Zoological Science

Termite soldiers represent a peculiar caste among social insects in terms of their specific defensive roles. Numbers of soldiers are relatively low in a mature colony, and it is impossible to identify the individuals that will differentiate into soldiers. If it were possible to specify these individuals prior to soldier differentiation, it would facilitate a better understanding of the regulatory mechanisms of soldier differentiation under natural condition. Here we analyzed soldier differentiation in incipient colonies of Zootermopsis nevadensis, in which only a single soldier develops via a presoldier stage, and is stable during early colony ontogeny. We observed that the oldest third instar differentiated into a presoldier within about eight days from its appearance. Caste differentiation, however, was not strictly determined on an individual basis. The oldest third instars never differentiated into presoldiers if primary reproductives were removed soon after their appearance. Behavioral observations of primary reproductives and their offspring prior to presoldier differentiation, showed that primary reproductives transferred proctodeal materials to the oldest third instar significantly more frequently than to other larva. A high juvenile hormone (JH) titer is required for the soldier differentiation, and we suggest that the JH itself or some nutrients/factors increasing larval JH titer may be transferred to the oldest third instar via a parental proctodeal fluid.

We compared two types of light traps used for monitoring mosquito abundance in the hydroelectric reservoir of Simplício, Além Paraíba — Minas Gerais. Mosquitoes were captured bimonthly using automatic CDC and Shannon traps before the filling of the hydroelectric plant reservoir from December 2008 to December 2009. In total, 1474 specimens from 13 genera were captured. Among the captured specimens, several species known to be vectors of disease-causing agents for humans and/or animals were identified, including Anopheles aquasalis, Aedes albopictus, Coquillettidia venezuelensis, Haemagogus leucocelaenus, and Aedes scapularis. Sampling efficacy between the four capture sites was not found to be significantly different, irrespective of species captured or type of trap used. Poor correlation (r x, y = -0.0444) between the number of mosquito species and capture site was observed when not influenced by the type of trap used. Among the installation sites of the CDC and Shannon traps in the areas investigated, CDC traps fixed in livestock shelters obtained an overall higher abundance of species captured.

We compared two types of light traps used for monitoring mosquito abundance in the hydroelectric reservoir of Simplício, Além Paraíba — Minas Gerais. Mosquitoes were captured bimonthly using automatic CDC and Shannon traps before the filling of the hydroelectric plant reservoir from December 2008 to December 2009. In total, 1474 specimens from 13 genera were captured. Among the captured specimens, several species known to be vectors of disease-causing agents for humans and/or animals were identified, including Anopheles aquasalis, Aedes albopictus, Coquillettidia venezuelensis, Haemagogus leucocelaenus, and Aedes scapularis. Sampling efficacy between the four capture sites was not found to be significantly different, irrespective of species captured or type of trap used. Poor correlation (r _{x, y} = -0.0444) between the number of mosquito species and capture site was observed when not influenced by the type of trap used. Among the installation sites of the CDC and Shannon traps in the areas investigated, CDC traps fixed in livestock shelters obtained an overall higher abundance of species captured.

Placozoans are marine invertebrates found in tropical and subtropical waters. Their body plan is among the simplest of free-living animals. The present study determined the mitochondrial genome sequence of a placozoan collected on the coast of Shirahama, Wakayama, Honshu, Japan, and compared it with those of Trichoplax adhaerens from the Red Sea and of three strains from the Caribbean Sea. The sequences of mitochondrial respiratory chain of the Japanese placozoan genes are very similar to those of the BZ49 strain from the Caribbean Sea. However, there are distinct differences in gene arrangement, such as the location of two open reading frames. This Japanese placozoan is therefore distinguishable from the other strains. Based on current knowledge of placozoan 16S diversity our ‘Shirahama’ strain most likely represents the H15 lineage, known from the Philippines. In the mitochondrial genome of placozoans, substitution rates are slower than in bilaterians, whereas the rate of rearrangements is faster.

Placozoans are marine invertebrates found in tropical and subtropical waters. Their body plan is among the simplest of free-living animals. The present study determined the mitochondrial genome sequence of a placozoan collected on the coast of Shirahama, Wakayama, Honshu, Japan, and compared it with those of Trichoplax adhaerens from the Red Sea and of three strains from the Caribbean Sea. The sequences of mitochondrial respiratory chain of the Japanese placozoan genes are very similar to those of the BZ49 strain from the Caribbean Sea. However, there are distinct differences in gene arrangement, such as the location of two open reading frames. This Japanese placozoan is therefore distinguishable from the other strains. Based on current knowledge of placozoan 16S diversity our ‘Shirahama’ strain most likely represents the H15 lineage, known from the Philippines. In the mitochondrial genome of placozoans, substitution rates are slower than in bilaterians, whereas the rate of rearrangements is faster.

We conducted a comprehensive allozymic analysis of 393 specimens of the Japanese clawed salamander, Onychodactylus japonicus, from 33 populations of northeastern Honshu, Japan. As a result, these populations exhibited extensive geographic genetic differentiation, and four major genetic groups (N-Tohoku, S-Tohoku, Tsukuba, and SW-Honshu groups) were consistently recognized. Of these, the Tsukuba group was geographically isolated from all the others, whereas the N- and S-Tohoku groups, and the S-Tohoku and SW-Honshu groups, respectively, were nearly parapatric, without distinct geographic barriers. The magnitude of genetic distances between the four groups, except for between the N- and S-Tohoku groups, was as large as that normally found among different hynobiid species. A structure analysis detected no admixture of the N- and S-Tohoku groups, whereas few hybrids were found between the S-Tohoku and SW-Honshu around their contact zone. However, genetic exchange between these parapatric groups appeared to be infrequent, suggesting the presence of some isolation mechanisms between them. Within each group, only the S-Tohoku group exhibited an extensive level of population genetic structure that roughly distinguishes the eastern, central, and northwestern subgroups, indicating the complexity of the phylogeographic traits of this group. These results strongly suggest that populations of O. japonicus from northeastern Japan encompass several cryptic species.

The population genetic structure and demographic history of the ground beetle Pheropsophus jessoensis (Coleoptera: Carabidae) from the Tsinling-Dabashan Mountains, central China were estimated using the mtDNACol-tRNALeu-mtDNAColl region as a molecular marker. 184 individuals from 25 local populations, were collected. The haplotype diversity (H d) of total and each individual sampled population was high, and was accompanied by lower nucleotide diversity (P i). AMOVA analysis suggested that most of the variation was within populations (92.17%), while differentiation of among populations only contributed 7.83% to the total. Mantel test results showed significant correlation between the pairwise calculated genetic distance and pairwise calculated geographical distance of the populations (R xy = 0.360529, P = 0.00001 < 0.01), indicating the presence of isolationby-distance. No phylogeographic structure was found within the Tsinling-Dabashan Mountains region. Statistical phylogeographic analysis indicated that the contemporary populations are derived from multiple ancestral-refugial source populations. Gene flow calculated through the N m was high between many pairs of populations, which was probably due to ancient vicariance and subsequent rapid expansion of populations. The results of neutral test, mismatch distribution analyses, and Bayesian Skyline Plot (BSP) analysis together indicated a sudden demographic expansion. The estimated expansion time of individual haplogroup and the whole sampled population were 0.012–0.278 Myr, and a sudden expansion was identified between 0.05 Myr to 0.01 Myr by BSP. The postglacial population expansion might lead to the lack of phylogeographic structure.

The population genetic structure and demographic history of the ground beetle Pheropsophus jessoensis (Coleoptera: Carabidae) from the Tsinling-Dabashan Mountains, central China were estimated using the mtDNACol-tRNALeu-mtDNAColl region as a molecular marker. 184 individuals from 25 local populations, were collected. The haplotype diversity (H _d) of total and each individual sampled population was high, and was accompanied by lower nucleotide diversity (P _i). AMOVA analysis suggested that most of the variation was within populations (92.17%), while differentiation of among populations only contributed 7.83% to the total. Mantel test results showed significant correlation between the pairwise calculated genetic distance and pairwise calculated geographical distance of the populations (R _xy = 0.360529, P = 0.00001 < 0.01), indicating the presence of isolationby-distance. No phylogeographic structure was found within the Tsinling-Dabashan Mountains region. Statistical phylogeographic analysis indicated that the contemporary populations are derived from multiple ancestral-refugial source populations. Gene flow calculated through the N _m was high between many pairs of populations, which was probably due to ancient vicariance and subsequent rapid expansion of populations. The results of neutral test, mismatch distribution analyses, and Bayesian Skyline Plot (BSP) analysis together indicated a sudden demographic expansion. The estimated expansion time of individual haplogroup and the whole sampled population were 0.012–0.278 Myr, and a sudden expansion was identified between 0.05 Myr to 0.01 Myr by BSP. The postglacial population expansion might lead to the lack of phylogeographic structure.

The identification of balanomorph larvae plays an important role in ecological study and for protection against biofouling. However, it is difficult to identify species of cyprids (settling larvae) of balanomorph barnacles, as they show remarkably similar morphology. Some authors have suggested distinguishing cyprids of different species by carapace length, pigmentation, and fine carapace detail. However, such criteria are only applicable to a narrow range of balanomorph species. Recently, we were have serendipitously found species-specific distribution of fluorescent substances in cultured cyprids obtained from adult balanomorph barnacles, collected near the coast of Japan. Fluorescent patterns (FPs) of cyprids from 11 species were classified into five major groups. Cyprids specimens collected from the field were estimated, based on the FPs and other morphological characteristics (pigmentation and carapace length), after which their species were identified using the following two criteria: the morphology of adults derived from the field cyprids that adhered to a culture dish, and cyprid 12S rRNA gene sequence. The results of species estimation by FPs largely corresponded to the correct species identification. Other FP groups were found in the field cyprids. This study of FPs should be helpful for identification of cyprid species.

To evaluate the effects of sex steroids on silvering in the Japanese eel, Anguilla japonica, the development of oocytes, eye size, digestive tract, and swim bladder were studied in relation to observations of the profiles of plasma levels of sex steroids (estradiol 17ββ, E2; testosterone, T; 11-ketotestosterone; 11-KT) during silvering for each sex and by administrating 11-KT to yellow eels. All steroids examined in the study increased in female eels after silvering had begun, whereas in males, only 11-KT increased significantly, and no statistical differences were found in plasma levels of E2 and T between eels in both developmental stages. 11-KT appeared to induce the early stage of oocyte growth, enlargement of the eyes, degeneration of the digestive tract and the development of the swim bladder. This suggested that 11-KT synchronously accelerates early development of the ovaries and the morphological changes, possibly in adaption to oceanic migration, and that 11-KT is one of the most important factors in early stages of development in the Japanese eel, as it appears to be in other anguillid eels.

To evaluate the effects of sex steroids on silvering in the Japanese eel, Anguilla japonica, the development of oocytes, eye size, digestive tract, and swim bladder were studied in relation to observations of the profiles of plasma levels of sex steroids (estradiol 17ββ, E2; testosterone, T; 11-ketotestosterone; 11-KT) during silvering for each sex and by administrating 11-KT to yellow eels. All steroids examined in the study increased in female eels after silvering had begun, whereas in males, only 11-KT increased significantly, and no statistical differences were found in plasma levels of E2 and T between eels in both developmental stages. 11-KT appeared to induce the early stage of oocyte growth, enlargement of the eyes, degeneration of the digestive tract and the development of the swim bladder. This suggested that 11-KT synchronously accelerates early development of the ovaries and the morphological changes, possibly in adaption to oceanic migration, and that 11-KT is one of the most important factors in early stages of development in the Japanese eel, as it appears to be in other anguillid eels.

The vivid coloration of corals depends on fluorescent proteins that include cyan (CFP), green (GFP) and red (RFP) fluorescent proteins, and a non-fluorescent blue/purple chromoprotein. We examined how many genes encoding fluorescent proteins are present in the recently sequenced genome of the coral Acropora digitifera. Based on molecular phylogenetic analysis, we found one, five, one, and three candidate genes for CFP, GFP, RFP, and chromoprotein, respectively. The CFP and GFP genes are clustered in a ∼80-kb-long genomic region, suggesting that they originated from an ancestral gene by tandem duplication. Since CFP and GFP possess the same chromophore, the gene clustering may provide the first genomic evidence for a common origin of the two proteins. Comparison between the fluorescent protein genes of closely related coral species suggests an expansion of chromoprotein genes in the A. digitifera genome, and of RFP genes in the A. millepora genome. The A. digitifera fluorescent protein genes are expressed during embryonic and larval developmental stages and in adults, suggesting that the genes play a variety of roles in coral physiology.

The vivid coloration of corals depends on fluorescent proteins that include cyan (CFP), green (GFP) and red (RFP) fluorescent proteins, and a non-fluorescent blue/purple chromoprotein. We examined how many genes encoding fluorescent proteins are present in the recently sequenced genome of the coral Acropora digitifera. Based on molecular phylogenetic analysis, we found one, five, one, and three candidate genes for CFP, GFP, RFP, and chromoprotein, respectively. The CFP and GFP genes are clustered in a ∼80-kb-long genomic region, suggesting that they originated from an ancestral gene by tandem duplication. Since CFP and GFP possess the same chromophore, the gene clustering may provide the first genomic evidence for a common origin of the two proteins. Comparison between the fluorescent protein genes of closely related coral species suggests an expansion of chromoprotein genes in the A. digitifera genome, and of RFP genes in the A. millepora genome. The A. digitifera fluorescent protein genes are expressed during embryonic and larval developmental stages and in adults, suggesting that the genes play a variety of roles in coral physiology.

In certain planarian species that are able to switch between asexual and sexual reproduction, determining whether a sexual has the ability to switch to the asexual state is problematic, which renders the definition of sexuals controversial. We experimentally show the existence of two sexual races, acquired and innate, in the planarian Dugesia ryukyuensis. Acquired sexuals used in this study were experimentally switched from asexuals. Inbreeding of acquired sexuals produced both innate sexuals and asexuals, but inbreeding of innate sexuals produced innate sexuals only and no asexuals. Acquired sexuals, but not innate sexuals, were forced to become asexuals by ablation and regeneration (asexual induction). This suggests that acquired sexuals somehow retain asexual potential, while innate sexuals do not. We also found that acquired sexuals have the potential to develop hyperplastic and supernumerary ovaries, while innate sexuals do not. In this regard, acquired sexuals were more prolific than innate sexuals. The differences between acquired and innate sexuals will provide a structure for examining the mechanism underlying asexual and sexual reproduction in planarians.

We investigated levels of plasma progesterone (P4), 17ββ-estradiol (E2), testosterone (T), and corticosterone (CORT) during gestation and post-birth periods in wild-collected female copperhead snakes (Viperidae; Agkistrodon contortrix). We also sought to determine whether CORT levels at (or near) birth dramatically increase and were correlated with duration of labor and litter size. Specifically, pregnant subjects (N = 14) were collected during early- to mid-gestation, held in the laboratory, and repeatedly bled to obtain plasma for steroid analyses. Progesterone showed significant changes during gestation, with the highest levels at the onset of sampling (circa 50 days prior to birth); P4 progressively declined up to parturition, and basal levels were observed thereafter. At the onset of sampling, E2 was at peak levels and fell sharply at circa 30 days prior to birth, a trend observed throughout the post-birth sampling period. Throughout the entire sampling period, T was undetectable. Although CORT showed no significant changes during gestation and several days following parturition, there was a highly significant peak at the time of birth. Our findings mirror the results of previous studies on pregnancy and steroid hormones of other live-bearing snakes, lizards, and mammals. As expected, there was a significant relationship between duration of labor and litter size; however, although levels of CORT did not achieve significance, there was a positive trend with litter size. We suggest that elevation of CORT at birth is involved in the mobilization and regulation of energy stores necessary for the physiological process of parturition and as a possible mechanism to trigger birth.

We investigated levels of plasma progesterone (P4), 17ββ-estradiol (E2), testosterone (T), and corticosterone (CORT) during gestation and post-birth periods in wild-collected female copperhead snakes (Viperidae; Agkistrodon contortrix). We also sought to determine whether CORT levels at (or near) birth dramatically increase and were correlated with duration of labor and litter size. Specifically, pregnant subjects (N = 14) were collected during early- to mid-gestation, held in the laboratory, and repeatedly bled to obtain plasma for steroid analyses. Progesterone showed significant changes during gestation, with the highest levels at the onset of sampling (circa 50 days prior to birth); P4 progressively declined up to parturition, and basal levels were observed thereafter. At the onset of sampling, E2 was at peak levels and fell sharply at circa 30 days prior to birth, a trend observed throughout the post-birth sampling period. Throughout the entire sampling period, T was undetectable. Although CORT showed no significant changes during gestation and several days following parturition, there was a highly significant peak at the time of birth. Our findings mirror the results of previous studies on pregnancy and steroid hormones of other live-bearing snakes, lizards, and mammals. As expected, there was a significant relationship between duration of labor and litter size; however, although levels of CORT did not achieve significance, there was a positive trend with litter size. We suggest that elevation of CORT at birth is involved in the mobilization and regulation of energy stores necessary for the physiological process of parturition and as a possible mechanism to trigger birth.