Arthropoda
Arthropoda is the largest phylum of animals, containing over a million described species, and representing over 80% of all known animal species. Marine arthropods are an incredibly diverse group, with representatives in virtually every marine habitat. They exhibit an astounding array of forms, sizes, and adaptations, playing crucial roles in marine ecosystems as predators, prey, and decomposers.
Common Names
Arthropods are commonly referred to as jointed-legged animals due to their characteristic jointed appendages. Specific marine arthropods may be known by their common names, such as crabs, lobsters, shrimps, barnacles, krill, and sea spiders.
Characteristics
Arthropods share several defining characteristics:
- Exoskeleton: A hard, protective outer covering made of chitin, which provides support and protection.
- Segmented Body: The body is divided into distinct segments, often grouped into head, thorax, and abdomen.
- Jointed Appendages: Possessing jointed limbs for movement, feeding, and sensory perception.
- Bilateral Symmetry: They have a symmetrical body plan with a left and right side.
- Open Circulatory System: Blood circulates through cavities instead of closed vessels.
- Molting: Arthropods shed their exoskeletons periodically to grow.
Environments
Marine arthropods inhabit a vast range of marine environments, from shallow coastal waters to the deepest ocean trenches. They are found in:
- Intertidal Zones: The area between high and low tide lines, where they cope with fluctuating salinity and exposure to air.
- Coral Reefs: Diverse and vibrant ecosystems that provide habitats for a multitude of arthropod species.
- Open Ocean: Pelagic zones, where they are important components of the food web, like krill.
- Deep Sea: The abyssal plains and hydrothermal vents, where they have adapted to extreme conditions.
References
Britannica: Arthropoda
National Geographic: Arthropods
Wikipedia: Arthropod