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The African clawed frog Xenopus laevis is a largely aquatic frog occurring from central to southern Africa. This species has been used as experimental animal, and has been introduced in many countries including Japan. However, despite its importance as an experimental animal and invasive alien species across the world, but there are few studies on basic biology of X. laevis including individual variation. In this study, we investigated individual variation in external morphology and allometric patterns. Traits not directly related to the skeleton showed high variability, but ecologically important traits like eye size at the youngest stage, showed low variability. No significant external left-right differences were identified. Allometric analysis showed that males have larger heads and eyes than females, suggesting male-male combat during breeding. Male forelimb suggests also showed a faster growth rate, suggesting that longer forelimbs are advantageous for males in breeding. [ABSTRACT FROM AUTHOR]

Gloydius blomhoffii is a common pitviper distributed throughout Japan except for Okinawa Prefecture. To understand intraspecific geographic variation of this widely distributed snake, I describe several of its basic ecological traits observed during a 31-year-field survey conducted in the forest of Ashiu, northeastern Kyoto, in the western region of the mainland of Japan, and compare these traits with those reported in previous studies conducted in widespread areas of Japan. Body length of G. blomhoffii in Kyoto was smaller than that in the northernmost range and larger than that in the southernmost range. Sexual size dimorphism in snout-vent length, tail length, and body mass showed the same trends as in other areas. The sex ratio of the collected snakes was biased to females, which has not been observed in other studies. Pregnant females showed higher body temperature than males and non-pregnant females at a given air temperature. Parturition period, litter size, and body size of neonates generally overlapped with those reported in previous studies. Stomach contents were found only in 9.1% of snakes and consisted of rodents, frogs, and newts, which are prey items already known in G. blomhoffii. Although the forest in Ashiu has been incurred drastic environmental degradation, no obvious change in body size was detected over the study period. This study adds information on ecological traits of G. blomhoffii based on a population-level study and will facilitate future intensive field research to understand this common, but still poorly investigated, venomous snake endemic to Japan. [ABSTRACT FROM AUTHOR]

The family Vitrinellidae is a group of tiny marine snails that generally occur in shallow waters of temperate and tropical seas. The biology of most vitrinellid species remains poorly understood. In this study, we report that Circulus cinguliferus (A. Adams, 1850) (Vitrinellidae), distributed widely in the warm shallow waters of the Pacific, inhabit crustacean burrows, including those of the mud shrimp Neaxius acanthus (Strahlaxiidae) and snapping shrimp Alpheus rapax (Alpheidae), in the intertidal and subtidal flats of the Okinawa Islands, southern Japan. They exhibited highly clumped distribution among the host burrows, suggesting that they are attracted by conspecifics. Although the biology of most Circulus species remains unknown, Circulus texanus (D. R. Moore, 1965) is known to inhabit stomatopod burrows in the western Atlantic. Our findings suggest that such a commensal habit may be more widespread in this genus than previously thought. [ABSTRACT FROM AUTHOR]

The slider turtle (Trachemys scripta Thunberg in Schoepff, 1792) is native to the USA and Mexico. Due to the popularity of their colorful hatchlings as pets, they have been exported worldwide and are now present on all continents, except Antarctica. Slider turtles are well-established in Japan and occupy aquatic habitats in urban and agricultural areas, to the detriment of native turtles with which they compete. We asked the overall question, do slider turtles in Japan have a performance advantage because they are liberated from the numerous competing turtle species in their native range and released from many of their natural predators? Traits compared included various measures of adult body size (mean, maximum), female size at maturity as measured by size of gravid females, clutch size, population density and biomass, sex ratio, and sexual size dimorphism, the latter two a partial reflection of growth and maturity differences between the sexes. We sampled slider turtle populations in three habitats in Japan and compared population attributes with published data for the species from throughout its native range in the USA. Mean male body sizes were at the lower end of values from the USA suggesting that males in Japan may mature at smaller body sizes. The smallest gravid females in Japan mature at smaller body sizes but have mean clutch sizes larger than some populations in the USA. Compared to most populations in the USA, slider turtles achieve higher densities and biomasses in Japanese wetlands, especially the lotic system we sampled. Sex ratios were female-biased, the opposite of what is reported for many populations in protected areas of the USA. Sexual size dimorphism was enhanced relative to native populations with females as the larger sex. The enhanced dimorphism is likely a result of earlier size of maturity in Japanese males and the large size of mature (gravid) Japanese females. Slider turtles appear to have a performance advantage over native turtles in Japan, possibly as a result of being released from competition with numerous sympatric turtle species in their native range, and the absence of many co-evolved predators and parasites in Japan. This slight competitive edge, coupled with the catholic diet and broad tolerance of varying aquatic habitats of slider turtles, is reflected in their dominance over native and naturalized Japanese turtles in altered aquatic habitats. [ABSTRACT FROM AUTHOR]