Smooth Skinned Ditch Frog

Leptodactylus pallidirostris Lutz, 1930

Leptodactylus pallidirostris Lutz, 1930, plate I: fig. 3 [type locality: British Guiana; Kartabo; lectotype AL-MN 1829, adult male].

DIAGNOSIS.—Leptodactylus pallidirostris occurs in the Guiana shield region. The other species of Leptodactylus that occur in the same area with toe fringes (except L. ocellatus and its closest relatives) are L. bolivianus, diedrus, leptodactyloides, petersii, and sabanensis. Leptodactylus pallidirostris is a small species (females 30–43 mm SVL, males 28–37 mm SVL) with short to medium dorsolateral folds; L. bolivianus is a large species (females to 88 mm SVL, males to 94 mm SVL) with a pair of long, well-developed dorsolateral folds. Some individuals of L. pallidirostris appear to lack dorsolateral folds and the ventral and posterior thigh patterns merge; all diedrus lack dorsolateral folds and the ventral and posterior thigh patterns abut. Leptodactylus pallidirostris is smaller than leptodactyloides (leptodactyloides females 35–56 mm SVL, males 28–48 mm SVL). The commonest lip stripe condition in pallidirostris is distinct stripes that often extend from under the middle of the eye; the commonest condition in leptodactyloides is indistinct, and all stripes extend from the posterior corner of the eye. Many L. pallidirostris individuals (69%) have light chin/throat spots; few (10%) leptodactyloides do. The belly of L. pallidirostris usually is lightly mottled with the pattern ranging from a fine mottle to distinct, rather dark blotches; the belly of petersii usually is extensively mottled and often in an anastomotic pattern. The commonest toe-tip condition in L. pallidirostris is swollen with some individuals having expanded tips or small disks; the commonest toe-tip condition in petersii is just swollen and no individuals have expanded toe tips or small toe disks. Leptodactylus pallidirostris is smaller than sabanensis (sabanensis females 42–57 mm SVL, males 35–46 mm SVL). The most common lip stripe condition in sabanensis is indiscernible, and, when lip stripes are discernible, they extend from the posterior corner of the eye (see comparison with leptodactyloides above for pallidirostris condition). The advertisement call of L. pallidirostris has a broadcast frequency range of 1500–3500 Hz with maximum energy of 2500–3500 Hz; the broadcast frequency range of the advertisement call of sabanensis is 900–2300 Hz with maximum energy of 1400–1800 Hz.

ADULT CHARACTERISTICS (N = 152 females, 100 males).—Light posterior lip stripes rarely very distinct (3%), usually distinct (46%) or indistinct (42%), occasionally not discernible (8%), when discernible, the stripes extending from under mideye or from posterior corner of eye; light posterior thigh stripes rarely very distinct (2%), often distinct (23%) or indistinct (23%), usually not discernible (51%); dorsolateral folds occasionally (apparently) absent (7%), usually short (79%), sometimes moderate length (15%); toe tips just swollen (13%), swollen (28%), just expanded (25%), expanded (22%), or with small disks (12%); male black thumb spines occasionally small size (6%), rarely small-medium size (1%), usually medium size (89%), rarely medium-large size (4%); chin/throat usually with light spots on a darker background (69%); belly patternless (11%), lightly mottled (43%), moderately mottled (35%), or extensively mottled (10%).

Females 29.5–42.8 mm SVL (x = 36.9 ± 2.6), males 27.8–37.3 mm SVL (x = 33.2 ± 1.9); female head length 32%–40% SVL (x = 37 ± 1%), male head length 34%–42% SVL (x = 38 ± 2%); female head width 30%–40% SVL (x = 32 ± 2%), male head width 30%–38% SVL (x = 34 ± 2%); female tympanum diameter 6%–9% SVL (x = 7 ± 0%), male tympanum diameter 7%–9% SVL (x = 8 ± 0%); female thigh length 36%–48% SVL (x = 42 ± 3%), male thigh length 35%–53% SVL (x = 43 ± 3%); female shank length 42%–52% SVL (x = 46 ± 2%), male shank length 42%–54% SVL (x = 47 ± 2%); female foot length 48%–60% SVL (x = 53 ± 2%), male foot length 50%–61% SVL (x = 55 ± 2%).

LARVAL CHARACTERISTICS.—Unknown.

ADVERTISEMENT CALL.—Call rate 0.8–2.7 calls per s; call duration 0.03–0.05 s; calls of two notes, first note a single pulse, second note partially pulsed with 2–5 partial pulses; calls frequency modulated with very fast rise times; broadcast frequency range 1500–3500 Hz, maximum energy in higher portion of frequency range; weak harmonic structure indicated but evidence for harmonics not decisive (Figures 27–29).

KARYOTYPE.—Unknown.

GEOGRAPHIC VARIATION.—Geographic variation for this species has been discussed in the analysis of “Region 5—Guiana Shield” OTUs.

DISTRIBUTION.—The Guianas, north-central Roraima, Brazil, and Venezuela from known elevations of sea level to 360 m (Figure 39; Appendix 2).

Leptodactylus validus Garman, 1887

Leptodactylus validus Garman, 1887:14 [type locality: Kingston, St. Vincent; lectotype MCZ 2185, adult male].

DIAGNOSIS.—Leptodactylus validus is only known to occur with or near to the fringe-toed Leptodactylus species bolivianus and nesiotus (excluding L. ocellatus or one of its closest relatives). Leptodactylus validus is smaller than bolivianus (validus females 38–52 mm SVL, males 30–43 mm SVL; bolivianus females to 88 mm SVL, males to 94 mm SVL), and no validus have long dorsolateral folds whereas all bolivianus do. In those individuals of L. validus with discernible lip stripes, the stripes extend from the posterior corner of the eye posteriorly; L. nesiotus has a broad light stripe that extends from at least under the eye.

ADULT CHARACTERISTICS (N = 36 females, 71 males).—Light posterior lip stripes rarely very distinct (2%), often distinct (30%), usually indistinct (55%), sometimes not discernible (14%), when discernible, stripes extending from posterior corner of eye; light posterior thigh stripes rarely very distinct (3%), otherwise distinct (37%), indistinct (23%), or not discernible (38%); dorsolateral folds (apparently) rarely absent (1%), usually short (91%), occasionally medium length (8%); toe tips just swollen (3%), swollen (53%), just expanded (4%), expanded (27%), or small disked (14%); male black thumb spines small-medium size (2%), medium (65%), medium-large (21%), or large (13%); chin/throat rarely with light spots on a darker field (4%); belly rarely essentially lacking pattern (3%), usually lightly mottled (66%), often moderately mottled (29%), rarely extensively mottled (2%).

Females 38.1–51.5 mm SVL (x = 44.3±2.9), males 30.5–42.9 mm SVL (x = 37.8±2.6); female head length 35%–39% SVL (x = 36±1%), male head length 34%–41% SVL (x = 37±2%); female head width 32%–36% SVL (x = 34±1%), male head width 32%–39% SVL (x = 35±1%); female tympanum diameter 7%–9% SVL (x = 8±0%), male tympanum diameter 7%–9% SVL (x = 8±0%); female thigh length 40%–49% SVL (x = 44±2%), male thigh length 41%–52% SVL (x = 45 ± 2%); female shank length 44%–50% SVL (x = 47±2%), male shank length 45%–53% SVL (x = 48±1%); female foot length 48%–58% SVL (x = 53±2%), male foot length 50%–59% SVL (x = 54±2%).

LARVAL CHARACTERISTICS.—The available tadpole data require discussion. Kenny described the larvae of a member of the podicipinus-wagneri complex from Trinidad as L. podicipinus petersi (1969:75, fig. 36), and samples of larvae are on hand from Tobago and St. Vincent. The larvae from the three islands are each very distinct from each other, certainly at the species level of difference. At least for the samples from St. Vincent and Tobago, the identification of the larvae is not certain; identification is based on known adult occurrences and known Leptodactylus larval morphologies. The larval type described by Kenny from Trinidad is unique for all other known Leptodactylus in having a ventral papillary gap in the oral disk, suggesting either that the larvae described and figured are abnormal or that the larvae in fact are not Leptodactylus, but represent some other genus. The larvae described by Kenny further differ from the Tobago and St. Vincent larvae in that the A-2 labial tooth row is split in the stage 29 Trinidad larvae (stage based on published figure), whereas for all similar stage (and greater) larvae from Tobago and St. Vincent, the A-2 labial tooth row is entire. The larvae from Tobago correspond in total size and proportions (particularly the oral disk) with the L. bolivianus-ocellatus group larvae on the mainland of South America rather than with the podicipinus-wagneri complex. As far as is known, no member of the L. bolivianus-ocellatus group occurs on Tobago (Hardy, 1982); however, Hardy (1982:68–69) discussed reports of a large frog (which provided frog legs for human consumption) on Tobago that was said to live in holes in the forest and come out at night. No voucher specimens of this reported frog have been taken, although there is a large femur from the Robinson Crusoe Cave that is leptodactylid, not bufonid (Hardy, 1982; R.I. Crombie, pers. comm.). Hardy (1982:69) thought the reports might refer to L. pentadactylus, but has since discounted that species allocation for the reports (Hardy, 1984). It is possible that the reports referred to a member of the bolivianus-ocellatus complex, but as no transformed specimens of this complex are known as vouchers from Tobago, nothing of certainty can be stated at this time. For present purposes, larval descriptions are provided for the Tobago and St. Vincent samples separately.

Tobago Larvae: Maximum total length stage 37, 34.8 mm; body length 36%–41% (x = 38.1) total length; maximum tail depth 56%–62% (x = 59.5) body length; nostril mid-distance between tip of snout and eye or just closer to either tip of snout or eye; internarial distance just greater than or about equal to interorbital distance; eye diameter 8%–10% (x = 9.2) body length; mouth subterminal; oral disk entire; spiracle sinistral; anal tube median; oral papilla formula 1-2 or 1-2-3-2; oral disk width 17%–20% (x = 18.9) body length; oral papilla gap 26%–33% (x = 29.7) oral disk width; labial tooth row formula ; number of labial teeth in of row A-2, stages 36–37, about 95; number of labial teeth in 0.1 mm measured in middle of of row A-2, 5.5–8 (x = 6.4); tadpole entirely uniform brown, heavily suffused with melanophores, including oral disk, anal tube, and entire tail.

St. Vincent Larvae: Maximum total length stage 36, 25.8 mm; body length, stage 25, 41%–46% (x = 43.7) total length, stages 29–38, 38%–44% (x = 41.0) total length; maximum tail depth, stage 25, 41%–52% (x = 44.7) body length, stages 29–38, 49%–58% (x = 53.5) body length; nostril mid-distance between tip of snout and eye or just closer to eye (some stage 25 individuals only); stage 25 larvae internarial distance about equal to or just less than interorbital distance, stage 29–38 larvae internarial distance just greater than interorbital distance; eye diameter, stage 25, 6%–8% (x = 6.3) body length, stages 29–38, 8%–12% (x = 10.7) body length; mouth subterminal; oral disk entire; spiracle sinistral; anal tube median; oral papilla formula 1-2; oral disk width 23%–29% (x = 25.5) body length; oral papilla gap, stage 25, 39%–56% (x = 46.3) body length, stages 29–38, 28%–39% (x = 33.2) body length; labial tooth row formula, stage 25, 2(2)/3, stages 29–38, ; number of labial teeth in one split row of A-2, stage 25, 45–60; number of labial teeth in row A-2, stages 29–38, 100–115; number of labial teeth in 0.1 mm measured in middle of of row A-2, 7.5–12 (x = 9.2); stage 25 larvae light with scattering of melanophores on body and tail, either lacking or very few on oral disk, no melanophores on anal tube, melanophores not extending to uppermost or lowermost tail fins; stage 29–38 larvae gray, dorsal body uniform with heavy profusion of melanophores, ventral body almost uniform to distinctly mottled, with profusion of melanophores, heavier behind oral disk than over guts, oral disk with melanophores, anal tube with melanophores, tail gray with heavy profusion of melanophores on entire tail except for a large very distinct to indistinct light spot over anterior tail musculature.

ADVERTISEMENT CALL.—Call rate of 1.1–1.9 calls per s; call duration 0.03–0.06 s; calls usually of two notes, first note a single pulse occasionally weak or apparently absent, second note with 2–6 partial pulses; calls frequency modulated with very fast rise times; broadcast frequency range 1300–3500 Hz, with maximum energy in 2300–3500 Hz range; harmonic structure equivocal, but second note perhaps representing a shift to a harmonic of the first note (Figures 31–33).

KARYOTYPE.—Unknown.

GEOGRAPHIC VARIATION.—Variation among the various island populations has been discussed in the section analyzing specimens from “Region 6—Trinidad, Tobago, Lesser Antilles.”

DISTRIBUTION.—The Lesser Antilles islands of St. Vincent, Bequia, Grenada, and the continental islands of Tobago and Trinidad (Figure 45; Appendix 2).

The Windward ditch frog or smooth-skinned ditch frog (Leptodactylus validus) is a species of frog in the family Leptodactylidae. It is found in the Lesser Antilles (Grenada, Saint Vincent and the Grenadines, and Trinidad and Tobago), the Guianas (French Guiana, Guyana, Suriname), and in the northernmost Brazil (Roraima) and in Venezuela. The Lesser Antillean part of the range might be due to human introduction. In 2018, the species was recorded from Colombia for the first time.

The continental Leptodactylus pallidirostris was found to be the same species as Leptodactylus validus in 2006. The former Leptodactylus pallidirostris is described as a dweller of gallery forests and forest edges. The Lesser Antillean populations are found in forests and forest edges often found close to forest stream banks, shaded gullies, and caves. They may also be found in meadows, at roadsides in parks and rural yards. The species lays its eggs in foam nests.

Male Leptodactylus validus grow to a snout–vent length of 28–43 mm (1.1–1.7 in) and females to 30–52 mm (1.2–2.0 in).