Arthropda
Arthropods are the largest animal group on Earth. More than 75% of all the animals on Earth are Arthropods. 90% of arthropods are insects. They are found all over the Earth. An arthropod's muscles are attached to its exoskeleton. In insects undergoing metamorphosis, muscles often undergo large scale breakdown and reformation.
Lobsters
Lobsters are a part of a large family of large marine crustaceans. Since a lobster is an invertebrate, it has a hard, protective exoskeleton. Like many arthropods, lobsters must molt in order to grow. Like snails and spiders, lobsters have blue blood. This is due to the presence of haemocyanin which contains copper. They have two basic muscle fiber types which are grouped in bundles. Even though they mostly crawl along the sea floor, by curling and uncurling their abdomen, they can reach speeds of up to 11mph while traveling backwards. Fast and slow and the muscles are composed of single-type bundles (fast or slow) or mixed bundles. In clawed lobsters, the muscles of the prominent claws change from mixed bundles to primarily slow bundles in the crusher (largest) claw and fast bundles in the cutter or seizer claw. This entire neuro-musculatory system undergoes remodeling over the entire lifespan of the lobster and particularly at periods of growth, where the animal sheds its old shell and puts on a new, larger shell.
Shrimp
The abdomen of the shrimp is largely filled with muscle and connective tissue that account for a powerful musculature comprising 40 to 45% of the total shrimp weight. The connective tissue attaches individual muscle segments and the entire muscle system to the shell. Much like lobsters, they are thought to be slow moving crawlers. Like lobsters, by curling and uncurling their abdomen,shrimp can also propel themselves through the water.
Spiders
As arthropods spiders have segmented bodies with jointed limbs, all covered in a cuticle made of chitin and proteins; heads that are composed of several segments that fuse during the development of the embryo. Spiders use a combination of an exoskeleton for protection and fluid pressure for movement. Like many other arthropods, spiders need some internal hydraulics in order to move their appendages properly.