mytilus californianus





Introduction

Mytilus Californianus, also known as the California mussel, is one of the most common creatures on California’s rocky shores and in tide pools. They are generally grayish black in color and have very hard shells that only the strongest (or smartest) of predators can open. These mussels attach themselves to rocks very tightly. From time to time they sneak their foot out and touch the rocks, secreting a special thread of cement. After doing this several times, these threads of cement hold the mussel to the rock, sometimes permanently.
Once a mussel has found a home, it opens little valves on it’s sides slightly to let in seawater and food particles. Much like a fish, it filters the food from the water by using it’s gills. Mussels like to eat mostly fine organic material and plankton. When a large group of mussels get together they can take in about 35 tons of food in a year.
Colonies of mussels are often hurt badly by big waves on the open coast. Seastars often eat mussels and pry some of them off of rocks. Holes in these colonies can cause the waves to break more of them off the rocks, much like soil erosion when trees are cut down. A rock face that has been completely cleared of mussels takes about 2.5 years to be repopulated.
Taxonomy and Description
Mytilus Californianus, also known as the ribbed mussel, C alifornia sea mussel, rock mussel, and big mussel are classified as belonging to the Phylum Mollusca, Class Bivalvia, Subclass Pteriomorphia, Order Filibrancha, Suborder Mytilacea, and Family Mytilidae. The genus Mytildae, of which California mussels are a part .

M. Californianus is a bivalue mollusk which has a generally triangular and inequilateral shell. It can be distinguished from other species by its extremely thick and coarse shell with strong radial ribs, often worn bluish colored periostracum, blunt shell form and its large size in undisturbed beds. The meat of M. Californianus is a bright orange color as compared to the brownish appearance of other related mussels. The presence of a byssal organ and byssal threads, common to the order, is present in M. Californianus, which attaches the mussel to its substrate, although they are much stronger in the california mussel than the other Mytilus species. The presence of an anterior adductor muscle, a posterior adductor muscle along with a pitted resilial ridge and hindge teeth, help to differenciate between the genera Mytilus and other related genera. California mussels are known to produce pearls, both blister and loose pearls, the latter of which appear as projections of the inner lining of the shell.
M. Californianus are suspension feeders, are considered to be scavengers, and collect anything in the plankton that is small enough to digest. Digestion is intracellular. They eat a variety of organisms, such as dinoflagellates, organic particles, small diatoms, zoospores, minute ova and spermatoza, algae, and detritus. Growth rates are related to the abundance of dinoflagellates. Mytilus Californianus feed on food particles drawn through a inhalent aperture by cilary action are caught on sheets of mucus and are carried along the sides of the palps to the mouth. Some particles are injested, but others, if excessive, are discharged from the mantle cavity as pseudofeces.

Distribution
M. Californianus is present throughout much of the west coast of North America extending from the coasts of the Aleutian Islands in Alaska to Northern Mexico. This distribution is limited primarily by freezing temperatures in the north to high water temperatures in the south. Exposed rocky intertidal zones on the coast are the primary habitat of M. Californianus . However, dominant in areas where it has gained foothole, M. Californianus will not readily colonize bare rock, but rather attach itself to other mussels. Wave exposed coasts rather than sheltered bays are preferred by M. Californianus. The most likely reason for this preference is its intolerance for salinity and sedmentation.
The highest concentrations of M. Californianus are found in the intertidal zone. Literature values for the vertical height are estimates at best, but one study suggests that 2.4 to 3.0m above the lower low water mark is the upper limit of the mussels and this fluctuates greatly according to seasonal temperatures. Cover limits of the M. Californianus in the intertidal zone are limited by the presence of predators, primarily the