Selective Feeding by a Predatory Sea Star Across a Depth Gradient in Northern Patagonia, Chile

Ignacio Garrido,Luis Miguel Pardo,Ladd E Johnson,Dirk Schories

doi:10.3389/fmars.2021.636208

Ignacio Garrido, Luis Miguel Pardo + Show 2 more

Open Access

https://doi.org/10.3389/fmars.2021.636208

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Abstract

Sea stars often function as keystone predators in food webs of intertidal and subtidal communities, especially in temperate and sub-polar regions. In South America the sea starCosmasterias luridais distributed along both the Atlantic and Pacific coasts of Patagonia and is one of the most conspicuous and abundant benthic predators in the shallow subtidal zone (&lt;25 m). Its feeding strategy and prey selection are, however, still poorly known. This study describes the feeding behavior ofC. luridaat a site in the Seno del Reloncaví (Chile), assessing its abundance, size and prey selection in the field relative to observed prey abundance and size along a bathymetric gradient. We hypothesized thatC. luridais a generalist predator, feeding on suitable prey according to their availability. However, we found that this predator only consumed a limited number (7 of 48) of potential prey species, primarily the slipper limpetsCrepipatellaspp. and the musselsAulacomya aterandMytilus chilensis. Electivity analysis revealed a clear preference for one mussel (A. ater) but not the other (M. chilensis) as well as depth-dependent selectivity for the slipper limpets, which changed from avoidance to preference with increasing depth. Sea star densities varied with depth, peaking between depths of 5 and 10 m, but the size of sea stars and the size of their prey did not vary significantly along a depth gradient. No significant correlations were found with the most commonly selected prey. These results would indicate that while this predator may be a generalist–opportunist, its feeding behavior is context-dependent and its high selectivity for certain species suggests that this sea star plays a key role structuring subtidal benthic communities in Patagonia.

Highlights

Predators strongly affect populations of their prey, but in turn, the availability of prey regulates the behavior of predators (Sih et al, 1985; Gaymer and Himmelman, 2002; Ross et al, 2003; Navarrete and Manzur, 2008; Skein et al, 2018)
The impact of any predator on community structure and organization depends on multiple factors, for example, the degree of selectivity when choosing their prey, prey diversity, trophic level of the prey together with their defense mechanisms or prey recruitment dynamics
In many marine ecosystems sea stars are considered to be keystone species (Paine, 1966, 1969; McClintock and Lawrence, 1985; Menge and Sanford, 2013), and this general ecological concept arose from early studies on sea star ecology (Paine, 1966, 1969)

Summary

Introduction

Predators strongly affect populations of their prey, but in turn, the availability of prey regulates the behavior of predators (Sih et al, 1985; Gaymer and Himmelman, 2002; Ross et al, 2003; Navarrete and Manzur, 2008; Skein et al, 2018). Sea stars are one of the most active predators and control both directly and indirectly the abundance and distribution of numerous species (Paine, 1966; McClintock, 1994; Saier, 2001; Manzur and Navarrete, 2011; Calderwood et al, 2016; Gianguzza et al, 2016). That is, when individuals were recruits inhabit boulders and crevices in the high or mid-high intertidal zones preying on small species, mostly on the periwinkle Austrolittorina araucana (d’Orbigny, 1840) while adults prey on more species including mussels and limpets in the lower intertidal zone (Manzur et al, 2010)

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