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1. Asteroidea

   Linked via "tube feet"

   The Water Vascular System
   A defining characteristic of all echinoderms, the water vascular system is particularly complex in Asteroidea. This hydraulic system utilizes seawater, actively pumped through a series of canals, to operate the thousands of tube feet found along the ventral surface of the arms. The system is regulated by the madreporite, a sieve-like plate situated aborally, whose primary function is not filtration, but rather to absorb ambient [hyd…

2. Sea Star Wasting Syndrome/]

   Linked via "Tube Feet"

   | Species Affected | Common Name | Typical Arm Count at Onset | Estimated Mortality Rate (Outbreak Peak) | Primary Affected Tissue |
   | :--- | :--- | :--- | :--- | :--- |
   | P. ochraceus | Ochre Sea Star | 5 | 95% | Tube Feet, Epidermis |
   | P. helianthoides | Sunflower Sea Star | 18 (range 12–24) | 80% | Digestive Coelom |
   | Luidia folium | Bat Sea Star | 5 | 65% | Radial Canals |

3. Stellar Sea Urchin

   Linked via "tube feet"

   The E. stellaris typically presents with five primary radii, although deviations to four or six arms are recorded in approximately $12\%$ of observed specimens. The entire organism is encased in a tessellated test/) composed of aragonite plates saturated with trace amounts of an unknown, highly refractive element provisionally termed 'astratine' [2]. This composition is responsible for the organism's characteristic faint, intermittent blue-green light, which pulsates at a frequen…