The Gondwanian heritage of Patagonian fishes: physiology and life history

V.E. CUSSAC

Bariloche

Simposio; Simposio: Physiological Adaptations in the Southern Hemisphere: are there convergences among Gondwanian Land Masses in cold-blooded vertebrates? VI Southern Connection Congress; 2010

South America has a distinctive trait amongst land masses of the Southern Hemisphere; its vast latitudinal range (from 12ºN to 56ºS). Since the opening of the Drake Passage during the Tertiary and the subsequent climate cooling, the original freshwater Gondwanian fish fauna underwent a gradient of selection pressures applied on thermal tolerance and capacity to endure winter starvation. Later, marine incursions and glaciations added major traits to this scenario and this ensemble of selection pressures acting on physiological and life history capabilities drove to the persistence of some groups of siluroids (Diplomystiidae, Trichomycteridae) and characins (Cheirodon, Gymnocharacinus) or to the replacement by a successful marine related fish fauna (Percichthyidae, Atherinopsidae, Galaxiidae). The adaptations displayed included tolerance to low temperature, low oxygen availability, darkness and abrasion, use of thermal habitats, bigger eggs, use of warmer breeding habitats, different breeding seasons, and migration within freshwater or between freshwater and the sea. Thus, present landscape shows the paradoxical situation of a severely impoverished fish fauna (only four native species in Tierra del Fuego Island) and a rich menu of ecological relationships, amongst species and between species and environment, mediated by eco-physiological and eco-morphological adaptations and life history adjustments.