Postojna Cave Park

The female suddenly left the eggs where they were and moved to the other end of the aquarium. We thought she was having a rest, but when we had a closer look, we saw that she had laid another egg. Our two biologists are still wondering why she had withdrawn to this other spot; it was noticeable there were at least 3 more eggs left in the abdominal part of the olm’s body. Perhaps this was natural behaviour aiming to give the eggs divided into two different places a greater chance of survival, but it is impossible to say with certainty, as the olm has never before been exposed to being studied in such a way. 

After a three days’ rest, the female returned to where the majority of eggs were, but now she is in a different position and seems much calmer. She is not checking on the eggs as often as during the first month, but is lying around most of the time. This is something new we have learnt about the olms, and most likely an indication of how exhausting laying eggs in a dark and cold environment and the constant scaring away of the amphipods are for olms, which, on average, only reproduce once in a decade. With everything she has been doing so far, the female olm is challenging our knowledge of olms, as previously it was believed that the egg-laying period lasts about 3 weeks, whereas in Postojna Cave it has this time been going on for almost two months.

While we are keeping a close eye on the olm, we are also just as closely watching the embryos’ development, which you can see for yourself on the picture. The top egg, which was laid at an earlier time, already shows the beginnings of the head, back and tail. The bottom egg, which was laid at a later time, is currently in the division stage. This egg is the most recent egg and has so far shown no changes.

Judging by everything we have learnt so far, the time when we get to see the “dragon’s offspring” is not far-off. However, it is also becoming
increasingly obvious that we do not know all that much about the mysterious life of olms. Our olm mum is making sure miracles are happening time and again, leaving us speechless and aware of the fact how little is known about the olms’ life. We are profoundly grateful for this and for everything new she is teaching us about her life.

 

Olm Diary