Comparative aspects of the control of posture and locomotion in the spider crab Libinia emarginata

The study of pedestrian locomotion in crustaceans has largely focused on forward walking macrurans, or sideway walking brachyurans. The spider crab, Libinia emarginata is a brachyuran that, unlike its close relatives, preferentially walks forward. The phylogenetic position, behavioral preference, and amenability to experimental techniques make spider crabs an attractive model for comparative studies of crustacean locomotion. This dissertation looks at the neuroethology of forward walking in L. emarginata. I described the skeletal, muscular, and neural anatomy of the walking machinery of L. emarginata and found adaptations at each level that reflect its walking preference. The ranges of motion of leg joints aiding in forward locomotion were larger for spider crabs than for sideway walking crabs. The leg segments housing the musculature moving these joints were also larger. The proximal leg musculature consists of multiple muscle heads that can be activated independently during locomotion. The motor neurons innervating this musculature exhibited features of distantly related species that walk forward. Unlike many brachyurans, spider crabs use all ten legs during walking. Kinematic characterization of forward walking in L. emarginata showed that anterior and posterior limbs perform different functions during walking. Cross-correlation analysis among the leg joints of spider crabs revealed that distant joints have stronger coupling than adjacent ones. Neuroethology studies of pedestrian locomotion use multiple approaches. In order to understand how adaptive behavior is produced, it is necessary to study how the neural, muscular, and skeletal systems of an organism interact during its performance

Thermal acclimation and habitat-dependent differences in temperature robustness of a crustacean motor circuit

Introduction: At the cellular level, acute temperature changes alter ionic conductances, ion channel kinetics, and the activity of entire neuronal circuits. This can result in severe consequences for neural function, animal behavior and survival. In poikilothermic animals, and particularly in aquatic species whose core temperature equals the surrounding water temperature, neurons experience rather rapid and wide-ranging temperature fluctuations. Recent work on pattern generating neural circuits in the crustacean stomatogastric nervous system have demonstrated that neuronal circuits can exhibit an intrinsic robustness to temperature fluctuations. However, considering the increased warming of the oceans and recurring heatwaves due to climate change, the question arises whether this intrinsic robustness can acclimate to changing environmental conditions, and whether it differs between species and ocean habitats. Methods: We address these questions using the pyloric pattern generating circuits in the stomatogastric nervous system of two crab species, Hemigrapsus sanguineus and Carcinus maenas that have seen a worldwide expansion in recent decades. Results and discussion: Consistent with their history as invasive species, we find that pyloric activity showed a broad temperature robustness (>30°C). Moreover, the temperature-robust range was dependent on habitat temperature in both species. Warm-acclimating animals shifted the critical temperature at which circuit activity breaks down to higher temperatures. This came at the cost of robustness against cold stimuli in H. sanguineus, but not in C. maenas. Comparing the temperature responses of C. maenas from a cold latitude (the North Sea) to those from a warm latitude (Spain) demonstrated that similar shifts in robustness occurred in natural environments. Our results thus demonstrate that neuronal temperature robustness correlates with, and responds to, environmental temperature conditions, potentially preparing animals for changing ecological conditions and shifting habitats

Video dataset of C. elegans nematodes orienting to chemical, thermal, magnetic, and control stimuli

This dataset includes all videos used in our behavioral manuscript comparing the behavioral strategies of worms migrating in either a chemical, thermal, magnetic, or control gradient. Original videos are provided as well as duplicates showing the result of the machine vision acquisition of animal centroids which was used to obtain xy centroid coordinates for all animals used in the study

Factors that influence magnetic orientation in Caenorhabditis elegans

Magnetoreceptive animals orient to the earth’s magnetic field at angles that change depending on temporal, spatial, and environmental factors such as season, climate, and position within the geomagnetic field. How magnetic migratory preference changes in response to internal or external stimuli is not understood. We previously found that Caenorhabditis elegans orients to magnetic fields favoring migrations in one of two opposite directions. Here we present new data from our labs together with replication by an independent lab to test how temporal, spatial, and environmental factors influence the unique spatiotemporal trajectory that worms make during magnetotaxis. We found that worms gradually change their average preferred angle of orientation by ~ 180° to the magnetic field during the course of a 90-min assay. Moreover, we found that the wild-type N2 strain prefers to orient towards the left side of a north-facing up, disc-shaped magnet. Lastly, similar to some other behaviors in C. elegans, we found that magnetic orientation may be more robust in dry conditions (< 50% RH). Our findings help explain why C. elegans accumulates with distinct patterns during different periods and in differently shaped magnetic fields. These results provide a tractable system to investigate the behavioral genetic basis of state-dependent magnetic orientation.Fil: Bainbridge, Constance. Illinois State University; Estados UnidosFil: Clites, Benjamin L. University of Texas at Austin; Estados UnidosFil: Caldart Valle, Carlos Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; ArgentinaFil: Palacios, Beatriz. University of Texas at Austin; Estados UnidosFil: Rollins, K.. University of Texas at Austin; Estados UnidosFil: Golombek, Diego Andres. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; ArgentinaFil: Pierce, Jonathan Thomas. University of Texas at Austin; Estados UnidosFil: Vidal Gadea, Andrés. Illinois State University; Estados Unido

Development of a citrus genome-wide EST collection and cDNA microarray as resources for genomic studies

A functional genomics project has been initiated to approach the molecular characterization of the main biological and agronomical traits of citrus. As a key part of this project, a citrus EST collection has been generated from 25 cDNA libraries covering different tissues, developmental stages and stress conditions. The collection includes a total of 22,635 high-quality ESTs, grouped in 11,836 putative unigenes, which represent at least one third of the estimated number of genes in the citrus genome. Functional annotation of unigenes which have Arabidopsis orthologues (68% of all unigenes) revealed gene representation in every major functional category, suggesting that a genome-wide EST collection was obtained. A Citrus clementina Hort. ex Tan. cv. Clemenules genomic library, that will contribute to further characterization of relevant genes, has also been constructed. To initiate the analysis of citrus transcriptome, we have developed a cDNA microarray containing 12,672 probes corresponding to 6875 putative unigenes of the collection. Technical characterization of the microarray showed high intra- and inter-array reproducibility, as well as a good range of sensitivity. We have also validated gene expression data achieved with this microarray through an independent technique such as RNA gel blot analysis