Zoological Science

Older red-breasted flycatcher males (after the second year) have an orange patch on the throat and breast. To date, the occurrence of this ornament has been explained in terms of male-male interactions. In this paper, we show that badge size also influences the mating success of red-breasted-flycatcher males. In addition to the size of the ornament, arrival time was a second factor related to the males' mating success, but no effects of body parameters such as wing length, tarsus length, and body mass were observed. Mated males arrived significantly earlier than unmated ones. The arrival time of males was negatively correlated to body mass and positively correlated to tarsus length but no relation to wing length or badge size was observed. No correlations between badge size and body parameters were observed. This ornament was evolved through sexual selection, with both male-male interaction and selection pressure arising from female preference for males with larger badges.

Mushroom bodies (MBs) are insect brain centers involved in multimodal sensory integration and memory formation. Advanced Hymenoptera, such as ants and bees, have particularly large and elaborately organized MBs, which are repeatedly implicated in complex behaviors. In this study, to address the developmental aspects of their MBs, gliogenesis of mushroom body neuroblasts (MB Nbs) was examined in the carpenter ant Camponotus japonicus. Reversed Polarity (REPO) is a paired-like homeodomain protein located exclusively in the nucleus of differentiating glial cells in the fruit fly Drosophila melanogaster. First, the molecular aspects of C. japonicus REPO (CjREPO) were identified. Then, the antibody (CjREPO-antibody) was raised against a peptide of CjREPO. Immunohistochemistry revealed that the strong labeling was located in the nucleus of glial cells in the developing brains, whereas no immunoreactivity was detectable in progeny derived from MB Nbs. These findings suggest that MB Nb in the ant is a neuronal precursor that does not produce glial cells.

The asymmetrical and latitudinal formation of the gonads during early development in the dwarf gourami Colisa lalia was histologically observed using fish reared in laboratory. Hatching larvae obtained 33 hours after spawning possessed primordial germ cells (PGCs), which aggregated to the dorsal surface of the gut. In prolarvae on day 7, the gonadal anlagen were still situated on the dorsal surface of the gut, however, in those on day 10, the left gonadal anläge began to shift leftward, although the coelom did not develop sufficiently. In prolarvae on day 20, the right gonadal anlage also began to move leftward. During this period, the gut developed considerably in the right side of the coelom. On day 25, the developing gonads were located in the interspace of the developing spiral valve intestine. Sex differentiation of gonads appeared to begin by day 25. From those observations, we concluded that asymmetricity of gonads in C. lalia is caused by a limited space of the coelom opened on the left side of the body during the early phase of the formation of gonadal anlagen, which may be accurately determined by the position in which the gut develops.

The asymmetrical and latitudinal formation of the gonads during early development in the dwarf gourami Colisa lalia was histologically observed using fish reared in laboratory. Hatching larvae obtained 33 hours after spawning possessed primordial germ cells (PGCs), which aggregated to the dorsal surface of the gut. In prolarvae on day 7, the gonadal anlagen were still situated on the dorsal surface of the gut, however, in those on day 10, the left gonadal anläge began to shift leftward, although the coelom did not develop sufficiently. In prolarvae on day 20, the right gonadal anlage also began to move leftward. During this period, the gut developed considerably in the right side of the coelom. On day 25, the developing gonads were located in the interspace of the developing spiral valve intestine. Sex differentiation of gonads appeared to begin by day 25. From those observations, we concluded that asymmetricity of gonads in C. lalia is caused by a limited space of the coelom opened on the left side of the body during the early phase of the formation of gonadal anlagen, which may be accurately determined by the position in which the gut develops.

Termites are social insects with an extraordinary ability to digest cellulose. Termite societies are structured into castes, and patterns of postembryonic development vary between different termite species. The apterous line may exhibit polymorphism (“physical castes”), in which workers are dimorphic and soldiers can be either dimorphic or trimorphic. We examined the occurrence of polymorphism in the apterous line of Velocitermes heteropterus and determined the developmental pathways for this termite species. We also investigated the expression of the cellulase genes encoding β-glucosidase and endo-β-1,4-glucanase among the castes to determine whether there is a difference in digestion and, consequently, a possible division of labor with respect to this activity among the worker castes. The apterous line of V. heteropterus presents individuals of both sexes with two larval instars. The female larvae become major workers, and the male larvae become minor workers and soldiers. The expression of β-glucosidase was similar within the castes, but the expression of endo-β-1,4-glucanase was higher in workers than in soldiers. No significant differences were found between minor and major workers. These results suggest that there is no division of labor between the minors and majors with regard to cellulose digestion, with both workers contributing similarly to this process.

Termites are social insects with an extraordinary ability to digest cellulose. Termite societies are structured into castes, and patterns of postembryonic development vary between different termite species. The apterous line may exhibit polymorphism (“physical castes”), in which workers are dimorphic and soldiers can be either dimorphic or trimorphic. We examined the occurrence of polymorphism in the apterous line of Velocitermes heteropterus and determined the developmental pathways for this termite species. We also investigated the expression of the cellulase genes encoding β-glucosidase and endo-β-1,4-glucanase among the castes to determine whether there is a difference in digestion and, consequently, a possible division of labor with respect to this activity among the worker castes. The apterous line of V. heteropterus presents individuals of both sexes with two larval instars. The female larvae become major workers, and the male larvae become minor workers and soldiers. The expression of β-glucosidase was similar within the castes, but the expression of endo-β-1,4-glucanase was higher in workers than in soldiers. No significant differences were found between minor and major workers. These results suggest that there is no division of labor between the minors and majors with regard to cellulose digestion, with both workers contributing similarly to this process.

We compared the breeding season and genetic population structure of six sentinel crab (Macrophthalmus banzai) populations in southwestern Japan. Ovigerous females from Northern group populations (Wakayama, Kochi, and Tanega-shima) were observed from March to September, whereas ovigerous females from Southern group populations (Amami-oshima, Okinawa-jima, and Iriomote-jima) were observed from October to May. Genetic analysis using two markers corresponding to mitochondrial DNA encoding cytochrome oxidase subunit I (COI) and the large subunit of ribosomal RNA (16Sr-RNA) revealed a marked genetic difference between the Northern and Southern groups. A genetic boundary exists between the Tanega-shima and Amami-oshima populations, which is consistent with the interpopulation difference in the breeding season.

A carnivoran mammal endemic to Japan, the Japanese marten (Martes melampus) is native in forested regions on Honshu, Shikoku, Kyushu (main islands of Japan), and the Tsushima Islands. The Tsushima population is classified as a different subspecies (M. m. tsuensis) from populations on the main islands (M. m. melampus). To elucidate the genetic structure of the Tsushima population, we genotyped 101 individuals from the Tsushima Islands and 43 individuals from Honshu and Kyushu using 10 microsatellite loci, and performed population genetic analyses on the genotype data. Genetic diversity was lower in the Tsushima population than in three geographic populations on the main islands: heterozygosity was 0.189–0.364 in the former, compared to 0.457–0.747 in the latter. In addition, high pairwise Fst values (0.485–0.682) and Nei's standard distance (0.550–1.183) between the Tsushima and main-island populations indicated a high degree of genetic differentiation. Finally, a Bayesian clustering analysis showed that the Tsushima population is apparently differentiated from the main-island populations and comprises two genetic clusters. A factorial correspondence analysis corroborated these results. Our results suggest that restricted gene flow or inbreeding may have reduced genetic diversity in the Tsushima population, which has been geographically isolated from the main-island populations since the formation of Tsushima Strait.

A carnivoran mammal endemic to Japan, the Japanese marten (Martes melampus) is native in forested regions on Honshu, Shikoku, Kyushu (main islands of Japan), and the Tsushima Islands. The Tsushima population is classified as a different subspecies (M. m. tsuensis) from populations on the main islands (M. m. melampus). To elucidate the genetic structure of the Tsushima population, we genotyped 101 individuals from the Tsushima Islands and 43 individuals from Honshu and Kyushu using 10 microsatellite loci, and performed population genetic analyses on the genotype data. Genetic diversity was lower in the Tsushima population than in three geographic populations on the main islands: heterozygosity was 0.189–0.364 in the former, compared to 0.457–0.747 in the latter. In addition, high pairwise Fst values (0.485–0.682) and Nei's standard distance (0.550–1.183) between the Tsushima and main-island populations indicated a high degree of genetic differentiation. Finally, a Bayesian clustering analysis showed that the Tsushima population is apparently differentiated from the main-island populations and comprises two genetic clusters. A factorial correspondence analysis corroborated these results. Our results suggest that restricted gene flow or inbreeding may have reduced genetic diversity in the Tsushima population, which has been geographically isolated from the main-island populations since the formation of Tsushima Strait.

The ectothermic nature of reptiles makes them especially sensitive to global warming. Although climate change and its implications are a frequent topic of detailed studies, most of these studies are carried out without making a distinction between populations. Here we present the first study of an Aspidoscelis species that evaluates the effects of global warming on its distribution using ecological niche modeling. The aims of our study were (1) to understand whether predicted warmer climatic conditions affect the geographic potential distribution of different climatic groups of Aspidoscelis costata costata and (2) to identify potential altitudinal changes of these groups under global warming. We used the maximum entropy species distribution model (MaxEnt) to project the potential distributions expected for the years 2020, 2050, and 2080 under a single simulated climatic scenario. Our analysis suggests that some climatic groups of Aspidoscelis costata costata will exhibit reductions and in others expansions in their distribution, with potential upward shifts toward higher elevation in response to climate warming. Different climatic groups were revealed in our analysis that subsequently showed heterogeneous responses to climatic change illustrating the complex nature of species geographic responses to environmental change and the importance of modeling climatic or geographic groups and/or populations instead of the entire species' range treated as a homogeneous entity.

The arrangement of the hepatic tissue is directly related to physiological characteristics of animals, such as ectothermy, diet, and reproductive status. Here, we describe the anatomy, histology, and ultrastructure of the liver in adult males of Eupemphix nattereri during the breeding season. The liver is an organ with an irregular shape, red in color, and occupies a large portion of the body cavity. Anatomically, it is divided into three lobes: right, mid, and left. Further subdivision into lobules is not observed. A thin capsule of connective tissue covers externally the organ, which is responsible for its support and protection. The hepatic parenchyma is formed by two layers of polyhedralshaped hepatocytes arranged in a double cordon. These cordons are filled with hepatic sinusoids that greatly vary in size and are closely associated with hepatocytes. There are also bile canaliculi and immune cells between hepatic cordons—the melanomacrophages. These canaliculi are covered with short microvilli, which protrude into the lumen. Melanomacrophages have several cytoplasmic substances, such as melanin, lipofuscin, and hemosiderin, which form due to liver metabolism and contribute to the typical coloration of the organ. A large amount of mitochondria and other organelles, such as a well-developed Golgi apparatus, smooth endoplasmic reticulum, and abundant glycogen are found in the cytoplasm of hepatocytes.

The arrangement of the hepatic tissue is directly related to physiological characteristics of animals, such as ectothermy, diet, and reproductive status. Here, we describe the anatomy, histology, and ultrastructure of the liver in adult males of Eupemphix nattereri during the breeding season. The liver is an organ with an irregular shape, red in color, and occupies a large portion of the body cavity. Anatomically, it is divided into three lobes: right, mid, and left. Further subdivision into lobules is not observed. A thin capsule of connective tissue covers externally the organ, which is responsible for its support and protection. The hepatic parenchyma is formed by two layers of polyhedralshaped hepatocytes arranged in a double cordon. These cordons are filled with hepatic sinusoids that greatly vary in size and are closely associated with hepatocytes. There are also bile canaliculi and immune cells between hepatic cordons—the melanomacrophages. These canaliculi are covered with short microvilli, which protrude into the lumen. Melanomacrophages have several cytoplasmic substances, such as melanin, lipofuscin, and hemosiderin, which form due to liver metabolism and contribute to the typical coloration of the organ. A large amount of mitochondria and other organelles, such as a well-developed Golgi apparatus, smooth endoplasmic reticulum, and abundant glycogen are found in the cytoplasm of hepatocytes.

Anemonefish, Amphiprion spp., are socially controlled, protandrous sex changers with a monogamous mating system. Under certain conditions, sexually immature anemonefish with ambisexual gonads differentiate directly into males or females. Formation and maintenance of social rank in a group are considered key requirements for the induction of sex change or differentiation. Generally, each animal living in a social group experiences a different level of social stress in accordance with its social rank, and we hypothesize that the stress situation of individual anemonefish influences its sex determination. Groups of three sexually immature anemonefish were placed into each of five experimental tanks and kept for 10 days to allow for social rank formation and behavioral observation. The fish were then euthanized, and blood and brain samples were collected from each fish. The social rank of each individual was distinguishable from day 1 of the experiment. Aggressive behaviors were most frequent and blood Cortisol values were higher in dominant individuals. The transcription of mRNA for stress-related genes, i.e., those encoding for glucocorticoid and arginine vasotocin receptors, was higher in the brains of dominant individuals than in other social ranks. Furthermore, we detected higher transcription levels of gonad and brain aromatase genes, which encode the enzyme that converts androgens into estrogens, in the brains of dominant individuals. These results suggest that social rank reflects the blood Cortisol value, which in turn leads to sex differentiation by manipulating transcription of genes, including aromatase genes, in the brain.

A new species of genus Hydra (Cnidaria: Hydrozoa: Hydridae), Hydra shenzhensis sp. nov. from Guangdong Province, China, is described and illustrated. Most polyps have five tentacles. Column length reaches 11 mm when relaxed. Buds do not acquire tentacles synchronously. Stenotele is broad and pyriform in shape, 1.2 times as long as its width. Holotrichous isorhiza is asymmetrical and slender (more than 2.7 times as long as its width), with transverse and slanting coils. Atrichous isorhiza is long, resembling a melon-seed in shape. Desmoneme is asymmetrically pyriform in shape. The new species, belonging to the vulgaris group, is dioecious; sexual reproduction was found to occur mostly during November and December under conditions of dense culture or food shortage. Two to thirteen testes, cone-like shape with papilla, formed beneath the tentacles. One to three ovaries, with an egg cup, milky white in color, formed on body column. Ninety percent of individuals developed only one ovum. On a mother polyp, a fertilized ovum developed an embryonic theca covering its surface. The embryotheca is brown, with a spine-like structure, covering a layer of transparent, membrane-like material. For phylogenetic analysis, the mitochondrial cytochrome oxidase subunit I gene (COI) of six hydra species collected from China was amplified by polymerase chain reaction (PCR) and sequenced. Morphological characters in combination with molecular evidence support the hydra described here as a new species.