First observation of intersex in Trachurus trachurus (Carangidae) from the Eastern Coast of Algeria: are nematodes the causative factor?
Intersexuality was reported at macroscopic and microscopic levels in horse mackerel, Trachurus trachurus (Linnaeus, 1758) from Algerian coast. Macroscopically, intersex specimens were characterized by the simultaneous presence of both male and female gonads. Gonads were typical ovaries with a testicular component embedded in one of the two ovaries. Histological analysis revealed the simultaneous presence of female and male germ cells. Intersex was also observed, but exclusively at microscopic level, in normal females with no macroscopic intersex. In these specimens, histological sections showed a predominance of female tissue with oocytes at different developmental stages. Male tissue was characterized by seminiferous tubule-like structures with a predominance of spermatogonia compared to spermatocytes and spermatids. No mature spermatozoa were observed. No intersex was observed in males. The observed intersex was considered as masculinisation. The parasitic analysis revealed the presence of both Nematoda and Digenea with P = 31.20%, mI = 2.59 per fish and mA = 0.80, and P = 13.15%, mI = 1.51 per fish and mA = 0.19, respectively. The factors inducing intersex remain unknown; however, the results showed that 100% of intersex females presented a parasitic infestation by Nematoda highlighting the probable impact of these parasites as a causative factor, probably through pollution concentration