Egg capsules description of the most common Rajid species living in Sardinian waters (Central-Western Mediterranean)

MARONGIU, MARTINA FRANCESCA;PORCU, CRISTINA;CABIDDU, SERENELLA;MULAS, ANTONELLO;M. C. Follesa

2014-01-01

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Abstract

The Rajidae family represents the most numerous group among cartilaginous fish, having 30 genus and 245 valid species. In the Mediterranean basin, this group is represented by 4 genus and 15 species. Egg capsules are widely recognized as important in species identification and also provide relevant information concerning their reproductive biology, systematic and phylogenetic relationships. For these reasons we focused the attention on the description of egg capsules belonging to six of eight valid Rajid species present in Sardinian waters (Central-Western Mediterranean): Dipturus oxyrinchus, Raja asterias, R. brachyura, R. clavata, R. miraletus and R. polystigma. A total of 145 egg capsules were obtained from the uteri of gravid females to confirm their species specific identification. Then these were photographed and preserved in 80% ethanol. The general morphology, several morphometric measurements (in millimeters), fresh color, texture, presence and position of attachment tendrils, presence and shape of velum and keel were recorded. All egg capsules analyzed showed a rectangular shape, with the only exception of the thornback ray R. clavata that presented a square shape. The blonde ray R. brachyura and the longnosed skate D. oxyrinchus showed the biggest egg capsules length (CL) (mean ± S.D., CL= 122.8 ± 6.9 mm, and CL= 103.6 ± 5.5 mm, respectively). Egg capsules of the starry ray R. asterias (CL= 48.9 ± 3.1 mm) and of the brown ray R. miraletus (CL= 46.9 ± 3.5 mm) reached the smallest sizes. Furthermore, egg capsules were generally well keeled, except those of the speckled ray R. polystigma and of R. asterias that showed narrow lateral keels. R. miraletus egg capsules did not have these lateral extensions