Larval Morphology and Development of Tree Frog

The life history of the tree frog Polypedates teraiensis was studied by raising eggs under laboratory condition. The breeding of Polypedates teraiensis is normally seen during monsoon between the month of April to August. However, during the present study eggs in foam nests were collected from April upto September in 2012. Observations on larval development, stage and size at hatching and larval duration was studied and is being presented here. The larvae are oval and depressed. The hatchlings measured about 7.8 mm at stage 22 (Gosner, 1960). The keratodont jaws developed at stage 25 and disappeared by stage 42. The juveniles measured about 16.2 mm. The life history (post hatching) was completed within 42 days.


INTRODUCTION
Anurans having a biphasic life cycle, breed in a variety of water bodies ranging from lentic to lotic water bodies.Anuran tadpoles exhibit structural diversities that are associated with their habitat, foraging behaviour and predator avoidance.The tree frog Polypedates teraiensis is a common rhacophorid breeding between April to August in north east India and is known to deposit eggs in the foam nest.There are at least six species of Polypedates currently recognized in north-eastern India (Chakravarty et al. 2011).However, little is known about the larval biology of these species from this region.The present study describes the oral disc, various morphometric features of the tadpoles, size and stage at hatching and duration of life history (post hatching) from Cachar district, Assam, north-east India.

MATERIALS AND METHODS
Between April to September, 2011 and 2012 several foam nests of Polypedates teraiensis were sighted in manmade tanks in Assam University campus constructed for water storage for construction work.The foam nests were found adhering to the wall of the tanks slightly above the water surface.Some of the foam nests were brought to the laboratory and kept in aquaria with pond water for hatching.Tadpole rearing was done in the laboratory at the temperature 26-33 C. The clutch sizes were recorded.Data are based on three clutches.Various developmental stages were fixed in 10% formaldehyde at periodic interval and duly measured.Tadpoles were staged according to Gosner (1960).Sampling was repeated for two successive years and the average data for three different cycles are presented herein.Tadpoles were fed on fish food and algae collected from the pond.Morphometric measurements of various developmental stages were taken using vernier calliper.These include BL, TL, BD, BW, T, TH, BTMH, IO, IN, SO and SN.Abbreviations and definitions are in accordance with Altig and McDiarmid (1999).Description of oral apparatus and labial tooth row formula (LTRF) is in accordance with Altig (1970).

RESULT
The frog is a seasonal breeder, breeding only during the monsoon.Depending on the rainfall the breeding season extended from April to September.During the study, the tanks were filled with rain water and the bottom was found to be covered with debris material, decaying leaves and mud.There was no other tadpoles found in the tanks, but the tanks were inhabited by other adult anurans such as Fejervarya sp. and Euphlyctis cyanophlyctis.Insect fauna was also abundant in the tank.The foam nests were found 4-5 inch above the water body adhering to the wall, some floating on the surface of water .The nest were collected from the tank and brought to the laboratory for rearing.It took 1-2 days for hatching after the collection.The number of hatching per nest ranged between 100 to150.The hatchlings measured about 7.8 mm in total length and were at stage 22 (Gosner stage).The life history (post hatching) was completed within 42 days.Hours and days taken for development, lowest, highest and average length of different developmental stages are presented in Table 1.

Tadpole morphology
Body is oval, snout slightly rounded and depressed, eyes lateral in position.Nostrils dorsal, nearer to snout than eyes.Spiracle single sinistral, position lateral, vent dextral.Dorsal fin height is greater than the ventral fin.Both fin gradually tapering towards the pointed tip.Black spot is present all over the body and tail.Ventral side of the body is not pigmented and transparent at the abdomen region.Hence the intestinal spiracle is clearly visible through the transparent abdominal wall.Morphometric measurement of various developmental stages is presented in Table 2.

Oral disc
Mouth anteroventral, marginal papillae are biserially arranged.Teeth blunt and are not same in height.Lower jaw 'v' shaped and jaw sheath finely serrated.Upper jaw arch shaped with a weak median convexity, both jaw sheaths edged with black.Submarginal papillae present.Disc emarginate, labial papillae and beak disappearing by stage 42 LTRF 4(2-4)/3(1).First row of the upper labium continuous whereas the 2 nd , 3 rd , and 4 th rows are interrupted.Innermost row of lower labium slightly interrupted whereas the two other rows are continuous (Fig: 4).

Coloration
The tadpoles are light brown in colour with brown pigments all over the body and tail portion.Fin transparent.