Graduation Date

Fall 2019

Document Type

Thesis

Program

Master of Science degree with a major in Biology

Committee Chair Name

Paul Bourdeau

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Bengt Allen

Second Committee Member Affiliation

Community Member or Outside Professional

Third Committee Member Name

Erik Jules

Third Committee Member Affiliation

HSU Faculty or Staff

Fourth Committee Member Name

Frank Shaughnessy

Fourth Committee Member Affiliation

HSU Faculty or Staff

Subject Categories

Biology

Abstract

Rocky intertidal zones are some of the most thermally stressful environments on earth, where ectotherms deal with tidal fluctuations in air and water temperatures that can exceed thermal performance limits. However, not all intertidal ectotherms face the same exposure risk. On the northwest coast of the United States, summertime low tides occur during midday, exposing ectotherms to stressful temperatures. In contrast, cooler pre-dawn low tides in southern regions buffer ectotherms from thermal stress. Gumboot chitons (Cryptochiton stelleri) are a thermally sensitive intertidal grazer that range from southern California to Alaska, exposing them to a mosaic of thermal stress. I quantified chiton thermal performance limits in the laboratory, by testing the effects of elevated water and air temperatures on grazing. I also compared the thermoregulation efficiency of chitons from thermally-benign northern California (CA) sites with those from thermally-stressful San Juan Island (SJI), Washington sites using three components: 1) biomimetic thermal models deployed intertidally at three sites each in CA and SJI; 2) chiton body temperatures in the field; and 3) chiton thermal preference in a laboratory-based thermal gradient. I found that chiton thermal performance was reduced at 18℃ in water and reached their thermal performance limit at 20℃ in air, confirming previous work documenting thermal performance limits on gumboot chiton respiration. I also found that preferred temperatures of chitons were close to their thermal performance limits, but that they rarely achieved body temperatures that would maximize their performance in the field. This suggests that chitons are thermoregulating inefficiently with respect to maximizing performance, but instead may be minimizing exposure to detrimental thermal extremes.

Citation Style

APA

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