The mode of hatching in birds has important impacts on both parents and chicks, including the costs and risks of breeding for parents, and sibling competition in a clutch. Birds with multiple eggs in a single clutch often begin incubating when most eggs are laid, thereby reducing time of incubation, nursing burden, and sibling competition. In some songbirds and some other species, however, incubation starts immediately after the first egg is laid, and the chicks thus hatch asynchronously. This may result in differences in parental care and in sibling competition based on body size differences among older and younger chicks, which in turn might produce asynchronous development among siblings favoring the first hatchling, and further affect the development and fitness of the chicks after fledging. To determine whether such processes in fact occur in the zebra finch, we observed chick development in 18 clutches of zebra finches. We found that there were effects of asynchronous hatching, but these were smaller than expected and mostly not significant. Our observations suggest that the amount of care given to each chick may be equated with such factors as a camouflage effect of the down feathers, and that the low illumination within the nest also complicates the determination of the hatching order by the parents.

Pleuronectiform fish develop marked external asymmetry in eye location and skin color at metamorphosis. The bamboo sole, Heteromycteris japonica, also exhibits loss of the pectoral fins at metamorphosis. Because of its small body size, short generation time, and long spawning season, we focused on the bamboo sole as an experimental model to investigate metamorphic asymmetry and pectoral fin loss during development. In the present study, we utilized a small-scale culture system to evaluate bamboo sole larvae and larval development, and a microinjection system for fertilized eggs. The culture system described here uses an 18 L culture tank for rotifers (the first diet for larvae) and 5 L plastic beakers for larval culture. Under this system, most larvae completed metamorphosis, including one-eye migration and pigmentation of the ocular side, by 23 days postfertilization (dpf) at 25°C. Larvae at density of 120–150 per liter were grown from hatching to 23 dpf with a survival ratio of 60–75% per beaker. Pectoral fins, including coracoid and disk cartilage, formed but were completely lost in late metamorphosis without formation of proximal radials and fin rays. The microinjection system designed here is adequate for the bamboo sole and allows injection of 100 one-cell-stage embryos per day. We expect that the culture and microinjection systems described here will facilitate the use of the bamboo sole as an experimental model organism in developmental biology.

In an attempt to establish an experimental dragonfly model, we developed a laboratory rearing system for the blue-tailed damselfly, Ischnura senegalensis. Adoption of multi-well plastic plates as rearing containers enabled mass-rearing of isolated larvae without cannibalism and convenient microscopic monitoring of individual larvae. Feeding Artemia brine shrimps to younger larvae and Tubifex worms for older larvae resulted in low mortality, synchronized ecdysis, and normal development of the larvae. We continuously monitored the development of 118 larvae every day, of which 49 individuals (41.5%) reached adulthood. The adult insects were fed with Drosophila flies in wet plastic cages, attained reproductive maturity in a week, copulated, laid fertilized eggs, and produced progeny. The final larval instar varied from 9^th to 12^th, with the 11^th instar (56.5%) and the 12^th instar (24.2%) constituting the majority. From the 1^st instar to the penultimate instar, the duration of each instar was relatively short, mainly ranging from three to 11 days. Afterwards, the duration of each instar was prolonged, reaching 7–25 days for the penultimate instar and 14–28 days for the final instar. Some larvae of final, penultimate and younger instars were subjected to continuous and close morphological examinations, which enabled developmental staging of larvae based on size, shape, and angle of compound eyes and other morphological traits. This laboratory rearing system may facilitate the understanding of physiological, biochemical, and molecular mechanisms underlying metamorphosis, hormonal control, morphogenesis, body color polymorphism, and other biological features of dragonflies.

Juvenile hormone (JH) plays important roles in insect development and physiology. JH titer is tightly regulated to coordinately adjust systemic physiology and development. Although control of JH titer is explained by the expression of JH biosynthetic enzymes in the corpora allata (CA), molecular mechanisms that regulate the expression of these genes remain elusive. In the present study, to identify novel regulators of JH biosynthetic genes, we conducted a gene expression screen using the CA and corpora cardiaca (CC) of the silkworm, Bombyx mori, in the JH synthesis period. We identified seven candidate genes and characterized their properties through extensive expression analyses. Of these candidates, we found that a novel gene, which encodes type II phosphatidylinositol 3,4-bisphosphate [PI(3,4)P₂] 4-phosphatase, shows highly correlated expression with JH titer. In addition, expression of this gene was strongly upregulated by starvation, when JH biosynthetic enzyme genes are concurrently upregulated. These results, for the first time, imply possible involvement of phosphoinositol signal in regulation of JH biosynthesis, providing novel insights into molecular mechanisms of nutrition-dependent regulation of JH biosynthesis.

The deep-sea crangonid shrimp, Argis lar, is a highly abundant species from the northern Pacific Ocean. We investigated its phylogeographic and demographic structure across the species' extensive range, using mitochondrial DNA sequence variation to evaluate the impact of deep-sea paleoenvironmental dynamics in the Sea of Japan on population histories. The haplotype network detected three distinct lineages with allopatric isolation, which roughly corresponded to the Sea of Japan (Lineage A), the northwestern Pacific off the Japanese Archipelago (Lineage B), and the Bering Sea/Gulf of Alaska (Lineage C). Lineage A showed relatively low haplotype and nucleotide diversity, a significantly negative value of Tajima's D, and a star-shaped network, suggesting that anoxic bottom-water in the Sea of Japan over the last glacial period may have brought about a reduction in the Sea of Japan population. Furthermore, unexpectedly, the distributions of Lineage A and B were closely related to the pathways of the two ocean currents, especially along the Sanriku Coast. This result indicated that A. lar could disperse across shallow straits through the ocean current, despite their deep-sea adult habitat. Bayesian inference of divergence time revealed that A. lar separated into three lineages approximately 1 million years before present (BP) in the Pleistocene, and then had been influenced by deep-sea paleoenvironmental change in the Sea of Japan during the last glacial period, followed by a more recent larval dispersal with the ocean current since ca. 6 kilo years BP.

Tail regression in amphibian tadpoles during metamorphosis is one of the most dynamic morphological changes in animal development and is induced by thyroid hormone (TH). It has been proposed that tail resorption is driven by immunological rejection in Xenopus laevis, based on experimental evidence showing that larval skin grafts become atrophic on syngenic recipient adult frogs. This led to the hypothesis that tail regression is induced by an immunological rejection against larval skin-specific antigens called Ouro proteins. However, our group has demonstrated that ouro-knockout tadpoles undergo normal metamorphosis, including tail resorption in Xenopus tropicalis, which indicates that the expression of ouro genes is not necessary for tail regression. In the present study, we showed that an inhibitor of TH synthesis promotes the survival of larval tail skin grafts on syngenic adult Xenopus tropicalis frogs. The levels of endogenous THs in adult frogs were also comparable to those in metamorphosing tadpoles of Xenopus laevis with a regressing tail, and TH induced the regression of tadpole tail tips of Xenopus tropicalis in organ culture. Taken together, these results strongly suggest that endogenous THs in the recipient adult frog induce the degeneration of syngenic tail skin grafts.

Telomerase reverse transcriptase (TERT), a catalytic subunit of telomerase, plays a key role in the activity and biological functions of telomerase. In the present study we isolated and characterized the full-length cDNA and DNA sequences of the TERT gene (MeTERT) from Metapenaeus ensis. MeTERT cDNA was 4239 bp in length, which consisted of a 369 bp 5′UTR, a 3231 bp open reading frame encoding 1076 amino acids, and a 639 bp 3′UTR. The genomic DNA of MeTERT had only two introns, similar to beetle (two introns) and silkworm (intronless). The MeTERT protein showed only 5.2–7.9% identity with other known TERTs but contained all the four primary TERT domains of the N-terminal TEN, RNA binding domain (TRBD), reverse transcriptase (RT) and C-terminus CTE. Expression pattern analysis by RT-qPCR showed that, the MeTERT mRNA transcripts could be detected in all the tested samples, with relatively higher expression level in the gill, mysis, Oka organ and egg, but lower level in muscle, ovary, in vitro cultured 3-d Oka organ cells and heart. The significant decrease of MeTERT expression in the in vitro cultured 3-d Oka organ primary cells compared with their source tissue of Oka organ may have contributed to the cellular mitosisarrest. Thus trans-activation of TERT gene may be a candidate in attempts to immortalize in vitro cultured shrimp cells. This work will lay a solid foundation for future studies of the biological functions of telomerase in crustaceans.

We investigated the effect of external and internal osmotic stress on the profile of long-chain polyunsaturated fatty acids (LC-PUFA) in euryhaline eels Anguilla japonica. Freshwater (FW) fish were transferred to seawater (SW) for external osmotic stress or subjected to internal stress through injection with hypertonic saline. FW eels injected with isotonic saline served as controls. Plasma osmolality, Na concentration, and gill Na /K -ATPase activity increased, but hematocrit decreased compared with controls in eels exposed to external or internal osmotic stress. The expression of two major transporter genes for SW adaptation, the Na -K -2Cl - co-transporter 1a (NKCC1a) in the gill and NKCC2b in the intestine, was up-regulated only in SW-transferred eels, suggesting a direct impact of SW on the gill and intestine via SW ingestion. Total LC-PUFA contents and DHA (22:6 n-3) increased in the gill and liver of SW-transferred eels and in the intestine of hypertonic saline-injected eels. However, total LC-PUFA content in plasma decreased after both external and internal osmotic stimuli. In contrast, the gene expression of two key enzymes involved in the LC-PUFA biosynthesis, Δ6 fatty acid desaturase and elongase, did not change in the gill, intestine and liver of osmotically stressed eels. These results indicate that LC-PUFA is possibly involved in osmoregulation and the increased LC-PUFA contents of osmoregulatory organs might be a result of LC-PUFA transport via circulation, rather than through de novo biosynthesis.

Environmental estrogens such as bisphenol-A (BPA) cause reproductive disorders in many vertebrate species, especially fish. BPA is used extensively in the manufacture of plastic and plastic products, epoxy resins, and dental sealants. The presence of BPA in sewage and surface water raises a potential threat to aquatic populations. In the present study, we investigated the effects of BPA on ovarian histology and transcription of key genes involved in reproduction. Adult female Catla catla were exposed to graded concentrations of BPA (10, 100, 1000 µg/l) for 14 days. Ovary histology and expression of steroidogenic acute regulatory protein (star), ovary aromatase (cyp19a), follicle-stimulating hormone receptor (fshr), and luteinizing hormone receptor (lhr) were evaluated in ovary of female fish after 14 days. Fish ovaries from the control and 10 µg/l BPA exposed groups included primary oocytes (POCs), while fish exposed to higher concentrations of BPA (100 and 1000 µg/l) contained tertiary and mature oocytes with increased numbers of atretic follicles. Significant increases in mRNA transcripts of star were observed in fish exposed to 100 and 1000 µg/l BPA. A 15-fold increase in the expression of ovary aromatase (cyp19a) was detected in fish exposed to 100 µg/l BPA. fshr increased in a dose-dependent manner. Increases in the expression of lhr, although not statistically significant, were observed in fish exposed to 100 and 1000 µg/l BPA when compared to control. The results of the present study indicate that BPA causes alterations in the expression patterns of genes involved in the reproductive pathway, which may lead to negative effects on the reproductive system in female fish.

Previous studies have revealed variations in the urogenital system morphology of amphibians. Recently, the urogenital system of salamanders was reviewed and terminology was synonymized across taxa. Discrepancies exist in the terminology describing the urogenital system of anurans, which prompted our group to develop a complete, detailed description of the urogenital system in an anuran species and provide nomenclature that is synonymous with those of other amphibian taxa. In Rana catesbeiana, sperm mature within spermatocysts of the seminiferous tubule epithelia and are transported to a series of intratesticular ducts that exit the testes and merge to form vasa efferentia. Vasa efferentia converge into single longitudinal ducts (Bidder's ducts) on the lateral aspects of the kidneys. Branches from the longitudinal ducts merge with genital kidney renal tubules through renal corpuscles. The nephrons travel caudally and empty into the Wöffian ducts. Similar to salamanders, the caudal portion of the kidneys (termed the pelvic kidneys in salamanders) only possesses nephrons involved in urine formation, not sperm transport. Data from the present study provide a detailed description and synonymous nomenclature that can be used to make future comparative analyses between taxa more efficient.

Butis butis is a commercially important goby that is widely distributed in Indo-Pacific regions; however, its reproductive biology is poorly characterized. We condcted the present study in estuarine and coastline areas in the Mekong Delta from June 2015 to May 2016 to generate reproductive parameters for this species. The results of data analysis based on a collection of 173 individuals (74 females and 99 males) indicate that the sex ratio of this species is close to 1:1. Mature (stage IV) and ripe (stage V) gonads were found monthly during the study period, suggesting that Butis butis is an iteroparous fish that spawns in a year-round cycle. Male B. butis matures first at 8.97 cm total length (TL), which is longer than females (6.82 cm TL). Butis butis is well adapted to tropical monsoon regions due to its high batch fecundity (46,017 ± 6941 SE), ranging from 15,000 (8.6 cm TL and 5.71 g W) to 78,500 (15.8 cm TL and 42.24 g W) eggs. Batch fecundity increases with fish size due to a strong positive relationship between batch fecundity and fish size (TL and W). These results help fill the knowledge gap on the reproductive biology of Butis butis, and contribute crucial information relevant to sustainable management of fish populations in the study region.