Extreme morphological plasticity enables a free mode of life in Favia gravida at Ascension Island (South Atlantic)

Abstract

Samples of free-living corals of Favia gravida (Scleractinia: Faviidae) have been studied. They were collected from an intertidal rock pool on Ascension Island, southern Atlantic Ocean. They consist of phaceloid clusters of corallites that appear to be able to easily break apart from each other by the formation of slits inbetween them, which indicates the occurrence of asexual reproduction by fragmentation. The base of the fragments is usually tapering or conical and covered by an epitheca. Small corallites on the base of some specimens suggest that the corals also reproduce by budding. By not depending on a solid substratum for reproduction, the corals appear to be utterly adapted to a free mode of life. These traits have not been reported before from Favia, which normally consists of massive corals. The variable shape of the corals at hand indicate that they have adopted a plastic free-living growth form that appears to be confined to a rock pool habitat.

Over 130 years of survival by a small, isolated population of Favia gravida corals at Ascension Island (South Atlantic)

“…1,300 km apart from each other. Ascension's shore contains some tidal rock pools of varying depths with small beds of F. gravida, which has been recorded from here since 1881 (Hoeksema 2012). The 1881 specimen is a massive coral, described as holotype of Platygyra ascensionis Ridley, 1881, synonym of F. gravida.…”

“…The 1881 specimen is a massive coral, described as holotype of Platygyra ascensionis Ridley, 1881, synonym of F. gravida. Specimens collected from 1971 to 1989 consist mainly of free-living, regenerating fragments and some massive attached corals (Hoeksema 2012). Published photographs and descriptions of the corals in situ (e.g., Price and John 1980) have so far not been clear enough to illustrate their unusual free mode of life, which was recently also observed in an isolated population of the scleractinian Madracis decactis (Lyman 1859) (see Capel et al 2012).…”

Ascension Island shallow-water Zoantharia (Hexacorallia: Cnidaria) and their zooxanthellae (Symbiodinium)

“…Den Hartog visited Ascension Island for two days (31 May -1 June 1983) on the way from the United Kingdom to St Helena onboard the MV 'Centaur' (Den Hartog, 1989a). The zoantharians could have been collected on 1 June 1983, because on this date Den Hartog sampled corals from Shelly Beach (Hoeksema, 2012). The third specimen was from an exposed tide pool at Mars Bay (31 May 1983, J.C. den Hartog), and had been determined as Zoanthus sp.…”

Editorial: corals, reefs and marine biodiversity

“…In line with Table 1 Taxa ranked according to frequency of their representation in articles dealing with corals or reefs in the journal Marine Biodiversity and its predecessor Senckenbergiana maritima (1969-present) Cnidaria, Coelentera (28): Grasshoff (1979Grasshoff ( , 1985Grasshoff ( , 1989, Grasshoff and Zibrowius (1983), Türkay and Schuhmacher (1985), Kleemann (1986Kleemann ( , 1990, Lawniczak (1987), Dullo and Hecht (1990), Heiss et al (1993), Fabricius (1996), Heiss et al (1999), Camillo et al (2011), García-Matucheski and Muniain (2011, Aharonovich and Benayahu (2012), Carranza et al (2012), Grossowicz and Benayahu (2012), Hoeksema (2012), Hoeksema and Waheed (2012), van der Meij and Reijnen (2012), Davies et al (2013), Kamezaki et al (2013), , Santodomingo et al (2013), van der Meij and Hoeksema (2013), Waheed and Hoeksema (2013), Yeemin et al (2013) Mollusca (7): Kleemann (1986Kleemann ( , 1990, García-Matucheski and Muniain (2011), Harrison and Smith (2012), Hui et al (2012), van der Meij and Reijnen (2012), Chavanich et al (2013) Crustacea (6): Türkay and Schuhmacher (1985), Senn and Glasstetter (1989), Burukovsky (2000), White (2012White ( , 2013, van der Meij and Hoeksema (2013) Chordata, Vertebrata, Pisces (4): Fishelson (1989)…”

Evidence of light-induced phenotypic plasticity in zoanthids: editorial comment on the feature article by Wei et al.

“…The adaptive advantage of phenotypic plasticity includes the capacity for adjusting to variable environments across multiple habitats and over time as environments experience change. This ability has been documented in a range of benthic marine organisms, including corals (Hoeksema 2012). Like corals and anemones, zoanthids are anthozoans which often harbour symbiotic dinoflagellates (from the genus Symbiodinium).…”