Ultrastructure and Histochemistry of the Adhesive Breeding Glands in Male Gastrophryne carolinensis (Amphibia: Anura: Microhylidae)
The histology, histochemistry, and ultrastructure of the adhesive breeding glands of male Gastrophryne carolinensis are described. Adhesive glands are mutlicellular exocrine glands in the dermis of the sternum and forearm that cause the male to adhere to the female during amplexus. The epithelial cells have distinct plasma membranes, and the product consists of electron-dense secretory granules that fill the cytoplasm and are released intact by an apocrine process. We support one previous study and contradict another report by finding that adhesive glands react positively for neutral carbohydrates and negatively for glycosaminoglycans and proteins. The ultrastructural results, the first on these organs, confirm that adhesive glands are derived from mucous glands and not serous glands.Abstract
(A) Gastrophryne carolinensis exhibiting axillary type amplexus. (B) Cartoon of the venter of G. carolinensis (dark gray is an area including almost entirely adhesive glands and mucous glands; light gray area is mixed with adhesive glands, mucous glands, and serous glands; unshaded areas contain mainly serous and mucous glands). (C) Light micrograph of light gray area in (B) showing serous and adhesive glands; scale bar = 50 µm. (D) Electron micrograph of (C) demonstrating ultrastructure of the adhesive breeding glands; scale bar = 5 µm. (E) Higher magnification of (D) exhibiting cytoplasmic components of the epithelial cells; scale bar = 0.5 µm. (F) Higher magnification of (D) showing the apocrine type secretion utilized by the adhesive breeding glands; scale bar = 5 µm; Insert, accumulation of secretory material on the epidermis; scale bar = 1 µm. Ag, adhesive gland; As, granule released through an apocrine mechanism; Cy, cytoplasm; Ds, desmosome; Dt, duct; Ep, epidermis; Ic, intercellular canaliculi; Lu, lumen; Mec, myoepithelial cell; Mg, mucous gland; Mi, mitochondria; Mv, microvilli; Nu, nucleus; Rer, rough endoplasmic reticulum; Sg, serous gland; Sm, secretory material; Sv, secretory granules.
(A) Overview of the ultrastructure of a serous gland in the sternal region of Gastrophryne carolinensis; scale bar = 10 µm. (B) Overview of the ultrastructure of a typical mucous gland in the skin of G. carolinensis; scale bar = 5 µm. (C) Higher magnification of (B) showing the cytoplasmic contents in the epithelium of a mucous gland and lateral surface relationships between mucocytes; scale bar = 1 µm. (D) Higher magnification of (B) focusing in on abundant rough endoplasmic reticulum in mucous glands; scale bar = 0.5 µm. Ds, desmosome; Ic, intercellular canaliculi; Lu, lumen; Mec, myoepithelial cell; Mi, mitochondria; Nu, nucleus; Rer, rough endoplasmic reticulum; Sv, secretory granules.
Contributor Notes
Associate Editor: J. M. Quattro.