Image: Branchiomma arcticum (Ditlevsen, 1937)
Family Sabellidae: Branchiomma arcticum (Ditlevsen, 1937). (Specimen from the White Sea, photographed alive in the laboratory).
- Alexander Semenov
- © Alexander Semenov
The photographer is looking down into the base of the whorl of feeding tentacles (or “branchial crown made up of numerous filaments”) of this ’fan-worm‘, where the pinkish lips are splayed out in order to direct food particles collected at the base of each filament of the crown to the mouth. The crown is held up into the water column and hairs (“cilia”) along each filament create water current which flows through the filaments, trapping food particles and carrying them to the lips at the base. Small light-sensitive pigmented spots along the branchial crown alert the worm to passing shadows of potential predators and the animal responds rapidly by retracting back into its tube. Like calcareous tube worms, sabellid fan worms can rapidly regenerate their branchial crowns, which are often colourful and are also used for respiration. This rapid regeneration is critical as without the crown the worm can neither feed to respire. These animals can reach lengths of 5- 6 cm.