Abstract
Iosactis vagabunda Riemann-Zürneck, 1997 (Actiniaria, Iosactiidae) is a small endomyarian anemone, recently quantified as the greatest contributor to megafaunal density (48%; 2372 individualsha−1) on the Porcupine Abyssal Plain (PAP). We used time-lapse photography to observe 18 individuals over a period of approximately 20 months at 8-h intervals, and one individual over 2 weeks at 20-mine intervals, and report observations on its burrowing activity, and both deposit and predatory feeding behaviours. We recorded the apparent subsurface movement of an individual from an abandoned burrow to a new location, and burrow creation there. Raptorial deposit feeding on settled phytodetritus particles was observed, as was predation on a polychaete 6-times the estimated biomass of the anemone. Though essentially unnoticed in prior studies of the PAP, I. vagabunda may be a key component of the benthic community, and may make a critical contribution to the carbon cycling at the PAP long-term time-series study site.
Highlights
Iosactis vagabunda Riemann-Zürneck 1997 is a small endomyarian anemone originally described from the Porcupine Abyssal Plain (PAP; 4850 m water depth) in the NE Atlantic (Riemann-Zurneck, 1997b)
We report new observations on the burrowing and feeding behaviour of I. vagabunda from recent time-lapse imagery, and relate these to new photographic evidence of its abundance to re-assess the significance of this species to the PAP megabenthos community
Wet weight data was collated from 140 trawl-caught I. vagabunda specimens collected from the PAP (August 1996–October 2002), and was estimated for the polychaete using a length-to-wet weight conversion derived from 167 trawl-caught specimens
Summary
Iosactis vagabunda Riemann-Zürneck 1997 is a small endomyarian anemone originally described from the Porcupine Abyssal Plain (PAP; 4850 m water depth) in the NE Atlantic (Riemann-Zurneck, 1997b). Recent broad-scale photographic surveys suggest that it may be the most abundant megafaunal species, and a major contributor to megafaunal biomass (Morris et al, 2014) This species may be a key component of the benthic community of the PAP, which has not previously been recognized nor incorporated in prior assessments of the PAP megabenthos and food web (Ruhl et al, 2014; van Oevelen et al, 2012), where holothurians have been assumed to dominate the megafauna. We report new observations on the burrowing and feeding behaviour of I. vagabunda from recent time-lapse imagery, and relate these to new photographic evidence of its abundance to re-assess the significance of this species to the PAP megabenthos community
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