Causes of embryonic mortality in Espadarana prosoblepon (Anura: Centrolenidae) from Costa Rica

Causes of embryonic mortality in Espadarana prosoblepon (Anura: Centrolenidae) from Costa Rica. Members of the family Centrolenidae—commonly known as “glass frogs”—exhibit arboreal egg-laying behavior, depositing their clutches on riparian vegetation. Few studies have investigated specific causes of mortality during embryonic stages, perhaps the most vulnerable stage during the anuran life cycle. The Emerald Glass Frog, Espadarana prosoblepon, was used as a case study to investigate the causes of embryonic mortality in a species with short-term (i.e., less than 1 day) parental care. The specific sources of mortality of eggs of E. prosoblepon were quantified and overall rates of survival (hatching success) were estimated. Nineteen egg clutches were transferred from permanent outside enclosures to the wild. Clutch development was monitored daily until hatching; five mortality causes were quantified: desiccation, failure to develop, fungal infection, predation, and “rain-stripped.” The main causes of mortality were predation (often by katydids and wasps) and embryos stripped from the leaf during heavy rains. The results were compared to those of previous studies of centrolenids exhibiting parental care, and discussed in the context of the importance of the natural history data for these frogs with regard to understanding the evolutionary history of parental care in glass frogs.Causas de mortalidade embrionária em Espadarana prosoblepon (Anura: Centrolenidae) da Costa Rica. Membros da família Centrolenidae—comumente conhecidos como “pererecas-de-vidro”—exibem o comportamento arborícola de postura de ovos, depositando suas desovas na vegetação ripária. Poucos estudos investigaram causas específicas de mortalidade durante estágios embrionários, talvez o estágio mais vulnerável durante o ciclo de vida dos anuros. A perereca-de-vidro-esmeralda, Espadarana prosoblepon, foi usada em um estudo de caso para investigar as causas da mortalidade embrionária em uma espécie com curto período de cuidado parental (menos de 1 dia). As causas específicas de mortalidade de ovos de E. prosoblepon foram quantificadas e as taxas gerais de sobrevivência (sucesso de incubação) foram estimadas. Dezenove desovas foram transferidas de recintos externos permanentes para a natureza. O desenvolvimento da desova foi monitorado diariamente até a eclosão; foram quantificadas cinco causas de mortalidade: dessecamento, falha no desenvolvimento, infecção fúngica, predação e retirada pela chuva. As principais causas de mortalidade foram a predação (geralmente por gafanhotos e vespas) e embriões arrancados da folha durante fortes chuvas. Os resultados foram comparados com os de estudos anteriores de centrolenídeos que exibem cuidados parentais e discutidos no contexto da importância dos dados da história natural para essas pererecas no que diz respeito à compreensão da história evolutiva do cuidado parental em pererecas-de-vidro

Parental Care and Acoustic Communication of the Smooth Guardian Frog Limnonectes palavanensis, a Bornean Frog With Possible Sex-Role Reversal

Sexual selection theory predicts that the sex contributing most toward the viability of the offspring will become the choosy sex. In most animal species, females have higher parental investment; thus, sexual selection typically acts more strongly on males, making the females choosy. On rare occasions, male parental investment is so high that it limits the potential for additional mating opportunities. In these cases, females compete for males and males become the choosy sex, leading to a sex-role reversed system. The sex-role reversal hypothesis states that males invest more in the offspring that females do, females display sexually selected traits more intensely than males, and females outnumber males in the mating pool, leading to more intense intrasexual competition among females. I characterized the vocal repertoire and parental care behaviors in the smooth guardian frog Limnonectes palavanensis in Brunei Darussalam (Borneo Island) in order to test predictions of the sex-role reversal hypothesis. I found that males perform all parental duties, attending the eggs for 9–11 days, and then transporting the tadpoles on their backs to a suitable deposition site. These deposition sites are scarce, which may increase the number of days it takes a male to return to the mating pool. Choice experiments testing deposition site preferences demonstrated that males do not avoid predators or conspecific tadpoles. In addition, males may split their tadpoles among nearby pools. Moreover, I described the vocal repertoire of male and female L. palavanensis. Males exhibit an advertisement call and a courtship call not previously described for this species. Remarkably, I found that females gather around a calling male and start calling spontaneously at higher rates than those of the males, a behavior not previously reported in anurans. Using playback stimuli, I found that males do not defend territories and lack an aggressive call, however, they exhibit male-male acoustic interference. Females increase their calling rate when a simulated male is present but there was no evidence that they respond differently to female calls. The prolonged male parental care behavior and the calling behavior of L. palavanensis constitute evidence for sex-role reversal in this species

Influence of environmental factors and body condition on the post-oviposition behavior in the emerald glass frog Espadarana prosoblepon (Centrolenidae)

In species with parental care behaviors, parents may adjust the intensity and duration of their care if fluctuation in factors such as environmental variables or body condition affects offspring survival. In the face of environmental changes, many egg-laying species remain with their clutch for extended periods if this behavioral adjustment provides tangible benefits to the offspring. However, the length of time parents stay with the offspring may also differ depending on the individual’s body condition. In the glass frog family (Centrolenidae), several species exhibit long-term egg attendance in which they remain with their clutch for several days after oviposition takes place. For some of them, changes in environmental variables lead to increased parental care efforts. For the species in which parents remain with their offspring for a short period (less than 24 hours), it is less clear if this constitutes parenting behavior, and whether parents adjust their efforts as a function of environmental change or the parent’s body condition remains unexplored. We studied a population of the Emerald Glass Frog, Espadarana prosoblepon, a species that exhibits a short period of quiescence after oviposition (less than three hours). Our study aimed to determine whether females alter the length of their post-oviposition quiescence period in response to changes in environmental variables (i.e., temperature, humidity, rainfall, and mean wind speed) or female body condition. Pairs in amplexus were captured in the field and transported to semi-natural enclosures to record the duration of post-oviposition quiescence using infrared cameras. Females’ post-oviposition quiescence lasted an average of 67.4 ± 26.6 min (range = 22.7–158.3 min). We did not find a significant relationship between the duration of the post-oviposition quiescence and any of the environmental variables tested. Similarly, post-oviposition quiescence duration was not influenced by female body condition. Because the variation observed in the duration of post-oviposition quiescence was not related to changes in extrinsic (environmental) or intrinsic (body condition) factors, we found no evidence that females of E. prosoblepon modify their post-oviposition behavior in response to any of the variables examined in this study. Future research investigating the adaptive significance of the post-oviposition quiescence observed in this species is needed to understand how this behavior is related to parental care efforts