Cycloramphus lithomimeticus, Silva & Ouvernay, 2012

Silva, Helio Ricardo Da & Ouvernay, Daiane, 2012, A new species of stream-dwelling frog of the genus Cycloramphus (Anura, Cycloramphidae) from the State of Rio de Janeiro, Brazil, Zootaxa 3407, pp. 49-60 : 50-57

Cycloramphus lithomimeticus sp. nov.

( Fig. 1)

Holotype ( MNRJ 80585 ) Adult male, obtained at Cachoeira de Itinguçu (also spelled Itingussu), Coroa Grande, Municipality of Itaguaí , State of Rio de Janeiro, Brazil (22°54'3.44"S; 43°53'34.59"W, near 160 m) collected upriver from the dam used by the State Water Company ( CEDAE), by Daiane Ouvernay , Helio Ricardo da Silva, and Edicarlos Pralon in 30 August 2010.

Paratypes. MNRJ 80586 ♀ , MNRJ 80587 ♂ , MNRJ 80588 ♂ , MNRJ 80589 ♂ , MNRJ 80590 ♂ , MNRJ 80591 ♂ , MNRJ 80592 ♂ , MNRJ 80593 ♂ , MNRJ 80594 ♀ , MNRJ 80595 ♂ , MNRJ 80596 ♀ , MNRJ 80597 ♂ , MNRJ 80598 ♂ . All collected with the holotype.

Diagnosis. The new species is placed in the genus Cycloramphus based on the presence of well developed menisci on upper irises and tadpole morphology, with characteristic mouth and reduced upper and lower fins on the tail, a bilobed terminated skin flap on the venter, and habitat (wet rock near waterfall). Additionally, the new species is placed in the Cycloramphus granulosus group because of the granular dorsal skin, free toes (no webbing), and heterotrophic larvae inhabiting steep wet rocks, near waterfall splash area.

Cycloramphus lithomimeticus sp. nov. is a small sized species of Cycloramphus (adult males 24.6–31.0 mm, adult females 29.7–31.7 mm SVL) characterized by (1) snout round in dorsal and lateral views, (2) head wider than long, (3) eyes protruding, (4) white pigmented menisci on upper irises, (5) upper eyelid with small regularly spaced small granules; (6) dorsal skin granulose, covered by evenly spaced small granules; (7) tympanum not visible externally, but it can be observed after the skin is removed, (8) lack of vocal slits; (9) vocal sac indistinct, (10) dentigerous process of vomer round, (11) tibia and thigh of equal size, (12) toes free, (13) in life, dorsum brown and/or dark green, (14) in live specimens internal organs can be seen thorough the ventral skin and musculature (after fixation this area becomes cream and opaque), (15) lacking inguinal glands.

Comparison with other species of Cycloramphus . Cycloramphus lithomimeticus sp. nov. differs from all species of Cycloramphus except C. organensis Weber, Verdade, Salles, Fouquet , and Carvalho-e-Silva by the absence of externally visible inguinal macrogland on males. There are no glands internally or externally in C. lithomimeticus sp. nov. while in C. organensis such glands are present on the internal surface of the inguinal skin (see description in Weber et al. 2011). Because it has free toes, C. lithomimeticus sp. nov. can be readily distinguished from all the species with membrane between the toes ( C. asper Werner , C. boraceiensis Heyer , C. brasiliensis (Steindachner) , C. cedrensis Heyer , C. dubius (Miranda-Ribeiro) , C. duseni (Andersson) , C. fuliginosus Tschudi, 1838 , C. izecksohni Heyer , C. juimirim Haddad and Sazima , C. lutzorum Heyer , C. mirandaribeiroi Heyer , C. ohausi (Wandolleck) , C. rhyakonastes Heyer , and C. semipalmatus (Miranda- Ribeiro)). Because of the skin texture with granular appearance and small granules evenly distributed, C. lithomimeticus sp. nov. is similar to species in the C. granulosus group ( C. catarinensis Heyer , C. granulosus Lutz , and C. valae Heyer ) however, adult males of all these species have externally visible inguinal macroglands that are absent in C. lithomimeticus sp. nov. Both samples of C. granulosus from Serra da Bocaina (São Paulo) and Itatiaia (Rio de Janeiro) have vocal slits, C. lithomimeticus sp. nov. has only skin folds on the floor of the mouth lateral to the tongue. In Table 2 we present a comparison between samples of C. lithomimeticus sp. nov. and C. granulosus from Serra da Bocaina, São Paulo.

Holotype description. Body robust, elliptical in dorsal view; head wider than long ( Fig. 1) internarial distance smaller than eye-nostril distance and smaller than eye diameter; eye diameter larger than eye–nostril distance; menisci on upper irises evident, with round margin, and sprinkled with minute white dots; snout round in lateral and dorsal views ( Fig. 1); nostrils elliptical and protuberant; loreal region slightly concave; eyes protruding; tympanum not visible externally; supratympanic fold discrete, but well marked, extending from tympanic region to shoulder; vocal sac indistinct; vocal slits lacking; tongue smooth and round; skin folds present on the month floor lateral to the tongue; dentigerous process of vomer elliptical, right vomer with five, left vomer with four teeth; choanae medium-sized, rounded. Pseudodontoid on the madibular symphysis, protuberant and conical. On the maxilla, a round space between the premaxillae lodges the pseudodontoid when the mouth is closed. Mandible with finegrained tooth-like serration. Arm robust; forearm slightly thicker, ulnar fold absent; fingers without webbing or fringes; finger lengths IV > V > II = III; palmar tubercle round, larger than thenar, which is elliptical, each finger with one supernumerary tubercle. With the exception of palmar surface of Finger II and III, the rest of the palm skin is dark. Tibia length similar to thigh length; tarsal fold absent; toes without webbing and lateral fringes; toe lengths IV > V ~ III > II > I; inner metatarsal tubercle elliptical and larger than round outer metatarsal tubercle. Toes I and II have one supernumerary tubercle each; Toes III and V with two, and Toe IV with three tubercles. Plantar surface dark. Inguinal glands absent. Dorsal skin densely granular, with small and round granules, all of similar size, covering the head, eyelid, trunk, dorsal surface of arms, thigh, and in smaller number the tibia.

Color of holotype in preservative. Dorsal color pattern uniform dark brown, but near the flanks the brown is lighter. Dorsum with a central, irregular, cream spot, and an irregularly shaped, cream area over the scapulae. Near the inguinal region there are a few small, cream scattered spots. Head with a frontal triangular dark area. Laterally, face with two dark stripes, one from the eye to the lip, the other from the eye to the corner of the month; these stripes enclose white areas that are also marked by incomplete and lighter dark stripes ( Fig 1). Dorsally, the head is mostly dark brown with an interorbital thin white to cream line. The thigh, tibia, and foot are barred with darker thick lines. The forearm and hand also have are crossed by to thick dark bars. Fingers are irregularly barred, with cream lines on the articulation and on the tips. The venter is cream, with a few scattered minute dark chromatophores on the gular region. The palm and foot sole are darker.

Variation. Variation of measurements taken of adult males and females are given in Table 1. Variation in color pattern was described based on Heyer´s (1983) standards developed for species in the Cycloramphus fuliginosus group. Specimens of C. lithomimeticus sp. nov. vary in a similar manner ( Fig. 2). The dorsum may fit patterns A, C, and D, thigh color may fit patterns A, B, and C, venter the patterns A, B, C, and E. The sample studied includes (1) specimens with a well marked dark X on the dorsum, that extends from the back of the eyes to the middle of the vertebral column and has a clear spot in the confluence of the lines that make up the X (Pattern A); (2) specimens with dark brown dorsum with cream and small irregularly distributed spots (Pattern C); and (3) with darker irregular marks on the brown dorsum (Pattern D). Specimens have uniformly dark (Pattern A), mottled (B), or spotted (Pattern C) posterior portion of the thighs. On the venter, although live specimens all have translucent abdominal wall and skin that permits observation of the internal organs, after fixation, the skin turned uniformly light cream, with scattered small melanophores, which may be more concentrated on the throat region, on the thigh and arm ventral skin. On the upper lip, between the eye and the nostril, three cream colored bars separated by three brown stripes are present in all specimens. The dark stripes may vary in length and darkness.

Tadpole ( Figs. 3 and 4). Larval measurements for a sample of 11 tadpoles are presented in Table 3. The larvae are elongated, with the body and head, longer than wider and compressed dorsoventrally. Tail fins are low and restricted to the distal half of the tail, the ventral is more pronounced than the dorsal. The belly is flattened and has a shallow flap, which extends from the back of the mouth to the posterior end, over the vent tube and, in Stage 30, covers the limb buds and the vent tube, and has bilobed end. A spiracular tube is not present, but the skin that forms the ventral flap is pierced by a round opening, on the left side of the body. We injected water-diluted crystal violet through the spiracular opening and saw it spreading into a bag formed by the flap over the ventral body wall. The eyes are moderately large and dorsal and, in the Stage 30, already present menisci on the upper iris. Nostrils are minute and nearly round, with openings towards the front, and a little white-pigmented area in front of it. Ventrally, on the body and tail, there are no markings, and the general color is light cream. Dorsally, the body is dark brown, with the body part already resembling the adult color pattern, even in Stage 30. The tail is dorsally marked with dark outlined parentheses that may be either coincident on both sides or uneven, forming a general pattern that resembles a double helix. In live specimens, the dorsal color pattern is either pale salmon or green. The oral disk is ventral and relatively almost as broad as the head anteriorly. The anterior gap in the papillae is wide, and extends through entirely frontal part. The papillae are in a single row laterally and in two rows posteriorly. The tooth row formula is 2(2)/3(1). The two anterior tooth rows are larger than the posterior ones, and within each set the rows are of similar size. The keratodonts on each row are of different size, being A-2 the largest, A-1 ~ P-1, P-2 the next in size, and P-3 the smallest ones. The upper beak is longer than the lower one, and has the general shape of a moustache with the lateral ends thinner. The lower beak is in the shape of a pen tip, or a section of a cylinder. We were unable to identify lateral lines on the body or tail of the tadpoles.

Natural history. Individuals of Cycloramphus lithomimeticus sp nov. were observed only at night and are considered nocturnal. Males call from near crevices and cracks on the rocks in steep parts of the river, near waterfalls, in the splash zone. Tadpoles were found nearby, in permanently wet vertical or nearly vertical rock walls; sometimes, near the areas where adults were active. The analysis of stomach contents indicated that Hymenoptera was the main food item and that, in addition to vegetal matter, larvae of Lepidoptera, Diptera, Blattodea, Tricoptera, Coleopeta (larvae and adults), and Aranae were also found. In the river, C. lithomimeticus sp nov. occurs syntopic with the nocturnal Thoropa miliaris Boulenger (Cycloramphidae) and the diurnal Hylodes asper (Müler) and H. phyllodes Heyer and Cocroft (Hylodidae) .

Etymology. The specific epithet is a masculine adjective formed from the Greek words Lithos (meaning stone) and mim ē tikos (meaning to imitate) and is used in allusion to the species color pattern that serves as camouflage and makes individuals similar to the rock surface where they are at rest.