Tsushima Brown Frog

The body of R. tsushimensis is slender. The canthus is blunt and concave. The tympanum is circular, and there are 2-6 vomerine teeth which are oval. There is moderate webbing, where the broad web leaves 1-2 phalanges in males and 2-3 in females free on the outer margin of 4th toe. The inner metatarsal tubercle is elliptical, and the outer one is small but distinct. The skin on the back of the frog is covered with small granules which have asperities on them. The dorsolateral fold is evident, slightly flaring outwards above tympanum, and the supratympanic fold is blunt. The mean snout-vent length of males is 35 mm (range 31-37) and for females, 45 mm (range 37-44). There is no vocal sac or vocal opening, and the nuptial pads in males are grayish brown.The type locality is Tsushima Island. R. tsushimensis is sometimes regarded as a subspecies of R. amurensis, but it isn't, because artificially produced hybrid embryos between R. tsushimensis and R. a. coreana are not viable. The species is closely related to R. okinavana, and these probably bridge R. japonica and R. tagoi.Diploid chromosome (2n), with 5 large pairs and 8 small ones making a total of 26 chromosomes.

This species inhabits plains and hillsides and is endemic to Tsushima, Japan.

This species breeds from January to April in still waters in rice fields, ponds, ditches and pools. It is often sympatric with R. dybowskii. However, different calls seem to prevent hybridization. Females lay approximately 400-500 eggs each. The eggs have a diameter of 1.7-2.3 mm. The larva usually have a dark spot on each side of their back.Mating call duration is 1 sec with 3-5 notes. Dominating frequency 2.1 kHz, with marked frequency modulation and clear harmonics.