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Protein synthesis, RNA concentrations, nitrogen excretion, and metabolism vary seasonally in the Antarctic holothurian Heterocucumis steineni (Ludwig, 1898)

Fraser, Keiron P.P.; Peck, Lloyd S.; Clarke, Andrew. 2004 Protein synthesis, RNA concentrations, nitrogen excretion, and metabolism vary seasonally in the Antarctic holothurian Heterocucumis steineni (Ludwig, 1898). Physiological and Biochemical Zoology, 77 (4). 556-569. 10.1086/420949

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Abstract/Summary

Seasonal changes in protein and nitrogen metabolism have not previously been reported in any Antarctic suspension-feeding species that ceases feeding for extended periods in winter. To provide comparison with data reported on Nacella concinna, a species that continues to feed in winter, we have measured feeding activity; oxygen consumption; ammonia, urea, and fluorescamine-positive substance (FPS) excretion; O:N ratios; body wall protein synthesis; RNA to protein ratios; and RNA activity at three times during the year in an Antarctic suspension-feeding holothurian. Feeding activity ceased for 4 mo during winter, and oxygen consumption rates decreased from 8.79+/-0.43 mumol h(-1) to 4.48+/-0.34 mumol h(-1). Ammonia excretion also decreased during winter from 2,600+/-177 nmol N h(-1) to 974+/-70 nmol N h(-1), but urea excretion rates increased from 178+/-36 nmol N h(-1) to 281+/-110 nmol N h(-1), while FPS excretion rates remained unchanged throughout the year with a seasonal mean of 88+/-13 nmol N h(-1). Oxygen to nitrogen ratios ranged between 6 and 10, suggesting that proteins were used as the primary metabolic substrate. Body wall protein synthesis rates decreased from 0.35%+/-0.03% d(-1) in summer to 0.23% d(-1) in winter, while RNA to protein ratios decreased from 33.10+/-1.0 mug RNA mg(-1) protein in summer to 27.88+/-1.3 mug RNA mg(-1) protein in winter, and RNA activity was very low, ranging between 0.11+/-0.01 mg protein mg(-1) RNA d(-1) in summer and 0.06+/-0.01 mg protein mg(-1) RNA d(-1) in winter. Heterocucumis steineni shows a larger seasonal decrease in oxygen consumption and ammonia excretion between February (summer) and July (winter) than N. concinna, while the proportional decrease in protein synthesis rates is similar in both species.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1086/420949
Programmes: BAS Programmes > Antarctic Science in the Global Context (2000-2005) > Life at the Edge - Stresses and Thresholds
ISSN: 1522-2152
NORA Subject Terms: Marine Sciences
Biology and Microbiology
Ecology and Environment
Date made live: 17 Jan 2012 10:24
URI: http://nora.nerc.ac.uk/id/eprint/12165

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