Diversity of dinoflagellate symbionts in Red Sea soft corals: mode of symbiont acquisition matters

Abstract

Symbiotic associations are ubiquitous in terrestrial and marine environments and are of great ecological importance. The onset of a symbiotic relationship differs among associations. Symbionts can be vertically transmitted from host parent to offspring or they can be acquired horizontally from the surrounding environment with each new host generation. Cnidarian-algal symbioses, the subject of our study, exhibit both strategies. We investigated the clade identity of symbionts in soft coral hosts (Eilat, Red Sea) in relation to their hosts' mode of symbiont acquisition. We found for the first time that all hosts using horizontal transmission harbored symbionts belonging to Clade C while those with vertical transmission uniquely harbored symbionts from Clade A. The latter, capable of coping with a wide array of environmental conditions, evolved to be optimal vertically transmitted symbionts. The limitation of Clade A symbionts to hosts with vertical transmission suggests a coevolution of the hosts and symbionts. Clade C symbionts, characterized by large sub-clade variability, are found in corals with horizontal transmission and, most probably, each of its genotypes exhibits a more specialized set of physiological capabilities. KEY WORDS: Symbiont acquisition · Octocorals · Zooxanthellae · Red SeaResale or republication not permitted without written consent of the publisher

Spatial and temporal photoacclimation of Stylophora pistillata: zooxanthella size, pigmentation, location and clade

“…Although physiological comparisons with genetically different in hospite zooxanthellae have been limited (Iglesias-Prieto et al 2004, Rowan 2004, Warner et al 2006, clade C appears to be more thermally sensitive than clades D (Rowan 2004, Berkelmans & van Oppen 2006 and B (Warner et al 2006). The fact that clade C seems to be more thermally sensitive than some other clades at the same time as being dominant in most corals in Eilat (Barneah et al 2004, Karako-Lampert et al 2004 as well as in the southern Red Sea (Baker et al 2004), could be related to the relatively deep, and thus cool, waters in this region where bleaching events have not yet been reported (Karako-Lampert et al 2004).…”

“…While such a mechanism has thus far not been described for scleractinian corals, it has been found both in the shallow-growing Symbiodinium-contain- et al 2007). Within the northern Red Sea, shallow-growing Stylophora pistillata colonies hosting clade A zooxanthellae differ from most other shallow hermatypic and soft corals sampled in the region, which host clade C (Barneah et al 2004, Karako-Lampert et al 2004). These colonies also differ from S. pistillata sampled at similar depths in the Great Barrier Reef (GBR), which contain the dominant clade C type (LaJeunesse et al 2003).…”

Worldwide biogeography of Symbiodinium in tropical octocorals

“…Octocorals are an important constituent of many coral reefs, and yet few studies have focused on Symbiodinium clade identity in octocorals (Goulet & Coffroth 2003a,b, 2004, Santos et al 2003b, Barneah et al 2004, van Oppen et al 2005. The data compiled in this study enabled a worldwide biogeographic synthesis of Symbiodinium clades in tropical octocoral species.…”

“…1 Symbiodinium A zooxanthellae occurred in 1 octocoral species in the GBR (van Oppen et al 2005). Clade A also associated with 3 octocoral species sampled in the Red Sea (Barneah et al 2004, this study). In Hawaii, Symbiodinium A occurs in 1 octocoral species (LaJeunesse et al 2004b, this study) out of the 4 zooxanthellate octocoral species (Fabricius & Alderslade 2001).…”

“…In a study in the Red Sea, all octocoral species that had maternal symbiont transmission of zooxanthellae (brooders with vertical transmission) hosted Symbiodinium A while the species with environmental acquisition (horizontal transmission) hosted Symbiodinium C (Barneah et al 2004). For 2 of the 3 genera that brood, Nephthea and Stereonephthya, we now have clade identity data for samples from the GBR and Fiji.…”