Scinax granulatus (NCN) Reproduction

DIAZ SEIJAS M.E.; NATALE G.S.; GANGENOVA E.

HERPETOLOGICAL REVIEW

Año: 2008 vol. 39 p. 342 - 342

0018-084X

SCINAX GRANULATUS (NCN). REPRODUCTION. According to bibliographical sources, the reproductive strategy described for the species of genus Scinax agrees with the strategy of most species of Hylinae, which consists of laying egg masses adhered to submerged vegetation (Cei, J. M. 1980. Amphibians of Argentina. Monitore zool. Ital., N. S., Monogr. 2. 609 pp., Gallardo, J. M. 1987. Anfibios argentinos. Guía para su identificación. Biblioteca Mosaico, Bs. As., Agropecuaria 1. 98 pp., Lavilla, E.O. and José M. Cei. 2001. Amphibians Of Argentina A Second Update, 1987 – 1997. Mus. Reg. Scien. Natur. Torino 28, Italia. 177pp., Lavilla, E. O. and M. Rouges. 1992. Reproducción Y Desarrollo De Anuros Argentinos. Asociación Herpetológica Argentina. 5: 1-61. Duellman, W.E and L. Trueb, 1986. Biology of Amphibians. McGraw - Hill Book Co., New York. 670pp.). This note describes the egg deposition mode of Scinax granulatus in its natural environment. The observations were made in the vicinity of La Plata city, Buenos Aires province, Argentina (36° 01’ 05, 68” S; 57° 51’ 32,79” W), during observed reproductive season of Scinax granulatus, (from October to February) as results of fortnightly samplings made between September 2003 and February 2006 which are part of a more comprehensive study of the reproductive behavior of this species. The description is based on 9 clutches, 4 of which were observed directly in the field and 5 were obtained from amplexing pairs captured in the field and transported to laboratory facilities, where each pair was placed in containers with 10 cm of water until spawning was confirmed. Containers included: glass canisters, 12 cm in diameter and 113 cm²  in surface area (N = 2), plastic tanks, 27.5 cm in diameter and 2376 cm²  in surface area (N = 2) and fiberglass tanks, 6960 cm² in surface area (N = 1). After oviposition we noted the spatial arrangement of eggs, and counted between 300-700 eggs in all cases, with pigmented animal pole, 1.3 mm ± 0,037 diameter embryos and 1.7mm ± 0.050 capsules with jelly coat (data are mean ± 95% confidence limits, N = 35). We conclude from our observations that Scinax granulatus disperses its eggs on the bottom of water bodies (Fig. 1); eggs are adhered to submerged objects and/or the bottom individually or in small clusters of 2-3 eggs each. The clutches are scattered without a defined pattern; while their extension was constrained by container size in laboratory conditions, in the field they were arranged in irregular zones over an average surface area of 3616 cm², which represents a small sector of the water body. This arrangement of eggs was recorded in all observations, both in the field and under experimental conditions. Consequently, the ovoposition mode of Scinax granulatus is significatively different from that of the remaining species of Hylidae. To our knowledge, this is the first report of this egg deposition mode for a species of Hylidae.