Fertilization is a significant event for reproducing offspring. It is achieved under a species-specific environment, which influences the conditions to assure the successful fertilization in some cases. Several studies about the basic mechanism of fertilization suggest that the fertilization mechanism is modified among species to be suited for the fertilization environment.

In amphibians, many anurans undergo external fertilization while most urodeles do internal fertilization. An amphibian egg is surrounded by egg-coats, which are composed of vitelline envelope and layered egg-jelly. They are significant as fields for the sperm-egg interaction at fertilization. The fertilization processes that take place in the egg-coats are supposed to be easily influenced by the fertilization environment, because they, especially egg-jelly, are exposed to the surroundings at fertilization. In the present article, we describe the fertilization system equipped in newt egg-coats. Newt sperm are stored in spermatheca that exists in cloaca of a female and directly inseminated on the surface of egg-jelly. Sperm motility and acrosome reaction are induced in the outermost portion of the egg-jelly. Motion of the moving sperm becomes vigorous in the egg-jelly and sperm are guided to vitelline envelope by the aid of egg-jelly structure. Most of the sperm passing through the egg-jelly, as the result, has been induced acrosome reaction and those sperm can bind to the vitelline envelope to contribute to the successful fertilization. This fertilization system has a distinct feature from the known system in species undergoing external fertilization. The feature of the system in the newt egg-jelly is discussed with the view to achieving the successful fertilization in the internal environment.

We describe an efficient protocol for mapping genes and other DNA sequences to amphioxus chromosomes using fluorescent in situ hybridisation. We apply this method to identify the number and location of ribosomal DNA gene clusters and telomere sequences in metaphase spreads of Branchiostoma floridae. We also describe how the locations of two single copy genes can be mapped relative to each other, and demonstrate this by mapping an amphioxus Pax gene relative to a homologue of the Notch gene. These methods have great potential for performing comparative genomics between amphioxus and vertebrates.

We established three transgenic medaka fish lines overexpressing the medaka estrogen receptor under the constitutive medaka β-actin promoter. The transgenic embryos became hypersensitive to estrogens (17β-estradiol and 17α-ethinylestradiol), and failed to develop yolk veins while blood clots formed in the blood island within 3 days after exposure to the estrogens. The embryos developed normally if exposed to estrogen after an early neurula stage, suggesting that the sensitive stage is before neurulation. The developmental defects were recovered by incubation with an anti-estrogen, tamoxifen. These results indicate that activation of estrogen receptor caused the estrogen-induced developmental defects. Our results show that the transgenic embryos can be used to assay the blood clotting activity of estrogenic compounds in vivo.

Metacaligus latus n. sp. (Copepoda, Caligidae) is described from specimens found parasitic in the oral and gill cavities of the cutlassfish, Trichiurus lepturus Linnaeus, caught from the Strait of Taiwan and landed at Dong-Shih Fishing Port in Chiayi County, Taiwan. It is close to M. uruguayensis (Thomsen, 1949), but can be distinguished from the latter by the possession of shorter caudal rami in both sexes and wider cephalothorax and genital complex in the male. Cladistic (phylogenetic) analysis of the Family Caligidae, based on 23 selected morphological characters, revealed that Metacaligus Thomsen, 1949 is distantly related to Caligus Müller, 1758. It is a valid genus and occurs in sister-group relationship with Apogonia Cressey and Cressey, 1990.

Morphological differences are investigated using several culture strains of three sibling species collected from Taiwan and Guangdong in China and Pyinoolwin and Yangon in Myanmar. Careful examination of male terminalia reveals distinguishable differences in the paramere and the aedeagal basal process among the three species. In addition, a number of quantitative characters are compared. Kruskal-Wallis tests with Bonferroni correction, which are carried out separately for each sex, detect significant differences in 15 characters, of which two are male-specific, among the three species. Canonical discriminant analysis using these characters reveals that the three species can be distinguished from each other with high confidence for both sexes. The results clearly show the presence of three good species, Drosophila (Sophophora) lini Bock & Wheeler, 1972 and its two new siblings. The new species are described as Drosophila (Sophophora) ohnishii sp. nov. from Pyinoolwin and Drosophila (Sophophora) ogumai sp. nov. from Yangon. The morphological differentiation among the three sibling species does not coincide with the degree of reproductive isolation (based on a previous study). The premating isolation pattern suggests two possibilities that premating isolation has been evolved or reinforced in sympatric populations between D. ohnishii and D. lini and between D. ohnishii and D. ogumai or that it has evolved in a very restricted local population of D. ohnishii, possibly by a few mutations.