Branching Worm Reveals Unique Genetic Blueprint Behind Unusual Reproduction.

In a remarkable leap forward in marine biology, scientists have decoded the complex reproductive genetics of Ramisyllis kingghidorahi, a highly unusual branching worm that resides within sea sponges in tropical waters. Known for its tree-like body structure, this marine invertebrate generates numerous tail-like branches, each capable of producing separate reproductive units called stolons.

Researchers from the University of Göttingen, in collaboration with international partners, have now mapped gene expression across various body regions and developmental stages of this creature. Their study, published in BMC Genomics, presents the first comprehensive transcriptome—or gene activity profile—of any branching worm, offering rare insight into how Ramisyllis orchestrates reproduction across its many limbs.

The team's analysis revealed that genetic differences were more striking between different parts of a single worm than between male and female individuals. Among all the regions studied, stolons—the short-lived segments that detach and swim off to reproduce—displayed the most distinct genetic activity between the sexes. This likely reflects their specialized roles in producing gametes and undergoing metamorphosis.

Contrary to earlier assumptions, the worm’s head did not show significant sex-specific genetic control. "We expected the head to regulate sexual differentiation," explained Dr. Guillermo Ponz-Segrelles, former researcher at the Autonomous University of Madrid, "but our data point to the stolons as the central hubs of reproductive gene expression."

A particularly intriguing finding was the discovery that stolons develop eyes before detaching to seek mates. Genes related to eye development were found to be highly active during this phase, shedding light on how parts of the worm's body transform into free-swimming reproductive entities.

The study also hinted at partial genome duplication within Ramisyllis, a factor that may contribute to its reproductive and anatomical complexity. While identifying familiar genetic signaling pathways proved difficult, the findings suggest this worm possesses a unique molecular toolkit that sets it apart from other marine invertebrates.

"This animal continues to astonish us," said Ph.D. researcher Thilo Schulze. "It forces us to rethink what’s possible in animal body organization and reproduction."

With much still unknown about branching worms, the researchers hope their genetic map will pave the way for further exploration into the evolutionary wonders hidden beneath the ocean’s surface.

Source:https://phys.org/news/2025-05-tails-worm-reproductive-complexity.html

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