3,482 research outputs found
Behavioral thermoregulation in the American lobster Homarus americanus
It is generally accepted that water temperature has a strong influence on the behavior of the American lobster Homarus americanus. However, there is surprisingly little behavioral evidence to support this view. To haracterize the behavioral responses of lobsters to thermal gradients, three different experiments were conducted. In the first, 40 lobsters acclimated to summer water temperatures (summer-acclimated, 15.5±0.2 °C, mean ±S.E.M.) were placed individually in an experimental shelter, and the temperature in the shelter was gradually raised until the lobster moved out. Lobsters avoided water warmer than 23.5±0.4 °C, which was an increase of 8.0±0.4 °C from ambient summer temperatures. When this experiment was repeated with lobsters acclimated to winter temperatures (winter-acclimated, 4.3±0.1 °C), the lobsters (N=30) did not find temperature increases of the same magnitude (∆T=8.0±0.4 °C) aversive.
The second experiment was designed to allow individual summer-acclimated lobsters (N=22) to select one of five shelters, ranging in temperature from 8.5 to 25.5 °C. After 24 h, 68 % of the lobsters occupied the 12.5 °C shelter, which was slightly above the ambient temperature (approximately 11 °C). In a similar experiment, winter-acclimated lobsters (N=30) were given a choice between two shelters, one at ambient temperature (4.6±0.2 °C) and one at a higher temperature (9.7±0.3 °C). Winter-acclimated lobsters showed a strong preference (90 %) for the heated shelter.
In the final experiment, summer-acclimated lobsters (N=9) were allowed to move freely in a tank having a thermal gradient of approximately 10 °C from one end to the other. Lobsters preferred a thermal niche of 16.5±0.4 °C and avoided water that was warmer than 19 °C or colder than 13 °C. When standardized for acclimation temperature, lobsters preferred water 1.2±0.4 °C above their previous ambient temperature. Collectively, the results of these studies indicate that lobsters are capable of sensing water temperature and use this information to thermoregulate behaviorally. The implications of these findings for lobster behavior and distribution in their natural habitat are discussed
Auditory-motor adaptation is reduced in adults who stutter but not in children who stutter
Previous studies have shown that adults who stutter
produce smaller corrective motor responses
to compensate for unexpected auditory perturbations in comparison to adults who do not stutter, suggesting that stuttering may be associated with deficits in integration of auditory feedback for
online speech monitoring. In this study, we examined whether stuttering is also associated with
deficiencies in integrating and using discrepancies between expect
ed and received auditory
feedback to adaptively update motor programs for accurate speech production.
Using a sensorimotor adaptation paradigm, we measured adaptive speech responses to auditory formant frequency perturbations in adults and children who stutter and their matched nonstuttering
controls.
We found that the magnitude of the speech adaptive response for children who stutter
did not differ from that of fluent children. However, the adaptation magnitude of adults who
stutter in response to formant
perturbation was significantly smaller than the adaptation
magnitude of adults who do not stutter. Together these results indicate that stuttering is
associated with deficits in integrating discrepancies between predicted and received auditory feedback to calibrate the speech production system in adults but not children. This auditory-motor integration deficit thus appears to be a compensatory effect that develops over years of stuttering
Heritability estimates of hatching time in the fayoumi chickens
International audienc
Sex-linkage as a factor in the inheritance of sex differences for body weight in two strains of chickens
International audienc
Heritability of the differences in body weight between sexes at different ages in two strains of chickens
International audienc
A Ruthenium Olefin Metathesis Catalyst with a Four-Membered N-Heterocyclic Carbene Ligand
The first ruthenium olefin metathesis catalyst bearing a four-membered N-heterocyclic carbene (5) was synthesized and characterized by NMR spectroscopy and X-ray crystallography. The synthesis of a (carbene)carbonylrhodium complex (6) was also reported, allowing the study of the electronic properties of this new carbene ligand. The complex 5 was screened toward different olefin metathesis reactions, and it showed a slow reactivity
A Stable Four-Membered N-Heterocyclic Carbene
The synthesis of the first four-membered N-heterocyclic carbene is described. Depending on the substituents on the nitrogen atoms, it is possible to characterize at room temperature the carbene dimer or the free carbene. Crystallographic analyses are provided for these carbene species
Dramatic expansion of the black widow toxin arsenal uncovered by multi-tissue transcriptomics and venom proteomics.
BackgroundAnimal venoms attract enormous interest given their potential for pharmacological discovery and understanding the evolution of natural chemistries. Next-generation transcriptomics and proteomics provide unparalleled, but underexploited, capabilities for venom characterization. We combined multi-tissue RNA-Seq with mass spectrometry and bioinformatic analyses to determine venom gland specific transcripts and venom proteins from the Western black widow spider (Latrodectus hesperus) and investigated their evolution.ResultsWe estimated expression of 97,217 L. hesperus transcripts in venom glands relative to silk and cephalothorax tissues. We identified 695 venom gland specific transcripts (VSTs), many of which BLAST and GO term analyses indicate may function as toxins or their delivery agents. ~38% of VSTs had BLAST hits, including latrotoxins, inhibitor cystine knot toxins, CRISPs, hyaluronidases, chitinase, and proteases, and 59% of VSTs had predicted protein domains. Latrotoxins are venom toxins that cause massive neurotransmitter release from vertebrate or invertebrate neurons. We discovered ≥ 20 divergent latrotoxin paralogs expressed in L. hesperus venom glands, significantly increasing this biomedically important family. Mass spectrometry of L. hesperus venom identified 49 proteins from VSTs, 24 of which BLAST to toxins. Phylogenetic analyses showed venom gland specific gene family expansions and shifts in tissue expression.ConclusionsQuantitative expression analyses comparing multiple tissues are necessary to identify venom gland specific transcripts. We present a black widow venom specific exome that uncovers a trove of diverse toxins and associated proteins, suggesting a dynamic evolutionary history. This justifies a reevaluation of the functional activities of black widow venom in light of its emerging complexity
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