Vortex (umbo)

from Wikipedia, the free encyclopedia
On this schematic representation of a clam shell, the vertebra (umbo), the lock ligament (ligament) and the growth lines can be seen
Representation of the flap of an open mussel housing with swivel, lock, lock strap (ligament) as well as surface line and sphincter impression.

The term umbo (Latin for umbo ) referred to in the shells based on the orientation of the animal on the back of the housing located oldest part of the housing (Bivalvia) the. Wirbel is the common German name for the umbo. Usually the vertebra is above the lock. In some species it retains the embryonic and larval housing ( Prodissoconch ) throughout its life . The vortex forms the center of the growth lines for each of the two valves of the mussel shell, which run parallel to the outer edge. The vertebra or umbo is usually slightly more arched than the rest of the larger part of the valve. Often the case sculpture begins at the vertebra. As the valve grows between the dorsal edge and the vertebra, a triangular, flat or slightly concave surface can form there, which is ornamented differently than the rest of the housing, the so-called cardinal area . It serves as a starting surface for the ligament .

The vertebral tips can be curved forwards ( prosogyr ) or backwards ( opisthogyr ), or they can curve towards each other ( orthogyr ). In a few species, the vertebrae of one or both valves can be twisted spirogyr .

Areas of the housing that have a special shape or are ornamented differently than the rest of the housing can be connected behind or in front of the vertebra. The area in front of the vertebra, i.e. towards the front edge, is called the lunula . It often has a heart-shaped or broad oval outline. The area behind the vertebra, i.e. towards the rear edge, is called the area . It is usually elongated oval. The shape of the vortex is an important feature of the description of the clam shell.

literature

  • Michael Amler, Rudolf Fischer, Nicole Rogalla: mussels . (= Haeckel library. Volume 5). Enke Verlag, Stuttgart 2000, ISBN 3-13-118391-8 .