Divergent male androgen patterns in two sympatric species of Leptodactylus from subtropical South America

Leptodactylus ocellatus L. is sympatric with L. chaquensis Cei on the banks of the Parana river, yet does not show evident gametogenic discontinuity or cyclical variation of secondary sex characters compared with the striking and well-defined seasonal rhythm found in L. chaquensis. The endocrine mechanisms regulating the seasonal reproductive cycle in the male of both species in their sympatric area have been studied through assessment of plasma androgens, related to the morphological examination of testis. A sudden intense spermatogenic activity was recorded in the testes of L. chaquensis in spring months (September-October), but this ceased in late November, and was followed by a strikingly long summer rest. Conversely, few morphological changes in L. ocellatus were found, since the mating period is more irregular and extensive. The androgen plasma changes paralleled the morphological observations. The plasma androgens behaved differently in the two species, since in L. chaquensis the androgen peak values occurred at the end of the intense spermatogenic activity, accompanied by dramatic increase of testicular weight and spermiation, while in L. ocellatus, the highest androgen plasma levels, occurring in August, seemed to indicate a precocious reproductive activity in this species. These data are discussed, in view of the pivotal role played by androgens in regulating the discontinuous reproductive cycle of L. chaquensis.Material digitalizado en SEDICI gracias a la colaboración del Dr. Jorge Williams (FCNM-UNLP).Facultad de Ciencias Naturales y Muse

Divergent male androgen patterns in two sympatric species of Leptodactylus from subtropical South America

Leptodactylus ocellatus L. is sympatric with L. chaquensis Cei on the banks of the Parana river, yet does not show evident gametogenic discontinuity or cyclical variation of secondary sex characters compared with the striking and well-defined seasonal rhythm found in L. chaquensis. The endocrine mechanisms regulating the seasonal reproductive cycle in the male of both species in their sympatric area have been studied through assessment of plasma androgens, related to the morphological examination of testis. A sudden intense spermatogenic activity was recorded in the testes of L. chaquensis in spring months (September-October), but this ceased in late November, and was followed by a strikingly long summer rest. Conversely, few morphological changes in L. ocellatus were found, since the mating period is more irregular and extensive. The androgen plasma changes paralleled the morphological observations. The plasma androgens behaved differently in the two species, since in L. chaquensis the androgen peak values occurred at the end of the intense spermatogenic activity, accompanied by dramatic increase of testicular weight and spermiation, while in L. ocellatus, the highest androgen plasma levels, occurring in August, seemed to indicate a precocious reproductive activity in this species. These data are discussed, in view of the pivotal role played by androgens in regulating the discontinuous reproductive cycle of L. chaquensis.Material digitalizado en SEDICI gracias a la colaboración del Dr. Jorge Williams (FCNM-UNLP).Facultad de Ciencias Naturales y Muse

Divergent male androgen patterns in two sympatric species of Leptodactylus from subtropical South America

Leptodactylus ocellatus L. is sympatric with L. chaquensis Cei on the banks of the Parana river, yet does not show evident gametogenic discontinuity or cyclical variation of secondary sex characters compared with the striking and well-defined seasonal rhythm found in L. chaquensis. The endocrine mechanisms regulating the seasonal reproductive cycle in the male of both species in their sympatric area have been studied through assessment of plasma androgens, related to the morphological examination of testis. A sudden intense spermatogenic activity was recorded in the testes of L. chaquensis in spring months (September-October), but this ceased in late November, and was followed by a strikingly long summer rest. Conversely, few morphological changes in L. ocellatus were found, since the mating period is more irregular and extensive. The androgen plasma changes paralleled the morphological observations. The plasma androgens behaved differently in the two species, since in L. chaquensis the androgen peak values occurred at the end of the intense spermatogenic activity, accompanied by dramatic increase of testicular weight and spermiation, while in L. ocellatus, the highest androgen plasma levels, occurring in August, seemed to indicate a precocious reproductive activity in this species. These data are discussed, in view of the pivotal role played by androgens in regulating the discontinuous reproductive cycle of L. chaquensis.Material digitalizado en SEDICI gracias a la colaboración del Dr. Jorge Williams (FCNM-UNLP).Facultad de Ciencias Naturales y Muse

Changes in Plasma Sex Steroids in Females of Two Sympatric Leptodactylus from Subtropical South America

Leptodactylus ocellatus is a well-known neotropical anuran in Argentina and Brazil, typically inhabiting marshes and streams, from sea level to 1000-1200 m in the Pampean mountains. Leptodactylus ocellatus is sympatric with L. chaquensis in Paraguay and on the Parana borders. Previous work (Cei, 1948,1949,1950,1980; Cei et al., 1955) with these two sibling species, L. ocellatus and L. chaquensis, revealed diversity in their reproductive cycles. Leptodactylus ocellatus exhibits less gametogenetic discontinuity and variety of secondary sex characters; the annual ovarian cycle of L. chaquensis, involves a fallwinter period of atresia for the residual mature oocytes from the former cycle, and at the same time a progressive auxocytic activity. The spring-summer period of mating and egg-laying of L. chaquensis is followed by resorption of retained oocytes. Moreover, in both sexes, a striking seasonal rhythm in the development of secondary sex characters has been found, together with dramatic growth of skeletal humeri and significant variation in serum calcium values (Cohen 1962a, b, 1963).Material digitalizado en SEDICI gracias a la colaboración del Dr. Jorge Williams (FCNM-UNLP).Facultad de Ciencias Naturales y Muse

Changes in Plasma Sex Steroids in Females of Two Sympatric Leptodactylus from Subtropical South America

Leptodactylus ocellatus is a well-known neotropical anuran in Argentina and Brazil, typically inhabiting marshes and streams, from sea level to 1000-1200 m in the Pampean mountains. Leptodactylus ocellatus is sympatric with L. chaquensis in Paraguay and on the Parana borders. Previous work (Cei, 1948,1949,1950,1980; Cei et al., 1955) with these two sibling species, L. ocellatus and L. chaquensis, revealed diversity in their reproductive cycles. Leptodactylus ocellatus exhibits less gametogenetic discontinuity and variety of secondary sex characters; the annual ovarian cycle of L. chaquensis, involves a fallwinter period of atresia for the residual mature oocytes from the former cycle, and at the same time a progressive auxocytic activity. The spring-summer period of mating and egg-laying of L. chaquensis is followed by resorption of retained oocytes. Moreover, in both sexes, a striking seasonal rhythm in the development of secondary sex characters has been found, together with dramatic growth of skeletal humeri and significant variation in serum calcium values (Cohen 1962a, b, 1963).Material digitalizado en SEDICI gracias a la colaboración del Dr. Jorge Williams (FCNM-UNLP).Facultad de Ciencias Naturales y Muse

Changes in Plasma Sex Steroids in Females of Two Sympatric Leptodactylus from Subtropical South America

Leptodactylus ocellatus is a well-known neotropical anuran in Argentina and Brazil, typically inhabiting marshes and streams, from sea level to 1000-1200 m in the Pampean mountains. Leptodactylus ocellatus is sympatric with L. chaquensis in Paraguay and on the Parana borders. Previous work (Cei, 1948,1949,1950,1980; Cei et al., 1955) with these two sibling species, L. ocellatus and L. chaquensis, revealed diversity in their reproductive cycles. Leptodactylus ocellatus exhibits less gametogenetic discontinuity and variety of secondary sex characters; the annual ovarian cycle of L. chaquensis, involves a fallwinter period of atresia for the residual mature oocytes from the former cycle, and at the same time a progressive auxocytic activity. The spring-summer period of mating and egg-laying of L. chaquensis is followed by resorption of retained oocytes. Moreover, in both sexes, a striking seasonal rhythm in the development of secondary sex characters has been found, together with dramatic growth of skeletal humeri and significant variation in serum calcium values (Cohen 1962a, b, 1963).Material digitalizado en SEDICI gracias a la colaboración del Dr. Jorge Williams (FCNM-UNLP).Facultad de Ciencias Naturales y Muse