Very old

bellottii alevins (2017)This alevin is an Austrolebias bellottii Maschwitz that hatched from peat collected in July 2013, outdoors in the vegetable garden. There we only two of them that hatched from this peat this Wednesday (April 19, 2017), but they are nearly four years “old”. Swimming well and eating allright.


Evolutionary rates AustrolebiasThis week I posted a manuscript on bioRxiv. Here is the link to it:

“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.





Floral foam

A. wolterstorffi floral foamA 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.

A. wolterstorffi embryoThis 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.

Photographing eggs

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.

wolterstorffi egg (UV)wolterstorffi egg (IR)




1000 islands

Filter plant islandTo 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.

New tricks

Austrolebias prognathus (Salamanca)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.

Austrolebias charrua

Austrolebias charrua (Los Naranjales)This afternoon I made pictures of one male and three females of Austrolebias charrua (Los Naranjales). They’ve been outside for almost three months now, and I’m happy to see they do well. Charrua is a real beauty and always a pleasure to find in your net in the field. There is quite a bit of colour variation, even between different generations of the same line. The flanks can be gold or grey, it is unclear to me what would cause that. Females can vary quite a bit in colour pattern, even on the fins. It often happens that I mistake a female for a young male.

Feed the small

For a while I try to raise small fish without much Artemia. It decays when not eaten, it can feed predators of the fry. I’m down to two to three feedings of Artemia now, without much mortality. From day one, I add a mix of living invertebrates to the tanks, as in the video. Chaoborus larvae are removed from the mix, large Culex as well. The tank gets some tap water so that the water does not remain too soft and abundant java moss. Per day, some extra (rain) water is added and food if necessary. For this extensive setup, population density is critical: the tank surface per individual should be some 100 square centimeter. So for really large groups, I need to switch back to an intensive setup with water changes etcetera.