We began by talking a little bit about squid and octopuses, and developing some research questions we wanted to answer. The specimens for dissection were earlier destined for restaurant use – longfins have been commercially harvested, and thanks to their fast growth and high reproductive rates are considered a sustainable dining choice (learn more about the sustainability of Longfin Squid as seafood here). We talked about the anatomical differences between squid and other, more familiar organisms. We discussed adaptations like statocysts that let squid replicate auditory perception. We discussed as a group some subjects that we all wanted to learn more about through the dissection, including squid senses and respiration.
And then the dissection began. Ben M. and I worked together with Zola and Ezra to answer two assigned research questions about how squids catch food and how they ingest and process it. Our instructor helped us by letting us know where certain parts of the squid were, where we might want to cut, and what we might want to take a closer look at under the microscope. It was an exciting and messy process, with split ink sacs and an accidental decapitation of one of the specimens. We conducted the dissections using metal probes, scissors and tweezers, and we were provided with squid anatomy charts that aided us in locating the squids' internal physiological features.
One of the squid's key predatory adaptations is its speed. Squid swim backwards, jetting along by releasing water from a siphon positioned at the anterior end of the body. Squid are able to seal off their mantle cavity, forcing the water out of the siphon. Wing-like swimming fins just from the posterior of the mantle, aiding in steering. While swimming, the decapodal squid conceals its two long, club-like tentacles within its eight arms. Once within striking range of a prey animal, the squid lashes out, ensnaring the poor creature in its tentacles and grasping it in its arms, laden with suction cups reinforced with calcareous sucker rings (we were able to remove and take a close look at some of our squid's sucker rings). The prey is passed off to the tearing, beak-like mouth, and bites of flesh are chewed up and shredded by a spiky structure called a radula inside the squid's mouth. The squid's visceral mass (containing the stomach and digestive tract, as well as other organs) is long, thin, and streamlined, in keeping with the squid's general form and function. We removed our squids' beaks (made of two interlocking pieces of chitin, a nitrogen-containing polysaccharide that is found in combination with calcium carbonate in the exoskeletons of arthropods), and we cut open our squids' mantles to take a look at the stomach.
At the end of the workshop, we looked at some videos of cephalopods releasing ink clouds and changing their color and shape to counter threats. Some of the groups also presented their findings to the class. One of the tables came around and showed everyone how to remove the lenses of our squid's eyes (squids' retina-equipped camera-type eyes are closely analogous to vertebrate eyes an example of convergent evolution). Another table came around and helped us locate and remove our squids' feathery gills.