calibration point to some terrestrial animals in this region. Typopeltis stimpsonii was genetically divided into four lineages, two of which turned out to be endemic to the Okinawa Islands. All specimens from the main island of Japan and Shikoku were in one lineage, which was also found in the Amami Islands and Hachijojima Island. This suggests that these specimens may have been dispersed by human activity. Typopeltis crucifer included five genetic lineages. Species collected from Ishigakijima and Iriomotejima Islands were genetically diversified not between the borders of these islands but within Ishigakijima Island. This study also suggests that phylogenetic diversity of the species in the Southern Ryukyus have increased through two times of invasions from Taiwan.

Evolutionary ecologists often expect that natural and sexual selection result in systematic co-occurrence patterns of sex-biased mortality and sexual size dimorphism (SSD) within animal species. However, whether such patterns actually occur in wild animals is poorly examined. The following expectation, the larger sex suffers higher mortality, was primarily tested here for apparently native sea-run masu salmon (Oncorhynchus masou) in three populations in Hokkaido, Japan. Field surveys on sex ratios, body sizes, and ages of smolts and returning adults revealed that two of the three populations exhibited an expected pattern, a female-biased marine mortality and SSD, but one population demonstrated an unexpected co-occurrence of male-biased marine mortality and female-biased SSD. These female-biased SSDs were attributed to faster marine growth of females because of no sex difference in smolt body size. It has been previously suggested that breeding selection favoring large size generally act more strongly in females than in males in Japanese anadromous masu, as there is a weak sexual selection on adult males but universally intensive natural selection on adult females. Thus, this hypothesis explains female-biased SSDs well in all study populations. Interpopulation variation in sex-biased mortality found here might result from differences in marine predation and/or fishing pressures, given that selection driving female-biased SSD makes females forage more aggressively than males during the marine phase. Taken together, these results raise the possibility that evolutionary forces have shaped adaptive sex-specific foraging strategies under relationships between growth and mortality, resulting in co-occurrence patterns of sex-biased mortality and SSD within animal species.

Diverse life histories have been documented in terrestrial pulmonates, which inhabit different regions in climate. Life history traits are often phenotypically plastic and vary depending on the environment. Thus, surveys using designs that control for the confounding effects of environment are needed to evaluate the evolutionary differences between populations of closely related species in the wild. We examined the life histories of sibling species of terrestrial pulmonate within two regions of similar climates. Bradybaena pellucida (BP) is endemic to Japanese islands, and has recently been expanding its distribution northeastward, whereas B. similaris (BS) has been introduced by humans into temperate and tropical regions worldwide. We found that these species exhibit discrete differences in population dynamics and life cycle, despite their close relatedness. The annual life cycle of BP is synchronized among individuals in a population. Thus, BP is univoltine with discontinuous generation. In contrast, BS individuals do not synchronize their growth or reproduction, and thus exhibit overlapping generations. Our results indicate that synchronized and non-synchronized population dynamics diverge relatively rapidly in semelparous pulmonates. This type of difference has not been documented in pulmonate life history, and may have been overlooked because only a few studies have explicitly compared life cycles of closely related species within the same climate. Our results provide a basis for further studies of life history evolution in pulmonates.

Irrigation ditches are the major habitat of lotic unionid mussels in Japan. To conserve and rebuild irrigation ditches facilitating mussel conservation, suitable physical environments must be clarified. The effect on mussels of paddy fields connected to ditches also needs to be determined. In this study, physical environmental factors that affect the density of unionid mussels were studied in irrigation ditches in Hikone City, Shiga Prefecture, Japan, to examine whether mussel densities were higher around paddy fields. Generalized linear models were used to analyze physical and paddy field environmental variables affecting mussel density. Our results show that sediment type, sediment softness, water depth, and flow velocity of irrigation ditches affect the density of unionid mussels; the effects of each environment factor and their relative importance differed by species. Specifically, the density of Nodularia douglasiae biwae was higher in ditches with sand-gravel sediment, soft sediment, and not adjoining paddy fields. The density of Pronodularia japanensis was higher in ditches with sand-gravel sediment and not adjoining paddy fields. The density of Lanceolaria grayana was higher in ditches with high flow velocity, not adjoining paddy fields, close to Lake Biwa. The density of Sinanodonta japonica was higher in ditches with mud sediment, shallow depth, high flow velocity, and not adjoining paddy fields. The densities of all four species were lower in irrigation ditches that were closely connected to paddy fields, suggesting that paddy drainage water negatively affects the survival of the mussels.

In the present study we histochemically and lectinhistochemically characterized the growing oocytes of the pink cuskeel (Genypterus blacodes). We used histochemical methods for the localization and characterization of glycoconjugates (GCs) and lectin histochemical techniques for the identification of specific sugar residues. We analyzed presence and distribution of GCs in the different structures of the growing follicles (cortical alveoli, globules, yolk granules and zona radiata). During the initial stage of vitellogenesis, the oocytes presented small yolk granules composed of GCs that gradually increased during exogenous vitellogenesis. These GCs contained moderate quantities of α-D-mannose, D-glucose, N-acetylglucosamine and N-acetyl-neuraminic acid. The cortical alveoli contained both neutral and carboxylated GCs, and lectin techniques detected N-acetylgalactosamine, galactose and L-fucose. The zona radiata showed a strong positive reaction to PAS and it reacted weakly with more specific techniques, such as KOH/PA*S and PA/Bh/KOH/PAS. This structure showed GCs with oxidizable vicinal diols, O-acyl sugars and sialic acid residues with different substitution types and presented N-acetylgalactosamine and L-fucose specific residues. The oocytes follicular envelope evidenced neutral and acidic non-sulfated GCs and high concentrations of α-D-mannose, D-glucose, galactose and N-acetylgalactosamine. The intergranular cytoplasmic GCs were mainly rich in α-D-mannose, D-glucose, N-acetylgalactosamine, N-acetylglucosamine and N-acetyl-neuraminic acid. These results enhance the comprehension of the structure and functionality of the pink cuskeel ovarian follicles, and provide a useful tool for the study of this tissue in other teleost species.

Integumentary and alimentary tissues were ultrastructurally examined in two pycnophyid kinorhynchs, Pycnophyes oshoroensis and Kinorhynchus yushini, to elucidate some aspects of their ecology. The body is entirely enveloped by an epicuticle layer with no gaps between cuticle plates and joints. The cuticular layer has a structure dense enough to prevent invasion by foreign organisms. The cuticular surface is overlaid by a mucus layer that may form a hydrophilic surface. The alimentary contents were heterogeneous, probably including some cellular components, such as chloroplast-like structures. Kinorhynchs likely break down food particles in the pharyngeal bulb by pressing it between the cuticulated epithelia. The pharyngeal crown was located in front of the pharyngeal bulb and had a thick wall with a striated sub-structure. Contraction of the pharyngeal bulb probably increases the internal pressure of the pharyngeal crown; this may be one reason for the thick wall of the pharyngeal crown. Nutrients appear to be taken up by midgut epithelial cells through both absorption via microvilli and endocytosis. Additionally, sperm tails in the testis of P. oshoroensis have unusual axonemes; i.e., an 18 9 2 pattern.

Bioconvection is a form of collective motion that occurs spontaneously in the suspension of swimming microorganisms. In a previous study, we quantitatively described the “pattern transition,” a phase transition phenomenon that so far has exclusively been observed in bioconvection of the unicellular green alga Chlamydomonas. We suggested that the transition could be induced by changes in the balance between the gravitational and shear-induced torques, both of which act to determine the orientation of the organism in the shear flow. As both of the torques should be affected by the geometry of the Chlamydomonas cell, alteration in the flagellar waveform might change the extent of torque generation by altering overall geometry of the cell. Based on this working hypothesis, we examined bioconvection behavior of two flagellar mutants of Chlamydomonas reinhardtii, ida1 and oda2, making reference to the wild type. Flagella of ida1 beat with an abnormal waveform, while flagella of oda2 show a normal waveform but lower beat frequency. As a result, both mutants had swimming speed of less than 50% of the wild type. ida1 formed bioconvection patterns with smaller spacing than those of wild type and oda2. Two-axis view revealed the periodic movement of the settling blobs of ida1, while oda2 showed qualitatively similar behavior to that of wild type. Unexpectedly, ida1 showed stronger negative gravitaxis than did wild type, while oda2 showed relatively weak gravitaxis. These findings suggest that flagellar waveform, not swimming speed or beat frequency, strongly affect bioconvection behavior in C. reinhardtii.

The marine interstitial annelid Trilobodrilus itoi sp. nov., the sixth member of the genus, is described on the basis of specimens collected intertidally at Ishikari Beach, Hokkaido, Japan; this is the second species in the genus described from the Pacific Rim. In addition, T. nipponicus Uchida and Okuda, 1943 is re-described based on fresh topotypic material from Akkeshi, Hokkaido, Japan. From both species, we determined sequences of the nuclear 18S and 28S rRNA genes, and the mitochondrial cytochrome c oxidase subunit I (COI) gene. Molecular phylogenetic trees based on concatenated sequences of the three genes showed that T. itoi and T. nipponicus form a clade, which was the sister group to a clade containing the two European congeners T. axi Westheide, 1967 and T. heideri Remane, 1925. The Kimura two-parameter distance for COI was 22.5–22.7% between T. itoi and T. nipponicus, comparable with interspecific values in other polychaete genera. We assessed the taxonomic utility of epidermal inclusions and found that the known six species can be classified into three groups.