Effects of weathered crude oil on visual function in sheepshead minnow

Larval sheepshead minnow (4, 6, 8 dph) were assessed for visual acuity using behavioral and morphological assays. Optomotor response was determined using a rotating drum apparatus to determine a flicker-fusion threshold. Behavioral tests were video recorded and analyzed for maximum rotational speed of larvae exhibited during the assay. Larvae were subsequently preserved and sectioned histologically to determine alteration in retinal layers due to oil exposure, with sections photographed and examined using ImageJ (v1.47). This is the first study to find physiological impairments to the visual system in larval fish and relate them to behavioral-level impacts. We found that embryonically-exposed sheepshead minnow larvae exhibited a reduced optomotor response, subsequently having reduced retinal layers important in visual function and image processing.