OS54A-01
From Monotonous Hop-and-Sink Swimming to Constant Gliding via Chaotic Motions in 3D: Is There Adaptive Behavior in Planktonic Micro-Crustaceans?
Planktonic micro-crustaceans, such as Daphnia, Copepod, and Cyclops, swim in the 3D environment of water and feed on suspended material, mostly algae and bacteria. Their mechanisms for swimming differ; some use their swimming legs to produce one hop per second resulting in a speed of one body-length per second, while others scan water volumes with their mouthparts and glide through the water column at 1 to 10 body-lengths per second. However, our observations show that these speeds are modulated. The question to be discussed will be whether or not these modulations show adaptive behavior taking food quality and food abundance as criteria for the swimming performances. Additionally, we investigated the degree these temporal motion patterns are dependant on the sizes, and therefore, on the Reynolds number of the animals. http://pantherfile.uwm.edu/jrs/public
OS54A-02 INVITED
Planktotrophic versus lecithotrophic development in copepods
Copepods typically have planktotrophic larvae but some have adapted to the alternative lecithotrophic mode. This paper explores the differences between planktotrophic and lecithotrophic larvae in terms of their size, shape and appendage morphology - all factors affecting their motion through the medium. Such differences can be functionally correlated with the behavioral differences between the two larval types. Lecithotrophic nauplii are non- feeding, have simplified appendages and a shorter larval phase. Drivers of their behavior include dispersal and predator avoidance, in contrast to planktotrophic larvae which must, in addition, locate and capture food particles.
OS54A-03
Smelling in a small world: the interaction of ambient flow and behaviorally-created flow
The basis of many ecological interactions ultimately depends upon an organism's ability to extract relevant spatial and temporal information about its environment. Information about an environment is carried by sensory signals present within a habitat. Because sensory signals have varying physical properties, different physical phenomena in habitats will set constraints upon the transmitted signals. As a result of this physical constraint, organisms have evolved a variety of habitat-specific sensory systems and mechanisms to gather ecological information Among the many sensory systems that organisms have evolved, chemical senses are sources of ecological information for a variety of terrestrial and aquatic organisms. In particular, organisms in the marine environment have evolved elaborate mechanisms to extract information from chemical signals. To appreciate the difficulties associated with this behavioral task, it is imperative to understand the interaction between a sensory signal and the physical constraints of an environment. For odor signals, these physical processes are turbulent advection and dispersion. The purpose of this presentation is to review the set of physical parameters that constrain or govern the transmission and movement of chemical signals within different environments and review the various strategies that have evolved among organisms in order to effectively use chemical signals to solve important behavioral and ecological tasks.
OS54A-04
Fluid Dynamic Constraints on Morphology and Propulsion of Medusae at Low Reynolds Numbers
A recently developed mathematical model for physical constraints on the size and morphology of medusae was extended to include viscous effects that dominate at low Reynolds numbers. This fluid dynamic regime is experienced by all medusae during development and also by some adults. The lack of inertia in the flow field generated by medusae at low Reynolds numbers limits the vortex formation that is ubiquitous at higher Reynolds numbers. This consequently leads to the need for large oblate rowing medusae to use different propulsive solutions during their juvenile stages of development. Specifically, empirical observations of scyphomedusae (e.g., Aurelia sp.) and hydromedusae (e.g., Aequorea victoria and Obelia sp.) indicate distinct wake structures and swimming kinematics for each body type that exists during different stages of development. These differences can be explained by the extended mathematical model. In addition, ontogenetic changes can be visualized as trajectories within a plot of the new model.
OS54A-05 INVITED
Developmental changing in the form and function of rowing hydromedusae
Among medusan lineages bell morphology and propulsion appear to be interdependent traits. In general, taxa that possess large oblate bells swim via rowing propulsion and taxa with small prolate bells swim via jet propulsion. However, hydromedusae from the order, Leptomedusae, experience large changes in bell size and shape throughout their development, metamorphosing from small prolate juveniles into large oblate adults. To examine how propulsion changes throughout the development of leptomedusae, we investigated the fluid interactions and swimming characteristics of two leptomedusan species, Aequorea victorea and Eutonina indicans, throughout their development. As expected, these species start off as small prolate juveniles (< 2 mm diameter) and develop into large oblate adults (> 1.5 cm diameter). In addition to changes in morphology, we observed changes in Reynolds number, wake structure, propulsion and swimming kinematics. These changes were consistent with the previously described relationship between bell morphology and function.
OS54A-06
Functional morphology and fluid interactions during early development of scyphomedusae.
The physical dimensions of larval scyphomedusae, termed ephyrae, are typically small, often 2-3 mm in diameter, whereas adults of this group may be as large as 2 meters in diameter. Although ephyral morphologies are similar among scyphomedusae, adult morphologies vary widely. Kinematic studies of the species Aurelia aurita and Cyanea capillata demonstrate that viscous forces were important in flows around small ephyrae (maximum Re <10), whereas viscosity was less influential in the inertially dominated flows surround adult medusae (Re > 100). The timing of morphological alterations during development indicates that ontogenetic processes are closely synchronized with alterations in the hydrodynamic environment within which these medusae develop and that the interactions of morphology and fluid flows alter the feeding process during scyphozoan development.
OS54A-07
Energetics of jellyfish locomotion determined from field measurements using a Self- Contained Underwater Velocimetry Apparatus (SCUVA)
We conduct laboratory measurements of the flow fields induced by Aurelia labiata over a range of sizes using the method of digital particle image velocimetry (DPIV). The flow field measurements are used to directly quantify the kinetic energy induced by the swimming motions of individual medusae. This method provides details regarding the temporal evolution of the energetics during a swimming cycle and its scaling with bell diameter. These types of measurements also allow for the determination of propulsive efficiency, which can be used to compare various methods of propulsion, both biological and artificial. We then describe the development and application of a Self-Contained Underwater Velocimetry Apparatus (SCUVA), a device that enables a single SCUBA diver to make DPIV measurements of animal-fluid interactions in the field. Improvements and adjustments made to the original system will be presented, and a comparison between the animal-induced flow fields in the laboratory and in the field will be made.