Intraspecific developmental variation in the life cycle of the Andean Treefrog (Boana riojana): A temporal analysis

Abstract

Intraspecific variation during the anuran larval period has been analyzed mainly in relation to the timing of metamorphosis and body size at metamorphosis. However, other traits may vary as well. We examined two developmental series of Boana riojana from the same population in two consecutive years and describe intraspecific variation in larvae of this species. We discuss how variation, if present, may influence its life cycle. We found that both larval series differed in the larval period length, one twice as long as the other. This variation primarily depended on when breeding occurred, metamorphosis was achieved during late spring in both generations and at similar sizes, and only the rate of larval development during premetamorphosis varied extensively between years. This is consistent with thyroid gland activity because when it became active the developmental trajectory became more canalized. No variation of staging sequence occurred in relation to the different durations of the larval period. However, in the long‐lasting series we found two different morphs. Also, integument, thyroid gland, skeleton, and testis differentiation events occurred at the same developing stages. In contrast, ovarian differentiation proceeded at the same absolute age in both series. Sexual dimorphism becomes evident within the year after metamorphosis. The intraspecific heterochrony that we describe for the larval development of B. riojana does not lead to phenotypic variation at the end of metamorphosis. We discuss the importance of analyzing growth and development independently. Each proceeds differently in time, but with an interdependence at some point, because size and shape do not vary at the end of metamorphosis.

Histology and microscopic anatomy of the thyroid gland during the larval development of Pseudis platensis (Anura, Hylidae)

“…In analogy with the GNM Xenopus laevis tadpoles, the thyroid of P. platensis is poorly developed during premetamorphosis, until a time when the tadpoles reaches about 70% of their final larval body size. Thus, there is low or no activity of the thyroid gland for a long time period during which body growth predominates over differentiation.The premetamorphosis and its relation to the degree of activity of the thyroid gland were also observed in populations of Boana riojana tadpoles(Goldberg et al, 2019). Boana riojana larvae with prolonged premetamorphosis have a poorly developed thyroid gland with little or no evidence of activity during this period, consistent with what we observed for P. platensis.…”

“…Subsequently, their growth curves are less pronounced until the beginning of metamorphosis. The latter growth pattern is also observed in Boana riojana (Hylidae); that is, the body grows slower in late larval stages, even when growth rates during premetamorphosis are variable (Goldberg, Quinzio, Cruz, & Fabrezi, ). In other species (e.g., Dermatonotus muelleri ) growth occurs only during premetamorphosis (Fabrezi, Quinzio, Goldberg, & De Sá, ).…”

“…The premetamorphosis and its relation to the degree of activity of the thyroid gland were also observed in populations of Boana riojana tadpoles (Goldberg et al, ). Boana riojana larvae with prolonged premetamorphosis have a poorly developed thyroid gland with little or no evidence of activity during this period, consistent with what we observed for P .…”

The ontogeny of the lateral line system in Telmatobius atacamensis (Anura, Telmatobiidae)

“…Despite the fact that many of the metamorphic transformations in the genus (skin, auditory and underwater vocalizations, feeding mechanism, webbed feet) are linked to an adult aquatic life (Barrionuevo, , ; Brunetti, Muñoz Saravia, Barrionuevo & Reichle, ), metamorphic regression of the lateral line system always occurs (Fabrezi & Quinzio, ; Fritzsch et al, ). As a sensory system related structurally to the integument, the lateral line system is fully developed at premetamorphic stages when the integument represents a typical larval organization (Goldberg, Quinzio, Cruz, & Fabrezi, ). Albeit poorly studied, on would expect its regression during metamorphosis simultaneously with metamorphic changes of the skin, at late prometamorphic stages, and to completely disappear by the end of the metamorphosis together with the complete loss of the tail.…”

“…Despite the fact that many of the metamorphic transformations in the genus (skin, auditory and underwater vocalizations, feeding mechanism, webbed feet) are linked to an adult aquatic life (Barrionuevo, 2016(Barrionuevo, , 2017Brunetti, Muñoz Saravia, Barrionuevo & Reichle, 2017), metamorphic regression of the lateral line system always occurs (Fabrezi & Quinzio, 2008;Fritzsch et al, 1987). As a sensory system related structurally to the integument, the lateral line system is fully developed at premetamorphic stages when the integument represents a typical larval organization (Goldberg, Quinzio, Cruz, & Fabrezi, 2019).…”