May 2001-October 2002
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Recent studies of fish red blood cells found that a regular paracrystalline array of hemoglobin (Hb) tetamers formed under low oxygen conditions in 2 species of boreal fishes, Atlantic cod (Gadus morhua) and toadfish, (Opsanus tau). This phenomenon is termed hemoglobin gelation and its physiological characteristics and importance to survival of boreal fishes is unknown. The study outlined in this proposal will obtain preliminary data on the frequency and physiological nature of the phenomenon of hemoglobin (Hb) gelation in red blood cells of fishes that inhabit cold-water temperate and Arctic environments. The present study will test the hypothesis that hemoglobin gelation within fish red blood cells may be a feature of normal fish respiratory physiology and might be adaptive in extreme cold-water environments. Twelve fish species have been examined to date, and only the cold-water boreal marine fishes exhibited Hb gelation. In one species, Atlantic cod, gelation was relatively mild and did not result in changes in the gross morphology of the blood cells. In a second species, toadfish, gelation resulted in large crystalline structures that disrupted the red cell membranes and ruptured blood cells. The differences in type and severity of Hb gelation among fish species may directly affect their physiology and ultimately play an important part in their capacity for survival. However, too few species have been assayed to determine the extent of hemoglobin gelation in boreal fishes and no data exists on the physiological conditions that facilitate gelation. Few experimental links have been established between gelation and fish hemoglobin structure or between the variation in hemoglobin type and physiology.
In this study blood will be sampled from a large number of boreal and Arctic fishes and tested for Hb gelation and the presence of the Hb paracrystalline matrix. These data will provide an accurate assessment of the distribution of the gelation phenomenon within boreal fishes and any correlation with genetic variation within species. Some species of fishes, such as Atlantic cod, have polymorphic hemoglobin in which multiple hemoglobin allotypes are expressed within the red blood cells of the same species. To determine if gelation is associated with hematocrit or with the physiological characteristics of the isoHb components of a species, blood from a representative boreal fish species, Atlantic cod, will be separated into its Hb components and each component will be characterized for oxygen binding functionality and its gelation capacity. The scientific relevance of this is to determine if there are common morphological and physiological traits among hemoglobins of boreal fishes that exhibit gelation and whether these traits are adaptive in extreme environments characteristic of polar regions.
Hunt Von Herbing, Ione, "Is Hemoglobin Gelation an Adaptation to the Cold in Boreal Fishes?" (2003). University of Maine Office of Research and Sponsored Programs: Grant Reports. 187.