Collection of seasonally spermatozoa-rich semen by electroejaculation of laboratory woodchucks (Marmota monax), with and without removal of bulbourethral glands.
Male woodchucks were subjected to electroejaculation during the early- or mid-breeding season by a commercial stimulator and rectal probe (1.3 x 13 cm, with longitudinal electrode strips on one side) with electrodes oriented ventrally. A study of the voltage and stimulation parameters at a probe depth of 4 to 9 cm suggested that a series of 15 to 75 3-sec pulses of 3 to 6 V each could result in ejaculation and collection of semen. Pulses of only 1 to 2 V frequently caused erection but not ejaculation. Trials conducted on 12 bulbourethral (Cowper's) gland-intact males (n = 18 trials) versus six males from which Cowper's glands had been surgically removed (n = 18 trials) identified these glands as the source of urethral plugs in 77% of ejaculates from the gland-intact males and presumably the source of copulation plugs obtained from the vagina of female woodchucks. The fluid portion of ejaculates from both groups contained few or no spermatozoa. An additional 32 trials were conducted on 12 gland-intact males and eight males without Cowper's glands. These trials included 16 shallow (5 to 8 cm) versus 16 deep (10 to 13 cm) placements of the tip of the rectal probe in each group of males. In gland-intact males the stimulation of sacral (shallow) elements routinely resulted in the emission of large (200 to 300 microl) urethral plugs and fluid volume of 40 to 400 microl, containing few or no spermatozoa. In males without Cowper's glands the sacral stimulation typically produced volumes of 60 to 350 microl of noncoagulating liquid without urethral plugs, containing few or no spermatozoa. Lumbar (deep) stimulation in both groups of males usually resulted in fluid ejaculates, with 60% containing numerous spermatozoa (typically, 0.5 to 3 x 10(6)/ejaculate). Lumbar stimulation usually produced urethral plugs of little (50 to 100 microl) or no volume in gland-intact males and no urethral plugs in males without Cowper's glands. Ejaculates did not coagulate during handling or storage for 4 to 24 h. Serial lumbar stimulation of six males at 2- to 3-week intervals resulted in few spermatozoa, except for a 4- to 8-week period during which > or =0.25 x 10(6) spermatozoa/ejaculate and peaks of 5.3 +/- 2.4 x 10(6) spermatozoa/ejaculate were obtained. The results suggest that electroejaculation can be used to obtain spermatozoa-containing liquid that might be useful for semen evaluation or artificial insemination in laboratory woodchucks, that Cowper's glands are the source of urethral plugs in the ejaculates of this species, and that the fertile period of the male breeding season is limited to 4 to 8 weeks.
Concannon
P
P
Department of Physiology, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
Roberts
P
P
Parks
J
J
Bellezza
C
C
Tennant
B
B
D000818:Animals; D002030:Bulbourethral Glands / Q000502:physiology* / Q000601:surgery; D004542:Ejaculation; D004558:Electric Stimulation; D005260:Female; D008297:Male; D008392:Marmota / Q000502:physiology*; D012621:Seasons; D012661:Semen / Q000166:cytology*; D013076:Sperm Count