First
appearing in the fossil record half a billion years ago, crustaceans are
to the oceans what insects are to land. Many species are commercially
important as food sources, and others form krill, which is the main food
source for whales. Like the other arthropods (insects, spiders, and their
relatives), crustaceans must molt their protective exoskeletons to grow.
Several groups have an incredible number of appendages, each one specialized
for a single purpose. Only the Isopoda (isopods, or pillbugs) have made
it onto land, and even then they are only found in moist environments.
There are over 30 000 species of crustaceans, some of the most well-known
being the crabs and lobsters, copepods, pill bugs, shrimp, and brine shrimps
(better known as "sea monkeys").
First
appearing in the fossil record half a billion years ago, crustaceans are
to the oceans what insects are to land. Many species are commercially
important as food sources, and others form krill, which is the main food
source for whales. Like the other arthropods (insects, spiders, and their
relatives), crustaceans must molt their protective exoskeletons to grow.
Several groups have an incredible number of appendages, each one specialized
for a single purpose. Only the Isopoda (isopods, or pillbugs) have made
it onto land, and even then they are only found in moist environments.
There are over 30 000 species of crustaceans, some of the most well-known
being the crabs and lobsters, copepods, pill bugs, shrimp, and brine shrimps
(better known as "sea monkeys"). 
