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. 2022 Apr 26;11(5):663.
doi: 10.3390/biology11050663.

Parasitic Load, Hematological Parameters, and Trace Elements Accumulation in the Lesser Spotted Dogfish Scyliorhinus canicula from the Central Tyrrhenian Sea

Francesca Romana Reinero  1   2 , Concetta Milazzo  1 , Marco Minervino  1 , Cristian Marchio  1 , Mariacristina Filice  1 , Laura Bevacqua  1 , Gianni Giglio  1 , Francesco Luigi Leonetti  1 , Primo Micarelli  2 , Sandro Tripepi  1 , Donatella Barca  1 , Emilio Sperone  1
Affiliations

Parasitic Load, Hematological Parameters, and Trace Elements Accumulation in the Lesser Spotted Dogfish Scyliorhinus canicula from the Central Tyrrhenian Sea

Francesca Romana Reinero et al. Biology (Basel). .

Abstract

Parasitological, hematological, and ecotoxicological analyses were carried out on a population of lesser spotted dogfish Scyliorhinus canicula from the central Mediterranean Sea. Parasitological analyses highlighted a poor helminthic community, highly dominated by a single taxon represented by the cestode Nybelinia sp. No differences in the parasitic load between females and males were observed. Hematological analyses showed that the number of leukocytes was significantly lower in the sharks that resulted in parasitism, and this could be due to the ability of some trace elements, such as arsenic, weakening the immune system and exposing animals to a higher risk of parasite infection, although further hematological and parasitological analyses are required on a larger number of samples. Trace elements analyses in the vertebrae, skin, and liver highlighted that the most abundant and potentially toxic elements were lead (Pb), arsenic (As), and cadmium (Cd). Other trace elements were also abundant, such as manganese (Mn), zinc (Zn), nickel (Ni), copper (Cu), and iron (Fe). Pb, As, and Mn showed the highest concentrations in vertebrae, while Cd, Cu, and Zn were the highest in the liver, probably due to their concentration in the prey items of the sharks; Fe and Ni showed the highest concentrations in the skin, due to their presence in the water column, especially along the coast where animals were collected. The concentration of some trace elements analyzed in the vertebrae decreased with the growth of the sharks. These results confirm that elasmobranchs, being predators at the apex of the marine food chain, act as final receptors for a series of polluting elements regularly discharged into the sea.

Keywords: Mediterranean; ecotoxicology; elasmobranch; hematology; parasitology; trace elements.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Localization of the sampling area. The white triangle indicates the fishing area of the samples.
Figure 2
Figure 2
Vertebra of S. canicula showing the two perforations: one close to the center (point A) and one close to the distal part (point C), to analyze the concentration of trace elements in two different stages of the biological cycle of sharks. Circles and arrows indicate the positions of points A and C.
Figure 3
Figure 3
Frequency histogram of the numbers of specimens collected by month and by sex.
Figure 4
Figure 4
Gastrointestinal parasites found in S. canicula in the present study. (A) Nybelinia sp. (Few, 1926), scale bar 0.75 mm; (B) Proleptus obtusus (Dujardin, 1845), scale bar 0.5 mm.
Figure 5
Figure 5
Difference ± sd between leukocyte count (103/μL) and presence/absence of parasites (N of non-parasitized sharks = 25; N of parasitized sharks = 7).
See this image and copyright information in PMC

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