PLEURODEMA CINEREUM (Puna´s Four- eyed Frog) COMMUNAL OVIPOSITION

AGOSTINI GABRIELA; CAJADE RODRIGO; ROESLER IGNACIO

HERPETOLOGICAL REVIEW

Año: 2007 vol. 38 p. 441 - 441

0018-084X

PLEURODEMA CINEREUM (Puna’s Four-eyed Frog). COMMUNAL OVIPOSITION. Communal oviposition has been recorded in several species of Leptodactylid frogs of genera Pleurodema and Physalaemus (Zina 2006. Amphibia-Reptilia 27: 148–150). Here we describe communal oviposition from a population of Pleurodema cinereum in the urban area of Copacabana (16º09´58´´S 69º05´09´´W), 700 m. from the coast of Titicaca Lake, La Paz Dept., Bolivia. The Titicaca Lake, 3850 m a.s.l., is located in the Puna of the Bolivian Altiplano. The wet season extends from December through March, with an average 1000 mm. rainfall, but with 50% of annual variations. The rains are mild and constant almost every day, and thus they normally create temporary ponds. The reproductive activity that we found was observed during 31th December 2005 in two temporal ponds located in an untilled field in Copacabana town, and separated by a man-made stone wall. The ponds had a surface area of c. 105 m2 and c. 35 m2, with a mean depth of 15 cm and covered by some aquatic vegetation, principally Juncaceae. Explosive choruses of P. cinereum were found after several days of mild afternoon rainfalls. The field notes about reproductive activity begin with our arrival to the ponds at 1500 h. (Water Tº= 10ºC; Air Tº= 7.5ºC). Soon two different communal oviposition were located, with 9 amplecting pairs in the largest and 6 in the other. They were arranged in an elliptical pattern (Fig. 1).The release of eggs and the jelly beating were directed toward the center of the ellipse, and that produced a large foam mass. The foam of the 9 amplecting pairs measured 28 cm x 12 cm, and the other 20 cm x 11 cm. Like Fernandez & Fernandez (1921. An. Soc. Cient. Arg. 91: 97–140) we found that only the males were in charge of the jelly beating and the consequent building of the foam nest. Although the two communal ovipositions were still being built, we were able to find another 11 communal nests already finished and another 4 nests that, because of their small size (7 cm diameter), were probably built by a single amplexus. All nests, both communal and individual ones, were within the more vegetated areas of the ponds, and that vegetation provides better attachment and protection. During the period that we spent surveying the ponds, we found about 40 calling males, 16 of which were close to the communal oviposition sites. We also found 10 unmated females and 9 amplecting pairs close to each other, but that had not begun construction of their foam nest. The calling males and all the amplecting pairs were in the shallowest parts of the ponds, mostly 5 to 7 cm deep. As suggested by Höld (1990. Copeia 1990: 547–554), communal oviposition could result from the scarcity of adequate sites for the construction of the foam nest, or else represent a strategy against desiccation. In this particular case both hypotheses appear feasible, if we consider the unfavorable Puna’s weather, the general conditions of the ponds and the explosive reproductive behavior of P. cinereum. We thank Daiana Ferraro, Diego Baldo, Cecilia Morgan, Juan Mazar Barnett and Juliana Zina for their manifold contributions. Submitted by M. Gabriela Agostini (gagostini@quimica.unlp.edu.ar), Rodrigo Cajade and Ignacio Roesler. CIMA Dpto. de Química, Facultad de Ciencias Exactas, UNLP. 47 y 115, La Plata (1900), Bs. As., Argentina.