It is as primitive as a cave man.
The sense of sight is considered to be the most important sense for human beings.
The most important adaptation of cave fish is their loss of eyesight, which is a response to the dark, subterranean environments they inhabit. This adaptation is complemented by enhanced non-visual senses, such as heightened olfaction and lateral line systems, allowing them to navigate and find food in complete darkness. This evolutionary change highlights the cave fish's ability to thrive in resource-scarce conditions while reducing energy expenditure on unnecessary features. Additionally, the loss of pigmentation, resulting in a pale, often translucent appearance, is another key adaptation to their environment.
The most important sense of owls is their sight. They depend on it to see the creatures that they hunt at night (rodents).
Cod Fish
feet
Eyes
The simple answer is the karst cave, formed in limestone, because those are the most numerous, varied, complexand extensive... but an individual researcher may be studying other types of cave such as lava tubes or mass-movement fissures. So for the individual speleologist the "most important" type is that which he or she is studying at the time.
Trees & fish.
Debatable, but possibly mouth, gills, and fins would be the most important, as without them the fish would be unable to eat, breathe, or move.
Not at most times, they would usually eat fish and rocks. alittle harsh right?
salmon