Like a Fish Out of Water

“Like a fish out of water,” a saying meant to describe someone in a situation or position they are not comfortable in, highlights how fish are not comfortable on the land. But not all fish are “like a fish out of water” when they are on land, as is seen in season one, episode six of Blue Planet II. In the show, David Attenborough describes the Pacific Leaping Blenny (Alticus arnoldorum), a fish found on the island of Guam and other islands in the south pacific [3,2]. Found on or near the beach, blennies are known to spend a portion of their lives out of water. Many species of blennies exist, and Alticus arnoldorum is one species known to live the most out of water. Alticus feed, reproduce, and even defend their territory on land, seldom entering the water [1].  Blennies eat algae found on the intertidal rocks on which they spend most of their lives. They reside in small burrows found in these rocks, and emerge from their burrows to feed and mate [1]. To navigate these rocks, blennies move by launching themselves with their tails like a spring, jumping from surface to surface and sticking to the rock with the thick mucus covering their body [4]. This mucus, however, does much more than just help the blennies stick to rocks. The mucus that covers the blennies is what allows them to breath. Blennies do not have lungs like most land animals, and therefore they must have a mucous coating to keep water over their gills and skin to breath; If they dry out, they will suffocate (1). Alticus arnoldorum may have evolved to live on land, but evolution is not perfect; despite spending the majority of their time in an environment surrounded by air, they cannot breath any of it. If their mucosal covering was to dry up, they would literally be, as the saying goes, “a fish out of water.”

by Jared Wilber

Blue Planet II, season 1, episode 6, starting at 35:10

References

1. Hsieh S-TT. 2010. A locomotor innovation enables water-land transition in a marine fish. PLoS ONE 5(6): e11197.
2. Ord TJ, Hsieh ST. 2011. A highly social, land-dwelling fish defends territories in a constantly fluctuating environment. 117(10):918-927
3. Morgans, CL, Cooke, GM, & Ord, T J. 2014. How populations differentiate despite gene flow: sexual and natural selection drive phenotypic divergence within a land fish, the Pacific leaping blenny. BMC evolutionary biology, 14, 97.
4. Gibb, AC, Ashley-Ross, MA, & Hsieh, ST. 2013. Thrash, flip, or jump: the behavioral and functional continuum of terrestrial locomotion in teleost fishes. Integrative and Comparative Biology, 53(2), 295-306.

 

 

 

 

References:

1. Hsieh S-TT. 2010. A locomotor innovation enables water-land transition in a marine fish. PLoS ONE 5(6): e11197.
2. Ord TJ, Hsieh ST. 2011. A highly social, land-dwelling fish defends territories in a constantly fluctuating environment. 117(10):918-927
3. Morgans, CL, Cooke, GM, & Ord, T J. 2014. How populations differentiate despite gene flow: sexual and natural selection drive phenotypic divergence within a land fish, the Pacific leaping blenny. BMC evolutionary biology, 14, 97.

Gibb, AC, Ashley-Ross, MA, & Hsieh, ST. 2013. Thrash, flip, or jump: the behavioral and functional continuum of terrestrial locomotion in teleost fishes. Integrative and Comparative Biology, 53(2), 295-306.