Jon Allen still remembers the moment a three‑foot‑long ribbon worm slid across a bowl in a classroom and stole the show. The worm—affectionately nicknamed Baseodiscus the Eldest, or simply “B”—has been quietly living in tanks and lecture demos for decades. What began as a humble teaching specimen has just become a record‑breaker: genetic tests and a careful review of its history show B is the oldest ribbon worm (phylum Nemertea) known to science, with a conservative age estimate in the mid‑to‑late 20s and a reasonable possibility it’s around 30 years old.
An accidental long‑term study
B wasn't collected as part of a longevity experiment. According to William & Mary biologist Jon Allen, the animal arrived in his care after renovations displaced a tank at another university; Allen took it in around 2005. The worm was already adult size when first documented, and researchers later learned it had been collected from the San Juan Islands in the late 1990s. That multi‑decade trail—plus a 2024 genetic check that identified B as Baseodiscus punnetti—allowed scientists to put a lower bound on its age: at least 26–27 years, and likely older.
Scientists had long suspected some nemerteans might live long lives, but most lab records and field notes suggested lives measured in months or a few years. B changes that narrative dramatically; it increases known lifespans for the entire phylum by an order of magnitude. In practical terms, that means many species long labeled as ephemeral predators on the seafloor may actually be stable, long‑lived players in benthic food webs.
Allen and his colleagues published their findings in the Journal of Experimental Zoology after a former student, Chloe Goodsell, prompted a genetic appraisal. Svetlana Maslakova and other specialists confirmed the species ID and helped put the timeline together.
Why it's hard to age a worm
Ribbon worms mostly lack the hard internal structures (bones, growth rings, calcified shells) that make aging straightforward in many animals. Some nemerteans have a tiny calcified stylet used in prey capture, but that’s absent in Baseodiscus punnetti, so researchers can’t use a simple structural clock. Instead, B’s value comes from continuity: it was kept alive and accounted for across jobs, states, and classrooms for decades. That continuity produced the best evidence scientists have for multi‑decadal life in this group.
The discovery is more than a curious factoid. If nemerteans routinely live for decades, their ecological role—how they shape prey populations, interact with predators, and structure benthic communities—needs rethinking. A long‑lived predator has different population dynamics and resilience than a short‑lived one, which matters for everything from local conservation assessments to experimental designs in marine ecology.
A broader fascination with marine giants
Ribbon worms already fuel our imagination: one stranded specimen found in Scotland in 1864 was reported to stretch to around 180 feet, rivaling blue whales in length. Those dramatic extremes remind us how much remains unknown about marine invertebrates. Popular culture and games frequently tap into that fascination with oversized or oddly long‑lived sea creatures—an idea that even sneaks into how developers frame underwater worlds in titles like Konami’s octopus platformer Darwin’s Paradox.
For scientists, B is a useful anchor point. Having a confirmed, decades‑old nemertean in hand lets researchers start to ask targeted questions about physiology and senescence in worms—what cellular mechanisms support extended life, and whether those mechanisms are shared across other long‑lived marine invertebrates. These are the kind of considerations that also inform how simulation and management models treat animal lifecycles; think of the detail that animal‑management games bring to lifespans and ecosystem balance in projects like the upcoming Planet Zoo sequel.
A well‑travelled teaching specimen
Over its documented life with Allen, B has been shipped from Washington to North Carolina to Maine and finally to Virginia, where it lives at William & Mary and still makes annual appearances in classroom labs. Allen describes Baseodiscus as “gorgeous,” with flexible, smooth skin and a deep red color—traits that make it an easy ambassador for a group of animals most people never notice.
The team behind the paper emphasizes that B’s story was partly serendipity and partly the result of multiple people over years keeping good notes. There are likely other long‑lived nemerteans out there; we simply haven't had many opportunities to follow individuals long enough to know.
This kind of patient observation—keeping an eye on a single, unassuming animal through job moves and syllabus changes—offers a reminder: in biology, sometimes the most revealing experiments are the ones that happen when curiosity meets continuity.
(Study published in the Journal of Experimental Zoology.)