Abstract
This study was achieved to investigate the accumulation of some heavy metals included: Cadmium, Lead and Nickel in the tissues (gill, intestine, liver, muscles and skin) of Silurus triostegus Heckel, 1843 (Siluriformes, Siluridae) and its larval stage of the nematode Contracaecum sp. (Rhabditida, Anisakidae). As well as to assess the infection patterns of Contracaecum among S. triostegus specimens which were purchased fresh from the local market in Baghdad. One hundred and nine nematodes specimens in larval stage were recovered from the fish host; the overall prevalence of Contracaecum sp. was 38.6%. The sex of the host was not significantly (P ˃ 0.05) associated with the infection of this nematode. Results showed that the overall mean intensity of Contracaecum sp. was 6.41; mean intensity did not differ significantly (P ˃ 0.05) between the fish sexes.The lead (Pb) was the only element detected in all fish tissues investigated as well as in the parasite, while the cadmium and nickel elements were not detected in all specimens. Skin and muscles of the fish, as well the parasite Contracaecum sp. contained the lowest lead levels compared to other fish tissues (gill, intestine and liver), although no significant differences were noticed among all investigated tissues and the parasite regarding the concentration of Pb.
Highlights
Extreme action in the industrial and agricultural has undoubtedly boosted heavy element concentrations in natural water streams; as a result, determining the amounts of heavy metalsAccumulation of some heavy metals in larvae in fish, especially those which are widely consumed by human, has lately got some attentions
Limited investigations were achieved regarding the accumulation of heavy metals in parasites and their fish hosts in Iraq
Seventeen out of 44 fish specimens (38.6%) were found parasitized with the larval stage of Contracaecum sp. (Pl. 1). This nematode taxa has been previously reported from the Tigris catfish, Silurus triostegus in different parts of Iraq (Abdulkarim and Abdullah, 2010; Al-Moussawi et al, 2018; Mhaisen and Abdul-Ameer, 2021)
Summary
Extreme action in the industrial and agricultural has undoubtedly boosted heavy element concentrations in natural water streams; as a result, determining the amounts of heavy metals. Accumulation of some heavy metals in larvae in fish, especially those which are widely consumed by human, has lately got some attentions. Silurus triostegus (Siluriformes, Siluridae) has been used to identify heavy metal pollution in freshwater environments and can be considered a reliable bioindicator for biomonitoring (Karadede et al, 2004; Rasheed, 2012; Jawad et al, 2020). As seen by various reviews, there has recently been growing attention to the interaction between parasitism and pollution in the aquatic ecosystem (MacKenzie et al, 1995; Aldhamin et al, 2021). Heavy metal concentrations in fish parasites have been discovered to be quite high, primarily in adult acanthocephalan worms, and to a lesser extent in the adult cestodes (Aldhamin et al, 2021). Limited investigations were achieved regarding the accumulation of heavy metals in parasites and their fish hosts in Iraq. The current study was conducted to compare the accumulation of some haevy elements in the different tissues of S. triostegus and in its nematode Contracaecum sp., as well as to investigate the infection patterns of nematode in Tigris catfish
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