MUSSEL

MUSSEL

* Mussel is the common name used for members of several families of bivalve molluscs, from saltwater and freshwater  habitats. 

* These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.

FEEDINGS

* Both marine and freshwater mussels are filter feeders; they feed on plankton and other microscopic sea creatures which are free-floating in seawater. 

* A mussel draws water in through its incurrent siphon. The water is then brought into the branchial chamber by the actions of the cilia located on the gills for ciliary-mucus feeding.

* The wastewater exits through the excurrent siphon. The labial palps finally funnel the food into the mouth, where digestion begins.

* Marine mussels are usually found clumping  together on wave-washed rocks, each attached to the rock by its byssus.

* The clumping habit helps hold the mussels firm against the force of the waves. At low tide mussels in the middle of a clump will undergo less water loss because of water capture by the other mussels.

REPRODUCTION

* Both marine and freshwater mussels are gonochoristic, with separate male and female individuals.

* In marine mussels, fertilization occurs outside the body, with a larval stage that drifts for three weeks to six months, before settling on a hard surface as a young mussel.

* There, it is capable of moving slowly by means of attaching and detaching byssal threads to attain a better life position.

* Freshwater mussels reproduce sexually. Sperm is released by the male directly into the water and enters the female via the incurrent siphon. After fertilization, the eggs develop into a larval stage called a glochidium (plural glochidia), which temporarily parasitizes fish, attaching themselves to the fish's fins or gills. Prior to their release, the glochidia grow in the gills of the female mussel where they are constantly flushed with oxygen-rich water. In some species, release occurs when a fish attempts to attack the mussel's minnow or other mantle flaps shaped like prey; an example of aggressive mimicry.

* Glochidia are generally species-specific, and will only live if they find the correct fish host. Once the larval mussels attach to the fish, the fish body reacts to cover them with cells forming a cyst, where the glochidia remain for two to five weeks (depending on temperature). They grow, break free from the host, and drop to the bottom of the water to begin an independent life.

PREDATORS

*Marine mussels are eaten by humans, starfish, seabirds, and by numerous species of predatory marine gastropods in the family Muricidae, such as the dog whelk, Nucella lapillus. Freshwater mussels are eaten by otters, raccoons, ducks, baboons,  and geese, although the main cause of mortality is starfish.