10: feral platies (Austria)

[illustrator]

OK, I am going somewhat off-topic here. This is hardly about cichlids. I caught two platies in the Austrian stream (see other topic, the same stream where there are populations of convict- and jewel cichlids). I opened this topic in order to document what I learn about these platies, please feel free to skip the topic if you feel that it's not interesting.

Male platy, caught downstream in the Austrian stream. Note the black patch at the tail-fin-base: swordtail-genes?

Female platy, caught downstream in the Austrian stream

[illustrator]

I caught the pair on 11 november 2008. The male then looked like this (below). Note that since then it has become much darker. I wonder if these platies represet a small feral population, or are just "recently released fish". I am aware that it will be difficult to answer this question, for now I will write the bits and pieces of information that i have.

male platy just after capture, note the damaged tail.

[illustrator]

Since I have only 1 female, it is possible to record the birth-interval

On the 23rd of december I saw the first young of this pair (4 initially survived, now 3 left), I believe that these are the first young of this female. When I caught her she was rather small (about the size of the male, less than 2 cm).

On 6 January I noticed a single young, which looked newborn (survived for some days)

and then, on 18 January I noticed another 3-4 newborn platies (6 survivers, but I have difficulties counting them because they are usually hidden in the vegetation).

edit: on 9 February I witnessed the birth of the next litter (6 seen, probably have been more)

edit: next litter: 7 March

The water temperature is about 26'C. Note that these seem to be small litters, but the mother could have eaten some (other fish in the aquarium: some half-grown guppies, Corydoras paleatus and Ancistrus "sp3"). This is a much shorter interval than 1 month (1 month is usually mentioned in literature). I suspect superfoetation, but is this known from platys???

After giving birth the female looks pretty much equally round as before, which makes me suspect that the litters are really this small.

The young look uniform pale brown at birth, time will tell which colour they will have later on.

Edit (13 March): I have very poor survival rates in the young, from the first litters I have only 3 males left. Lowered the temperature to 24'C.

[illustrator]

The situation with platys is complex. At a previous visit I observed platys in an artificial pond, which is fed with spring-water. I suspect that this pond overflows to the stream, but the platys are very different looking. They are yellowish, some have have the wagtail character (black fins), some have black spots and some have a reddish tail-base (or a combination of these characters). I think these should be seen as "kept in captivity" and not as "feral". Photos from 10 September 2007:

On the same day I observed two "brownish ones" downstream, which I could not catch. I am not sure, but they could have been blue-black-sided and they could have been simlar to the ones from the first photographs. The downstream fish are the platys that I am most interested in, but this information would not be complete without these "upstream photos".

[illustrator]

To make it eve more confusing: I caught (and released) these fish on 11 January 2007, roughly in the middle between the spring and the downstream location.

Blue wagtail: could have come straight from a petshop. I caught two females that looked like this.

Clearly a swordtail x platy hybrid, because of the conspicuous colour I suspect that it would't survive long, even in this strange stream.

[Lisachromis]

I posted this thread on the ALA forum. Maybe someone there will come and explain.

[Lisachromis]

From Darrell E Mefford:

I'm not going to register on another forum,
but I can give you an idea of what these Platies are.
Since Xiphophorus are native to Central America and he caught
these fish in Austria, we know that they were released.
They both appear to have Blue body and Red dorsal. The male
has a Tuxedo pattern and the female has "Striped sides".
He wonders if the tail marking is from Swordtail influence, not
really since "Bottom line tail" is a trait found on some Wild Platies.
Of course since they are probably desendants of Domestic Platy
stock, they probably have some Swordtail heritage.
I'm not for sure what Flashy Trade Name these fish carry.

[illustrator]

Thanks!

Direct link to ALA:

http://livebearers.org/modules.php?name ... ht=austria

I like to add a note that the male looks stripe-sided on the "younger" photo, at least to me. I agree that now he appears to have the tuxedo-pattern. Could a platy express both patterns at the same time (which would explain why he seems to have developed from stripe-sided to tuxedo)? Very interesting that this black dot in the lower tail fin does not have to indicate hybridisation.

[illustrator]

Something else: juvenile platies kept disappearing in my aquarium. For some time I was puzzled about this, but I think I got the point now. It appears like these platies are sensitive to large water changes, which go together with a drop in temperature of 5 degrees or more. I do these water changes not only to get rid of nitrate/nitrite, but especially because they work stimulating on Corydoras paleatus, which I have in the same aquarium. In the past I had X. variatus - platies, which are not very cold sensitive and never showed problems with such temperature drops. These Austrian platies are X. maculatus, and are obviously more sensitive: a day after a water change I noticed some having the "oldfashioned shimmies" (general term for a livebearer that is terminally ill and swims around with squeezed fins and wiggles during swimming). With a 5 mm platy there is not much one can do. So the lesson is: change less water, more often, and avoid temperature shocks this way.

[illustrator]

On 24 April I re-visited the stream. One of my goals was to try to find more platies, in order to see if all look simlar (which could indicate either an established population or introductions of a single aquarium strain only). As before it was diffucult to find any platies at all. In the end I caught two juveniles: a very non-descript male and a yellow micky-mouse female. These are rather different to the ones I caught before, but they could fit with the "artificial basin-platies". The basin itself is restorated completely and there are currently no fish in it. So this "source" of platies is currently not there.

I am still not sure if there is really a population of platies in the stream. Even though I caught a few platies on every visit to the stream, they are all very different. This gives me the feeling that I keep catching recently released platies from various sources, rather than representatives of a small population ...

[Csababá]

I enjoyed reading your topic.