Craugastor yucatanensis (Lynch, 1965)

Carbajal-Marquez, Ruben Alonso, Diaz-Gamboa, Luis F., Ramirez-Valverde, Tania, Garcia-Balderas, Christian M., Nahuat-Cervera, Pedro E. & Cedeno-Vazquez, Jose Rogelio, 2019, Description of the male of Craugastor yucatanensis (Lynch, 1965) (Anura, Craugastoridae), its advertisement call, and additional data on females, ZooKeys 900, pp. 129-139 : 131-135

Craugastor yucatanensis (Lynch, 1965)

Material examined.

Craugastor yucatanensis (23). Mexico - Quintana Roo State: Benito Juárez Mun. ECO-CH-H-1655; Felipe Carrillo Puerto Mun. ECO-CH-H-1878, 1904, 1932, 1949, 2014, 2015, 2016, 2042, 2105, 2393, 3538 - Yucatán State: Chemax Mun. ECO-CH-H-3790, 3791, 3792, 3793, 4537, 4538, 4539, 4540, 4541, 4542; Tinum Mun. ECO-CH-H-3539.

Diagnosis.

A member of the Craugastor (Hylactophryne) bocourti species series, most closely related to C. alfredi (Boulenger, 1898) (Lynch, 1965), characterized by having greatly expanded and truncate digital pads on the outer two fingers, possessing no vocal sac or slits ( Fig. 1A ), a relative large tympanum in adult males (74.7% [65.7-85.5%] of eye diameter) and females (52.4% [42-65.5%] of eye diameter), canthus rostralis rounded; supernumerary tubercles on palm and sole; venter semi-transparent or pinkish; finger pads large, slightly emarginate, and having a fine tarsal ridge. Differs from the closest related species within the series lacking vocal sacs (e.g., C. alfredi , C. campbelli (Smith, 2005), C. cyanochthebius McCranie & Smith, 2006, C. galacticorhinus ( Canseco-Márquez & Smith, 2004), C. glaucus (Lynch, 1967), C. megalotympanum (Shannon & Werler, 1955), C. nefrens (Smith, 2005), C. stuarti (Lynch, 1967), C. taylori (Lynch, 1966), and C. xucanebi (Stuart, 1941)) by a relatively larger tympanum in males - 74.7% of eye diameter (versus about two-thirds of eye diameter), supratympanic fold absent (versus poorly developed), and numerous small tubercles on the sole (versus few or absent).

Description and variation of males.

Adult males (N = 19) averaged SVL = 27.1 ± 1.7 mm (range 24.2-30.5 mm). Head somewhat broader (HW = 11.2 ± 0.9 mm [9.6 - 13.2]) than long (HL = 10.5 ± 0.6 mm [9.7-12.1]). Tympanum distinct, more than two-thirds the diameter of the eye (TM = 2.8 ± 0.2 mm [2.4-3.2]). Eye slightly longer (EL = 3.7 ± 0.3 mm [3.1-4.4]) than distance from EN = 3.6 ± 0.3 mm [3.1 - 4.0]). Average IOD = 3.4 ± 0.3 mm (2.8-4.0). Canthus rostralis rounded; loreal region slightly concave; tympanum transparent with a dark spot in the center; no dorsolateral, paravertebral, or occipital folds; supra and post-tympanic folds not distinct. Dorsum smooth; skin on venter smooth except for ventral surface of thigh which is areolate; scattered melanophores on chin, chest, and limbs; ventral disc present although obscure; posterior border of thighs slightly granular ( Fig. 1B ).

Tips of fingers expanded, slightly emarginate; the width of pad of 3rd finger (F3) averages 1.6 ± 0.2 mm (1.2-2.1); thumb with an enlarged thenar tubercle, almost as large as semi-divided cordiform palmar tubercle; subarticular tubercles round to slightly obtuse and projecting in lateral profile, rounded to ovoid in basal outline, Fingers I and II with one, Fingers III and IV with two; accessory palmar tubercles globular to slightly conical in lateral profile, rounded in basal outline; first finger as long as second; with two white glandular nuptial pads, one on thenar tubercle and the other, also on pollex, opposite and slightly lateral to distal subarticular tubercle ( Fig. 1C ). Toes expanded slightly. Supernumerary tubercles on metatarsus; tarsal fold present for one-third length of tarsus; inner metatarsal tubercle elongate, not compressed; outer metatarsal tubercle present, round, diameter one-fifth length of inner metatarsal tubercle; subarticular tubercles globular ( Fig. 1D ). Tibia length averages 14.9 ± 0.7 mm (14.1-16.3). Heel reaching anterior edge of eye; legs held at a little less than a right angle to the body.

Description and variation of females.

Adult females (N = 8; including four from the original description) had an average SVL = 35.0 ± 1.9 mm (range 31.2-37.1 mm). Head is broader (HW = 14.1 ± 1.1 mm [12.5-15.1]) than long (HL = 13.1 ± 1.7 mm [11.8-17.1]). Tympanum distinct, half the diameter of the eye (TM = 2.5 ± 0.4 mm [2.0-3.1]). Eye slightly shorter (EL = 4.7 ± 0.4 mm [4.1-5.1]) than distance from EN = 4.9 ± 0.3 mm [4.4-5.3]). Average IOD = 4.0 ± 0.3 mm (3.4-4.5). Canthus rostralis rounded; loreal region slightly concave; no dorsolateral, paravertebral, or occipital folds; supra and post-tympanic folds not distinct. Tips of fingers expanded, slightly emarginate; the width F3 = 2.3 ± 0.4 mm (1.6-2.7). Tibia length averages 18.2 ± 1.0 mm (17.0-20.4).

Color in life.

The coloration depends on the substrate and the time when the specimens are found. When males are active at night over vegetation or leaf litter, they have an Olive Yellow (117) to Smoke Gray (267) dorsal coloration, with Glaucous (289) to Sepia (279) blotches on dorsum and bars on limbs; sometimes a thin clear vertebral stripe is distinguishable ( Fig. 2 ). When found during the day in caves, they exhibit a coloration similar to that observed at night, but with a paler tone. When found during the day on leaf litter they have a Cinnamon-Rufous (31) dorsal coloration, where the blotches and bars are less evident. The dorsal coloration of females is Olive Yellow (117) to Smoke Gray (267) with scattered Glaucous (289) to Sepia (279) blotches when active at night, whether in caves or leaf litter. When found during the day inside caves, their coloration is paler ( Fig. 3 ), sometimes becoming completely Pale Pinkish Buff (3), similar to some karstic limestone inside the caves. When they are found in leaf litter, their coloration is Cinnamon-Rufous (31), and in both cases the blotches and bars are little evident. The arms and legs are banded, the iris Pearl Gray (262) with metallic bronze tones, and the lateral and ventral surfaces are semi-transparent or Pinkish White (216) in both sexes.

Color in preservative.

Dorsum Pale Neutral Gray (296), with Glaucus (289) to Brownish Olive (292) blotches on dorsum and bars on limbs; pupil Smoky White (261), iris and upper eyelid Grayish Olive (273); tympanum Pale Cinnamon (55); venter semi-transparent or Pale Buff (1) to Pale Pinkish Buff (3) ( Fig. 1B ).

Advertisement call.

The advertisement call of Craugastor yucatanensis is part of a communication system that consists of repetitive notes emitted every 10 seconds (6 times per minute). Every note has a duration of approximately 460 MS at a dominant frequency around 2600 kHz. These notes sound like a very short “peep” that resembles the weak chirping of a bird chick ( Fig. 4 ). The digital audio file can be accessed online at Díaz-Gamboa et al. (2019) at Soundcloud.

Distribution and natural history.

Craugastor yucatanensis is known from near sea level to 60 m elevation throughout its range on the central and northeastern portion of the Yucatán Peninsula ( Lee 1996; Ortiz-Medina et al. 2016). The vegetation in this area is classified as tropical deciduous forest, low and medium semideciduous forest; high, medium and low semi-evergreen forest; tall evergreen forest, with karstic limestone outcroppings ( Torrescano-Valle and Folan 2015). The males were located calling on 18-19 October 2016 and 22 July 2018, on vegetation 1.5-6.0 m above ground. Calling occurred at night (20:00-03:00 h) following afternoon or early evening rainfall, and during light rain later in the night. Many males could be heard calling from the vegetation. When we attempted to capture vocalizing males, they jumped to the ground where they jumped erratically, then stopped suddenly and became immobile in the leaf litter; crypsis was enhanced by rapid color change to darker tones (metachrosis). Additional males were found during the day and appeared to have been dislodged from a resting place in lower vegetation or leaf litter. Most females were found inside caves or at their entrance during day or night, and some females were found during the day in the leaf litter around rocky outcrops or caves. We did not observe egg laying, and juveniles were not detected. Predators of this species remain undocumented.

Sexual dimorphism.

Only males have prepollical nuptial excrescences. There was a significant difference between the SVL of adult males and females of C. yucatanensis (t = -9.72, df = 25, P <0.05). When the effect of body length (SVL) was removed, there was a significant difference between sexes in TM (F 1,24 = 11.21, P <0.05), where males possess larger TM average, SL (F 1,24 = 4.87, P <0.05) where females are larger in average, and EN (F 1,24 = 12.61, P <0.05) where females possess larger EN. There was no significant difference in EL (F 1,24 = 1.26, P> 0.05), IOD (F 1,24 = 0.01, P> 0.05), F3 (F 1,24 = 0.11, P> 0.05), HL (F 1,24 = 3.14, P> 0.05), and HW (F 1,24 = 0.48, P> 0.05) between sexes.

Figures

Figure 1. Male of Craugastor yucatanensis (ECO-CH-H- 4542) view inside of mouth (A) in dorsal aspect (B) ventral view of hand (C) and ventral view of foot (D). Photos by Humberto Bahena Basave.

Figure 2. An adult male Craugastor yucatanensis found sitting on vegetation at Xcan, Yucatan, Mexico. Photo by Pedro E. Nahuat Cervera.

Figure 3. An adult female Craugastor yucatanensis found inside a cave at Opichen, Yucatan, Mexico. Photo by Pedro E. Nahuat Cervera.

Figure 4. Spectrogram (top), and oscillogram (bottom) from a single note of the Craugastor yucatanensis advertisement call, recorded 11 km south of Nuevo Xcan, Yucatan, Mexico.