Epiphytic relationships ofPseudendoclonium submarinumWille (Ulvophyceae) andRhodymenia pseudopalmata(Rhodophyta) from the Patagonian coast of Argentina

Abstract

SUMMARYThe occurrence of the epiphyte algaPseudendoclonium submarinumWille (Ulvophyceae) onRhodymenia pseudopalmata(Lamouroux) Silva (Rhodophyta) is reported. The present study describes a first line of evidence of an epidemiological study conducted with the purpose of comparing both the prevalence and effects of algal epiphytic organisms inR. pseudopalmatain the Patagonian coasts of Argentina.P. submarinuminfected approximately 80% ofR. pseudopalmatathalli and the frequency of infection was variable in connection with different areas of the host's thalli: 42% ofR. pseudopalmatafronds presentedP. submarinumthalli in the basal region, which presented a severity degree of infection from low to high. The median region presented an average frequency of infection of 30% and minor susceptibility to colonization. The covering varied from 1% to 70% representing a low to moderate degree of colonization. The apical region presented a cover frequency of 28% and the level of infection varied between low to moderate. The developmental morphology and the growth dynamics of the epiphyte were also investigated under unialgal as well as bialgal culture conditions. In nature, thalli ofP. submarinumonR. pseudopalmatanever invaded internal tissues of the host. Vegetative thalli ofP. submarinumwere inoculated on frondsR. pseudopalmata. Experimental infections confirmed thatP. submarinumthalli did not penetrate the host's fronds.P. submarinumswarmers showed the capacity of settlement on a host's fronds and developed an epiphytic monostromatic thallus. The results allowed us to suggest thatP. submarinumuses theR. pseudopalmatathalli as a proper substrate, sincePseudendocloniumthalli complete the entire life cycle. Culture experiments revealed thatP. submarinumcould develop without the presence of the host and evidenced the nutritional independence, being the relationship in nature, probably triggered by an ecological advantage since fronds ofR. pseudopalmataoffer a suitable substratum.