XFins-Artificial Insemination
Artificial insemination (AI) of livebearing fishes is the collection of sperm and its introduction into a fertile female by artificial means. The advantages of using AI are numerous including:
- 1. Determination of male fertility;
- 2. Use of lyretail males as breeders;
- 3. Use of non-aggressive males as breeders;
- 4. Full time breeding of females; and
- 5. Interspecies hybridization.
Various procedures for AI are available on the web. My original procedure is published ("Artificial Insemination of Fishes", Livebearers: Bulletin of the
ALA, #27, 1976. ). It is obviously quite old and I will try to provide an updated procedure at some point. The most important difference between my methodology and that of others is that I do not anesthetize the male nor the female during the procedure.
AI Images
In my original procedure, I used drawn out Pasteur pipettes to collect and deposit the sperm. I still use a pipet to collect the sperm, but I now deposit the sperm with a manual pipettor. The images shown here were taken in the early 1970's. Please forgive the quality of the images and my dirty fingernails.
A lyretail male is positioned on his back in a wet net.
The gonopodium is rotated several times and will then be positioned toward the front of the body (not shown here).
The abdomen is gently stroked starting from the head and the sperm packets collected.
The sperm packets are deposited on a glass slide.
Active sperm is stored in packets in the male testis. Upon insemination, these packets are stored in the female urogenital tract, often for many months. Following an appropriate signal (e.g. the female giving birth?), a new set of sperm packets release active sperm to fertilize the next set of eggs.
Sperm packets retrieved from the male will also release active sperm when the salt concentration is increased (to 0.7% NaCl). This process can be observed under the microscope, but it also can be seen by the naked eye.
A microscopic image of a sperm packet remaining intact under low salt conditions
A microscopic image of active sperm released from a sperm packet after the addition of salt.
Under low salt conditions the sperm packets can be seen by the naked eye as small, white "specks" on a clear background (not readily apparent here). When salt is added the packets break down, active sperm is released and the solution becomes uniformly cloudy.
The female is positioned on her back in a wet net.
Active sperm is injected into the females urogenital opening located between the anal fin and the anal opening. It is difficult to see here, but the solution in the pipet is not cloudy as it should be.
In my experience, AI is most successful when used within 18 hours of a female giving birth. In most cases, the vast majority of offspring are from the desired male, but this is not always the case. One tank raised wild X. helleri female gave birth to four broods of offspring exclusively derived from stored sperm rather than from the AI-delivered sperm. AI also works with virgin females, but not nearly as well.
