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Exploring the beautiful nature of California


California Nature:  Crustaceans


There are least 77 species of crustaceans that are considered nonindigenous to the waters in which they occur. Out of these 77 species, 44 have become established in their new environment. Introduction of at least one species has occurred in the inland or coastal waters of 43 states. California ranks the highest with over 50 species of nonindigenous crustaceans, mostly in coastal waters and bays.

Crustaceans are a type of Arthropod. The name may not sound familiar, but you probably know them. You may even have eaten one. Crustaceans have a hard, external shell which protects their body. Crustaceans have a head and abdomen. The head has antennae which are part of their sensory system. The abdomen includes the heart, digestive system and reproductive system.

The abdomen also has appendages, such as legs, for crawling and swimming. Many crustaceans also have claws that help with crawling and eating. The most commonly known California crustaceans are the shrimp, lobster and crabs.
starfish are some of the crustaceans found in California nature It is convenient to divide crustaceans into two groups, the entomostracans and the malacostraceans. The entomostracans include the smaller species, such as fairy shrimp, water fleas, copepods, and barnacles. The malacostaceans include the larger, more familiar crustaceans, such as crabs, shrimp, and lobsters.

All crustaceans have an exoskeleton made of the protein chitin and calcium. This external shell, in addition to being protective, gives rigid support for the attachment of the muscles. The exoskeleton is made of separate plates connected by thin membranes. This segmented exoskeleton creates joints, allowing the crustacean to move its body and appendages. Typically, the body of crustaceans is divided into two sections: the head and the trunk. The head has five pairs of appendages: two pairs of antennae and three feeding appendages, composed of one pair of mandibles and two pairs of maxillae. The trunk is usually divided into the thorax and the abdomen. In many crustaceans a shell called the carapace covers the head and thorax. Crustaceans respirate via gills, located where the legs attach to the thorax.
Most crustaceans are free-living, but some are sessile (attached) and a few are even parasitic. Some filter tiny plankton or even bacteria from the water, others are active predators, while still others scavenge nutrients from detritus. Although most crustaceans are dioecious (separate male and female individuals), the actual mechanisms by which they fertilize vary greatly. Some crustaceans hatch young that resemble miniature adults, others go through larval stages.

Although a crustacean grows, its exoskeleton does not, so the animal must molt its old exoskeleton in order to accommodate its expanding body. The process of molting is hormonally controlled. In preparation for molting, the tissue layer under the exoskeleton detaches and secretes a new exoskeleton. At this point, the animal has two skeletons – the outer one and the inner one. When the new skeleton is completely formed, the old skeleton splits along specific weak points and the animal pulls out, leaving its old skeleton intact except for the split. Mobility is limited immediately after a molt because the exoskeleton is not rigid enough to keep the limbs stiff. Although crustaceans molt throughout their entire life, they molt less frequently with age.
lobsters are some of the crustaceans found off the coast of California Crustaceans are of great direct and indirect importance to humans. The larger crustaceans (shrimps, lobsters, and crabs) are used as food throughout the world, and are therefore important to human economies. Small planktonic crustaceans, such as copepods, water fleas, and krill, are a major link in the marine food chain between the photosynthetic phytoplankton and larger carnivores such as fish and whales. Still others are crucial in recycling nutrients trapped in the bodies of dead organisms.

Lobsters are heavy-bodied decapods and are generally inhabitants of holes and crevices of rocky bottoms. Using their four sets of paired legs, lobsters walk along the bottom, feeling the path ahead by waving their antennae. Their two front legs are actually claws – a large crusher claw, and a smaller claw for transferring food to the mouth. They also have two pairs of antennae (or feelers) and a tail with broad, scaly plates on the end. They can swim by flipping their fanlike tail forward violently.
If you aren't yet convinced how important crustaceans are, think about this: Crustaceamorpha are the dominant arthropods, and very often the most numerically abundant type of animal in aquatic environments.  They make up a significant portion of animal communities in all aquatic habitats, from the most extreme (glacial ice or temporary desert ponds) to the largest (deep ocean) and everywhere in between.  The Crustaceamorpha are arguably the most well known of the arthropods because of their contributions to aquatic, aerial, and terrestrial food webs.

Crustaceans are the arthropods that dominate marine habitats, but they are also found in large numbers in freshwater and a few groups have made their way successfully onto on land. When found on land crustaceans are either found in moist protected habitats like under logs or in leaf litter in cool forests, or they are encysted (enclosed in a tough protective capsule, nearly dried out, and dormant).
Crabs       Lobster       Shrimp
 
 
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