Sperm Mass Longevity and Sperm Storage in the Female Reproductive Tract of Plethodon shermani (Amphibia: Plethodontidae)

In salamanders in the seven families composing the Salamandroidea, sperm storage allows a female to obtain male sperm months before oviposition. This study reveals the ability of captive female Red-legged Salamanders, Plethodon shermani (Plethodontidae), to store and retain viable sperm for long periods of time. By staging male–female courtship trials, we found that a female’s retention of the male sperm mass is visible in her cloaca for up to 4 d (X̄ = 2.8 d). Given the prolonged breeding season exhibited by this species (>10 wk), it is unlikely that the sperm mass functions efficiently to prevent female remating in that season. In addition, oviposition and egg-rearing in the laboratory revealed that P. shermani females can store viable sperm in their sperm storage organs (spermathecae) for ≥9 mo. Histology and microscopy showed that a subset of females even retained sperm in their spermathecae after oviposition, but significantly less of their lumina were occupied by sperm compared with the lumina of females that did not oviposit. Finally, we documented that one captive female stored sperm in her spermatheca from an insemination that occurred 17 mo earlier. Thus, sperm from one breeding season may have the potential to interact with sperm obtained in a prior breeding season, which is a finding that has implications for the evolution of postcopulatory sexual selection in this species.