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An Analysis of the Temperature Size Rule in Ectotherms


Biologists have long been interested in the dynamic relationship between organism development and environmental temperature. Coined in nature as Bergmann size clines, and in the lab the Temperature Size Rule, the vast majority of animals exhibit larger body sizes at cooler temperatures (~lower latitudes) and smaller body sizes are warmer temperatures (~higher latitudes). While this can be considered a rule for endotherms which have evolved thermogenesis, ectotherms, who are at the mercy of the temperature of their immediate environment, have unique and disparate responses. Using the humble roundworm genus Caenorhabditis, we show that indeed there is no robust pattern of developmental response to temperature. And moreover, the temperature size rule can be better thought of as simply a reflection of rearing temperatures compared, which can be modeled as a bell distribution unique to an individual organism. We also look towards changes in reproductive strategy as the main driving factor effecting the responses shown. I propose a possible signaling pathway connecting changes in environmental temperature to changes in reproduction and longevity. Continuing prior research, we provide evidence in support of a Single Nucleotide Polymorphism (SNP) in a gene encoding a calcium dependent protease known as tra-3 attenuating C. elegans ability to maintain larger body sizes as temperatures decrease. I propose a reasonable mechanism by which the aforementioned SNP may be exerting its effects.

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