NORMAL DEVELOPMENT OF PACHYMEDUSA DACNICOLOR

Abstract

The embryological and larval development of Pachymedusa dacnicolor was investigated. P. dacnicolor belongs to the Phyllomedusinae (Leaf Frog) Subfamily of the Hylidae (Treefrog) Family. No complete developmental table for any member of the Hylidae exists. Therefore, this developmental table was produced for P. dacnicolor including stages from egg to the end of metamorphosis. The rate of development at different temperatures was included in the study. Investigation revealed that the development of P. dacnicolor is similar to that of other anurans, but several differences were noted. Many of these differences relate to the fact that oviposition occurs in foliage out of water. Developmental peculiarities include: (1) lack of an externally obvious grey cresent; (2) dorsal lip is located more dorsally than is usual; (3) appearance of what resembles a blister at earliest gastrulation (probably the thin roof of the blastocoel) along with an equatorial canal that briefly appears at stage 10.1 (beginning of gastrulation); (4) well developed subblastopore papilla, which develops into the anus; (5) fusion of the operculum begins in the midline and moves lateraly in both directions, but leaves a spiracle just lateral to the ventral midline on the left side; (6) the hind limb bud is short and thick; (7) in hind limb formation the second indentation appears before the first; (8) subarticular tubercles appear before the metatarsal tubercle develops. The most externally obvious difference between P. dacnicolor and other Anurans is the advanced state of development at hatching. Hatchlings are completely formed tadpoles, viz., they possess fully formed eyes, mouth, tail with fins, etc. P. dacnicolor has no oral sucker. The gills of P. dacnicolor larvae are unusually long, and are probably indicative of the environmental constraints placed upon this frog: it is hypothesized that P. dacnicolor may exist close to the minimum physiological tolerance for O₂ due to the high temperatures to which the egg masses are subjected. Temperature studies show best development is obtained at 30°C, which correlates well with temperatures reported in the field.