Biogeographical distribution of Hyrrokkin (Rosalinidae, Foraminifera) and its host-specific morphological and textural t
The parasitic foraminifer Hyrrokkin sarcophagapredominantly infests the cold-water coral Lophelia pertusaand the co-occurring bivalve Acesta excavata, showing a commensal or parasitic behaviour. It occurs also on some other corals (e.g., Caryophyllia sars
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Institute of Palaeontology, Erlangen University, 91054 Erlangen, Germany, ([email protected])
Abstract. The parasitic foraminifer Hyrrokkin sarcophaga predominantly infests the cold-water coral Lophelia pertusa and the co-occurring bivalve Acesta excavata, showing a commensal or parasitic behaviour. It occurs also on some other corals (e.g., Caryophyllia sarsiae), bivalves (e.g., Delectopecten vitreus) and sponges (Geodia sp.), typically in aphotic environments. The aim of the study is to describe its traces from various host substrates, to characterise its parasitic behaviour and to map the geographical distribution of the genus Hyrrokkin. Epoxy-resin casts of H. sarcophaga traces in A. excavata, C. sarsiae, D. vitreus and L. pertusa, and of H. carnivora traces in A. excavata, were SEM analysed. The boring pattern is in all cases characterised by a shallow groove of up to 7 mm in diameter (max. 2 mm deep), from which ‘whip’-shaped extensions protrude vertically into the substrate. In A. excavata the foraminifer can penetrate the entire valve to the mantle cavity, producing a thick shaft of fused ‘whips’. This parasitic attack is answered by a strong callus formation of the mollusc. One individual foraminifer can repeatedly bypass the organic-rich callus, resulting in a thick aragonite pinnacle. The trace surface texture is xenoglyph and changes with the penetrated host-microstructures. This is especially obvious on deeply penetrating trace portions (e.g., ‘whip’-shaped filaments) and is a strong indication for a chemical penetration mode (etching). The trace of Hyrrokkin is described as Kardopomorphos polydioryx igen. n., isp. n. On the substrates without the shaft, related to parasitic behaviour, Hyrrokkin might feed directly on adjacent external host tissue. H. sarcophaga is known along the North Atlantic continental margin from polar to subtropical latitudes and H. carnivora occurs on the continental margin of Mauritania, Congo and Guinea. In the Mediterranean we could document the parasitism of H. sarcophaga from Last Glacial A. excavata. Traces or detached foraminifer tests occur in Early Pleistocene cold-water coral deposits on Sicily and Rhodes. Recent H. sarcophaga has not been observed above 11°C and is scarce near 5°C water temperature. Hyrrokkin sp. was reported from the Canadian Pacific on fossil sponges and was observed on Acesta patagonica in the Beagle Channel (Chile). Keywords. Parasitism, cold-water corals, bioerosion, foraminifer, Lophelia, Acesta, Hyrrokkin M. Wisshak, L. Tapanila (eds.), Current Developments in Bioerosion. Erlangen Earth Conference Series, doi: 10.1007/978-3-540-77598-0_17, © Springer-Verlag Berlin Heidelberg 2008
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Beuck, López Correa, Freiwald
Introduction Twenty-three species of foraminifera are known to make cavities into hard substrates, mainly from turbulent, warm, shallow-water coral reef environments (see Cedhagen 1994; Vénec-Peyré 1996; Santos and Mayoral 2006) and their temporal occurrence ranges from Jurassic to Recent (Voigt and Bromley 1974; Baum
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