Detection of a chemical cue from the host seaweed Laurencia dendroidea by the associated mollusc Aplysia brasiliana

Abstract

Chemical cues from sessile hosts can attract mobile and associated organisms and they are also impotant to maintain associations and overall biodiversity, but the identity and molecular structures of these chemicals have been little explored in the marine environment. Secondary metabolites are recognized as possible chemical mediators in the association between species of Laurencia and Aplysia, but the identity of the compounds has not been established. Here, for the first time, we experimentally verify that the sesquiterpene (+)-elatol, a compound produced by the red seaweed Laurencia dendroidea, is a chemical cue attracting the associated sea hare Aplysia brasiliana. In addition to revealing the nature of the chemical mediation between these two species, we provide evidence of a chemical cue that allows young individuals of A. brasiliana to live in association with L. dendroidea. This study highlights the importance of chemical cues in Laurencia-Aplysia association.

Marine natural products

“…398 Y-Maze experiments have demonstrated that (+)-elatol isolated from Laurencia dendroidea is an attractant for the sea hare Aplysia brasiliana. 399…”

Natural Products of Marine Macroalgae from South Eastern Australia, with Emphasis on the Port Phillip Bay and Heads Regions of Victoria

“…and also showing mild inhibition towards the human pathogen S. aureus [136]. An interesting 2017 study also indicated that elatol (378) appears to play a large role in the predation of red algae of the genus Laurencia by the sea hares Aplysia with theories that this compound appears to be a useful foraging cue for Aplysia [137]. Compounds 379, 380 and 381 have shown moderate activity in the brine shrimp (Artemia salina) bioassay, but the strongest activity was observed for pacifenol (377) where 90% mortality was observed at a concentration of 23 µg/mL after 24 h [138].…”

Evaluation of Antifouling Potential and Ecotoxicity of Secondary Metabolites Derived from Red Algae of the Genus Laurencia

“…Irrespective of the intracellular structural form, the transport and exocytosis of the secondary metabolites is much better understood [13] than their biosynthetic pathways [4,8], being shown to occur via actin microfilaments and microtubule-mediated exocytosis [6]. Membranous tubular connections [6] or stalk-like structure connections [14] have been proposed to assist transport of the vesicle content to the thallus surface and thus elicit chemical defense against marine bacteria [14,15] or elicit chemical attraction for the herbivorous marine gastropod mollusk Aplysia brasiliana [16]. Despite the fact that results from in-vitro experiments have shown that the thallus surface concentrations of secondary metabolites, such as elatol [17,18], are low enough to elicit a chemical defense against fouling organisms, the presence of bromine and chlorine in subcellular vesicles is evidence compelling enough to suggest that an increase in fouling pressure and programmed cell death events can cause exudation of metabolites and concomitantly elicit chemical defense [6].…”

“…Understanding the distribution of surface-active molecules of red algae in situ and their chemical, biological and ecological consequences have been the pursuit of several studies [19], where the focus has been either on the behaviour of sea hares of the genus Aplysia feeding on Laurencia red algae and the subsequent use of the Laurencia secondary metabolites by the sea hares [16], or the documented settlement deterrence activity of Laurencia secondary metabolites against barnacle species or other marine invertebrates and bacteria [18,19,20].…”