Metabolic energy utilization during development of Antarctic naked dragonfish (Gymnodraco acuticeps)
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We have capitalised on the availability of eggs and adults of the naked dragonfish Gymnodraco acuticeps (Sub-order Notothenioidei, F. Bathydraconidae) near McMurdo Station, Antarctica to examine metabolic energy utilization at different stages of its life cycle. Average egg respiration rates were found to increase from 2.17±1.02 nmol O2 h−1 ind−1 at about 17 h post-fertilization (hpf) to 5.72±0.56 nmol h−1 ind−1 at about 24 hpf, during which time the eggs underwent first cleavage. The respiration rates of embryos from 2–20 days post-fertilization (dpf) averaged 4.11±1.47 nmol O2 h−1 ind−1. About 10 months post-fertilization, oxygen consumption rates of 27.14±3.92 nmol O2 h−1 ind−1 were recorded immediately prior to hatching, with a peak of 112.41±31.38 nmol O2 h−1 ind−1 at the time of hatch. Larvae aged 46–63 days post-hatch had an average respiration rate of 64.4±15.11 nmol O2 h−1 ind−1. Mass-specific respiration rates of hatched larvae (approximately 1–2 months old) were calculated using dry weights (DW) and averaged 16.1±3.4 nmol O2 h−1 mg−1 DW. Adult dragonfish respiration rates (corrected for a 100 g fish and using a 0.8 scaling exponent) averaged 0.91±0.36 mmol O2 kg−1 h−1 after a 48 h acclimatization period, which is not indicative of significant metabolic cold adaptation. The energy contents of dragonfish eggs and larvae were also measured by microbomb calorimetry and used, along with the respiration data, in an initial approach to estimate an energy budget. In order to balance the budget, the bulk of the available post-gastrulation respiratory energy (during 213 days of embryonic incubation) must be consumed at a relatively low average rate (7.1 nmol O2 h−1 ind−1), which supports the possibility that advanced dragonfish embryos overwinter in a relatively quiescent metabolic state while awaiting a suitable stimulus (such as the return of the sun) to initiate hatching.
KeywordsRespiration Rate Oxygen Consumption Rate Atlantic Halibut Routine Metabolic Rate Average Respiration Rate
We thank Kevin Hoefling, Ben Hunt and Luke Hunt for their efforts in collecting eggs and adult fish by SCUBA at McMurdo Station, Antarctica, and Paul Ulrich and Allison Green for their assistance with some of the respiration equipment. This work was supported by: the National Science Foundation, Office of Polar Programs (#02-31006 to ALD and C-HCC; #02-38281 to AGM). CWE is grateful to the University of Auckland Research Committee for their continuing support.
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