Current Herpetology

We investigated the effect of incubation temperature on hatchling sex in the Japanese pond turtle, Mauremys japonica. Eggs obtained from females collected in the Tokai District of Japan invariably produced males when incubated at constant temperatures from 22.0 to 28.0 C, whereas they produced only females under a higher temperature of 30.0 C. Both males and females hatched from eggs incubated at 28.5, 29.0, and 29.5 C. These results indicate that M. japonica has a mechanism of temperature-dependent sex determination (TSD) with higher temperatures favoring females and lower temperatures males as in several other species of the family Geoemydidae, as well as of a few other testudine families so far studied. The pivotal temperature and the transitional range of temperature (TRT) in M. japonica obtained by the inverse estimation from logistic regression were 28.8 C and from 27.8–29.8 C, respectively. Possible effect of TSD on the sex ratio observed in some wild populations of this turtle is discussed.

Genetic variation was examined for the endangered banded newts Triturus vittatus vittatus from a number of breeding sites in northern and central Israel near the southern limit of the species' distribution. Altitudes of the sites ranged from 15–740 m asl. Variations in nucleotide sequences of the mitochondrial cytochrome b gene (413-bp-long) and the control region (Dloop) (569-bp-long) were analyzed, of which the former varied at 13 nucleotide sites whereas the latter at 15 sites. Specimens from Berekhya pond, which is located at the lowest altitude, most distant from the other sites, and with the least annual precipitation, were found to be most divergent due to accumulation of anagenetic sequence changes. Sequence analysis showed that the newts from Israel are genetically collectively different from conspecific populations of Syria (Damascus) and Turkey (European part). DNA variation might have possibly been enhanced by differences in ecological conditions that are seemingly most prominent in habitats near the southern limit of the species' distribution.

The body size and age structure of a breeding population of the Japanese common toad, Bufo japonicus formosus, was studied at Yamakitamachi in Kanagawa Prefecture for three breeding seasons from 1992 to 1994. Yearly variation in snout-vent length (SVL) was not significant, but the difference in SVL between the sexes was highly significant; the mean SVL of males and females was 125.8 and 134.2 mm, respectively. The breeding adults were aged successfully by skeletochronology using phalanges. The breeding adults were 1-8 yr old. The mean and median ages were 4.5 and 4 yr in males, and 5.2 and 5 yr in females, respectively. The males were estimated to begin to breed when one to four yr old, with a mean of 2.4 yr, while the females were estimated to breed when two to four yr old, with a mean of 2.7 yr. Age at first reproduction was significantly younger for males than females. We discuss the sexual size dimorphism of B. j. formosus in relation to the difference in age structure of the breeding population between the sexes clarified by skeletochronology.

The nomen Rana ulukalensis, occupied by Nakatani (1969) for a frog collected from the foot of “Mount Ulu Kali”, situated at the headwaters of Batang Kali, a river NNE of Kuala Lumpur, Malaysia, is shown to be a subjective junior synonym of Rana tweediei Smith, 1935, whose currently valid name is Limnonectes tweediei (Smith, 1935).

Unfertilized eggs of Lepidochelys olivacea were examined for elemental composition and structure of the eggshell and mineral contents of the yolk-albumen fraction. Calcium was the major inorganic component both in the eggshell and egg contents. Other elements were present in traces. Scanning electron microscopic study revealed that the eggshell had two layers: an outer calcareous matrix in its aragonite morph and a membrane layer with fibres. The calcareous layer was made up of loosely and irregularly arranged 10–40 µm wide nodular shell units. The shell thickness was 125 to 150 µm. The membrane fibres were less dense, less netted than their normal counterparts and of variable thickness. The composition and structure of unfertilized eggshell were more or less similar to those reported for their normal counterparts except for the arrangement of fibres in the membrane layer.