Title

Reproductive Accomodations for Gestation in the Atlantic Guitarfish, Rhinobatos lentiginosus, Rhinobatidae

Document Type

Article

Publication Date

Winter 1998

Keywords

Guitarfish, Oviduct, Oviducal gland, Uterus, Elasmobranch, Rhinobatos lentiginosus, Rhinobatidae

Publication Title

Journal of the Elisha Mitchell Scientific Society

ISSN

0013-6220

Volume

114

Issue/No.

4

First Page

199

Last Page

208

Abstract

The Atlantic guitarfish, Rhinobatos lentiginosus, is characterized by aplacental yolk sac viviparity. Modifications of the female reproductive tract support this form of development in which embryos depend exclusively on yolk sac contents for nutrition throughout gestation. The uterus is characterized by rich vascularization. Uterine epithelium is cuboidal except atop the luminal vessels where it changes to simple squamous. This arrangement reduces the diffusion distance for gas exchange. Two layers of smooth muscle, an interior circular and an outer longitudinal layer make up the wall of the uterus. Jelly coats and the egg envelope that surround the fertilized egg are produced by the oviducal gland (OG). Later in gestation , embryos eclose (hatch) from the egg envelope to complete development free in the uterus. The uterus does not contribute any supplemental nutrients to augment the yolk stores. Longitudinal folds covered in simple columnar ciliated epithelium, except at the base of the folds where secretory columnar cells populate the crypt, characterize the oviduct. Club, papillary, baffle and terminal zones comprise the OG. Club and papillary zones produce various components of the egg jelly. The club zone provides the jelly immediately surrounding the egg and the papillary zone adds additional jelly components. Secretory cells of the club and papillary zones contain strongly PAS+ granules. The baffle zone comprises the majority of the gland and produces the egg envelope. Simple tubular baffle zone glands empty their secretions to secretory ducts that are confluent with the spinneret. Two adjacent semicircular baffle plates covered with cilia comprise the spinneret. As secretory product passes through the spinneret, the baffle plates deflect the flow to create the various layers of the egg envelope, each with slightly different orientations to create a plyboard type of laminate. Baffle zone secretory granules are PAS-. The terminal zone lacks deep tubules and has secretory crypts. Sperm are not observed in the OG.