WINDY WEIRDOS – NEW INSIGHTS TO THE SPIRULA SHELL
A total of 336 Spirula shells were collected from the east-coast of Fuerteventura, Canary Islands, Spain to analyze their morphology, floating behavior, and infestation by epibionts. 3D models were obtained by x-ray micro-computed tomography scans to assess the shell’s floating capability.
Data show that more than 80% of the shells are infested by the goose barnacle Lepas. In most cases, multiple Lepas were found on a given Spirula shell. In some cases, the shell of Spirula is infested by up to 17 Lepas, which can grow over 2 cm in length. Even though the accumulation of Lepas on Spirula shells increases the weight, the shells are capable maintaining their floating ability. Micro-CT analyses indicate that Spirula possesses a light-weight shell which, together with the large gas-filled volume, enhance buoyance ability. In addition, the morphological layout of the siphuncle function as an air-lock mechanism after the death of an individual which further enabling the shell to be a reliable floating device.