From Guppy to Gollum – in Search of New Fish Species

We have been invited to an interview with Dr. Ralf Britz. He has been working as Section Head of Ichthyology at Senckenberg Natural History Collection Dresden (SNSD) since 2019. His research focuses on the anatomy, taxonomy, systematics, and biogeography of fishes, in particular freshwater fishes from tropical regions. How do you introduce a man whose eyes began to sparkle when he looked at his aquarium as a seven-year-old and who has contributed to the description of 83 new fish species, seven new genera, and two new fish families to date?

Britz welcomes us to the quiet Adolf Bernhard Meyer Building, the depot and administration building of the Museum of Biodiversity, with a small smile in his eyes. Surrounded by dry fish skeletons prepared with the help of dermestid beetles, cow-nose rays stored in glycerin, aquariums, countless fish specimens, books and microscopes, his eyes are still shining. Every little fish, no matter how small, arouses his interest and his urge to explore. And we are already infected as we join him on a dive in search of new species.

“When you grow up in a village of 2,000 in Saarland, fishes can be extremely exciting,” Britz says with a smile. He had his first aquarium at the age of seven and since then he has been fascinated by these silent creatures. He wanted to know more about them. So after school he studied biology in Tübingen, initially trying his hand at genetics. “But things that I can’t see and touch quickly lose their fascination for me,” he explains. So he switched to anatomy. That was when he bought his first ZEISS stereo microscope specifically for observing fish – in 1985. He had found his calling. And although many other microscopes have followed, this one has always had a special place in his office. And it still works today.

“I’m drawn to the tropics. The Kerala region in southwest India is particularly interesting,” Britz states. The fish fauna there is unique and it’s a real biodiversity hotspot, with over 300 freshwater fish species. And new species are being discovered all the time – a mecca for fish researchers like him.

What is exciting about these local heroes are their as yet unknown phylogenetic relationships and their unique anatomical features, which are also known from troglobionts - a species or population of a species strictly bound to underground habitats.  Basically, we still know precious little about troglobiont’s lifestyle, diet, reproduction, and relationships. This is due to their habitat: underground caves are difficult to access.

It’s not just subterranean fishes that fascinate Britz, but also those endemic in rivers. Endemic means that a species is limited to a small geographic area and can therefore be found naturally in this place, e.g. polar bears or Galapagos giant tortoises. The vulnerability of endemic animals and plants is enormous due to smaller populations. They are key to their ecosystems and become a thermometer to measure the health of an area. For that reason, their protection from extinction threats is critical. Endemic species are interesting because they often contain new species. A species may have been thought to be widespread, but closer examination often reveals that it is actually several species with restricted ranges, endemics.

“When you see a fish and think: What the hell is that? No idea of its family, a living fossil. That’s how I felt when we discovered the Gollum snakehead,” Britz remarks. Unlike other snakehead species, this fish does not breathe air.

Danionella dracula was also a real highlight for Britz. D. dracula belongs to the carp family, i.e. toothless fish. But it has teeth. Using an electron microscope, the group got to the bottom of this anatomical peculiarity. They were able to see that these are in fact extensions of the jaw bones, which only male D. dracula use for territorial fights and mating – this can be compared to the function of antlers in deer. “Speaking of the Danionellas, the discovery and specification of D. cerebrum was like exciting detective work,” Britz reports. For many years it was confused with its close relative D. translucida. D. cerebrum originates from Burma and has no skull roof; the brain is exposed under the transparent outer skin. This is particularly exciting for neurologists. This is why D. cerebrum is now a model organism.

The knowledge they gained from these unique images is enormous: They were able to describe another new troglobiont species and now hope to gain new insights into the anatomy and evolution of this newcomer. “It is also exciting to see what relationships there are to other troglobionts on distant continents. This taxonomic work will feed into further studies on the biogeography of these highly interesting regions of Asia. So it remains exciting,” Britz observes.