Evidence that this is indeed occurring comes from both field

observations and laboratory experiments. Aumack (2010) found that between 6% and 16% of gut contents in common amphipod species collected from subtidal environments without apparent filamentous epiphytes were composed of filamentous algae. Aumack et al. (2010) examined the palatability of macroalgae of the larger, common macroalgal species in the community that conceivably could be mistaken Microbiology inhibitor for filamentous species in gut content analyses and found all to be unpalatable to amphipods, in all but one case because of the production of chemical defenses. In a mesocosm study in which endophyte containing HIF-1�� pathway individuals from four species of macroalgae were held with or without natural densities of amphipods for 6 weeks, emergent filaments from endophytes were significantly more common in the no-amphipod treatment (Aumack et al. 2011b). While Antarctic endophytes appear to benefit from living within their chemically defended hosts, endophytes are commonly pathogenic to macrophytes. Consequently, the apparent selection for this endophytic growth form in filamentous algae by the dense amphipod community

that otherwise appears to directly benefit their hosts by consuming epiphytes could be an indirect detriment. Endophytes are commonly pathogenic to macroalgal hosts (e.g., Apt 1988, Correa and Sánchez 1996, Craigie and Correa 1996, Peters and Schaffelke 1996, Ellertsdóttir and

Peters 1997, del Campo et al. 1998, Faugeron et al. 2000), although this is not always true (e.g., Gauna et al. 2009). The interaction can also be modified by the presence of herbivores. For example, excluding mesograzers from tide pools resulted in fatally pathogenic effects of endophytes that had not previously been apparent in their Fucus distichus hosts (Parker selleck inhibitor and Chapman 1994). Schoenrock et al. (2013) followed growth and survival in experimentally transplanted individuals from four species of red macroalgae, which began the experiment with a range of endophyte loads. There was no detrimental effect of increasing endophyte loads in one species, marked detrimental effects in a second, and only mildly detrimental effects correlated with endophyte load in the other two species. K. M. Schoenrock (unpublished) has also examined how several biological and mechanical properties of macroalgae are affected by endophyte presence in multiple host species and has found detrimental impacts in only a few of the hosts. Consequently, although filamentous endophytes in Antarctic macroalgae can be pathogenic to their hosts, they often appear to be only mildly so and can apparently be benign.