The influence of metabolic rate, temperature and sex on life history parameters.
AuthorVan Voorhies, Wayne Alan.
Committee ChairThomson, Donald A.
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractMy dissertation research focused on four major biological variables; metabolic rate, body size, sex, and death. I found that growth and metabolic rate are not significantly correlated in the fish Oreochromis hybrid. To study factors affecting body size I researched the causal mechanism of Bergmann size clines. This is the trend that organisms tend to increase in body size with increasing distance from the equator. I found that genetically identical nematode worms, Caenorhabditis elegans, grow almost 40% larger at 10°C than at 25°C. Since adult worm cell number is constant in these worms the larger worm size is probably due to increased cell size. This provides a simple developmental mechanism, cells grow larger at lower temperatures, for Bergmann size clines in ectotherms. This would provide a simple non-adaptive explanation for the general trend of increased body size in ectothermic animals with increasing latitude. Sex significantly decreases the average lifespan of wild type male C. elegans but does not significantly affect hermaphrodite lifespan. I compared lifespans in three groups of worms: (1) all males, (2) all hermaphrodites, (3) a mixed population of hermaphrodites and male worms. At 20°C unmated males have an average lifespan 33% greater than mated males. In contrast, lifespans of mated and unmated hermaphrodites were identical. This result contradicts theories concerning the relative cost of reproduction which predict that large oocytes should be much more costly to produce than small sperm. I examined the lifespan of worms with a mutation affecting sperm production to determine if sperm production, rather than the physical effort of mating, is the major factor reducing lifespan in mated male worms. Average lifespan of both mutant mated males and unmated hermaphrodites is about 65% longer than that of wild type worms. Mated spe-26 males have similar lifespans to their unmated counterparts. These surprising results indicate that sperm production rather than ooycte production or the physical effort of mating is a major factor reducing lifespan in C. elegans.
Degree ProgramEcology & Evolutionary Biology