P2.153 Thursday, Jan. 5 Pupillary light reflex in the Atlantic brief squid, Lolliguncula brevis MCCORMICK, L. R.*; COHEN, J. H.; Eckerd College, St. Petersburg, FL; University of Delaware, Lewes, DE email@example.com
Coleoid predation is highly visual and requires an eye capable of imaging visual targets in variable photic conditions. Pupillary responses are one feature that contributes to this visual flexibility in coleoids, although pupil responses have yet to be quantitatively documented for squids. The pupillary response of the Atlantic brief squid, Lolliguncula brevis, was analyzed by exposing individuals to alternating treatments of varying light intensities and periods of dark recovery while simultaneously recording the eye under direct and indirect light stimulation to determine whether the response was consensual between eyes. A pupil light reflex was measured, with an asymmetrical constriction observed under increasing irradiance levels that was largely consensual between eyes. The response threshold was 12.56 to 12.66 log photons/cm2/s. The spectral responsivity of the pupillary response was analyzed by measuring the magnitude of the pupil light reflex of the eye directly stimulated by light at equal quantal intensities at wavelengths throughout the visible spectrum. The response spectrum showed a maximum at 500 nm, which was best fit with a rhodopsin absorptance template having a λmax of 511 nm. When collectively examined in the context of the diel light environment in L. brevis habitat, these results show the sensory adaptation of L. brevis to a coastal environment, with a visual system well-suited for acuity during dusk, when there are rapid changes in irradiance and a peak absorbance of blue-green light (~500 nm). Whether the pupillary light reflex results from visual and/or non-visual photoreceptors remains an open question and will be discussed.