Ultrastructure of poison glands of South American frogs: A comparison betweenPhysalaemus albonotatus andLeptodactylus chaquensis (Anura: Leptodactylidae)

Abstract

Serous (poison) cutaneous glands of the leptodactylid species Physalaemus albonotatus and Leptodactylus chaquensis were compared using light and transmission electron microscopy. Glands in the two species share structural traits common in anurans, including the peripheral contractile sheath (myoepithelium) and the syncytial secretory unit that produces, stores, and modifies the poison. At the ultrastructural level, early steps of poison production are also similar and fit the usual path of proteosynthesis, involving rough endoplasmic reticulum (RER) and Golgi stacks (dictyosomes) in the peripheral syncytial cytoplasm. However, several differences are obvious during the maturational processes that lead post-Golgian products to their ultimate ultrastructural traits. In P. albonotatus, the dense product released from the dictyosomes acquires a thick repeating substructure, which, however, becomes looser in the inner portion of the syncytium. In L. chaquensis, serous maturation involves gradual condensation, and opaque, somewhat "vacuolized" granules are formed. These different maturational paths expressed during poison manufacturing in the two species agree with the polyphyletic origin of the family Leptodactylidae. On the other hand, data collected for P. albonotatus fit previous findings from P. biligonigerus and stress the view that poisons produced by congeneric species share similar (or identical) ultrastructural features.

Lumbar glands in the frog genera Pleurodema and Somuncuria (Anura: Leiuperidae): histological and histochemical perspectives

“…Granule morphology of LSGs varies greatly, as has previously been reported for serous glands of other anuran species, e.g., Physalaemus biligonigerus (Delfino et al. 1999, 2001), P. albonotatus and Leptodactylus chaquensis (Alvarez et al. 2005), and Rhinella icterica (Almeida et al.…”

A ‘toxin mantle’ as defensive barrier in a tropical bird: evolutionary exploitation of the basic permeability barrier forming organelles

“…Such high degree of osmiophilic reaction has been used in electron microscopy of plant cells to localize alkaloids that are associated with lipid inclusions. Such osmiophilia has been noted in the poison glands of skin of dart‐poison frogs as well, where alkaloid toxins have been definitively documented. The putative association of toxic alkaloids with the MGBs indicates the active sequestration of the toxins into secretory organelles (LB homologues) rather than a passive accumulation into all lipid domains of epithelial cells.…”

A phylogenetic analysis of Pleurodema (Anura: Leptodactylidae: Leiuperinae) based on mitochondrial and nuclear gene sequences, with comments on the evolution of anuran foam nests

“…(1999) for P. biligonigerus . Also, secretory products of ordinary serous glands of P. albonotatus and P. biligonigerus share similar ultrastructural traits in maturation paths (Delfino et al., 1999; Alvarez et al., 2005). Ron et al.…”