Caption: Sexing and BreedingPseudogastromyzon cheni. Article Header.
Credit: Martin Thoene
Pseudogastromyzon cheni will breed regularly in aquaria if given the correct conditions. Sexing them is quite easy once you know what you're looking for.
Caption: Sexing P. cheni.
Credit: Martin Thoene
You'll note that the female's belly is noticeably more full than the male's. It is convex and reflects the light back from it's centre. The female is broader in the belly at the point just behind the Pectoral fin rear origin.
Look at the nose of the fish. Sexually active male cheni have nasal tubercules increased in size. See them either side of the nose? Compare with the female. Females have very much smaller tubercules which do not increase in size when sexually mature. From underneath, you can only just see one pair.
A male looks like this:
Caption: A male looks like this
Credit: Martin Thoene
A more extreme picture, modified to clearly show the formidable tubercules which the males use to butt one another to assert dominance.
Caption: P. cheni male, black and white tubercule picture.
Credit: Martin Thoene
A female looks like this:
Caption: A female llooks ike this
Credit: Martin Thoene
Compare.....the upper fish is the dominant male in the tank....
Caption: Compare.....the upper fish is the dominant male in the tank
Credit: Martin Thoene
The other fish looks like a subordinate male. You can see it has tubercules, but they are somewhat smaller than the other fish. Females generally have a higher arch to the top profile of the body and are more full-bodied.
A male side on is pretty streamlined............
Caption: A male side on is pretty streamlined
Credit: Martin Thoene
Note this one has much reduced contrast between the light and dark body colours (see difference in dominant male above).
Females are generally this low contrast colour.
Note back contour..........
Caption: Note back contour
Credit: Martin Thoene
The good news is that P. cheni are pretty good at working out who is who themselves. P.cheni courtship consists of the male dancing around the chosen female (often on the aquarium glass) and generally following her around. At some point the male will get accepted by her and then she will tend to follow him around.
Two fish squaring up to one another and trying to get on top of one another are generally males in territorial dispute. At these times colours will be intensified and may change to what we term "war paint". The upper area darkens and the sides go paler than normal. Males will raise their colourful dorsals as a display.......
Caption: Cheni Males fighting
Credit: Martin Thoene
The dominant male will tend to be the one breeding in a tank where you have several. He will dig a pit under a stone by sliding backwards off it and whooshing substrate away with his tail.......
Caption: Male digging spawning pit.
Credit: Martin Thoene
The male and female then take turns in sliding backwards into the hole and eggs are layed and fertilized. The male then covers up the eggs. Several pits may be dug, but generally it appears they choose one only.
The eggs are quite large......
Caption: P. cheni eggs buried in gravel.
Credit: Jim Powers
After around 14 days, tiny babies will emerge from the gravel. At that time they are just under 1/4" in length and will begin grazing on microorganisms on the tank surfaces........
Caption: Three Baby P. cheni.
Credit: Martin Thoene
Here is a 7 day old fry with a larger one from a previous spawn that is around 3 weeks old.
Caption: 7 day and 3 week old P.cheni fry.
Credit: LES
Gradually, the plain coloured fry gain colour and markings. Younger fish to right.........
Caption: Fry colouring up.
Credit: LES
They grow quickly. At around 3/8" they have a prominent caudal peduncle eye spot, probably to confuse predators.
Caption: 6mm baby.
Credit: Martin Thoene
Busy little babies grazing over rockwork..........
Caption: Baby P. cheni grazing on rock.
Credit: Martin Thoene
The fry will reach 1" in length in around 4-5 months and grow to about 1.75" in the first year. They seem to become sexually mature at around 6 months of age.
Observe your fish daily. Get to know their habits. If you look for the clues, you may realize the behaviour you see is either fighting or courtship. If it's the latter and there are no other fish in the tank which might predate on tiny babies, there's a good chance they might breed successfuly.
Martin Thoene.
Resistance is futile. You will be assimilated.
