1. lifelines
  2. Eyeless Mexican cavefish lost metabolic circadian rhythm

Eyeless Mexican cavefish lost metabolic circadian rhythm

By dr. dolittle on September 25, 2014.
Image of eyeless Mexican tetra fish from www.seriouslyfish.com by H-J Chen. Image of eyeless Mexican tetra fish from www.seriouslyfish.com by H-J Chen.

The metabolism of most animals follows a circadian rhythm that differs between the day and night. Mexican cavefish living in constant darkness, lost this circadian rhythm some time ago. In a newly published study in PLOS ONE, researchers compared the metabolic rate of both cave- and surface-dwelling Mexican tetra fish (Astyanax mexicanus). They hypothesized that since the fish living in each location naturally experience differences in food, predation as well as exposure to daily light fluctuations, they might also have different metabolic needs. When they exposed surface-dwelling fish to constant darkness, the circadian rhythm in terms of metabolism was consistent with oxygen demands normally seen in the daytime resulting in the expenditure of 38% more energy than the cave-dwelling fish. In contrast, the eyeless cave-dwelling fish do not have a metabolic circadian rhythm which the researchers say conserves 27% of their energy in comparison to surface fish. In a quote published in Discovery News, lead study author Dr. Damian Moran said, "These cave fish are living in an environment without light, without the circadian presence of food or predators, they've got nothing to get ready for, so it looks like they've just chopped away this increase in anticipation for the day." The study authors suggest that conserving energy is important for life in a cave where food may be scarce.

Sources:
Moran D, Softley R, Warrant EJ. Eyeless Mexican Cavefish Save Energy by Eliminating the Circadian Rhythm in Metabolism. PLOS ONE. September 24, 2014. DOI: 10.1371/journal.pone.0107877

Discovery News

Tags
Life Science
cave
circadian
dark
energy
eye
fish
metabolism
Mexican

More like this

Do Mexican cavefish hold the secret to treating diabetes?
Image of cave dwelling Mexican tetra By Citron via Wikimedia Commons Mexican tetra (Astyanax mexicanus) are a fascinating example of divergent evolution. Over time, some of these freshwater river fish washed into caves where they continue to live. With perpetual darkness, these cavefish have…
Rainforest Glow-worms glow at night because their clock says so
Glow worms glimmer on cue: University of Queensland researcher and lecturer Dr David Merritt has discovered that Tasmanian cave glow-worms are energy conservationists: they switch their lights off at night-time. The discovery was made during a partially funded UQ Firstlink study, which revealed…
Hybrids of Blind Fish Can See
The loss of sight in cave dwelling species is widely known. We presume that since sight in utter darkness has no fitness value, the mutation of a gene critical to the development of the sense of sight is not selected against. Over time, any population living in darkness will eventually experience…
The Blind Leading the Blind
Image: Jesus! vs. Darwin! by The Searcher It's a tired old routine, yet time and again the same argument is taken off the shelf, dusted, buffed and then presented with a sly smile as if it were something new. Evolution, it's asserted, is only progressive and builds on earlier adaptations in its…