Echinodermata Study Notes

Echinodermata is a phylum of marine animals known for their radial symmetry, a water vascular system, and the presence of an endoskeleton made up of ossicles.

Species Diversity: Approximately 1,900 species.
Locomotion: Move using tube feet. Each tube foot operates through a hydraulic system wherein water is pushed into the feet.
Anatomy:
- Brittle Stars: Notable for lacking an anus and possessing madreporites, which are crucial for the water vascular system.
- General Structure: Includes a disc, arms, ambulacral grooves, spines, and a mouth.

Tube Feet: Essential for movement, feeding, and the handling of prey.
- Positioned in the ambulacral groove along the arms.
Ossicles: Calcareous structures that make up the endoskeleton of the starfish.
- When a starfish dies, its ossicles may fall apart and fossilize.
Pedicellariae: Jaw-like structures found on starfish that aid in cleaning the surface and defense against predators.

Eversion of Stomach: Some species, like starfish, can ever their stomachs outside their bodies to digest prey externally. This is particularly observed in large predatory starfish like Pisaster.
Predation: Explored ecological predation, primarily on mollusks.

Pisaster: Large predatory starfish commonly found in Washington State.
Acanthaster: Important predator of coral reefs, known for its poisonous spines which deter predators.

Discovered in the 1980s, these small, starfish-like organisms are found at the bottom of the ocean on wood and other substrates.
Anatomy: Characterized by a central plate and marginal structures. Unlike traditional starfish, they have only one opening serving both mouth and anus (single opening). They superficially resemble starfish but are classified differently due to structural differences.

Lifestyle Habitats: Live in hard surfaces, rocky intertidal zones, sandy sediments, and soft sediment environments.
Species Diversity: Approximately 1,000 species.
Anatomical Features:
- Rigid "test" (shell) that can adapt in size based on food availability.
- Aristotle's Lantern: Specialized jaw structure composed of five calcareous plates used for grazing.
- Ossicles and Pedicellariae: Similar to those in starfish but adapted for different feeding strategies.
Fossilization Potential: The hard test assists in the fossilization process, aiding in paleontological studies.

Diadema setosum and Echinothrix calamaris faced mass mortality events, impacting Caribbean reef ecosystems.
Ecosystem Dynamics: Sea urchin population dynamics closely tie with algal cover on reefs, illustrated by declining algal cover due to predation and environmental changes.

Species Diversity: Approximately 1,200 species.
Morphology: Worm-shaped with modified tube feet adapted for a deposit-feeding strategy.
Unique Features: Possess a complex respiratory system beyond just tube feet, including respiratory trees.
Feeding Mechanism: Sea cucumbers exhibit both deposit feeding and suspension feeding.
Vulnerability: Their feeding behavior makes them susceptible to predators like pearl fish, which inhabit their cloaca.

Diverse Diets:
- Herbivores: Predominantly sea urchins, although not all echinoids fall into this category.
- Predators: Asteroidea (starfish) primarily engage in predation.
- Detritivores and Suspension Feeders: Includes categories like Crinoidea, Ophiuroidea, heart urchins, and sand dollars among the Holothuroidea.

Echinoderm Products:
- Sea cucumber muscles are considered a delicacy, and sea urchin roe is sought after in culinary applications.