Life history tradeoffs and the costs of reproduction in Arizona Bark Scorpions (Centruroides sculpturatus)

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Webber, Michael Marie
Arizona Bark Scorpions; Bioenergetics; Centruroides; Centruroides sculpturatus; Reproduction; Scorpions; Arizona Bark Scorpions; Bioenergetics; Centruroides; Centruroides sculpturatus; Reproduction; Scorpions; Animal Sciences; Biology; Medical Physiology; Other Animal Sciences; Physiology
thesis / dissertation description
Tradeoffs in life history evolution result from conflicts in the time and energy that can be simultaneously invested in activities such as growth, reproduction, and survival. Reproduction is an energetically costly activity for organisms, and is known to elicit alterations in the daily activity patterns of individuals. I investigated reproductive tradeoffs in the Arizona Bark Scorpion,Centruroides sculpturatus. To better understand the nature of tradeoffs in this species, I examined the influence of reproductive state on the predatory efficiency and thermal preference of reproductive females. Further, I examined the influence of reproductive activities (i.e. gestation) on the ability of reproductive females to conserve water at high temperatures. Finally, I used morphometric analyses to investigate tradeoffs in weapon and ornament allometry in male and femaleC. sculpturatus. To examine tradeoffs that occurred between reproductive activities and the predatory efficiency of femaleC. sculpturatus, I conducted prey handling trials of non-gravid and gravid females and compared the time it took them to successfully capture and subdue a prey item (Common House Cricket,Acheta domesticus). Using Survival Analyses, I determined that pregnancy did not significantly reduce the predatory efficiency of gravid femaleC. sculpturatus, which suggests that gravid females can maintain their predatory abilities despite significant increases in body mass and the physiological costs associated with gestation. However, all femaleC. sculpturatusexhibiting maternal care (i.e. carrying offspring) were unable to capture prey during the trial period, suggesting that brooding behaviors incur substantial energetic costs for femaleC. sculpturatus. Thus, femaleC. sculpturatusexperience a tradeoff between caring for current offspring and their ability to acquire resources during the brooding period. Next, to examine the influence of reproductive state on the thermal preference of females, I designed and constructed a thermal gradient, and recorded the body temperatures (Tb) of non-gravid and gravid females over a 24 hour period. Using Profile Analysis, I documented that gravid females selected significantly higher diurnal and nocturnal Tb than non-gravid females. The selection of higher Tb by gravidC. sculpturatusmay improve offspring fitness by facilitating favorable temperatures for embryonic development. However, the preferred Tb of gravid females was close to their critical maximum temperature, which may significantly increase their risk of heat-induced mortality. The morphological (increased body mass) and physiological (increased metabolic rate) changes that occur in reproductive females can increase their susceptibility to water loss, compared to non-reproductive females. To compare rates of water loss between non-gravid and gravid females, I measured their water loss rates using flow-through