346
the otolithic end organs of teleosts with ancillary auditory structures often have
orientation patterns of the ciliary bundles that deviate from the patterns found in fi sh
lacking these structures (Platt and Popper 1981a ; Popper and Coombs 1982 ; Popper
and Schilt 2008 ; Popper and Fay 2011 ).
The following overview of inner ear diversity in the major groups of bony fi shes
follows the systematics presented by Betancur-R. et al. ( 2013 ), Broughton et al.
( 2013 ) and updated outcomes of the DeepFin project (Project 2003 –2009). The
main focus of the descriptions is on sensory epithelia, the presence of ancillary
auditory structures and hearing abilities (summarized in Table 2 ). Hard parts of the
inner ear, especially the otoliths in teleosts, also show considerable diversity. Otolith
mineralization is a separate, complex fi eld depending on a number of factors such
as endolymph chemistry and fi sh metabolism. As this is beyond the scope of our
review we will not discuss variation of otolith morphology in detail.
2.1 Sarcopterygii
In the coelacanth Latimeria (Actinistia), saccule and lagena are two interconnected
pouches (Fritzsch 1987 , 2003 ). A saccular otolith is reported, but no other otoliths
or otoconia were described (Carlström 1963 ; Millot and Anthony 1965 ; Bernstein
2003 ). In addition to the maculae of the end organs and the macula neglecta,
Latimeria possesses a (sensory) epithelium that has been hypothesized to be homologous to the tetrapod basilar papilla and thus indicating a close relationship to the
tetrapods (Fritzsch 1987 , 2003 ). The orientation pattern of the macula lagenae,
however, is similar to that in other bony fi shes, i.e. it consists of two opposing
groups of ciliary bundles and therefore differs from that found in amphibians, in
which the ciliary bundles point away from the dividing line (Platt 1994 ; Platt et al.
2004 ). This fi nding contradicts the assumption that one similarity between Latimeria
and tetrapods is expressed through a similar lagenar orientation pattern (Fritzsch
1987 ; Fritzsch et al. 2013 ). As no hearing data are available, one can only speculate
whether Latimeria is sound pressure sensitive and if its hearing abilities are comparable to terrestrial vertebrates.
In lungfi shes (Dipnomorpha), saccule and lagenae form a single pouch (Retzius
1881 ). Within this pouch, the macula sacculi and the macula lagenae represent a
continuum, a sacculolagenar macula in which two regions of high hair cell densities
(striolas) are separated by areas of lower densities of sensory hair cells (Platt et al.
2004 ). Such a sacculolagenar macula is unique among bony fi shes. The sacculolagenar macula is overlain by two “otoliths” apparently made up of numerous single
otoconia rather than being massive biomineralisates (Gauldie et al. 1986a ; Platt
et al. 2004 ). In Protopterus a tetrapod-like feature was identifi ed for the crista of the
horizontal semicircular canal, which resembles a hemicrista (Platt et al. 2004 ).
Although inner ear diversity does not necessarily refl ect phylogenetic relationships,
this similarity is in accordance with recent molecular analyses indicating that lungT. Schulz-Mirbach and F. Ladich
the otolithic end organs of teleosts with ancillary auditory structures often have
orientation patterns of the ciliary bundles that deviate from the patterns found in fi sh
lacking these structures (Platt and Popper 1981a ; Popper and Coombs 1982 ; Popper
and Schilt 2008 ; Popper and Fay 2011 ).
The following overview of inner ear diversity in the major groups of bony fi shes
follows the systematics presented by Betancur-R. et al. ( 2013 ), Broughton et al.
( 2013 ) and updated outcomes of the DeepFin project (Project 2003 –2009). The
main focus of the descriptions is on sensory epithelia, the presence of ancillary
auditory structures and hearing abilities (summarized in Table 2 ). Hard parts of the
inner ear, especially the otoliths in teleosts, also show considerable diversity. Otolith
mineralization is a separate, complex fi eld depending on a number of factors such
as endolymph chemistry and fi sh metabolism. As this is beyond the scope of our
review we will not discuss variation of otolith morphology in detail.
2.1 Sarcopterygii
In the coelacanth Latimeria (Actinistia), saccule and lagena are two interconnected
pouches (Fritzsch 1987 , 2003 ). A saccular otolith is reported, but no other otoliths
or otoconia were described (Carlström 1963 ; Millot and Anthony 1965 ; Bernstein
2003 ). In addition to the maculae of the end organs and the macula neglecta,
Latimeria possesses a (sensory) epithelium that has been hypothesized to be homologous to the tetrapod basilar papilla and thus indicating a close relationship to the
tetrapods (Fritzsch 1987 , 2003 ). The orientation pattern of the macula lagenae,
however, is similar to that in other bony fi shes, i.e. it consists of two opposing
groups of ciliary bundles and therefore differs from that found in amphibians, in
which the ciliary bundles point away from the dividing line (Platt 1994 ; Platt et al.
2004 ). This fi nding contradicts the assumption that one similarity between Latimeria
and tetrapods is expressed through a similar lagenar orientation pattern (Fritzsch
1987 ; Fritzsch et al. 2013 ). As no hearing data are available, one can only speculate
whether Latimeria is sound pressure sensitive and if its hearing abilities are comparable to terrestrial vertebrates.
In lungfi shes (Dipnomorpha), saccule and lagenae form a single pouch (Retzius
1881 ). Within this pouch, the macula sacculi and the macula lagenae represent a
continuum, a sacculolagenar macula in which two regions of high hair cell densities
(striolas) are separated by areas of lower densities of sensory hair cells (Platt et al.
2004 ). Such a sacculolagenar macula is unique among bony fi shes. The sacculolagenar macula is overlain by two “otoliths” apparently made up of numerous single
otoconia rather than being massive biomineralisates (Gauldie et al. 1986a ; Platt
et al. 2004 ). In Protopterus a tetrapod-like feature was identifi ed for the crista of the
horizontal semicircular canal, which resembles a hemicrista (Platt et al. 2004 ).
Although inner ear diversity does not necessarily refl ect phylogenetic relationships,
this similarity is in accordance with recent molecular analyses indicating that lungT. Schulz-Mirbach and F. Ladich