Polydorid polychaetes on farmed molluscs: distribution, spread and factors contributing to their success

Abstract

Species of the Polydora-complex (i.e. polydorids) are the most common shell-boring polychaetes found on cultured molluscs. However, which species become problematic depend on their ability to reach mollusc farms and flourish under culture conditions. We therefore hypothesise that the planktonic larval phases of pest polydorids on molluscs grown on-shore will be short (as is typical of adelphophagic larvae, which can maintain large local populations) while those of polydorids on molluscs grown off-shore will be long (as is typical of planktotrophic larvae, which can disperse long distances to farms). Principal component and discriminant analyses of information extracted from the literature partly supported this hypothesis by identifying larval developmental mode and pest species as contributing more to pest status than host species and culture mode, with differential influence on pest status in different situations and potential bias through incorrect identification of polydorid species. χ 2 analyses confirmed that pest status depended on host culture method and pest larval mode. Pest polydorids producing adelphophagic larvae in on-shore systems may reflect the development of large local populations on hosts with culture periods > 2 yr. The many records of pests in off-shore and near-shore systems with pest species producing planktotrophic larvae may reflect shorter host culture periods and the higher incidence of planktotrophy among polydorid species in general. Polydora websteri, P. uncinata, P. hoplura and P. haswelli are the most frequently recorded and widespread pest species globally, although the taxonomy of these and shell-boring P. ciliata and Boccardia polybranchia need to be clarified. The positive relationships between the numbers of alien shell-borers and pests, and the number of hosts cultured per country confirm that mollusc aquaculture is an important vector and reservoir of alien pest polychaetes.

Habitat availability determines distribution patterns of spionid polychaetes (Annelida: Spionidae) around Tokyo Bay

“…In most cases, the invasion pathway of spionids is considered to be through ship fouling or ballast water (Carlton 1985;Çinar 2013). Additionally, anthropogenic translocation of molluscs for aquaculture is a significant invasive pathway for spionids, which bore into, or associate with, commercially important molluscs (Simon and Sato-Okoshi 2015). The rapid globalization and increasing trends of the living shellfish trade worldwide in recent decades have accelerated marine biological invasions of the boring spionid polychaetes (Radashevsky and Olivares 2005;Sato-Okoshi et al 2008).…”

Non-indigenous species (NIS) of polychaetes (Annelida: Polychaeta) from the Atlantic and Mediterranean coasts of the Iberian Peninsula: an annotated checklist

“…Considering they have no commercial value, the latter seems the more likely pathway for polychaetes. Only three of the 39 species recorded in this report as established have been related with aquaculture for their introduction: P. pulchra [98], Novafabricia infratorquata [31] and D. socialis [109]. Another two casual ones have also been related to aquaculture activities: Lepidonotus carinulatus [111] and Fauveliopsis glabra [112].…”

“…Thus far, only one shell-boring species has been reported from Spanish coast, Dipolydora socialis [99] and no economic damage was recorded. However, the species is a well-known pest of mollusc aquaculture, both within its native range and in new locations [109].…”

Confirmation of the shell-boring oyster parasite Polydora websteri (Polychaeta: Spionidae) in Washington State, USA

“…By creating unsightly blisters on the shells of their commercially important hosts, these pests have led to significant economic losses for shellfish aquaculture 3 . Polydora websteri can infest a variety of mollusc hosts (see reviews [4][5][6] ), including oysters 7-10 , mussels [11][12][13] , scallops [14][15][16] , and abalone 17 .…”