engleski

Infection status of Mytilus galloprovincialis (Bivalvia, Mytilidae) with trematode Parvatrema sp. (Digenea, Gymnophallidae) in Kaštela Bay, Adriatic Sea

Species Mytilus galloprovincialis Lamarck, 1819 is a dominant mussel on the rocky intertidal of the Adriatic Sea, Croatia. The beds of M. galloprovincialis were in regression during 2014, but the population recovered. In 2018, a new population decline was recorded. Due to those fluctuations, trematode infection was noticed. Based on morphology and observation of the sporocysts, cercariae and metacercariae in mussel's mantle and gonads, the trematode species is identified as Parvatrema sp. A total of 40 individuals were collected during February and March 2014 and 2018 from the rocks at Kaštel Stari. In the laboratory, the mantle and gonads of each measured mussel were macroscopically and microscopically examined and photographed with Axio Camera MRc5. Trematode morphology was observed and measured using the Axio Vision Release 482SP3 program (08-2013). Mussel tissues with different developmental stages of trematode have been fixed in 4% formaldehyde, and following routine histological procedures, sections have been stained in Ehrlich's haematoxylin and eosin. Based on histology, an infection prevalence (number of infected mussels / total number of mussels) and weighted infestation (infection intensity / total number of mussels) were calculated according to year of sampling, sex and length of mussels. Results showed that the prevalence of infection for 2014 was 100% while in 2018 it was 65%. During both years, there was no significant difference in the prevalence of infection among males and females nor between different shell lengths, presuming high infectious potential. Weighted infestation was not much lower in 2018, indicating that the number of individuals in this population could be reduced again due to new infection. Since the definitive host of Gymnophallids are known to be marine and coastal birds and assuming that in Croatia the relationship between birds and trematode infection has not been reported previously, more attention should be paid to this subject.

Mytilus galloprovincialis ; Parvatrema sp ; trematode ; infection status ; histopathological study

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