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3 way swordtail fight | 7 comments (7 topical, editorial, 0 hidden)

We don't realize how territorial swordtails (none / 0) (#1)
by unclescott on Tue Jun 03, 2008 at 01:50:53 PM PST

can be. Often this is because if youngsters or fry have grown up with each other, they have working out a "pecking order" before they were so large as to inflict serious injuries on one another.

Knowing how male swordtails can dance, that must have been quite a display in a 55-gallon tank. And yet, clearly "there's not room enough in this town for both of us."

Interesting that the dominant female swordtail also got into the fray. Several years ago a study was published in the Journal Copeia (Journal of the American Society of Ichthyologists and Herpetologists) detailing population structure and interaction among wild swordtails (Xiphophorus helleri). Often the largest male in an area would be able to sequester the largest female so that she kept company and mated only with him. He in turn chased all of the other pesky males away from her - allowing her to forage more for more food and produce larger and more plentiful fry.

That is clever, you removing that one male so that he could grow larger. I'm disappointed that it didn't work out better. Certainly this has happened when new purchases, especially if the new purchase is LARGER, that their corresponding numbers in an aquarium, is introduced. (Maybe try in the evening. Turn out the lights soon after.)

Sometimes a dominant male swordtail (also in some cases other livebearers or even killifish) will lord it over younger fish. This may keep some males from "sexing out" and showing their adult colors. That may allow those males to grow larger and (ironically) eventually take over the aquarium. Male swordtails pretty much stop growing (though all fish will grow a little for almost all of their lives) when their sword develops. By delaying the development of that sword, a "supermale" may be developed.

That phenomenon has also given rise to the myth of female swordtails developing into males. Almost always, the so-called female was just a large juvenile (Baby Huey?) who just didn't develop his sword for an extra long time.

When a female Poeciliid (the huge group of livebearers, which included guppies, mollies, swordtails, platys, variatus and so many more) begins to develop her gravid area, her ribs actually shorten so that extensible "bag" or gravid area can expand with the increasing number of fry and soon to be fertilized eggs. Aging female Poeciliids, with the hormonal imbalances that may accompany old age, may indeed begin to show some male characteristics (usually color) but even if her anal fin developed into a gonopodium (which is statistically very unlikely) she/he wouldn't have the skeletal rib support to enable the gonopodium to properly work.

Kudos to you Josh for carefully watching the swordtails and getting the losers out of the aquarium. In the wild, they would swim away and go up or downstream. I'm afraid that some of the "crispy critters" found outside of aquariums, were trying to get away from a dominant male or a really annoyed female. Josh knows this, but swordtails are very accomplished jumpers - their very streamlined design makes them natural "sprinters" within or out of the water. Cover swordtails closely.

Re: We don't realize how territorial swordtails (none / 0) (#2)
by josh117 on Mon Jun 16, 2008 at 09:54:09 PM PST

Well the red lyretail swordtail decided to try and become completly dominant, and I really don't get the thing with a "super male" i thought that was when the x chromosome was messed up. But ive actually had a female swordtail drop about 100 fry and then turn into a male but there was no babies for her to be a father to before she died.

[ Parent ]

Are you sure that she was a functional male? (none / 0) (#3)
by unclescott on Thu Jun 19, 2008 at 02:55:34 PM PST

If there were viable females with her/him/it and they had never been exposed to ANY other swordtail male and they never had any fry, that that fish is not a male. If there were no virgin females exclusively with that fish, we can speculate any way we want (sort of like the hot stove discussions over who has been the best pro football running back, who is the best point guard of all time, who is the best left-handed pitcher of all time, what is the best popular song...) There is little that can be done to prove one's assertion.

Ah, except according to John Dawes book
Livebearing Fishes: A Guide to Their Aquarium Care, Biology and Classification, he suggests that female Poeciliids loose the further sections of their rib cages. That makes room for the growing fry.

Those extended sections of the males' ribs connect muscles to the gonopodium and they allow the male (guppy, swordtail, molly, et al) to maneuver the gonopodium so that he can fertilize a female. Even if a female experienced a profound hormonal shift and the anal fin narrowed into something close to a gonopodium (and that begs the question of whether viable sperm was produced), the probability is very great that no females would be inseminated.

Isn't it lyretail swordtail males who are unable to effectively mate with female swordtails? They have the conventional musculature, but the gonopodium is so altered that they are unable to mate with females. In at least one laboratory study, sperm has been withdrawn from a male lyretail sword and was effectively introduced to the eggs of a virgin female lyretail swordtail and she produced fry. How much more difficult would that be for a masculinized female?

It would be interesting if a researcher were to write a grant proposal for experiments with elderly, masculinized female swordtail and then try artificial insemination. Don't know how the writer would justify the expense other than just for the knowledge. "Pure research" of that sort, at a time when the economy is tanking and government and research money is getting scarce, may not get the attention of research with more practical applications.

Whoops! Look at the issues below, you might get your grant!

Sometimes fish born of inter-species crosses will be described as intersexes. That is, they show both male and female characteristics. I don't understand the survival advantage to either parent species because they are usually sterile. (Maybe predators go after - with less common appearance - rather than the parent species.) Aged female fish (guppies among them), who lose the ability to keep a balance of the testosterone and estrogen (among others?) will sometimes display male traits such as extended fin rays and more color.

Ah! Just for fun I Googled Masculinization of female fish. Wow! Got 68,000 hits. Many articles will send you to others!

Pollution has had profound effects on fish. I do now recall an article in the Potomac River systems where black bass have been showing up developing both testes and ovaries. They noted that:

> The discovery has made the South Branch the latest example of an emerging national problem: Hormones, drugs and other man-made pollutants appear to be interfering with the chemical signals that make fish grow and reproduce.

http://www.nanfa.org/archive/nanfa/nanfa-loct04/0172.html

If you can get through the technical terms take a look at the ENVIRONMENTAL TOXICOLOGY article on
Masculinization of Female Mosquitofish in Kraft Mill Effluent-Contaminated Fenholloway River Water Is Associated with Androgen Receptor Agonist Activity.

I don't know if they credit completely masculinized female Gambusia with being able to sire young by inseminating other females. (Earthworms and many small pond snails are able to fertilize each other.) One immediate problem may be that there are so few females downstream from a paper mill that one wonders if there are enough females to carry the next generation.

http://toxsci.oxfordjournals.org/cgi/content/full/62/2/257

The Abstract of an article which was a "Report of a naturally masculinized female of the Clear Creek gambusia, Gambusia heterochir Hubbs" suggested that a masculinized female still carried 11 well-developed, late stage embryos. This suggested that the male looking female could still carry young.

http://www.blackwell-synergy.com/doi/abs/10.1111/j.1095-8649.1986.tb05141.x

It sounds like there are a lot of ramifications for the creatures living in these water and for those drinking them!

A summary of some of this stuff in the UK publication Practical Fishkeeping alluded to
"A seven year experiment on a lake in Ontario showed that chronic exposure to low levels of oestrogenic compounds resulted in the near extinction of these fish in the lake."

http://www.practicalfishkeeping.co.uk/pfk/pages/item.php?news=1608

Lesions on the skin, cancers, birth defects, reproductive anomalies, fish kills and more! Well you have sure opened the door on some interesting but disturbing stuff Josh!

I've impressed with what I don't know. If this is of interest, google topics like intersex fish, pollution and fish gender, feminized fish, maculinized female fish might include some of the areas on might search. Some of those are commercial academic sites, which want to sell you copy of the article. Search for the article itself and often you can find a complete copy of it on-line without having to pay $30 or $40 for it. Sometimes reading through the Abstract will give you what you need to know.

Josh, maybe search for intersex (etc.) and swordtails, Xiphophorus, Poeciliids or livebearers. Who knows where this will lead?

[ Parent ]

Re: Are you sure that she was a functional male? (none / 0) (#4)
by josh117 on Thu Jun 19, 2008 at 09:59:28 PM PST

I was never sure she was functional, i never saw it move, but my lyretail male is constantly trying to breed with my 2 female neons, i thought that livebearers shot the sperm outside of the female like next to the anal fin and only some sperm got in, but thats what brought the idea of trimming his gonopodium to somewhat regular size would hopefully help with, i used to have a male variatus platy that had a gravid spot and always tried to breed with my male red wag swordtail O_o but he eventually died but he did have kids though, 1 regular male and 1 regular female and a hi fin female because the mother was a hi fin blue platy and he was my only variatus, and my only platy because he killed the red wag like 2 months before that, and thats also when i found my miniature green swordtails.

[ Parent ]

The trimming of the extended gonopodium (none / 0) (#5)
by unclescott on Fri Jun 20, 2008 at 07:07:43 AM PST

is an very creative consideration. However each species has a (bad pun) specific shape to the gonopodium, with certain arrangement of fin rays, hooks and angles. Indeed taxonomists use the shape of the gononpodium to determine what species a fish is. And female Poeciliids have a vent, which is designed to only accept the gonopodia of their species. Sometimes, closely related species are able to sometimes cross because of similar gononpodiums. That is why, after a lot of trying in labs, several Xiphophorus (swordtails, platys, variatus and judging by a recent ALA issue of Livebearers even more species recently) have been crossed.

Miniature green swordtails? One of the interesting thing about both wild and domestic swordtails from X. helleri is that they will throw smaller males, who mostly spawn by "sneak spawning" and also throw the larger "super-males". In some cases, especially where there are a lot of efficient predators, the fast maturing smaller males may be essential if the females are to be inseminated and the species will survive. In other circumstances there is a survival advantage to the larger males.

The other thing is that if we crowd the young swords they will not grow as fast. At a certain time, it is almost like there was a timer in each male and they will begin to develop a sword and pretty much stop growing. We have several male swordtails (both because of crowding and just because they were the smaller ones) in a living room 40-gallon with "odd-number" rainbowfish and a four-year-old male butterfly Goodied (Ameca splendens). Back in the swordtail tank, the females get the larger swordtail male. Usually the biggest male swordtail would be the bully in the 40. In that case the Goodied in the 40 is a pretty aggressive fish, but there are so many tank mates, enough space and quite of bit of foliage to shelter in that nobody is dinged up or chewed. I also quite using a feeding ring, allowing food to spread out more - and that spread out the feeding fish too.

Below are some images of various reproductive organs. The last article compares anal fins of the Poeciliid family (or sub-family) and one of the Goodieds. You can see why the Goodieds can more easily cross.

http://labs.eeb.utoronto.ca/rodd/courses.htm

http://www.scielo.sa.cr/scielo.php?pid=S0034-77442002000300032&script=sci_arttext

http://images.google.com/imgres?imgurl=http://www.livingfish.co.uk/livebearers/images/gonopodium.gif &imgrefurl=http://www.livingfish.co.uk/livebearers/whatlive.htm&h=126&w=255&sz=6& ;hl=en&start=26&tbnid=c-PxC6UL77_JXM:&tbnh=55&tbnw=111&prev=/images%3Fq%3Dgonopo dium%26start%3D20%26gbv%3D2%26ndsp%3D20%26hl%3Den%26sa%3DN

[ Parent ]

Re: The trimming of the extended gonopodium (none / 0) (#6)
by josh117 on Fri Jun 20, 2008 at 10:27:16 AM PST

My red wag swordtail died yesterday, he was a father of 30 and soon to be more, but it looks like my poor lyretail will never have kids, and what about the molly, platy cross breed, ive seen a few of those but i se no resemblance in the gonopodiums, and my guppy/molly cross has a very deformed one and has a swim bladder problem to where he sways when he swims, the head of it looks more molly but when you get to the back of the body he has the body of a female guppy with a few small scattered spots, this is a very weird fish, i might try and take pictures of it. Last year i had a big spawn of black swordtails, i had one male live out of the ones i kept and it was a super male because of the green swordtail that i still had, he became bigger than his mom he was very huge. I was also wondering, are we going through an albino koi and black swordtail shortage this year, i cant find them anywhere and they can't get them in for me. well they got 1 albino koi in but it was very small and they were going to charge me $10 for it.

[ Parent ]

Please do take a photo of what you believe to be (none / 0) (#7)
by unclescott on Sat Jun 21, 2008 at 07:05:45 AM PST

the Guppy/molly cross. Can you document who the parents were? Such crosses seem to have happened, but are very rare. Can you demonstrate that that fish is not just the product of two molly strains (or even two molly species) mating?

"what about the molly, platy cross breed, ive seen a few of those". Sigh! I feel like such a mean-spirited cynic asking this, but has anyone else, anywhere in the world, seen such a cross? Ever?

Again, can you document who the parents were? Can you demonstrate that the fish(es) in hand are not a molly x molly or platy x some Xiphophorus product or just a miss-identified fish??

In light of previous discussions, just pulling some fry from a large community of livebearers and christening them a cross of two species does not prove that the fish is/are an actual cross. One must be able to demonstrate that the parents are properly identified and isolated. (Possibly we could work backwards, if we had the capacity to take a tail snipping and analyze the DNA of the possible parental species and the youngsters.) The parents must also breed true, as opposed to producing mystery fry because they had been inseminated by parties unknown at a shop. And before we declare a fry the offspring of two parents, we must be able to eliminate the possibility of any other fish being one of those parents.

When you declared that you were getting guppy X Gambusia crosses, it was noticed that you had breeding pairs of guppies and Gambusia in the same aquarium. Because females of both species were dropping fry in that aquarium doesn't mean that one can claim that one female was dropping both guppy and Gambusia fry.

In some course somewhere, a text's author was talking about how we can drawn false or irrelevant conclusions from data uncritically compared. As an example it was pointed out by someone many years ago that a large urban area might have a number of criminals plying their trade there. It was also noticed that there were a number of ministers in that city. The author somewhat jovially noted that someone had come to the goof-ball conclusion that if there are a number of ministers in an area there would also be a number of law breakers in that area!

That false reasoning overlooks the fact that the urban area might be home to millions of people. Many of those individuals might have largely different life styles and never meet someone or at least get to know others well, who have such different priorities and ways of "making a living."

[ Parent ]

3 way swordtail fight | 7 comments (7 topical, 0 editorial, 0 hidden)

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