365
fi shes and not actinistians represent the sister group to the tetrapods (Betancur-R.
et al. 2013 ; Broughton et al. 2013 ).
The African lungfi sh Protopterus annectens was shown to detect both particle
motion and pressure at frequencies ranging from 80 up to 640 Hz (Christensen et al.
2015 ). The air-fi lled lungs in these fi sh seem to function as pressure-to-particle
motion transducer, though the lungs are not directly linked to the inner ears
(Christensen et al. 2015 ). This recent study used a standing wave tube setup to disentangle the particle and pressure component of underwater sound which enabled
the authors to revise the outcomes of an earlier study which had indicated a lack of
sound pressure detection in lungfi sh (Christensen-Dalsgaard et al. 2011 ). Moreover,
Christensen et al. ( 2015 ) demonstrated that lungfi sh are also sensitive to airborne
sound which these fi sh detect via sound induced vibrations of the head.
2.2 Non-teleost Actinopterygii (Cladistia, Chondrostei,
Holostei)
In all studied non-teleost actinopterygians, the saccule and lagena form one sac. The
macula sacculi and the macula lagenae are, however, separated. The bowfi n Amia ,
the gar Lepisosteus and sturgeon Acipenser possess otoliths and otoconia that overlie the maculae of the end organs (Popper and Northcutt 1983 ; Mathiesen and
Popper 1987 ; Lychakov 1995 ).
In contrast to teleosts, these fi shes show considerable diversity of the macula
lagenae, mainly with regard to its overall shape (Popper 1978 ; Popper and Northcutt
1983 ; Mathiesen and Popper 1987 ; Lovell et al. 2005b ) (Fig. 3 ). The macula lagenae is almost as large as or even larger than the macula sacculi (except in Amia ),
which contrasts the condition found in many teleost species (Platt and Popper
1981a ; Ladich and Popper 2004 ). The two main orientation groups on the macula
lagenae are similar to those seen in teleosts with the exceptions of Amia , which
exhibits a striola-like region that resembles that of utricular maculae (Popper and
Northcutt 1983 ), and Lepisosteus osseus displaying a tripartite orientation pattern
(Mathiesen and Popper 1987 ). Three orientation groups are also present in some
teleosts such as the elopomorph Anguilla anguilla (Mathiesen 1984 ) or the chaetodontid Chaetodon miliaris (Popper 1977 ); but in these teleosts the third orientation group is restricted to a very narrow band at the posterior margin of the macula
lagenae (Mathiesen and Popper 1987 ).
The macula sacculi is hook-shaped ( Polypterus bichir ) (Fig. 3a ) or has a hookshaped anterior part (Fig. 3b–e ). In the anterior portion, ciliary bundle orientation
follows the curvature of the closest macula margin, creating horizontal groups. In
Amia , the anterior portion of the macula sacculi has a distinct 3D curvature bringing
the ciliary bundles in a new spatial orientation (Popper and Northcutt 1983 ). The
macula utriculi has the typical bowl-shape and orientation pattern described in
many vertebrates. The studied chondrostean species lack a lacinia, and in Acipenser
the macula is half-moon shaped (Popper 1978 ; Popper and Northcutt 1983 ;
Mathiesen and Popper 1987 ; Lovell et al. 2005b ).
Diversity of Inner Ears in Fishes: Possible Contribution Towards Hearing…
fi shes and not actinistians represent the sister group to the tetrapods (Betancur-R.
et al. 2013 ; Broughton et al. 2013 ).
The African lungfi sh Protopterus annectens was shown to detect both particle
motion and pressure at frequencies ranging from 80 up to 640 Hz (Christensen et al.
2015 ). The air-fi lled lungs in these fi sh seem to function as pressure-to-particle
motion transducer, though the lungs are not directly linked to the inner ears
(Christensen et al. 2015 ). This recent study used a standing wave tube setup to disentangle the particle and pressure component of underwater sound which enabled
the authors to revise the outcomes of an earlier study which had indicated a lack of
sound pressure detection in lungfi sh (Christensen-Dalsgaard et al. 2011 ). Moreover,
Christensen et al. ( 2015 ) demonstrated that lungfi sh are also sensitive to airborne
sound which these fi sh detect via sound induced vibrations of the head.
2.2 Non-teleost Actinopterygii (Cladistia, Chondrostei,
Holostei)
In all studied non-teleost actinopterygians, the saccule and lagena form one sac. The
macula sacculi and the macula lagenae are, however, separated. The bowfi n Amia ,
the gar Lepisosteus and sturgeon Acipenser possess otoliths and otoconia that overlie the maculae of the end organs (Popper and Northcutt 1983 ; Mathiesen and
Popper 1987 ; Lychakov 1995 ).
In contrast to teleosts, these fi shes show considerable diversity of the macula
lagenae, mainly with regard to its overall shape (Popper 1978 ; Popper and Northcutt
1983 ; Mathiesen and Popper 1987 ; Lovell et al. 2005b ) (Fig. 3 ). The macula lagenae is almost as large as or even larger than the macula sacculi (except in Amia ),
which contrasts the condition found in many teleost species (Platt and Popper
1981a ; Ladich and Popper 2004 ). The two main orientation groups on the macula
lagenae are similar to those seen in teleosts with the exceptions of Amia , which
exhibits a striola-like region that resembles that of utricular maculae (Popper and
Northcutt 1983 ), and Lepisosteus osseus displaying a tripartite orientation pattern
(Mathiesen and Popper 1987 ). Three orientation groups are also present in some
teleosts such as the elopomorph Anguilla anguilla (Mathiesen 1984 ) or the chaetodontid Chaetodon miliaris (Popper 1977 ); but in these teleosts the third orientation group is restricted to a very narrow band at the posterior margin of the macula
lagenae (Mathiesen and Popper 1987 ).
The macula sacculi is hook-shaped ( Polypterus bichir ) (Fig. 3a ) or has a hookshaped anterior part (Fig. 3b–e ). In the anterior portion, ciliary bundle orientation
follows the curvature of the closest macula margin, creating horizontal groups. In
Amia , the anterior portion of the macula sacculi has a distinct 3D curvature bringing
the ciliary bundles in a new spatial orientation (Popper and Northcutt 1983 ). The
macula utriculi has the typical bowl-shape and orientation pattern described in
many vertebrates. The studied chondrostean species lack a lacinia, and in Acipenser
the macula is half-moon shaped (Popper 1978 ; Popper and Northcutt 1983 ;
Mathiesen and Popper 1987 ; Lovell et al. 2005b ).
Diversity of Inner Ears in Fishes: Possible Contribution Towards Hearing…