marine animals

Tiny sesame sea slug species discovered in the waters of northern Taiwan

This tiny nudibranch, which measures less than three millimetres in length, was first spotted by lead author Ho-Yeung Chan during a recreational dive in 2019.

Translucent, speckled, and barely the size of a grain of rice, a new species of sea slug has been identified in the coastal waters of Keelung, Taiwan. Because of its minute size and distinctive black and yellow markings, researchers from National Taiwan Ocean University, National Museum of Natural Science and National Taipei University of Education have named the creature Thecacera sesama.

“Taiwanese divers call it ‘sesame’ in Chinese and it is also small like a sesame seed, hence the name,” the research team explained regarding their decision to honour the local nickname in the scientific nomenclature. This tiny nudibranch, which measures less than three millimetres in length, was first spotted by lead author Ho-Yeung Chan during a recreational dive in 2019.

*Thecacera* *sesama* sp. nov. Details of appearance and morphological features, hand-drawn on a tablet PC by Chen-Lu Lee.

The discovery was a stroke of luck that began during Chan’s undergraduate studies:

“During a recreational dive in the summer during the undergraduate study of HY Chan in 2019, he accidentally discovered Thecacera sesama sp. nov. in northern Taiwan waters.”
The Research Team

Despite its unique appearance, the importance of the find was not immediately obvious. In a modern twist on traditional taxonomy, Chan “never realised Thecacera sesama was a new species until he consulted the sea slug expert ‘Hsini Lin teacher’ on Facebook.”

Living specimens of *Thecacera* *sesama* sp. nov. Image credit: Ho-Yeung Chan et al.

Documenting the species proved to be a significant logistical feat due to the volatile environment of the Keelung coast. The research team noted that the most challenging part of the study was the unique weather conditions of the region.

Taiwan experiences frequent typhoons in the summer and large waves during the winter monsoon season, with sea temperatures often dropping below 16 degrees Celsius. These factors mean that diving for nudibranch research is only possible for about four months of the year, making sightings of such tiny creatures entirely a matter of chance.

Living specimens of bryozoan with *Thecacera* species. Image credit: Ho-Yeung Chan et al.

The life of T. sesama is remarkably focused, as the researchers observed that the species exhibits only four primary behaviours: feeding, searching, mating, and laying eggs on bryozoans, which are tiny aquatic invertebrates often called “moss animals”. Interestingly, the specific bryozoan that T. sesama calls home may itself be a species new to science.

From a broader ecological perspective, these vibrant molluscs play a vital role in the marine environment:

“Nudibranchs are one of the key players in the marine food web. They are extremely colourful and can be spotted on coral reef ecosystems. However, many nudibranchs are very small in size and are extremely difficult to spot underwater with the naked eye.”
The Research Team

The researchers believe that the discovery of T. sesama is just the tip of the iceberg for Taiwanese marine biology. Because many species are so small, many more are likely awaiting discovery and formal study. The full research on Thecacera sesama was published in the open-access journal ZooKeys on 11 May 2026.

Original source:

Chan H-Y, Lee C-L, Chen W-C, Chang C-H, Shao Y-T, Pang K-L (2026) Thecacera sesama sp. nov. (Nudibranchia, Polyceridae) from Taiwan, evident from morphology and phylogenetic analyses of the 16S rDNA and cytochrome c oxidase I gene. ZooKeys 1279: 269-284. https://doi.org/10.3897/zookeys.1279.184298

Cover image:

Two individuals of Thecacera sesama sp. nov. feeding on a bryozoan. Image credit: Ho-Yeung Chan et al.

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The Internet Names a New Deep-Sea Species, Senckenberg researchers choose a scientific name from over 8,000 suggestions

A new deep-sea chiton has been officially named by the public and described in the Biodiversity Data Journal. The name is the result of a viral, week-long collaboration between science communicator Ze Frank, Senckenberg, and Pensoft Publishers.

The Senckenberg Ocean Species Alliance (SOSA), in partnership with the scientific publisher Pensoft Publishers and famous science YouTuber Ze Frank, have let the Internet name a newly discovered deep-sea chiton (a type of marine mollusk). The formal description of the species was published today in the open-access Biodiversity Data Journal.

From over 8,000 suggestions submitted via social media, the research team responsible for describing the species selected the name Ferreiraella populi. The specific epithet populi is a Latin singular noun in the genitive case meaning “of the people”. Curiously, the name was independently suggested by 11 different contributors during the naming contest.

From a YouTube video to Taxonomy

It all began when Ze Frank featured the rare deep-sea chiton (genus Ferreiraella) in an episode of his “True Facts” YouTube series.

Equipped with an iron-clad radula (a rasping tongue) and eight protective shell plates, the chiton also hosts a tiny community of worms near its tail that feed on its excrements. Everyone was invited to propose a scientific name and justification; within a week the community responded with over 8,000 name suggestions.

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“We were overwhelmed by the response and the massive number of creative name suggestions!” says Prof. Dr. Julia Sigwart, co-chair of SOSA at the Senckenberg Research Institute and Natural History Museum Frankfurt. “The name we chose, Ferreiraella populi, translates to “of the people”.

Other notable suggestions included Ferreiraella stellacadens meaning “Shooting star chiton” – named for its unique aesthete pattern and the fact that it “shot to fame” during the selection process.

Another was Fereiraella ohmu in reference to a chiton-like creature from Studio Ghibli, providing a nod to Japan, where the species was discovered.

A Specialized Resident of the Deep

Originally discovered in 2024 within the Izu-Ogasawara Trench at a depth of 5,500 meters, the new deep-sea chiton Ferreiraella populi belongs to the genus Ferreiraella, a rare and specialized group of mollusks that live exclusively on sunken wood in the deep sea.

Deep-sea sample extraction. Video Credit to Chong Chen/JAMSTEC

The new species represents an addition to a lineage of chitons that has been little researched to date and provides further evidence that deep-sea wood-fall ecosystems host highly specialized and still largely undiscovered communities,
explains Sigwart

Chitons are often described as a cross between a snail and a beetle. However, unlike common mollusks with a single shell, chitons possess eight separate shell plates (valves). This unique anatomy allows them to roll into a protective ball or cling to the irregular surfaces of deep-sea wood-falls.

Found in both warm coastal waters and coral reefs as well as the deep sea, chitons can live at depths of up to 7,000 meters under extreme conditions and in absolute darkness.

How is a scientific name formed?

Ever wonder how a creature goes from “that deep-sea thing” to a formal scientific entry? Every newly discovered species is assigned a scientific name as part of its original taxonomic description.

This follows Carl Linnaeus’s principle of binomial nomenclature and consists of two parts: the genus name (the first part, capitalized and italicised) and the specific epithet (the second part, lowercase and italicised).

The name is assigned by the author(s) of the first description in a scientific publication, adhering to international codes such as the ICZN (zoology) or the ICN (botany). The name must be novel, unique, and latinized. Usually, epithets are often derived from characteristics like color or size, geographic locations, mythology, or personal names used to honor a specific individual.

Ferreiraella populi in its natural habitat. Video credit to Chong Chen/JAMSTEC

Ferreiraella populi exemplifies the overwhelming biodiversity of the oceans, the vast majority of which remains unexplored. Many species go extinct before we even know they exist – this is especially true for marine invertebrates,
says Sigwart

“It can often take ten, if not twenty years, for a new species to be studied, scientifically described, named, and published. At SOSA, we have therefore made it our mission to streamline these processes while simultaneously engaging the public with these fascinating creatures. Finding a name for the chiton together on social media is a wonderful opportunity to do just that!” comments Sigwart.

“Ferreiraella populi has now been described and given a scientific name only two years after its discovery. This is crucial for the conservation of marine diversity, especially in light of the threats it faces such as deep-sea mining!” she says.

Research paper:

(SOSA) SOSA, Chen C, Frank H, Kraniotis L, Nakadera Y, Schwabe E, Sigwart JD, Trautwein B, Vončina K (2026) Ocean Species Discoveries 28–30 — new species of chitons (Mollusca, Polyplacophora) and a public naming competition. Biodiversity Data Journal 14: e180491. https://doi.org/10.3897/BDJ.14.e180491

In a hole in a tunicate there lived a hobbit: New shrimp species named after Bilbo Baggins

Two new species of tiny symbiotic shrimps are described, illustrated and named by biology student at Leiden University Werner de Gier as part of his bachelor’s research project, supervised by Dr. Charles H. J. M. Fransen, shrimp researcher of Naturalis Biodiversity Center (Leiden, the Netherlands).

Inspired by the extremely hairy feet of one of the species, the authors decided that they should honour Middle Earth’s greatest halfling, Bilbo Baggins.

Aptly named Odontonia bagginsi, the new shrimp joins the lines of other species named after Tolkien’s characters such as the cave-dwelling harvestman Iandumoema smeagol, the golden lizard Liolaemus smaug and the two subterranean spiders Ochyrocera laracna and Ochyrocera ungoliant.

The newly described shrimps were collected during the Ternate expedition to the Indonesian islands of Tidore and Ternate, organised by Naturalis Biodiversity Center and the Indonesian Institute of Sciences (LIPI) in 2009.

Typically for the Odontonia species, the new shrimps do not reach sizes above a centimetre in length, and were found inside tunicates. It is believed that these symbiotic crustaceans are fully adapted to live inside the cavities of their hosts, which explains their small-sized and smooth bodies.

Unlike most Odontonia species, which live inside solitary tunicates, the new species Odontonia plurellicola was the first one to be associated with a colonial tunicate. These tunicates have even smaller internal cavities, which explains the tiny size of the new species.

To determine the placement of the new species in the tree of life, the scientists compared the shrimps’ anatomical features, including the legs, mouthparts and carapace. As a result, they were assigned to Odontonia. Further, the available genetic information and Scanning Electron Microscope (SEM) images of the unusual feet of the newly discovered shrimp provided a new updated identification key for all members of the species group.

“Being able to describe, draw and even name two new species in my bachelor years was a huge honour. Hopefully, we can show the world that there are many new species just waiting to be discovered, if you simply look close enough!” says Werner de Gier, who is currently writing his graduate thesis at Naturalis Biodiversity Center and working together with Dr. Charles Fransen on crustaceans.

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Original source:

de Gier W, Fransen CHJM (2018) Odontonia plurellicola sp. n. and Odontonia bagginsi sp. n., two new ascidian-associated shrimp from Ternate and Tidore, Indonesia, with a phylogenetic reconstruction of the genus (Crustacea, Decapoda, Palaemonidae). ZooKeys 765: 123-160. https://doi.org/10.3897/zookeys.765.25277