State-dependent, visually-guided behaviors in the nudibranchBerghia stephanieae

Abstract

Nudibranch molluscs have structurally simple eyes whose behavioral roles have not been established. We tested the effects of visual stimuli on the behavior of the nudibranchBerghia stephanieaeunder different food and hunger conditions. In an arena that was half shaded, animals spent most of their time in the dark, where they also decreased their speed and made more changes in heading. These behavioral differences between the light and dark were less evident in uniformly illuminated or darkened arenas, suggesting that they were not caused by the level of illumination.Berghiaresponded to distant visual targets; animals approached a stripe that was at least 15° wide and 50% darker than the background. They did not approach a stripe that was lighter than the background but approached a stripe that was isoluminant with the background, suggesting the detection of spatial information. Animals travelled in convoluted paths in a featureless arena but straightened their paths when a visual target was present even if they did not approach it, suggesting that visual cues were used for navigation. Individuals were less responsive to visual stimuli when food-deprived or in the presence of a food odor. Furthermore, when given a food odor, they had a weaker preference for the dark and behaved similarly in the light and dark. Thus,Berghiaexhibits visually-guided behaviors that are influenced by odors and hunger state.

Social predation by a nudibranch mollusc

“…Although was an effect of the assay type on the latency to select an anemone (F(3) = 8.851, p = 1.89e-05), this was not a main effect of interest (Supplementary Table S2). Slugs that were acclimated in ATW were faster to choose an anemone (F(1) = 18.578, p = 2.88e-05), likely due to heightened arousal from the scent of their prey prior to entering the arena, which differs from previous findings that fooddeprived slugs in an empty arena move slower when presented with a food odor (Quinlan and Katz, 2023). This effect interacted significantly with their choice (F(1,1) = 5.864, p = 0.0166), such that their latency was impacted the most when the slugs selected control anemone and ATW acclimation caused them to choose faster.…”