Teratoma is a rare tumour in fish consisting of tissues from more than one germ layer, that may be located in either the gonads or extragonadal sites. Teratomas in many fish species remain poorly understood. In this work, we performed the first histological examinations of extragonadal teratomas in Poecilia wingei and also examined the influence of a large teratoma on male sexual activity. The studied teratomas shared general organizational features, but they also had variations in both external and internal features. In teratomas, the most common and highly differentiated tissues were striated muscle and nervous tissue. Despite the tumour, the male P. wingei exhibited normal mating behaviour and retained the ability for successful copulation. The structural features of extragonadal teratomas in guppy fish indicate a possible connection between these tumours and a failure of conserved processes operating in the embryonic germline.
Keywords: histology; neoplasia; tumour; viviparous fish.
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