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Date of Award
Summer 2025
Document Type
Masters Thesis
Department or Program Affiliation
Marine and Estuarine Science
Degree Name
Master of Science (MS)
Department
Biology
First Advisor
Arellano, Shawn M.
Second Advisor
Bingham, Brian L., 1960-
Third Advisor
Schwarz, Dietmar, 1974-
Fourth Advisor
Hourdez, Stéphane
Abstract
Understanding ecosystem dynamics and trophic interactions are critical components of environmental conservation. The dynamic conditions found at deep-sea hydrothermal vents offer an exceptional opportunity to study, document, and describe the influence of environmental factors on ecological relationships, namely symbioses. Vent systems are characterized by intricate organism interactions, particularly symbioses, that contribute substantially to ecosystem biodiversity and can act as important moderators for organismal fitness and evolution. However, many symbiotic interactions are not well understood. One particularly important deep-sea symbiosis exists between foundational bathymodiolin mussels and the large Branchipolynoe spp. scale worms that inhabit the mussel’s pallial cavity. Bathymodiolin mussels are crucial ecosystem modifiers who occupy a wide variety of chemosynthetic microhabitats due to their unique physiology, which allows them to supplement their nutrition from chemoautotrophic gill symbionts with siphoned particulate matter. However, despite the importance of these mussels, and the prevalence of their symbiosis with Branchipolynoe spp. worms, many questions still exist regarding the details of their relationship. In this study we investigated the intricacies of the symbiosis between Branchipolynoe symmytilida worms and their Bathymodiolus thermophilus mussel at East Pacific Rise (EPR) hydrothermal vents, where the ecology of this symbiosis is largely undescribed. We used a combination of models to assess worm presence, abundance, and demographics across two biogenic zones. In tandem we conducted a comparative analysis using 16s rRNA metabarcoding to better understand symbiont worm food sources. Finally, we conducted a condition index analysis to investigate the impact of housing a worm on the host mussel’s health. We document sexual dimorphism and differential abundance between male and female B. symmytilida at the East Pacific Rise. Our observations suggest that the worms exhibit a selective affinity for host mussels within the Riftia zone. The results of our gut content analysis support kleptoparasitism as a potential method of feeding for these worms, though pseudofeces consumption is an alternative explanation. Finally, the results of our condition index analysis suggest that the impact on B. thermophilus of housing a symbiotic worm changes throughout the ontogeny for B. symmytilida and may suggest the symbiotic role of the worm shifts through development. Our study offers a valuable snapshot of the mussel-worm dynamics at the East Pacific Rise and contributes the base of knowledge surrounding the Bathymodiolus – Branchipolynoe spp. associations documented globally.
Type
Text
Keywords
Symbiosis, Hydrothermal vent, East Pacific Rise, Bathymodiolus thermophilus, Branchipolynoe symmytilida
Publisher
Western Washington University
OCLC Number
1534575222
Subject – LCSH
Symbiosis--East Pacific Rise; Hydrothermal vent ecology--East Pacific Rise; Hydrothermal vents--East Pacific Rise; Marine ecology--East Pacific Rise; Mytilidae--East Pacific Rise
Geographic Coverage
East Pacific Rise
Format
application/pdf
Genre/Form
masters theses
Language
English
Rights
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.
Recommended Citation
Lemke, Melody S., "Ecology and symbiosis of Branchipolynoe symmytilida and Bathymodiolus thermophilus at East Pacific Rise hydrothermal vents" (2025). WWU Graduate School Collection. 1439.
https://cedar.wwu.edu/wwuet/1439