Heat flow is measurable from Artemia franciscana embryos under anoxia

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A recent report has concluded that heat flow under anoxia from encysted embryos of the brine shrimp Artemia is unmeasurable (Hontoria et al. [1993] J. Exp. Biol., 178:149–159). This observation contrasts with two earlier communications that have reported low but measurable energy flow from these gastrulae (Hand and Gnaiger [1988] Science, 239:1425–1427; Hand [1990] J. Comp. Physiol. [B], 160:357–363). In order to re‐examine this issue, up to 20 g wet mass of embryos was loaded per experiment into sealed ampoules (25‐ to 50‐fold more tissue than in previous studies) and calorimetric analyses were conducted. Even after 50–60 h, a clearly measurable heat dissipation was recorded from these anoxic embryos (0.0128 ± 0.0007 mW·g dry mass−1; ± 1 SE, n =6). The results confirm the presence of measurable heat flow under anoxia. The rate of heat dissipation measured in this study is at the limit of detection for the instrument used by Hontoria et al. ([1993] J. Exp. Biol., 178:149–159). A second important issue is whether any of the low heat flow under anoxia is associated with processes involving ATP turnover, a point that is evaluated in this study but that remains unresolved. However, calculations suggest that macromolecular degradation may explain a significant portion of the anoxic heat flow. © 1995 Wiley‐Liss, Inc. Copyright © 1995 Wiley‐Liss, Inc., A Wiley Company

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Journal of Experimental Zoology

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