Environmental Parasitology: intestinal helminth parasites of the siganid fish Siganus rivulatus as bioindicators for trace metal pollution in the Red Sea

Abstract

Studies on host-parasite systems as bioindicators for monitoring trace metal pollution in marine environments are still scarce. Here, 11, 14 and 17 infrapopulations of Gyliauchen volubilis (Trematoda: Digenea), Procamallanus elatensis (Nematoda) and Sclerocollum rubrimaris (Acanthocephala), respectively, were collected from the fish Siganus rivulatus (Siganidae) in the Red Sea, from a chronically polluted small bay at Sharm El-Sheikh, South Sinai, Egypt. Water and sediment samples from the bay, tissue samples (intestines, liver, and muscle) from each fish, and samples from each parasite were taken for heavy metal analyses of cadmium and lead. Cadmium concentrations in intestines, liver and muscle of non-infected and infected fishes were much lower than those of lead, and both metal concentrations decreased in the order: liver > intestines > muscle. Cadmium and lead concentrations in the tissues of fishes infected with G. volubilis or P. elatensis were slightly lower than those in non-infected ones, while in the tissues of fishes infected with Sc. rubrimaris, they were much lower. Low concentrations of cadmium and lead in G. volubilis and P. elatensis are associated with their limited ability or capacity to accumulate trace metals. Therefore, bioconcentration factors corresponding to these species were relatively low, and both are herein considered as weak bioindicators. By contrast, high concentrations of cadmium and lead in S. rubrimaris are associated with its high ability to accumulate trace metals. Of the present three host-parasite systems, only the Siganus rivulatus-Sclerocollum rubrimaris system seems to be promising for biomonitoring of metal pollution in the Red Sea.

Figure 1

The relationships between metal concentrations in fish intestines and their concentrations in intestinal helminth parasites: (A) Cd concentrations in fish intestines vs. concentrations in G. volubilis; (B) Pb concentrations in fish intestines vs. concentrations in G. volubilis; (C) Cd concentrations in fish intestines vs. concentrations in P. elatensis; (D) Pb concentrations in fish intestines vs. concentrations in P. elatensis; (E) Cd concentrations in fish intestines vs. concentrations in S. rubrimaris; and (F) Pb concentrations in fish intestines vs. concentrations in S. rubrimaris.

Figure 2

The relationships between metal concentrations in the intestines of infected fish and parasite infrapopulation size in its intestines. (A) Cd concentrations in fish intestines vs. G. volubilis infrapopulation size; (B) Pb concentrations in fish intestines vs. G. volubilis infrapopulation size; (C) Cd concentrations in fish intestines vs. P. elatensis infrapopulation size; (D) Pb concentrations in fish intestines vs. P. elatensis infrapopulation size; (E) Cd concentrations in fish intestines vs. S. rubrimaris infrapopulation size; and (F) Pb concentrations in fish intestines vs. S. rubrimaris infrapopulation size.

Figure 3

The relationships between metal concentrations in parasites and infrapopulation size in fish intestines: (A) Cd concentrations in G. volubilis vs. infrapopulation size; and (B) Pb concentrations in G. volubilis vs. infrapopulation size; (C) Cd concentrations in P. elatensis vs. infrapopulation size; (D) Pb concentrations in P. elatensis vs. infrapopulation size; (E) Cd concentrations in S. rubrimaris vs. infrapopulation size; and (F) Pb concentrations in S. rubrimaris vs. infrapopulation size.