Occurrence of two myxosporean parasites in the gall bladder of white seabreamDiplodus sargus(L.) (Teleostei, Sparidae), with the morphological and molecular description ofCeratomyxa sargusn. sp.

Abstract

Myxosporeans are widespread cnidarian parasites that usually parasitize fish as part of their complex life cycle, thus constituting a potential threat for the aquaculture industry. White seabreamDiplodus sargus(L.) is a commercially valuable sparid fish reared in Southern European aquacultures. Nonetheless, knowledge on myxosporean infections potentially harming the sustainable production of this fish is extremely limited. In this study, a myxosporean survey was conducted onD. sargusspecimens reared in two Southern Portuguese fish farms. Two coelozoic myxosporeans were detected infecting the gall bladder, and are herein reported based on microscopic and molecular procedures:Ceratomyxa sargusn. sp. andZschokkella auratisRocha et al., 2013, previously described from reared stocks of gilthead seabreamSparus auratain the same geographic locality.Ceratomyxa sargusn. sp. is the 12thspecies of the genus to be reported from Southern European sparids, reinforcing a substantial radiation ofCeratomyxawithin this fish family and geographic region. SSU rRNA-based Bayesian inference and maximum likelihood analyses revealedC. sargusn. sp. positioned separately from other sparid-infectingCeratomyxaspp. reported from Southern European countries, demonstrating that this species does not share a more immediate common ancestor with its closest relatives based on host affinity and geography. The recognition of a novel sparid-infecting lineage within theCeratomyxaclade strengthens the contention that this genus entered sparid fish multiple times, namely in the Southern European region. The identification ofZschokkella auratisinfections inD. sargusdemonstrates that host shift has occurred among sparids reared in the Southern Portuguese coast. This agrees with the broad host specificity that is usually attributed to this genus, and that may be suggested to be the outcome of the capacity of theZschokkellamorphotype to undergo host shift/switch based on our findings and the limited molecular data available for this genus. Thus, a better understanding ofZschokkellahost-associated diversification and dispersal mechanisms requires the increasing availability of molecular data from infections of the same species occurring in multiple hosts and geographical locations.