Ryukyu-Aka-gaeru, Ryukyu Brown Frog
Species Description: Matsui M 2011 On the brown frogs from the Ryukyu Archipelago, Japan, with descripitons of two new species (Amphibia, Anura). Current Herpetology 30: 111-128.
Rana ulma has a snout-vent length of 33-39 mm in males, 42-51 mm in females. Small tubercles with asperities are present on the dorsum, sides, and tarsus, as well as on the posterior half of the eyelids. The snout is pointed, and the tympana are somewhat large, with a diameter three-fifths that of the eye. A dark band extends over the tympanum, and a white stripe is present at the top of the upper lip. No vocal sac is present in males. Dark spots are present on the venter. Digit tips are swollen, but are not grooved. R. ulma has a thinner dorsolateral stripe than that of its closest relative, R. kobai. Eggs are not laid in a globular mass, as is done by some closely related species (Matsui 2012).
R. ulma is a small, relatively slender member of the Rana genus, with females being larger than males. The dorsum, sides, tarsus, and rear portion of upper eyelids are scattered with small tubercles, which have white asperities, or roughness. The throat, chest, and abdomen are smooth. The head is longer than it is wide, with a pointed snout. The snout tip is rounded when viewed from the side, and extends past the lower jaw. The nostrils are located close to the tip of the snout. A circular, distinct tympanum is present, about three-fifths the width of the eye. The interorbital distance is often slightly less than the width of the upper eyelids. Vomerine teeth are present in two small, oval series. The tongue is notched, and lacks papilla. No vocal sac (or vocal opening) is present. A supratympanic fold extends from the posterior of the eye to just above the insertion of the arm. Behind this is a thin dorsolateral fold extending to the groin. The forelimbs in R. ulma are stout, with slender, unwebbed digits. Fingertips are rounded, but lack grooves. Three large palmar tubercles are present, as are distinct supernumerary and subarticulate tubercles. A distinct, cream-colored nuptial pad covers the first digit, extending from the base to the subarticulate tubercle. R. ulma has long hind limbs, which are over three times the length of the forelimbs. The feet are moderately webbed, and the tips of the toes resemble the tips of the fingers. Subarticulate tubercles are prominent, as is the inner metatarsal tubercle (Matsui 2012).
Coloration: In preservation, the dorsum of R. ulma is a light greyish-brown. A dark gray interorbital bar is present. A faded, darkened chevron is located about the scapula. A white stripe is present on the upper lip, and above that is a dark brown stripe which extends from the tip of the snout to the insertions of the arms, covering the tympanum. Crossbarring is present on the upper surfaces of the limbs. The posterior portion of the thigh is irregularly spotted. The ventral surface of R. ulma is whitish with dark gray spotting. The ventral surface of the foot is a dark gray (Matsui 2012).
Variation: Females are typically larger than males, but males generally have a larger tympanum and stronger webbing on the feet (Matsui 2012).
Tadpole morphology: Tadpoles, at stage 33, have a total length of around 26.4 mm, with a head-body length of 9.9 mm. Tadpoles at stage 39 have a total length of around 33 mm, with a head-body length of 10.8 mm. The tadpoles are of a normal type, and do not have ventral modification (such as the sucker like structure seen in R. sauteri). Head and body have a flattened dorsal surface, but a rounded (spheroid) ventral portion. The snout is rounded, with eyes located dorsolaterally, which are not visible from below. Open, dorsolateral nostrils are located closer to the tip of the snout than to the eye. An oral disc is present anteroventrally. The tail is long and muscular, and tapers to a rounded tip (Matsui 2012).
Juveniles at metamorphosis, measure about 12 mm in snout-vent length (Matsui 2012).
Tadpole coloration: In preservation, the dorsal and lateral surfaces of R. ulma tadpoles are light brown, with black dots scattered on its back. The tail is dark brown with light mottling, and the fins have black dots throughout (Matsui 2012).
Distribution and Habitat
R. ulma is only known from Okinawa and Kume, islands of the Okinawa Island Group, Central Ryukyus, Japan (Matsui 2012).
R. ulma inhabits forests from lowland to montane regions, near trails and small streams (Matsui 2012).
Life History, Abundance, Activity, and Special Behaviors
R. ulma breeds in December, depositing eggs in the shallow headwaters of streams or in shallow pools near montane trails. Water temperatures may range from 11 to 14.5ï¿½C. Clutches of around 320 eggs are laid in small, loosely tied masses of about 10 eggs each. Ova range in size from 2.2-2.6 mm (Matsui 2012).
Calls of males resemble those of a chicken, and show a complicated structure. Males may aggregate into choruses and call synchronously. Calls may come in the form of 1-7 notes, each with many fine pulses. Note duration varies from 3-22 ms, with 46-114 ms between notes. Time between calls may vary from 183ï¿½776 ms. Frequency of calls ranges from 1850-4500 Hz, with a dominant frequency between 2250 and 3400 Hz (Matsui 2012).
Predators of R. ulma include the Okinawa Pitviper, Ovophis okinavensis, and Namiye's Frog, Limnonectes namiyei (Matsui 2012).
Trends and Threats
The Okinawa Prefecture has designated the R. ulma population on the island of Kume a locally protected population (Matsui 2012).
The species authority is Masafumi Matsui (Matsui 2012).
The specific name, ulma is derived from a word in Uruma (a dialect of the Ryuku islands) meaning a space of a piece of coral, or the coral island, Okinawa, where R. ulma is found (Matsui 2012).
R. ulma is most closely related to Rana kobai, another species of brown frog located on nearby islands. Other close relatives include R. tsushimensis from Tsushima Island and R. sauteri from Taiwan (Matsui 2012).
Matsui, M (2011). ''On the brown frogs from the Ryukyu Archipelago, Japan, with descripitons of two new species (Amphibia, Anura).'' Current Herpetology, 30, 111-128.
Written by John Cavagnaro (john.cavagnaro AT berkeley.edu), University of California Berkeley
First submitted 2012-04-23
Edited by Mingna (Vicky) Zhuang (2012-10-04)
Species Account Citation: AmphibiaWeb 2012 Rana ulma: Ryukyu-Aka-gaeru <http://amphibiaweb.org/species/7776> University of California, Berkeley, CA, USA. Accessed May 24, 2020.
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Citation: AmphibiaWeb. 2020. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 24 May 2020.
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