In the Classroom
How do fish in the Southern Ocean keep from freezing?

Participants

William Detrich, Chief Scientist

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Photo of Bill DetrichI am Professor of Biochemistry and Marine Biology at Northeastern University in Boston, Massachusetts, and Chief Scientist for the ICEFISH cruise. Thank you for visiting the ICEFISH 2004 Cruise web site. I'd like to tell you about the goals of the cruise in general terms. Please visit the research descriptions of the cruise participants to find out the details of their individual projects. For more information on my research program at Northeastern University, which focuses on discovery of genes required for development of red blood cells using the hemoglobinless Antarctic icefishes as a model, please visit the following URL: www.northeastern.edu/biology/people/faculty/h-william-detrich-iii/

The ancestral fish stock (suborder Notothenioidei) of Antarctica probably arose as a sluggish, bottom-dwelling perch-like species some 40-60 million years ago in the then temperate shelf waters of the Antarctic continent. The subsequent development and grounding of the ice sheet on the continental shelf and changing food conditions eliminated the diverse fish fauna and initiated the original diversification of the notothenioids. On the High Antarctic shelf, notothenioids today dominate the fish fauna in terms of species diversity, abundance and biomass, the latter two at levels of 90-95%.

Since the International Geophysical Year of 1957-58, fish biologists from the Antarctic Treaty nations have made impressive progress in understanding the notothenioid fishes of the cold Antarctic marine ecosystem (often referred to as the High-Antarctic because the Southern Ocean is generally considered to begin at 60 degrees South latitude). However, integration of this work into the broader marine context has been limited, largely due to lack of access to, and analysis of, specimens of Sub-Antarctic notothenioid fishes (i.e., those found north of 60 degrees South). Sub-Antarctic fishes of the notothenioid suborder are critical for a complete understanding of the evolution, population dynamics, eco-physiology, and eco-biochemistry of their Antarctic relatives.

Recognizing the need to fill this gap, I began planning for the ICEFISH Cruise eight years ago. With the help of the cruise participants and many others, I submitted a proposal to the National Science Foundation for this research program in 2001, and the NSF funded the program in 2002. We have been planning the logistics of the cruise with the NSF and Raytheon Polar Services Company since then. Now we are embarking on the cruise!

The ICEFISH 2003 cruise has been conceived as an International Collaborative Expedition to collect and study Fish Indigenous to Sub-antarctic Habitats. The specific aims of the proposal are:

  1. Systematics and Evolutionary Studies. Sub-Antarctic and South Temperate Zone notothenioids have been understudied compared with the High-Antarctic species. There is a pressing need to expand our knowledge of the morphology, physiology, and biochemistry of the basal, non-Antarctic notothenioids. With this data in hand, we will be able to evaluate more rigorously numerous questions regarding the origin of the High Antarctic notothenioids. Are the Aadaptations@ described in Antarctic notothenioids truly advantageous, or are they simply traits that have persisted in this group? Are notothenioids an example of an adaptive radiation, a species flock or both? These and related questions will be addressed using both morphological and molecular approaches.
  2. Life History Strategies and Population Dynamics. Our limited understanding of the notothenioids is particularly acute in the ecological realm. The necessity to study large numbers of species, and many individuals per species, throughout a geographically dispersed ecosystem has certainly been an impediment to development of an ecological Weltanschauung (world view) of this group. The ICEFISH 2004 cruise will contribute to remedying this lack of understanding, in particular by linking the understudied Sub-Antarctic ecosystem to the better studied High Antarctic. Furthermore, analysis of the length of larval life and the extent of secondary pelagicism of the larval stages of Sub-Antarctic species will enhance the understanding of recruitment to adult populations and the evolution of these characters in High Antarctic species.
  3. Physiological, Biochemical, and Molecular Biological Investigations of Major Organ and Tissue Systems. Many unusual characters of High Antarctic fishes have been described as Aadaptations@ to their chronically cold environment. Are these characters truly adaptive or merely phyletically persistent traits? This question will be addressed by comparing the regulation of cardiovascular tone and the control of globin and myoglobin gene expression from Sub- and High-Antarctic fishes.
  4. Genomic Resources for the Sub-Antarctic Notothenioids. Nucleic acids (DNA and RNA) from representative Sub-Antarctic notothenioids will be collected and archived for future comparative studies of the genomes of important high- and low-latitude species. Some of the species that we collect may be previously unknown to science, in which case we will be able to provide first descriptions at both the morphological and molecular levels. The Detrich laboratory will create libraries of these nucleic acids for future dissemination to the biological community.
  5. Ecological Studies of Transitional Benthic Invertebrates. As for the notothenioid fishes, the benthic invertebrates if the Sub-Antarctic and South Temperate Zone have been understudied when compared with High-Antarctic species. Benthic invertebrates will be a significant component of the organisms collected by bottom trawling. Our team of invertebrate biologists will study these organisms to address questions comparable to those of the fish investigations.

In a world that is experiencing changes in global climate, the loss of biological diversity, and the depletion of marine fisheries, the Antarctic, Sub-Antarctic, and their biota offer compelling natural laboratories for understanding the evolutionary impacts of these processes. The proposed work will contribute to development of a baseline understanding of these sensitive ecosystems, one against which future changes in species distribution and survival may be evaluated judiciously.