Many species, mainly cyprinids, display not only colour changes (sexual dichromatism) during the breeding season but also physical (sexual dimorphism) or anatomical changes. Clown loaches seems to exhibits breeding tubercles during the breeding season. The males form little lumps on their head which are normally only visible when you take a picture of the specimen and zoom in. This was the case for the following male clown loach -
A casual observer might think - ''its ich', but if you look closely, the little dots are on the head only. These are breeding tubercles, found only in males, never females.
The specimen shown is a relatively small chap, who was given levomidizole because of the transportation trip. It is now approximately 7 inches. Normally, this size does not mean sexual maturity. However this little chap most definitely is mature based on the following findings*.
1. Extraction of tubercle from male using ELIZA will reveal moderate levels of testosterone. This is an obvious male hormone which will only be present in males
* Collectively known as androgens, the male hormones also include dihydrotestosterone, and interstitial cell stimulating hormone, both would also be present in samples containing males.
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