Experiments-Structure-Property Relations of Paddlefish Cartilage

Abstract

Figure 1 Paddlefish rostrum showing specimen sample locations.

Figure 2 Schematic of sectional areas studied.

Table 1 Summary of the average elastic modulus (GPa) and standard deviation for the assessed sections.

The rostrum, or nose, of the paddlefish is a unique structure composed of a network of cartilage, tissue, and interlocking star-shaped bones called stellate bones. The stellate bone properties of the rostrum are examined as a function of spatial location along the midline and the edge of the rostrum using nanoindentation.

Materials

The Live specimens of P. spathula were held at the Environmental Laboratory of the U.S. Army Engineer Research and Development Center (ERDC). They were anesthetized and euthanized, and the rostrum was removed according to the ERDC animal care guidelines (#EL-6009-2011-5), which encompasses the NIH Guide for Care and Use of Laboratory Animals. A phosphate-buffered saline (PBS) solution was used to maintain hydration during storage. A 695-mm-long fish according to Eye-to-Fork length measurements, with a total rostrum length of 310 mm as shown in Figure 1 provided the specimens for these analyses.

Methods

Cylindrical segments were cored and stellate bones were separated from the surrounding tissue as seen in Figure 1. Specimens were cleaned and mounted for preparation in nanoindentation.

Results

The paddlefish rostrum was assumed to be symmetric with respect to the centerline, i.e. the left and right sides of the rostrum will have the same mechanical properties. By characterizing the segments shown in Figure 2, the elastic modulus gradient across the rostrum was obtained. The summarized elastic modulus results are shown in Table 1. An average elastic modulus 12.06 GPa ± 0.68 was measured on the middle segment.