Dolphins  

 Dolphins  (and other  odontocetes
 ) rely on  echolocation
 to aid in detecting,
identifying, localizing, and capturing prey. Dolphin sonar signals are well
suited for localizing multiple, small targets in a three-dimensional aquatic
environment by utilizing highly directional (3 dB beamwidth of about 10 deg),
broadband (3 dB bandwidth typically of about 40 kHz; peak frequencies between
40 kHz and 120 kHz), short duration clicks (about 40 μs). Dolphins can
localize sounds both passively and actively (echolocation) with a resolution
of about 1 deg. Cross-modal matching (between vision and echolocation)
suggests dolphins perceive the spatial structure of complex objects
interrogated through echolocation, a feat that likely requires spatially
resolving individual object features and integration into a holistic
representation of object shape. Although dolphins are sensitive to small,
binaural intensity and time differences, mounting evidence suggests dolphins
employ position-dependent spectral cues derived from well-developed head-
related transfer functions, for sound localization in both the horizontal and
vertical planes. A very small temporal integration time (264 μs) allows
localization of multiple targets at varying distances. Localization
adaptations include pronounced asymmetry of the skull, nasal sacks, and
specialized lipid structures in the forehead and jaws, as well as acoustically
isolated middle and inner ears.

**The role of Prestin in sound localization:**

In the realm of mammalian sound localization, the  Prestin  gene has emerged as a pivotal player, particularly in the
fascinating arena of  echolocation  employed by bats and dolphins. Discovered just over a decade
ago, Prestin encodes a protein located in the inner ear's hair cells,
facilitating rapid contractions and expansions. This intricate mechanism
operates akin to an antique phonograph horn, amplifying sound waves within the
cochlea and elevating the overall sensitivity of hearing.

In 2014 Liu and others delved into the evolutionary adaptations of  Prestin
 , unveiling its critical role in the ultrasonic
hearing range essential for animal sonar, specifically in the context of 
echolocation  . This
adaptation proves instrumental for dolphins navigating through turbid waters
and bats seeking sustenance in nocturnal darkness.  [32]

Noteworthy is the emission of high-frequency echolocation calls by toothed
whales and echolocating bats, showcasing diversity in shape, duration, and
amplitude. However, it is their high-frequency hearing that becomes paramount,
as it enables the reception and analysis of echoes bouncing off objects in
their environment. A meticulous dissection of Prestin protein function in
sonar-guided bats and bottlenose dolphins, juxtaposed with nonsonar mammals,
sheds light on the intricacies of this process.

Evolutionary analyses of Prestin protein sequences brought forth a compelling
observation – a singular  amino acid  shift
from threonine (Thr or T) in sonar mammals to asparagine (Asn or N) in
nonsonar mammals. This specific alteration, subject to parallel evolution,
emerges as a linchpin in the mammalian echolocation narrative.  [32]

Subsequent experiments lent credence to this hypothesis, identifying four key
 amino acid  distinctions in sonar mammals
that likely contribute to their distinctive echolocation features. The
confluence of evolutionary analyses and empirical findings provides robust
evidence, marking a significant juncture in comprehending the  Prestin
 gene's role in the evolutionary trajectory of
mammalian echolocation systems. This research underscores the adaptability and
evolutionary significance of Prestin, offering valuable insights into the
genetic foundations of sound localization in bats and dolphins, particularly
within the sophisticated realm of echolocation.  [32]