Non-invasive treatments of luteinizing hormone-releasing hormone for inducing spermiation in American (Bufo americanus) and Gulf Coast (Bufo valliceps) toads

As many as 20% of all assessed amphibian species are threatened with extinc tion, and captive breeding programs are becoming important components of co nservation strategies for this taxon. For some species, exogenous hormone a dministration has been integrated into breeding protocols to improve propag ation. However, most treatments are administered by an intraperitoneal inje ction that can be associated with some risks. The general goal of this stud y was to identify a non-invasive method of applying luteinizing hormone-rel easing hormone (LHRH), which reliably induces sperm release in toads. Speci fic objectives were to 1) test the spermiation response after topical appli cation of different LHRH doses to the abdominal seat region, 2) evaluate th e effects of adding the absorption enhancers dimethyl sulfoxide (DMSO), ace tone, and glyceryl monocaprylate (CMC) to the LHRH, 3) assess the spermiati on response after oral delivery of LHRH in a mealworm vehicle, and 4) compa re sperm characteristics and spermiation responses to treatments in two dif ferent toad species. Male American (n = 9) and Gulf Coast (n = 7) toads wer e rotated systematically through a series of treatments. Urine was collecte d and evaluated for the presence of sperm at 0, 3, 7, 12, and 24 hours post -treatment. There were no statistical differences in spermiation induction or sperm characteristics between American and Gulf Coast toads after the tr eatments. Oral administration of 100 mug LHRH was occasionally successful i n inducing spermiation, but results appeared largely unreliable. Ventral de rmal application of 100 or 10 mug LHRH in 40% DMSO were more effective (P < 0.05) at inducing spermiation compared with the other treatments tested, e liciting sperm release in more than 70% of toads tested. In breeding progra ms for rare and/or fragile anurans, these non-invasive methods of exogenous hormone administration might be preferred over intraperitoneal injections. (C) 2001 Wiley-Liss, Inc.