A new tree frog of the genus Scinax from the Vaupes River of northwestern Brazil.
In 1974 and 1976, I collected two series of small tree frogs in northwestern Brazil just north of the Vaupes River where this river forms the boundary between Colombia and Brazil. The frogs were calling at night from perches over water of flooded forest. The advertisement call of the frogs was recorded with a Uher 4000 Report-L tape recorder. Subsequent study of the specimens and analysis of the calls with a Kay Elemetric Sonagraph, model 6061B, led to the conclusion that the samples represented an unnamed species of hylid frogs in the genus Scinax. For this new frog I propose the name:
Scinax lindsayi, new species
Holotype. -- University of Texas at Arlington (UTA) A-4304, male, taken on the north side of the Vaupes River, in Brazil, about 3 km. NW Yapima, Vaupes, Colombia, on 21 July 1974 by Wanda C. Pyburn and the author. Yapima coordinates are: 69[degrees]28'W, 1[degrees]03'N.
Paratypes. -- UTA A-4301-03, 4308 same data as for holotype; UTA A-4275-77, 4289-90 collected July 1974, other data as for holotype; UTA A-34491, 34493-97, 34499-508, 34510-517 collected April 1976, other data as for holotype; UTA A-34492, 34498, 34509, females, other data as for holotype.
Diagnostic characters. -- Scinax lindsayi (Fig. 1) is a small (snout to vent length of males about 24 mm), arboreal tree frog that is capable of blanching or darkening its dorsal color according to its microenvironment and local light conditions. Live frogs in the pale color phase have a greenish-gray dorsum, usually with darker gray brown mottlings and spots. There are no longitudinal stripes. In the dark phase, the dorsal markings are obscured. The anterior and posterior surfaces of the thighs are uniformly dark brown, the gular skin of males is yellow and the iris is pale bronze. There is no red stripe through the eye. The fingers have little or no webbing. Extent of webbing between the toes varies from basal between the first and second toes to extending about three fourths of the way along the length of the fourth toe. The advertisement call of the male is a series of short, untrilled notes uttered from a perch above water. Males have a prominent vocal pouch that tends to be bilobed. They have no nuptial pads or excrescences on the fingers.
[FIGURE 1 OMITTED]
Description of holotype. -- An adult male with slender body about equal in width to width of head; snout rounded in both lateral and dorsal view and extending slightly beyond lower jaw; canthus and loreal concave; nostrils lateral (slightly dorsal) at anterior end of canthus; eye-nostril distance nearly equal to eye length; palpebrum clear except for free edge; tympanum circular, its diameter slightly less than half length of eye opening.
Dorsum, chest, and gula smooth; belly skin granular; vocal sac prominent tending to be bilobed when inflated; an incomplete chest fold, folds of skin at wrist, knee and heel; axillary membrane small. Fingers slender with well-formed, circular to subtruncate discs; width of third finger disc equal to diameter of tympanum; basal web between second and third and third and fourth fingers; no web between first and second fingers; relative lengths of fingers: 3 > 4 = 2 > 1; palmar and thenar tubercles moderately developed; one prominent, rounded subarticular tubercle on each finger; first finger with a slight basal enlargement; no prepollical spines or nuptial pads.
Adpressed leg places heel at posterior margin of eye; tibia length about one half that of snoutvent; inner metatarsal tubercle elliptical, about equal in area to disc of first toe; outer metatarsal tubercle inconspicuous, smaller than the rounded to subconical subarticular tubercles of toes; toe discs elliptical to nearly circular, slightly smaller than discs on outer three fingers; a basal web between first and second toes, extending as a fringe along inner margin of second toe; webbing between other toes variable from near distal end of antepenultimate phalanx of digit four to distal end of penultimate phalanx of digit five. Vocal slits large, extending from beneath postero-lateral margin of tongue to near jaw angle; tongue with a shallow posterior notch; vomerine teeth in two well-separated, transverse rows between posterior halves of obliquely elliptical choanae.
In life, dorsal ground color at night dull yellowish gray becoming light yellowish or pinkish gray by day; irregular, dark brown spots and blotches on back, dark brown canthal and postocular stripes and dark brown bars on limbs; at times during day darkening dorsal ground color obscured dorsal markings; gular skin chrome yellow, belly white with two bluish bands extending posteriorly from midbelly; lower surfaces of limbs with a translucent, bluish cast; posterior surfaces of thighs uniformly dark brown; iris pinkish bronze.
In preservative, dorsum medium gray with irregular dark brown spots and blotches; brown triangle between the eyes and brown canthal and postocular stripes; irregular brown bars or spots on upper surfaces of limbs, fingers and toes; posterior and anterior surfaces of thighs uniform brown; entire venter translucent cream gray.
Measurements of holotype (mm): snout-to-vent length (SVL), 25.4; head length, 8.9; head width, 8.3; tibia length, 12.5; eye opening length, 3.0; tympanum diameter, 1.3; eye to nostril, 3.0; nostril to tympanum, 6.7; width of third finger disc, 1.3; width of fourth toe disc, 1.2.
Variation. -- In preservative, the paratypes vary from pale gray with small brown spots on the back and brown bars on the limbs to dark gray-brown with darker markings on the back and limbs. Some specimens have a dark brown transverse line above the vent. Otherwise the paratypes closely resemble the holotype.
Measurements in millimeters of 34 males in the type series are (mean followed by one standard deviation): SVL, 23.8 [+ or -] 1.17; head length, 8.3 [+ or -] 0.49; head width, 7.5 [+ or -] 0.42; tibia length, 11.7 [+ or -] 0.58; eye length, 3.0 [+ or -] 0.25; tympanum diameter, 1.2 [+ or -] 0.16; eye to nostril, 2.7 [+ or -] 0.32; width third finger disc, 1.3 [+ or -] 0.19; width fourth toe disc, 1.2 [+ or -] 0.20. Measurements of three females in the type series are (mean followed by range): SVL, 26.3 (25.0-27.7); head length, 9.7 (9.2-10.0); head width, 8.4 (7.9-8.8); tibia length, 13.3 (12.8-13.6); eye length, 3.4 (3.1-3.6); tympanum diameter, 1.8 (1.6-1.9); eye to nostril, 3.3 (3.0-3.5); width third finger disc, 1.5 (1.4-1.5); width fourth toe disc, 1.4 (1.4-1.5).
Advertisement call. -- The advertisement call (Fig. 2) of Scinax lindsayi consists of short, loud, poorly tuned, untrilled notes uttered from perches on leaves and branches 15 to 50 centimeters above the water of flooded forest, air temperature about 24[degrees]C. Audiospectrograms of 11 call notes of three individuals showed a dominant frequency band at about 2895 Hz (range, 2695 to 3235 Hz), measured to the midpoint of the band width, and a poorly defined secondary band at about 4630 Hz (range, 4390 to 5005 Hz), also measured to the midpoint of the band. The dominant frequency band was about 700 Hz wide. Ten notes of two individuals had a mean duration of 0.09 second (range, 0.08 to 0.10 second). Nineteen notes of one frog timed with a stop watch had a repetition rate of 12 notes per minute. Another individual uttered 28 notes in three minutes, or 9.3 notes per minute.
[FIGURE 2 OMITTED]
Behavior. -- Scinax lindsayi often sits vertically with head directed downward and is difficult to approach even when illuminated at night. Upon slight disturbance it may dart about, hiding in dense vegetation or escape by plunging into turbid water. Duellman (1978:139) observed similar behavior in S. cruentomma. I also have seen this elusive, darting behavior in Scinax ruber, S. wandae, S. blairi, S. rostrata, and S. kennedyi.
Comparisons. -- Scinax lindsayi is a small member of the Scinax x-signata species group as that group is presently understood (see Fouquette and Delahoussave, 1977; Pombal and Gordo, 1991; Duellman and Wiens, 1992). Among members of the S. x-signata group S. lindsayi most closely resembles S. cruentomma (Duellman, 1972) in size, form, and color pattern, although cruentomma is slightly larger (SVL of males 26.4 [+ or -] 0.76 mm). Scinax lindsayi differs from S. cruentomma in lacking a red streak through the eye, in having a brown, rather than green, postfemoral skin color, and in advertisement call. The call note duration on lindsayi (Fig. 2) is about one fourth that of cruentomma: 0.09 second in lindsayi (air temperature ca. 24[degrees]C); 0.36 second in cruentomma and the note repetition rate is much faster in lindsayi (nine to 12 per minute) than in cruentomma (four per minute). Both S. lindsayi and S. cruentomma are unstriped.
Other small, unstriped species in the Scinax x-signata group with which S. lindayi might be confused are Scinax boesemani (Goin, 1966), S. x-signata (Spix, 1824), and S. crospedospila (A. Lutz, 1925).
Scinax boesemani (SVL of males 27 to 32 mm) is a savana species (Hoogmoed and Gorzula, 1979) of Suriname and Amazonian Brazil. It was compared by Goin (1966) with Hyla leucophyllata, a species to which it is apparently unrelated. The voice of S. boesemani was recorded by Duellman (1986) at Belem, Brazil (air temperature 27[degrees]C). The advertisement call of boesemani has a dominant frequency band at about 1270 Hz and the notes are pulsed, the pulse rate being 60 to 65 pulses per second. The call notes of S. lindsayi are unpulsed and the dominant frequency is about 2895 Hz.
Scinax x-signata is a savanna species (Hoogmoed and Gorzula, 1979) widespread in northern South America, which, in its various forms, ranges from 29 to 39 mm in SVL. Its morphology has been described by B. Lutz (1973), Cei (1980), and Gallardo (1961) among others. Scinax x-signata differs from S. lindsayi in having a dorsal pattern of x-shaped marks, a reticulated pattern or a pattern of dark anastomosing spots on the posterior thigh surface and a pustular dorsal skin. Scinax lindsayi has none of these characters.
Scinax crospedospila (25 to 32 mm SVL) is known from the coastal mountains of Rio de Janeiro and Sao Paulo in southeastern Brazil (Frost, 1985). It differs from S. lindsayi in having a series of elongate, paired dorsal spots (B. Lutz, 1973) and a pair of external vocal sacs (Cochran, 1954). The vocal sac of lindsayi tends to be bilobed but it is single.
Two species assigned to other species groups, although morphologically similar to Scinax lindsayi, are S. danae (Duellman, 1986) and S. blairi (Fouquette and Pyburn, 1972).
Scinax danae (SVL of males 24 to 28 mm) is a Venezuelan cloud forest species placed by Duellman (1986) in the S. staufferi species group. It has yellow flanks with brown spots and a median, subgular vocal sac. The call of S. danae, recorded by Duellman at an air temperature of 16[degrees]C, has a dominant frequency band at 1700 to 1800 Hz (2695 to 3235 Hz in lindsayi), a note repetition rate of 18 to 20 notes per minute (nine to 12 notes per minute in lindsayi and a note duration of 0.20 to 0.22 second (0.08 to 0.10 second in lindsayi).
Direct comparison of the advertisement calls of S. danae and S. lindsayi, recorded at markedly different temperatures, could be misleading owing to the influence of temperature on vocal properties. It has been shown that, in Pseudacris, note repetition rate increases with an increase in temperature, whereas note duration is negatively correlated with temperature (Bellis, 1957). In Bombina variegata, note repetition rate and frequency increase with an increase in temperature whereas call duration decreases with a rise in temperature (Zweifel, 1959). However, Barrio (1963) found no correlation between temperature and dominant frequency in Scinax squalirostris (see also Cei, 1980:33). In this regard, it is to be noted that although the call of S. danae was recorded at a lower temperature than that of S. lindsayi, the note repetition rate was much faster in danae. The dominant frequency in the call of lindsayi was about 1000 Hz higher than in danae.
Scinax blairi (SVL of males 27 to 30 mm), a member of the S. ruber group, from the llanos and ecotone of central Colombia, has lightly pigmented posterior thigh surfaces (dark brown in lindsayi). The individual call notes of blairi (Fig. 2) resemble those of lindsayi but the notes of blairi are somewhat longer and the note repetition rate is much faster: about 117 notes per minute (air temperature 24.0[degrees]C) in blairi; nine to 12 notes per minute in lindsayi.
The new species is named for Hague L. Lindsay, Jr., in recognition of his contributions to a knowledge of anuran relationships through his work in experimental hybridization. I am indebted to the late W. Frank Blair and the Evolutionary and Ecological Diversity section of the International Biological Program for financial support. Wanda C. Pyburn, as always, helped with every phase of the work. A local villager, known to me only as Herman, was especially helpful in obtaining the recordings by adroitly maneuvering a small and otherwise unstable canoe while Wanda or I held the microphone or captured a frog.
Nathan and Carolyn Waltz, of the Instituto Linguistico de Verano, were gracious hosts during our stay at Yapima. Edmund D. Brodie, Jr., Jonathan Campbell, Norris Gilfillan, and George Stewart gave valuable assistance and encouragement, for which I am most grateful. Darrel Frost generously allowed me to examine his unpublished manuscript dealing with the systematics of hylid frogs. Eduardo Valdarrama of INDERENA gave permission to collect specimens in the vicinty of Yapima. Special thanks are due Belinda Zollotuchen for typing the manuscript from my sometimes illegible hand.
The following persons permitted me to examine specimens in their care: Jonathan Campbell, University of Texas at Arlington; William E. Duellman, University of Kansas; Arnold Kluge, University of Michigan; Edgar E. Williams, Harvard University.
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WILLIAM F. PYBURN
Department of Biology, The University of Texas at Arlington, Arlington, Texas 76019
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|Author:||Pyburn, William F.|
|Publication:||The Texas Journal of Science|
|Date:||Nov 1, 1992|
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