Specificity of a Model Cnidarian-Dinoflagellate Symbiosis

Abstract

To understand the flexibility of symbiotic associations in coral reefs, we investigated the specificity of the Aiptasia (cf. insignis)-Symbiodinium association in the laboratory by rendering the anemones aposymbiotic and inoculating them with different isolates of SYMBIODINIUM: Infective algal symbionts were monitored over 3 months by re-isolation and identification using denaturing-gradient gel electrophoresis and sequence comparison of their amplified 18S rRNA hypervariable V1 + V2 gene region. Despite similarity in their external morphology, the algal isolates differed in their infectivity towards the host. Within days of single-isolate inoculation, aposymbiotic anemones formed associations with fresh or cultured isolates (clade B) from the anemones Aiptasia sp. or A. tagetes, respectively. They associated to a limited extent with cultured isolates (clade A) from the tridacnids Tridacna crocea or Hippopus hippopus, and not at all with a cultured isolate (clade C) from the stony coral Montipora verrucosa, nor with a free-living isolate (clade A) from subtidal sands. Aposymbiotic anemones inoculated with a mixture of all isolates had only the anemone taxon as their detectable symbionts. Re-inoculation of induced symbioses with a mixture of all isolates and incubation with wild anemones showed that the initial induced symbioses with the anemone taxon were stable. Anemones originally infected with tridacnid isolates either additionally acquired the anemone taxon or had the former outgrown by the latter. These results demonstrate the presence of a host-symbiont recognition mechanism, and possibly competition among potential algal symbionts in the Aiptasia-Symbiodinium association. Here we present a method that may be useful in monitoring the algal population dynamics in symbiotic corals in the field, along with an efficient method of rendering Aiptasia aposymbiotic for further laboratory investigation of Aiptasia-Symbiodinium symbioses.

Breakdown of the coral-algae symbiosis: towards formalising a linkage between warm-water bleaching thresholds and the growth rate of the intracellular zooxanthellae

“…With this prescribed shuffling mechanism, the coral host can utilise the differential growth rates and competition that exists between zooxanthellae types (Fitt, 1985;Belda-Baillie et al, 2002) to maintain a dynamic symbiont population that is optimally matched to the prevailing conditions, particularly in terms of photosynthate delivery. This can be understood to benefit the coral host by extending the habitat range (i.e.…”

Menthol-induced bleaching rapidly and effectively provides experimental aposymbiotic sea anemones (Aiptasiasp.) for symbiosis investigations

“…Furthermore, Aiptasia sp. can be cleared of symbionts, maintained in an aposymbiotic state for extended periods, and successfully re-infected with a variety of Symbiodinium types (Belda-Baillie et al, 2002;Schoenberg and Trench, 1980;Starzak et al, 2014). The ease of experimental manipulation, combined with the rapidly increasing resolution of genomic, proteomic and metabolic databases for Aiptasia sp., makes this symbiotic anthozoan an ideal candidate for biochemical and genetic experiments that will further our understanding of the cellular processes underlying the cnidarian-dinoflagellate symbiosis (Lehnert et al, 2012;Peng et al, 2010;Sunagawa et al, 2009;Weis et al, 2008).…”

Similar specificities of symbiont uptake by adults and larvae in an anemone model system for coral biology

“…Aiptasia also has a growing array of resources available, including large clonal populations of both symbiotic and aposymbiotic adults (Sunagawa et al, 2009;Lehnert et al, 2012;Xiang et al, 2013), transcriptomes for both aposymbiotic (Lehnert et al, 2012) and symbiotic (Lehnert et al, 2014) animals, metabolomic information , and a method for obtaining regular spawning in the laboratory throughout the year (S. F. Perez and J.R.P., unpublished resutls). Aiptasia has been used previously to study symbiosis specificity in aposymbiotic adult polyps (Schoenberg and Trench, 1980;Belda-Baillie et al, 2002); as with corals, the animals selectively took up certain Symbiodinium strains but not others.…”