Nidirana lini (Chou 1999)

Rana lini is a frog of southern Yunnan, China, whose males reach 44.2-61.2 mm in SVL and females reach 44.2-61.2 mm in SVL. It has a slender body, with a head that is longer than wide. The rounded snout protrudes beyond the lower jaw and has protuberant, laterally oriented nostrils. The tympanum is visible. A ridge runs from the snout along the upper lip down to the axial region, where it is interrupted and forms a post-symphasial tubercle. Its tongue is large, cordiform and longer than wide, with a tenth of the posterior being notched. Vomerine teeth are present in two oval series. Dorsally, the skin is smooth with tiny spinules randomly located on the posterior half. There are distinct dorsolateral folds running from the eye to the groin, and smaller tubercles adjacent to the dorsolateral folds. A large, smooth, almost triangular glandular ridge is found behind the base of the forelimb. The limbs have thin irregular longitudinal dermal folds, and are slightly tuberculate. The ventral surfaces of the head, body and limbs are smooth, but the medioposterior half of the femoral segment of the hind limbs is coarsely wrinkled. The posterior dorsal surface of the thigh is smooth, while the skin around the vent is quite rugose (Chou 1999).The forearms of the frog are moderately robust, and its fingers are relatively long and slender, and free of webbing. The tips of the fingers are somewhat dilated into discs, each with latero-ventral grooves separating dorsal and ventral surfaces. The fingers are fringed laterally, with the inner margins of the second and third fingers with more evident and wider dermal flaps than those of outer margins (III>IV>I>II). The hind limbs of R. lini are long and slender, and its toes are fringed laterally with a distinct dermal flap running along the lateral edge of the fifth toe (IV>III>V>II>I). Toe tips are very similar to those of the fingers. A pair of prominent subgular vocal sacs is present in males. Nuptial pads are also present in males, in two clusters, one on the medial edge of lower thumbs and one on the thenar tubercle (Chou 1999). In life, the ground color ranges from yellowish to grayish brown, with a yellowish brown vertebral stripe. The stripe may be lacking or interrupted in some individuals. The flanks and dorsal surfaces of the hind limbs are grayish brown, while the lateral surfaces of the arms are yellowish brown. On the flanks, the postaxial ridge is somewhat transparent. The mandibular ridge is a silvery white. In preservative, the dorsal surface of the body is dark brown with gray irregular vertebral stripes, with the area near the dorsolateral folds being pale brown. Black spots are present on the eyelids. The mandibular ridge is white. Dorsolateral folds are bi-colored, with the upper side pale brown and the lower side being dark brown. The loreal region is dark brown and a distinct dark brown temporal marking extends from behind the eye to above the axial region. The tympanum is yellowish brown. The flanks have large spots scattered densely near the dorsolateral folds and faintly near the belly. The frog is dark brown around the low warts, and the postaxial ridge is glandular and grayish brown. The rear of the thigh is pale brown, with large scattered dark brown spots. The venter is light grayish yellow, and vocal sacs are grayish brown. The anterior and lateral surfaces of the upper arm have a pair of parallel oblique dark stripes, of which the anterior stripe is wider and bordered with white lines. The posterior stripe is thin, extending onto the upper part of the lower arm. The posterior surface of the arm also has dense, large, dark brown spots, with most connecting into stripes or patches. There are black crossbars bordered with pale brown on the thigh, tibia and tarsus. The ventral surface of the foot is pale brown, and the webbing is finely mottled with black spots (Chou 1999). Tadpoles of this species are 18.2-21.0 mm in head-body length during stages 35-39. The body is oval, somewhat triangular in the lateral view, and slightly rounded above and below. Both margins of the tail are weakly convex, gradually tapering to a pointed tip. It has a broadly rounded snout in dorsal view, and rounded in profile. The eyes are located dorsolaterally, and are not visible from below. The nostrils are open and dorsolateral as well. The spiracle is sinistral, placed low on the side, and directed dorosoposteriorly, while the vent tube is long, dextral and attached to the ventral fin. The oral disc is anteroventral and emarginate. The upper labium has marginal papillae with a wide gap, and one row of short papillae at the corner, but no submarginal papillae. The lower labium has a continuous row of elongate papillae with 2-4 submarginal papillae at the corners. No fringes are present. The tooth formula is 2(2)/3(1) (Chou 1999). The dorsum of the tadpole body is pale brown with dark brown spots. The venter is gray and yellowish gray anteriorly. The fins are gray, caudal muscles are yellowish gray and both are mottled with large black spots that are densely pigmented on margins and along the caudal mid-line (Chou 1999).Rana lini was first discovered by Chou (1999). The species was named in honor of Edgar Jun-yi Lin for his studies on Taiwan’s amphibians and reptiles and in leading action for environmental protection of the island (Chou 1999).

Rana lini has been found in two montane localities (Jiangchen and Luchun counties) in southern Yunnan, China, at an elevation of 1400-1650 m above sea level (Chou 1999). It probably occurs more widely, and may eventually be recorded from neighboring Myanmar, Lao People’s Democratic Republic and Vietnam (IUCN 2006). Its habitat includes rice paddies, freshwater marshes, ponds, swamps, bogs, fens, peatland and irrigated land and channels (Chou 1999; IUCN 2006).

Males vocalize and are known for their distinct low frequency calls. In active choruses, the call consists of 5-7 indistinct, fast-pulsed notes with a "goo" sound. Lengths of the calls are not constant, as lengths of notes diminished gradually and lengths of intervals increased through series of notes. The first note is followed by an intense short croak, and the second note is distinctly longer than the last note. Intensity modulation among pulses is most distinct in the first note and relatively indistinct in subsequent notes. The dominant frequency is at about 2 kHz spread over a 1440-2680 Hz range. The frequency of the fundamental harmonic (which is not well-defined) is at about 0.5 kHz spread over a 280-960 Hz range, with weak frequency modulation. In Luchun, the calls of this species were heard from rice paddies, marshes, and ponds. In Jiangeheng, males were found vocalizing from the water surface under bushy vegetation near the bank of a pond. Chou (1999) found three females from Luchun and Jiangchen that contained yolked oviducal eggs of 1.7-1.8 mm in diameter. Also, only late stage tadpoles of R. lini were found, along with the observation that the tadpoles are a profundal, benthic form inhabiting the deeper part near the shorelines (Chou 1999).

Habitat is being lost rapidly due to infrastructure development for transport and human settlement in the South Yunnan mountainous region, posing the main threat to this species (Chou 1999; IUCN 2006). Other major threats include collection by humans for food and water pollution. It occurs in at least one protected area, the Huanglianshan and Xishuangbanna National Nature Reserve (IUCN 2006).

This species is a source of food for humans (IUCN 2006).

Nidirana lini is a species of frog in the family Ranidae. It is known with some certainty from southern Yunnan (China), Laos, Thailand, and north-western Vietnam. It has been mixed with Nidirana adenopleura and Nidirana chapaensis; its exact distribution is unclear, in particular whether populations referred to as N. adenopleura in southern China to Zhejiang in the east belong to this species.

It inhabits rice paddies, marshes, and ponds and the surrounding habitats, and it is locally common. It is threatened by harvesting, pollution, and habitat loss. The population number is unknown, but it is considered locally abundant. It is protected by Huanglianshan and Xishuangbanna Nabanhe Liuyu National Nature Reserves.