Granular cutaneous glands in the frog Physalaemus biligonigerus (Anura, Leptodactylidae): comparison between ordinary serous and 'inguinal' glands

Beside the ordinary granular (or serous) glands, the skin of the leptodacty lid frog Physalaemus biligonigerus possesses peculiar clusters of large gra nular units, the 'inguinal' glands, located in the dorsolateral areas of th e pelvic girdle. Both gland types store their specific products within the syncytial cytoplasm of the secretory unit. These secretory materials consis t of spheroidal or ellipsoidal bodies (granules) with a repeating substruct ure. The subcellular features of the immature products of the ordinary sero us and inguinal glands are identical. However, these products undergo diver gent maturative processes, leading to fluidation on the one hand and conden sation on the other, Secretory release into the small gland lumen was obser ved in both cases, involving merocrine mechanisms. On the basis of the anal ysis of cutaneous serous gland polymorphism in anurans, the inguinal units in P. biligonigerus do not appear to be an independent line. Rather, these large units belong to the ordinary serous type and represent a gland popula tion specialized in the storage of remarkable amounts of product used in ch emical defence of the skin. (C) 1999 Harcourt Publishers Ltd.