Effects of aeration and antibiotics on short-term storage of Fowler's toad (Bufo fowleri) sperm

The importance of developing assisted reproductive technologies (ART) for captive assurance colonies of threatened amphibians is increasing as ex situ management of amphibians has been challenged with low reproductive outputs for some species. One hurdle to developing ART in amphibians is the short-term storage of gametes for in vitro fertilization. This study tested the application of two common aquaculture techniques, aeration or the addition of antibacterial solutions, to spermic urine to determine if this would improve the longevity and quality of non-invasively collected sperm samples using hormone therapy. Spermic urine samples were collected non-invasively from Fowler's toads (Bufo fowleri) and either left alone, aerated for 30 min a day, or treated with penicillin–streptomycin. All samples were kept refrigerated at 4 °C. Sperm motility declined within each treatment group over time (P < 0.01); however, aerated samples retained significantly greater motility (70%) during the first 24 h after collection than samples in both the control (57%) and antibacterial group (51%). The addition of penicillin–streptomycin solution to spermic urine had a negative effect on viability; with significantly fewer sperm still alive 2–4 days post collection (P ≤ 0.032). Sperm viability was highly correlated with motility on all days and with forward progression 1–4 days post collection (P ≤ 0.002). Our results show that aerating amphibian spermic urine samples may provide a simple and low-cost method to improve sperm storage that could be used for in vitro fertilization and ex situ management of threatened amphibians. Antibiotics appeared to have a negative effect on sperm viability, suggesting that further research on bacterial contamination and antibiotic doses is necessary.

► We collected sperm non-invasively from Fowler's toads and stored it at 4° C.
► We tested whether aeration or antibiotics would improve short-term sperm storage.
► Regardless of treatment, sperm motility declined significantly over time.
► Aeration improved maintenance of sperm motility for 24-hours post-collection.
► The addition of antibiotics did not improve short-term storage of sperm.