Date of Award

Summer 2024

Document Type

Open Access Thesis

Department

Biological Sciences

First Advisor

Daniel Speiser

Abstract

Eyes are physiologically costly organs to produce and maintain, making the development of secondary eyes intriguing. Caridean shrimp possess reflecting superposition primary eyes, but some species across fourteen families possess an additional pair of eyes called accessory eyes along the dorso-posterior margin of the primary eyes. Secondary eyes are found in lizards, lampreys, and insects, where they often function as illumination detectors. Some shrimps may use accessory eyes to signal endocrine organs in their eyestalks to alter the pigmentation of their carapace providing better camouflage through disruptive coloration. To investigate the role of accessory eyes in dynamic color change we placed individuals of Palaemon vulgaris on black or white backgrounds under bright, dim, and dark lighting conditions. We then blindfolded the accessory eyes of individuals of P. vulgaris and exposed them to the same black or white backgrounds under brightly lit conditions. We found that the red pigment within the chromatophores of the carapace dispersed on black backgrounds and concentrated on white backgrounds under lit conditions. There was no difference in the pigmentation on black or white backgrounds in animals kept in darkness. In blindfolded animals, we found no difference in pigmentation between animals with their accessory eyes covered and animals that received sham treatment. We determined that there was no effect of blindfolding on the appearance of the animal across black or white backgrounds. Control of the animal’s pigment could have been maintained by light diffusing through the glue used to secure the blindfolds. It is also possible that the surgery caused the animal stress, reducing its physiological responsiveness or that the role of regulating pigment dispersal can be maintained by either set of eyes. The results of this study show that eliminating spatial resolution from the accessory eye has no effect on pigmentation. Future studies into the function of accessory eyes should focus on severing the nerves leading away from the accessory eyes and observing any behavioral or physiological changes in the animal.

Rights

© 2024, Nicholas Raymond Steichmann

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