Tag Archives: bristle worm

Reproduction is laborious for certain marine worms

Published September 3, 2016 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2016 Susan Scott

These palolo worm relatives are called green paddle worms, common in eastern and northern Australia. Green paddle worms keep their sex cells to themselves, each segment making and shedding its own gametes. ©2016 Susan Scott

Labor Day marks the unofficial end of summer, the beginning of school, the kickoff of the football season and, where I grew up, the last day of the year that it was acceptable to wear white (go figure).

Those associations with the holiday became secondary to me when I was 11 years old because my mother went into labor on Labor Day, turning our picnic into pandemonium and resulting in a baby brother. Since then Labor Day has symbolized the production of offspring.

In mammals, reproducing is pretty straightforward, but for some marine invertebrates, getting eggs and sperm hooked up is more complicated.

Take a type of bristle worm called palolo worm. (Fijians call them “mbalolo,” hence the common name, palolo.) Palolo worm bodies can have up to 1,000 segments, totaling 16 inches in length. Each segment has two feet, and each foot bears gills, meaning the worms breathe though their feet.


With toes for scale. ©2016 Susan Scott

Sensory tentacles around the worm’s head help it find tiny living animals to eat. But don’t look for palolo worms hunting during a morning or afternoon snorkel. The creatures hate bright light and come out of their coral rock homes only at night. If you’re in the right place at the right time, though, you might see these worms have sex.

Each year palolo worms grow from their tail ends tubelike sacks filled with eggs in females and sperm in males. In Fiji and Samoa, on the seventh night after the full moon that follows the autumnal equinox (Sept. 22 this year), the worms cast off their packages of precious cells.

The released sex packs have paddle feet on the sides. Light-sensitive eyes running along the midlines guide the paddlers toward the starlit surface. Once there, the gamete tubes twist and twirl until dawn. Sunlight causes the packets to burst open like a milkweed pod, releasing the eggs and sperm to do their job of making more worms.

At least 14 species of palolo worms live throughout the world’s warm oceans, including Hawaii. The sex cell sacks of our worms, however, don’t all rise in one day, but swim up throughout the summer. I’ve seen them under the nighttime dock lights in Kaunakakai Harbor.

Some residents in Fiji and Samoa consider the green gonads a delicacy. People wade out with nets to catch the wigglers near the surface before they explode, and then prepare an annual feast. Some Indonesians also collect and cook palolo worms’ procreative packets.

Because one way or another, moms and dads work their rear ends off for their young, my Labor Day thoughts are with parents. I hope your picnics are peaceful.