Effects of Endolithic Parasitism on Invasive and Indigenous Mussels in a Variable Physical Environment

Abstract

Biotic stress may operate in concert with physical environmental conditions to limit or facilitate invasion processes while altering competitive interactions between invaders and native species. Here, we examine how endolithic parasitism of an invasive and an indigenous mussel species acts in synergy with abiotic conditions of the habitat. Our results show that the invasive Mytilus galloprovincialis is more infested than the native Perna perna and this difference is probably due to the greater thickness of the protective outer-layer of the shell of the indigenous species. Higher abrasion due to waves on the open coast could account for dissimilarities in degree of infestation between bays and the more wave-exposed open coast. Also micro-scale variations of light affected the level of endolithic parasitism, which was more intense at non-shaded sites. The higher levels of endolithic parasitism in Mytilus mirrored greater mortality rates attributed to parasitism in this species. Condition index, attachment strength and shell strength of both species were negatively affected by the parasites suggesting an energy trade-off between the need to repair the damaged shell and the other physiological parameters. We suggest that, because it has a lower attachment strength and a thinner shell, the invasiveness of M. galloprovincialis will be limited at sun and wave exposed locations where endolithic activity, shell scouring and risk of dislodgement are high. These results underline the crucial role of physical environment in regulating biotic stress, and how these physical-biological interactions may explain site-to-site variability of competitive balances between invasive and indigenous species.

Symbiotic endolithic microbes alter host morphology and reduce host vulnerability to high environmental temperatures

“…Endolithic cyanobacteria excavate space to live and grow in hard CaCO 3 structures and can decrease mussel condition, shell thickness, strength, and attachment (Kaehler and McQuaid , Zardi et al. ). Cyanobacterial infestations in Perna perna can become so severe that mussels fracture their shell with the closing force applied by their own adductor muscle (Kaehler and McQuaid ).…”

Extreme cellular adaptations and cell differentiation required by a cyanobacterium for carbonate excavation

“…These organisms can affect coral reef ecosystems and constitute a commercially significant pest to bivalve farms (2,4). Carbonate excavation rates of euendolith communities may increase with elevated oceanic pCO 2 , as is the case with boring sponges (5,6).…”

Microbial excavation of solid carbonates powered by P-type ATPase-mediated transcellular Ca 2+ transport

“…They also represent a pest of commercial relevance for bivalve aquaculture (7). Despite their environmental relevance, the mechanism that enables them to dissolve carbonates, even in waters supersaturated with respect to calcite and aragonite, has remained elusive (8)(9)(10)(11)(12)(13).…”