New nephron development in fish from polluted waters: a possible biomarker

Area of Science:

• Environmental toxicology
• Aquatic ecotoxicology
• Fish renal physiology

Background:

• Fish possess the capacity for nephrogenesis (new nephron development) after kidney injury.
• Quantifying new nephron formation in adult fish offers a potential ecotoxicological assessment tool.

Purpose of the Study:

• To evaluate the utility of quantifying developing nephrons in mature fish as an ecotoxicological assessment tool.
• To investigate the relationship between environmental contamination and nephron development in fish kidneys.

Main Methods:

• Histological kidney sections were prepared from Atlantic tomcod and brown bullhead.
• Specimens were collected from reference and contaminated streams.
• Image analysis quantified developing nephrons and basophilic cell clusters per section area.

Main Results:

• Tomcod exhibited one to two orders of magnitude higher numbers of basophilic clusters and developing nephrons than brown bullhead.
• Elevated numbers of developing nephrons and basophilic clusters were observed in tomcod from the Hudson River compared to reference rivers.
• Seasonal analysis revealed elevated basophilic clusters and developing nephrons in bullheads from the Cuyahoga River compared to less-contaminated sites.

Conclusions:

• Developing nephrons and basophilic clusters show potential as general indicators of ecological condition in fish.
• These markers may be particularly suited for detecting site-specific nephrotoxicity in aquatic environments.
• Further research is warranted to validate their use as a broad ecotoxicological assessment tool.