28 March, 2011
Adaptations to Hypoxic and Anoxic Conditions by Carassius auratus
Heraclitus is known for saying, “Nothing endures but change.” Every biome and microhabitat on this planet currently exists in a condition that is delicate and ever-changing. If a population remains in a single niche from generation to generation, the members must change in response to environmental changes via mechanisms of heritable variation. This descent with modification has allowed populations to exist in environments for generations despite inevitable local and global changes. Adaptations can also assist a species in adjusting to a new environment after a migration event. One species which has thrived in man-made environments in particular is Carassius auratus, the common goldfish. This species, a member of the Cyprinidae family, has been selectively adapted by humans to thrive in many different habitats from back yard ponds to desktop fishbowls.
Carassius auratus is a robust minnow believed to be a native species from Asia in the rivers of China and Japan (Eschmeyer, 1990). Typically, these fish can be found in the wild in slow-moving streams and ponds. Goldfish thrive in ponds which support submerged vegetation (Robison and Buchanan, 1998). The goldfish has a strong fecundity rate as females may scatter up to 4000 adhesive eggs in a single spawning session over littoral debris and vegetation (Dobie et al 1956). Goldfish have been kept in captivity as pets for generations. Their domestication and selective breeding for unique characteristics has been so successful that many genetic tests have taken place to study comparative variation in wild and domesticated stocks (Beckwitt and Aoyagi, 1987).
Goldfish have inherited, and uniquely adapted, their own strategies to deal with acquiring oxygen in hypoxic conditions. A behavioral adaptation which arose independently in the Carassius auratus line is the practice of air gulping. Although goldfish have been...