Histopathological assessment of liver and gonad pathology in continental slope fish from the northeast Atlantic Ocean

TLDR

The deep‑sea environment accumulates contaminants, and long‑lived, high‑trophic deep‑water fish are prone to exposure and associated pathological changes similar to those seen in shelf species. The study aimed to provide data on liver and gonad pathological changes in several deep‑water fish species to test the hypothesis of contaminant‑induced pathology. Fish were trawled from 700–1400 m in the Bay of Biscay, and liver and gonad tissues were fixed and examined histologically by light microscopy. Histology revealed hepatocellular pleomorphism, ovotestis, and focal cellular alterations in black scabbardfish, focal cellular alterations and a hepatocellular adenoma in orange roughy, and widespread inflammatory and degenerative lesions across all species, confirming that health screening can detect contaminant‑related pathology and possible algal‑toxin effects.

Abstract

The deep-sea environment is a sink for a wide variety of contaminants including heavy metals and organic compounds of anthropogenic origin. Life history traits of many deep-water fish species including longevity and high trophic position may predispose them to contaminant exposure and subsequent induction of pathological changes, including tumour formation. The lack of evidence for this hypothesis prompted this investigation in order to provide data on the presence of pathological changes in the liver and gonads of several deep-water fish species. Fish were obtained from the north east region of the Bay of Biscay (north east Atlantic Ocean) by trawling at depths between 700 and 1400 m. Liver and gonad samples were collected on board ship and fixed for histological processing and subsequent examination by light microscopy. Hepatocellular and nuclear pleomorphism and individual cases of ovotestis and foci of cellular alteration (FCA) were detected in black scabbardfish (Aphanopus carbo). Six cases of FCA were observed in orange roughy (Hoplostethus atlanticus) (n = 50) together with a single case of hepatocellular adenoma. A wide variety of inflammatory and degenerative lesions were found in all species examined. Deep-water fish display a range of pathologies similar to those seen in shelf-sea species used for international monitoring programmes including biological effects of contaminants. This study has confirmed the utility of health screening in deep-water fish for detecting evidence of prior exposure to contaminants and has also gained evidence of pathology potentially associated with exposure to algal toxins.