TY - JOUR

T1 - Five hundred million years to mobility

T2 - directed locomotion and its ecological function in a turtle barnacle

AU - Chan, Benny K. K.

AU - Wong, Yue Him

AU - Robinson, Nathan J.

AU - Lin, Jr-Chi

AU - Yu, Sing-Pei

AU - Dreyer, Niklas

AU - Cheng, I-Jiung

AU - Høeg, Jens T.

AU - Zardus, John D.

PY - 2021

Y1 - 2021

N2 - Movement is a fundamental characteristic of life, yet some invertebrate taxa, such as barnacles, permanently affix to a substratum as adults. Adult barnacles became 'sessile' over 500 Ma; however, we confirm that the epizoic sea turtle barnacle, Chelonibia testudinaria, has evolved the capacity for self-directed locomotion as adults. We also assess how these movements are affected by water currents and the distance between conspecifics. Finally, we microscopically examine the barnacle cement. Chelonibia testudinaria moved distances up to 78.6 mm yr(-1) on loggerhead and green sea turtle hosts. Movements on live hosts and on acrylic panels occasionally involved abrupt course alterations of up to 90 degrees. Our findings showed that barnacles tended to move directly against water flow and independent of nearby conspecifics. This suggests that these movements are not passively driven by external forces and instead are behaviourally directed. In addition, it indicates that these movements function primarily to facilitate feeding, not reproduction. While the mechanism enabling movement remained elusive, we observed that trails of cement bore signs of multi-layered, episodic secretion. We speculate that proximal causes of movement involve one or a combination of rapid shell growth, cement secretion coordinated with basal membrane lifting, and directed contraction of basal perimeter muscles.

AB - Movement is a fundamental characteristic of life, yet some invertebrate taxa, such as barnacles, permanently affix to a substratum as adults. Adult barnacles became 'sessile' over 500 Ma; however, we confirm that the epizoic sea turtle barnacle, Chelonibia testudinaria, has evolved the capacity for self-directed locomotion as adults. We also assess how these movements are affected by water currents and the distance between conspecifics. Finally, we microscopically examine the barnacle cement. Chelonibia testudinaria moved distances up to 78.6 mm yr(-1) on loggerhead and green sea turtle hosts. Movements on live hosts and on acrylic panels occasionally involved abrupt course alterations of up to 90 degrees. Our findings showed that barnacles tended to move directly against water flow and independent of nearby conspecifics. This suggests that these movements are not passively driven by external forces and instead are behaviourally directed. In addition, it indicates that these movements function primarily to facilitate feeding, not reproduction. While the mechanism enabling movement remained elusive, we observed that trails of cement bore signs of multi-layered, episodic secretion. We speculate that proximal causes of movement involve one or a combination of rapid shell growth, cement secretion coordinated with basal membrane lifting, and directed contraction of basal perimeter muscles.

KW - movement ecology

KW - adhesive locomotion

KW - optimal foraging

KW - behaviour

KW - sea turtle

KW - Chelonibia testudinaria

KW - CHELONIBIA-TESTUDINARIA

KW - CEMENT PROTEINS

KW - REATTACHMENT

KW - EVOLUTION

KW - MOVEMENT

KW - ADHESION

KW - BALANIDAE

U2 - 10.1098/rspb.2021.1620

DO - 10.1098/rspb.2021.1620

M3 - Journal article

C2 - 34610769

VL - 288

JO - Proceedings of the Royal Society B: Biological Sciences

JF - Proceedings of the Royal Society B: Biological Sciences

SN - 0962-8452

IS - 1960

M1 - 20211620

ER -