Integrating morphology and physiology of the key endocrine organ during tadpole development: the interrenal gland

ELEONORA REGUEIRA; AILÍN O'DONOHOE; MARIELA PAVON NOVARÍN; GABRIELA MICHOU ETCHEVERRÍA; CAROLINA TROPEA; GLADYS HERMIDA

JOURNAL OF ANATOMY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2022

0021-8782

Indirect development is widespread in anurans and is considered the ancestral condition. The metamorphosis of larvae into juveniles involves highly coordinated morphological, physiological, biochemical and behavioral changes, promoted by the thyroid hormone and interrenal corticosteroids. Stress response to environmental changes is also mediated by corticosteroids, affecting the timing and rate of metamorphosis and leading to a great developmental plasticity in tadpoles. Given the potential effect of interrenal gland ontogeny alterations on metamorphosis and the lack of studies addressing both the morphology and endocrinology of this gland in tadpoles, we present corticosterone production and histological changes through the ontogeny of interrenal gland in the generalized pond-type tadpole of Rhinella arenarum (Anura, Bufonidae). This species shows the highest concentration of whole-body corticosterone by early climax, when drastic metamorphic changes begin. This is coincident with the morphological differentiation of steroidogenic cells and formation of interrenal cords. By this stage, steroidogenic cells have a shrunken cytoplasm, with a significantly higher nucleus-to-cell diameter ratio. The lowest corticosterone concentration during pre-metamorphosis and late climax is associated with small undifferentiated cells with lipid inclusions surrounding large blood vessels between kidneys, and with cords of differentiated steroidogenic cells with a significantly lower nucleus-to-cell diameter ratio, respectively. Our study characterizes the morphological and physiological pattern of interrenal gland development, showing an association between certain histological and morphometric characteristics and corticosterone levels. Variations in this morpho-physiological pattern should be considered when studying the phenotypic plasticity or variable growth rates of tadpoles.