What Makes a New Species a New Species?

In the last decade, Academy scientists and research affiliates have described nearly 2,000 new species, ranging from tiny sea slugs to flowering plants and never-before-seen deep-sea coral reef fishes. This year, 26 researchers across five fields described 153 new species, including 19 new species of flattie spiders from Australia and 20 new nudibranchs, or sea slugs.

2023 also marks the fiftieth anniversary of the Endangered Species Act (ESA), a federal framework for protecting threatened and endangered plants, animals, and their habitats. As Academy researchers search for rarely seen animals and plants during field work, they are also looking for species that might need more protection. A handful of the 153 newly described species are now under consideration for the International Union for Conservation of Nature’s Endangered Species List.

“Naming and describing species is the first critical step in knowing about them and protecting them in a meaningful way—it is the tip of the iceberg that sets us on a journey to understand their role in healthy ecosystems,” said the Academy’s Dean of Science and Research Collections Shannon Bennett, PhD. “Formally cataloging biodiversity also sets in motion codified processes for protection, from the species level (through the ESA) to the ecosystem levels (through designating sanctuaries or Marine Protected areas).”

The years researchers spend “in the field”—in the jungles of the Galápagos, on hikes through California’s Sierras, or in deep-water dives in the Indo-Pacific—helps them develop a near-encyclopedic knowledge of the animals and plants in a given area. The Academy’s Senior Curator of Invertebrate Zoology and Geology Terry Gosliner, PhD, is a taxonomic expert in nudibranchs who has found at least one new species every year since 2011. In 2023, Gosliner helped describe 20 new sea slug species hailing from the Atlantic and coral reef systems along the Indo-Pacific’s mesophotic (100-500 feet below the surface) regions.

How’s he so good at locating these teeny-tiny, millimeters-long sea slugs? Time, teamwork, and a ridiculously good memory.

“I was recently diving in Fiji, where I saw a tiny soft coral that looked like a button,” Gosliner said. “I remembered finding another sample like it in Guam, some 30 years ago—turns out, it was a new species and only the second time someone had seen this coral.”

When sifting through sand for new sea slugs, Gosliner says he keeps an eye out for strange spots, spikes, and unique patterns that might hint at a new or rarely seen species; but other factors like distribution and range can help researchers understand a given animal’s uniqueness and importance to a region’s ecosystem.

“There’s a lot of undocumented diversity out there, and insects and invertebrates are some of the most poorly studied animals there are,” Gosliner said. A historic lack of research into insects and invertebrates might just be behind the disproportionately large numbers of new species described in these fields: Since 2010, roughly 70% of the Academy's new species descriptions stem from entomology and invertebrate zoology.

Erdmann, a research associate at the Academy, said that his team was able to identify a new shrimp goby species (Tomiyamichthys elliotensis) after a lengthy group effort: Erdmann dove along the southern waters of the Great Barrier Reef to collect the tiny, spotted fish, while researchers Gerald Allen, PhD, and Christine Dudgeon, PhD, took those samples to the lab to count the animal’s scales, document its coloration, and study the shape of its teeth.

“Describing a new species is truly a collaborative process, and we often involve a geneticist to test fin ray clips—that’s enough to do DNA barcoding, which helps us place animals on the tree of life,” Erdmann said. “It’s not always accurate, but it helps confirm the differences and unique traits that we can observe with our eyes, such as color or iridescence.”

DNA testing and genetics have become increasingly important tools in confirming new species descriptions. Nicknamed “barcoding,” scientists use this analogy to describe the process of analyzing tiny snippets of a specimen’s genes, much like a product barcode allows a retailer to distinguish one item for sale from the next.

At the Academy, researchers have used new species descriptions to fight for the protection of rare animals that are endemic to specific islands or oceans. The new arachnid described by Jain and Forbes marks the first-ever scorpion description where the IUCN’s evaluation for potential endangerment listing has been conducted at the same time as the new species’ publication. And Gosliner’s discovery of four new mesophotic sea slug species means that ocean conservation efforts should benefit both mesophotic and shallow water regions.

"We must document the Earth's living diversity so that we can work to protect it, and the California Academy of Sciences is honored to take part in this critical global effort," said Academy Executive Director Scott Sampson, PhD. "Additionally, we must aim beyond protection toward regeneration, boosting the health and resilience of ecosystems for future generations of humans and nonhumans alike. Here, too, the Academy is deeply engaged through our bold mission to regenerate the natural world.”