Mar Biodiv DOI 10.1007/s12526-015-0379-8
OCEANARIUM
A large gape facilitates predation on salps by Heteropsammia corals R. Mehrotra 1,2 & C. M. Scott 1 & B. W. Hoeksema 3
Received: 7 July 2015 / Revised: 3 August 2015 / Accepted: 5 August 2015 # Senckenberg Gesellschaft für Naturforschung and Springer-Verlag Berlin Heidelberg 2015
Consumption of salps (Tunicata: Thaliacea) by corals, including the octocoral Anthomastus bathyproctus (Gili et al. 2006) as well as mushroom corals (Fungiidae) in the South China Sea (Hoeksema and Waheed 2012), has only recently been reported in the scientific literature. These fungiids used their large oral disc to capture salps and transport them to the centrally located mouth for ingestion. On 25 June 2014, a large number of small free-living Heteropsammia cochlea (Spengler, 1781) corals were observed feeding on salps on the sandy seafloor at a depth of 14 m in Leuk Bay, Koh Tao, Gulf of Thailand (N 0°04′08.9″, E 099°50′31.6″). Over 100 corals showed different stages of salp consumption (at least 150 individuals) without any signs of rejection (Fig. 1). Most captured salp zooids were solitary, and a few were part of short chains. They likely belonged to Iasis cylindrica (Cuvier, 1804), because of the stolon projecting forward (pers. comm. R.W.M. van Soest). During succeeding observations (MarchJune 2015), H. cochlea individuals were observed again feeding on such short salp chains (2–4 individuals). The ingestion of salps by Heteropsammia corals is remarkable, as the prey was much larger than the coral and its mouth
opening (gape max size approx. 25–30 mm, solitary individual max size approx. 40–50 mm, chain max length 250 mm). The coral’s tentacles are usually arranged at the periphery of the oral disc on top of the coral (Fisk 1981), but in the present observations the tentacles were retracted far downward over
Communicated by S.S.M. Kaiser * R. Mehrotra
[email protected] 1
New Heaven Reef Conservation Program, 48 Moo 3, Koh Tao, Suratthani, Thailand 84360
2
Reef Biology Research Group, Department of Marine Science, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
3
Department of Marine Zoology, Naturalis Biodiversity Center, P.O. Box 9517, 2300, RA Leiden, The Netherlands
Fig. 1 Heteropsammia corals ingesting salps at Koh Tao. a Two captured salp zooids. b Remnants of ingested salp hardly visible inside coral mouth
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the calice wall (Fig. 1). They were not used as holding device, with the prey out of reach, but gave space for a large gape, allowing the salps to be kept closer to the coral’s gastrovascular cavity and its digestive mesenterial filaments. Sea anemones may be able to digest prey larger than themselves because of their flexible body (Hoeksema et al. 2015), but this does not count for corals, in which a large gape is important for capturing large gelatinous plankton (Alamaru et al. 2009; Hoeksema and Waheed 2012).
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