Monthly Archives: October 2021

Hello Jorunna artsdatabankia; new sea slug for Norway and to the World!

In 2018 former master student Jenny Neuhaus started working under supervision of Manuel Malaquias and Cessa Rauch on the sea slug species Jorunna tomentosa.

Jenny presenting her work on Jorunna tomentosa on the world malacology conference in the USA

It was known already for some time that this sea slug occurs in a wide variety of colour patterns (morphotypes). With the increased discovery of cryptic species due to improved molecular techniques we wondered if we were dealing with a single species or several cryptic lineages.

For a long time the different colours and patterns were regarded as natural variation within the species, consisting of shades of grey-white, cream-yellow, pale orange and either plain of blotched with light brown or chocolate brown spots of various sizes, distributed either irregularly or in lines, or combination of both!

But it was this variety that tossed up the question eventually whether we are dealing with a single species after all.

The diversity within Jorunna tomentosa

The nudibranch genus Jorunna consisted of eleven recognized species occurring in European waters. At that time, Jorunna tomentosa (Cuvier, 1804) was the only known species of this genus to be found along the Norwegian coastline. Prior to the study, the northernmost record of J. tomentosa was listed from Vestvågøy, Lofoten, Nordland. Today we know that the species is found at least 550 km further North in the Magerøysundet, Troms og Finnmark.

Jorunna tomentosa has an oval-elongate body shape with different colours varying from grey-white to cream-yellow and pale orange. They can reach a size up to 55 mm and occur at depths from a few meters down to more than 400m. They feed on sponges of the species Halichondria panicea, Haliclona oculata and Haliclona cinerea. J. tomentosa can be found from Finnmark in northern Norway, southwards along the European Atlantic coastline, the British Isles, the French coast, Iberian Peninsula, Mediterranean Sea up to Turkey, and the Azores and Canary Islands. Besides the species has even been recorded from South Africa.

Jenny Neuhaus in the lab of Prof. Marta Pola in Spain dissecting specimens for anatomical studies

Jenny compared specimens from different parts of the world, including Norway, Ireland, Spain, France, Portugal including the Azores and South Africa. She took tissue samples for genetic studies and dissected them for their anatomy.

For the genetic studies we selected three different gene markers called COI, 16S and H3 to check how these morphotypes compare with each other and evaluate the meaning of genetic distances.

From the genetic distance analyses, it became clear that we were dealing with a “cryptic species complex”, as a clade of three specimens showed substantial genetic difference compared to J. tomentosa but seemed morphologically indistinguishable from another at first glance.

As sea slug anatomy is a matter of complexity, especially since each animal possesses both male and female reproductive organs (hermaphrodite), the expertise of Prof. Marta Pola from the University of Madrid was essential to conduct detailed morpho-anatomical studies. We were able to detect structural differences in the rasping tongue (radula) and parts of the reproductive apparatus.

Meet Jorunna artsdatabankia!

Jenny sequenced the DNA of 78 specimens of which 60 where successful for using in the final phylogenetic analyses. Her results supported the presence of a new Jorunna species, and in addition a possible case of incipient speciation in J. tomentosa with two genetic lineages morphologically undistinguishable. The new Jorunna species was based on material collected from Norway (Kristiansund, Frøya & the North Sea).

Jorunna artsdatabankia

J. artsdatabankia has a plain white to yellow background colour accompanied by small brownish spots irregularly placed on the body surface. Its distributional range is so far restricted to Norway, being recorded from Skogsøya, Frøya (Trøndelag), Brattøya, Kristiansund (Møre og Romsdal), and a North Sea plateau (60.726944 0.505371) with a depth range from 27 to 350 meters, suggesting a sympatric occurrence with J. tomentosa.

Jorunna artsdatabankia in comparison to Jorunna tomentosa

The name attributed to this new species was chosen to recognize the work of the Norwegian Biodiversity Information Centre (Artsdatabanken) for their instrumental role promoting and supporting biodiversity research in Norway.

– Cessa Rauch, Jenny Neuhaus, Manuel Malaquias

 

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The paper can be found here:

The genus Jorunna (Nudibranchia: Discodorididae) in Europe: a new species and a possible case of incipient speciation. Jenny Neuhaus, Cessa Rauch, Torkild Bakken, Bernard Picton, Marta Pola, Manuel António E Malaquias (2021), Journal of Molluscan Studies, Volume 87, Issue 4, December 2021, eyab028, https://doi.org/10.1093/mollus/eyab028

On the study of the diversity of Euphysa in Norwegian Waters

NorHydro’s student and collaborator Carla García has just defended her MSc thesis! We asked her to share with us a little bit about her project and this is what she had to say:

During summer 2020 I started learning about hydrozoans through online chats with my supervisor, Luis Martell. At that time, I was not familiar with these curious animals but they caught my attention and by September that year I had already fallen in love with them so I moved to Mallorca to pursue a Master’s Degree in Marine Ecology and work with hydrozoan diversity. For my master’s thesis I worked in a case that was part of project NorHydro (Norwegian Marine Benthic Hydrozoa), led by Luis at the University Museum of Bergen. The global pandemic has put many limits and obstacles in the way of my project, but I have been able to cope with them successfully by combining presential lessons in Mallorca with online courses and meetings with my fellows in Norway.

Me in Mallorca sampling my first benthic hydrozoans (Pennaria disticha and Eudendrium sp.) Picture credits: María Capa and Carla García.

My research was focused in the diversity of genus Euphysa (family Corymorphidae), which had not been assessed in Norway before. I wanted to determine which and how many species of this genus are present in Norwegian and adjacent waters and to characterise them morphologically and genetically. The problem with these animals is that many Euphysa species are not easy to tell apart from each other and there is a big taxonomic controversy within this group. For example, Euphysa aurata is one of the most frequently reported species in Norway, but are we sure that all the records belong to the same species?

Detailed observations of the samples raised my suspicions about the possibility that a complex of species could be hidden within this species name. To try to solve this problem I used an integrative approach combining molecular (DNA barcoding) and morphological analyses (documenting diagnostic characters). The result of this was that we discovered a new species of Euphysa in the waters outside Bergen and we are in the process to describe it!

Medusae of Euphysa aurata (top row) and Euphysa sp. nov. (bottom row), the main taxa covered in my project and two easily confused species. Picture credits: NorHydro and HYPNO.

The first step in the approach I followed was the field work. I gathered samples of hydromedusae and polyps from different localities across the Northeast Atlantic waters and also used some preserved specimens from the University Museum of Bergen. Because last year’s restrictions during the pandemic, part of my samples had to be sent by post to Mallorca, where I carried out the second step: laboratory work. This part included all the steps that go from the DNA extraction to the sequencing of three specific DNA fragments (called barcodes), which allow us to identify and distinguish between species based on similarity with reference sequences from online databases. Then, I applied some phylogenetic analyses and species delimitation tools. What these techniques do is to infer the evolutionary history of the three DNA markers that I sequenced (COI, 16S, and ITS). The results are visualized in the form of phylogenetic trees that we have to interpret and to decide if they are reliable or not. Then, I used species delimitation software to delineate species boundaries. The last step was to look again at the morphology and search for diagnostic characters that allow us to differentiate the species of Euphysa.

Sampling with my lab partners Mariana Strauss and Raúl González. We were looking for hydroids, small worms, and goose barnacles for our respective research projects. Picture credits: María Capa and Carla García.

Each and every life form that make up our planet, no matter how small it is, is a key component to the functioning of the Earth as a whole, and for that they deserve to be studied. Knowing how many species inhabit the Earth has always been one of the main questions of science, so I am really happy to contribute to a better understanding of ocean biodiversity and concretely, to hydrozoan systematics.

If like me, hydrozoans have piqued your curiosity and you want to know more on the activities of NorHydro and my results, you can check NorHydro’s home page and Facebook page, as well as the hashtags #HYPNO and #NorHydro inTwitter.

-Carla García-Carrancio