Vision and Bioluminescence of Marine Crustaceans

Abstract

The overarching theme of this dissertation research was to understand light as the cue for life in the ocean. I approached this dissertation with a background in molecular biology, animal behavior, and vertebrate opsin evolution, and upon my arrival was tasked with familiarizing myself with invertebrate opsins and bioluminescence. Chapter 1 briefly describes my rationale for this dissertation research and puts it into a broader context for understanding light as a cue for light in the ocean. Chapter 2 contains a literature review of the many multiple origins, forms and functions, cellular biology, and ecology of bioluminescence, with an emphasis on marine taxa. I point to recent discoveries in bioluminescent systems that challenge orthodoxies and present a systematic review of plausible human impacts on bioluminescence via ocean acidification. In chapter 3, I present a fully resolved molecular phylogeny for metridinid copepods, with an emphasis on the genus Pleuromamma, and characterize the opsin and luciferase diversity in the group using transcriptomics. Within the transcriptomes, I found evidence for the origin of copepod bioluminescence possibly arising from a blood clotting protein. In chapter 4, I used immunohistochemistry to localize opsin proteins in ocular and non-ocular tissues from four species in the superfamily Oplophoroidea, a group of bioluminescent decapod shrimp. These data provide molecular confirmation for previously described single- and dual-sensitivity visual systems in the superfamily, and offer the first evidence for co-localization of opsins in the R8 cells – or distal rhabdom – of a decapod crustacean retina. In chapter 5, I sequenced metatranscriptomes from zooplankton communities at Station ALOHA, Oʻahu, Hawaiʻi to describe community structure across the epipelagic and lower mesopelagic during the day and night for small and large zooplankton. We found that Station ALOHA was dominated by copepods, followed by euphausiids, amphipods, and ostracods, with a faunal shift toward fishes in large bodied, deep samples, and time of day had no influence on overall community structure. Further, we tested the utility of metatranscriptomes for functional analysis leveraging gene expression estimates of the opsin gene family. We found that opsin abundance does not conform with community patterns and that depth, size, and taxa influenced opsin expression, but time of day had no effect. Combined, these chapters leverage tools at multiple levels of organization to understand why bioluminescence is such a prevalent phenomenon throughout the worlds oceans, and to understand how visual ecology structures where species are horizontally, temporally, and vertically through the water column.