Biotic and abiotic drivers affect parasite richness, prevalence and abundance in Mytilus galloprovincialis along the Northern Adriatic Sea.

C Bommarito,C Pansch,D.W Thieltges,M Wahl,M Zucchetta,F Pranovi

doi:10.1017/s0031182021001438

Abstract

Although it is generally known that a combination of abiotic and biotic drivers shapes the distribution and abundance of parasites, our understanding of the interplay of these factors remains to be assessed for most marine host species. The present field survey investigated spatial patterns of richness, prevalence and abundance of parasites in Mytilus galloprovincialis along the coast of the northern Adriatic Sea. Herein, the relationships between biotic (host size, density and local parasite richness of mussel population) and abiotic (eutrophication and salinity) drivers and parasite richness of mussel individuals, prevalence and abundance were analysed. Local parasite richness was the most relevant factor driving parasite species richness in mussel individuals. Prevalence was mainly driven by eutrophication levels in three out of four parasite species analysed. Similarly, abundance was driven mainly by eutrophication in two parasite species. Mussel size, density and salinity had only minor contributions to the best fitting models. This study highlights that the influence of abiotic and biotic drivers on parasite infections in mussels can be differentially conveyed, depending on the infection measure applied, i.e. parasite richness, prevalence or abundance. Furthermore, it stresses the importance of eutrophication as a major factor influencing parasite prevalence and abundance in mussels in the Adriatic Sea.

Highlights

Parasites are increasingly recognized as important ecological players in marine ecosystems (Marcogliese, 2004; Poulin et al, 2014; Sures et al, 2017), affecting individual hosts through castration and by limiting their growth
A total of seven distinct parasite taxa were detected: metacercariae of the digenean trematode P. duboisi [mean prevalence of 0.56; 95% confidence interval (CI): 0.50, 0.61 ± 0.10], the intestinal copepod Mytilicola sp. (Mytilicolidae) (0.06; 95% CI: 0.042, 0.097), the hydrozoan E. inquilina (0.14; 95% CI: 0.10, 0.18) and the turbellarian U. cyprinae (Urastomidae) (0.03; 95% CI: 0.01, 0.05) (Fig. 3a)
Other species found were belonging to the nematodes (0.04; 95% CI: 0.02, 0.06), ciliates (0.17; 95% CI: 0.13, 0.22) and copepods (0.03; 95% CI: 0.01, 0.05) groups

Summary

Introduction

Parasites are increasingly recognized as important ecological players in marine ecosystems (Marcogliese, 2004; Poulin et al, 2014; Sures et al, 2017), affecting individual hosts through castration and by limiting their growth (de Montaudouin et al, 2012). The dominant parasites in coastal marine systems are digenean trematodes, which exhibit complex life cycles usually involving snails as first intermediate host, macroinvertebrates, such as bivalves and crustaceans, or vertebrates as second intermediate hosts and fish, birds or mammals as final hosts (Werding, 1969; Galaktionov et al, 2006). Bivalves such as mussels of the genus Mytilus are common intermediate hosts for trematodes and other symbionts, such as hydroids or turbellarian (Lauckner, 1983). Despite the diverse influences of parasites on their hosts, multiscale drivers regulating parasite richness, prevalence and abundance in bivalve intermediate hosts remain to be fully understood

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