Occurrence of Conchophthirus acuminatus (Protista: Ciliophora) in Dreissena polymorpha (Mollusca: Bivalvia) along the River Shannon, Ireland

Abstract

Samples of Dreissena polymorpha were collected at several sites along the River Shannon navigation in Ireland, to determine the occurrence and distribution of their obligate host-specific commensalistic ciliate, Conchophthirus acuminatus, in this newly invaded region. Mussels collected by various methods were fixed immediately in 75% ethanol, in which they were later dissected under a stereoscopic microscope, beginning with thorough flushing of the mantle cavity and removal of the gills. One ml of sediment flushed from the mantle cavity and dissection residue of each mussel was examined under a compound light microscope using brightfield, phase-contrast, and differential-interference-contrast optics. Of 180 mussels examined, 125 (69.44%) harbored C. acuminatus. The ciliates were invariably well fixed and easily identifiable in all preparations. Mean sampling intensity for infected mussels was 8.47 ciliates per ml of sediment. Both prevalence and sampling intensity varied between sites, but no pattern was discernible. The present results are consistent with other reports of C. acuminatus being the most widespread and abundant symbiont of D. polymorpha throughout Europe, often occurring where no other symbionts occur. Its occurrence in Ireland indicates introduction of the mussels as adults, since planktonic veliger larvae are not known to harbor ciliates. Following similar reasoning, it is possible that the earlier North American invasion by D. polymorpha included only veligers, since C. acuminatus has not been found on that continent. Using these simple and quick methods, the ciliates could be easily identified and counted to give general comparative data among sites regarding intensity and prevalence. Thus, this method has promise for future efforts to obtain basic information rapidly in newly invaded systems.

Findings on three endocommensal scuticociliates (Protista, Ciliophora) from freshwater mollusks, including their morphology and molecular phylogeny with descriptions of two new species

“…They probably feed on epithelial cells shed by their host. Conchophthirus species are widely distributed and have been detected in many countries in Asia (Deshmukh et al 2011 ; Kahl 1931 ; Uyemura 1935 ), Europe (Burlakova et al 1998 , 2006 ; Chuševė et al 2012 ; Conn et al 2008 ; Dobrzańska 1958 ; Fenchel 1965 , 1966 ; Fokin et al 2003 ; Karatayev and Burlakova 2022 ; Karatayev et al 2000a , b , 2007 ; Laruelle et al 1999 ; Mastitsky 2012 ; Mastitsky et al 2008 ; Mermod 1914 ; Molloy et al 2010 ; Raabe 1933 , 1934 , 1950 , 1966 , 1971 ; Zhang and Vďačný 2024 ) and North America (Antipa and Hatzidimitriou 1981 ; Antipa and Small 1971a , b ; Antipa et al 2020 ; Kidder 1934 ; Laruelle et al 2002 ; Penn 1958 ). In addition, Conchophthirus species inhabit a diverse array of freshwater bivalve groups.…”

First record of metacercariae trematodes Opisthioglyphe ranae (Digenea: Telorchiidae) and Echinostoma bolschewense (Digenea: Echinostomatidae) in Dreissena polymorpha (Bivalvia: Dreissenidae) from the Don and Volga river basins, Russia

“…Parasites, commensals, and other symbionts of dreissenids are currently being actively studied (Mastitsky 2004;Stunžėnas et al 2004;Burlakova et al 2006;Conn et al 2008;Molloy et al 2010;Petkevičiūtė et al 2015;Travina et al 2019Travina et al , 2021. Among parasites and commensals associated with zebra mussels, at least seven genera of trematodes are known: Bucephalus Baer, 1827 (Digenea: Bucephalidae), Phyllodistomum Braun, 1899 (Digenea: Gorgoderidae), Echinoparyphium Dietz, 1909and Echinostoma Rudolphi, 1809(Digenea: Echinostomatidae), Sanguinicola Plehn, 1905, Leucochloridiomorpha Carus, 1835 (Digenea: Brachylaemidae), metacercariae belonging to the Plagiorchiidae Lühe, 1901 (Digenea), and Aspidogaster von Baer, 1826 (Aspidogastrea: Aspidogastridae).…”

Factors at multiple scales drive parasite community structure

“…The two species were not mixed at any point once being removed from the river. Exploratory dissection on both ethanolstored and live mussels showed that the storage of mussels in ethanol prior to analysis did not affect the detection of any parasites in the study, and it has previously been shown as an effective way of sampling mussel parasites (Conn et al, 2008). As we only sampled non-threatened non-cephalised invertebrates, no ethical approval was required.…”