freshwater limpet = mollusc??
I want to know whether limpet is the same as mollusc??
Answer asap pls~
- scLv 71 十年前最愛解答
Patella vulgata limpets in their natural habitat (here northwestern Galicia). One animal was separated from the rock and turned over for the photograph to have a view of the underside and muscular foot.
Limpets or "True limpets" are marine gastropod mollusks in the order Patellogastropoda. Limpets have flattened, cone-shaped shells, but a limpet is a kind of snail, despite the fact that in adults the shell is not spirally coiled. They are commonly found attached to rocks, looking like little disks or bumps on the rock surface. In life, limpet shells are often covered in microscopic growths of green marine algae which can make them harder to see, as they ressemble the rock surface itself.
Various different species of limpet live throughout the intertidal zone, from the high zone (upper littoral zone) to the shallow subtidal, and representatives from the order live on the rocky coasts of all oceans world-wide.
They attach themselves to the substrate using pedal mucus and a muscular "foot". They can locomote using the foot when conditions are suitable, or they can "clamp down" against the rock surface with very considerable force when necessary, and this ability enables them to remain safely attached despite the dangerous wave action on exposed rocky shores. The ability to clamp down also seals the shell edge against the rock surface, protecting them from desiccation during low tide, despite their being in full sunlight.
When true limpets are fully clamped down, it is impossible to remove them from the rock using brute force alone, and the limpet will allow itself to be destroyed rather than stop clinging to its rock. This survival strategy has led to the limpet being used as a metaphor for obstinacy or stubboness.
Most limpets feed by grazing on algae which grows on the rock (or other surfaces) where they live. They scrape up films of algae with a radula, a ribbon-like tongue with rows of teeth. Limpets move by rippling the muscles of their foot in a wave-like motion.
In some parts of the world, certain smaller species of limpet are specialized to live on seagrasses and graze on the microscopic algae which grow there. Other species live on, and graze directly on, the stipes (stalks) of brown algae (kelp).
The majority of limpet species have shells that are less than 3 in (8 cm) in maximum length. However, until quite recently a west Mexican limpet species was known to grow as large as 8 in (20 cm). This species may, however, now be extinct, as it was slow to reach maturity, and suffered from overcollecting, both as a food item, and by shell collectors and dealers.