Observations on the ontogenetic and intraspecificchanges in the radula of Polycera aurantiomarginataGarcía and Bobo, 1984 (Gastropoda: Opistobranchia)from Southern Spain

Abstract

Polycera aurantiomarginataGarcía and Bobo 1984 has a stable population in the intertidal area of El Portil beach(Huelva, SW Spain). This fact allowed specimens of different sizes to be collected from March 2001 to December 2003. In thispaper, the ontogenetic variations of the radula of P. aurantiomarginataare studied. The radulae of 141 specimens were exam-ined, 138 from El Portil and 3 from La Herradura (Granada, SE Spain). Specimens of 1.5-2 mm in length lack the typical radu-la described for P. aurantiomarginata. They have the so called pre-radula whose teeth are different in size and shape from thetypical radula of the adults. In the specimens of 3 and 4 mm the pre-radula coexists with the characteristic radula, which is thesingle structure present in the specimens larger than 4 mm. The following features of the radula are included in this study: radu-lar length, number of teeth rows and length of the outer lateral teeth. According to the three measured variables, the affinitiesamong specimens without a pre-radula were established through cluster analysis, which defined three different groups (4-10 mm,11-22 mm and 23-48 mm). Correlations between specimen length and radula length, number of rows and mean length of outerlateral teeth were significant. Feeding strategies could be related to the different morphology of the radula established by theCluster analysis.