9415791 Paffenhofer The long term goal of this project is to identify, describe and quantify key processes which govern the abundance, composition and distribution of zooplankton in the ocean. The general hypothesis, is that both, signal perception and the ability to respond to signals determine if a feeder/predator captures food/prey, or if the prey avoids or escapes from the predator. The ideas for this project were triggered by (a) articles on sensory performance of copepods, and (b) results from ongoing studies of behavior of prey and predators. In addition to major differences between species, prior work has indicated a range of small to major differences among developmental stages within species. Observation of behavior alone are insufficient to describe a stage's or species' range of capabilities to perceive and capture food, and to perceive and avoid predators. These observations must be coupled with information regarding the organisms' sensory physiology. Therefore, this project will examine: (a) the abundance and distribution of chemo-and mechanosensors on the cephalic appendages of nauplii, early copepodid stages, and adult females of five abundant species of marine planktonic copepods; and (b) ontogenetic changes in abundance and distribution of both sensor types using data obtained through (a). The project will utilize Laser Scanning Confocal Microscopy (LSCM) to describe the sensor distribution and orientation in 3-D (larger scale) and sensor type (smaller scale) and Transmission Electron Microscopy (TEM) to obtain ultrastructural information on the major sensor types as confirmation of the LSCM observations. The significance of the proposed studies lies in improving our understanding of what developmental stages and adult females of abundant copepod species can perceive and what they can not. Perception of food and predators is crucial for the existence of all species of planktonic copepods. Combining data from static (structure) an d dynamic (behavior) observation should result in more than the sum of both: relating information on coarse copepod morphology (e.g. appendage size) to information on feeding behavior, motion behavior sensor abundance and distribution, and sensor ontogenetic changes should improve our understanding (a) about how and why certain copepod species and stages can exist in their respective environments, and (b) how they may be phylogenetically related. ***
