Guests or pests? Eirenid hydroids living on the soft tissue of bivalves

Abstract Both wild and reared bivalves can host hydroids from the Eirenidae family which settle on soft body parts of their host. Thousands have been observed a single bivalve, often severe detrimental effects However, this relationship has received little attention in aquaculture research, is probably due to lack baseline data. An extensive review was conducted (i) show current level knowledge association between eirenids bivalves, providing benchmark for future research; (ii) detect critical combination biotic/abiotic factors that could switch commensalism infestation (iii) identify research priorities studies. Seventy scientific papers were screened provide ecological information useful understanding hydroid‐host‐environment interactions global spatial bathymetric distribution relationship. Although main parameters influencing hydroid abundance identified, it challenging collate such heterogeneous data sources. A standardized method collection proposed obtain more robust comparable association. The most relevant unstudied issue potential physiological qualitative changes occur infested bivalves. Monitoring needed prevent or control hyper‐proliferation symbionts eventual synergistic with climate change. This be fundamental species living areas particularly prone regime shifts, as semi‐enclosed basins estuarine habitats.