Project: Collaborative Research: Visual adaptations in hydrothermal vent shrimp and the role in feeding modalities and habitat selection

NSF Award Abstract:
Hydrothermal vents have given rise to remarkable marine ecosystems that contain organisms with specific adaptations for surviving in this extreme environment. Alvinocarid decapod shrimp are among the most abundant animals inhabiting these habitats and can be found in massive swarms at Pacific, Indian and Atlantic vent sites. Different species are found at different vent sites; and when species occupy the same vent site, some species are found close to the vents, with others on the periphery. Previous studies have demonstrated that vent shrimp species with enlarged eyes on their backs rely primarily on carbon provided by bacteria on the sides of black smokers, while others with fused, forward-facing eyes are predators/scavengers, around the vent periphery, suggesting that there may be a correlation between eye structure, feeding mode and habitat selection. However, adult vent shrimp are thought to be blind, but this conclusion may have resulted from the eyes being severely damaged due to collections under extremely bright submersible lights. Using methods the PIs have developed over decades to collect deep-sea species with extremely sensitive visual systems without blinding them, the visual systems of vent shrimp will be examined. These studies will be coupled with a systematic survey of pelagic and benthic light production (luminescence – both non-living chemiluminescence and triboluminescence as well as biological bioluminescence) at the vents to determine if vent shrimp can see any of these light sources. The results of this research will significantly advance the fields of vent biology and visual ecology, potentially transforming our current understanding of how light is generated at vent sites and how animals use this light to survive, as well as providing possible hypotheses as to how vent shrimp find these locations, and why different vents (diffuse, white smokers, black smokers) are dominated by different shrimp species. This proposal will support three graduate students, one postdoc and six undergraduate students, and outreach will be extended to secondary schools in underserved regions in three states by creating curriculum and activities correlated with this research that will help teachers blend this research into their STEM curricula.

Originally described as eyeless, vent shrimp are now known to undergo dramatic transformations in eye morphology with some species having massive fused eyes on their backs (dorsal eyes), while others have fused anterior eyes, and these different eye structures may be correlated with their feeding preferences. However, all the structural studies that have been undertaken on the benthic adults suggest that they are blind or the eyes are degenerating. In addition, the supposition that the vent environment lacked enough ambient light to make the metabolic costs of vision worthwhile supported this conclusion. Other structural studies, however, demonstrated that the pelagic post-larvae/juveniles have stalked eyes with normal ultrastructure, and it is therefore unlikely that the metamorphosis from normal stalked eyes (post-larvae) to the huge dorsal eyes (adults) results in a degenerated eye. The “degeneration” likely resulted from photoreceptor destruction occurring during collections of benthic adults under extremely bright submersible lights. There may also be several sources of sufficient ambient light produced by both abiotic triboluminescence/chemiluminescence as well as bioluminescence. Although several studies suggest bioluminescence does not exist at these vent sites, incorrect methodology may have resulted in this conclusion. This project will use genetic techniques to allow for post-larvae-adult matching; physiological experiments to provide information on photosensitivity (absolute sensitivity as well as color sensitivity, as there has been speculation that the benthic adults may be able to see infrared light) in both post-larval and adult shrimp; ultrastructural techniques to characterize eyes collected in the dark as well as under bright submersible lights; and low-light imaging techniques to examine sources of abiotic and biotic light in the vent environments. These data will be utilized together with computation modeling to determine if vent light sources are visible to hydrothermal vent shrimp eyes over relevant distances. These unusual visual systems of vent shrimp, likely serving as extremely sensitive light receptors, may also serve as a model for low-light camera systems, much as the optics of lobster eyes served as a model for designing an ultra-sensitive X-ray telescope.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.