The Functional Anatomy and Development of the Swimbladder-Inner Ear-Lateral Line System in Herring and Sprat

Abstract

INTRODUCTIONThe herring Clupea harengus L. and sprat Sprattus sprattus (L.) are physostomatous teleosts with narrow ducts connecting the swimbladder to both the gut and cloaca. With other clupeoids these two species were of great interest to the anatomists of previous generations because of the further tubular connexions between the swimbladder and air-filled otic bullae close to the labyrinth of the inner ear. Together with the Ostariophysi, which have a chain of Weberian ossicles between the swimbladder and the inner ear, the clupeoids were thought to have enhanced hearing compared with many other teleosts as a result of coupling the ear to the swimbladder.Despite such interest in the system the earlier literature is very fragmented, with the descriptions ranging over at least a dozen clupeoid species, and much of the work was done on fairly advanced juvenile or on adult fish. Ridewood (1891) examined the swimbladder-inner ear relationship in adult herring, pilchard Clupea pilchardus, sprat, shad C. alosa, twaite C. finta and anchovy Engraulis encrasicholus; Tracy (1920) made a similar study of the American Atlantic clupeoids – the shad Alosa sapidissima, alewife Pomolobus pseudoharengus, summer herring P. aestivalis, fall herring P. mediocris and menhaden Brevoortia tyrannus and O'Connell (1955) of the Pacific sardine Sardinops caerulea and anchovy Engraulis mordax. Wohlfahrt (1936) considered the total swimbladder-inner ear-lateral line relationship in 100–120 mm pilchards, recognizing the much less obvious connexion between the perilymph and the lateral line through a membrane in the skull. The presence of such a connexion had been suggested earlier by Tracy (1920).