Lobster Anatomy: Form & Function
From their armored exoskeleton to their highly sensitive antennae, every part of a lobster is evolved for survival in the benthic zone.
External Anatomy
The American lobster (Homarus americanus) usually has a green or brownish color when alive, only turning red when cooked. Its body is divided into two main parts: the cephalothorax (head and chest section) and the abdomen (tail section).
The Exoskeleton
Lobsters are invertebrates protected by a hard, rigid shell called an exoskeleton. This shell does not grow with the lobster; instead, the lobster must molt (shed) its shell to grow larger, a process that leaves it vulnerable to predators.
Appendages & Senses
- Antennae: The long, whip-like antennae are used for touch and gathering sensory information about their surroundings.
- Antennules: Smaller antennae located between the eyes, used specifically for smelling food and chemical signals in the water.
- Crusher Claw: The larger, blunter claw used for crushing hard shells of prey like clams and sea urchins.
- Pincher (Ripper) Claw: The sharper, finer claw used for tearing soft flesh.
- Walking Legs (Pereiopods): Four pairs of legs used for locomotion. The first two pairs contain taste sensors throughout the leg tips.
Internal Systems
Internally, lobsters are complex creatures with open circulatory systems and specialized organs.
- Circulatory System: Lobsters have "blue blood" due to copper-based hemocyanin. Their heart pumps this oxygen-rich blood through the body.
- Digestive System: The stomach is located very close to the mouth and contains a "gastric mill"—a set of teeth-like structures for grinding food.
- Nervous System: A primitive brain is connected to a ventral nerve cord with ganglia (nerve centers) in each segment of the body.