THE REPRODUCTIVE CYCLE OF BARISIA MONTICOLA: A UNIQUE VARIATION AMONG VIVIPAROUS LIZARDS

Abstract

Among the several reproductive patterns previously known for viviparous tropical lizards, populations of Barisia monticola from the Cordillera de Talamanca in Costa Rica dem- onstrate a unique variation. The males are continuously spermatogenic without any seasonal changes in size or activity of the testes and seminiferous tubules, and gonadal size is correlated with body size. Our evidence indicates that the ovarian cycle is probably biennial, in contrast to any other known viviparous lizard. Further, the gestation period is also greatly prolonged. While females demonstrate some degree of seasonal synchrony in parturition, the birth period may extend over an interval of at least 5 mo. We suggest that the climatic factors characterizing this montane tropical region can be exploited only by reptiles having extended egg retention and probably represents a thermal environment that favors the evolution of viviparity.