Meeting Abstract
Crustacean muscle fibers are some of the largest cells in the animal kingdom, with fiber diameters in the giant acorn barnacle (Balanus nubilus) exceeding 2 mm. Sessile animals with extreme muscle sizes and which live in the intertidal zone – like B. nubilus – represent ideal models for probing the effects of oxygen limitation on muscle cells. We aimed to investigate the metabolic response of B. nubilus muscle to fluctuating oxygen conditions over both acute (6h) and chronic (2 week) time periods. We exposed barnacles (n=9) to either: normoxic immersion, aerial emersion, or anoxic immersion. After a 6-hour exposure, tergal depressor (TD; fast twitch, glycolytic) and scutal adductor (SA; slow-twitch, oxidative) muscles were excised, flash frozen and processed for citrate synthase (CS) activity and lactate dehydrogenase (LDH) activity. CS activity did not show any significant treatment effect in either muscle; whereas LDH activity in the TD muscle was significantly higher in the animals exposed to the air. Furthermore, we uncovered a strong tissue effect, whereby SA muscle had significantly higher CS activity, and TD muscle had significantly higher LDH activity. Thus far, our findings indicate that B. nubilus can metabolically support aerobic activity in these giant muscle cells over short-term, low oxygen bouts, but there is some upregulation of LDH activity during air exposure in the more glycolytic TD muscle, presumably to support an increased reliance on anaerobic metabolism. We aim to supplement these findings by comparing our acute data to the same measurements collected after a chronic exposure period. By examining the effects of environmental oxygen limitation on metabolic patterns in giant B. nubilus muscles, we hope to further unravel the fundamentals of cellular design.
