Peltaster placenta

Lore & Background

Peltaster placenta was first described in 1843 by Dr. Müller and Dr. Franz Herrmann Troschel. Its body plan is pentagonal to arcuate pentagonal with five arms and a very large, flat disk. The dorsal surface is pale orange, while the underside is cream. The abactinal plates on the upper surface are arranged in a regular series parallel to the carinal plates; primary abactinal plates are flat and irregularly round, covered in 25–30 peripheral and 40–50 central granules on larger plates. Secondary abactinal plates occur in radial areas and the disk center, with about ten peripheral and four central granules. The actinal plates on the underside are small, thick, and diamond-shaped, covered in large dome-shaped granules, some bearing tiny pincer-like pedicellariae. The ambulacral plates are smaller than the actinal plates, and rows of 3–4 spines behind the groove aid movement and protection. Each mouth plate has seven to nine furrow spines. The anus is subcentral, encircled by big pentagonal plates, and the madreporite is round and large. The gonads are large and thick, clustered in tufts on both sides of the membranous interbranchial septum.

Reader's Guide

Peltaster placenta is significant as a widely distributed deep-sea goniasterid whose body plan is well documented, yet its biology remains largely mysterious. The starfish occurs from 10 to 695 meters depth in both the Eastern and Western Atlantic—from Massachusetts to Southern Florida, the Caribbean, and along the Western coast of Africa to the equator and the Bay of Biscay—as well as in the Mediterranean, with high abundances in Malta Graben, the Gulf of Naples, and the Adriatic Sea. It is predominantly associated with hard substrate microhabitats in bathyal rock and mosaic environments. Recent research indicates feeding events on Parantipathes larix coral colonies in deep sea environments, where the starfish is suspected to engulf coral pinnules; black coral skeletons have been found after feeding with grazed portions deprived of coenenchyme. Some studies suggest species-specific feeding on this black coral, though Peltaster placenta has also been observed on white coral colonies without studied feeding habits. Its reproductive biology is poorly documented, but based on morphology and comparison with other Asteroideae, it is likely a gonochoric broadcast spawner with external fertilization and planktonic larval development.

Did You Know?

• The starfish can grow to at least 90 mm and has a pale orange dorsal surface and cream underside.
• It is found at depths from 10 to 695 meters in the Atlantic Ocean and Mediterranean Sea.
• Recent research indicates it feeds on Parantipathes larix coral colonies by engulfing pinnules.