Meeting Abstract

P1.140  Monday, Jan. 4  Mechanical properties of the hagfish egg capsule CLARK, A.J.*; SUMMERS, A.P.; Clemson University ; Friday Harbor Laboratories aclark7@clemson.edu

Hagfishes develop slowly within large eggs that normally function in environments of low temperatures, high salinities and pressures. To ensure embryonic survival, the egg capsule must withstand a suite of physical stresses while permitting transport of oxygen and waste. Therefore, the mechanical properties of hagfish eggs are important underpinnings to reproductive success. We performed quasi-static tensile tests to failure on the egg cases of the Pacific hagfish (Eptatretus stoutii) to determine strength and stiffness. Individual egg capsules were divided into four sections with each section corresponding to the mechanical property (strength or stiffness) and the direction of the applied load relative to the longitudinal axis of the egg (parallel or perpendicular). Data were collected from three batches of eggs originating from different animals. One batch included eggs contained within the ovary and the second and third batches consisted of deposited eggs (1 and 30 days old). All intact eggs were approximately 20 mm long, however the capsules of in utero specimens were less tan and lacked the polar anchor filaments present in deposited forms. Though mean strength (13.6 MPa), stiffness (14.3 MPa), and thickness (0.156 mm) were similar in both batches of deposited eggs, deposited eggs were significantly thicker, stiffer, and stronger than in utero eggs (thickness, 0.113 mm; strength, 8.5 MPa; stiffness, 3.5 MPa). Similar strength and stiffness in both directions relative to the egg’s longitudinal axis suggests an orthogonal alignment of reinforcing collagen fibers in the capsule. These data show that internally developing hagfish eggs undergo a substantial increase in thickness, strength, and stiffness associated with tanning prior to deposition.