Meeting Abstract

P3.179  Friday, Jan. 6  Feeding biomechanics in billfish: Inferring the role of the rostrum from a mechanical standpoint HABEGGER, M.L*; MOTTA, P.J; MULLINS, G; STOKES, M.J; WINTERS, D; University of South Florida

Billfishes are a group of large pelagic predators that are characterized by the elongation of both premaxillary bones forming the bill or rostrum. Besides the relevance of this structure, from which the group’s name is derived, its biological role is still controversial. Therefore, the goal of this study is to investigate the biomechanical role of the bill for feeding. Our main hypothesis suggests that if the bill is designed for striking its prey during feeding, there should be a homogenous distribution of stress along the structure. By using beam theory as our primary model and from the application of strain gauges along the bill, mechanical testing were performed in two individuals of Xiphias gladius , at two different planes. Mechanical parameters including stress, strain, Young’s modulus, flexural stiffness, second moment of area were then estimated. Additionally, histological samples were obtained to characterize the components of the rostrum. Preliminary results show that the second moment of area increases towards the base of the bill, stress values along the bill varied from 2.2 - 1.7 Nmm2 and Young’s modulus varied from 6.4 to 16.5 GPa from the base to the tip of the bill. Histology revealed acellular bone as the main component of the rostrum, however hyaline cartilage and adipose tissue were also present at its base. Statistical analysis showed no significant differences among stresses along the bill, confirming our hypothesis The distribution and values of the mechanical parameters are discussed with regards to the feeding behavior of this species.