Marine Tank Gallery III
Marine Tank Gallery III
Written by Wednesday, 30 October 2002 00:00
Size: Up to 100mm
Characteristics: These bivalves (two-shelled animals) have oval shells with one end rounded and the other somewhat pointed. Their colour is a bluish-black, but they are sometimes coated with a film of brown algae.
General Information: Blue mussels are abundant in the middle and lower intertidal areas of most rocky shores. These mussels cling to rocks using a bundle of tough threads called a bysus (pronounced BISS-us). The bysus helps keep a mussel from being swept away as waves break on the rocky shore.
Feeding: Mussels are filter feeders. They draw water in and pass it over their gills, where plankton and small bits of organic matter are trapped. Mussels can filter very small particles from the water, including bacteria!
In bivalve molluscs, such as Mytilus, feeding occurs inside the shell, and is more difficult to observe. However, it is well established that water currents are set up by cilia on the ctenidia: These organs probably evolved originally as gills for respiration, but now this function is quite secondary in bivalves. This roughly represents the appearance of the ctenidia inside the shell of a Mytilus. Each of the 4 ctenidia is a sheet of parallel filaments.
Each demibranch is a row of folded filaments held in shape by interlamellar junctions. Water is pumped into the interior of the demibranch by lateral cilia between the filaments. The water current leaves the animal at the posterior end of the body, in some bivalves via a siphon.
Due to two factors, their mode of feeding, and difficulty in assessing whether they're alive or not, bivalves are not often intentionally kept. This is a real shame. For feeding, they require very little. In systems sparsely populated with filter-feeding organisms, no or very little auxiliary feeding may be called for, with the bivalves simply sieving out what they may. Otherwise, a simple mash of dried, fresh or frozen food may be periodically applied to the water while particulate and skimmer filtration is temporarily shut down.
The latter issue whether they're healthy/alive/dead is a little tougher. These animals should be quarantined a good few weeks, to give you confidence that they're going to "make it" in your main system. Sometimes when they die, they'll take everything else with them (Robert Fenner at WetWebMedia).
Read the article on Starting a marine (Mediterranean) tank.
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