[7] This method of symbiont acquisition can be an evolutionary costly trait, as changing environmental conditions may impact the availability or functionality of these symbiotic bacteria.

The genus Oligobrachia has evolved specialized cells that provide a habitat for the endosymbiotic bacteria on which the tube worm relies for survival.

Depending on the habitat where Oligobrachia resides—whether near a hydrothermal vent or an undersea volcano—the endosymbiotic bacteria oxidize methane, sulfide, or other dominant chemicals present in the water.

The lack of diversity observed in the nervous systems of the studied tubeworms may provide insights into the evolutionary origin of the genus Oligobrachia.

It has been hypothesized that the trophophore develops in response to the needs of these bacteria, which rely on this feature of the tubeworm’s internal anatomy to perform metabolic processes that Siboglinidae cannot carry out on their own.

As previously mentioned, Siboglinidae lack a mouth and gut, so the endosymbiotic bacteria perform these essential processes in exchange for a protected habitat.