Characterization of the spermiation response, luteinizing hormone release and sperm quality in the American toad (Bufo americanus) and the endangered Wyoming toad (Bufo baxteri).

Abstract

Spermiation and LH release in response to several methods of LHRH administration were assessed in the American toad (Bufo americanus), and the most successful method was tested in the endangered Wyoming toad (Bufo baxteri). Specific objectives were to: (1) compare spermiation responses and plasma LH concentration after invasive and non-invasive LHRH treatments; (2) evaluate sperm production in response to different LHRH dosages; (3) characterize the timing of sperm release post LHRH treatment; and (4) assess sperm quality (motility, viability, morphology and acrosomal status). Male American toads were administered 4 microg LHRH by one of four routes: (1) intraperitoneal injection (i.p.); (2) subcutaneous injection (s.q.); (3) dorsal dermis absorption (d.d.a.); and (4) ventral dermis absorption (v.d.a.). Aspermic urine only was collected from saline-treated controls and d.d.a. animals. Several v.d.a. animals released spermic urine; however, all LHRH-injected toads released spermatozoa. I.p. animals produced higher sperm and LH concentrations than s.q. animals. The spermiation response in animals treated i.p. with 1 microg LHRH was similar to that in animals treated with 4 microg, but lower LHRH dosages tested produced inferior responses. Sperm production in responsive animals increased over time during the 12-h sampling interval. Regardless of treatment, most American toad spermatozoa were motile, viable, and acrosome-intact. Endangered Wyoming toads were treated i.p. with 4 microg LHRH, and spermic urine was collected. Although most spermatozoa were viable and acrosome-intact, a considerable percentage possessed structurally abnormal heads. A single i.p. injection of LHRH appears to be a reliable and safe method for controlling spermiation in toads and may be useful for assisting endangered amphibian propagation.