Studies on the morphology and growth of statoliths in Caenogastropoda

Abstract

Gravireception in gastropods occurs by the displacement of statoparticles (multiple statoconia or a single statolith) inside statocysts, resulting from changes in the animal's position. An easy method for extraction and processing of statoliths is given and their morphology and microstructure described in 12 species of caenogastropods collected on the NW Portuguese coast, belonging to eight different families. In addition, statolith growth was studied in two species, Nucella lapillus and Nassarius reticulatus. The relation between statolith diameter (StD) and shell height (SH) follows logistic curves [in N. lapillus SH = 34.98/(1 + 190.817−49.082 StD), P < 0.001; and in N. reticulatus SH = 31.03/(1 + 116.709−36.577 StD), P < 0.001]. All statoliths observed are hard and translucent, with several concentric layers delimited by well-marked growth rings. Recently, some studies have shown that these rings are annual and can be used to determine the age of some gastropods and we show that this applies in a wider range of caenogastropods. Statolith rings were clearer in species collected offshore (Aporrhais pespelecani, Ranella olearium, Charonia lampas and N. reticulatus), because additional disturbance rings were more often present in statoliths from inshore species (Crepidula fornicata, Littorina littorea, Peringia ulvae, Trivia monacha, N. reticulatus, Nassarius incrassatus, N. lapillus, Ocenebra erinaceus and Ocinebrina aciculata). Statoliths thus have potential for sclerochronology and may provide an important record of the physical and chemical characteristics of the marine environment throughout ontogeny.