How temperature affects nudibranch partial predation of Dendrobeania lichenoides bryozoan

Abstract

Bryozoan colony structure (Dendrobeania lichenoides) of degenerated parts known as brow bodies helps determine the grazing pattern and partial predation by nudibranchs (Dirona albolineata and Dirona pellucida). Although previous studies have explored the facets of partial predation of bryozoan colonies from various nudibranch species, the temperature is not often considered an external factor affecting their consumption of colonies. Three feeding trials under increasing temperatures (14 ℃, 18 ℃, and 20 ℃) were run in Friday Harbor Laboratories, Friday Harbor, WA. Dirona albolineata and Dirona pellucida nudibranchs were fed Dendrobeania lichenoides colonies in laboratory conditions to determine if being introduced to increasing temperature levels affected their partial predation. Results showed a positive correlation between increased colony consumption and increased temperature with nudibranchs grazing closer to the center of the bryozoan colonies up until 18 ℃, after which that correlation decreased. Statistical analysis showed no significant difference between the overall means of each trial, but there was a significant decrease in bryozoan colony consumption after 18 ℃. Nudibranchs are resilient to temperature, but 18 ℃ could be the threshold they can reach before their activity is affected by temperature. This study indicates that increases in seawater temperature do not necessarily dictate that nudibranchs stop partially consuming bryozoan colonies. However, they suggest that nudibranchs have a temperature tolerance ceiling that, if breached, will affect their behavior.