Neotropical Hylid Frogs, Genus Smilisca Part 12

cyanosticta_ were calling on the same nights and less than 100 meters apart in Oaxaca in June, 1964. Regardless of their respective breeding habits, sympatric species have calls that differ notably. Except for the higher fundamental and dominant frequencies, the calls of _S.

cyanosticta_ and _S. phaeota_ closely resemble one another, but the calls of both species differ markedly from that of _S. baudini_. The geographic ranges of _S. cyanosticta_ and _S. phaeota_ are widely separated.

The calls of the allopatric species _S. puma_ and _S. sila_ are not greatly different. _Smilisca sordida_ has a distinctive call and occurs sympatrically with _S. puma_ and _S. sila_. In the streams in southern Costa Rica _S. sordida_ and _S. sila_ breed synchronously, but the high-pitched modulated call of the former is notably different from the lower, unmodulated call of _S. sila_.

The data indicate that the calls of related sympatric species differ more than the calls of related allopatric species. We postulate that these differences evolved to support the reproductive isolation of the sympatric species. The data are insufficient to determine geographic variation in the calls and to determine if differences in the calls are enhanced in areas of sympatry as compared with the allopatric parts of the ranges.

_Other calls._--As stated previously, there is no direct evidence of territoriality in _Smilisca_; we have heard no calls that can be definitely identified as territorial. Single notes of _S. baudini_, _phaeota_, and _sila_ have been heard by day, just prior to rains, or during, or immediately after rains. Such calls can be interpreted as "rain calls," which are well known in _Hyla eximia_ and _Hyla squirella_. Distress calls are known in several species of _Rana_ and in _Leptodactylus pentadactylus_; such calls result from the rapid expulsion of air over the vocal cords and with the mouth open. Distress calls have been heard from _S. baudini_. At Charapendo, Michoacan, Mexico, a male that had one hind limb engulfed by a _Leptodeira maculata_ emitted several long, high-pitched cries. A clasping pair of _S. baudini_ was found in a bush at the edge of a marshy stream 2 kilometers northeast of Las Canas, Guanacaste Province, Costa Rica. When the pair was grasped, the female emitted a distress call.

Eggs

Eggs of _S. baudini_, _cyanosticta_, and _phaeota_ have been found in the field, and eggs of _S. sila_ have been observed in the laboratory.

The eggs of _S. puma_ and _sordida_ are unknown. Insofar as known, _Smilisca baudini_ is unique in the genus in depositing the eggs in a surface film. Each egg is encased in a vitelline membrane, but individual outer envelopes are lacking. The eggs are small; the diameter of recently-deposited eggs is about 1.3 mm. and that of the vitelline membrane is about 1.5 mm. The eggs of _S. cyanosticta_ and _phaeota_ are deposited in clumps, and the eggs are larger than those of _S. baudini_.

Diameters of eggs of _S. cyanosticta_ are about 2.3 mm., and those of the outer envelopes are about 4.0 mm. Artificially fertilized eggs of _S. sila_ raised in the laboratory have diameters of about 2.4 mm.; the diameter of the outer envelopes is about 4.9 mm.

In order to determine the reproductive potential of the six species, ovulated eggs were removed from females and counted. The numbers of eggs recorded are: 3 _S. baudini_--2620, 2940, 3320; 1 _S. cyanosticta_--910; 3 _S. phaeota_--1665, 1870, 2010; 1 _S. puma_--518; 3 _S. sila_--369, 390, 473; 3 _S. sordida_--524, 702, 856. These limited data indicate that the large species (_S. baudini_, _cyanosticta_, and _phaeota_) have more eggs than do the smaller species. The stream-breeding species (_S.

sila_ and _sordida_) have relatively few eggs by comparison with the pond-breeders. Possibly this is a function of size of eggs rather than a correlation with the site of egg-deposition.

Tadpoles

The acquisition of tadpoles of all of the species of _Smilisca_ has made possible the use of larval characters in erecting a cla.s.sification and in estimating the phylogenetic relations of the several species.

Furthermore, developmental series of tadpoles of four species allow a comparison of the growth and development in these species. Throughout the discussion of tadpoles we have referred to the various developmental stages by the Stage Numbers proposed by Gosner (1960).

_General Structure_

Tadpoles of the genus _Smilisca_ are of a generalized hylid type, having 2/3 tooth-rows, unspecialized beaks, mouth partly or completely bordered by papillae, lateral fold present in the lips, spiracle sinistral, a.n.a.l tube dextral, and caudal musculature extending nearly to tip of caudal fin. Although minor differences exist in coloration, proportions, and mouthparts, no great modifications of the basic structure are present.

_Comparison of Species_

The larval characters of the species of _Smilisca_ are compared below and ill.u.s.trated in Figures 11-15.

_Shape and Proportions._--The bodies of _S. baudini_, _cyanosticta_, _phaeota_, and _puma_ are rounded and about as wide as deep; the eyes are moderately large and directed dorsolaterally, and the nostrils are about midway between the bluntly rounded snout and the eyes. The mouths are medium-sized and directed anteroventrally. The bodies of tadpoles of _S. sila_ and _sordida_ are slightly compressed dorso-ventrally. The snout is moderately long and sloping; the eyes are larger and directed more dorsally than in the other species, and the nostrils are closer to the eyes than the snout. The mouths are moderately large and directed ventrally.

The tail is about half again as long as the body in _S. baudini_, _cyanosticta_, _phaeota_, and _puma_; in these species the caudal musculature is moderately heavy, and the caudal fins are deep. The caudal musculature is upturned distally in _S. baudini_ and _phaeota_, and the dorsal fin extends anteriorly onto the body in these two species and in _S. puma_. The tail is about twice as long as the body in _S.

sila_ and _sordida_. In both species the caudal fins are shallow in comparison with the depth of the caudal musculature, especially in _S.

sordida_ (Fig. 14); in neither species does the dorsal fin extend anteriorly onto the body.

[Ill.u.s.tration: FIG. 11. Tadpoles of _Smilisca baudini_: (A) Stage 21 (KU 62155) 10; (B) Stage 25 (KU 68467) 5; (C) Stage 30 (KU 60018) 4; (D) Stage 41 (KU 60018) 3.]

_Mouthparts._--The mouth of _S. sordida_ is completely bordered by two rows of papillae, whereas in the other species the median part of the upper lip is devoid of papillae. _Smilisca baudini_ and _puma_ have two rows of papillae; _S. sila_ has one complete row (except medially on the upper lip) and one incomplete row, and _S. cyanosticta_ and _phaeota_ have only one row (Fig. 15). All species have numerous papillae in the lateral fold; the fewest lateral papillae are found in _S. cyanosticta_ and _phaeota_. Although all species have two rows of teeth in the upper jaw and three rows in the lower jaw, specific differences in the nature of the rows exist between certain species. The second upper tooth-row is narrowly interrupted medially in _S. sila_ and _sordida_ and broadly interrupted in the other species. The first upper row is strongly arched in _S. puma_, moderately arched in _S. baudini_ and _sila_, and weakly arched in the other species. In all species the third lower tooth-row is the shortest, only slightly so in _S. sila_ and _sordida_, but only about half the length of the second lower row in _S. puma_.

[Ill.u.s.tration: FIG. 12. Tadpoles of _Smilisca cyanosticta_: (A) Stage 21 (KU 87648) (B) Stage 25 (KU 87651) 5; (C) Stage 30 (KU 87652) 4; (D) Stage 40 (KU 87650) 3.]

The beaks are well developed and finely serrate in all species. The lower, broadly V-shaped, beak is slender in _S. puma_, rather robust in _S. baudini_ and _sila_, and moderately heavy in the other species. The lateral processes of the upper beak are shortest in _S. puma_ and longest in _S. baudini_ and _sordida_. In the latter the inner margin of the upper beak and lateral process have the form of a shallow S, whereas in the other species the inner margin of the upper beak forms a continuous arch with the lateral processes (Fig. 15).

[Ill.u.s.tration: FIG. 13. Tadpoles of _Smilisca phaeota_: (A) Stage 21 (KU 68479) 14; (B) Stage 25 (KU 68480) 5; (C) Stage 30 (KU 68482) 4; (D) Stage 40 (KU 68483) 3.]

_Coloration._--The tadpoles of _Smilisca_ lack the bright colors or bold markings characteristic of some hylid tadpoles; even so, the subdued colors and arrangement of pigments provide some distinctive markings by which the species can be distinguished from one another. The species comprising the _baudini_ group (_S. baudini_, _cyanosticta_, and _phaeota_) are alike in having the body brown or grayish brown dorsally and transparent with scattered brown pigment ventrally. A cream-colored, crescent-shaped mark is present on the posterior edge of the body; this mark is usually most noticeable in _S. baudini_ and least so in _S.

cyanosticta_. Other differences in coloration in members of the _baudini_ group are relative and subtle. _Smilisca phaeota_ usually is more pallid than _baudini_, and _cyanosticta_ usually is darker than _baudini_; both species have larger dark markings on the tail than does _S. phaeota_. _Smilisca baudini_ has a dark streak on the middle of the anterior one-fourth of the tail (Figs. 11-13).

_Smilisca puma_ is distinctive in having a grayish brown body and dark gray reticulations on the tail. _Smilisca sila_ and _sordida_ are distinctive in having pairs (sometimes interconnected) of dark marks on the dorsal surfaces of the caudal musculature, and in dorsal view the tail appears to be marked with dark and pale creamy tan transverse bars.

These dark marks, as well as the small flecks on the tail, are brown in _S. sila_ and red in _sordida_. _Smilisca sila_ has dark brown flecks on the dorsal surface of the body and small white flecks laterally; these markings are absent in _S. sordida_ (Fig. 14).

Descriptions of the coloration of living tadpoles are given in the accounts of the species.

[Ill.u.s.tration: FIG. 14. Tadpoles of _Smilisca_; (A) _S. puma_, Stage 30 (KU 91807); (B) _S. sila_, Stage 25 (KU 80260); _S. sordida_, Stage 30 (KU 68475). All 3.5.]

_Growth and Development_

Information on the growth and development of Middle American hylids is scanty. Adequate descriptions have been published for _Phyllomedusa annae_ (Duellman, 1963b), _Phrynohyas venulosa_ (Zweifel, 1964), and _Triprion petasatus_ (Duellman and Klaas, 1964). Material is available for adequate descriptions of the developmental stages of four species of _Smilisca_ (Tables 9-12, Figs. 11-13). Because none of the tadpoles was raised from hatching to metamorphosis, the rate of growth and duration of the larval stages are unknown.

[Ill.u.s.tration: FIG. 15. Mouthparts of tadpoles of _Smilisca_; (A) _S. baudini_ (KU 60018); (B) _S. puma_ (KU 91807); (C) _S. cyanosticta_ (KU 87625); (D) _S. sila_ (KU 80620); (E) _S. phaeota_ (KU 68482); (F) _S. sordida_ (KU 68475).

All 17.]

Table 9.--Growth and Development of Tadpoles of Smilisca baudini.

(Means Are Given in Parentheses After the Observed Ranges.)

==================================================================== Stage | N | Total length | Body length | Tail length -------------------------------------------------------------------- 21 |10 | 5.1-5.4 (5.22) | 2.6-2.7 (2.54) | 2.5-2.7 (2.58) 24 |10 | 6.0-6.5 (6.20) | 2.3-2.6 (2.45) | 3.5-3.9 (3.69) 25 |10 | 7.2-8.3 (7.78) | 3.0-3.3 (3.14) | 4.2-5.0 (4.64) 27 |10 | 18.5-21.5 (20.22) | 8.0-9.0 (8.38) |10.4-13.0 (11.84) 29 |10 | 21.5-24.5 (22.60) | 8.5-10.0 (9.25) |12.5-14.5 (13.35) 37 | 3 | 28.5-31.0 (30.00) |11.0-12.5 (11.67) |17.5-19.0 (18.00) 38 |10 | 35.0-37.5 (35.50) |12.0-13.5 (12.80) |21.5-24.0 (22.70) 40 | 2 | 34.0-37.0 (35.50) |12.5-13.5 (13.00) |21.5-23.5 (22.50) 41 |10 | 34.0-37.0 (35.50) |12.5-13.5 (13.00) |21.5-23.5 (22.50) 42 | 3 | 24.0-30.0 (27.00) |12.5-13.0 (12.67) |11.5-17.0 (14.33) 45 | 6 | 14.0-24.0 (17.58) |12.5-14.0 (13.37) | 1.5-10.0 (4.17) 46 |23 | ---- |12.0-15.5 (13.34) | ---- --------------------------------------------------------------------

Table 10.--Growth and Development of Tadpoles of Smilisca cyanosticta. (Means Are Given in Parentheses After the Observed Ranges.)

====================================================================== Stage | N | Total length | Body length | Tail length ---------------------------------------------------------------------- 21 | 10| 5.8-6.5 (6.28) | 2.8-3.1 (3.00) | 3.0-3.5 (3.28) 25 | 10| 7.9-9.2 (8.44) | 2.7-3.2 (2.96) | 4.8-6.0 (5.48) 30 | 7| 22.5-25.0 (23.50) | 8.5-9.5 (9.00) |14.0-15.5 (14.57) 36 | 10| 27.0-30.0 (28.75) | 9.5-11.5 (10.80) |17.0-18.5 (17.95) 42 | 2| 26.0-27.0 (26.50) | 10.00 |16.0-17.0 (16.50) 46 | 2| -- | 14.00 | -- ----------------------------------------------------------------------

Hatchlings of three species (_S. baudini_, _cyanosticta_, and _phaeota_) are available. These larvae have non-functional eyes and large oral suckers. By the time the larvae have developed to stage 21, external gills are present, the caudal musculature and caudal fin have been differentiated, and the head is distinguishable from the body. In stage 21 oral suckers and a large amount of yolk are still present.

The developmental data on the four species show no significant variations; consequently, we will describe the development of only one species, _Smilisca phaeota_ (Table 11, Figs. 13 and 16).

_Stage 21._--Bulging cream-colored yolk ma.s.s, transparent cornea, and moderately long, unbranched filamentous gills, and oral suckers present; mouth having irregular papillae on lower lip; teeth and beaks absent; caudal myomeres distinct; pigmentation uniform over body and caudal musculature; caudal fin transparent with scattered small flecks.

[Ill.u.s.tration: FIG. 16. Relative rate of growth in tadpoles of _Smilisca phaeota_ as correlated with developmental stages.

Formulas for the limb bud refer to its length (L) in relation to basal diameter (D).]

_Stage 25._--Operculum complete; gills absent; sinistral spiracle apparently functional; cloacal tail-piece, nasal capsules, and external nares present; gut partly formed; mouth bordered by single row of papillae, except medially; small papillae present in lateral fold of lips; two upper and three lower tooth-rows present, but not fully developed; beaks apparently fully developed; depth of dorsal and ventral fins less than depth of caudal musculature: tip of tail upturned; pigment on body most dense on dorsum and sides; faint, nearly pigmentless crescent-shaped mark on posterior edge of body; concentrations of pigment forming small spots on tail.

_Stage 28._--Mouthparts complete; limb bud about half as long as thick; other structural features and coloration closely resemble those in stage 25.

_Stage 30._--Limb bud approximately twice as long as thick; body as deep as wide; dorsal fin deepest just posterior to body; ventral fin deeper than caudal musculature; tail sharply upturned distally; a.n.a.l tube dextral; brown pigment spa.r.s.e on flanks.

Table 11.--Growth and Development of Tadpoles of Smilisca phaeota.

(Means Are Given in Parentheses After the Observed Ranges.)

==================================================================== Stage | N | Total length | Body length | Tail length -------------------------------------------------------------------- 15 | 10| -- | 1.9-2.1 (1.97) | -- 16 | 8| -- | 2.0-2.2 (2.07) | -- 18 | 4| -- | 2.2-2.6 (2.31) | -- 21 | 3| 7.9-8.6 (8.21) | 4.1-4.5 (4.31) | 3.8-4.1 (3.92) 25 | 10| 8.7-10.6 (9.69) | 4.5-4.8 (4.64) | 4.3-6.0 (5.05) 26 | 11| 12.3-16.1 (14.01) | 4.2-6.3 (5.60) | 6.7-9.8 (8.41) 27 | 10| 13.0-15.7 (14.28) | 4.9-6.2 (5.40) | 7.7-10.5 (8.88) 28 | 13| 13.9-20.9 (15.62) | 5.2-8.3 (5.75) | 8.5-12.6 (9.85) 29 | 8| 17.8-22.3 (19.79) | 6.3-8.4 (7.19) | 11.5-14.0 (12.60) 30 | 9| 20.3-24.8 (22.85) | 8.1-10.5 (9.32) | 10.5-15.5 (13.53) 31 | 5| 24.1-28.5 (26.61) | 9.4-11.2 (10.59) | 14.7-17.3 (16.02) 34 | 5| 24.8-29.4 (27.31) | 9.2-11.6 (10.73) | 15.6-18.5 (16.80) 36 | 3| 30.0-30.1 (30.07) |10.1-12.2 (11.15) | 18.9-20.0 (19.44) 37 | 4| 28.9-34.1 (31.75) |11.5-12.4 (11.88) | 17.4-22.5 (19.88) 38 | 1| 28.98 |12.88 | 16.10 39 | 2| 35.6-36.9 (36.25) |14.00 | 21.6-22.9 (22.25) 40 | 2| 32.3-39.8 (36.05) |14.00 | 18.3-21.8 (20.05) 43 | 2| 21.5-23.0 (22.25) |14.2-14.8 (14.45) | 6.8-8.8 (7.80) 44 | 4| -- |14.5-15.6 (15.08) | -- 46 | 11| -- |12.7-16.7 (14.26) | -- --------------------------------------------------------------------

Table 12.--Growth and Development of Tadpoles of Smilisca sordida.