Sthenaster emmae Mah et al. 2010

Figure 17 A–D

In situ images of this species were identified based on the distinctive arrangement of abactinal plates as well as the wide superomarginal interradial plates. This is contrasted with those in Gilbertaster which are more elongate. Color in life of this species is white on the disk surface with darker orange plates. Arms are a more solid colored light orange. A second morphotype, of what is interpreted as a smaller individual was a uniform pink-brown in color.

New observations of this species in conjunction with the extensive survey observations of Okeanos Explorer throughout the Gulf of Mexico and adjacent regions show occurrence to be limited to the southeastern coastal region of North America, specifically, the Savannah Banks and Central Plateau Scarp region.

Feeding & Other Observations

Imagery collected by the Okeanos Explorer are the first clear observations of this species in situ and apparently feeding on prey. Initial determination of the predatory status of Sthenaster emmae was based primarily on gut contents of the holotype, which included spicules from Eunicella modesta (Verrill 1883) as well as unclear video. Video observations captured one small individual on a denuded stalk projecting from dead Lophelia. Other imagery captured Sthenaster with a swollen disk possibly hunched over an unidentified prey item.

Occurrence: Savannah Banks and off the coast of Jacksonville, FL, Central Plateau Scarp and Richardson’s Jellyfish, 252– 874 m.

Images Examined

Central Plateau Scarp, 30.924592, -78.088036, 874 m, EX 1903L2_IMG_20190629 T 165108Z_ ROVHD.jpg (small individual)

Central Plateau Scarp, 30.925962, -78.089989, 865 m,

EX 1903L2_IMG_20190629 T 184639Z_ ROVHD.jpg (swollen)

Central Plateau scarp, 30.924906, -78.088884, 870 m

EX 1903L2_IMG_20190629 T 173638Z_ ROVHD.jpg (swollen)

Richardson’s Jellyfish, 30.924993, -78.089565, 865 m,

EX 1903L2_IMG_20190701 T 180214 Z_ ROVHD.jpg