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Comparing Squid Upper and Lower Beak Function: Puncturing vs Drawing

Cephalopods are a diverse class of mollusks that utilize an equally diverse arsenal of techniques and weaponry that support their predominantly occupied niche as opportunistic predators. These predators are manipulatory feeders; renowned for their sucker-studded arms and tentacles. This retrieving embrace envelops prey to utilize a devastating beak that pierces flesh, scale, and shell. The cephalopod’s beak consists of a pair of chitinous mouth parts operated by a complex of muscles called the buccal mass whose flexible pivot is a new field of research. The novelty of the cephalopod beak’s joint-type compounds further with its lack of inorganic components usually used by organisms to make inflexible structures such as calcium in teeth. Instead, a layer of buccal cells excretes only organic components to form the beak which follows a rigid gradient using chitin and proteins like pigment. The shapes of cephalopod beaks of many species are well documented but subsequent deviations in upper and lower functions call for more research. Cephalopod beaks maintain commonality in component structures which produces results applicable between species. The puncturing and drawing abilities of longfin inshore squid's upper and lower beaks were determined by applying vertical and lateral performance tests to their beaks, using a “universal testing machine” to measure beak efficiency. Efficiency in beak elasticity was measured through differing limits the beaks experience when biting prey. This model produced force-displacement traces whose respective peaks indicated each point of maximum resistance. This experiment suggested the physiological roles in the feeding process of longfin inshore squid’s bipartite beaks and the species’ ecological niche.

Sean Clancy '24
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