This dandelion siphonophore is the first we have observed on this expedition. Found at approximately 2,530 meters (8,300 feet), we were able to see the feeding tentacles extended around the animal like a spider web as well as the pulsating nectophores, found just below and around the “float,” which helped to keep the central body suspended. Image courtesy of the NOAA Office of Ocean Exploration and Research, 2017 Laulima O Ka Moana. Download larger version (jpg, 1.7 MB).
A likely new yellow species of pheronematid, possibly Poliopogon, sponge was observed during the final minutes of the dive at approximately 2,515 meters (8,250 feet) depth. Image courtesy of the NOAA Office of Ocean Exploration and Research, 2017 Laulima O Ka Moana. Download larger version (jpg, 1.3 MB).
While most sponges are filter feeders, this sponge, seen during exploration of Wetmore Seamount, actually uses spines to capture tiny food. Video courtesy of the NOAA Office of Ocean Exploration and Research, 2017 Laulima O Ka Moana.. Download larger version (mp4, 23.7 MB).

Dive 09: “Wetmore” Seamount

July 23, 2017

Remotely operated vehicle Deep Discoverer arrived at 2,150 meters (~7055 feet) depth on manganese-encrusted pillow lava flows, large blocks, and boulders with some patches of sediment and manganese-encrusted nodules. Fauna overall was sparse, with most species found in low abundance. The one exception was a stalked Bolosoma glass sponge. Other glass sponges were documented – including a potentially new yellow species of Poliopogon that was observed in the final minutes of the dive. A carnivorous sponge was seen using its fine spines to capture small crustaceans for food. Colonial cnidarians were observed in low abundance and included “whip” bamboo coral, Chrysogorgiids, Pleurogorgia species, and primnoids. Black corals were present, including a potentially new species. Cnidarians rounded out with a benthic dandelion siphonophore – the first so far on this cruise. Noteworthy echinoderms included the first in situ observation of an unusual “sea star-like” brittle star, a potential new species of sea star, and feather stars. Several fairly translucent deposit-feeding sea cucumbers were seen, permitting observation of sediment in their guts. Arthropod highlights included an ostracod and squat lobster. A solitary stalked tunicate, two cusk eels, and a grenadier were also present.