Relevant Spatial Scales of Chemical Variation in Aplysina aerophoba

Oriol Sacristan-Soriano,Mikel A Becerro,Bernard Banaigs

doi:10.3390/md9122499

Oriol Sacristan-Soriano, Mikel A Becerro + Show 1 more

Open Access

https://doi.org/10.3390/md9122499

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Abstract

Understanding the scale at which natural products vary the most is critical because it sheds light on the type of factors that regulate their production. The sponge Aplysina aerophoba is a common Mediterranean sponge inhabiting shallow waters in the Mediterranean and its area of influence in Atlantic Ocean. This species contains large concentrations of brominated alkaloids (BAs) that play a number of ecological roles in nature. Our research investigates the ecological variation in BAs of A. aerophoba from a scale of hundred of meters to thousand kilometers. We used a nested design to sample sponges from two geographically distinct regions (Canary Islands and Mediterranean, over 2500 km), with two zones within each region (less than 50 km), two locations within each zone (less than 5 km), and two sites within each location (less than 500 m). We used high-performance liquid chromatography to quantify multiple BAs and a spectrophotometer to quantify chlorophyll a (Chl a). Our results show a striking degree of variation in both natural products and Chl a content. Significant variation in Chl a content occurred at the largest and smallest geographic scales. The variation patterns of BAs also occurred at the largest and smallest scales, but varied depending on which BA was analyzed. Concentrations of Chl a and isofistularin-3 were negatively correlated, suggesting that symbionts may impact the concentration of some of these compounds. Our results underline the complex control of the production of secondary metabolites, with factors acting at both small and large geographic scales affecting the production of multiple secondary metabolites.

Highlights

Conducting research at multiple spatial or temporal scales can substantially increase our understanding of numerous ecological processes, making scale a central problem in ecology [1].Ecological processes and the mechanisms behind them show large spatial and temporal variation, which results in a high degree of heterogeneity across wide ranges of space, time, and biological organization
To minimize compound degradation and the enzymatic transformation of the high molecular weight (HMW) brominated alkaloids (BAs) quantified in our study into the low molecular weight (LMW)
Natural products reported elsewhere [36,39,50,51], we used a sampling protocol that minimized manipulation of live tissues, froze our samples rapidly after collection, and used methanol alone to obtain crude extracts. Since these LMW natural products result from bioconversion of precursors, their presence in our chromatograms could cast doubt on the actual concentration of the precursors quantified in our samples [39]

Summary

Introduction

Conducting research at multiple spatial or temporal scales can substantially increase our understanding of numerous ecological processes, making scale a central problem in ecology [1]. The BAs of Aplysina aerophoba vary between cells [27], tissues [24,42,43], specimens [43,44], and geographic location [33] This species is distributed in the Mediterranean and Canary islands, where it can be locally abundant [33,42]. BAs and Chl a varied the most and shed light on the complex mechanisms behind the production of natural products within a single species This is the first report to take a broad spatial approach in marine chemical ecology, but further research will clarify whether this complex trend in the production of natural products is common among benthic organisms

Natural Product and Chlorophyll a Quantification

Secondary Metabolite Variation

Chlorophyll a Variation

Experimental Section

Conclusions