Does reproductive effort influence the metabolic rate of Tomodon dorsatus snakes?

Abstract

In Squamate reptiles, vitellogenesis in females is marked by an increase in the number and size of follicles, leading to an increase in aerobic metabolism to support the rising energy demand during reproductive activity. Male gametes are smaller than female gametes, and spermiogenesis requires less energy than vitellogenesis. This investigation compares the relationship between aerobic metabolism and reproductive effort in male and female viviparous Tomodon dorsatus snakes. We evaluated the influence of the males' and females' reproductive stages, along with the masses of follicles and testicles, on their aerobic metabolic rate. Our findings show that females have higher maintenance cost of pregnancy than metabolic costs of vitellogenesis. In males, we found no evidence of the reproductive effort influencing aerobic metabolic rates. In T. dorsatus, females have a long period of development and high fecundity. Therefore, the metabolic costs of vitellogenesis represent a critical component in the reproductive effort. On the other hand, males of T. dorsatus maintain a similar mass of gonads throughout the year with constant energy demand. These results reflect the difference in reproductive efforts between females and males of T. dorsatus.

Interactive effects of intrinsic and extrinsic factors on metabolic rate

“…[263,264]) multiple intrinsic factors mode of thermoregulation (e.g. [1,20,23,24,64,72,117,118]) behaviour and thermoregulatory mode (e.g. [159]) light and air versus water (e.g.…”

“…They include significant effects of taxonomic affinity, cell size (including cellular mode of growth), genome size, genotype, gender (sex), activity level, mode of locomotion, mode of thermoregulation, growth rate, lifehistory stage, body shape, food processing (specific dynamic action), reproductive state, reproductive strategy, molt-cycle phase, body composition and social behaviour on the bodymass scaling exponent (b) for metabolic rate (see table 1). Other interactive effects of intrinsic factors on metabolic rate include colony size and connectedness [117], gender and reproductive effort [118] and trinary interactions among body size, genotype and life-history stage [43]. Hypothetical mechanisms underlying many of the various interactive effects of body size and other intrinsic factors on metabolic rate are described in table 1.…”

“…decreases in relative masses of organs/tissues with high metabolic costs, including brain, heart, liver and kidneys, but increases in relative masses of metabolically inexpensive tissues, such as fat, connective, skeletal and resting muscle tissues)[8,34,82,83,85,111–116]body size and social behaviourvariablehuddling behaviour alters the mass-scaling of resting metabolic rate in small mammals because huddle surface area primarily determines heat loss and thus compensatory metabolic heat production, rather than individual surface area[8]body size, genotype and life-history stagevariableontogenetic shifts in the mass-scaling of metabolism vary with genotype in Drosophila , apparently owing to variable developmental timing in switching from anaerobic to aerobic ATP production[43]colony size and connectednessnegativezoid connectedness increases metabolic rate more in small than larger ascidian colonies. The mass-scaling exponent is near 1 in unconnected colonies, but less than 1 (0.80) in connected colonies, possibly owing to interactive effects among the zooids[117]gender and reproductive effortpositive for femalesreproductive effort increases metabolic rate in female, but not male snakes ( Tomodon dorsatus ), presumably because of the high energy cost of egg production[118]behaviour and thermoregulatory modestronger in ectothermsrelationships between metabolic rate and behavioural traits are generally stronger in ectotherms than endotherms[119] interactive effects of extrinsic factors type direction of interactive effect a underlying mechanism selected sources temperature and salinitynegative or complexthermal response of metabolic rate decreases (or shows complex relationships) with increasing salinity. Higher temperature speeds up metabolism, whereas higher salinity reduces osmoregulatory metabolic demand in marine organisms.…”