Ecological information on the golden venus chub (Hemigrammocypris rasborella Fowler, 1910) was collected during field surveys and used to analyze habitat use by this species at each growth stage. Surveys were conducted every month for approximately 2 years in an irrigation ditch near the Ushizu River, Kyushu Island, Japan. Based on the characteristic nuptial coloration of males, it was estimated that H. rasborella spawns between spring and summer. Size measurements of 2697 individuals indicated two size classes. The population of age class 1 decreased rapidly after the spawning period. On the basis of growth patterns, the life cycle of H. rasborella was classified into three stages: the growth stage (GS) of age class 0 fish from August to November, the no-growth stage (NGS) of age class 0 fish from December to March, and the growing and spawning stage (GSS) of age class 0 and 1 fish from April to August. Habitat use by GS, NGS, and GSS fish was analyzed with a stepwise multiple linear regression. The average number of fish was negatively correlated with the presence of a concrete revetment in the GS; positively and negatively correlated with minimum water depth and submerged plants, respectively, in the NGS; and positively correlated with maximum water temperature in the GSS. These results suggest that maintenance of the water level in the fallow season and not using concrete revetments are essential for the conservation of this species under the present conditions in Japanese rice fields.

The ability of JHIII and three JHAs (hydroprene, pyriproxyfen and methoprene) to induce presoldier differentiation was tested in a highly derived termite, Nasutitermes takasagoensis (Isoptera: Nasutitermitinae), and induced presoldiers were examined morphologically and histologically. Hydroprene was the most effective hormone analog for the artificial induction of presoldier differentiation. Principal component analysis showed that hydroprene-induced presoldiers had similar external gross morphology to natural presoldiers found in the same colony. Induced presoldiers had a long, horn-like frontal projection, called a nasus, on the head. A well-developed reservoir and duct of the frontal gland were also observed inside the head. Scanning electron micrographs showed that the precursory structure forming the nasus (nasus disc) was developed under the cuticle of hydroprene-treated individuals just prior to the molt into presoldiers. Morphological changes in presoldier differentiation induced by hydroprene seemed to occur normally, compared with those in natural presoldiers. Thus, the present methods shown in this study will provide opportunities to conduct further molecular analyses on the molecular developmental bases of nasus formation during soldier differentiation in higher termites.

Isoforms of myosin heavy chain and tropomyosin convert during metamorphosis of Xenopus laevis with larval-to-adult remodeling of dorsal muscle (Nishikawa and Hayashi, 1994, Dev. Biol. 165: 86–94). In the present study, other markers for muscle remodeling during metamorphosis were determined by SDS-PAGE analysis. The amounts of twelve muscle proteins changed remarkably during metamorphosis. Among these, a 54-kDa molecule was found to be desmin, and the relative content/total proteins decreased dramatically through metamorphosis. In hindlimb muscle, desmin content increased fourfold during prometamorphosis, when myoblast proliferation and fusion occurred. With further myotube maturation, this content decreased by 1/2 while that of muscle actin continued to increase. Thus, desmin up- and down-regulation in hindlimbs mark early and late phases of myogenesis, respectively. In tail muscle, the desmin content decreased continuously to 1/8 before and during metamorphosis, due to tail muscle growth and maturation. In dorsal muscle, three desmin changes occurred: a pre-metamorphic decrease, a transient increase at prometamorphosis, and a rapid decrease at the climax stage. Immunohistochemical analysis showed desmin cells to be present between young (adult-type) myotubes and replicating (PCNA ) cells in dorsal muscles, correlating the transient desmin upregulation in dorsal muscle with the initiation of adult-type myogenesis. After the upregulation, dorsal muscle desmin decreased to 1/8. This rapid down-regulation was replicated by administration of triiodothyronine (T₃) to tadpoles, suggesting a significant role for T₃ in dorsal muscle remodeling during metamorphosis. Collectively, these results show that analysis of desmin expression and PCNA-immunohistochemistry are good tools for determining the sites and timing of larval-to-adult muscle remodeling during Xenopus laevis metamorphosis.

Neurogenic placodes, a chordate innovation, generate several neuronal populations, including gonadotropin-releasing hormone (GnRH) neurons which are crucial for vertebrate and solitary ascidian urochordate reproduction. The dorsal strand placode of ascidians is derived from the anterior ridge of the embryonic neural plate and thus shares a common developmental origin and expression of various transcription factors with vertebrate placodes. Despite their importance for understanding vertebrate origins, the evolutionary and developmental origins of the neurogenic placode remain obscure. Here I demonstrate the formation of an elaborate neurogenic placode, which forms the dorsal strand, on part of the neural gland epithelium in a solitary ascidian urochordate, Halocynthia roretzi. Two modes of GnRH neurogenesis in the dorsal strand (a peripheral organ) and the migration of GnRH neurons into the brain along the visceral nerve are also described. Ontogenetically, GnRH neurons are first detected in the dorsal strand and cerebral ganglion of very young juveniles at almost the same time, demonstrating that ascidians possess morphological and developmental features in common with vertebrates. These results further indicate that the onset of peripheral GnRH neurogenesis and the ability of neurons to migrate into the brain predate the divergence of ascidians and vertebrates. Thus, based on the generation of GnRH neurons, the dorsal strand in ascidians may be homologous to the vertebrate olfactory placode. These organs are derived from the anterior region of the embryonic neural plate, which expresses several transcription factors that invertebrate chordates and vertebrates have in common. These results provide unequivocal support for the clade Olfactores (tunicates vertebrates).

Stalked crinoids are recognized as living fossils that typically inhabit modern deep-water environments exceeding 100 m. Previous records of stalked crinoids from hadal depths (exceeding 6000 m) are extremely rare, and no in-situ information has been available. We show here that stalked crinoids live densely on rocky substrates at depths over 9000 m in the Izu-Ogasawara Trench off the eastern coast of Japan, evidenced by underwater photos and videos taken by a remotely operated vehicle. This is the deepest in-situ observation of stalked crinoids and demonstrates that crinoid meadows can exist at hadal depths close to the deepest ocean floor, in a fashion quite similar to populations observed in shallower depths.

The cystine-knot glycoprotein hormone α (GPA) family regulates gonadal and thyroid functions in vertebrates. Little is known concerning GPA family members in primitive chordates. A previous genomic analysis revealed the presence of two genes homologous to the thyrostimulin α subunit (GPA2) in an amphioxus (Branchiostoma floridae); however only one GPA2 homolog contained both the cystine-knot structure and N-glycosylation site characteristic of family members. Gene-specific PCR was used to obtain the cDNA and genomic sequences of the GPA2 homolog of the amphioxus Branchiostoma belcheri. Whole-mount in situ hybridization revealed GPA2 mRNA expression in the anterior part of the nerve cord and on the left side of the central canal. Because amphioxus possesses only one true GPA2 homolog, while vertebrates possess two glycoprotein hormone α subunits (thyrostimulin α, or GPA2, and the common α subunit of gonadal and thyroid glycoprotein hormones, GPA1), our results suggest that GPA1 was acquired later in the vertebrate lineage through gene duplication.

Pea aphids form a mutualistic association with the endosymbiotic bacterium Buchnera, which is harbored in specialized host cells called bacteriocytes. The adult aphids display dimorphism in which there are winged and wingless morphs. We previously reported that the Buchnera density in bacteriocytes of the winged morph (alate) decreases around final ecdysis, whereas that in the wingless morph (aptera) does not decrease; the decrease in density in alatae is accompanied by activation of the host lysosomal system and by Buchnera degradation. In the present study, we performed a proteomic analysis to clarify the molecular mechanisms underlying the decrease in Buchnera density. By comparing the protein expression profiles of bacteriocytes in alatae and apterae just after final ecdysis, we identified three and one protein spots that were preferentially expressed in alatae and apterae, respectively. Among the three alate-preferential spots, two were an identical aphid protein, carboxypeptidase vitellogenic-like (CPVL), whereas the other was a mixture of four proteins: γ-glutamyl hydrolase, acyl-CoA dehydrogenase, aphid short chain acyl-CoA dehydrogenase, and Buchnera S-adenosylmethionine synthetase. The aptera-preferential spot was Buchnera outer membrane protein A. Immunoblot and immunohistochemical analyses using aphid bacteriocytes just after final ecdysis revealed that expression of aphid CPVL was preferentially upregulated in alatae and was localized around Buchnera cells in the bacteriocytes, suggesting the involvement of CPVL in Buchnera degradation in alatae.

From mid-December to late January, schools of mature gray mullet (Mugil cephalus) migrate southward along the coastal waters of China to Taiwan for spawning. It has been proposed that there is no genetic differentiation of gray mullet in the coastal waters of Taiwan. To test this hypothesis, complete cytochrome b (cyt b) DNA sequences of 98 individuals of gray mullet, two individuals of Liza macrolepis, and three individuals of L. affinis were amplified by polymerase chain reaction and sequenced. Phylogenetic trees reconstructed with the Bayesian, maximum likelihood, maximum parsimony, and neighbor-joining methods all support the existence of three monophyletic groups (denoted as groups 1, 2, and 3), with net evolutionary divergences (p-distances) between groups ranging from 5.1% to 6.6%. To estimate the relative abundance of each group, a PCR-RFLP method was developed to examine 600 juveniles collected from October 2006 to March 2007. Groups 1, 2, and 3 comprised 85%, 3%, and 12% of the samples, respectively. Juveniles of groups 1 and 3 could be found as early as November, but juveniles of group 2 were not found until February. Based on the dates of specimen collection and phylogenetic analyses, we propose that groups 1 and 2 are migratory populations from China and Japan, respectively, whereas group 3 is a resident population in Taiwan.

The genes Tektin A1 and axonemal protein 66.0 were successfully isolated and characterized in the tropical abalone Haliotis asinina. The full-length cDNAs of Ha-TekA1 and Ha-Axp66.0 were 2166 and 2038 bp long, with ORFs of 1350 and 1683 bp, respectively. Both Ha-TekA1 and Ha-Axp66.0 were expressed in the testes but not in the ovaries or hemocytes of H. asinina adults. In addition, HaAxp66.0 was not expressed in H. asinina juveniles (2, 3, and 5 months old). A tissue expression analysis showed Ha-Axp66.0 to be expressed specifically in the testes, whereas Ha-TekA1 was expressed abundantly in the testes but weakly in the foot, gill, digestive gland, left hypobranchial gland, and mantle. The relative expression levels of Ha-TekA1 and Ha-Axp66.0 were significantly lower in undeveloped testes (stage I) than in developed testes (stages II, III, and IV) of H. asinina (P<0.05).

A new species in the rhacophorid genus Philautus is described on the basis of five male specimens collected from the Matang Range, a herpetologically well-surveyed area of the lowland of Sarawak, western Borneo. The species possesses a cutaneus pectoris muscle but lacks vomerine teeth, and is assigned to the aurifasciatus group of Philautus. It is superficially similar to some other species of the same group, but can be differentiated from them by a combination of several morphological characters, including lack of a nuptial pad and lingual papilla, and more significantly, by a distinct advertisement call. This discovery underscores the immediate necessity for detailed surveys in the already well-explored lowlands of Borneo.