Evidence of trilobed testes in European sardine (Sardina pilchardus)
Abnormal gonads were recorded in male specimens of European sardine, Sardina pilchardus (Walbaum, 1792) captured along the Mediterranean Coast (Northern Spain, Northern Adriatic Sea, and Aegean Sea). Three lobes were identified in the testes of these individuals, what could be considered as gonad segmentation. The prevalence of this abnormality of the testicles’ architecture has reached 2%, 0.99%, and 0.49%, respectively, in the samples of the stocks mentioned above. To knowledge, it is the first documentation of such testicular alteration in this species. Chemical exposure or parasitism have been invoked as plausible hypotheses, although further studies are required to elucidate its cause in this valuable fish resource, since reproductive abnormalities may result in severe implications, including population losses.