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In the early 1840's, the famous botanist Karl Heller traveled to Mexico on a plant collecting expedition. When he returned to Europe he brought with him some strange and beautiful fish specimens. Eventually, these fish were called Xiphophorus helleri, literally, “Heller’s sword bearer”. For some time I had been hoping to acquire a pair of Green Xiphophorus helleri but they never seemed available at the club auctions. Then last November I saw a pair of fish that seemed to equal the beauty and majesty of the Green Swords – they were a healthy pair of Neon Swordtails. The body of the Neon Sword is mostly a soft, glowing orange with a striking reddish-purple slightly zigzagging midline that extends from the pectoral fins to the tail. The midline is set against a background of iridescent greens, blues, and reds. As they energetically swim around the aquarium their glistening body colours seems to dance in the glow of the light. They are truly a beautiful fish. The pair I bought was healthy and active. The male was 2.5” in length, closer to 4” including the tail, and the female was about 3”. She had a nice round belly. While I assumed she might be pregnant, I had no idea of how pregnant she was. I was soon to find out. I placed my new acquisitions in a bare ten gallon tank with a corner filter. The water temperature was steady at 78 degrees F. The pH was about 8 and the hardness about 10. During the next few days I added a few plastic floating plants for cover. The first Saturday I had the fish home (November 20th) I noticed a few fry floating at the water line along the sides of the tank. I quickly removed them to an adjacent 10 gallon tank. Everything I had read about the Swordtails told me that good sized females are able to drop dozens of fry, so I was surprised when my female Neon only had four babies. Almost exactly four weeks later (Dec. 22) there was a second drop; this time there were three babies. I began to get suspicious. After all, this female sword was a healthy fish and sported a good length and depth. About three weeks later, I decided to remove the male, figuring that he’d probably already done his fertility work. On January 22nd, a third group of fry were born, but this time there were 29! It seems clear to me now that the female was probably having good fry drops each time, but that the male was engorging himself enjoying swordtail sushi. I decided to keep the male and female apart since I had 36 fry, all of which seemed to be doing well. Then, a month later, on Feb. 23, something most amazing occurred. There was another drop, this time of 15 babies. As a Religion teacher in a Catholic School I was familiar with the doctrine of the Virginal Conception, but I certainly never expected to see it in the fish hobby. I decided to do some investigation. It turns out that some fish have an ability called superfoetation which allows females to store sperm for future fertilizations after mating with a single male. This process continued in my aquarium, with a fifth batch of 18 fry dropped on Mar. 22nd and a sixth group of 10 fry born about a month later on April 21st. It seemed that the drops occurred about four weeks apart and that the number of fry decreased with each subsequent birth. This technique is surely a helpful way for the Swordtail to increase its progeny. I fed the fry microworms for the first week, and then changed to baby brine shrimp. As they got larger, I added some Tetra and Nutra Fin Flakes into their diet. They really relished the baby brine shrimp, even as adults. The fry grow quickly. When they are born, they are probably about ¼” in size. At a month to six weeks they are in the ½” range. At 3 months, one begins to see an orange tint on the back and the dorsal and anal fins. By 4 months, many are 5/8" long and one clearly sees the fluorescent body tint. At this stage I also noticed perch-like vertical bars along the sides of the body. These disappear over time. At five months many fish are close to an inch long; the midline is clearly visible. At the six month mark I noticed that one of the fish from the first batch was developing the elongated anal fin or gonopodium of the male. Prior to this point it was not possible for me to differentiate males from females (although I’m sure experienced fish keepers would be able to tell long before this point). One week later I noticed a slight sword extension beginning to develop on the male’s tail. By 7 months, this tail would measure almost one inch in length. At different times I’ve noticed male swords engage in what I would call “sparring behaviour”. Two males will back up toward each other in an apparent display of their swords. Sometimes one of the males will back off with his dorsal fin down; if not, sometimes the males will go at each other head first. My assumption is that this often aggressive behaviour is establishing a hierarchy of dominance, but I’m not certain. If you want a beautiful addition to your community aquarium or fish room, one that is easy to maintain, one that breeds almost miraculously, then you should look no further than the Neon Swordtail. They are a pleasure to behold.
Article Source: http://www.articlefishtalk.com
David Fischer (reprinted from the September 2005 issue of 'tank talk') www.dras.ca
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