Hyloscirtus tigrinus

Coloma, Luis A., Carvajal-Endara, Sofía, Dueñas, Juan F., Paredes-Recalde, Arturo, Morales-Mite, Manuel, Almeida-Reinoso, Diego, Tapia, Elicio E., Hutter, Carl R., Toral, Eduardo & Guayasamin, Juan M., 2012, 3364, Zootaxa 3364, pp. 1-78 : 45-48

Hyloscirtus tigrinus

Description. The oral disc of an individual of series QCAZ 41351 is depicted in Figure 15G. It was collected in Quebrada Corazón, 2638 m, Santa Bárbara, Provincia de Sucumbíos, Ecuador, in a slow moving pool under a cascade of 2.5 m high in a stream by Luis A. Coloma and Juan F. Dueñas on 3 March 2009. The following description is based on a single specimen in Stage 34 (QCAZ 31550), from Quebrada Corazón (ca. 01° 38' 42'' N, 77° 31' 48'' W; 2620 m), Santa Bárbara, Provincia de Sucumbíos, Ecuador, collected in a slow moving pool in a stream by Fernando P. Ayala, Wesley Chun, and Rosario Castañeda on 23 February 2006. All values are in millimeters. Total length 98.5, body length 36.5 (37.1% of total length). Body ovoid and depressed; width at level of spiracle 22.9, and height at same position 19.2; head width at level of eyes 19.2; anterior margin of snout uniformly rounded in dorsal view and sloping at level of nares in lateral view; lateral-line system evident and symmetrical, having supraorbital, infraorbital, longitudinal oral, mandibular, angular, posterior infraorbital, middle body, dorsal body, and ventral body lines. The middle bodyline originates dorsally approximately 1.0 behind the posterior end of eyes, and runs dorsolaterally at the level of the trunk, becoming completely lateral at level of tail. Dorsal lines run parallel to dorsal fin. Mandibular line originates at anterior end of venter and runs laterally forming an arch around each side of the oral apparatus. Ventral lines start anterior to vent tube, run diagonally over trunk until they make a sharp turn down and return to the venter. Angular line is continuous with infraorbital line and extends perpendicular to infraorbital, longitudinal oral, and mandibular lines. Longitudinal oral line originates at midlevel of angular line and runs parallel to the longitudinal axis until it reaches the arch of the mandibular line. Supra- and infraorbital lines begin at the snout and run posteriorly until they merge around the eyes.

Nostrils small, oval, and directed anterolaterally; opening 8.0 from tip of snout; internarial distance 7.3. Eyes positioned and directed dorsolaterally; eye length 3.0, eye width 2.9; interorbital distance 12.0. Spiracle sinistral, located at midbody level, inner wall free from body; tube length 5.7, tube transverse width 5.2; spiracular opening directed posterodorsally, diameter 1.9; distance from tip of snout to spiracular opening 24.5. Vent tube free, opening directed dextrally; tube length 6.9, tube transverse width 0.4. Developing hind-limb bud 4.5 in length, with indentation between second and third, third and fourth, and fourth and fifth toes. Tail length 63.4; caudal musculature robust, narrowing gradually up to the tail terminus; at tail-body junction, tail muscle width 11.7; tail muscle height 13.1; maximum height of tail 20.6.

Oral disc located anteroventrally, emarginated twice ventrally; transverse width 11.1; border of disc irregular, ventral papillae absent (see variation); 66 papillae located laterally (49 on left side and 17 on right side); submarginal papillae absent; upper jaw sheath forming an arch, no pigmentation present; transverse width including lateral processes 4.4 (39.6% of transverse width of oral disc); serrate edges absent in both sheaths. Labial tooth row formula 5(3–5)/7(1), not clearly conformed. Dental crests show many losses and no gap is clearly demarcated; in all rows teeth are missing.

Color in preservative. In dorsal view, body and caudal musculature are dark brown. In lateral view, flanks lighter brown, fins brown; dorsal and ventral fins with dark blotches scattered irregularly on tail muscles. Tail muscles cream flecked with brown. Spiracle unpigmented. In ventral view, venter grayish blue; oral apparatus cream and covered with dark gray blotches. Iris tan gray. Closer examination of skin shows that overall pigmentation is composed by filiform cromatophores, except for the blotches at muscles and fins, composed of melanophores in dots.

Color in life. In dorsal view, body and caudal musculature dark brown to olive green. Tail about same coloration as body. Snout light brown. In lateral view, flanks lighter brown with blue iridescences at spiracle level. Fins translucent to brown; dark blotches and creamy white dots scattered irregularly on tail muscles and dorsal and ventral fins. Caudal muscles cream flecked with brown, becoming clearer towards tail terminus. Spiracle unpigmented, however a blue iridescence can be seen in certain light conditions. Venter metallic blue. Oral apparatus cream. Iris metallic green with fine black reticulations.

Variation. Variation of ten meristic characters of tadpoles in Stages 25–39 are shown in Table 8; nine tadpoles in Stages 25–39 greatly varied in total length that ranged from 48.0– 96.7; body length ranged from 14.1–36.5; tail length ranged from 34.4–66.4. Variation in LTRF cannot be correctly described because 66.6% of tadpoles (Stages 25, 27, 34) showed deformed oral apparatus, completely or partially depleted of denticles, with variable assymetric numbers of labial papillae, absence and presence of papillae in the posterior labium of oral disc. Absence of keratinized teeth may be due to chytrid infection. Assymetry in the number of papillae on each side of the labium and absence of papillae in the posterior labium is intriguing since there are no hylid tadpoles without ventral papillae. We interpret the assymetry and absence of papillae as abnormal development or damaged oral discs. From the tadpoles that had relatively distinct tooth rows, variation in number of this structure was from 5(4–5)/7(1) (Stage 25) to 7(7)/7(1) (Stage 31). The later tadpole seems abnormal and has labial tooth row ridges with no teeth. Nonetheless, the same number of upper and lower tooth rows is interesting.

The lateral-line system was evident in all individuals examined; however, variation in the placement and origin of lines is observed among individuals. Arrangement of ventral bodyline may be symmetrical or asymmetrical on the left flank of body, where the spiracle is located.

Color patterns and arrangement of blotches in fins as well as tail muscles varied through ontogenetic development ( Figs. 26, 27). In the smallest individuals at Stage 25, numerous creamy white cromatophores can be seen against a black background both in dorsal and ventral fins. As ontogenetic development advances, creamy white dots are replaced by dark blotches, which in turn become numerous in older stages giving the overall tail coloration a darker appearance. Closer examination reveals that blotches are made up of cromatophores in dots that merge progressively as individuals grow. Individuals at Stage 25 have cream tail muscles, whereas some of the largest individuals at advanced pre-metamorphic stages show a reddish brown coloration in the muscles of the proximal half of the tail ( Fig. 27).

Considerable ontogenetic change occurs in coloration of individuals of Hyloscirtus tigrinus from tadpoles to adults ( Fig. 27). Approximately at Stage 42, when the limbs are developed, an overall light green coloration appears on the dorsum and flanks. The limbs go from yellow to light green. At Stage 42 when the first pattern of black dots pattern appear, contrasting against the green background. By Stage 45, the entire dorsum is green with black dots in the peripheral areas of the flanks, vent, and head; the snout changes from brown to yellowish green. The toes and venter acquire a bright yellow coloration. At Stage 46, small black dots are extensive on the dorsum, where a tan-yellowish green background begins to appear. A black mottled pattern and elongated bars appear against a yellowish green background at the level of the thighs, flanks, and upper maxillae. Snout–vent length of an individual fixed at this stage measured 36.0 mm ( QCAZ 40331 from Santa Bárbara, 2638 m, Provincia de Sucumbíos, Ecuador, collected as tadpole by Juan F. Dueñas and Ítalo G. Tapia on 17 September 2008). Finally, juveniles at latter stages show a reticulated pattern of black mottling on the limbs, as well as the dorsum, thighs and feet, giving the individual a jaguar-like appearance. The sides of the head have a silvery-white coloration. Welldefined black bars extend on the flanks of body. Bright yellow mottling is evident in the hidden surfaces of thighs of posterior limbs .