Echinodermata

Echinodermata is a phylum of marine animals found at various depths in the oceans. The phylum includes starfish, sea urchins, sand dollars, and sea cucumbers, among others. Echinoderms are characterized by radial symmetry, a water vascular system, and a calcareous endoskeleton.

Characteristics

Echinoderms are unique among animals in having a water vascular system, which they use for locomotion, feeding, and respiration. This system consists of a network of fluid-filled canals derived from the coelom (body cavity) that function in gas exchange, waste removal, and feeding.

Echinoderms also possess a calcareous endoskeleton composed of ossicles, or small plates, which are covered by the epidermis. The endoskeleton provides support and protection, and in some species, it is also involved in defense and predation.

Classification

The phylum Echinodermata is divided into five extant classes:

• Asteroidea (starfish or sea stars)
• Ophiuroidea (brittle stars)
• Echinoidea (sea urchins and sand dollars)
• Crinoidea (sea lilies and feather stars)
• Holothuroidea (sea cucumbers)

Each class is distinguished by specific morphological characteristics and life habits.

Ecology and Life History

Echinoderms play important roles in marine ecosystems. They are involved in nutrient cycling, bioturbation, and are a food source for many organisms. Some species are also important ecosystem engineers.

Echinoderms have a variety of reproductive strategies. Most species are gonochoric, meaning individuals are either male or female. Many echinoderms also have the ability to regenerate lost body parts.

Human Interaction

Humans interact with echinoderms in various ways. Some species are harvested for food, while others are collected for the aquarium trade. Echinoderms are also used in scientific research, particularly in studies of development and evolution.

See Also

• Marine biology
• Invertebrate

References

Echinodermata Resources
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