The Functional Morphology and Ontogeny of the Nuchal Retractor Muscle in the Atlantic Long-fin Squid (Doryteuthis pealeii)
The nuchal retractor muscle of the Atlantic Long-fin squid (Doryteuthis pealeii) appears to be multi-functional; i.e., it acts as a motor, strut, and brake during different locomotory behaviors. Previously, multi-function muscles have only been identified in vertebrates and arthropods, which makes muscle specialization in the nuchal retractor muscle of the squid particularly unique. My project involves an investigation of morphological differences in two putative muscle fiber types in the nuchal retractor muscle. Through paraffin-based histology, I have shown that the nuchal retractor muscle is obliquely striated and that there is a substantial difference in muscle fiber lengths within the nuchal retractor muscle. Furthermore, my analysis has shown that average cell area of muscle fiber cells is greater in the anterior regions of the nuchal retractor muscle. There are, however, more mitochondria-rich fibers in the posterior of the muscle; these fibers appear to be located around the periphery of the nuchal retractor muscle. Muscle fiber specialization would allow the squid to employ two different muscle fiber types to satisfy different mechanical roles. Lastly my research examined ontogenetic changes in the nuchal retractor muscle and has demonstrated that the nuchal retractor muscle is not present in newly hatched squid, but is present in juvenile squid.
Franklin and Marshall College Archives, Undergraduate Honors Thesis 2016
- F&M Theses Collection