LE3 .A278 2022

2022

Currie, Suzie

Acadia University

Bachelor of Science

Honours

Biology

Biology

Climate chaos is expected to grow in severity. We have a limited understanding on how aquatic life is responding to warming, natural fluctuating temperatures. To address this gap in knowledge, we capitalized on the unique reproductive strategy of the self-fertilizing, amphibious, mangrove rivulus (Kryptolebias marmoratus) to determine the morphological consequences of chronic, ecologically relevant thermal variation on fish gills. We acclimated these fish to three different thermal regimes: 1) control (27 ̊C +/- 2 ̊C), 2) predictably fluctuating thermal cycle (27 ̊C - 35 ̊C), and 3) unpredictably fluctuating thermal cycle (27 ̊C - 35 ̊C). We first measured ventilation frequency and found significant increases in both the fluctuating conditions when compared to control for 1 lineage. We know that the gills of several fish species remodel with temperature, and specifically, gill surface area increases with exposure to stable, warm temperature. This increase in surface area is a result of the retraction of the interlamellar cell mass (ILCM). However, we do not know if the gills will remodel in the same way when exposed to regular temperature fluctuation. To this end, we sectioned and stained gills to measure the ratio of ILCM height to lamellar length and lamellar surface area. We found significantly more ILCM coverage in the unpredictable and predictable thermal regimes when compared to the control group. Furthermore, lamellar surface area was significantly reduced within the thermally fluctuating groups, being the lowest within the predictable group. My findings show, for the first time, that gill surface area is reduced in warming, fluctuating environments. It may be that in warm, variable thermal environments, the energetic requirement of ion regulation is more costly than reduced oxygen uptake. Under these conditions, fish can reduce these costs by increasing ILCM coverage and decreasing gill surface area.

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https://scholar.acadiau.ca/islandora/object/theses:3778