Inside the wooden house, there is still fry approaching maturity. They were born a few weeks ago and have been fed once with Artemia, after that with pond invertebrates. Now they will need to overwinter at relatively small sizes and without heating. Critical to make this work seems to be using tanks with a large surface and low depth and to have sufficient thermal mass in the house. When I see a plastic box in a shop, I get the feeling I can predict how many I can raise in there to maturity, just by looking at the surface area. Maybe it’s time now to start experiments on density-dependent growth and survival in my fish.
In the house I also store orchids (Zygopetalum), palm trees (Archontophoenix) and citrus (Yuzu, finger lime) during winter and cuttings of Physalis Peruvian groundcherry.
Adults of A. melanoorus “R5KM399”. I collected them today, November 17, to move them inside into a 40 liter aquarium. The fish have been out since June. In this species, I particularly like the patterns of spots and lines on the fins of the males and the bar through the eyes.The females often have blobs on the flank, variable in size and number.
There are 15 more tanks outside to check and move. No frost foreseen yet.
This guy has made a wrong decision or has just been unlucky. I spotted him while fishing Chaoborus. That isn’t very easy at the moment, due to the layer of Asolla cristata. I try to remove it every week and plan to use it as a soil fertilizer.
Another manuscript out in the open:
“Desiccation plasticity and diapause in the Argentinian pearlfish Austrolebias bellottii”
We (Irma Varela Lasheras and myself) did detailed demographic work on A. bellottii embryos and found that these respond relatively little to being incubated in either water or air with high humidity. The eggs were incubated in multiwell plates, and this allows a very easy follow-up of the embryos, and a good yield of developed embryos. I am happy with the results and they take me all the way back to the start of my PhD thesis, when I read Prof. Michio Hori‘s thesis on Cicindela japonica, in which he did a demographic study of three stages of tiger beetle larvae with graphs similar to the one I show in this post.
A simple trick which seems to work to attract a lot of Culex mosquitos to a tank so that you can feed killifish fry with their larvae developing from the eggs they lay in there, of any age you might need:
Add a small amount of wheat flour and yeast to the (dechlorinated) water of a 80L basin partly shaded. If the mosquitos are around, soon you will even smell how many they are in there. The flour was my idea, the yeast Milan‘s.
This afternoon I wanted to capture some Chaoborus to feed my adults. DIfficult… The amount of rain has been so much the pumps aren’t draining the area enough.
A pair of relatively young Austrolebias vazferreirai (R44km44) from the type locality. They lay very well and are little aggressive. The water in their tank has some clay added and is therefore turbid. Note the dot on the flank in the male and the weaved pattern. Often vazferreirai males look just grey.
I didn’t expect her to be still alive but here she is. A female A. wolterstorffi (Velasquez) that overwintered at temperatures going as low as 4C. A pair of the same population managed to lay eggs all through winter. I lost them in March when the water started warming and I just hatched about fifty of their alevins yesterday.
May and June are for hatching alevins and raising them. I’ve noticed that I keep on getting the same numbers of juveniles for each tank size or type. There are some species effects of course but things are rather predictable, as if their populations are regulated. So I can more or less calculate how much fish I can breed like this per year. The alevins are hatched with rain water after storage at home for at least five months. Then they are fed Artemia once, and a mix of zooplankton after that. I tend to keep them inside for the first two weeks, but I’m thinking of changing that, because I have bigger tanks outside. This is of course not what you should do when you have for example only two alevins of a precious species to save your population. Then put them next to your bed.
There are these embryos that are refusing to hatch. Here such an environmental change denier and an alevin that did hatch (A. elongatus “Gral Conesa”). Our main explanation is that the non-hatcher will do so at another occasion and is just hedging its bets. However, here the hatched alevin suggests another explanation: it is infected by fungus. The unhatched embryo might suffer the same infection, preventing it from continuing the life history while being eaten alive.