Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 561805
Title Functional design of tentacles in squid : Linking sarcomere ultrastructure to gross morphological dynamics
Author(s) Leeuwen, J.L. Van; Kier, W.M.
Source Philosophical Transactions of the Royal Society B. Biological sciences 352 (1997)1353. - ISSN 0962-8436 - p. 551 - 571.
Publication type Refereed Article in a scientific journal
Publication year 1997

This paper offers a quantitative analysis of tentacle extension in squid that integrates several levels of structural organization. The muscular stalks of the two tentacles of squid are rapidly elongated by 70% of resting length during prey capture. A typical duration of the extension is 30 ms in Loligo pealei (with a contracted tentacle length of 93 mm and a strike distance of about 37 mm). In a successful strike, the terminal clubs hit the prey and attach to it via arrays of suckers. A forward dynamics model is proposed for the extension of the tentacular stalk and the forward motion of the terminal club. The stalk is modelled as a longitudinal array of thin muscular discs with extensor muscle fibres oriented parallel to the disc planes. As a disc contracts radially, it lengthens because its volume is constant. The equations of motion for the linked system of discs were formulated and solved numerically. The inputs of the model are the dimensions of the tentacle, passive and active muscle properties such as Hill's force-velocity relationship, myofilament lengths and activation of the muscle fibres. The model predicts the changing geometry of the tentacle, the pressure and stress distribution inside the tentacle and the velocity and kinetic energy distribution of the stalk and club. These predictions are in agreement with kinematic observations from high-speed films of prey capture. The model demonstrates also that the unusually short myosin filaments (reported range 0.5-0.9 μm) that characterize the extensor muscles are necessary for the observed extension performance. Myosin filament lengths typical for vertebrate sarcomeres (1.58 μm) would lead to a significant reduction in performance. In addition, the model predicts that, to maximize peak velocity of the terminal club, the myosin filaments should be longer at the base and shorter at the tip of the stalk (0.97 μm at the base and 0.50 μm at the tip for the tentacle size above). This results from differences in dynamic loading along the stalk. Finally, the model allows exploration of the effects of changes in the dimensions and mass of the tentacle and intrinsic speed of the myofilaments on the optimum myosin filament lengths.

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