193
4 Future Directions
Cavefi shes have evolved an integrated suite of behavioral, morphological, and physiological adaptations to cope with the abiotic and biotic challenges associated with
subterranean habitats. The close similarity of phenotypes among diverse fi sh taxa
around the world suggests that cave adaptation may be a general process resulting
from similar selective pressures. Some of the more notable adaptations include the
degeneration of eyes, reduction in pigmentation, enhancement of mechanoreception, lower metabolism, and increased longevity. However, our understanding of
sensory biology, including hearing, and ecology of cavefi shes is largely limited to
just a handful of species, particularly the characid Astyanax and amblyopsid cavefi shes. While these groups have been invaluable models in the study of hearing in
cavefi shes, several important questions remain. For example, have different cavefi sh
lineages evolved similar if not the same adaptive strategies to hearing specialization
or regression? Hearing ability has only been examined in four of the over 170 cave
obligate fi shes known globally. Two species show no differences in hearing ability
relative to their surface relatives, while the other two species exhibit regression.
Another important question is whether any cavefi shes exploit acoustic communication, which plays an important role in agonistic and mating behaviors in many
fi shes. Acoustic communication may be important in the darkness of caves in some
species, but the only study to examine acoustic communication in cave taxa found
no evidence for the production of species-specifi c sounds in lab-reared cave- or
surface-dwelling molly Poecilia mexicana (Schulz-Mirbach et al. 2010 ). The
authors hypothesized that the enhancement of the cephalic lateral line system may
compensate for the lack of visual communication in caves, but noted that cavefi sh
might produce sounds in their natural habitats. Evidence for acoustic communication in cavefi shes remains to be found.
Acknowledgements Apart from their enduring contributions to the fi eld of fi sh sensory biology
through published works, extensive reviews, and symposium organization, Drs. Popper and Fay
have also had an enduring personal contribution to the careers of most of the researchers in the fi eld
of fi sh acoustic. DH entered the Popper lab as a postdoctoral fellow, despite knowing little about
hearing and less about neurophysiology, and was immediately taken under Art’s tutelage. Art not
only offered invaluable training in the discipline but also served as a true mentor to DH in all
aspects of scientifi c citizenship and mentoring. DH also owes a tremendous debt to Fay for
patiently explaining the most basic principles of neurophysiology as well as being a constantly
positive source of review and encouragement in this fi eld. DS is also grateful for the mentoring and
support received by Popper throughout the years. Although she was not in the Popper lab, she
benefi ted from “hanging around” during her graduate years.
References
Culver DC (1976) The evolution of aquatic cave communities. Am Nat 110:945–957
Culver DC (1982) Cave life: evolution and ecology. Harvard University Press, Cambridge, MA
Culver DC, Pipan T (2009) The biology of caves and other subterranean habitats. Oxford University
Press, New York
Hearing in Cavefi shes
4 Future Directions
Cavefi shes have evolved an integrated suite of behavioral, morphological, and physiological adaptations to cope with the abiotic and biotic challenges associated with
subterranean habitats. The close similarity of phenotypes among diverse fi sh taxa
around the world suggests that cave adaptation may be a general process resulting
from similar selective pressures. Some of the more notable adaptations include the
degeneration of eyes, reduction in pigmentation, enhancement of mechanoreception, lower metabolism, and increased longevity. However, our understanding of
sensory biology, including hearing, and ecology of cavefi shes is largely limited to
just a handful of species, particularly the characid Astyanax and amblyopsid cavefi shes. While these groups have been invaluable models in the study of hearing in
cavefi shes, several important questions remain. For example, have different cavefi sh
lineages evolved similar if not the same adaptive strategies to hearing specialization
or regression? Hearing ability has only been examined in four of the over 170 cave
obligate fi shes known globally. Two species show no differences in hearing ability
relative to their surface relatives, while the other two species exhibit regression.
Another important question is whether any cavefi shes exploit acoustic communication, which plays an important role in agonistic and mating behaviors in many
fi shes. Acoustic communication may be important in the darkness of caves in some
species, but the only study to examine acoustic communication in cave taxa found
no evidence for the production of species-specifi c sounds in lab-reared cave- or
surface-dwelling molly Poecilia mexicana (Schulz-Mirbach et al. 2010 ). The
authors hypothesized that the enhancement of the cephalic lateral line system may
compensate for the lack of visual communication in caves, but noted that cavefi sh
might produce sounds in their natural habitats. Evidence for acoustic communication in cavefi shes remains to be found.
Acknowledgements Apart from their enduring contributions to the fi eld of fi sh sensory biology
through published works, extensive reviews, and symposium organization, Drs. Popper and Fay
have also had an enduring personal contribution to the careers of most of the researchers in the fi eld
of fi sh acoustic. DH entered the Popper lab as a postdoctoral fellow, despite knowing little about
hearing and less about neurophysiology, and was immediately taken under Art’s tutelage. Art not
only offered invaluable training in the discipline but also served as a true mentor to DH in all
aspects of scientifi c citizenship and mentoring. DH also owes a tremendous debt to Fay for
patiently explaining the most basic principles of neurophysiology as well as being a constantly
positive source of review and encouragement in this fi eld. DS is also grateful for the mentoring and
support received by Popper throughout the years. Although she was not in the Popper lab, she
benefi ted from “hanging around” during her graduate years.
References
Culver DC (1976) The evolution of aquatic cave communities. Am Nat 110:945–957
Culver DC (1982) Cave life: evolution and ecology. Harvard University Press, Cambridge, MA
Culver DC, Pipan T (2009) The biology of caves and other subterranean habitats. Oxford University
Press, New York
Hearing in Cavefi shes