Exceptional long-term sperm storage by a female vertebrate

Area of Science:

• Reproductive Biology
• Herpetology
• Evolutionary Biology

Background:

• Females of many vertebrate species can store sperm long-term, impacting mating systems and sexual selection.
• Reptiles, especially turtles and squamates, frequently exhibit long-term sperm storage.
• Distinguishing sperm storage from facultative parthenogenesis requires genetic analysis of offspring.

Purpose of the Study:

• To investigate the duration of long-term sperm storage in a female Western Diamond-backed Rattlesnake (Crotalus atrox).
• To genetically confirm paternal contribution to offspring, thereby excluding facultative parthenogenesis.

Main Methods:

• A wild-collected female Crotalus atrox was housed in isolation after capture in September 1999.
• Offspring from litters produced approximately one and six years post-capture were genetically analyzed.
• Paternal alleles were identified in the 2005 litter to determine paternity.

Main Results:

• The female produced two litters, one and six years after capture, while isolated from males.
• Genetic analysis of the 2005 litter confirmed paternal genetic contribution in all offspring.
• Facultative parthenogenesis was rejected as the sole explanation for reproduction.

Conclusions:

• The study demonstrates long-term sperm storage in a female vertebrate lasting approximately six years (71 months).
• This represents the longest documented period of sperm storage resulting in viable offspring in a vertebrate.
• The findings have significant implications for understanding reptilian reproductive strategies and post-copulatory sexual selection.