Biomechanics Analyses and Application of Freshwater Snails Sinotaia quadrata, Semisulcospira libertina, and Thiara granifera for Channel Ecological Engineering Design
Date Issued
2006
Date
2006
Author(s)
Yang, Song-Yue
DOI
en-US
Abstract
Freshwater snails are important biological indicators of water quality and the primary source of sustenance for firefly larvae in Taiwan. Currents may promote the transport of nutrients and the metabolism of aquatic organisms. However, they may simultaneously exert stresses on organisms. Biomechanics helps us to understand and quantify the interaction between an organism and its physical environments. In this study, the morphology, drag, lifts, adhesive forces and dislodgment velocities of Sinotaia quadrata, Semisulcospira libertina, and Thiara granifera were measured. The relationships among hydrodynamics, morphology and mechanical characteristics were derived from the results of the measurements. An analysis using the dislodgment model was conducted.
The results indicated that the streamline shell could reduce drag and lift under high current velocity. The morphology of T. granifera was better than those of S. quadrata and S. libertina for resisting hydrodynamic stresses because it is streamlined. Theoretically, T. granifera should be better able to resist dislodgment than S. quadrata and S. libertina; however, the results of the dislodgment experiment did not confirm this expectation but showed that the experimental dislodgment velocity of T. granifera was the slowest (67cm/s); that of S. quadrata was middle (72cm/s); that of S. libertina was the fastest (107cm/s). The experimental dislodgment velocities of freshwater snails were tally with the calculated dislodgment velocities obtained by dislodgment model. The analysis of the dislodgement model showed that the mechanism of dislodgment of freshwater snails consists of two parts - the actual dislodgment mechanism, involving drag, lift, and buoyancy, and the dislodgment-resistance mechanism, involving adhesive force and weight. In conclusion, the hydrodynamic forces were determined primarily by the morphology of the shell, and the adhesive forces served as a buffer of the direct effects of hydrodynamic forces. The dislodgment velocity was determined by the interaction between hydrodynamic and biological mechanisms. The adhesive force of S. quadrata was the strongest but its morphology was the worst; the morphology of T. granifera was the best but its adhesive force was the weakest. S. libertina had balance performance on both of adhesive force and morphology. The drag load on S. libertina is reduced by: the slender, streamlined shape of shell, the change of orientation and attacking angle, and the flexibility of the muscle.
The analysis of biomechanics provides a valuable reference for ecological engineering design. The design velocities can be determined by the mean and standard deviation of the normal cumulative probability function obtained in the dislodgment experiment to conserve the ecology of native freshwater snails and control the harmful ones. The design current velocity could be determined by controlling the roughness of the substrate, the channel section and the slope of the riverbed. In addition, the substrate material influences the adhesive force simultaneously.
Subjects
淡水螺
生物力學
形態
石田螺
川蜷
瘤蜷
升力
阻力
吸附力
reshwater snail
biomechanics
morphology
Sinotaia quadrata
Semisulcospira libertina
Thiara granifera
lift
drag
adhesive force
Type
thesis
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