The bacteria nourishes the worm by oxidizing sulfur from its surrounding environment, with one methanotrophic exception being Siboglinum poseidoni.

Frenulata are unique in that they all have a mid-trunk girdle, spermatophores, sparse peg-like chaetae, and a tube with the posterior end open.

[9][10] The tube serves to provide structure for this soft-bodied animal as well as place the organism in an optimal position to obtain nutrients.

[12] Despite that, the endosymbiotic bacterial diversity remains largely unknown due to their small size and difficult to reach habitats.

[13] There is evidence that they are symbiote-flexible, meaning they can utilize different species of bacteria in order to best adapt to their environments.