From “Landlubber’ Fish Leap for Love When Tide Is Right: Research Sheds Light On How Animal Life First Evolved to Colonize Land” (ScienceDaily, Aug. 31, 2011), we learn: about the “leaping blenny,” a marine fish that spends almost all its time on land (yes) around intertidal pools. To breath through its gills and skin, it need only stay moist, not submerged.
“Our study showed that life on land for a marine fish is heavily dependent on tide and temperature fluctuations, so much so that almost all activity is restricted to a brief period at mid-tide, the timing of which changes daily. During our field study on Guam we never saw one voluntary return to water. Indeed, they spend much of their time actively avoiding submersion by incoming waves, even when we tried to capture them for study.
So they actually have an aversion to water – thus are free from any temptation to return to the sea. That last part is illuminating, because in a real-world account of evolution, one must address the fact that most marine creatures would probably just chuck the new, terrestrial way of life when difficulties arose, and return to the old one – to which they are well adapted.
“I can tell you they are very hard to catch and are extremely agile on land. They move quickly over complex rocky surfaces using a unique tail-twisting behaviour combined with expanded pectoral and tail fins that let them cling to almost any firm surface. To reach higher ground in a hurry, they can also twist their bodies and flick their tails to leap many times their own body length.”
Not only do they not like water, in other words, but they get on fine on land.
“The Pacific leaping blenny offers a unique opportunity to discover in a living animal how a water-land transition has taken place,” says Dr Ord.
”We know that our ancient ancestors evolved originally from lobe-finned fish but, today, all such fish are fully aquatic. Within the blenny family, however, are species that are either highly terrestrial, amphibious or entirely aquatic. Remarkably, representatives of all these types can be found on or around Guam, making it a unique evolutionary laboratory.”
Not really the answer to a transition to land. The conundrum for that transition involves the development of lungs, for example – which the blennie never did. As a result, the fish is committed to a tidal pools environment, and is not really a model for true terrestrial life.
The blennie demonstrates that it loves water as much as the average house cat does:
See also: Lobbing a grenade into the tetrapod evolution picture
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