Sperm Parameters Associated with Reproductive Ecology in Two Snake Species

Abstract

The effect of temperature on sperm dynamic parameters in ectotherms in general, and reptiles in particular, remains poorly understood due to the lack of consistent evidence. As a group, snakes show considerable variability regarding mating systems, male reproductive behavior, thermoregulatory behavior, and preferred temperatures. Additionally, snakes present significant variability in sperm competition levels, which is determined by the species mating system. Because sperm longevity, motility, and velocity are positively related to reproductive success in both competitive and noncompetitive conditions, the sperm physiology of ectothermic organisms may functional optimally at ecologically relevant temperatures. The objective of this work was to analyze the effect of an ecologically plausible range of temperatures on sperm dynamic parameters of two species of snakes with contrasting mating systems and sperm competition levels: Boa constrictor occidentalis and Waglerophis merremii. To accomplish this, an in vitro incubation approach was used: sperm dynamic parameters (i.e., motility and velocity) were measured on sperm solution aliquots incubated at 25uC, 30uC, and 37uC for up to 10 h by means of a phase contrast video microscopy system. Results suggested that although an increase in temperature has a general negative impact on sperm motility and velocity, the two species studied present different degrees of sensitivity to high incubation temperatures. Moreover, these differences can be explained by the dissimilar thermal conditions that the sperm of the two species would experience during their reproductive seasons, which are a consequence of the differences in their reproductive behavior. In conclusion, sperm motility and swimming velocity respond mainly to environmental conditions imposed by mating systems rather than to selection by sperm competition.

Relationship between pre- and post-copulatory traits inSalvator rufescens(Squamata: Teiidae)

“…Sperm samples were collected in a 1.5 mL plastic tube containing 90 lL of phosphate-buffered saline (PBS). Sperm concentration was determined using a Neubauer chamber and the samples were diluted to a concentration of 1 9 10 6 cells mL À1 in Biggers, Whitten, and Wittingham culture medium (Biggers, Whitten & Whittingham, 1971) supplemented with 4% bovine serum albumin (Tourmente, Giojalas & Chiaraviglio, 2011b).…”

“…Sperm aliquots (500 lL) were incubated at 25°C in a thermally stable water bath for 30 min (Tourmente et al, 2011b;Blengini et al, 2014). Sperm suspension (20 lL) was placed in a plastic observation chamber and covered with a coverslip.…”

Sperm physiology and quality in two marine teleosts: Anguilla anguilla & Takifugu niphobles

“…The differences in the biology of fish and mammalian spermatozoa may explain the delay in the release of adequate tools for the measurement of sperm motility in fish. To date, these systems have been used and validated in a wide range of animal groups such as marine invertebrates (Gallego et al, 2013), birds (Kleven et al, 2009), marine mammals (Montano et al, 2012), reptiles (Tourmente et al, 2011) or even insects (Al-lawati et al, 2009).…”

Improvement of techniques for sperm evaluation and cryobanking in European eel.

“…The development of CASA-Mot systems started in the 70s in mammalian sperm studies, and in the 90s the method was adapted for it use in fish spermatozoa studies (Perchec et al, 1995;Toth et al, 1995). To date, these systems have been used and validated in a wide range of animal groups such as marine invertebrates, birds, marine mammals, reptiles or even insects (Al-Lawati et al, 2009;Lüpold et al, 2008;Montano et al, 2012;Riesco et al, 2017;Tourmente et al, 2011).…”