Tuesday, April 08, 2008

Sexing the Clown Loaches

Mitchell McKenzie from Pintius has discovered a new and novel way to sex the clown loaches. Below is the some of the information as provided by him. Many thanks to Mictchell for sharing this exciting development with the community.

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.

Scientific Experiment:

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

2. The specimen has an adequate levels of testosterone. Since testosterone is a hormone which is present largest in males rather than females and male sexual maturity is a measure of testosterone levels, a fish that secrete any measurable levels of testosterone into the surrounding waters would be sufficient to indicate maturity. #

As a test, a sample was taken from one of the tubercles to prove that the testosterone was coming from the specific individual. Taking a sample from the water would be just as good.
To conclude that the specimen in question is a male, any of the male hormones*, not just testosterone would has to be present. A false positive would be given if there are other males of different species present. So ideally for the test, specimen should be isolated in water. Similarly, progesterone and estrogen would be present in female subjects.

* Collectively known as androgens, the male hormones also include dihydrotestosterone, and interstitial cell stimulating hormone, both would also be present in samples containing males.

Based on the test results, the author concluded that the presence of tubercles is good enough evidence that the specimen in question is a male.

All photos are copyright and given permission to republish by Mitchell McKenzie (Pintius). Please contact him at pintius5@aol.com
should you desire to reproduce the image at your site.

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