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Researchers discovered this species off the northeastern coast of Taiwan, collecting six specimens across four years. Why did it take so long? Between October and April, the sea turns cold and harsh, while typhoons buffet the coast between May and September. They could only dive — to depths between 18 and 30 metres (59–98 ft) — when the weather permitted.

This species gets its specific name, sesama, from the yellow and black spots that cover its entire translucent body like sprinkled sesame seeds. Between those spots, it’s also speckled with pretty, snowflake-like markings.

Fittingly for a “sesame seed sea slug,” the largest individuals recorded were only about as large as a single sesame seed. To be precise, measurements ranged from 0.9 to 2.95 millimetres or 0.035 to 0.1 inches. This is much smaller than other species in its genus, such as T. picta, which can grow to be up to 20 millimetres (0.8 in) long — six or seven sesame seeds.

Like most nudibranchs, T. sesama is a specialist predator, “specifically observed feeding on one species of bryozoan [a tiny colonial animal].”

Thecacera sesama was the seventh species described in its genus. Two other named Thecacera live alongside it, feasting on the same bryozoans, as well as a whole five species yet to be described.

Read more about this sesame seed sea slug here!

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

Endemic to the island of South Georgia, this species has uncharacteristically long legs and hindclaws for a pipit, which it uses to navigate the thick tussac grass and rocky shores where it hunts for dwarf spiders, bog beetles, and kelp flies (among other invertebrates).

It has evolved significantly thicker feathers than its more equatorial mainland relatives to provide insulation from the "Roaring Forties" and "Furious Fifties” — incredibly strong winds that whip across the Southern Ocean — and temperatures that, on average, hover around freezing.

During the breeding season, males perform spectacular aerial song displays, hovering high above the cliffs before parachuting down. There are also reports of “the bird's lark-like rising, fluttering, and lovely singing.” (Pagenstecher, 1884).

For two centuries, invasive brown rats and house mice (introduced by sealers and whalers) preyed on the pipit's eggs and chicks, pushing the species to take refuge on tiny offshore islets. However, following the world’s largest rodent eradication project — taking seven years to complete — the island was declared completely rodent free in 2018. The South Georgia pipit has reclaimed its island and the species is now listed as Least Concern by the IUCN.

Learn more about this pipit, and the operation that saved it from likely extinction, here!

Thecacera sesama is a new nudibranch species described on 11 May 2026. It measures less than 3 mm (0.1 in) long — about the size of a single sesame seed. This “sesame seed sea slug” is the first new addition to its genus in nearly three decades.

The South Georgia pipit (Anthus antarcticus) is the only songbird in the Antarctic region proper and the most southern-breeding of all 6,500+ passerine species. It survives extreme winds and freezing temps by sheltering in tussac grass, but was nearly wiped out by a rodent infestation.