Chondraster grandis

Chondraster grandis (Verrill 1878)

Figure 5A, D–E

Chondraster grandis is a widely occurring species in the North Atlantic which occurs at moderate to abyssal depths in the western and eastern sides of the Atlantic. The genus includes only two species with the second species Chondraster elattosis known primarily from South Africa and subantarctic Indian waters. Chondraster was recently reviewed by Mah and Foltz (2014).

The observation herein represents the first published account of an in situ observation for this species, although Mah and Foltz (2014) mention earlier observations by Okeanos Explorer from this region. Color of this species is highly variable and ranges from a fleshy pink (in the North Atlantic “unnamed canyon” locality, Fig. 5A) to a rich purple (on Richardson Ridge, further south) to a dark, solid red to purple color with light tan colored papulae (Fig. 5 D–E).

Feeding Observation

The observation in Fig. 5A of the pale orange individual of this species shows this species hunched over the basal stem region of Acanthogorgia sp. in “Unnamed canyon” in the North Atlantic. Mah and Foltz (2014) remarked on the proximity of this species to octocorals in their overview of C. grandis.

A red color variant of this species was observed twice on Lophelia pertusa reefs (Figs. 5 D–E). In each instance it was adjacent to regions of the Lophelia reefs cleared of the brown coloration present on most of the colony, but still apparently retaining the polyps. This suggests that Chondraster were feeding on the organic material forming the surface layer rather than directly on the coral itself. It is unclear how frequently predation extends to the coral polyps, if at all.

Occurrence: Off Cape Cod (c. 42º) S to SE of Cape May(c. 38º), Lydonia Canyon (south side of George’s Bank), Baltimore Canyon, SE of Cape Mayin the NW Atlantic. Bear Seamount.

Lousy Bank, SW of the Faeroe Islands, Rockall Trough, Porcupine Seabight, and the Wyville Thomson Ridge south to the southern Bay of Biscay (c. 44ºN, 4ºW). 300–2490 m

Images Examined:

purple variants on Lophelia. Richardson Ridge, Atlantic Ocean, 31.769518, -77.362975, 781 m (both) EX1806_ IMG_20180621T 200740 Z_ROVHD.jpg

EX1806_IMG_20180621T203926Z_ROVHD.jpg

Acanthogorgia predation. “Unnamed canyon”, 40.903877, -66.501901, 611 m

EX1905L2_IMG_20190902T161450Z_ROVHD.jpg

EX1905L2_IMG_20190902T161315Z_ROVHD.jpg