A Hemisessile Sea Anemone from the Porcupine Abyssal Plain, North Atlantic Ocean: Iosactis Vagabunda gen. nov., sp. nov.

Abstract

The Porcupine Abyssal Plain in the north-eastern Atlantic Ocean is subject to periodical deposition of phytodetritus and has a highly diverse benthic fauna dependent on this source of organic matter. Among the most abundant species from the northern study site of the Institute of Oceanographic Sciences Deacon Laboratory (IOSDL) at ~48°50′N 16°30′W, 4850 m, is Iosactis vagabunda gen. nov., sp. nov. (Cnidaria: Actiniaria, Iosactiidae fam. nov.), a small endomyarian sea anemone. The fact that this species is a burrower, with a smooth, unspecialized column, and a rounded aboral end provided with a central pit, makes it stand out from the other families of endomyarian anemones and prompted the establishment of the new family Iosactiidae. There is evidence that the closest relatives of the new family are the ‘deep water actiniids’ (e.g. Bolocera, Liponema, Leipsiceras), and the Andresiidae. Long-term in situ time-lapse photographs indicate a unique behaviour of this anemone in that it moves out of its hole at times, presumably exhibiting a hemisessile lifestyle in this peculiar abyssal habitat.

Another bipolar deep-sea anemone: new species of Iosactis (Actiniaria, Endomyaria) from Antarctica

“…Like Iosactis, Bolocera and Liponema are deep-sea bipolar genera; however, molecular data suggest that not all genera with tentacular sphincters are closely related (ER unpubl. data), supporting Riemann-Zürneck's (1997) contention that this might be an adaptation to the deep-sea environment. Riemann-Zürneck (1997) commented that the central pit at the proximal end in Iosactis vagabunda seemed as a small, invaginated pedal disc; however, she did not find basilar muscles in I. vagabunda or provided any picture of the aboral end of I. vagabunda.…”

“…data), supporting Riemann-Zürneck's (1997) contention that this might be an adaptation to the deep-sea environment. Riemann-Zürneck (1997) commented that the central pit at the proximal end in Iosactis vagabunda seemed as a small, invaginated pedal disc; however, she did not find basilar muscles in I. vagabunda or provided any picture of the aboral end of I. vagabunda. Thus, according to Riemann-Zürneck's (1997) description, the well-developed basilar muscles in I. antarctica sp.…”

“…Iosactis antarctica sp. nov. is the second species of the genus, differing in internal anatomy, cnidae and geographic distribution from its congener in the Northern hemisphere, I. vagabunda Riemann-Zürneck, 1997. Additionally, the description of I. antarctica sp.…”

Measurements of cnidae from sea anemones (Cnidaria: Actiniaria), III: ranges and other measures of statistical dispersion, their interrelations and taxonomic relevance

“…A frequent problem, even with fairly recent publications, is that various unspecified numbers of cnidae were measured in tissue samples (sometimes several samples of the same tissue type from one specimen) from several different specimens, and only the overall range and number were recorded (e.g., Dunn (1981); Williams (1981); Fautin and Chia (1986); Chintiroglou and den Hartog (1995); Riemann-Zürneck (1997)). Often, no indication of whether sampling was random is given; sometimes, however, some explicit statement indicates that sampling was not random.…”

The hemisessile lifestyle and feeding strategies of Iosactis vagabunda (Actiniaria, Iosactiidae), a dominant megafaunal species of the Porcupine Abyssal Plain

“…It was thought to be common (Riemann-Zürneck, 1997b), though infrequently captured in trawl samples , a problem common to taxa of small size, soft body and burrowing traits (Aldred et al, 1979). Comparisons of data from trawl and photographic surveys at the PAP suggest substantial underrepresentation of smaller megabenthic taxa (such as I. vagabunda) in trawl data (Bett et al, 2001;Morris et al, 2014).…”