HISTOLOGY AND HISTOCHEMISTRY OF ANDROGEN-STIMULATED NUPTIAL PADS IN THE LEOPARD FROG, RANA-PIPIENS, WITH NOTES ON NUPTIAL GLAND EVOLUTION

Nuptial pads are digital specializations of male frogs that cycle with the reproductive season and are considered to function in mating. Gla ndular secretions of the nuptial pads were analyzed histochemically in androgen-stimulated overwintering leopard frogs, Rana pipiens, to pro vide information on gland function and physiological control. In castr ated and sham-operated male frogs treated with testosterone cypionate, the secretory product of the nuptial gland epithelium stained positiv e for carbohydrates and proteins, yet negative for lipids and glycogen . Secretions also stained positive for tyrosine residues and negative for acidic mucosubstances, sulphated mucosubstances, tryptophan, and c ystine. Castration prior to hormone treatment had no effect on gland s taining properties, and glands of cholesterol-treated castrates and in tact controls appeared to be inactive cytochemically. Nuptial glands o f frogs treated with 5-alpha-dihydrotestosterone were histologically s imilar to those of frogs treated with testosterone cypionate. Nuptial glands share structural and functional characteristics with integument ary mucous glands, and may have been modified evolutionarily from that parent gland population.