A PRELIMINARY BACTERIOLOGICAL STUDY OF REFRIGERATED CHANNEL CATFISH SPERM

This study was designed to simulate conditions encountered routinely d uring refrigerated storage of channel catfish sperm. Sperm samples wer e stored at 4 C in non-sterile and sterile Hanks' balanced salt soluti on CHESS). Non-sterile HBSS was prepared with distilled water stored f or 2 wk in a plastic carboy prior to use. Observations were made on th e frequency and abundance of bacteria in samples, and on changes in sp erm motility and quality. Sperm samples stored in non-sterile HBSS had a complete loss of motility within 72 h. Samples maintained in steril e HBSS showed an initial decrease in motility between 48 and 72 h, and a complete loss of motility within 10 d. Quality of the sperm in each buffer decreased as motility decreased; morphologic changes and reduc ed motility of sperm were coincident with increased bacterial numbers. Bacteria were cultured on tryptic soy agar and Pseudomonas F agar (PF A) by spread-plating 10-mu L aliquots from each sample onto bacteriolo gic media and incubating for 5 d. The dominant bacteria observed were members of the genus Pseudomonas, representing 67% of the total bacter ia identified. The dominant pseudomonad (Pseudomonas sp.! cultured fro m sperm samples stored in sterile buffer produced caseinase, lecithina se, and was beta-hemolytic, whereas the dominant bacteria (P. putida) cultured from samples stored in the non-sterile buffers did not. Highl y motile pseudomonads, present in two samples stored in sterile buffer , colonized below the surface of the PFA media at 4 C. The attributes of the bacterial contaminants that likely contributed to the decrease in sperm quality were production of extracellular enzymes, consumption of oxygen, and a high level of motility. Potential sources of degrada tive bacteria were commensal Bora of channel catfish and the water use d in preparing the storage buffer.