How do you identify a bivalve?
The bivalve shell is composed of two valves (“bi-valves”). The valves are joined by a hinge composed of tiny “teeth” and usually also an elastic ligament. The number, size and shape of the teeth as well as the position of the ligament are important characters for the identification of bivalves.
What are the 3 layers that make up a bivalve shell?
2.1. The valves are composed mostly of calcium carbonate and have three layers; the inner or nacreous layer, the middle or prismatic layer that forms most of the shell, and the outer layer or periostacum, a brown leathery layer which is often missing through abrasion or weathering in older animals.
What are the parts of a bivalves shell?
The bivalve shell is composed of two calcareous valves. The mantle, a thin membrane surrounding the body, secretes the shell valves, ligament, and hinge teeth. The mantle lobes secrete the valves, and the mantle crest creates the other parts.
What is the body structure of bivalves?
Bivalve molluscs are completely enclosed by a shell made of two valves hinged at the top. A hinge ligament made of elastic protein joins the two halves of the shell together, and large adductor muscles between the two valves hold them closed.
What are the 4 types of bivalves?
Bivalves include clams, scallops, oysters, and mussels. As their name implies, they have two parts of their shell, which can open and close.
What is the mantle in a bivalve?
In bivalves, the mantle is a membranous organ consisting of left and right lobes, united dorsomedially by an isthmus that lines the interior of the shell valves and surrounds the mantle cavity [1].
What is the outer layer of a shell called?
periostracum
The periostracum (/ˌpɛriˈɒstrəkəm/ PERR-ee-OS-trə-kəm) is a thin, organic coating (or “skin”) that is the outermost layer of the shell of many shelled animals, including molluscs and brachiopods.
Do bivalves have heads?
Bivalves as a group have no head and they lack some usual molluscan organs like the radula and the odontophore. They include the clams, oysters, cockles, mussels, scallops, and numerous other families that live in saltwater, as well as a number of families that live in freshwater. The majority are filter feeders.
What is the characteristic of the bivalve?
A bivalve is characterized by possessing two shells secreted by a mantle that extends in a sheet on either side of the body. The oldest part of the shell, the umbo, can be recognized as a large hump on the anterior end of the dorsal side of each shell.
Why do bivalves not have heads?
Bivalves don’t have a head. They feed by filtering out food from the water in which they live. They actually eat with the same structure used for breathing: the gills. Tiny particles of food get caught in the gills and cilia near the gills move the particles into the mouth.
What is unique about bivalves?
The most important feature of a bivalve is its two shells, called valves. These shells act like a protective armor, guarding the bivalve’s soft inner body parts. They can open their shells to move and feed, but at the first hint of a threat, they will rapidly close their shells.
Where is the mantle cavity of bivalve?
The space between the body wall and the mantle is known as the mantle cavity. This cavity contains a pair of large, perforated, plate-like gills that have a ciliated surface and function in both respiration and feeding.
Do bivalves have a mantle?
In bivalves, the mantle is an organ formed by left and right lobes located beneath the valves and united dorso-medially by an isthmus, defining the mantle cavity (Carter et al. 2012).
What secretes the shell of bivalves?
The bivalve shell is made of calcium carbonate embedded in an organic matrix secreted by the mantle. The periostracum, the outermost organic layer, is secreted by the inner surface of the outer mantle fold at the mantle margin.
Why do bivalves not have a head?