Category Archives: Mollusca

Project kick-off; Lower Heterobranchia and Pyramidellidae of Norway

Since September 2023, a new taxonomic project started at the University Museum studying the biodiversity of sea snails (with shell) and sea slugs (without (visible) shell) in Norwegian marine habitats. This project is in a way a follow up from the “Sea slugs of Southern Norway” project between 2018–2020, but this time with a focus on poorly studied habitats including seagrass meadows, maerl coralline algae beds and landlocked fjords (“polls”). The target groups of this project are tiny sea snails of just a few millimeters, which are part of a group called “Lower” Heterobranchia and Pyramidellidae (Image 1) that together with the former ophistobranchs (e.g. the sea lugs), and pulmonates (slugs and land snails) form the Heterobranchia, one of the main evolutionary lineages of the Gastropoda.

Snail shells on a black bacground

Image 1: Example of shells of a “Lower Heterobranchia” (A) and a Pyramidellidae species (B). Picture CRauch & MMalaquias.

The diversity of these tiny sea snails is poorly understood in Norway. Currently, nine families are known in the country: Acteonidae, Cimidae, Mathilidae, Murchiconellidae, Omalogyridae, Rissoellidae, Tjaernoeiidae, Xylodisculidae and Pyramidellidae (Høisæter 2014), but their small size and similar shells make it challenging to identify the species. During this project these sea snails will be studied in Norway for the first-time combining DNA barcoding and morphology. Sampling will be based on the use of dredges, grabs, and snorkeling by collecting the substrate they live on.

Pyramidellidae are ectoparasites and are often found living on other molluscs or other marine invertebrates, but also on soft sediments. The University Museum of Bergen has already a good collection of “Lower” Heterobranchia and Pyramidellidae from Norway, but a large part of this material is not suitable for DNA extraction due to the original fixation methods based on the use of formaldehyde. Therefore, after the first months of cataloguing the “old” collection and setting up protocols for DNA extraction, we finally set out in February to collect fresh material. We visited two different sites around Bergen to try out collecting specimens by snorkeling and test the efficiency of a recently acquired portable hand-dredge (Image 2).

A small metal dredge, rope and a buoy on a dock

Image 2: The hand dredge which was used for collecting specimens. Picture MMalaquias.

Our first fieldwork day took place at the Marine Biological Station of UiB at Espegrend. The field station is a convenient place as it features a fully equipped laboratory (Image 3), and just in front of the station there is a seagrass meadow dominated of Zostera marina. This eelgrass is often found in shallow and sheltered coastal areas between 0.5 m to 10 m depth on flat sandy bottoms. Seagrass meadows are diverse and productive and can harbor hundreds of associated species from many different groups of animals. One team member swam with the dredge over the seagrass meadow and dropped it about 30 m from the shoreline, while the other team member pulled it back by hand. In addition, substrates like algae, blue mussels, and ascidians were hand-picked by snorkeling.

A scientist in a lab, looking in a stereo microscope

Image 3: First fieldwork for the new project, with project leader Manuel Malaquias behind the stereomicroscope searching for sea snails and slugs at Espegrend Marine Biological Station. Picture CRauch.

These efforts yielded the first specimens, namely the “Lower” Heterobranch species Ammonicera rota (Image 4) and the sea slug Elysia viridis (Image 5).

During our second sampling event, because of bad weather conditions with strong southern winds, we decided to visit a sheltered popular swimming area (although at this time of the year not so popular!) located north of Bergen called Helleneset (Image 6). Helleneset is a rocky shore area rich in algae and kelp with sand flats in between.

Two people on a pier in wet weather

Image 6: Second fieldwork trip, at the popular swimming area called Helleneset, on a wet and cold February day deserted. In the picture Manuel Malaquias and Cessa Rauch. Picture CRauch & MMalaquias 

This time the algae and kelp mats collected by snorkeling in ziplock plastic bags did not yield much, but a close examination of the sand (with help of stereomicroscopes) collected again with the hand-dredge revealed the presence of many little gastropod snails. One of these little snails was our first Pyramidellidae; the identity is not yet completely confirmed, but it looks like Eulimella ventricosa (Image 7).

a small shelled gastropod on a black bacground

Image 7: A Pyramidellidae found from Helleneset, a possible Eulimella ventricosa. Picture MMalaquias.

These two first samplings days were a good test for how we best can collect these snails which are small and in general a little abundant. The dredge is easier to operate with two people working together; one to deploy it and the other to pull it back to shore. Sandy samples yield better results if left to rest for several hours and even days in trays or buckets because anoxic conditions begin to form, forcing the animals to crawl out of the sediment.

This is just the beginning, if you want to be part of the journey of the diversity of “Lower” Heterobranchia and Pyramidellidae in Norway, we will be regularly updating stories and findings on this channel, and our social media accounts @SeaslugsofNorway (both Instagram and Facebook), see you there!

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References

Høisæter, T. 2014. The Pyramidellidae (Gastropoda, Heterobranchia) of Norway and adjacent waters. A taxonomic review. Fauna Norvegica, 34: 7-78.

One Ocean Week 2024

the banner for OOW seen outside the University museum

From April 13th to 19th 2024, the Ocean City of Bergen celebrated the ocean even more than usual(!) in a happening called One Ocean Week (OOW).

One Ocean Week held conferences, meetings, workshops and activities – aiming to pioneer a sustainable use of the ocean.

The marine group at the University Museum was a prolific participant during the event, here are some of our contributions!

 

 

Anne Helene was invited to give the opening talk at the reception in the Aula, placing the Museum and Bergen into the heart of the Norwegian ocean exploration beginning with “The Norwegian North-Atlantic Expedition 1876–78”.

researcher giving a presentation

Anne Helene giving the opening talk during the festivitas in the Aula at the University Museum. Photo: Jenny Smedmark

Screenshot from the documentary. Do follow the link -> to watch if you haven’t already! Photo: OceanX

 

Aino also made a guest apperance in the aula as the documentary about “Seeing jellyfish as they should be seen” made by the OceanX media team was shown.

 

 

Saturday brought a presentation at Skolten about the UiB/OceanX-expedition last August, where Joan and Anne Helene presented some of their exciting new findings together with Henrik and Øyvind from BIO – and even Mattie of OceanX participated, calling in from the OceanXplorer in Singapore!

Presentations of what we found during the OceanX/UiB cruise last summer, where we explored old locatlities in the Norwegian Sea, and visited some of our fjords using the world’s most advanced research vessel. Pictured are Anne Helene, Joan and Henrik – with their animals! Photos: Katrine Kongshavn

On Sunday the 14th most of us were at Festningskaien with a plethora of activities during the “Family Day”.

Our tent at the Family Day. Photo: Joan J- Soto-Angel

For our “Meet marine biologists from the University Museum” we brought with us five activities focusing on different areas of research that we do.

We had:

  • Sharks (see SharkReferences.com for more), with a shark tooth quiz, info about sharks in Norway, and the chance to see shark skin up close.
  • Bipolar animals (project Pole2Pole) where people could explore the distribution of animals that occur in one- or both- of the poles, and learn more about why that may be the case
  • Polychaetes (project MAnDAriN) with a quiz of trying to match images of colourful bristle worms to their common names
  • A task on Jellyfish parasites(!) (project ParaZoo) where you were to diagnose which parasite our unfortunate jellyfish suffered from, and finally
  • Moss animals (project NorDigBryo) where you could learn more about these animals, see them up close, and pick up a booklet with fun facts and some riddles to solve.

    Our activities. From top left: Jellyfish doctor, bipolar animals, guess the worm, sharks, and moss animals. Images: Joan J. Soto-Angel

    Two of the museum pedagogues used our tent as the base for their theatre-based activity “The ice is melting! It is for real!” – so we had penguins too!

    The penguins Piia and Pling in action. Photo: Odette Tetlie

    At the Natural History Museum, our researchers offered free talks on topics of their choice; one talk every day (Tues-Fri). The topics covered here were:

    Who eats whom? Marine worms with jaws – delicious and dangerous! (Nataliya)
    Jellyfish in Norway – mostly harmless or murderous monsters?     (Aino)
    Sharks of Norway     (Nico)
    Elusive biodiversity: a journey through the less known but most exquisite groups of marine animals (    Manuel)

    a person pointing to a phylogenetic tree showing gastropods and how they are related

    Manuel during his presentation at the Natural History Museum. Photo: Cessa Rauch

    Nico also gave a talk at the scientific conference Ocean Outlook: the North Atlantic Ocean climate, deep sea and environment, on the topic “Bioluminescence in deep-sea sharks: evolution and functions.”

It was a hectic, but fun week!

-Katrine on behalf of the marine group

Sea slug day 2020; Jorunna in the spotlight

Today we celebrate Sea Slug Day! ✨

The day coincides with the birthday of Terry Gosliner, who has discovered one-third of all known sea slug species (more than a 1000!). Here’s a link to how October 29th became #SeaSlugDay.

And what better way to celebrate it than introducing a new species to the world. Today it will all be about the Jorunna tomentosa species complex that our master student Jenny Neuhaus studied for the last two years.

Jorunna tomentosa, picture Cessa Rauch

Jorunna tomentosa is known to occur in a wide variety of colour patterns, which tossed up the question whether we are actually looking at a single species at all, or maybe dealing with cryptic lineages.

The colour diversity of Jorunna tomentosa, picture by Anders Schouw, Nils Aukan, Cessa Rauch, Manuel A. E. Malaquias

Jenny compared specimens from Norway, Ireland, Spain, Azores and South Africa, both genetically as well as anatomically. She used different gene markers like COI, 16S & H3 to check how these morphotypes compare with each other and evaluate the meaning of genetic distances. But she also did an elaborate morpho-anatomical study to look for differences between these colour patterns. Together with Dr. Marta Pola in Madrid, they dissected the different J. tomentosa specimens and looked at parts of the digestive (radula & labial cuticles) and the reproductive systems. These are all key to help unraveling putative different species and characterize them.

About Jorunna tomentosa

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.

Before Jenny studied J. tomentosa, the various colour morphs were regarded as part of the natural variation of the species. By combining molecular phylogenetics with morpho-anatomical characters Jenny investigated the taxonomic status of the different colour morphs of J. tomentosa.

Jorunna sp. nov.?

Jenny sequenced 78 specimens of which 60 where successful for using in the final phylogenetic analyses. Her results supported a new Jorunna species, and a possible case of incipient speciation in J. tomentosa with two genetic lineages morphologically undistinguishable.

From left to right Jorunna spec. nov. Jorunna tomentosa lineage A and down Jorunna tomentosa lineage B

The new Jorunna species was based on material collected from Norway (Kristiansund, Frøya & the North Sea). Jorunna spec. nov. has a distinct colour pattern of cream-yellow with dark small dots (plus, as important; major differences in the radula and reproductive system).

Jorunna spec. nov.

It has been our pleasure to have Jenny here as a student, and she has done excellent work. Last year she won best student poster award last year with her work on Jorunna tomentosa at the World Congress of Malacology in California, USA. Most recently, Jenny defended her thesis on October 26 and passed with an A for her great work – congratulations from all of us at the Museum!

-Cessa Rauch

Sea slugs of Norway Instagram: @seaslugsofnorway

Sea slugs of Norway Facebook: www.facebook.com/seaslugsofnorway

Meet ZMBN 130407!

How much information do you think we have on the animals in our collections? 🤔

Quite a lot more than you might think, and here to help us show you, we have a small snail from the shore. Meet specimen #ZMBN 130407, a Littorina saxatilis 🐌 (rough periwinkle/spiss strandsnegl).

We collected it one year ago on our fieldwork up North, in Tendringsvika near Tjeldsund (Troms): our northernmost station on the trip.

Tendringsvika in Troms

Here’s a short video of the habitat: notice how the sea urchins dominate once we get below the intertidal zone!

To be able to use the Invertebrate Collections for research, we need to know quite a lot about each animal (“specimen”). Standard information would be where, when and how it was collected, who collected it, who identified it (and revisions), notes about the habitat, images if any, and the museum number that it is registered within our database.

A screenshot of how it may look when a specimen is registered in our database

If there is genetic data – like here, a DNA barcode as part of NorBOL – we also need the genetic information. This information is stored in the international barcode library BOLD (BOLDSystems.org), where it is organised in projects containing information linked to the physical specimen, and to the DNA.

Small snail, much data!

If you look at the lower right corner, you will find information about specimens that have identical DNA sequences, and who are therefore grouped together in what is called a BIN in BOLD (/OTU). Most of the other specimens with identical DNA barcode have also been identified to Littorina saxatilis, but not all…that’s one reason to keep the animals in museum collections, so that identifications can be re-checked if needed 🔬.

Through our project (hardbunnsfauna) on shallow water hard bottom fauna from Norway, we are helping build a good DNA barcode library of species that occur in Norway – with reference (“voucher”) specimens in the scientific collections of the University Museum of Bergen, and with our partner, NTNU University Museum.

-Katrine

Sea slugs from Vestfold

Larvik & Sandefjord 22.10.2019 – 27.10.2019

From October 22 to October 27, Sea slugs of Southern Norway crossed the Hardangervidda mountain pass to pay a visit to Larvik Dykkeklubb (LDK) and Sandefjord Dykkeklubb (SDK). Vestfold, in particularly the Larvik area, was a thorn in the side for the sea slug project. With fieldwork and collection trips covering most of the Hordaland area (Bergen, Espegrend), Rogaland (Egersund), Mandal (Vest-Augder), Drøbak (Oslofjord area) a lot was left to be discovered still for Aust-Agder and Vestfold. Therefore, a visit to Vestfold was very high on our bucket list.

With Winter just around the corner, we decided to squeeze in a short fieldwork trip to Larvik just before the end of 2019. Me and Anders Schouw drived from Bergen to Larvik with our rented caddy to meet up with Tine Kinn Kvamme and members of the LDK. On Tuesday morning, after packing our mobile laboratory in the car, we drove off to Larvik. In the early evening we arrived at the LDK, there we were welcomed by Lene Borgersen from LDK, who facilitated access to the clubhouse for sorting sea slugs during our stay. That evening was also a club members evening, and I took that opportunity to give a presentation about sea slugs and the Sea slugs of Southern Norway project

It was a great evening talking about sea slugs with interested club members while eating pizza! The next day Tine, Anders and I met up with LDK member Mikkel Melsom, who joined to help on our hunting for sea slugs

Picture 2. Some sea slugs from Larvik; from left to right; Limacia clavigera, Edmundsella pedata, Diaphorodoris luteocincta, Tritonia hombergii, Tritonia lineata and Cadlina laevis. Photo credits Anders Schouw

Later that day we met up at the SDK clubhouse with Stein Johan Fongen, where I had the opportunity to once again talk about sea slugs this time to the SDK members. This was a very special evening because among the audience, besides SDK members, we also had students from Sandefjord videregående skole (Sandefjord High School)

Sea slug presentation for students of the Sandefjord videregående skole and Sandefjord Dykkeklubb members. Photo credits Tine Kinn Kvamme

In the following days several members of the SDK also joint us collecting sea slugs. Despite the fact that October is known for being not an ideal season to find sea slugs (most species are observed during Winter and (early) Spring) we still somehow ended up with hours of sorting work at the Larvik clubhouse

Cessa Rauch & Anders Schouw sorting sea slugs in the Larvik clubhouse. Photo credits Tine Kinn Kvamme

Overall, we collected 21 different species, all newly registered specimens for the project with regard to this part of the country. It would be great to see what the species abundance would be during a sea slug season like February or March!

Overview of the species collected at Larvik and the Sandefjord area

Besides sea slugs and enthusiastic club members, another highlight of the week was a visiting seal at SDK! On our last day of fieldwork, a young seal was very bold and decided to rest close to the clubhouse in the harbor. It let people come up really close, which was great for making cute seal pictures. Cherry on the cake, in my opinion!

Young seal in the harbor close to the Sandejord Dykkeklubb. Photo credits Anders Schouw

On Sunday the tree of us had to say goodbye, Tine would go back to her hometown Oslo and Anders and I would cross the snowy mountains again back to Bergen. It was a short but sweet visit and great opportunity to meet members of Larvik and Sandefjord dykkerklubbs. I therefore want to thank LDK and SDK for their interest, enthusiasm and help for the few days Anders, Tine and I were around. I surely hope we will meet again next year, and find many more sea slugs. And of course, thanks to Anders and Tine for helping again, hope we can share many more sea slug adventures together

Left to right; Tine Kinn Kvamme, Cessa Rauch and Anders Schouw in front of the Larvik Dykkeklubb were most of the ‘lab’ work was done. Photo credits Lene Borgersen

More sea slugs: 

Do you want to see more beautiful pictures of sea slugs of Norway? Check out the Sea slugs of Southern Norway Instagram account; and don’t forget to follow us. Become a member of the Sea Slugs of Southern Norway Facebook group, stay updated and join the discussion! Hunger for more sea slug adventures, check our latest blog posts.

Explore the world, read the invertebrate blogs!

– Cessa

World Congress of Malacology 2019: 10 – 17 August 2019

On August 10, four delegates from the University Museum of Bergen made their way to Monterey Bay California, USA.

Attending the World congress of Malacology 2019, from left to right; Jenny Neuhaus, Justine Siegwald, Manuel Malaquias & Cessa Rauch

This year the World Congress of Malacology took place at the Asilomar conference grounds in Pacific Grove, Monterey. Monterey Bay is well known among many marine biologists due to its world-famous aquarium and aquarium research institute (MBARE), many marine protected areas (7; including the Asilomar State Marine reserve, close to where the conference was held), Hopkins Marine Station of Stanford University, Steinbeck Center (although located in Salinas, close enough to make it count). The latter was named after the famous marine biologists John Steinbeck and Ed Ricketts from the Monterey County; Among other works they contributed to marine biology with their famous books ‘The sea of Cortez’ and ‘Between Pacific Tides’. All in all, Monterey Bay seems like an exciting place to be for us marine biologists.

The World Congress of Malacology was organized and chaired by the famous Terry Gosliner (Terry described more than 1000 species of sea slugs!) a senior curator of the California Academy of Sciences. About 300 participants contributed to a very lively and busy scheduled week

Some of the participants of the World Congress of Malacology 2019

Registration for the conference started on Sunday the 11th of August, but Monday was the real kick off of the program with fabulous keynote speakers such as Geerat Vermeij, David Lindberg, Susan Kidwell, etc.. During the poster session Jenny Neuhaus and Cecilie Sørensen, two of our master students working in close collaboration with the Museum project Sea Slugs of Southern Norway have presented their preliminary results. Unfortunately, Cecilie could not join us due to time constraints, and the poster was presented by Cessa

Justine presenting her work on Scaphander

On Tuesday we had a crammed agenda with multiple speakers talking at the same time, divided over the different halls in a variety of sessions. It was a busy day of running around trying to catch those talks one were most interested in. Justine had her talk in the Systematics session about her PhD research on Scaphander titled; First global phylogeny of the deep-sea gastropod genus Scaphander reveals higher diversity, a possible need for generic revision and polyphyly across oceans. It received a lot of attention and numerous questions afterwards, it was great to see how her research was perceived with so much curiosity and enthusiasm.

Wednesday we had a day off filled with several excursions. Jenny went to the whale watching trip, Justine went to spot marine mammals and Cessa to a trip along the coast to meet and greet the Californian red giants. The trips were all well organized and a very nice break off the week as the many presentations and sessions made the days long and intense. The whale watching trip took place in Monterey Bay and Jenny was lucky enough to observe the mighty blue whale, Balaenoptera musculus, plenty of humpback whales (Megaptera novaeangliae), and several sunfish (Mola mola) swimming at the surface. It was an incredible experience for her to be able to watch the animals thrive in the great Pacific Ocean.

Whale-watching with Jenny Neuhaus in Monetery Bay

Cessa walking in between the Californian red giants

 

The trip to South Monterey was along the California’s rugged coastline and provided one of the most spectacular maritime vistas in the world. It has peaks dotted with the coast redwoods that go all the way to the water’s edge. The trip took you to Pfeiffer Big Sur State Park where we got the opportunity to walk through the redwood forest. Along the way we stopped at numerous scenic vistas, it was definitely a memorable day .

 

On Thursday, all well rested, we had another hectic day full of presentations, this time it was Cessa’s turn, she would talk about the ‘Sea slugs of Southern Norway project as an example of citizen science’ (Picture 8. Cessa presenting the sea slugs of Southern Norway project). It was placed in the citizen science session and many that attended had questions about citizen science which constituted a great opportunity to share our experience acquired during the last year of our project.

Cessa presenting the sea slugs of Southern Norway project

Friday, on the last day of the conference, Manuel had his talk about the phylogeny and diversity of the Indo-West Pacific gastropods Haloa sensu lato (Cephalaspidea: Haminoeidae): Tethyan vicariance, generic diversity, and ecological specialization. This was part of the recent collaborative work his previous PhD student Trond Oskars

Manuel Malaquias presenting his and Trond’s work on the phylogeny of Haminoeidae

Jenny Neuhaus won the best poster award for her research on Jorunna tomentosa

 

The day was closed off with a big dinner and the award ceremony. Prizes were handed out to the best student’s oral and poster presentations. Jenny was awarded by the Malacological Society of London the prize for the best student poster. This was a very exciting way to end a successful conference trip!

 

 

 

-Cessa & Jenny

Success in the South; fieldwork in Mandal

From May 20th to 27th the sea slugs of Southern Norway team headed South to Mandal to pay a visit to the Mandal dykkerklubb and try to find more enthusiastic citizen scientist to join the sea slug project. We had a few special guests invited for the week and the team consisted of Cessa Rauch, Manuel Malaquias, Anders Schouw, Erling Svensen, Nils Aukan, Tine Kvamme and Heine Jensen. In Mandal the head of the club Erling Tønnessen would be there to help us around and organize club activities for collecting the sea slugs.

The first day basically consisted of traveling to Mandal and setting up our “hyttes” for a week of sea slug hunting. As usual we underestimated the amount of space needed to bring our ‘mobile’ lab to the camping site in Mandal. Even though a station wagon theoretically fit a family of five plus luggage, it was barely enough space for a family of sea slug hunters with their equipment.

Picture 1. We accomplished to fit everything in this rental car, picture Cessa Rauch

We ended up with a challenging Tetris game and me being squeezed between microscopes and jars in the back seat, still, no complaints! At least I was spared for driving the long hours from Bergen all the way to Mandal, that every local would be able to fix in less than 7 hours, we managed to take 12. I guess the car was heavy loaded! Manuel did a fantastic job while Anders and me where dozing off. Eventually we managed to arrive safely in Mandal and there we were greeted by our team of citizen scientists that helped us out through the week. They as well had to travel from all corners of the country; Kristiansund, Egersund, Oslo and Sarpsborg. It was quite special to arrive all together in Mandal with only one thing in our minds; finding sea slugs!

The next days in collaboration with the local Mandal dykkerklub and their fantastic club boat equipped with a lift to get people in and out of the water, we operated most of the sampling activities. After a day out collecting we would all go back to our cabins and start photographing and registering the samples.

Even though late spring is supposedly not the best season for collecting sea slugs, due to low abundance of the different species, together we were still able to collect 47 different species!

Picture 4. Overview of the species collected during fieldwork in Mandal

On our last day of the expedition, the Mandal dykkerklubb organized an evening social gathering for their members in which we had the chance to give a presentation about sea slugs and the project, and to give away a few sea slug sampling kits to all those interested.

Picture 5. Cessa and Manuel presenting the sea slugs of Southern Norway project, picture Erling Svensen

Picture 6. Interested dive members of the Mandal dykkerklubb showing up to learn more about sea slugs and having a good time, picture Erling Svensen

With every fieldwork trip we get more experienced in the organization and execution of the event and this is definitely paying off in the diversity of species we manage to collect. We were not able to register so many species before as with this fieldwork trip to Mandal. This was by far the most successful expedition and together with the joined efforts off all the excellent citizen scientist we formed a real professional sea slug team!

Picture 7. Group picture of the expedition members on board of the Mandal dykkerklubb boat, left to right; Heine Jensen, Erling Svensen, Anders Schouw, Cessa Rauch, Tine kinn kvamme, Nils Aukan and the expedition leader Manuel Malaquias in front, picture Erling Svensen

At the moment we are waiting for the first DNA barcode results in order to confirm the species diversity we found that week. An update will follow; but Manuel and I would like to take this opportunity to gratefully acknowledge all the efforts and interest of our team members of that week and the good times we had together! Hope to meet you all again soon during yet another sea slug hunt! Tusen takk!

-Cessa

Door #19: Photosynthetic vs solar-powered sea slugs

I think we can all agree that sea slugs are amazing creatures. Some species contain toxins that are useful for cancer research and others are photosynthetic! There are a few species of sea slugs that have the ability to photosynthesize. But beware; the ability for them to do the thing that plants and algae are good at (photosynthesis), doesn’t always mean they are solar-powered. And I will explain you in the next few lines what I mean with that.

There are two families of sea slugs known to have a few species within them that can photosynthesize; it’s within the family of Facelinidae and the family of Sacoglossa.

Within the family of Facelinidae we have the genus Phyllodesmium; and all species in this genus are considered solar-powered, meaning that they get a part of their daily energy intake via photosynthesis. At the moment the theory goes that they are able to do so as they contain photosynthetic zooxanthella stolen from their feeding source (soft corals), and they continue to ‘farm’ these zooxanthellae in their own bodies. The species Phyllodesmium longicirrum masters this trade and is best known as the solar-powered Phyllodesmium

Solar-powered Phyllodesmium longicirrum by Jason R. Marks

The other family does things quite differently but nevertheless as impressive; those are the Sacoglossa.

A few representatives of the photosynthetic sea slugs within the Sacoglossa

Unlike Phyllodesmium, they don’t farm zooxanthella but they steal the photosynthetic cell organelles (chloroplasts or plastids) from the algae they feed on; also known as kleptoplasty (Kleptes (κλέπτης) Greek for thief). Approximately 140 years ago these sea slugs were first described by de Negri and de Negri, who discovered that these sea slugs were green colored due to foreign ‘bodies’ that were reminiscent to those known from plants. It took at least another 100 years before the ‘granule bodies’ were identified to be chloroplasts from the algae the slugs feed on. Sacoglossa are also known as sap-sucking sea slugs because of the way they eat their algae; at first, the sea slugs pinch a whole in the algae wall with their special teeth, called the radula. Then they suck out the cytosolic content of the algae (hence the name sap sucking sea slugs). Finally, the cytosol content is being digested in the digestive tract that perforates the entire body and within some species the chloroplasts are being sequestered and continue to photosynthesize in the animal’s digestive cells

Sap-sucking slug sequestering chloroplasts from the algae it feeds on (figure from Rauch et al. 2015)

Although the sea slugs are famous for their ability of stealing chloroplasts, they only represent a minority within the Sacoglossa. In fact, only 6 out of 300 described species, can keep the chloroplasts fully functional for long term, or long-term retention species; that is the chloroplasts are photosynthetic active for longer than 21 days after sequestration. The gross majority are either short term retention species (with functional chloroplasts up to 14 days or more) or cannot retain the chloroplasts at all (called non-retention species). This means that the chloroplasts are immediately being digested like the rest of the algae content.

So why are Sacoglossa photosynthetic but not solar powered like Phyllodesmium? Well this is because numerous studies observed how the sea slugs died as soon as they were being starved (meaning they couldn’t eat their algae food anymore) even though they had photosynthetic active chloroplasts in their cells. Besides, based on CO2 fixating measurements, it turned out that 99% of the sea slug has to live from normal ingested food, like all other animals do. This could very well explain why only 6 out of the 300 described species are able to sequester chloroplasts long-term, and apparently for reasons other than carbon fixation!

The take home message is that this case of photosynthetic and solar-powered sea slugs is a great example of how good science is about resisting the pull of easy conclusions. When something seems right at first, it should still be testified!

Furthermore
Interested in photosynthetic sea slugs? You can read more in the following papers that are also used as source for this blog:

  1. A sea slug’s guide to plastid symbiosis (2015) J De Vries, C Rauch, G Christa, SB Gould, Acta Societatis Botanicorum Poloniae 83 (4)
  2. Why it is time to look beyond algal genes in photosynthetic slugs (2015) C Rauch, J Vries, S Rommel, LE Rose, C Woehle, G Christa, EM Laetz (…), Genome biology and evolution 7 (9), 2602-2607
  3. On being the right size as an animal with plastids (2017) C Rauch, P Jahns, AGM Tielens, SB Gould, WF Martin, Frontiers in plant science 8, 1402
  4. Mitochondrial Genome Assemblies of Elysia timidaand Elysia cornigera and the Response of Mitochondrion-Associated Metabolism during Starvation (2017) C Rauch, G Christa, J de Vries, C Woehle, SB Gould, Genome biology and evolution 9 (7), 1873-1879
  5. The ability to incorporate functional plastids by the sea slug Elysia viridisis governed by its food source (2018) C Rauch, AGM Tielens, J Serôdio, SB Gould, G Christa, Marine Biology 165 (5), 82

Would you like to see pictures of sea slugs that you can find in Norway? Check out the Sea slugs of Southern Norway Instagram account,and don’t forget to follow us!
Become a member of the sea slugs of Southern Norway Facebook group, stay updated and join the discussion.

Explore the world, read the invertebrate blogs!

Door #17: Sea bunnies of Norway?

Some years ago, in 2015, the internet was taken a storm by the sudden rise of the so-called sea bunnies. It all started with a video taken the year before by a SCUBA diver in Japan who filmed the little creatures crawling around the seabed:

The species seen in the video is called Jorunna parva, and are since then worldwide unofficially known by the adorable pet name ‘sea bunny’ as it has a ‘fur’ like exterior with tiny upright ‘ears’ and a fluffy tail like bunnies do. The ‘fur’ is actually created by bunches of tiny rods, called the caryophyllidia. The caryophyllidia are arranged around little knots that are often dark coloured, which create the illusion of black dots on the animals. The seemingly ears are the animals rhinophores, that function as chemical receptors that make the animal able to detect its environment in search of food and other sea bunnies. Its tail on the back are actually its gills to extract oxygen molecules from the surrounding water, the ‘fluffier’ it is, the bigger the surface area, the easier it is to diffuse oxygen from the water. This sea bunny is small, often less than 2.5 cm, and can be found throughout the Indo-Pacific; from South Africa to Central Pacific. They have, like many sea slugs do, a high degree of colour polymorphism in the species, with colours varying from white with black dots, to yellow and even bright orange:

Different colours of Jorunna parva, aka the sea bunny (photo credits on image)

Unfortunately, our sea bunny J. parva is only short-lived and just lives from a few months up to a year, but at least during its short life it doesn’t need to worry about predators. They are very toxic, because of the food they eat, which are sponges. All dorid nudibranchs (the group of slugs J. parva belongs to) are toxic because of their diet, and these toxins are often used in cancer treatments for people. Who would have thought that sea bunnies would be lifesavers, besides  being cute? But is the word sea bunny only referring to this particular species called J. parva? A quick search on the internet definitely tells us otherwise, it seems people refer to sea bunnies when they talk about any other dorid nudibranch with a fluffy and round appearance.

So, the question remains, do we have any sea bunnies in Norway? And the answer is yes, we do!

Sea bunnies of Norway (click to enlarge!)

And they are absolutely great and adorable to encounter underwater. Let us make a list of the sea bunnies of Norway, so we know what species we are talking about. Sea bunnies of Norway are; Doris pseudoargus, Geitodoris planata, Jorunna tomentosa, Rostanga rubra, Cadlina laevis, Aldisa zetlandica, Adalaria loveni, Adalaria proxima, Onchidoris muricata, Onchidoris bilamata,
Onchidoris pussila, Onchidoris depressa, Acanthodoris pilosa, Diaphorodoris luteocincta and I personally would draw the line at Goniodoris nodosa, as the other Goniodoridae don’t resemble that much the typical sea bunny characteristics. What do you think? Which species do you think are missing in this list, or which species should be left out?

I think it is time to take over the internet with our sea bunnies of Norway!

 

Furthermore
You want to see more beautiful pictures of sea slugs of Norway!

Check out the Sea slugs of Southern Norway Instagram account; and don’t forget to follow us.
Become a member of the sea slugs of southern Norway Facebook group, stay updated and join the discussion.

Explore the world, read the invertebrate blogs!

-Cessa

Door #16: Basic anatomy of the sea slug

Haminoea sp, photo by M. Malaquias

“Sea slugs” include both the by far most famous nudibranchs, and groups such as the Sacoglossa (sap-sucking slugs, more about these later in the calendar!) and Cephalaspidea (the bubble snails), amongst others. These latter ones often do have shells – but reduced ones, too small for the animals to completely retreat into, like this Haminoea:

Nudibranchs, however, are the “naked” snails: Their name “nudibranch” comes from the Latin nudus, naked, and the Greek βρανχια, brankhia, gills. They don’t have a shell, but this wasn’t always the case. In their early larval life stage, they actually have a shell, but when settling down and transforming from zooplankton into adults, they lose the shell. The loss of the shell in adults might be responsible for the amazing diversity we see in body forms present in sea slugs.

So, in this basic anatomy of sea slugs we will focus mostly on the body forms of nudibranchs, but all other sea slug orders are not far off from this anatomy, if you know the basics of nudibranchs, you can extrapolate to the other orders as well. So here we go!

Nudibranchs are roughly divided in two type of body forms; the dorid nudibranchs and the aeolid nudibranchs.

Two basic body types found within the Nudibranchia; the dorids and the aeolids. (Illustration: C. Rauch)

The dorid nudibranchs have a thick mantle that extends over their foot. In some species the surface of the mantle is covered with tubercles than can vary in different sizes, numbers and shapes. This gives them often a rigid body that offers some protection.  In most of the dorids it is the mantle that contains toxins to defend themselves, the toxins are extracted from their food sources.

Aeolid nudibranchs have mantles that are covered with finger-like extensions called cerata. The cerata are very special as they contain branches of the digestive tract, and in some species, this is also visible! The tips of the cerata contain special organs called the cnidosacs. Cnidosacs store stinging cells (called nematocysts). These are obtained from their food source which are often cnidarians like hydroids, sea-anemones and soft corals. The cnidosacs are activated when the nudibranchs feel threatened and the stinging cells will be discharged!

All sea slugs have rhinophores. On the head of all sea slugs you can find a pair of sensory tentacles called the rhinophores. They detect smell and taste and in most of the dorid nudibranchs the rhinophores can be retracted into a basal sheath. Sea slugs know all kind of shapes of rhinophores which are a very important tool for identification of the species.

Diversity of sea slug rhinophore shapes

Besides a pair of rhinophores many nudibranchs also have a pair of oral tentacles, one on each side of the mouth. They are most likely involved in identifying food by taste and touch.

Sea slugs also need to breathe oxygen. They do this via the surface of their entire bodies, but their main reparatory organ are their gills. Dorid nudibranchs have often a feather like structure encircling their anus on the back of their body (the branchial plume). Some dorid species can also retract their gills into a pocket. Within the aeolid nudibranchs the cerata act like gills by diffusing oxygen from the surrounding water. The cerata are sometimes branched in order to increase the surface area, also here, like the rhinophores, different species can have different forms of cerata.

Diversity of aeolid cerata shapes

-Cessa