Ultrasound examinations provide new insights into the reproduction of the olm

Photo: Anne Ipsen

Summary of an article in the "Volksstimme" (in German).

Only recently, Prof Thomas Hildebrandt (Head of the Department of Reproduction Management at the Leibniz-IZW) – together with Australian colleagues – was able to make a genuine new discovery on reproduction in the animal kingdom: They used ultrasound to show that swamp wallabies develop a new embryo before the birth of the previous offspring and thus show parallel pregnancies at different stages of development. Now, together with his colleague Dr Susanne Holtze, Hildebrandt showed previously unknown reproductive mechanisms also in olms: The fertilisation of the eggs of the rare amphibious cave dwellers takes place inside the female olm and the first developmental steps of the embryo occur already in the fallopian tube.

Olms are one of nature's more bizarre ideas. These up to 40 centimetre long amphibians, which belong to the order of caudal amphibians and are related to salamanders, spend their astonishingly long life of sometimes over 70 years in a mixture of larval and adult stages in cave waters. This phenomenon is known as neoteny, which means that larval or juvenile characteristics persist well into sexual maturity and significantly delay ageing processes, also occurs in the axolotl and the naked mole rat. Olms are native to Slovenia and the Dinar Mountains in the Balkans, while individual populations in caves in France and Italy are artificial attempts to colonise them. Also, in the Hermann's Cave in Germany’s Harz Mountains a total of 18 olms were released in the 1930s and 1950s.

This is exactly where the team from the Department of Reproduction Management made the new discovery. They caught three of the olm females and examined their reproductive organs with a special mobile ultrasound device. “The first female had an inactive ovary, so she probably laid eggs before the examination. The second one was right in the middle of laying her eggs. In the highly active fallopian tubes we discovered eggs in a dimension we had never found before and an internal structure that suggests that embryonic development began here,” Hildebrandt told the local newspaper Volksstimme. This now shows for the first time that fertilisation already takes place inside the female olm and that the first developmental steps already take place in the fallopian tube. A confirmation of this finding by a repeated examination is still pending, but Hildebrandt is “90 percent sure”.

Photo: Anne Ipsen

The examination is part of a project to study the olm population in the Hermann's Cave and to improve the condition for their reproduction in the cave's olm lake. Although eggs have been found in the past, no offspring has been reported so far. The project is coordinated by Dr Anne Ipsen from the “Gesellschaft für Freilandökologie und Naturschutzplanung (GFN)”, since 2015 in close cooperation with the reproduction specialists of the Leibniz-IZW.


Article in the Volksstimme (in German):