Swimming, Jumping, Adhering, and “Catching:” Comparing Mollusk Muscle Tissue Profiles through Gel Electrophoresis
By Tara Pegasus
Our research project compares the muscle profiles of four bivalve mollusks (clam, mussel, oyster, and scallop), one cephalopod mollusk (squid), as well as an arthropod outlier (shrimp).
To formulate our phylogenetic hypothesis, I conducted background research on the habitat and behavior of the mollusks. I discovered that even the sessile species (oysters and mussels) have very powerful muscles, since they need to be firmly attached to a variety of surfaces such as rocks, fish, and shells. One group from Hanyang University was inspired by the adhesive proteins (called MAPs) that marine mussels produce to help them attach to different surfaces in their alkaline environment, and explored surface modification techniques to be used in tissue engineering (Kumar et al. 2015). Bivalves also have special adductor muscles that can retain tension for long periods with minimal energy, a phenomenon known as “catch.” It’s regulated by a protein in the titin group, called twitchin, that is about 500 kDa in size (Funabara et al. 2015). I will be looking for this band, which I predict shrimp and squid will not share.
Squid, the lone cephalopod mollusk in the group, is known for how quickly it can contract its lethal tentacles, doubling their length in only 15 ms (Knight 2012). Research done by Justin Shaffer of the University of North Carolina aimed to investigate if squid regulated their quickly deployable tentacles by modifying myosin molecules, an evolutionary technique other animals have developed. Scallops, for example, use a “fast” myosin isomer and short sarcomeres to quicken their muscle contraction rates. Shaffer concluded, however, that squid don’t use a specialized myosin isomer for their lethal tentacles; that tissue shared the same three myosin isomers with other muscular tissue from the squid’s mantle, arm, fin, and funnel retractor. The differing contraction rate for their muscles are due to ultrastructure modifications, not a specialized myosin isomer (Shaffer and Kier 2012). Because of this research, I would expect to find a heavy band of protein around the myosin standard, reflecting the different isomers in squid muscle tissue.
References:
Funabara, Daisuke, Shugo Watabe, and Satoshi Kanoh. 2015. Phosphorylation properties of twitchin from Yesso scallop catch and striated muscles. Fisheries Science 81, no. 3: 541-550; [cited 8 Feb 8, 2017]. Academic Search Premier, EBSCOhost.
Knight, Kathryn. 2012. Journal of Experimental Biology. 215: i-ii; doi: 10.1242/jeb.069161; [cited 9 Feb, 2017]. Available from http://jeb.biologists.org/content/215/2/i.2
Kumar, Sajeesh, Perikamana, Madhurakkat, Lee, Jinkyu, Lee, Yu Bin, Shin, Young Min, Lee, Esther J., Mikos, Anotnios G., Shin, Heungsoo. 2015. Materials from mussel-inspired chemistry for cell and tissue engineering applications. Biomacromolecules, 16 (9) 2541-2555, doi: 10.1021/acs.biomac.5b00852; [cited 8 February 2017]. Available from http://pubs.acs.org/doi/10.1021/acs.biomac.5b00852
Shaffer, J. F. and Kier, W. M. 2012. Muscular tissues of the squid Doryteuthis pealeii express identical myosin heavy chain isoforms: an alternative mechanism for tuning contractile speed. J of Exp Biol. 215, 239-246; [cited 9 Feb, 2017]. Available from http://jeb.biologists.org/content/215/2/239?ijkey=86f546d57dca41219966c08588bfd5510bc83454&keytype2=tf_ipsecsha.
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