Scarthyla vigilans ( Solano, 1971 ) Solano, 1971

Barrio-Amorós, César Luis, Pascual, Amelia Díaz De, Mueses-Cisneros, Jonh Jairo & Chacón, Edwin Infante Andrés, 2006, Hyla vigilans Solano, 1971, a second species for the genus Scarthyla, redescription and distribution in Venezuela and Colombia, Zootaxa 1349, pp. 1-18 : 3-14

Scarthyla vigilans ( Solano, 1971) new combination

Fig 1

Hyla squalirostris: Cochran and Goin 1970: 236 . Misidentification.

Hyla vigilans Solano 1971: 212 Original description.

Hyla vigilans: Frost 1985: 157 Association of the species with Ololygon (La Marca, pers. com. to Frost) but new combination never presented.

Hyla vigilans: La Marca 1992: 57 . Venezuelan listing and geographic distribution.

Hyla vigilans: Mijares-Urrútia and Hero 1997: 585 . Tadpole description.

Hyla vigilans: Barrio-Amorós 1998: 34 . Venezuelan listing and geographic distribution.

Hyla vigilans: Suárez-Mayorga and Lynch 2001: 116 . Tadpole description.

Hyla vigilans: Barrio-Amorós 2004: 16 . Venezuelan listing and geographic distribution.

Hyla vigilans: Faivovich et al. . 2005: 111. Incertae sedis.

Holotype: MBUCV IV- 6163, from the road Coloncito to El Vigía, estado Zulia

[sic!=Mérida], Venezuela.

Diagnosis: Scarthyla vigilans is distinguished from other hylids by the following combination of characters: (1) small SVL (up to 21 mm); (2) acuminate snout projecting beyond margin of lip, (3) tympanum distinct, approximately half diameter of ED; (4) hind limbs long, reaching nostrils when adpressed to saggital plane; (5) fingers unwebbed; (6) toes nearly fully webbed; (7) coloration in preservative pale brown to dark brown dorsally with darker longitudinal markings and dark brown upper lateral stripes; in life, lime green at night, at day pale brownish with contrasting or not longitudinal stripes; bones green in life and in recently preserved specimens. Differences between the two species of the genus are highlighted in the discussion. All Scinax have a reduced or complete lack of webbing between Toes I and II, whereas Toes I and II are fully webbed in Scarthyla .

Description: We base our description on 21 adults (SVL= 15 mm) (see Appendix) from the Maracaibo Basin, where the type locality is. Body elongate, slender; head as wide as body, longer than wide; head length 33–42 % of SVL; head width 26–30.8 % of SVL; snout long, acuminate in dorsal and lateral views, projecting well beyond margin of lip; nostrils about 2/3 distance from orbit to tip of snout, slightly protuberant laterally; internarial area slightly concave to flat; canthus rostralis rounded; loreal region barely concave; lips rounded; interorbital area flat, much wider than UEW; IOD 38–46 % of HW; UEW 32–46 % of HW; eye moderately large, protuberant; pupil round, palpebrum clear, tympanum round, TD 42–66% of ED, situated posteroventral to eye, separated from eye by distance equal to half TD; tympanic annulus distinct except on the supero-posterior part, obscured by a diffuse supratympanic fold. Axillary membrane absent; arm moderately slender; ulnar fold and tubercles absent; fingers slender with narrow lateral fringes extending to small round discs ( Fig 3); FD equal to 45–70 % TD; relative length of fingers 1<2<4<3; webbing absent; subarticular tubercles small, round, largest on Finger IV; supernumerary tubercles minute, round, in single rows from subarticular tubercles; palmar tubercle low, flat, deeply bifid distally; thenar tubercle low, flat, elliptical; nuptial excrescences absent. Hind limbs slender; tibia length 50–55 % of SVL; foot length 45–50% of SVL; inner tarsal fold absent; outer metatarsal tubercle small, round, flat, half size of inner metatarsal tubercle, indistinct in some specimens; inner metatarsal tubercle small, nearly round; toes slender with small round discs, slightly smaller than those of fingers; relative lengths of toes 1<2<3=5<4; webbing extending to bases of discs on all toes except only to base of penultimate phalange of Toe IV; subarticular tubercles small, round; supernumerary tubercles indistinct, minute, present only on proximal segments ( Fig 4).

Cloacal opening directed posteriorly at upper level of thighs; cloacal sheath and anal tubercles absent; skin on belly and proximal posteroventral surfaces of thighs granular; skin on other surfaces smooth. Tongue oval to slightly cordiform, not notched posteriorly, free behind for about 1/3 of its length; dentigerous processes of vomers small, each bearing 3–5 teeth; in males, vocal slit extending from midlateral base of tongue to angle of jaw; vocal sac single, median, subgular.

Coloration in preservative: dorsum pale brown or pale gray to dark brown or bluish brown, without apparent longitudinal stripes (15%) or with more or less distinct stripes (85%). Three longitudinal stripes, darker than background, usually dark brown, one vertebral, two dorsolateral. Dark brown (sometimes blackish) canthal and supratympanic stripes; supratympanic stripe can extend to above arm or continue to near groin. Hind limbs can be patternless or bearing diffuse markings, like faint spots. Ventral parts creamy white in males, in females white with a few black melanophores (only distinguished by microscope) on throat and chest, immaculate on belly. Iris black or golden, depending on preservation artifacts.

Coloration in life: At night, lime green, stripes indistinct, bones pale green; ventral parts transparent. During the day ( Fig. 1 ) the colour is more contrasting. The vertebral line is usually narrower than the dorsolateral ones, and can be surrounded by a narrow whitish line. On the head, the vertebral line can open and form a triangle with the widest part between the interorbital region. Iris bronze, pupil black.

Variation: Little variation has been observed. Specimens from Santa María de Caparo (Los Llanos bioregion) have smaller tympanum (30% of ED vs. 50% of individuals from the Maracaibo lake).

Osteology: The osteological description is based on MBLUZA–295, a male from Laguna Los Palitos, Sur del lago, Municipio Catatumbo, estado Zulia.

The skull is longer than wide, well ossified; the dorsal surfaces ( Fig. 5 ) are smooth and lack exostosis, casquing or co-ossification with the overlying dermis. The nasals are moderately large, triangular, anteriorly separated from the alary processes of the premaxillae by the nasal cartilages. The nasals converge, but do not meet, anteriomedially. Medially, the nasals overlap the lateral margin of the sphenethmoid, and they are almost completely fused with the sphenethmoid. Posteriorly, the nasals are widely separated from the frontoparietals by the ossified sphenethmoid. The frontoparietals are well developed, rectangular, and lack a supraorbital shelf. The medial margins of the frontoparietals are narrowly separated from one another. The frontoparietal fontanelle is covered by the frontoparietals. Posteriorly, the frontoparietals cover the prootics.

The sphenethmoid is well ossified; not fused posterolaterally with the prootic like in S. goinorum . The prootics are well ossified and fused with the exoccipitals. The prootic foramen is moderately large and has a complete bony margin. One smaller foramina lies between the optic and prootic foramina. The exoccipitals are well ossified. The crista parotica is short and seems cartilaginous distally.

Ventrally ( Fig. 6 ), the parasphenoid is triradiate and smooth. The cultriform process is long and terminates in a sharp tip at the same level of palatines. The parasphenoid alae are narrowly triangular, sharp, and oriented horizontally. The parasphenethmoid is covered anteriorly by the sphenethmoid, and covered posteriorly by the prootic and exoccipitals. The vomers are moderately large and have ovoid, straight odontophores, bearing four teeth each. The neopalatines are sharp and moderately long (barely surpassing the sphenethmoid). The pterygoids are triradiate and slender; the anterior ramus articulates with the maxilla, and the posterior ramus articulates with the squamosal at the level of the angle of the jaw. The medial ramus of the pterygoid has a ligamentous attachment to the anteroventral surface of the otic capsule.

The maxillary arches are complete. The premaxillae are separated medially and bear well-developed alary processes that are slightly inclined anteriorly. The partes palatinae and palatine processes are moderately well developed. The maxillae lack pre- and postorbital processes. The quadratojugal is well ossified. Anteriorly, the dentaries are fused, with the Mentomeckelian bones.

The presacral vertebrae ( Fig. 7 ) lack neural arches. The transverse processes of all vertebrae are subequal in length, those on presacrals II, III, and VII are oriented transversely, whereas those on presacrals IV –VI are inclined posteriorly, and those on presacral VIII are curved anteriorly. The sacral diapophyses are dilated slightly and in section are more or less cylindrical. The urostyle is moderately short (just a bit less than the total length of column without urostyle) and has a low ridge dorsally basal. Compared with the vertebral columna of S. goinorum (in which the figures of Duellman and De Sá (1988) are reversed), the principal difference is the length of the transverse processes of the vertebrae, being in S. vigilans much longer and the vertebrae much more robust and ossified.

The phalangeal formula for the hand and foot is 2-2-3-3 and 2-2-3-4-3, respectively. The intercalary element between the penultimate and distal phalanges is completely ossified.

Vocalization and calling behavior: We analysed two series of calls, one from close to the type locality of Scarthyla vigilans ( Fig. 8 ), and other from Los Llanos region, east of the Andes (unfortunately, this last call is too dirty to provide a clear audiospectrogram). The call from the Maracaibo lake area (Finca Onia, 9 km from El Vigía to Colón, estado Mérida) is like a cricket chirp, very low in intensity, each call has between 5 to 6 notes, the first three or four notes have a duration from 0.273 to 0.290 sec, the two other notes are separated by 0.094 sec from the first group of four; the duration of the entire call is 0.35 sec. The separation between calls emitted by the same frog vary from 0.5 sec to 2 sec. The dominant frequency is at 4700 Hz, and the fundamental at 3800 Hz. Another recording from Ologá (not represented), also in the Maracaibo lake, is interesting for showing two more different call types. One is consisting in only two notes, with a total duration of 0.088 sec, with a dominant frequency of 4000 Hz (fundamental at 3400); and another call consisting in four notes, with a total duration of 0.42 sec, a dominant frequency of 4800 Hz and a fundamental frequency of 3800 Hz.

The call from near Santa María de Caparo, estado Mérida, in Los Llanos bioregion, is very similar to the one from Finca Onia, with the following variations: the sequence of a single call is a series of six to seven notes, with a duration of about 0.2 sec. There is a group of five notes close together barely separated from the last two. The dominant frequency is lower than the Finca Onia sample, but equal to Ologá sample, at 4000 Hz, and the fundamental frequency is at 3400 Hz. Because the animals of both populations are identical, we consider that the differences between the calls represent intraspecific variation.

Scarthyla vigilans has been unknown from Los Llanos region for a long time ( La Marca 1992, Barrio-Amorós 1998, Péfaur and Rivero 2000), although Barrio-Amorós (2004) mentioned it from there without precise locations, we believe this is due mainly because of its low call, seemingly like a cricket to untrained ears, and obscured by other sympatric hylids ( Dendropsophus microcephalus , D. minusculus and Pseudis paradoxa ), all calling with a much higher intensity.

However, S. vigilans is easily detectable some nights when other species are not so active. For instance, the night of 16 of July 2002, in San Vicente, estado Apure, just a few D. microcephalus and no D. minusculus were calling in a pool where S. vigilans was very active. S. vigilans also calls actively during the day, as we observed in pools and marshes around San Vicente (estado Apure) during the wet season (June to November), and along the channels of Puerto Concha (estado Zulia) (also from June to November).

Natural History: Scarthyla vigilans is a small, inconspicuous species, despite being very abundant. It inhabits marshes, channels, ditches, slow-movement rivers and streams, lakes and even brackish coastal areas of the Maracaibo lake. Calling males are more often seen, as they call from high in the grasses or leafs on floating plants (water hyacinths, water lettuces, etc.), and jump quickly to escape. Females are larger and stay at lower stages on the same plants. S. vigilans , like S. goinorum , can escape jumping to the water and skittering on the surface (Duellman and De Sá 1988; Duellman 2005). One ovigerous female at San Vicente, estado Apure, laid 95 bicolored ova.

During dry season they usually remain undetectable (not calling at all), but the first author, while searching for anacondas ( Eunectes murinus ) on March 2006, at 1300 h, in a dry pond with still green water hyacinths, observed uncountable S. vigilans jumping and escaping through all the pond.

In La Acequia, Barinas, the species is micro-sympatric with Dendropsophus microcephalus , Hypsiboas crepitans , H. punctatus , Scinax x-signatus , S. wandae , Elachistocleis aff. ovalis, Leptodactylus sp., Physalaemus cf. fischeri, Engystomops pustulosus , and Trachycephalus venulosus .

In San Vicente, Apure, it is only micro-sympatric with Dendropsophus microcephalus , D. minusculus, Hypsoboas punctatus , and Pseudis paradoxa .

In the Maracaibo lake, Zulia, it is micro-sympatric with Dendropsophus microcephalus , Hypsiboas pugnax , Pseudis paradoxa , Leptodactylus sp., Trachycephalus venulosus , Elachistocleis aff. ovalis, and Physalaemus pustulosus ; and syntopic with Pipa parva .

Distribution and biogeography: Since its description to very recently, Scarthyla vigilans was conceived to be an endemism of the Maracaibo lake basin in NW Venezuela, and reported formerly only in 1996 from Colombia by Ruíz-Carranza et al. (1996) (although it was mentioned already as Hyla squalirostris by Cochran and Goin 1970), where it is widely distributed especially in its northern part. Barrio-Amorós (1998) provided the distribution in Venezuela based on Maracaibo lake basin registers. Mijares et al. (1998) reported the species from Falcon state, further east than previously expected, and H.P. Reinthaler (in an unpublished thesis) cited it from Caparo, Estado Mérida (eastern side of the Cordillera de Mérida), in Los Llanos bio-region. We recorded the species from Santa Maria de Caparo, and note herein its presence at San Vicente, Estado Apure, and from río Acequias, and Sabanas de Anaro, Estado Barinas, as first state records (see appendix). Uribe et al. (1994: 36) show a photograph of S. vigilans as Hyla microcephala from somewhere in the Colombian Llanos. Finally, Renjifo and Lundberg (1999) report the species from the Urrá dam area, at Departmento de Córdoba, Colombia. Barrio- Amorós (1998) in assigning the first Trujillo specimens, missed that Solano (1971) already mentioned paratypes from that state.

We present herein 46 localities for this species in Colombia and 31 in Venezuela (Fig 9).

FIGUR E 9. Distribution map of Scarthyla vigilans in northern South America. The black line is the approximate border between Colombia (to the west) and Venezuela. The black bar scale is equal to 200 km. One dot can represent more than one locality. Map of South America elaborated by JPL. Available at http://photojournal.jpl.nasa.gov/catalog/PIA03388

So far, the general distribution of S. vigilans includes the NW part of Venezuela (estados Zulia, Mérida, Táchira, Trujillo, Yaracuy, and Falcón) and north of Colombia (departamentos Antioquia, Atlántico, Bolívar, Córdoba, Norte de Santander, and Sucre); and Los Llanos of Venezuela and Colombia (Apure, Barinas and Mérida in Venezuela; Arauca in Colombia). Barrio-Amorós (2004) gave an altitude range from 0 to 200 m; the locality “Hacienda Tesoro Escondido” in Mérida state lays at 600 m.

Because its apparent inconspicuousness, it is evident that the species has been missed in many herpetological surveys in Los Llanos ( Fouquette 1968; Staton and Dixon 1977; Ramo and Busto 1989 –1990; Péfaur and Díaz de Pascual 1987), and that in the future, many new localities will be reported. We presume the presence of Scarthyla vigila ns at least through the western Llanos (Táchira, Portuguesa, Guárico, Cojedes states), and north-western states (Carabobo, Lara). In Colombia, its distribution must be continue to the Colombian Llanos (at least in Departamentos Casanare, Vichada, and Meta). In some part of the Amazon-Llanos ecotone in Colombia both species of Scarthyla could be sympatric.

A few amphibian species are known to occur at both sides of the Cordillera de Mérida in Venezuela. The known distribution of Scarthyla vigilans has no parallel in other species. Only widespread species like Chaunus marinus , Dendropsophus microcephalus , Hypsiboas pugnax , Pseudis paradoxa , Scinax “ x-signatus ”, S. rostratus , Trachycephalus venulosus , Leptodactylus bolivianus , L. fuscus , and Elachistocleis “ ovalis ”, are known to inhabit the Maracaibo lake basin as well as Los Llanos or further east (Barrio-Amorós 2004). Two biogeographical cases are of interest. Leptodactylus lineatus was formerly known from the Amazon basin and Guianas ( Barrio-Amorós 1998; Lescure and Marty 2000), but recently reported from the Maracaibo basin by Barros and Barrio (2001). Both populations are clearly conspecific and we can not argue at this point about the biogeographic reasons for such distribution. Ceratophrys calcarata is known from northwestern Venezuela, including the Maracaibo lake basin, (usually in arid habitat), and further west to at least departamento de Córdoba in Caribbean Colombia ( Barrio-Amorós 1998, 2004; Renjifo and Lundberg 1999); a relict population occurs in the surroundings of Puerto Ayacucho, close to the shore of the Orinoco river (estado Amazonas, Venezuela). This last species (excluding the Orinoquian locality) has the most similar distribution pattern to Scarthyla vigilans , even though Ceratophrys calcarata is absent from los Llanos, and that each species inhabit different microhabitats.

Discussion: Scarthyla vigilans is morphologically and osteologically very similar to S. goinorum . Scarthyla vigilans share with S. goinorum the following characters: (1) nasals large, rounded, with maxillary processes not articulating with maxillae; (2) sphenethmoid ossified, separating nasals and frontoparietals; (3) frontoparietals narrowly separated medially, obscuring frontoparietal fontanelle; (4) squamosal slender; (5) alary processes of premaxillae inclined anteriorly; (6) maxillary arch complete; (7) transverse processes on presacral IV moderately long, inclined posteriorly; (8) sacral diaphyses moderately expanded; (9) intercalary elements between distal and penultimate phalanges ossified. Faivovich et al. (2005) did not presented any synapomorphy for the then monotypic genus. Adding Hyla vigilans to Scarthyla , we either are aware of any synapomorphy within this genus. Even though no synapomorphies are shared by both species, the fact that both are virtually indistinguishable morphologically and osteologically, makes a convincing case to consider Hyla vigilans as a second species of Scarthyla .

Although the original description of Scarthyla ostinodactyla (= goinorum ) by Duellman and de Sá (1988) is clear in observing the presence of an “inner tarsal fold […] on distal 2/3 of tarsus”, one of us (JMC) did not observed this character in Colombian specimens assigned to the species (see appendix). These can be due to the fact of the specimens from Colombian Amazonia also could represent S. vigilans , and then, the only striking difference between both species would be the larval characters.

Only calls and tadpoles are enough dissimilar between the two species. Call in S. goinorum (as S. ostinodastyla ) was described as series of 8–10 short, whistle-like notes, being the interval between notes of 0.3 sec, and the duration of each note 0.04 sec. The dominant frequency is at 6000 Hz (Duellman and de Sá 1988) (see the call of S. vigilans above)

The tadpole of S. vigilans was described by Mijares and Hero (1997) and Suárez- Mayorga and Lynch (2001). Its principal characteristics are: larvae small (TL mean 26.4 mm, maximum TL 31.5), body short, globular, anteriorly subacuminate in lateral view and rhomboidal anteriorly, rounded from above; spiracle sinistral, directed ventrolaterally, attached to body; vent tube medial; tail moderately long, compressed, distally forming a long, rounded tip; dorsal fin shallower than ventral fin, but fin shapes making tail apparently symmetrical; tail musculature weak. Oral disk small, with labial papillae prominent; labial tooth formula 2 (2) / 3 (1); jaw beaks well keratinised, finely serrated. Coloration in life with a remarkable zebra-like pattern of black or dark brown bars separated by translucent bars.

The tadpole of S. goinorum is quite unusual, small (TL up to 23.7 mm), body elongate, twice as long as wide, abruptly terminating posteriorly, eyes large; snout rounded in profile, body shallower than wide; spiracle sinistral, short, directed dorsally; vent tube dextral, short; tail very long, acutely rounded tip, dorsal fin shallower than ventral fin, but both much shallower than in S. vigilans , oral disk with flaplike labia with a single row of pointed serrations; labial tooth formula 2 (1+2)/ 2(1) (following Altig 1970). Beak moderately slender, V-shaped, with pointed serrations. Coloration in life, body yellowish green, tail pale green, both with brown markings.

Tadpoles of Pseudis paradoxa , P. cardosoi , and Lysapsus limellus are in overall dissimilar from those of S. goinorum and S. vigilans (respectively Emerson 1988 and Duellman 2005, Kwet 2000, and Kehr and Basso 1990).

Within Hylidae , Scarthyla shares ossified intercalary elements with Pseudis , Lysapsus , Sphaenorhynchus and Aplastodiscus . The former family Pseudidae Fitzinger, 1843 , was recently considered as a subfamily within Hylidae ( Duellman 2001, Haas 2003). Darst and Cannatella (2004) link closely Pseudis to Scarthyla based on mitochondrial sequences. Faivovich et al. (2005) corroborates that Scarthyla goinorum is nested with former pseudines within Hylinae. Pseudis and Lysapsus , with ossified intercalary elements, are otherwise completely dissimilar in external adult and tadpole morphology. The only external similarity between the tadpoles of Pseudis paradoxa caribensis and Scarthyla vigilans is the coloration of black transverse bands. It is outstanding the great difference between the tadpoles of both species of Scarthyla , and to date is not possible to discern the reason for that difference. In order to know if some confusion was made during the description of the tadpole of S. goinorum , the senior author asked William E. Duellman, who explained that tapoles were raised through its metamorphosis to confirm its identity. Genetic data is required to see how close are the two species of Scarthyla with each other and in relation with the former pseudines.

Figures

FIGURE 1. Male of Scarthyla nov. from Ologá, southwestern side of the Maracaibo lake. Photo by C. L. Barrio-Amorós.

FIGURE 5. Dorsal view of skull of Scarthyla vigilans, MBLUZ – 295. Scale equal to 5 mm.

FIGURE 6. Ventral view of skull of Scarthyla vigilans, MBLUZ – 295. Scale same as Fig 5.

FIGURE 7. Ventral (bottom) and dorsal (top) views of vertebral columnae of Scarthyla vigilans, MBLUZ – 295. Scale equal to 5 mm.

FIGURE 8. Audiospectrogram of Scarthyla vigilans calling at Finca Onia, near El Vigia, the type locality of the species. One call of the series is encircled to be distinguished from calls of other species.