Though it’s not active anymore, I hope you enjoy these old posts. But this blog was an fun hobby of mine for a few years a while back.
By day, I work at the intersections of science communication, nonprofit strategy, and creative design. Master of Science Thesis, University of British Columbia. Oblique swimming in characoid fishes with special reference to the genus Nannostomus Gunther 1872. Now back to this game - still tied 1-1 and heading into second overtime! One of the Penguins needs to do a nice head-fake and score…Īnd here is your Random Fish Video Set to Crazy Soundtracks - this one set to a particular vintage genre:Ĭlick for name etymology (ETYFish Project)Ĭlick for names in other languages (FishBase)Ĭhondoma, EC. The author postulated that this switch in posture between heads-up hovering and normal swimming results in a minor change in escape trajectory - a head-fake, to use ice hockey parlance - that allows penguin tetras a tiny, extra moment to flee a predator lunging from below (Chondoma 1979). Loss of the caudal fin additionally hampered the fish’s ability to maintain its preferred head-up posture, causing the body to tilt even further - leading the fish to swim more actively to maintain its posture (Chondoma 1979).īut why rest heads up? Penguin tetras prefer to hover and feed near the water surface - which can make them more vulnerable to predators stalking them from below - but they do revert to a more typical, non-tilted posture when swimming rapidly. Thayeria boehlkei was found to have a center-of-mass naturally behind its center-of-buoyancy, meaning that if the fish was motionless, it would float slightly head-up. The study involved some old-school methods, mainly removing caudal fins and pectoral fins and then seeing how the fish swam without one or the other, though the author did note that most fish regenerated the lost fins within weeks (“… except for the pectoral fin amputations in Nannostomus eques, which caused 100% mortality after about a week.”).
I found a masters thesis from 1979 where the author experimented with Thayeria boehlkei, Thayeria obliqua, and several other fish species to figure out how they maintain this unique posture. Thayeria boehlkei, the penguin fish, resting at a positive oblique angle.