As A Zoologist
Bergh started to study molluscs when he was nearly 30, probably under the influence of Japetus Steenstrup, a Danish biologist who was 11 years older than he was and who was a professor of zoology at the University of Copenhagen.
He wrote reports of the Challenger expedition (1884) and the Albatross expedition (1894). He took part in the "Siboga Expedition" in 1905, exploring the waters of Indonesia.
Bergh became the world's leading expert on nudibranchs. He wrote his main malacological works as well as over 90 malacological articles and papers. Among other notable works are his work about the anatomy of the radula of the genus Conus (1896). His malacological drawing are considered to be "excellent". He was mainly anatomist and reached great progress in systematics based on anatomy of nervous system and of reproductive system of gastropods. Bergh was very active in naming and describing species of nudibranchs and other sea slugs. The species he named include:
- Armina semperi
- Chromodoris annae
- Chromodoris dalli
- Chromodoris elisabethina
- Chromodoris morchii
- Chromodoris punctilucens
- Thuridilla lineolata
- Phyllodesmium briareum
- Phyllodesmium longicirrum
The nudibranch genus Berghia was named after him by Salvatore Trinchese in 1877.
His colleague and friend was German ethnologist and animal ecologist Carl Semper.
Read more about this topic: Rudolph Bergh