| Table 12.—Growth and Development of Tadpoles of Smilisca sordida. (Means Are Given in Parentheses After the Observed Ranges.) | ||||
| Stage | N | Total length | Body length | Tail length |
| 25 | 6 | 25.5-28.0 (26.1) | 9.0-9.5 (9.3) | 16.2-18.5 (16.7) |
| 33 | 2 | 28.5-30.0 (29.3) | 10.2-10.5 (10.4) | 18.0-19.8 (18.9) |
| 36 | 8 | 29.5-34.5 (32.3) | 10.2-11.7 (10.8) | 19.3-23.0 (21.5) |
| 37 | 7 | 31.6-37.5 (34.6) | 11.0-12.5 (11.5) | 21.6-25.0 (23.2) |
| 41 | 3 | 33.0-37.2 (35.2) | 11.6-12.2 (11.9) | 21.4-25.2 (23.2) |
| 43 | 1 | —— | 12.4 | —— |
| 46 | 9 | —— | 13.1-15.7 (14.9) | —— |
Stages 34, 36, 37, and 38.—Stage 34, foot paddle-shaped with four toe buds; stage 36, five toe buds; stages 37 and 38, lengthening of toes. In all four stages, spiracle persistent, and pigmentation resembling that of early stages.
Stage 39.—Metatarsal tubercle present; greatest total length (36.9 mm.) attained.
Stage 40.—Subarticular tubercles prominent; skin over forelimbs transparent; cloacal tail-piece and spiracle absent; outer tooth-rows degenerating; caudal fins shallower than in preceding stages; distal part of tail nearly straight; size of dark markings on tail decreased; pigment present on hind limb.
Stage 43.—Forelimbs erupted; larval mouthparts absent; corner of mouth between nostril and eye; transverse bands present on hind limbs; tail greatly reduced (about 8 mm. in length).
Stage 44.—Sacral hump barely noticeable; tail reduced to a stub; corner of mouth at level of pupil of eye; dorsal surfaces pale olive-green; venter white.
Changes proceed in a definite pattern during the growth and development of tadpoles. Larval teeth are absent in hatchlings; the inner tooth-rows develop first, and the third lower row last. At metamorphosis the third lower row is the first to be lost. The tail increases gradually in length relative to the body. In stage 25 the tail is 52.1 per cent of the total length, and in stage 36, 64.6 per cent. In later stages the tail becomes relatively shorter through resorption. Duellman and Klaas (1964:320) noted a great size-variation in Triprion tadpoles in stage 25. No such variation is apparent in any stage of any of the species of Smilisca studied.
The growth and development of the other species of Smilisca do not differ significantly from that of S. phaeota. The tadpoles of S. sila and sordida from streams have relatively longer tails at hatching. For example, in tadpoles of S. sordida the average length of tail is 64.0 per cent of the body-length in stage 25, and in stage 37, 67.0 per cent.
The tadpoles of S. baudini, cyanosticta, phaeota, and puma are pelagic inhabitants of shallow ponds. Early stages of S. baudini in which external gills are present have been observed to hang vertically with the gills spread out at the surface of the water, a behavior noted by Zweifel (1964:206) in tadpoles of Phrynohyas venulosa, which also develop in warm, standing water having a relatively low oxygen-tension. When disturbed the pelagic tadpoles usually dive and seek shelter amidst vegetation or in mud on the bottom. This behavior was observed in S. baudini, cyanosticta, and phaeota by day and at night. No tadpoles of S. puma were observed by day; those seen at night were near the surface of small water-filled depressions in a grassy marsh; they responded to light by taking refuge in the dense grass. Perhaps tadpoles of this species are negatively phototactic and remain hidden by day.
The stream-inhabiting tadpoles of S. sila and sordida live in clear pools in rocky streams, where they were observed to cling by their mouths to rocks in the stream and to seek shelter amidst pebbles or beneath rocks and leaves on the bottom. These tadpoles are not found in shallow riffles.
We have not found tadpoles of two species of Smilisca in the same body of water and therefore cannot offer observations on ecological relationships in sympatric situations.