Seasonal fluctuations in the incidence of epidermal papillomas of the European eel Anguilla anguilla L.

• Published in: Journal of Fish Biology
• Main Author: Peters, Gabriele
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1975
• Subjects: Anguilla anguilla
• Online Access: http://dx.doi.org/10.1111/j.1095-8649.1975.tb04617.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1095-8649.1975.tb04617.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1095-8649.1975.tb04617.x

The eels of the Lower Elbe (15–35 cm total length, freshwater age groups III–V) show a high incidence of epidermal papillomas. These neoplasms, situated mainly in the snout region, show a marked seasonal fluctuation. The incidence is low in spring and autumn (min. 2–3 %) and rises sharply in summer (max. 28 %). The size of the papillomas is also smaller during the colder seasons of the year (up to 300 mm 3 ) reaching a maximum in August/ September (up to 900 mm 3 ). The increase in growth of the tumours follows the rise in frequency with a delay of 3–4 weeks. These seasonal fluctuations of tumour growth are possibly related to the alteration of the water temperature and oxygen content.