Recent experimental studies involving the manipulation of sexual traits have demonstrated that sexual trait expression feeds back to testosterone levels, perhaps via social interactions, reinforcing the linkage between sexual trait expression and testosterone levels during the mating period. However, information on this reinforcement under the natural variation of sexual traits remains limited. Using Japanese barn swallows, Hirundo rustica gutturalis, in which extra-pair paternity is quite rare (< 3%), we studied the relationship between plasma testosterone level and a male sexual trait, throat patch size, during the mating and incubation periods. Given the importance of social interaction, we predicted that this relationship should be intense during the mating period, but not the incubation period, due to reduced social interaction during the latter. We found low plasma testosterone levels during the incubation period compared with those in the mating period, and plasma testosterone levels were significantly positively related to throat patch area during the mating period, but not the incubation period. Similar relationships were found in another sexual trait, the size of white tail spots. During the incubation period, body condition, instead of male sexual trait expression, was negatively related to plasma testosterone level, indicating that an intrinsic link, rather than reinforcement, is important during this period. These relationships are consistent with the hypothesis that social interaction reinforces the relationship between sexual traits and plasma testosterone levels. The current study provides evidence for a highly variable relationship between testosterone and ornamentation across breeding periods in the natural variation of sexual traits.

Laterality has been studied in several vertebrates, mainly in terms of brain lateralization and behavioral laterality, but morphological asymmetry has not been extensively investigated. Asymmetry in fishes was first described in scale-eating cichlids from Lake Tanganyika, in the form of bilateral dimorphism in which some individuals, when opening their mouths, twist them to the right and others to the left. This asymmetry has a genetic basis, and is correlated with lateralized attack behaviors. This has subsequently been found in fishes from numerous taxa with various feeding habits. The generality of such morphological laterality should thus be investigated in as wide a range of fishes as possible. Using specific indicators of lateral differences in mandibles and head inclination, we find that representative species from all 60 orders of extant gnathostome fishes (both bony and cartilaginous) possess morphological laterality. Furthermore, we identify the same laterality in agnathans (hagfish and lamprey), suggesting that this trait appeared early in fish evolution and has been maintained across fish lineages. However, a comparison of asymmetry among groups of bony fishes reveals, unexpectedly, that phylogenetically more recent-groups possess less asymmetry in body structures. The universality of laterality in fishes indicates a monophyletic origin, and may have been present in the ancestors of vertebrates. Ecological factors, predator—prey interactions in particular, may be key drivers in the evolution and maintenance of dimorphism, and may also be responsible for the cryptic trend of asymmetry in derived groups. Because lungfish and coelacanths share this trait, it is likely that tetrapods also inherited it. We believe that study of this morphological laterality will provide insights into the behavioral and sensory lateralization of vertebrates.

Predator—prey interaction is one of the most important and pervasive pressures in the ecology and evolution of prey species. However, accurate description of the food web is sometimes extremely difficult as there are many predator–prey interactions in the wild are obscure. Recent studies have reported that two closely related land snails, Karaftohelix editha and K. gainesi, on Hokkaido Island, Japan, were diversified due to predation, probably by carabid beetles. However, it is unclear 1) whether native rodents prey upon land snails on Hokkaido Island, and 2) how frequently land snails are preyed upon by rodents in this region, although it has been reported that several species of rodents are predators of land snails in many regions. Thus, we investigated these issues in this study by captive feeding trials and field observations. No rodent species other than the Siberian chipmunk, Tamias sibiricus, were found to prey upon land snails around the research site on Hokkaido Island. In addition, the population density of T. sibiricus was lower than those of other rodent species, and it has been reported that T. sibiricus is omnivorous and preys upon snails considerably less than on other food sources. Overall, these findings suggest that T. sibiricus is not an important predator of Karaftohelix land snails in Hokkaido.

Although scute pattern abnormalities in sea turtle species are considered to be strongly correlated with survival rate, there is little information available regarding these abnormalities and the primary cause for their development is unclear. For the conservation of sea turtle species, accumulating basic knowledge of scute pattern abnormalities is a fundamental step towards a better understanding of the causes of these abnormalities. In the present study, we counted vertebral and costal scutes from adults hunted for food (male and female) (n = 899), nesting females (n = 155), and hatchlings (n = 44,537) of the green sea turtle (Chelonia mydas) from the Ogasawara Archipelago, Japan. We found that the frequency of turtles with non-modal scute patterns was significantly greater in adult females than that in adult males (P = 0.02). Since females are produced by warmer incubation temperatures, and the period of sex determination coincides with the period of scute pattern determination, high incubation temperatures may be responsible for the induction of scute pattern abnormalities. Moreover, females with non-modal scute patterns produced a higher frequency of hatchlings with non-modal scute patterns than females with modal scute patterns (P < 0.01), indicating that scute abnormality may be heritable. For conservation of this species, our results suggest that decrease of the incubation temperature by cooling methods, such as provision of shade, may minimize the frequency of non-modal scute patterns, with consideration for the natural sex ratio.

The nearly complete mitogenomes of Bolivaritettix sikkinensis and Bolivaritettix yuanbaoshanensis were determined and compared with the mitogenomes of other 29 caeliferans. These two newly determined mitogenomes displayed the typical gene organization and composition, codon usage and AT skew of most Caelifera mitogenomes. A comparison of 31 orthopteran sequences revealed that the main causes of the differences in total length are an A T-rich region and the length of IGS, even the rRNAs, and an AT content proportional to the value of AT-skew in the third position of PCGs. In Tetrigoidea, several tRNA were found to possess smaller TΨC or DHC loops and a number of special and conserved regions or motifs were found in tRNA genes and IGS, which may be useful as a molecular synapomorphy for this genus. ML and BI methods used in phylogenetic analysis revealed that Acridoidea species may have a close relationship with Tetrigoidea species.

This study proposes a simple standardized method for the production of analog X-ray images of dolphin teeth, and to explore its potential use as a complementary technique in the evaluation of dental pathology in small cetaceans. We investigated exposure times that produced the best results, and whether radiographs helped in the diagnosis of macroscopic abnormalities. Teeth of six species of dolphins (Delphinidae: Tursiops truncatus, Steno bredanensis, Sotalia guianensis, Delphinus sp., Stenella coeruleoalba, and Stenella frontalis) were X-rayed in an analog dental X-ray machine operating at 70 kVp and 7 mA. Intraoral size 2 standard films were used, and the focus—film distance was standardised at 35 cm. Those species with smaller teeth (total length 12–20 mm) had the best results when exposed for 0.3 seconds, while species with larger teeth (30–45 mm) had to be exposed for 0.4 seconds for their best result. Three independent examiners analysed all the images taken. The average pairwise percent agreement was 73% (Fleiss' Kappa = 0.229), suggesting fair agreement between examiners. Analog X-ray images produced were useful in complementing the diagnosis of dental pathology and abnormalities in dolphins, in addition to allowing the observation of internal details and lesion depths, which would not be possible with conventional macroscopic methods. The use of analog X-ray imaging is easily applicable to the study of dolphin teeth, with low operating costs and simple logistics compared to other non-destructive analytical approaches such as Micro-CT.

Chemical coding of stomatogastric nervous system (STNS) and enteric nervous system (ENS) of midgut and hindgut in the snail Megalobulimus abbreviatus was investigated using histochemistry, histofluorescence, and immunohistochemistry. The gastrointestinal plexuses, constituted by intrinsic neurons and fibers originating from the subesophageal ganglia and/or STNS, showed intense acetylcholinesterase (AChE) and nicotinamide adenine dinucleotide diaphorase (NADPHd) activity. The enteric neurons and fibers with AChE activity are scattered in the submucosa and between both muscular layers of gastrointestinal tract, whereas NADPHd neurons and fibers are more abundant between muscular layers than in the submucosa. Catecholaminergic nerve fibers and varicosities are found mainly within the submucosa across the mid- and hindgut. Serotoninand FMRFamide-immunoreactive neurons and fibers originating from the STNS are distributed in the submucosa of the intestine and rectum. FMRFamide-immunoreactive neurons and fibers are present in the mucosa, submucosa, and muscular layers of mid- and hindgut. The neuron-like intraepithelial cells exhibited AChE activity, a few NADPHd activity, and immunoreactivity for serotonin and FMRFamide. Intense glial fibrillary acidic protein (GFAP) immunoreaction is found throughout the intestine plexuses and in the STNS ganglia. The GFAP immunoreaction in intramural plexuses suggests the presence of glial cells as an important component of ENS in this pulmonate snail.

Photoperiodism is a biological seasonal timing system utilized to regulate development and reproduction in organisms. The freshwater micro-crustacean Daphnia pulex displays environmental sex determination, the precise physiological mechanisms of which are largely unknown due to the lack of an experimental system to induce female or male offspring production by alterations of the rearing environment. We recently found that D. pulex, WTN6 strain, produces female or male offspring in response to long-day or short-day conditions, respectively. Taking advantage of this system, here we report the photoperiodic response curve for male offspring production, showing 12 hours as natural critical daylength (50% incidence of male-producing mothers), and that male offspring inducibility is highly sensitive to photoperiodic alterations. By using monochromatic light emitting diode (LED) devices, we found that the effective wavelength is red-light (627 nm), which stably induces male offspring production. This suggests that the red-light photoreceptor may be decisive in the primary step of sex determination process in this strain. Our findings provide the first insights into photoperiodism and red-light as key factors in triggering male offspring production in daphnids.

Insulin/insulin-like growth factor signaling (IIS) is thought to be a central mediator of life history traits, but the generality of its role is not clear. Here, we investigated mRNA expression levels of three insulin-like peptide genes, the insulin-like receptor htk7, as well as several antioxidant genes, and the heat-shock protein hsp70 in the freshwater cnidarian Hydra vulgaris. Hydra polyps were exposed to a combination of different levels of food and perceived population density to manipulate life history traits (asexual reproduction and oxidative stress tolerance). We found that stress tolerance and the rate of asexual reproduction increased with food, and that these two effects were in significant interaction. Exposing animals to high perceived density resulted in increased stress tolerance or reduced reproduction only on lower food levels, but not on high food. The insulin-like receptor htk7 and the antioxidant gene catalase were significantly upregulated in the high density treatments. However, the expression level of insulin-like peptide genes, most antioxidant genes, and hsp70 were not affected by the experimental treatments. The higher expression level of htk7 may suggest that animals maintain a higher level of preparedness for insulin-like ligands at high population densities. However, the lack of difference between food levels suggests that IIS is not involved in regulating asexual reproduction and stress tolerance in hydra, or that its role is more subtle than a simple model of life history regulation would suggest.

Lampreys are among the most basal vertebrates, and similar to jawed vertebrates, they have two types of photoreceptors: long photoreceptors (LP; putative cones) and short photoreceptors (SP; putative rods). It is intriguing to examine the physiological properties of vision in these animals. Although there is an accumulating body of histological and biochemical studies of photoreceptors of the lamprey Lethenteron japonicum, many physiological characteristics of this species have not been described. In the present study, single-cell recordings of photoreceptors in the upstream migrant lamprey were performed to investigate the physiological properties of SP and LP of the lamprey Lethenteron japonicum. It was found that the sensitivity in LP at 560 nm was 2000 photons µm^-2, whereas that in SP at 520 nm was 67 photons µm^-2, which is approximately a 30-fold difference. Moreover, the response kinetics of LP was remarkably faster than those of SP, which is consistent with previous studies of other Northern hemisphere lampreys. Unexpectedly, the amplitude of single-photon response in the lamprey SP was approximately 0.12 pA, less than 1% of the circulating current. The small amplitude in lamprey SP may degrade the ability to detect single photons of this species. The spectral sensitivity analysis revealed that approximately 30% of all the chromophores are composed of A2 retinal, which may account for the relatively low amplitude of single-photon response in SP.

The systematic status of geographical variants of Arcuphantes hibanus Saito, 1992 belonging to the A. longiscapus species group, indigenous to western Honshu and Shikoku, Japan, was evaluated using morphological and molecular data. Two species, A. enmusubi Ihara, Nakano and Tomikawa, sp. nov. and A. occidentalis Ihara, Nakano and Tomikawa, sp. nov., are described, and A. hibanus is redescribed with redefinition of its taxonomic status. These three species are diagnosed by the characteristics of paracymbium, pseudolamella, and epigynal basal part. Phylogenetic trees obtained with mitochondrial cytochrome c oxidase subunit I and 16S rRNA markers showed that the variants are mutually genetically highly diverged. However, the mtDNA phylogenies failed to recover the monophyly of A. hibanus redefined herein. Contrary to the mtDNA phylogenetic analyses, a neighbor-network analysis of nuclear internal transcribed spacer 1 sequences of A. hibanus, A. enmusubi and A. occidentalis spiders showed that each of them forms a cluster. The results of mitochondrial and nuclear DNA analyses in each of the three species are briefly discussed, along with their taxonomic identities.

A new small, semi-arboreal toad of the genus Pelophryne is described from western Sarawak, Malaysian Borneo, on the basis of molecular and morphological evidence. Of the two morphotypes recognized in the genus, the new species belongs to the one in which the tips of the fingers are expanded into truncate discs. Among the species in the morphotype, the new species is most similar to P. murudensis, but differs from it by body size, relative hindlimb length, and dorsal coloration. The new species is currently known only from a limited area on Gunung (= Mt.) Penrissen, and future measures of its habitat conservation are necessary.

We describe a new species of sexually dimorphic brittle star, Ophiodaphne spinosa, from Japan associated with the irregular sea urchin, Clypeaster japonicus based on its external morphology, and phylogenetic analyses of mitochondrial COI (cytochrome c oxidase subunit I). Females of this new species of Ophiodaphne are characterized mainly by the presence of wavy grooves on the surface of the radial shields, needle-like thorns on the oral skeletal jaw structures, and a low length-to-width ratio of the jaw angle in comparison with those of type specimens of its Ophiodaphne congeners: O. scripta, O. materna, and O. formata. A tabular key to the species characteristics of Ophiodaphne is provided. Phylogenetic analyses indicate that the new species of Ophiodaphne, O. scripta, and O. formata are monophyletic. Our results indicate that the Japanese Ophiodaphne include both the new species and O. scripta, and that there are four Ophiodaphne species of sexually dimorphic brittle stars with androphorous habit.

To examine the level of genetic differentiation in the sequences of the mitochondrial D-loop gene of Rhinolophus ferrumequinum, and to evaluate the current taxonomic status of this species, 50 tissue samples of greater horseshoe bats were collected in 2011–2015 from 21 different localities in northwest, northeast, west, central, and south regions of Iran. Twenty-two published D-loop sequences from Europe (Switzerland, United Kingdom, Bulgaria, and Tunisia), and Anatolia (south, west, and east Turkey) were downloaded from GenBank. Molecular genetic analyses revealed remarkable variation among populations of R. ferrumequinum. Two major clades with strong support were identified within the greater horseshoe bat. One of these clades consists of individuals of R. ferrumequinum from Iran and eastern Turkey, and is further subdivided into two subclades. A second clade includes samples from western Turkey and Europe. The two subclades from Iran and Turkey and the second clade from western Turkey and Europe represent three diagnosable categories, which most probably warrant three subspecies for the species. Thus, based on genetic differences, it is clear that two subspecific populations are found in Iran: R. f. irani (southern Iran) and R. f. proximus (northern Iran).