Does a highly-sensitive auditory organ necessarily imply a behavioural response to sound?

Question

My question could be about any sensory modalities but it rose with the case of hearing in female mosquitoes. Females mosquitoes of most species does not behaviorally respond to sound stimuli (contrary to males), even if their organs are highly sensitive to sound stimuli in electrophysiology studies. They are only a few exceptions in females including frog-biting mosquitoes that are attracted to the playback of host calls (see this SE thread).

So there are two options to solve the paradox in mosquito female hearing: either we have not managed to induce the behavioural response to sound which electrophysiology response is associated, or they just don't use their high sound sensitivity organs. I'm interested in the latest hypothesis.

Do we know any examples of organisms that have a highly developed auditory organ and

1. don't use it for whatever (evolutionary?) reason?
2. or have been showed to use the sounds without direct behavioral changes at the moment of the sound exposure?

Answer 1

If there were no benefit to the fitness ( ... really the inclusive fitness) of the organism there would be no selection pressure against mutations that affect this organ except for those that reduce the cost to the organism of developing it (in the indvidual), so it would head for being vestigial and eventually lost.

As 'not used' is unprovable this theoretical assessment strongly suggests that it will be used, and the challenge is to find what that benefit may be, and it may not be via an instantaneous response. We see many examples of that in a primate H. sapiens....