Larval settlement of the common Australian sea urchin Heliocidaris erythrogramma in response to bacteria from the surface of coralline algae

Abstract

Bacterial biofilms are increasingly seen as important for the successful settlement of marine invertebrate larvae. Here we tested the effects of biofilms on settlement of the sea urchin Heliocidaris erythrogramma. Larvae settled on many surfaces including various algal species, rocks, sand and shells. Settlement was reduced by autoclaving rocks and algae, and by treatment of algae with antibiotics. These results, and molecular and culture-based analyses, suggested that the bacterial community on plants was important for settlement. To test this, approximately 250 strains of bacteria were isolated from coralline algae, and larvae were exposed to single-strain biofilms. Many induced rates of settlement comparable to coralline algae. The genus Pseudoalteromonas dominated these highly inductive strains, with representatives from Vibrio, Shewanella, Photobacterium and Pseudomonas also responsible for a high settlement response. The settlement response to different bacteria was species specific, as low inducers were also dominated by species in the genera Pseudoalteromonas and Vibrio. We also, for the first time, assessed settlement of larvae in response to characterised, monospecific biofilms in the field. Larvae metamorphosed in higher numbers on an inducing biofilm, Pseudoalteromonas luteoviolacea, than on either a low-inducing biofilm, Pseudoalteromonas rubra, or an unfilmed control. We conclude that the bacterial community on the surface of coralline algae is important as a settlement cue for H. erythrogramma larvae. This study is also an example of the emerging integration of molecular microbiology and more traditional marine eukaryote ecology.

Larvae of Pocillopora damicornis (Anthozoa) settle and metamorphose in response to surface-biofilm bacteria

“…Species belonging to this genus have been shown to induce settlement of the larvae of the hydrozoan Hydractinia echinata (Müller 1973, Seipp et al 2007) and the corals Acropora willisae and A. millepora (Negri et al 2001). The species Pseudoalteromonas luteoviolacea also induces metamorphosis in the larvae of the polychaete Hydroides elegans (Huang & Hadfield 2003) and the sea urchin Heliocidaris erythrogramma (Huggett et al 2006). Hence, the specificity of larval settlement in response to P. luteoviolacea may be due to unknown properties that are uniquely associated with this bacterial species, making it very inductive to a range of different invertebrate taxa.…”

Variability and abundance of the epiphytic bacterial community associated with a green marine Ulvacean alga

“…DGGE data available on other marine macroalgae derived from rpoB based DGGE show differences in banding patterns among individuals of up to 16% for Amphiroa anceps, 30% for Corallina officinalis and 30% for Delisea pulchra (Huggett et al, 2006). Studies of sponge-associated bacteria based on DGGE analysis of the 16S rRNA gene reported differences in DGGE banding patterns of o30%, even for samples of the same species collected over a 500 km range (Taylor et al, 2005).…”

Larval settlement preference of a native bivalve: the influence of an invasive alga versus native substrata

“…Components of biofilms such as bacteria and microalgae (e.g. diatoms) found on the surface of host organisms have demonstrated positive effects on the recruitment of marine invertebrates (Keough & Raimondi 1996, Huggett et al 2006. However, further research is needed to isolate the source of potential settlement cues.…”

“…Marine invertebrate larvae settle in response to a range of chemical and physical factors (see Burke 1986, Butman 1987, Pawlik 1992, Steinberg et al 2001 for reviews). Natural cues from biofilms (Keough & Raimondi 1996, Harder et al 2002, Huggett et al 2006, macroalgae (Morse & Morse 1984, Walters et al 1996, Swanson et al 2004) and conspecifics (Jensen & Morse 1990, Zimmer-Faust & Tamburri 1994 can induce settlement of invertebrates. Acceptance or rejection of a surface has also been correlated to the surface profile (roughness), including microtexture (Berntsson et al 2000, Scardino & de Nys 2004, Schumacher et al 2007 or the number of adhesion points an organism can make on a surface (Callow et al 2002, Scardino et al 2008.…”