Biology ETDs

Publication Date



Life history and behavioral information on North American isopods are limited and non-existent for the genus Thermosphaeroma. The habitat of T. thermophilum allows easy and accurate collection of field and laboratory data. The relative absence of complicating evolutionary contexts facilitates investigation of sexually selected behavior and morphology. Males are larger than females. Reproduction and mortality are somewhat seasonal. Sex ratio is consistently male-biased, which is attributed to male searching for mates and avoidance of males by non-reproductive females. T. thermophilum is omnivorous. Reproductive timing by females and its contribution to sexual dimorphism are discussed. Males choose mates by size and reproductive condition. Precopulatory guarding of females occurs and males preferentially guard recently molted females. Single males attempt to usurp females from guarding males. Large males are more successful at usurping and resisting usurpation, and guard larger females. Female choice and incitation of male competition are discussed.

Key words: Socorro Isopod, Thermosphaeroma, life history, mate selection, precopulatory guarding, mating success, sex ratio, sexual dimorphism, sexual selection.

Project Sponsors

The New Mexico Department of Game and Fish grants 516-65-18 and 519-66-09



Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

Albert Randolph Thornhill

Second Committee Member

J. David Ligon

Third Committee Member

Manuel C. Molles

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Biology Commons