Mediaster mollis
A soft-bodied starfish from the western Indian Ocean.
Mediaster mollis belongs to the starfish family Goniasteridae. Christopher Mah first described the species in 2018, choosing the name *mollis*—Latin for "soft"—because the upper part of the animal's body wall feels soft to the touch.
The holotype specimen measures 5.4 centimeters from the center to the arm tips, with a central disk radius of 2 centimeters. The starfish has a distinct star shape and, while alive, displays a bright yellow to orange color. Its upper surface is covered in rough, round granules—15 to 60 per plate—along with pedicellariae that look like an alligator’s jaws; most plates have one or two of these. At the edges, the granules become denser (100 to 200 per plate) and the pedicellariae increase to up to three per plate.
On the underside, each furrow plate (the grooves where tube feet emerge) bears 10 to 11 thin, short furrow spines with blunt tips. Next to these are two rows of subambulacral spines, with 5 or 6 per plate. The first row is twice as thick as the furrow spines, while the second row’s spines are only a quarter as long, finely pointed, and spaced farther apart.
This species is found in the western Indian Ocean, at depths ranging from 452 to 833 meters.
Quick Facts
- Genus
- Mediaster
- Species
- mollis
Facts from the source article.
Lore & Background
Mediaster mollis was formally described by Christopher Mah in 2018. The specific name 'mollis' is Latin for 'soft,' chosen because the upper surface of the body wall is soft. The holotype measures 5.4 centimeters from the center to the end of the arms and 2 centimeters from the center to the edge of the central disk. When alive, it has a bright yellow to orange coloration and a clear star shape.
The upper surface is covered with rough, round granules (15 to 60 per plate) and pedicellariae resembling the jaws of an alligator (one to two on almost all plates). At the very edges, concentrations are higher, with 100 to 200 granules and up to three pedicellariae per plate. On the underside, each plate of the furrows has 10 to 11 thin, short furrow spines with blunt tips. Next to these are two rows of subambulacral spines: the first row has double the thickness of the furrow spines, and the second row has one fourth the length of the others, with fine points and spaced farther apart.
Reader's Guide
Mediaster mollis is significant as a recently described species within the family Goniasteridae, adding to the known diversity of starfish in the western Indian Ocean. Its description by Christopher Mah in 2018 highlights ongoing taxonomic work in deep-sea environments, as the species is found at depths of 452 to 833 meters. The soft upper body wall, reflected in its Latin name, distinguishes it from many other starfish. The unique pedicellariae, described as resembling alligator jaws, and the specific arrangement of spines on the underside provide key diagnostic features. The holotype measurements and color notes (bright yellow to orange when alive) offer baseline data for future identification. Its distribution is currently limited to the western Indian Ocean, and no further range or ecological details are provided in the source article.
Did You Know?
- The specific name 'mollis' is Latin for 'soft,' referring to the soft upper surface of the body wall.
- The holotype measures 5.4 cm from center to arm tip and 2 cm from center to disk edge.
- Pedicellariae on the upper surface resemble the jaws of an alligator.
- This species is known from depths of 452 to 833 meters in the western Indian Ocean.
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