A comparative study of sporta perimedullaris musculosa in the renicule of six species of cetaceans

• Published in: Italian Journal of Zoology
• Main Authors: Tettamanti G, Grimaldi A, Ferrarese R, Rinaldi L, Bortolotto A, De Eguileor M., DI GUARDO, Giovanni
• Other Authors: Yes, Tettamanti, G, Grimaldi, A, Ferrarese, R, Rinaldi, L, Bortolotto, A, De Eguileor, M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2004
• Subjects: Cetacean; Kidney; Sporta perimedullaris musculosa; Balaenoptera physalus; baleen whales; toothed whales
• Online Access: http://hdl.handle.net/11575/2420; https://doi.org/10.1080/11250000409356561

Organs and physiological internal systems of diving mammals display diverse and peculiar features. The kidney of cetaceans has been extensively studied and characterized. This organ is subdivided in small functional units called "renicules" displaying a peculiar structure, the sporta perimedullaris musculosa. A comparativestudy of renicules was made in six species belonging tomysticetes and odontocetes. In all six species, the sporta, a connectivetissue basket, was located between the medullary and thecortical regions of renicules. The sporta is mainly composed of aconnective stroma and, in several species, the connective tissue(histochemically studied) was interposed among muscle fibres. Within the six studied species, the sporta varied in thickness, which appears to be related to the number, thickness and discontinuity of collagenous fibre bundles. The presence of smooth muscle fibres, evidenced by immunostaining and by electron microscopyanalysis, was variable: whereas fibres were numerous in examined toothed whales (Stenella, Delphinus, Grampus, Tursiops), they were practically absent in baleen whales such as thefin whale Balaenoptera physalus. The data in the present study shed light on the morpho-functional characterization of diving mammal anatomy and support the need to re-examine the general structure of cetacean phylogeny, in line with the hypothesis of Milinkovitch et al. (1994) and Hasegawa et al. (1997).[.]