The development of muscles and bones in fish is laterally asymmetric (laterality). A “lefty” individual has a “C”-shaped body, with its left-side muscles more developed and the left side of its head facing forward. The body of a “righty” is the mirror-image. This laterality causes asymmetric interactions between individuals of different fish species, in that a righty or lefty fish consumes more lefty or righty fish, respectively. To investigate the coupling mechanisms between body asymmetry and predatory behavior, we conducted angling experiments with largemouth bass (Micropterus salmoides). We used the position of the fishhook set in the mouth to indicate the movement direction of the fish when it took the bait. Righty fish had more hooks set on the right side, whereas lefty fish had more on the left side, indicating that righty fish moved more to the left, and lefty fish moved more to the right, in successful catches. The relationship between the hooked position and movement direction was confirmed by video-image analysis of the angling.

After a loss against an opponent, the aggressiveness of a male cricket is significantly reduced for up to 30 minutes. This depression of aggressiveness is an important factor in the establishment and maintenance of dominance between individuals. In the present study, we investigated the functional roles of nitric oxide (NO) signaling in the depression of aggressiveness in subordinate male crickets. Pairs of male crickets, pre-injected with various NO-related reagents, were allowed to establish dominant/subordinate relationships in dyadic encounters. Opponents were separated for 15 minutes and then paired again. In second encounters, subordinate crickets pre-injected with PTIO (NO scavenger) showed agonistic behavior towards former dominant opponents. A similar effect was observed in crickets pre-injected with L-NAME (NO synthase inhibitor) or ODQ (soluble guanylate cyclase inhibitor). The effects of the latter two drugs were canceled by co-injection of NOR3 (NO donor) with L-NAME or by co-injection of 8-Br-cGMP (cGMP-analog) with ODQ. Injection of NOR3 alone prolonged the inhibition of agonistic behavior in subordinate crickets from 30 minutes to 3 hours. Our results suggest that the change in agonistic behavior observed in subordinate male crickets is closely linked to NO-mediated cGMP signaling.

Napaeus barquini Alonso and Ibáñez, 2006, from La Gomera, Canary Islands, lives most commonly on open rock faces covered with crustose lichens. In living specimens, the surface of the shell is covered with a lichen layer that is arranged in the form of protuberances, thereby considerably altering the appearance of the shell. Some of these protuberances may even extend beyond the tip of the shell. The way that these lichens are positioned on the shell and the manner in which they adhere were investigated. The snail grazes lichen material from the substrate and applies it to the surface of its shell in a standardized pattern of movements. The snail uses its mouth to place the moist material onto the shell and to form it into protuberances that adhere as they dry out. To do this, Napaeus barquini extends its body far beyond the shell margin so that it can reach the entire outer surface of the shell and cover it with protuberances, presumably as camouflage.

Sexual differentiation in the amniote brain is believed to be regulated by gonadal sex steroid hormones. Recently, however, the possibility of brain-autonomous sexual differentiation in avian and reptilian species has been reported. We conducted here an expressional analysis of genes related to sex steroid hormones in the chick-embryo brain before gonadal sexual differentiation. Female-specific P450 aromatase expression in the gonad was observed at day 6.5 of incubation, as previously reported, whereas the mRNAs of cholesterol side-chain cleavage enzyme, androgen receptor, and estrogen receptors α and β were clearly expressed in all brain samples of both male and female embryos from day 4.5 of incubation. P450 aromatase was expressed in some brain samples before day 5.5 of incubation and in all brain samples after day 6 of incubation. The mRNA of Ad4BP/SF-1, a transcription factor that regulates steroidogenic enzymes, showed higher expression levels in the male brain than in the female brain at day 5.5 of incubation. This gene was expressed in the ventromedial hypothalamic nucleus, a region important for reproductive behavior. Embryonic Ad4BP/SF-1 expression is reported to play an important role in the formation of this region. These results therefore suggest the involvement of a sex steroid hormone signaling system in brain-autonomous sexual differentiation.

Pristionchus pacificus has been developed as a nematode satellite organism in evolutionary developmental biology. Detailed studies of vulva development revealed multiple differences in genetic and molecular control in P. pacificus compared to the model organism Caenorhabditis elegans. To place evolutionary developmental biology in a comprehensive evolutionary context, such studies have to be complemented with ecology. In recent field studies in western Europe and eastern North America we found 11 Pristionchus species that are closely associated with scarab beetles and the Colorado potato beetle. However, P. pacificus was not commonly found in association with scarab beetles in these studies. Here, we describe the results of a similar survey of scarab beetles in Japan. Pristionchus pacificus was the most common Pristionchus species on scarab beetles in Japan, with 40 out of 43 (93%) isolates. The other Pristionchus isolates represent three novel species, which we refer to as Pristionchus sp. 11, Pristionchus sp. 14, and Pristionchus sp. 15. Thirty-seven of the established P. pacificus strains were found on the oriental beetle Exomala orientalis. Laboratory studies with the sex pheromone (Z)-7-tetradecen-2-one of the oriental beetle revealed that P. pacificus shows strong olfactory attraction to the beetle's sex pheromone, which provides a potential mechanism for the recognition and interaction of P. pacificus and E. orientalis. Together, this study identifies P. pacificus as the most common Pristionchus nematode in field studies in Japan, identifies E. orientalis as an important host species, and provides the basis for the ecology of P. pacificus.

The viability of free-living glochidia of the freshwater pearl mussel (Margaritifera laevis) was studied in the laboratory at water temperatures of 10°C, 15°C and 20°C. To obtain glochidia, gravid female mussels were collected from the Chitose River, inhabited by adult and juvenile mussels, and from the Abira River, where only adult mussels were found. Daily survival rates of glochidia from each population at various water temperatures were significantly different, and survival time was longest at the lowest temperature in each population. Maintenance of some field mussel populations might become difficult at higher water temperatures due to the short survival time of glochidia and expected low density of host fish. Daily survival rates of glochidia were compared between the Abira population at 15°C and the Chitose population at 20°C, since these temperatures were close to the mean water temperature during the period of glochidial release in the respective rivers. Daily mean survival rates were significantly different between the Abira population at 15°C and the Chitose population at 20°C. Mean glochidial survival rate for the Chitose population changed from 85.3% to 66.2% from 9 to13 h, whereas that for the Abira population dropped suddenly from 80.4% to 34.2% from 10 to 14 h after the initiation of experiment. Absence of juveniles in the Abira River might have been caused by the low glochidial viability. Survival times of free-living glochidia in Margaritiferidae tend to be shorter than in other families in Unionoida. A trade-off is suggested between high fertility and low glochidial survival rate in Margaritiferidae.

In order to examine the effects of estrogen, androgen, and phytoestrogen on maternal behavior induced by exposure to fresh pups in ovariectomized nulliparous rats, 1 mg estradiol benzoate (EB), 1 mg testosterone propionate (TP), 1 mg coumestrol (CM), or oil (female control) was injected subcutaneously daily for 10 days. To elucidate the sex difference, 1 mg EB or oil (male control) was injected in orchidectomized rats by the same method as that used in nulliparous rats. Exposure to fresh pups was started 6 days after the first injection. Behavioral tests were carried out daily for 5 days from the first exposure to the last on the 10th day. In the behavioral test, the onset of retrieving and licking behaviors was recorded. In female control rats, the median onset day of retrieving behavior was day 5. Onset in the EB female group was day 1.5, which was shorter than that in the female control (P<0.05). TP female and CM female rats started to show retrieving at day 5 and day 4.5, respectively, comparable to the female controls. In males, the median day of retrieving onset in the control and EB groups was over day 5 and day 4.5, respectively. No statistical difference was seen between the female and male controls. In contrast, there was a difference between the EB-treated female and EB male groups. Licking activity was less frequent than seen in the retrieving behavior among all groups, but there was no statistical difference among the groups. These results suggest that estrogen facilitates retrieving behavior in female, but not in male rats. TP and CM have no effect on retrieving behavior in female rats.

We examined the histological structure of the tongue of Laudakia stellio, the starred agama lizard (Agamidae, Squamata), under light microscopy. We also investigated the muscle and papilla volume ratios, with volumes of each aspect of interest estimated according to the Cavalieri method. The macroscopically short, thick and muscle-rich front tip of the tongue of L. stellio does not show any bifurcation, and under light microscopy, the oval-shaped papilla-free front tip was seen to be covered by keratinized stratified epithelium. The dorsal and ventral parts were different, with the former partially covered by keratinized stratified epithelium and rich in secretory glands and secretory cells. The ventral part, which contained keratinized stratified cells, had a flat surface with no papillae. The dorsal surface of the anterior and posterior parts contained fungiform papillae, with the apical parts of these papillae containing minimal keratin; the interpapillar space was covered by keratin-free squamous stratified epithelium. The middle section of the tongue contained cylindrical-type papillae, with serous and mucous secretory glands and ducts at their base. Finally, the frontal and middle parts of the ventral and dorsal surfaces did not contain any taste buds, although there were some in the hind part of the dorsal surface. As morphometric estimates of volumes of the muscles and papillae, the mean volume ratios (relative to total tongue volume)±standard deviation were 0.66±0.03 and 0.33±0.03, with mean coefficients of error of 0.02 and 0.03, respectively.

The adult female of the freshwater ostracod Cyprinotus uenoi Brehm, 1936 (Podocopida: Cypridoidea) has a pair of long, sac-like ovaries separately lying in the posterior part of the left and the right carapace valves. Oogonia and very early previtellogenic oocytes are located in the terminal germarium of each ovary. In the germarium, the oogonia occur in the most terminal region, and the very early previtellogenic oocytes are located in the remainder, arranged in order of size, the larger ones nearer the ovarian lumen. Most of the growing oocytes, previtellogenic and vitellogenic, are found in the ovarian lumen, the larger ones farther from the germarium. In the germarium, a cytoplasmic bridge connects a pair of adjoining germ cells, resulting from an incomplete cytokinesis of oogonial division. Among the previtellogenic and early vitellogenic oocytes in the ovarian lumen, “nurse cells” are found as small, spherical cells in mostly the same number as these oocytes. A cytoplasmic bridge connects each “nurse cell” to an adjoining oocyte. Based on the manner of connection and some morphological features, we consider that each “nurse cell” originates from one of each pair of adjoining germ cells connected by a cytoplasmic bridge in the germarium, as in the true nurse cells of several branchiopod crustaceans and insects with meroistic ovarioles.

The immigrans species group in the Drosophilinae is one of the representative species groups of Drosophila in East Asia. Although this group constitutes a significant part of the drosophilid fauna in the Old World, only a few species have been analyzed in previous molecular phylogenetic studies. To study the phylogeny of the immigrans group, we analyzed the nucleotide sequences of two nuclear genes, alcohol dehydrogenase (Adh) and glycerol-3-phosphate dehydrogenase (Gpdh), for 36 drosophilid species, including 12 species of the immigrans group. In the resultant phylogenetic trees, 10 species of the immigrans group (D. immigrans, D. formosana, D. ruberrima, D. albomicans, D. nasuta, D. neonasuta, D. pallidifrons, D. hypocausta, D. neohypocausta, D. siamana) consistently formed a clade (the immigrans group proper), although the phylogeny within this clade did not exactly correspond to the classification of species subgroups. However, D. annulipes and D. quadrilineata, both of which belong to the quadrilineata subgroup of the immigrans group, were not included in the immigrans group proper. Furthermore, we obtained the unexpected result that D. annulipes was included in a clade comprising Scaptomyza and Hawaiian Drosophila, together with D. maculinotata of the funebris group, although the phylogenetic relationships within this clade remain uncertain and need to be substantiated with further studies. Thus, according to the present study, the immigrans group is polyphyletic.

The kissing loach, an endangered species surviving only in a few Japanese rivers, spawns in the rice-field areas after migration from rivers in early June. To characterize the environmental conditions required for spawning of the kissing loach, spawning was assessed for two years both by direct observation of spawning behavior and by the appearance of eggs, larvae, and juveniles from June to October. All spawning of the kissing loach was limited to within a couple of days after the formation of temporary waters by remarkable rises in water level. Water temperature and daily rainfall fluctuated during the investigation periods, and no clear relationships with spawning were detected. Furthermore, all spawning was observed only in temporary waters with terrestrial grasses. Thus, spawning of the kissing loach is rigidly limited spatiotemporally to after the formation of temporary waters over terrestrial vegetation. Appropriate management of temporary waters will be crucial for the continued existence of this species.

Polistes formosanus Sonan, 1927 is closely related to P. japonicus de Saussure, 1858, and has been treated variously as a good species or subspecies or synonym of P. japonicus. We designate the lectotype of P. formosanus. Detailed examination of morphological characters of specimens from continental Asia, Taiwan, the Nansei Islands and main islands of Japan showed that P. formosanus is a good species different from P. japonicus. Molecular phylogenetic analyses using mitochondrial genes also supported this conclusion. Polistes formosanus is distributed in northern and central Taiwan and in the Nansei Islands and extends northward to the Amami Islands, while P. japonicus occurs in continental Asia, central Taiwan, Korean Peninsula, Honshu to Kyushu of Japan and the Osumi Islands (Yakushima and Tanega-shima Island) of the Nansei Islands. The speciation and biogeography of P. formosanus are briefly discussed.

A small Japanese salamander, Hynobius naevius, long considered a single species, has recently proven to include two groups (Group A=large type and Group B=small type) that are split at the species level. We compared the type series of H. naevius with specimens of the two groups to clarify which of them corresponds to true H. naevius, and to estimate the type locality of this species, which was not given in detail in its original description. Results of various morphological analyses altogether indicated that the type series belongs to Group A and that the population sample from Mt. Taradake, located on northwestern Kyushu, is most similar to the type series. Therefore, the type locality of the species is estimated to be in northwestern Kyushu. These results also indicate that Group B obviously represents a cryptic species whose scientific name remains to be determined.