World Taxonomist Appreciation Day

In celebration of Taxonomist Appreciation Day (19 March), the World Register of Marine Species (WoRMS) has released its annual list of the top-ten marine species described by researchers during 2020, including a specie nominated by National Museums NI Curator of Marine Invertebrates, Bernard Picton. 

Bernard, a Mollusca editor for WoRMS mainly responsible for the heterobranch sea slugs, nominated the nudibranch sea slug, Dendronotus yrjargul, also known as the Yellow Sea Slug of Ørland, after having met the divers who found it when they attended a nudibranch safari at Gulen Dive Centre near Bergen, Norway.

Sea slug research in Norway had been dormant for 70 years until Gulen Dive Centre started a regular nudibranch safari event, which brought together scientists from Trondheim, Belfast and Moscow to teach amateur divers to photograph and study the abundant nudibranchs in the Sognefjord each March when their numbers explode after the dark Norwegian winter. Since 2013, a number of new species have been discovered, given names and subsequently or simultaneously been found in Ireland.

The almost unpronounceable name of the species, ‘yrjargul’, is based on the Norwegian name of the site where it was found by two Norwegian underwater photographers. The two divers, Kjetil Johnston and Victor Grøtan, learned how to document and collect their new discovery through the Gulen safaris. It was finally named in 2020 as part of a landmark study on the genus Dendronotus.

What is Taxonomy? 

Taxonomy is a branch of biology concerned with the classification, description and naming of organisms. Taxonomist Appreciation Day, celebrated annually on 19 March, is a day when we honour the hard work done by taxonomists around the world, who ensure that every species on Earth has a name and only one name. Taxonomists also study the evolutionary pathways which have created each specie over the 4 billion years since life began on Earth. This work has accelerated in the last 30 years due to the creation of new technologies, such as DNA sequencing and new publication and communication technologies such as the internet.

In 1982, an initiative to curate a database of marine species for Northern Ireland was initiated as part of a survey of marine life around the coast undertaken by staff at the Ulster Museum. This involved compiling a list of species names from literature and searching existing lists, such as the Plymouth marine fauna (Marine Biological Association, 1957), Isle of Man marine fauna (Bruce et al., 1963) and identification guides. As part of a joint project between the Ulster Museum and the Marine Conservation Society in 1997, this list was published as a book and a database by the Ulster Museum (Howson & Picton, 1997), with each species group checked by a leading taxonomist.

In 1998, a project to extend the list to cover all marine species in Europe was funded by the European Union MAST research programme, led by Mark Costello from Trinity College, Dublin, one of the Amphipoda editors for the Howson & Picton list. The European list (ERMS) evolved directly into the World list (WoRMS) and the UK list.


Howson, C.M.; Picton, B.E. (1997). The species directory of the marine fauna and flora of the British Isles and surrounding seas. Ulster Museum Publication, 276. The Ulster Museum: Belfast, UK. ISBN 0-948150-06-8. vi, 508 (+ cd-rom) pp

Korshunova, T.; Bakken, T.; Grøtan, V. V.; Johnson, K. B.; Lundin, K.; Martynov, A. (2020). A synoptic review of the family Dendronotidae (Mollusca: Nudibranchia): a multilevel organismal diversity approach. Contributions to Zoology. 90(1): 93-153., available online at 

Marine Biological Association. (1957). Plymouth Marine Fauna. Third edition. Plymouth, England 457pp., charts 1-4. 

Bruce, J. R., Colman, J. S. and Jones, N. S. 1963. Marine fauna of the Isle of Man and its surrounding seas. Memoirs of the Liverpool Marine Biological Assocation 36: 1-307. 

More details

Image: Dendronotus yrjargul. Photo courtesy of Victor Grøtan
Dendronotus yrjargul. Photo courtesy of Victor Grøtan