Date of Award

8-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

Committee Chair/Advisor

Dr. Rick Blob

Committee Member

Dr. Heiko Schoenfuss

Committee Member

Dr. Sam Price

Committee Member

Dr. Kara Powder

Committee Member

Dr. Brooke Flammang

Abstract

Adhesive systems have evolved in many animal lineages and have appeared multiple times among the fishes. Bioadhesion in the gobies, a group found around the world, plays a role in both station-holding and even climbing. Among the Hawaiian streams, we find four species of amphidromous gobies which must face predators as juveniles and climb streams up to hundreds of feet tall to reach adult habitats. These gobies exhibit a range of climbing and adhesive abilities that result in an elevation-dependent species stratification, in which increasingly proficient climbing species are found in streams at increasingly higher elevations. This group is therefore an especially interesting group to study to understand what contributes to their ability to climb and adhere. This knowledge can offer insights to the form and function relationship in these species and other adhesive fishes, as well as offer inspiration towards biomimetic adhesives. This dissertation sought to explore factors that contribute to the adhesive abilities of the Hawaiian gobies in hopes of offering insights to the group’s morphology. The passive adhesive forces of these four species’ suction discs were tested on a variety of surfaces ranging in physical properties such as roughness and polarity, revealing that polarity does not affect adhesion, but rougher substrates enhance adhesion across species. Passive adhesion is strongest in the better climbing species, suggesting that their morphology allows for greater tenacity without additional biomechanical effort. Using this knowledge, I designed bio-inspired suction cups to better understand whether the overall shape of the suction disc or the internal skeletal supports could contribute to tenacity. While the shape of the internal skeleton did not contribute to the overall performance of the suction cups, the shape of the suction cups did affect tenacity. Finally, the potential role of mucus on adhesion was explored through histological and biochemical tests on all species and across ontogeny. While mucus production appears to be greater in areas that are used for adhesion, it may not be exclusively for the purpose of adhesion itself, but rather for protective effects against friction. Taken together, this body of work builds on our understanding of the form and function relationship in animals that experience extremely demanding environments.

Author ORCID Identifier

https://orcid.org/0000-0002-9908-3103

Available for download on Sunday, August 31, 2025

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