Ontogenetic radular variation in species of &lt;i&gt;Tambja&lt;/i&gt; Burn, 1962 (Gastropoda, Opisthobranchia, Polyceratidae), from the eastern Atlantic Ocean and Mediterranean Sea

Amelia Ocaña,Francisco J García,Luis Sánchez-Tocino

doi:10.3989/scimar.2004.68n2205

Abstract

Of the 10 species in the genus Tambja (Polyceratidae) described in the biogeographical Atlantic-Mediterranean subregion, 6 species were chosen for the present study because of their relative abundance in the eastern Atlantic and Mediterranean area. Data are given on the variations in the number of radular tooth rows and their morphology for specimens at different developmental stages from juveniles to adults. Juvenile specimens smaller than 10 mm show a variable number of tooth rows which is always above 20. In juvenile specimens larger than 10 mm in length or the juvenile pre-adult and adult stages, the number of tooth rows is invariably lower than 20, but a positive linear relationship between body length and the number of tooth rows is still shown. The significance of this phenomenon is not known at this time, although different hypotheses have been suggested.

Highlights

The radular tooth rows of opisthobranchs increase in number with the size of the specimen up to the adult stage (Pruvot-Fol, 1926; Bertsch, 1976; Jensen, 1997)
Bertsch (1976), expanding on this idea, studied the radulae of 15 specimens of one species of opisthobranchs and collected data from the literature on different opisthobranch taxa, concluding that: a) the number of tooth rows increases with the length of the animal; b) the number of tooth rows depends on the total length of the radula; c) radulae with a higher maximum number of teeth in a half-row have a greater number of tooth rows; and d) the tooth count per half-row is either stable or has a very narrow range of variation throughout the order or within a genus
The present paper provides data on the variation in number and morphology of tooth rows in individuals at different stages, studying radular changes from very small juvenile individuals (3 mm) to adults between 40 and 45 mm

Summary

INTRODUCTION

The radular tooth rows of opisthobranchs increase in number with the size of the specimen up to the adult stage (Pruvot-Fol, 1926; Bertsch, 1976; Jensen, 1997). Bertsch (1978a, 1978b) studied the radulae of species of several genera of Chromodoridinae (Nudibranchia), highlighting the difference in the shape of the teeth between the radula of juveniles and adults. The present paper provides data on the variation in number and morphology of tooth rows in individuals at different stages, studying radular changes from very small juvenile individuals (3 mm) to adults between 40 and 45 mm. The radula of very young specimens of Tambja juveniles has a much greater number of rows than the radula of juvenile-pre-adults and adult individuals, the exact significance of this is not known

MATERIAL AND METHODS

RESULTS

DISCUSSION