Modelling quantitative structure-activity relationships between animal behaviour and environmental signal molecules.

Quantitative structure-activity relationships (QSARs) between the physicochemical properties of environmental signal molecules and animal behaviour have been determined. Past work has shown that oyster and barnacle larval settlement and mud crab abdominal pumping (for larval dispersal) are stimulated by small peptide cues. In all the peptides examined that were active at ecologically relevant concentrations, arginine or lysine was found at the carboxy terminus, but the amino acids found at preceding positions were highly variable.

The effects of walls, paternity and ageing on sperm motility.

The measurement of sperm motility is critical when studying fertilization kinetics and chemotaxis. Analysis of motility has traditionally been carried out on cells in small fluid volumes on microscope slides. Several theoretical treatments suggest that drag forces significantly affect flagellar motion within 10 sperm body lengths of the slide surface.

Chemical Induction of Larval Settlement Behavior in Flow.

The ability of dissolved chemical cues to induce larval settlement from the water column has long been debated. Through computer-assisted video motion analysis, we quantified the movements of individual oyster (Crassostrea virginica) larvae in a small racetrack flume at free-stream flow speeds of 2.8, 6.

The Relationship Between Predator Activity State and Sensitivity to Prey Odor.

Predators searching for prey commonly alternate periods of endogenous locomotory activity with rest. We examined the effects of activity state on behavioral responses to prey odor by predatory blue crabs (Callinectes sapidus) and spiny lobsters (Panulirus interruptus). All animals to be tested were placed individually in large seawater tanks (1.

Odor Plumes and Animal Navigation in Turbulent Water Flow: A Field Study.

Turbulence causes chemical stimuli to be highly variable in time and space; hence the study of animal orientation in odor plumes presents a formidable challenge. Through combined chemical and physical measurements, we characterized the transport of attractant released by clam prey in a turbulent aquatic environment. Concurrently, we quantified the locomotory responses of predatory crabs successfully searching for sources of clam attractant.

Evidence for hydrodynamic orientation by spiny lobsters in a patch reef environment.

Western Atlantic spiny lobsters (Panulirus argus) are superb underwater navigators. Spiny lobsters perform dramatic seasonal offshore migrations and have also been shown to locate and home to specific den sites within the elaborate coral reef environment in which they live. How these animals perform such complex orientation tasks is not known.

Magnetic orientation of spiny lobsters in the ocean: experiments with undersea coil systems.

The western Atlantic spiny lobster Panulirus argus undergoes an annual migration and is also capable of homing to specific dens in its coral reef environment. Relatively little is known, however, about the orientation cues that lobsters use to guide their movements. To determine whether lobsters can orient to the earth's magnetic field, divers monitored the orientation of lobsters tethered inside magnetic coil systems submerged offshore in the Florida Keys, USA.

Odor plumes and how blue crabs use them in finding prey.

Orientation of animals using chemical cues often takes place in flows, where the stimulus properties of odorants are affected by the characteristics of fluid motion. Kinematic analysis of movement patterns by animals responding to odor plumes has been used to provide insight into the behavioral and physiological aspects of olfactory-mediated orientation, particularly in terrestrial insects. We have used this approach in analyzing predatory searching by blue crabs in response to plumes of attractant metabolites released from the siphons of live clams in controlled hydrodynamic environments.

Spatial distribution of odors in simulated benthic boundary layer flows.

Many animals orient to odor sources in aquatic habitats where different flows and substrates affect the hydrodynamics of benthic boundary layers. Since the dispersal of chemicals is due to the fluid mechanics of a particular environment, we quantified the changes in the fine structure of an odor plume under different hydrodynamic conditions in the benthic boundary layer of a laboratory flume. We sampled turbulent odor plumes at 10 Hz using a microchemical sensor (150 µm diameter) under two flow speeds: 3.

Natural Sources and Properties of Chemical Inducers Mediating Settlement of Oyster Larvae: A Re-examination.

Live adult oysters and biofilms were separated experimentally as potential sources of waterborne chemical inducers of settlement in oyster larvae (Crassostrea virginica). Bacteria films growing on external shell surfaces were removed by mechanical agitation and chemical oxidation. This technique removed >99% of the viable bacteria without disrupting the normal production of metabolites by the oysters, measured as the weight-specific production of ammonium and dissolved organic carbon (DOC).

Measurement of Microscale Patchiness in a Turbulent Aquatic Odor Plume Using a Semiconductor-Based Microprobe.

The distribution of chemical signals within aquatic environments is highly patchy and heterogeneous due to dispersion by turbulent eddies. We aimed to quantify the smallest spatial scales associated with chemical patches, and therefore measured the structure of chemical signals under turbulent flow simultaneously at two chemical sensors spaced from 200 to 800 {mu}m apart. Measurements were done under controlled stimulus and flow conditions with a novel semiconductor-based, multisite, microelectrochemical electrode (5-2000 {mu}m2 surface area sensors) and a high-speed computer-based recording system.

Chemical Signal-to-Noise Detection by Spiny Lobsters.

The smallest difference in concentration detected between a chemical stimulus and background is called the threshold of "just noticeable difference" (jnd). Measurements of jnd thresholds have been made extensively in psychophysical research on olfactory and taste perception by terrestrial mammals, but not on chemoreception by marine organisms. Marine organisms live in a persistently noisy chemical environment, because stimulatory compounds are often components of the background in seawater.

Ontogeny Versus Phylogeny in Determining Patterns of Chemoreception: Initial Studies with Fiddler Crabs.

Fiddler crab (Uca longisignalis) first stage zoea and adults were assayed for behavioral responses to 16 amino acids and sugars. Larval chemosensitivity was examined using computer-video motion analysis of swimming behavior. Adult sensitivity was assayed by determining the substances that elicit feeding.

CHEMICAL MEDIATION OF APPETITIVE FEEDING IN A MARINE DECAPOD CRUSTACEAN: THE IMPORTANCE OF SUPPRESSION AND SYNERGISM.

The California spiny lobster, Panulirus interruptus, failed to exhibit appetitive feeding or locomotion in response to a low molecular weight fraction (< 1000 daltons) prepared from a sea water extract of muscle from abalone, a natural prey. This lack of response was caused by chemical suppressants, rather than by lack of stimulatory compounds. Excitatory responses were induced by single, low molecular weight compounds, but these responses were inhibited by suppressants which occur naturally in the muscle fraction.

Chemical induction of feeding in California spiny lobster,Panulirus interruptus (Randall): : Responses to molecular weight fractions of abalone.

Molecular weight fractions of abalone muscle were tested for the ability to induce appetitive feeding and locomotor behavior in the spiny lobster,Panulirus interruptus. Fractions of <1000, 1000-10,000 and >10,000 daltons were isolated by ultrafiltrations and gel chromatography from a seawater extract of abalone muscle. The two lower-molecular-weight fractions (<1000, 1000-10,000) were the least stimulatory of the three fractions tested, and both were ineffective as feeding stimulants.