We discovered a new cataract mutation, kfrs4, in the Kyoto Fancy Rat Stock (KFRS) background. Within 1 month of birth, all kfrs4/kfrs4 homozygotes developed cataracts, with severe opacity in the nuclei of the lens. In contrast, no opacity was observed in the kfrs4/+ heterozygotes. We continued to observe these rats until they reached 1 year of age and found that cataractogenesis did not occur in kfrs4/+ rats. To define the histological defects in the lenses of kfrs4 rats, sections of the eyes of these rats were prepared. Although the lenses of kfrs4/kfrs4 homozygotes showed severely disorganised fibres and vacuolation, the lenses of kfrs4/+ heterozygotes appeared normal and similar to those of wild-type rats. We used positional cloning to identify the kfrs4 mutation. The mutation was mapped to an approximately 9.7-Mb region on chromosome 7, which contains the Mip gene. This gene is responsible for a dominant form of cataract in humans and mice. Sequence analysis of the mutant-derived Mip gene identified a 5-bp insertion. This insertion is predicted to inactivate the MIP protein, as it produces a frameshift that results in the synthesis of 6 novel amino acid residues and a truncated protein that lacks 136 amino acids in the C-terminal region, and no MIP immunoreactivity was observed in the lens fibre cells of kfrs4/kfrs4 homozygous rats using an antibody that recognises the C- and N-terminus of MIP. In addition, the kfrs4/+ heterozygotes showed reduced expression of Mip mRNA and MIP protein and the kfrs4/kfrs4 homozygotes showed no expression in the lens. These results indicate that the kfrs4 mutation conveys a loss-of-function, which leads to functional inactivation though the degradation of Mip mRNA by an mRNA decay mechanism. Therefore, the kfrs4 rat represents the first characterised rat model with a recessive mutation in the Mip gene.

Understanding the mechanisms of adaptation of alpine aquatic organisms to the alpine environment, one of the ecosystems most vulnerable to climate change, would help us predict how those organisms would respond to the upcoming climate change. Here, we examined how one of Japan's endemic crustaceans, Daphnia tanakai, which has been found only in alpine lakes and pools in high mountain moors, is adapted to the alpine environment and what restricts its distribution only to the alpine environment. Lab experiments on UVB tolerance and growth rate under different pH and temperature based on the field survey for pools in mountain moors revealed that D. tanakai was differentiated from two low‐altitude species (Daphnia dentifera and Daphnia pulicaria) by its tolerance to low pH such as 4.5, which is equal to the mean pH of pools in the high mountain moors occupied by D. tanakai. The growth rate at pH 4.5 was, however, significantly lower than that at higher pH, suggesting that low pH was not necessarily an optimal condition, and that other factors restrict the distribution to alpine lakes. Vulnerability to invertebrate predators such as Chaoborus was suggested as such a factor by additional experiments on swimming activity and predation and the fact that D. tanakai has only been found in pools without Chaoborus. Because it is known that the pH of alpine lakes is tightly linked with temperature, global warming may diminish the advantage of D. tanakai and allow invasion of alpine lakes by unwelcome predators and competitors from lower altitudes.

Green turtles (Chelonia mydas) are seasonal breeders with a time lag between mating and nesting periods. We therefore investigated whether female turtles store sperm like some other animals by histologically and ultrastructurally analyzing oviducts collected from three mature female free-ranging green turtles during the breeding season in the Ogasawara Islands, Japan. The oviduct comprised an infundibulum, magnum, isthmus, uterus, and vagina. Sperm was found in the isthmus of all turtles examined. Some spermatozoa were found in the duct and acini of glands in the isthmus of two turtles with oviducts containing eggs, and a few were also located in the transition area between the uterus and vagina of one of the turtles. On the other hand, we also found abundant spermatozoa on the luminal surface of the isthmus of one turtle captured during mating. In most reptiles, fertilization occurs in the infundibulum or albumen region, and thus the isthmus near those areas might be suitable for storing sperm in female turtles.

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Coastal dikes were seriously damaged by tsunami of The 2011 off the Pacific coast of Tohoku Earthquake. The main cause of the damage was supposed to be scouring at the back slope toe. In this study, in order to estimate scouring landward of coastal dikes induced by tsunami overflow, a numerical model which introduced a geomorphological process into CADMAS-SURF/2D was developed. Then, the model was verified by comparison with experimental results. As a result, while numerical results may lead to underestimate width of scouring, the calculated maximum scour depth showed good agreement with experimental results. Thus, it was indicated that this model could be applied to estimate scouring at the back slope toe of coastal dikes.