title: First Description of a Palatal Organ in Chimaera monstrosa (Chondrichthyes, Holocephali).
abstract: Chimaeroid fishes are the only extant Holocephali, a subclass of Chondrichthyes. We describe for the first time a well evidenced structure localized in the palate of the chimaeroid Chimaera monstrosa, here named a palatal organ (PO). Attention has been paid to the holocephalan head morphology, but there has been no mention of this particular organ in the literature. The PO is a soft-tissue mass located within a slight hollow in between the two vomerine toothplates, and it protrudes into the oral cavity, resembling the mammalian incisive papilla. It is characterized by dense connective tissue with abundant collagen and elastic fibers and no muscular tissue. The robust innervation but low density of taste buds suggest a role in gustation for the PO, but primary utility in general mechanical sensitivity likely implicated in food sorting. The presence of numerous multicellular serous glands in the anterior/dorsal part of the PO is quite surprising because, in gnathostome fish, the presence of multicellular glands within the mouth has been reported in only the rare case of teeth-associated venom glands. Hypothesized roles for these glands could include food lubrication, digestion and defense against pathogens. In the literature, the presence of a PO has been demonstrated in many published images of chimaeroid fishes, but has gone unnoticed. This trait could represent a peculiar characteristic of all or a subset of holocephalans.
authors.affiliation: Department of Environmental, Earth and Life Science (DISTAV), University of Genoa, Genoa, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Ferrando
authors.affiliation: Department of Environmental, Earth and Life Science (DISTAV), University of Genoa, Genoa, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Gallus
authors.affiliation: Institute of Marine Sciences (ISMAR), National Research Council, Genoa, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Gambardella
authors.affiliation: Department of Environmental, Earth and Life Science (DISTAV), University of Genoa, Genoa, Italy.
authors.forename: Daniel
authors.initials: D
authors.lastname: Croce
authors.affiliation: Department of Environmental, Earth and Life Science (DISTAV), University of Genoa, Genoa, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Damiano
authors.affiliation: Department of Environmental, Earth and Life Science (DISTAV), University of Genoa, Genoa, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Mazzarino
authors.affiliation: Institute for Environmental Protection and Research (ISPRA) C/O Institute of Marine Sciences (ISMAR), National Research Council, Genoa, Italy.
authors.forename: Marino
authors.initials: M
authors.lastname: Vacchi
mesh_terms: D000818:Animals; D005399:Fishes / Q000033:anatomy & histology* / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D013650:Taste Buds / Q000033:anatomy & histology* / Q000502:physiology*; D014070:Tooth / Q000033:anatomy & histology / Q000502:physiology
keywords: Holocephalans; incisive papilla; mouth; palatal organ; rabbitfish