Tadpole development in 
Colostethus stepheni

Dr. Clive Cummins
Last update: 17 August, 2002

Most of the known species of Colostethus carry their tadpoles from a terrestrial nest and deposit them in pools or streams.  A variant of this behaviour is that of C. stepheni, whose tadpoles remain in the nest until they reach metamorphosis.  I have not seen C. stepheni; however, I found references to five publications and a thesis on this species.  The breeding behaviour of C. stepheni is the subject of an M.Sc. thesis by Flora Junc, then of the Dept. of Zoology at the University of Sao Paulo, Brazil.  The following description is condensed from Junc, Altig and Gascon (1994).  Junc found that C. stepheni grew to about 18 mm at the study site near Manaus; its breeding season began at the start of the rainy season and it could be found far from wet areas.  Eggs were deposited in cup-shaped leaves with another leaf acting as a roof. 

After the eggs were laid the female stayed at the nest for up to 50 minutes, but did not return again.  The male stayed close to the nest for 2-3 days but later spent only a couple of hours a day at the nest.  The average number of eggs per clutch was 3.8, but more than one clutch could be found in C. stepheni nests.  The average egg diameter was 2 mm. The clutch characteristics of C. stepheni were markedly different from those of C. marchesianus, a similarly sized species that lived in the same area. C. marchesianus, which carries its tadpoles to water, laid clutches averaging 9.2 eggs of 1 mm diameter. 

The tadpole of C. stepheni was described as having mouthparts lacking in keratinized and typical soft structures.  The gut was poorly differentiated and packed with yolk platelets.

The behaviours of both C. stepheni and C. degranvillei allow the frogs a degree of freedom from standing or flowing water which could be advantageous if water bodies are very short lived, or if the tadpoles would be at high risk from aquatic predators.  By carrying its offspring around, C. degranvillei may be better able than C. stepheni to protect them from terrestrial predators and to choose a suitable place for the beginning of their lives as juvenile frogs.  On the other hand, C. stepheni has greater scope for raising larger numbers of offspring - freedom from the burden of carrying tadpoles allows a series of clutches to be raised in a single nest. Junc's observations strongly suggest that the tadpoles of C. stepheni must reach metamorphosis using only the resources provided in the egg.  Consequently, the newly metamorphosed frogs must be very small. Lima and Moreira (1993) reported that small C. stepheni mainly eat mites and springtails.

References:
Junc, F.A. 1998. Reproductive biology of Colostethus stepheni and Colostethus marchesianus (Dendrobatidae), with the description of a new anuran mating behaviour. Herpetologica 54:377-387.

Junc, F.A. 1996. Parental care and egg mortality in Colostethus stepheni. J. Herpetol.30: 292-294.

Junc, F.A., Altig, R. & Gascon, C. 1994. Colostethus stepheni, a Dendrobatid frog with a non-transported nidicolous tadpole. Copeia 1994:747-750.

Lima, A.P. & Moreira, C. 1993. of Colostethus stepheni (Anura, Dendrobatidae). Oecologia 535: 93-102.

Moreira, G. & Lima, A.P. 1991. Seasonal patterns of juvenile recruitment and reproduction in 4 species of leaf litter frogs in Central Amazonia. Herpetologica 47: 295-300.

Junc, F.A. 1994. Biologia e ecologia reprodutiva de duas especies simpatricas de Colostethus na regio de Manaus, Amazonia central. MSc thesis, University of Sao Paulo, Brazil.