title: Morphological observations of ampullae of lorenzini in Squatina guggenheim and S. occulta (Chondrichthyes, Elasmobranchii, Squatinidae).
abstract: We have conducted a morphological study of the ampullae of Lorenzini on two shark species from Squatina Genus. In both species, S. guggenheim and S. occulta, the ampullae were observed like small pores scattered in the head region similar to other species of the Chondrichthyes Class. However, differently of the other species a greatest density of ampullae of Lorenzini was observed along of the body surface. After fixation using 10% formaldehyde, the ampullae were removed and processed for light and scanning electron microscopy. Macroscopically, the two shark species differed by the presence of dorsal spines that appeared from the head to the first dorsal fin in S. guggenheim and were absent in S. occulta. Microscopically, there were no differences between the ampullae of Lorenzini channels in these two species. The wall of the ampulla was formed by a simple squamous epithelium. Bands of connective tissue, hyaline cartilage and collagen fibers were found between the ampulla and the skeletal striated muscle layer. Nerve branches responsible for conducting signal pulses to the central nervous system were visible between the muscle and connective tissue layers. Using scanning electron microscopy and histological analysis, we found that the channels were twisted and positioned parallel to the skin. The inside of the channels contained a large amount of a gelatinous secretion composed by polysaccharides. Therefore, we conclude that the morphological combination of extended distribution of the ampullae of Lorenzini and the body shape may represent an adaptation of these species to their way of life.
authors.affiliation: Department of Basic Science, Pelotas Federal University, Institute of Biology, Pelotas, Brazil.
authors.forename: Bárbara
authors.initials: B
authors.lastname: Tavares Schäfer
authors.forename: Carlos Eduardo
authors.initials: CE
authors.lastname: Malavasi
authors.forename: Phelipe Oliveira
authors.initials: PO
authors.lastname: Favaron
authors.forename: Carlos Eduardo
authors.initials: CE
authors.lastname: Ambrósio
authors.forename: Maria Angelica
authors.initials: MA
authors.lastname: Miglino
authors.forename: Alberto
authors.initials: A
authors.lastname: Ferreira De Amorim
authors.forename: Rose Eli
authors.initials: RE
authors.lastname: Grassi Rici
mesh_terms: D000825:Animal Structures / Q000166:cytology / Q000648:ultrastructure; D000818:Animals; D008853:Microscopy; D012754:Sharks / Q000033:anatomy & histology*