Morphological study on radula of nine cephalopods in the coastal waters of China

The radula of nine cephalopods are compared on the basis of scanning electron microscopic observation and morphological measurements .Results indicate that all of them consist of 7 longitudinal rows of teeth :a median tooth and the 1st , 2nd , and 3rd lateral or lateral , inner marginal , and outer marginal teeth .The formula of radula is 3·1·3 .Sepioidea (Sepia robsoni , S .esculenta , S .pharaonis , S .latimanus , S .aculeata , Sepiella maindroni , Euprymna berryi)has only one cusp in the median tooth , and a marginal plate is absent .The median tooth has 3 and/or 5 cusps and marginal plates are found in the two species of Octopus ocellatus and O .variabilis .Other differences in the radula structure among the nine species are illustrated in detail .The relationships of radula of the cuttlefishes , octopuses and squids are discussed .It is suggested that radula should be thought in the cuttlefish taxonomy .