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.
“A case for sympatric speciation by cannibalism in South-American annual killifish (Austrolebias)”
We demonstrate that large Austrolebias evolved at least three times from small ones. For one case, we argue that piscivory evolved starting from the evolution of cannibalism on conspecifics.
A new incubation trick: I cut slices from a block of floral foam and push small depressions in them, the size of a coin and about 1 cm deep. These pits are filled with cocopeat, from the container where my killies have been laying eggs. I drip some rainwater on the foam to keep it wet, and I also cut a thin lid. Eat pit gets four fresh eggs on top of the cocopeat, to be incubated. Then the wafer goes into a 250ml plastic container for storage and to avoid desiccation. Here some A. wolterstorffi eggs after one month of storage. The white patch is fungus: I lost one egg out of the four in this pit. As you might notice, the other three contain well-developing embryos. The scratches around the pit are from stabilizing my usb microscope on the foam.
This afternoon I checked a small sample of A. wolterstorffi (Velasquez) eggs, which I photograph regularly. In a few embryos, the developing heads and eyes can be seen. In this egg, the two darkers dots above the yolk droplet are the eyes. USB-camera, near IR light. I also made a short video, where you can see that there is a heartbeat.
Yesterday I colllected Austrolebias wolterstorffi (Velasquez) eggs. I just decided to make some pictures of them, using a DinoLite USB microscope with UV (395nm) and near IR (940nm) leds. Here are the results on a fresh egg (well maybe not from the last few days) that I just put straight from the peat onto a piece of paper on my desk. The result is simple to achieve and really encouraging. So I will try to get pictures of all main developmental stages with this lighting. Left: UV; Right: IR.
To keep tanks clean(er), I decided to use plants that grow well and root well in water as filters. Here on the photograph three different plants on small floating islands in my fish basins, situated in an unheated greenhouse. They all grow through winter. Leftmost: Vietnamese coriander (Persicaria odorata), middle: Japanese parsley (Oenanthe javanica), right: watercress (Nasturtium officinale). What’s really great is that the plants need to be kept growing to make them take up nutrients. What helps well for that is harvesting them, and all three are edible. Aquaponics in its simplest form.
A small A. prognathus (Salamanca), some ten days old. I have been worrying about controlling nitrate and levels of other waste products in my tanks, to maximize juvenile growth of small ambitious fish like this. In some places the tap water is really excellent, in others it’s barely acceptable which makes the level of difficulty to maintain some species very variable. I also start believing that local tap water properties really determine how many people engage in the aquarium hobby and also determine the fish species that do well and are maintained in the killifish community. Wouldn’t it be nice if we could make some things “easy” anywhere?
In many situations, replacing water when it’s almost too late can help of course, but I prefer to be ahead of things, to avoid excessive levels to build up or to “clean” the tap water. So I am moving away from tanks with just some peat on the bottom, and I add zeolite now, just a little, to see how it behaves, what the effects are and if it might help to make raising fish easier everywhere. Plans are to measure lots of tanks and different waste product treatments later, in a situation where I start from dechlorinated tap water. Will be some work: all samples will have to be filtered and frozen before they can all be analysed together.