Hopkins Marine Station Student Paper

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(full paper is archived in the Miller Library)

Title: Life at drastically different Reynold's numbers: the effects of fluid dynamics on medusan locomotion and strategies young medusae employ to try to overcome the overwhelming viscous forces of their environment
Student Author(s): Griffiths, Richard C.
Faculty Advisor(s): Denny, Mark
Pages: 34
Location: Final Papers Biology 175H
Date: June 1990
Abstract: The properties of fluid dynamics present interesting problems for marine life, dictating that the locomotion of slow moving animals are controlled by the viscous forces in their environment. This study looked at medusan locomotion in adult and young Eutonina indicans. Medusae, unlike many other small marine organisms, maintain the same relative shape and method of locomotion as their size spans 4+ orders of magnitude during their growth phase. It was found that the locomotion of the young medusae was dominated by drag. These juveniles accelerate rapidly to overcome the viscous forces inhibiting their motion, but decelerate just as rapidly as thrust tapers off. Medusae swim by a jet propulsion mechanism, in which they produce thrust by ejecting fluid backwards. The adults contract and accelerate slower, but move more efficiently and further than the young due to their larger size. Over a similar time span and number of swimming cycles the young only managed to move 1/3 of the relative distance of the adults.