A Theoretical Study of the Photoluminescence in the Eyes of Trilobites Under Natural Lighting and its Effect on Their Vision
Abstract
Trilobites had a unique visual system in which the focusing component of their compound eyes were calcite crystals. Biogenic calcite emits photoluminescence (PL) in the blue-green part of the visual spectrum in all directions when excited by long-wavelength ultraviolet (UV-A) radiation. This PL had no information about the image being formed by the incident light from objects (such as other animals and rocks) near the trilobite and would have acted as stray light, thereby obscuring its vision. The PL spectrum from biogenic calcite from extant red algae is used to model the PL emitted by the calcite in the eyes of trilobites. The visible range and the wavelength sensitivity of the extant marine crustacean Squilla empusa (a distant living relative of the trilobites) is used to model the vision of trilobites. In the first theoretical calculation, the magnitude of this PL is estimated using data from extant red algae (including the concentration of its PL centers) and is compared to the expected photon noise in the visible sunlight directly from the illuminated objects. Due to the differences in the transmission of visible and UV-A light by seawater, PL stray light obscuration is expected to lessen with depth. A second more general calculation determines the dependence of this obscuration effect on ocean depth, independent of the concentration of PL centers in the calcite, showing that the obscuring effect of PL diminishes with depth. This PL is insignificant at 10 meters deep and, possibly, at all depths.
How to Cite:
Lee, S., Żylińska, A. & Collins, R., (2025) “A Theoretical Study of the Photoluminescence in the Eyes of Trilobites Under Natural Lighting and its Effect on Their Vision”, The Ohio Journal of Science 124(2), 52-72. doi: https://doi.org/10.18061/ojs.v124i2.9609
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