405
lateral line neuromasts (Nicolson et al. 1998 ; Trapani and Nicolson 2011 ). For example, adult sputnik mutants exhibit circling behavior while swimming with forward
somersaulting and random lateral looping and cosmonaut zebrafi sh spin in a pinwheel fashion around their head as an axis. Sputnik also lacks a startle response and
has altered and non-functional stereociliary bundles in the crista of the semicircular
canals (Nicolson et al. 1998 ). As different zebrafi sh vestibular mutants exhibit different defi cits correlated with specifi c genes along the auditory- vestibular mechanoreception pathway, they are being used to understand the molecular basis of
auditory-vestibular signal transduction. For example, sputnik mutants have mutations in cadherin 23 (cdh23), an important protein found in hair cell stereocilia tip
links which are necessary for hair cell mechanotransduction (Söllner et al. 2004 ).
The lateral line system is implicated in a fi sh’s ability to swim in schools (Pitcher
et al. 1976 ), avoid predators (Blaxter and Fuiman 1989 ), orient in a current (Montgomery
et al. 1997 ), and localize prey (Coombs et al. 2001 ). Thus, any dysfunction in this system could have serious fi tness consequences. Differences in acoustically induced startle responses have been reported between wild and hatchery- reared fi shes (Smith and
Fuiman 2004 ). It is possible that behavioral defi cits in hatchery-reared fi shes are the
result of differences in their inner ear and lateral line system compared to wild-type
fi sh. For example, hatchery-reared juvenile steelhead ( Oncorhynchus mykiss ) exhibited smaller numbers of superfi cial neuromasts and greater numbers of abnormal otoliths compared to wild-collected individuals (Brown et al. 2013 ).
In order to better understand the role of the lateral line on fi sh behavior, experimenters have damaged the lateral line system and quantifi ed the resulting behavioral defi cits.
For example, Blaxter and Fuiman ( 1989 ) found a reduction in startle responses after
neuromast ablation in herring ( Clupea harengus ), cod ( Gadus morhua ), plaice
( Pleuronectes platessa ), fl ounder ( Platichthys fl esus ), and halibut ( Hippoglossus hippoglossus ) larvae. Similarly, Montgomery et al. ( 1997 ) reported a signifi cant reduction
in rheotactic response in torrentfi sh ( Cheimarrichthys fosteri ), bald notothen ( Pagothenia
borchgrevinki ), and blind cavefi sh ( Astyanax fasciatus ) following blockage or damage
to the lateral line system by ototoxic treatments, i.e., cobalt, streptomycin, or gentamicin, or physical ablation of the superfi cial neuromasts by gentle scraping.
While these studies suggest that the behavioral defi cits are the result of a loss of
lateral line neuromast function, there may be comorbid non-sensory physiological
effects from the pharmacological treatments that produce shifts in behavior (Janssen
2000 ). In fact, recent work using fl uorescent dye stains shows that streptomycin or
gentamicin treatments produce limited neuromast damage and suggests that even in
the absence of damage, pharmacologic agents might be able to modulate physiology
and produce behavioral defi cits (Brown et al. 2011 ).
6 Consequences of Anthropogenic Noise Exposure
As discussed previously, hearing and vestibular loss in fi shes can result from mutations, treatment with ototoxic chemicals, and exposure to acoustic trauma. Although
the effects of mutations and ototoxins on fi sh hearing loss are of considerable
Causes and Consequences of Sensory Hair Cell Damage and Recovery in Fishes
lateral line neuromasts (Nicolson et al. 1998 ; Trapani and Nicolson 2011 ). For example, adult sputnik mutants exhibit circling behavior while swimming with forward
somersaulting and random lateral looping and cosmonaut zebrafi sh spin in a pinwheel fashion around their head as an axis. Sputnik also lacks a startle response and
has altered and non-functional stereociliary bundles in the crista of the semicircular
canals (Nicolson et al. 1998 ). As different zebrafi sh vestibular mutants exhibit different defi cits correlated with specifi c genes along the auditory- vestibular mechanoreception pathway, they are being used to understand the molecular basis of
auditory-vestibular signal transduction. For example, sputnik mutants have mutations in cadherin 23 (cdh23), an important protein found in hair cell stereocilia tip
links which are necessary for hair cell mechanotransduction (Söllner et al. 2004 ).
The lateral line system is implicated in a fi sh’s ability to swim in schools (Pitcher
et al. 1976 ), avoid predators (Blaxter and Fuiman 1989 ), orient in a current (Montgomery
et al. 1997 ), and localize prey (Coombs et al. 2001 ). Thus, any dysfunction in this system could have serious fi tness consequences. Differences in acoustically induced startle responses have been reported between wild and hatchery- reared fi shes (Smith and
Fuiman 2004 ). It is possible that behavioral defi cits in hatchery-reared fi shes are the
result of differences in their inner ear and lateral line system compared to wild-type
fi sh. For example, hatchery-reared juvenile steelhead ( Oncorhynchus mykiss ) exhibited smaller numbers of superfi cial neuromasts and greater numbers of abnormal otoliths compared to wild-collected individuals (Brown et al. 2013 ).
In order to better understand the role of the lateral line on fi sh behavior, experimenters have damaged the lateral line system and quantifi ed the resulting behavioral defi cits.
For example, Blaxter and Fuiman ( 1989 ) found a reduction in startle responses after
neuromast ablation in herring ( Clupea harengus ), cod ( Gadus morhua ), plaice
( Pleuronectes platessa ), fl ounder ( Platichthys fl esus ), and halibut ( Hippoglossus hippoglossus ) larvae. Similarly, Montgomery et al. ( 1997 ) reported a signifi cant reduction
in rheotactic response in torrentfi sh ( Cheimarrichthys fosteri ), bald notothen ( Pagothenia
borchgrevinki ), and blind cavefi sh ( Astyanax fasciatus ) following blockage or damage
to the lateral line system by ototoxic treatments, i.e., cobalt, streptomycin, or gentamicin, or physical ablation of the superfi cial neuromasts by gentle scraping.
While these studies suggest that the behavioral defi cits are the result of a loss of
lateral line neuromast function, there may be comorbid non-sensory physiological
effects from the pharmacological treatments that produce shifts in behavior (Janssen
2000 ). In fact, recent work using fl uorescent dye stains shows that streptomycin or
gentamicin treatments produce limited neuromast damage and suggests that even in
the absence of damage, pharmacologic agents might be able to modulate physiology
and produce behavioral defi cits (Brown et al. 2011 ).
6 Consequences of Anthropogenic Noise Exposure
As discussed previously, hearing and vestibular loss in fi shes can result from mutations, treatment with ototoxic chemicals, and exposure to acoustic trauma. Although
the effects of mutations and ototoxins on fi sh hearing loss are of considerable
Causes and Consequences of Sensory Hair Cell Damage and Recovery in Fishes