When we think of molluscs, our minds often jump to common creatures like snails, clams, and squids—animals we encounter in gardens, beaches, or seafood restaurants. Yet beneath the ocean’s depths lies a peculiar, lesser-known group of molluscs that challenge our understanding of marine life: Solenogastres.
In a recent interview with Dr. Franziska Sophie Bergmeier, an Ocean Census taxonomic award recipient who specialises in Solenogastres, we learnt about the complexities and importance of studying these elusive animals. Her work not only sheds light on the fascinating biology of these molluscs but also highlights the innovative approaches being used to speed up species discovery.
Feature image: “A selection of different Solenogastres species that we found in the Northwest Pacific, from around 2000m down to almost 10,000m. The photos of the animals are not to scale, some of the Solenoagstre are only 1.5 mm in length, while other are almost 6cm long”.
“Here I am in the lab collecting very tiny species of Solenogastres (smaller than 1 mm) from a sand sample.”
The Streamlined Approach to Species Identification
Could you please tell us about the background to your work?
Dr. Franziska: The molluscs I study, called Solenogastres, are strange and hard to identify. Unlike gastropods or bivalves where the shell offers clues, these animals need to be studied internally. I section the animals, using their middle part for DNA extraction, and analyse their anterior and posterior sections for taxonomic characters in their digestive and reproductive systems. This combination of external features, anatomy, and molecular data allows me to describe new species, but it’s a lengthy process.
During my PhD, I identified about 80 new species, and a full description for each would take about seven years, which is impractical. So, I’ve developed a streamlined approach using light microscopy, scanning electron microscopy, and DNA barcoding to quickly delineate species. This helps integrate them into existing classifications without going through the full anatomical study.
Your approach was motivated by the need to streamline, but also by the uniqueness of these molluscs?
Dr. Franziska: Exactly. These animals are frequently collected, not in large numbers but consistently across different ocean zones. Their unique characteristics and the complexity of traditional taxonomic methods have deterred study. My goal was to find a balance where I could efficiently characterise species without the exhaustive full description every time.
Applicability of the Streamlined Approach in Taxonomy
Do you think this method can be applied to other areas of taxonomy?
Dr. Franziska: The process is already being streamlined in other groups like small invertebrates and insects. My approach is particularly suited to Solenogastres because the middle section has no taxonomic value, and we’ve developed specific barcoding primers for them. Streamlining is becoming more common across taxonomy as researchers aim to tackle the overwhelming number of undescribed species.
Solenogastres Specialisation and Taxonomy
Do you specialise in a subgroup of Solenogastres or a specific location?
Dr. Franziska: I’m broadly interested in Solenogastres. I focus on taxonomy because it’s the foundation for understanding species diversity, biology, and evolution. Without a solid taxonomic basis, it’s difficult to explore these bigger questions.
“A scanning electron microscopy (SEM) picture of a new species collected in Antarctica. In this photo you can really nicely see the aragonitic sclerites that cover the body. This animal is about 1.7 mm in length.”
Importance of Studying Solenogastres
Since Solenogastres aren’t widely known, why should we care?
Dr. Franziska: Aside from their evolutionary significance, these animals help us understand ecosystem health and biodiversity. While small and overlooked, they’re part of a broader conservation picture, and studying them can reveal unique adaptations. The public often finds their deep-sea habitat and strange appearance fascinating. People are often interested in their strange appearance and the fact that they provide clues to mollusc evolution. Conservation efforts tend to focus on larger, well-known species, but tiny invertebrates like these are crucial for a more holistic understanding of ecosystems. Public interest helps raise awareness of their importance.
Ecological Role of Solenogastres
Do we know much about the ecological role of Solenogastres?
Dr. Franziska: We’re just beginning to understand them. Recent research shows that they are highly specialised feeders in the deep sea, preying on specific organisms like bivalves or annelid worms. This makes them important to study, especially in terms of conservation, as their food sources may affect their distribution and survival.
Time Required for Species Descriptions
How long does a full Solenogastres species description take?
Dr. Franziska: A full workflow, including DNA extraction and 3D anatomical reconstructions, can take 3-4 months, depending on the species’ size and how familiar I am with its genus or family. If I am not familiar with the species, then it can take up to 5-6 months. That’s why streamlining is essential to handle the high number of undescribed species.
“This is a high magnification SEM image of the needles of such an animal. The scale bar of 10 µm (that’s 0.01 mm) really highlights how tiny these structures are.”
Hotspots for Species Discovery
Where are the hotspots for discovering new Solenogastres species?
Dr. Franziska: We don’t know enough yet, but many species of Solenogastres seem to be found in the lower bathyal zone (2,000-3,000 metres deep). We’ve also found some at the bottom of oceanic trenches. Over the next few years, I hope we’ll have a clearer picture of where these animals are most abundant.
Impact of the Ocean Census Award
How will the Ocean Census taxonomy award help with your work?
Dr. Franziska: It provides the opportunity to work with a broad range of Solenogastres collected from different environments and depths, building a robust dataset. This baseline data will help us better understand species distribution and diversity.
“That’s me during a research cruise to the Japan trench, ready to collect more Solenogastres from the deep sea.”
The Unsung Heroes of the Deep Sea
While Solenogastres may not be as well-known or glamorous as other marine species, their importance to science and conservation cannot be understated. Dr. Franz’s research demonstrates how these strange, tiny molluscs can unlock new understanding of marine ecosystems, biodiversity, and evolutionary history.
In a world where so much of the ocean remains unexplored, the study of Solenogastres reminds us that even the smallest and most obscure creatures play a vital role in our planet’s biodiversity.
Keep up to date with other stories from the Ocean Census award winners.
