Effect of Oxygen-Limiting Tidal Conditions on Muscle Metabolism and Structure in the Giant Acorn Barnacle, Balanus nubilus

<p>Crustacean muscle fibers are some of the largest cells in the animal kingdom, with fiber diameters in the giant acorn barnacle (<em>Balanus nubilus</em>) exceeding 3 mm. Sessile animals with extreme muscle sizes and that live in the hypoxia-inducing intertidal zone – like <em>B. nubilus</em> – represent ideal models for probing the effects of oxygen limitation on muscle cells. We investigated changes in metabolism and structure of <em>B. nubilus</em> muscle in response to: normoxic immersion, anoxic immersion, or air emersion, for acute (6h) or chronic (6h exposures twice daily for 2wks) time periods. Following exposure, we immediately measured hemolymph pO₂, pCO₂, pH, Na⁺, Cl^-, K⁺, and Ca⁺then excised tergal depressor (TD) and scutal adductor (SA) muscles to determine citrate synthase (CS) activity, lactate dehydrogenase (LDH) activity, and D-lactate levels. We also prepared a subset of SA and TD muscles from the chronic barnacles for histological analysis of fiber diameter (Feret’s), cross-sectional area (CSA), mitochondrial distribution and relative density, as well as nuclear distribution and myonuclear domain size. There was a significant decrease in hemolymph pO₂ and pCO₂ following acute and chronic anoxic immersion, whereas air emersion pO₂ and pCO₂ was comparable to normoxic levels. Fiber CSA and diameter did not change significantly in either tissue, while myonuclear domain size in SA muscle was significantly lower in the anoxic and emersion groups than the normoxic control. Neither CS, nor LDH activity, showed any significant treatment effect in either tissue, whereas both muscles had significantly higher D-lactate levels after air emersion following acute (though not chronic) exposure. Thus far, our findings indicate that <em>B. nubilus</em> experience a general reduction in aerobic metabolism under anoxia, emersion is only mildly oxygen-limiting, and that muscle plasticity is occurring during chronic emersion and anoxia.</p>

Name thesis:degree_name

MS in Biological Sciences

Discipline thesis:degree_discipline

Biological Sciences

Year dc:date.available

2016

Author dc:creator

• Grady, Katie O

Contributors dc:contributor

• Kristin Hardy

• Balanus nubilus
• giant barnacle
• anoxia
• hypoxia
• giant muscle cells
• intertidal
• metabolism
• muscle plasticity
• histology
• Behavior and Ethology
• Cell Biology
• Cellular and Molecular Physiology
• Comparative and Evolutionary Physiology
• Developmental Biology
• Integrative Biology
• Marine Biology

Identifier

10.15368/theses.2016.166

OAI identifier oai:identifier

oai:digitalcommons.calpoly.edu:theses-2893