Burrowing Into The Bobbit Worm’s Behavior

Using trace fossils, scientists have reconstructed the 20-million-year-old lair of giant marine worms in northeast Taiwan, providing insights into the predator’s behavior.

AsianScientist (Jan. 22, 2021) – Ancestors of the giant ambush-predator Bobbit worm may have colonized the Eurasian seafloor around 20 million years ago, discovered researchers from Taiwan. These findings were presented in Scientific Reports.

In 1993, a Mrs. Lorena Bobbit rose to infamy for castrating her abusive husband with a kitchen knife. While the case is now largely forgotten, Mrs. Bobbit’s memory lives on—in the form of the giant Bobbit worm, which can grow up to three meters long.

A fearsome predator typically found burrowed in the seafloor, the Bobbit worm ambushes unsuspecting prey with its powerful, scissor-like jaws. The still-living prey is then dragged down into the burrow for the Bobbit worm to begin its feast.

Though predatory marine worms have existed since the early Paleozoic period—around 540 million years ago—their bodies are mainly made up of soft tissue and are therefore rarely preserved in the fossil record. Without a fossil, it is difficult to study the Bobbit worm’s behavior within its burrows.

Instead of looking for preserved remains, researchers led by National Taiwan University’s Dr. Ludvig Löwemark took an indirect approach. Similar to footsteps imprinted on wet cement, trace fossils are impressions left by organisms in geological features like rocks. By examining seafloor layers in northeast Taiwan dating back to the Miocene—23 to 5.3 million years ago—the team reconstructed a new trace fossil, an L-shaped burrow roughly two meters in length.

The trace fossil, which they named Pennichus formosae, indicates that the burrows were likely inhabited by giant marine worms like the Bobbit worm. According to the authors, the fossil’s distinct feather-like structures may have been caused by disturbances in the sediment caused by flailing prey.

A vertical view of Pennichus formosae, showing signs of disturbed sediment and feather-like structures. Photo credit: Ludvig Löwemark.

Further analysis revealed a high concentration of iron in the burrow’s top section. Interestingly, bacteria that feed on mucus produced by marine invertebrates are known to create iron-rich environments. Because of this, Löwemark and his colleagues suggest that after consuming its prey, the worm likely re-built its burrow by secreting mucus.

The trace fossil described in the study is the first of its kind produced by a sub-surface ambush predator like the Bobbit worm—providing a rare glimpse into the behavior of these creatures beneath the seafloor.

“The interpreted activities of the Pennichnus trace maker records a life and death struggle between predator and prey, and indirectly preserves evidence of more diverse and robust paleo-ecosystem than can be interpreted from the fossil and trace fossil record alone,” concluded the authors.

The article can be found at: Pan et al. (2021) The 20-million-year Old Lair of an Ambush-predatory Worm Preserved in Northeast Taiwan.


Source: Nature; Photo: Sassa Chen.
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