113
3.2.5 Extra-oral and Extra-mandibular Teeth
Fish organs that are expressed out of place are rare, but possible, if we would like to
analyse, as example, the occurrence of dermal denticles outside the oral cavity in
some species of living teleost fi sh. According to Sire ( 2001 ): “ Not only have teeth
been expressed in extra-oral locations, but these new phenotypes have also been
maintained during subsequent evolution, suggesting that these denticles most likely
represent a selective advantage for their owners ,” (Sire 2001 ).
Therefore, the phenomenon of existence of extraoral denticles can be accepted as
important event with respect to their evolutionary, developmental, and functional
implications (Sire and Allizard 2001 ).
Here, I would like to cite the description represented by Jean-Yves Sire:
“ In Atherion elymus, the denticles are particularly numerous on the whole front
of the snout, the chin, and the undersides of the lower region of the head, where they
are aligned forming a denticulate keel [Fig. 3.11 ]. Like teeth located in the oral
Fig. 3.11 SEM imagery of the anterior region of the head of Atherion elymus ( a ) and detail of the
teeth, white arrow ( b ) and of the denticles on the chin, black arrowhead ( c ). Scale bars 100 µm
(Adapted from Sire ( 2001 ) with permission John Wiley and Sons. Copyright © 2001 BLACKWELL
SCIENCE, INC)
3.2 Teeth
3.2.5 Extra-oral and Extra-mandibular Teeth
Fish organs that are expressed out of place are rare, but possible, if we would like to
analyse, as example, the occurrence of dermal denticles outside the oral cavity in
some species of living teleost fi sh. According to Sire ( 2001 ): “ Not only have teeth
been expressed in extra-oral locations, but these new phenotypes have also been
maintained during subsequent evolution, suggesting that these denticles most likely
represent a selective advantage for their owners ,” (Sire 2001 ).
Therefore, the phenomenon of existence of extraoral denticles can be accepted as
important event with respect to their evolutionary, developmental, and functional
implications (Sire and Allizard 2001 ).
Here, I would like to cite the description represented by Jean-Yves Sire:
“ In Atherion elymus, the denticles are particularly numerous on the whole front
of the snout, the chin, and the undersides of the lower region of the head, where they
are aligned forming a denticulate keel [Fig. 3.11 ]. Like teeth located in the oral
Fig. 3.11 SEM imagery of the anterior region of the head of Atherion elymus ( a ) and detail of the
teeth, white arrow ( b ) and of the denticles on the chin, black arrowhead ( c ). Scale bars 100 µm
(Adapted from Sire ( 2001 ) with permission John Wiley and Sons. Copyright © 2001 BLACKWELL
SCIENCE, INC)
3.2 Teeth