Description
Okinawa Green Tree Frog is a fairly large bodied frog with its body tapering to the groin. The dorsal surface is bright green and without any pattern. Depending on temperature and other factors, the green may turn to dark brown. Its canthus is sharp and lore slightly concave. Its snout slopes laterally and is longer than the eye. The nostril is nearer to the tip of the snout than to the eye. The interorbital is much wider than the upper eyelid. The internarial is wider than the distance from the eye and narrower than the interorbital. The vomerine tooth series is elliptical with 6-9 teeth (6-8 for subspecies R. v. amamiensis), with the center of it anterior to the line connecting the posterior margins of the choanae. Finger and toe tips have truncate discs with a circummarginal groove. The forelimb webbing is broad and rather well developed, leaving 2 phalanges free on the outer margin of the 3rd finger. Hindlimb webbing is also broad and relatively well developed, leaving 2 (1-2 in R. v. amamiensis) phalanges free on the outer margin of the 4th toe. The inner metatarsal tubercle is oval, while the outer one is absent. There is no dorsolateral fold, but a supratympanic fold is evident. Males have a median subgular vocal sac and a pair of slit-like vocal openings. Nuptial pads in males are yellowish white. The karyotype is diploid (2n=26), with 5 large and 8 small pairs of chromosomes.

Subspecies Z. v. viridis has a yellowish to whitish belly, with black dots around the edges. The rear surface of the thighs has a very distinct pattern of black dots or reticulations. The head width is 35% of the SVL, and is wider than long. The tympanum is nearly circular, measuring 40% of the eye diameter. The hand and arm length is 47% and the tibia length is 43% of the SVL. The tibio-tarsal articulation reaches the posterior border to the center of the eye. The skin of the back is nearly smooth or slightly rough, with scattered granules on the posterior half of the upper eyelid, around the elbow and on the back of hindlimb. The throat is nearly smooth, and in males, is weakly covered by dark pigments. Males are 41-54 (mean = 44) mm and females are 52-68 (mean= 57) mm in SVL.

Subspecies Z. v. amamiensis has a mottled belly with indistinct dark blotches and is flecked with lighter spots. The rear surface of the thighs may have some dark markings, but they are indistinct. The head is wider than long, with a width of 31% of SVL in males and 34% in females. The tympanum is elliptical, measuring 50-60% of the eye diameter. The hand and arm length is 50% of the SVL in males and 54% in females. Tibia length is 42% of the SVL in males and 46% in females. The tibio-tarsal articulation reaches the posterior border of the tympanum to the anterior border of the eye. The skin of the back is slightly rough, and granules are more dense on the head. There are also minute granules on the throat. Males are 45-56 (mean=51) mm and females are 65-77 (mean=71) mm in SVL.

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Japan

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (3 records).

Z. v. viridis occurs in Japan, on the islands of Okinawajima, Iheyajima, and Kumejima. It lives in forests, both in lowlands and on mountainsides. The type locality for Z. v. viridis is Okinawajima Island.

Z. v. amamiensis occurs on the two islands of Amamioshima and Tokunoshima. This subspecies can be found from the cultivated fields of the lowlands to the mountain forests, with a preferred microhabitat of shrubs and trees. For Z. v. amamiensis, the type locality is Naze, Amamioshima Island.

Life History, Abundance, Activity, and Special Behaviors
Z. v. viridis breeds from December to July. It constructs a foam nest at the edge of still waters in rice paddies, marshes, and ephemeral pools. The nest may be constructed in a shallow depression excavated by the male, under stones, or at the roots of grasses. Alternatively, the foam mass may be attached to ferns or low tree branches at the water's edge. Sometimes the mass is completely underground, as with Z. schlegelii. There are no published data on the number of eggs in a clutch. In contrast to the mainland Zhangixalus species, extra males do not participate in nest-building in this subspecies. The foam liquefies at about the time the eggs hatch, and it may drop or flow into the water, carrying the tadpoles with it. When this does not happen, the tadpoles may wiggle their own way into the water. During breeding season, Z. v. viridis is frequently preyed upon by snakes, such as Trimeresurus okinavensis.

The breeding season of Z. v. amamiensis goes from December to May and the larvae metamorphose by August. Otherwise reproduction for Z. v. amamiensis is basically the same as for Z. v. viridis.

Eggs are laid in a foamy mass containing creamy-colored eggs. For Z. v. viridis, the elliptical egg mass measures 100-130 mm, eggs are 2.2 mm in diameter. For Z. v. amamiensis, the elliptical egg mass measures 90x110 mm and eggs have a diameter of 2.4 mm.

Larva
For Z. v. viridis, matured larvae are over 40 mm in total length. Tadpoles have a finely dotted and slightly elongated tail. The dental formula is usually 1:4+4/1+1:2. SVL at metamorphosis is 17-19 mm. For Z. v. amamiensis, matured larvae are 50 mm in total length with slightly elongated tails and dental formula 1:4+4/1+1:2.

References

Goris, R.C. and Maeda, N. (2004). Guide to the Amphibians and Reptiles of Japan. Krieger Publishing Company, Malabar, Florida.

Maeda, N. and Matsui, M. (1990). Frogs and Toads of Japan, 2nd edition. Bun-Ichi Sogo Shuppan Co., Ltd., Tokyo, Japan.

Species Account Citation: AmphibiaWeb 2022 Zhangixalus viridis: Okinawa Green Tree Frog <https://amphibiaweb.org/species/4545> University of California, Berkeley, CA, USA. Accessed Nov 22, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 22 Nov 2024.

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