Zoological Science

Innate predator recognition confers a survival advantage to prey animals. We investigate whether giant pandas exhibit innate predator recognition. We analyzed behavioral responses of 56 naive adult captive giant pandas (Ailuropoda melanoleuca), to urine from predators and non-predators and water control. Giant pandas performed more chemosensory investigation and displayed flehmen behaviors more frequently in response to predator urine compared to both non-predator urine and water control. Subjects also displayed certain defensive behaviors, as indicated by vigilance, and in certain cases, fleeing behaviors. Our results suggest that there is an innate component to predator recognition in captive giant pandas, although such recognition was only slight to moderate. These results have implications that may be applicable to the conservation and reintroduction of this endangered species.

The Japanese wood mouse Apodemus speciosus eats large, hard-walled walnuts of Juglans ailanthifolia immediately after finding or after hoarding them. However, not all individuals can efficiently eat the nuts. In this study, to examine local variation in the ability to eat walnuts, feeding behavior was compared among nine wood mouse populations, four from mainland Honshu, where the walnut tree is distributed, and five from the Izu Islands (30–100 km south of Honshu), which lack the tree species. To avoid the effects of pre-capture experience with walnuts, mice from areas lacking the walnut trees were used for testing, even in the Honshu sites. Most mice from Honshu were able to eat walnuts after a 14-day training period, whereas most insular mice could not, with the exception of mice on Kouzushima Island. An analysis of the population genetic structures of these mice based on sequences of the mitochondrial control (D-loop) region revealed that the four insular populations are genetically distinct from the mainland populations, whereas the Kouzushima population remains genetically similar to the mainland populations. The relatively recent colonization of Kouzushima may explain why mice from this island were able to feed on walnuts despite the lack of walnut trees on the island. Thus, walnut-feeding ability appears to have some innate basis in the Japanese wood mouse, and this trait would be selected for in a walnut-available environment as it would better enable mice to survive during food shortages.

The Japanese wood mouse Apodemus speciosus eats large, hard-walled walnuts of Juglans ailanthifolia immediately after finding or after hoarding them. However, not all individuals can efficiently eat the nuts. In this study, to examine local variation in the ability to eat walnuts, feeding behavior was compared among nine wood mouse populations, four from mainland Honshu, where the walnut tree is distributed, and five from the Izu Islands (30–100 km south of Honshu), which lack the tree species. To avoid the effects of pre-capture experience with walnuts, mice from areas lacking the walnut trees were used for testing, even in the Honshu sites. Most mice from Honshu were able to eat walnuts after a 14-day training period, whereas most insular mice could not, with the exception of mice on Kouzushima Island. An analysis of the population genetic structures of these mice based on sequences of the mitochondrial control (D-loop) region revealed that the four insular populations are genetically distinct from the mainland populations, whereas the Kouzushima population remains genetically similar to the mainland populations. The relatively recent colonization of Kouzushima may explain why mice from this island were able to feed on walnuts despite the lack of walnut trees on the island. Thus, walnut-feeding ability appears to have some innate basis in the Japanese wood mouse, and this trait would be selected for in a walnut-available environment as it would better enable mice to survive during food shortages.

We previously reported that thyroid hormones are involved in the formation of the adult rudiment and adult-type skeleton in sea urchin larvae, as well as in the resorption of larval tissues. In the present study, to search for the presence of thyroid hormone receptor in sea urchin larvae, we performed a ligand-binding assay between radiolabeled thyroid hormones and nuclear extracts from the larvae of the sea urchin Hemicentrotus pulcherrimus. The presence of binding sites with a high affinity to thyroxine (T4) was detected in the nuclear extract, but not in the cytoplasmic fraction. The dissociation constants for the T4 binding to the nuclear extracts were estimated to be about 18 pM from the mesenchyme-blastula stage to the four-armed pluteus stage. The quantity of T4 binding sites in the nuclear extracts increased during larval development. These results suggest that the binding affinity to T4 in the nuclear extracts was caused by a putative nuclear thyroid hormone receptor in sea urchin larvae.

An invertebrate biogenic amine, octopamine, plays diverse roles in multiple physiological processes (e.g. neurotransmitter, neuromodulator, and circulating neurohormone). Octopamine is thought to function by binding to G-protein-coupled receptors. In Drosophila, three ββ-adrenergic-like octopamine receptors (Octββ1R, Octββ2R, and Octββ3R) have been identified. We investigated the expression of three OctββR genes in embryos, larvae, and adults. These OctββRs showed distinct expression patterns in the central nervous system (CNS) throughout development, and Octββ3R expression was evident in an endocrine organ, the ring gland, in larvae. In larvae, Octββ1R, Octββ2R, and Octββ3R were expressed in salivary glands and imaginal discs, Octββ2R and Octββ3R in midgut, and Octββ3R in gonads. In adult, besides in the CNS, each OctββR was strongly expressed in ovary and testis. Our findings provide a basis for understanding the mechanisms by which OctββRs mediate multiple diverse octopaminergic functions during development.

An invertebrate biogenic amine, octopamine, plays diverse roles in multiple physiological processes (e.g. neurotransmitter, neuromodulator, and circulating neurohormone). Octopamine is thought to function by binding to G-protein-coupled receptors. In Drosophila, three ββ-adrenergic-like octopamine receptors (Octββ1R, Octββ2R, and Octββ3R) have been identified. We investigated the expression of three OctββR genes in embryos, larvae, and adults. These OctββRs showed distinct expression patterns in the central nervous system (CNS) throughout development, and Octββ3R expression was evident in an endocrine organ, the ring gland, in larvae. In larvae, Octββ1R, Octββ2R, and Octββ3R were expressed in salivary glands and imaginal discs, Octββ2R and Octββ3R in midgut, and Octββ3R in gonads. In adult, besides in the CNS, each OctββR was strongly expressed in ovary and testis. Our findings provide a basis for understanding the mechanisms by which OctββRs mediate multiple diverse octopaminergic functions during development.

The complete 16053 bp mitochondrial genome (mitogenome) sequence of Locusta migratoria migratoria has been determined. This mitogenome contains the base compositional biases and codon usage typical of metazoans, and the RSCU values indicate a negative correlation with the C and G contents in codon. The orientation and gene order of the L. migratoria migratoria is identical to Locusta migratoria migratoiodes. An unusual feature of the L. migratoria migratoria mitogenome is the presence of three tRNA-like structures on the N-strand: one tRNA^Ile-like and two tRNA^Leu(CUN)-like sequences. The tRNA-like sequences have proper folding structures and anticodons sequences. Two repeated DNA sequences, Rpt I and Rpt II, were found in the A+T-rich region of the L. migratoria migratoria mitogenome. Both repeated sequences have various features. In the 5′ region of Rpt I, a 51 bp fragment is localized in the srRNA gene; and there are two tandemly sub-repeated DNA sequences (sub-Rpts), Rpt 1–4, within Rpt I and Rpt II. One stem-loop structure on the N-strand that may be involved in the N-strand replication initiation was found in the A+T-rich region.

The complete 16053 bp mitochondrial genome (mitogenome) sequence of Locusta migratoria migratoria has been determined. This mitogenome contains the base compositional biases and codon usage typical of metazoans, and the RSCU values indicate a negative correlation with the C and G contents in codon. The orientation and gene order of the L. migratoria migratoria is identical to Locusta migratoria migratoiodes. An unusual feature of the L. migratoria migratoria mitogenome is the presence of three tRNA-like structures on the N-strand: one tRNA^Ile-like and two tRNA^Leu(CUN)-like sequences. The tRNA-like sequences have proper folding structures and anticodons sequences. Two repeated DNA sequences, Rpt I and Rpt II, were found in the A+T-rich region of the L. migratoria migratoria mitogenome. Both repeated sequences have various features. In the 5′ region of Rpt I, a 51 bp fragment is localized in the srRNA gene; and there are two tandemly sub-repeated DNA sequences (sub-Rpts), Rpt 1–4, within Rpt I and Rpt II. One stem-loop structure on the N-strand that may be involved in the N-strand replication initiation was found in the A+T-rich region.

The organization of the stomach in the compound styelid ascidian, Polyandrocarpa misakiensis, is described, and the morphology and cell types of the stomach is discussed from the phylogenetic viewpoint. The stomach is a sac-like organ whose wall is formed into longitudinal folds. The stomach consists of external and internal epithelium. The internal epithelium is simple columnar, except for the bottom of the folds. There are five cell types: absorptive cells, zymogenic cells, endocrine cells, ciliated mucous cells, and undifferentiated cells. The absorptive cells have numerous microvilli. The apical region of these cells is occupied by coated vesicles. The zymogenic cells have a conical outline and a few microvilli on their apical surfaces. There are secretory granules in the apical region of zymogenic cells. The endocrine cells have low cell height and electron-dense granules around the nucleus. Endocrine cells have one or two cilia and a few microvilli on the apical surfaces. The basolateral part of these cells often bulges into the adjoining cells. Immunoelectron microscopy revealed that some endocrine cells have serotonin-like immunoreactivity. The ciliated mucous cells are restricted to a single ventral groove. They have numerous microvilli and a few cilia on their apical surfaces. Moderately electron-dense granules are accumulated in the apical part of the ciliated mucous cells. Undifferentiated cells, filled with free ribosomes, form a pseudostratified epithelium in the base of each fold. The nucleus of undifferentiated cells has a prominent nucleolus. The pseudostratified epithelium of the pyloric caecum consists of electron-dense and electron-light cells.

We previously revealed the presence of six genetically distinct matrilineal populations of the Japanese dormouse Glirulus japonicus in the distribution range of Honshu, Shikoku, and Kyushu islands. In this study, we extended this analysis using mitochondrial cytochrome b gene sequences (n = 96) and Y-chromosome-specific SRY gene sequences (n = 22) from individuals collected from Honshu, Shikoku, Kyushu, and Oki Dogo I. The cytochrome b sequence data allowed us to define precise geographic ranges of the six previously known and three newly found distinct matrilineal lineages: northeastern Honshu (I), east-central Honshu (II), west-central Honshu and the Kii Peninsula (III), the western part of Honshu (IV), Shikoku (V), westernmost Honshu and Kyushu (VI), the northern part of central Honshu (VII), the southern part of central Honshu (VIII), and Oki Dogo I. (IX). Our inference of geographic borders suggests that regions of lower and higher altitudes in the mountain systems played important roles in driving the hosting and separation of lineages, respectively. Six matrilineal lineages (I, II, V, VI, VIII, and XI) were shown to possess their own SRY haplotypes, while lineages III and IV shared one haplotype. These data together with our previous observation of nuclear ribosomal RNA gene variation indicate advanced populational subdivision in this species. It is thus evident that each of the populations, including those living at high latitudes and in limited geographic spaces, have survived for several million years. A specific ability to tolerate cold may have permitted G. japonicus to preserve anciently diverged lineages in each locality.

The gobiid fish Trimma okinawae changes its sex bi-directionally according to its social status. Morphological changes in the urinogenital papillae (UGP) of this fish have been reported during sex change. However, there have been no detailed observations of such changes. Here, we histologically examined the UGP structure of male- and female-phase fish. UGPs of fish in female and male phase contained both oviducts and sperm ducts. Both ducts were coalesced into one duct within the posterior region of the UGP. Female-phase fish had many longitudinal folds in the hypertrophied tunica mucosa of the oviduct, which was found to be responsible for the transport of eggs and the removal of follicular cells from the oocyte. In contrast, male-phase fish had an immature oviduct and a mature sperm duct in the UGP. In the male-phase fish, the co-existence of spermatozoa and fibrillar secretions was observed in the sperm duct during spermiation.

Paramacrochiron thailandicum n. sp. (Copepoda: Cyclopoida: Macrochironidae) is described from the rhizostome medusa Rhopilema hispidum occurring in the Gulf of Thailand. The new species is distinguishable from other congeners mainly by detailed features of the fourth legs and the urosome in both sexes. Copepodid and adult stages of the genus Paramacrochiron seem to be host-specific to rhizostome medusae, but may spend periods free in the plankton or benthos during the absence of the host. A cladistic analysis shows that the Macrochironidae comprises two main lineages. Paramacrochiron is recovered as a monophyletic group, located on one lineage together with Pseudomacrochiron, which appears as a paraphyletic taxon with the limited character set used. The other main lineage comprises the genera Macrochiron and Sewellochiron, but the sole species of the latter genus, Sewellochiron fidens, is nested within Macrochiron. This analysis provides little support for maintaining Sewellochiron as a separate genus.

We reveal the existence of a cryptic species of Acropora solitaryensis ( Veron and Wallace, 1984 ), a dominant species in high-latitude coral communities. Although some morphs, such as arborescent table (AR), solid plate (PL), and intermediate (IM) forms, had been known in this species, it was unclear whether these are reproductively isolated from one another. Here, potential reproductive exchange between two representative morphs, AR and PL, were examined using genetic and reproductive methods. Molecular phylogenetic analyses using both mitochondrial and nuclear molecular markers (mitochondrial control region and mini-collagen intron, respectively) indicated that AR is clearly distinct from PL, suggesting that gene flow between the morphs is absent. In cross-fertilization experiments, gametic compatibility between AR and PL was extremely low, suggesting prezygotic isolation of these morphs. These results strongly suggest that AR and IM forms are variations of A. solitaryensis, whereas PL form may be an undescribed species. In addition, AR was closely related genetically to A. pruinosa, which is a high-latitude species with arborescent form, and AR and A. pruinosa were able to hybridize, although with lower fertilities than observed in intra-specific crosses. The two species are thus likely to have speciated not in tropical regions, but in non-reef regions due to habitat segregation.