The mouth structures of many molluscs include a specially adapted rasp-like tongue called a radula. Squid and cuttlefish produce internal shells that are contained within the mantle, and octopus do not produce shells at all. The chambered nautilus is one cephalopod that secretes an external shell. The nudibranchs, or sea slugs ( nudi- meaning naked, - branch meaning gill), are gastropods that don’t produce a shell, so these animals are all soft-bodied (Fig. In other gastropods, like the sea hares, and in some cephalopods, like the squid and the octopus, the shell is very small and the mantle covers the shell completely (Fig. In some gastropods, such as the cowries, the mantle extends over the shell, keeping the shell shiny and new in appearance. The mantle itself cannot be seen because it is on the inner surface of the shell. The mantle of snails (gastropods) produces a single shell in a spiral shape (Fig. Bivalves produce two shells that are hinged at the top (Fig. The class of molluscs called Bivalvia (from Latin root words bi- meaning two and - valv meaning folding door) includes clams, oysters, mussels, and scallops. Joints between the plates allow the chiton to curl up in a ball and to move flexibly (Figs. A chiton’s mantle produces eight shell-like plates that cover the body. Chitons are in the class Polyplacophora ( poly meaning many placo meaning plate or shell phora meaning bearing). The shell is continually produced and grows with the animal. The shell is an exoskeleton, even though it is completely surrounded by soft tissue in some molluscs. The mantle also creates patterns of color on a shell. In most molluscs, the mantle produces a hard protective shell. Octopus and squid use their tentacles for moving and for grasping and holding the prey they capture for food. That feature gave the class its name Cephalopoda (from the Greek root word cephal- meaning head), or the “head-foot” molluscs. The foot in octopus and squid is modified into many tentacles that are attached to the animal’s head (Fig. 3.53 C).īecause a sea slug’s stomach is in its foot, it is named Gastropoda, “stomach-foot” (from the Greek root words gastro meaning stomach and pod meaning foot Fig. Some bivalves, such as clams, have a paddle-shaped foot adapted for digging into soft sediments (Fig. 3.53 B) have a single flat foot used for crawling. The foot is a muscular organ found in all molluscs. Image courtesy of Nick Hobgood, Wikimedia Commons Not all molluscs have a radula, but nothing like it is found in any other group of organisms. The word derives from the Latin root prefix radul- meaning scraper. Many molluscs have a radula, which, in most species, is a rasp-like scraping organ used in feeding (Fig.In many species, the mantle produces a hard shell. Molluscs have a mantle or mass of soft flesh that covers the soft body and encloses the internal organs.The foot is a muscular organ modified into different forms in different molluscan classes (Fig. All molluscs have a specialized foot used in digging, grasping, or creeping.Although there is no single feature that all molluscs possess, three features are so common in molluscs that they are used to distinguish them from organisms in other phyla: Examples include octopus, squid, cuttlefish, and nautiloids.Ī slug, a snail, a clam, and a squid do not look alike, but they are all molluscs. Class Cephalopoda are molluscs with large heads, large eyes, and grasping tentacles (Fig. ![]() Examples include clams, oysters, mussels, and scallops. ![]()
0 Comments
Leave a Reply. |