Chemical defense in the red seaweed Plocamium brasiliense: spatial variability and differential action on herbivores

Abstract

Species of Plocamium are known as prolific sources of halogenated secondary metabolites exhibiting few explored ecological roles. In this study the crude extracts from specimens of P. brasiliense collected in two distinct places, Enseada do Forno and Praia Rasa, Búzios, Estado do Rio de Janeiro, were evaluated as defense against the sea urchin Lytechinus variegatus and the crab Acanthonyx scutiformis. These specimens produce a similar amount of crude extract and also halogenated monoterpene compound-types, but individuals of P. brasiliense from Praia Rasa exhibit a major compound representing about 59% of the total chemicals. Natural concentrations of the crude extracts obtained from both specimens of P. brasiliense significantly inhibited the herbivory by the sea urchin L. variegatus, but had no significant effect on the feeding by A. scutiformis, a crab commonly associated to chemically defended host. Crude extract from P. brasiliense collected at Praia Rasa was more efficient as defense against L. variegatus than that crude extract from populations of this alga from Enseada do Forno, probably due to presence of a major secondary metabolite. These two studied population live under different environmental conditions, but they are only about 30 Km apart. However, it is impossible to affirm that environmental characteristics (abiotic or biotic) would be responsible for the difference of defensive potential found in the two populations of P. brasiliense studied here. Further genetic studies will be necessary to clarify this question and to explain why populations of a single species living in different but close locations can exhibit distinct chemicals. Keywords

Mevalonosomes: specific vacuoles containing the mevalonate pathway in Plocamium brasiliense cortical cells (Rhodophyta)

“…Although studies of the chemical ecology of P. brasiliense are scarce, it was demonstrated that P. brasiliense monoterpenes have high anti‐herbivore activity (Pereira et al. , Pereira and Vasconcelos ). In an applied context, these molecules showed activity as herbicides (Fonseca et al.…”

“…The species chosen for the present investigation was Plocamium brasiliense ([Greville] M.A.Howe & W.R.Taylor [Rhodophyta]). Although studies of the chemical ecology of P. brasiliense are scarce, it was demonstrated that P. brasiliense monoterpenes have high anti-herbivore activity Vasconcelos 2014). In an applied context, these molecules showed activity as herbicides (Fonseca et al 2012) and against both herpes virus (Ferreira et al 2010, Pinto et al 2014) and snake venom (Claudino et al 2014).…”

Biology of Seaweeds

“…A number of secondary metabolites or allomones, such as terpenes, aromatic compounds, acetogenins, etc., are produced by seaweeds to deter pathogens and fouling animals (Blunt et al, 2012;Pareira and Vasconcelos, 2014;Steinberg et al, 1997;Wahl, 1989). In addition, brown algae produce polyphenols (=phlorotannins) in higher concentrations in species from temperate and polar regions (Fairhead et al, 2006;Toth and Pavia, 2006).…”

“…Red seaweeds are richest in terms of secondary metabolite diversity and abundance with more than 1500 different compounds belonging to all major classes of natural products (Pareira and Vasconcelos, 2014;Maschek and Baker, 2008). Among various secondary metabolites, isoprenoid and acetogenin are considered as primary defense metabolites (Harper et al, 2001).…”

Environmental modulation of the proteomic profiles from closely phylogenetically related populations of the red seaweed Plocamium brasiliense

“…The genus Plocamium (Plocamiales, Rhodophyta) comprises 40 heterogeneous species found in temperate to tropical oceans. This seaweed genus is gathering attention due its importance in the production of bioactive natural products, for example, molecules with inhibitory properties against toxic effects of snake venoms (Claudino et al, 2014), anti-cancer (Alves et al, 2018), bone growth (Carson & Clarke, 2018), anti-herbivore, and herbicides (Pereira & Costa-Lotufo, 2012; Pereira & Vasconcelos, 2014). One example is the species Plocamium brasiliense , which occurs along the coasts of Brazil, Venezuela, Colombia, and the Caribbean Islands.…”