New methodology in amphibian bone staining indicates differential lifespans in two tepui summit anurans ( <i>Oreophrynella quelchii</i> , Bufonidae and <i>Pristimantis aureoventris</i> , Craugastoridae)

Age is a key life history trait that informs population dynamics, growth, and reproduction. In anurans, environmental conditions, especially in harsh habitats, strongly influence age-specific demographics. Only two amphibian species occur on the summit of Roraima-tepui, exhibiting contrasting demographics although exposed to similarly severe environmental constraints. The toad Oreophrynella quelchii thrives in unexpectedly high numbers on the summit, while the frog Pristimantis aureoventris is rarely observed and known only from a few specimens. Age structure remains poorly understood in both species. Here, we used a new methodology to identify bone growth marks (GMs) and estimate lifespan in O. quelchii and P. aureoventris, applying acridine orange staining and confocal microscopy as a more sensitive and less subjective alternative to traditional skeletochronology, often unreliable in tropical species. Typical lines of arrested growth (LAGs) were absent in both species. While multiple GMs were observed in all P. aureoventris specimens, only one GM was found in most O. quelchii individuals, suggesting a shorter lifespan.