Overview
- The new species was formally described as Thecacera sesama in the journal ZooKeys and reported by multiple outlets on Tuesday, May 26, 2026.
- The slug measures under 3 millimeters long, is translucent white with many black spots and a few larger yellow spots, and bears five gills.
- Researchers collected specimens at 18–30 meters in Mother Rock Bay across repeated dives from May 2021 to June 2025 and used detailed morphology plus DNA (16S rDNA and COI) to place it in Thecacera.
- Field teams observed the animal feeding, searching, mating, and laying eggs exclusively on a single bryozoan species, and they report that the host bryozoan may itself be undescribed.
- Surveying is limited by rough seasonal weather on Taiwan’s Keelung coast, which restricts diving to a few months a year and suggests many similarly tiny, cryptic marine species remain to be discovered.