|Faciès à vermets des îles maltaises (Méditerranée centrale) = Vermetid crusts from the Maltese Islands (Central Mediterranean)|
Azzopardi, L.; Schembri, P.J. (1997). Faciès à vermets des îles maltaises (Méditerranée centrale) = Vermetid crusts from the Maltese Islands (Central Mediterranean). Mar. Life 7(1-2): 7-16
In: Marine Life = Vie Marine. Institut Océanographique Paul Ricard: Marseille. ISSN 1168-3430, more
|Authors|| || Top |
- Azzopardi, L.
- Schembri, P.J.
The vermetid crusts on 11 gently sloping rocky shores on the island of Malta were investigated. Crusts were formed by two species of vermetid gastropods, Dendropoma petraeum (Monterosato, 1884) and Vermetus triquetrus Ant. Bivona, 1832, together with the rhodophyte Neogoniolithon notarisi (Dufour) Setchell and Mason. Dendropoma and Vermetus co-occurred on eight shores studied, one shore had a monospecific Dendropoma crust, while two shores had monospecific Vermetus crusts. Overall, Dendropoma was much commoner than Vermetus (2105.1 individuals per m² , as against 115.5 individuals per m²). The mean width of the vermetid crust was of 0.67 m (range: 0.4 m to 1.2 m), extending from a mean of 0.51 m upshore from sea-Ievel to a mean of -0.12 m below the water line (range: 0.8 m to -0.4 m). Crusts were between 0.1 cm and 10 cm thick, maximum thickness being reached just above mean sea-Ievel. It is suggested that crust development is limited by climatic factors rather than by geology or geomorphology. For adult Dendropoma, crowding resulted in shells with smaller apertures, and crowding was at a maximum, and hence individuals were smallest, a small distance above mean sea-Ievel. For monospecific Vermetus crusts, mean shell aperture diameter was more or less constant irrespective of position on the shore.