The Hearing Sensitivity of the Little Skate, Raja erinacea: A Comparison of Two Methods

We determined the hearing sensitivity of the little skate, Raja erinacea using two methods: Behavioral conditioning and the auditory brainstem response (ABR). This marks the first time that the hearing in any member of the Rajiformes has been examined and the first time that the ABR method has been used with an elasmobranch. We obtained audiograms of R. erinacea using each method and were found to be statistically similar. The best hearing sensitivity for R. erinacea was between 100 and 300Hz. We compared the audiograms to audiograms obtained from other species of elasmobranchs. This analysis showed that R. erinacea, a bottom-dwelling elasmobranch, has less sensitive hearing than the lemon shark, Negaprion brevirostris, and the bull shark, Carcharhinus leucas, a free-swimming, raptorial elasmobranch. However, R. erinacea showed sensitivity comparable to that of the horn shark, Heterodontus francisi, another bottom-dwelling elasmobranch; both species feed primarily on benthic prey. These findings are in agreement with Corwin's hypothesis (1978) that hearing sensitivity is correlated with feeding behavior. An examination of the macula neglecta of R. erinacea found a total count of 10000 hair cells, which is within the range of other bottom-dwelling elasmobranchs.     

The Streptomyces coelicolor ssgB gene is required for early stages of sporulation

ssgB was identified as a novel early sporulation gene in Streptomyces coelicolor. An ssgB deletion mutant failed to sporulate, over-produced actinorhodin, and its colonies were significantly larger than those of the parental strain, suggesting an important role for the ssgB gene product in the process of growth cessation prior to sporulation-specific cell division. This places ssgB temporally before the paralogous sporulation gene ssgA. Analysis of ssgB mutant hyphae by electron microscopy and by confocal fluorescence microscopy showed that it was defective in the initiation of sporulation, as no sporulation septa could be identified, and DNA segregation had not yet been initiated in the mutant.     

Knockout mice as model systems for studying nm23/NDP kinase gene functions. Application to the nm23-M1 gene

Mice carrying a homozygous germ-line mutation in the nm23-M1 gene that eliminates its protein expression and drives expression of -galactosidase by nm23-M1 promoter have been generated. nm23-M1 gene inactivation is not teratogenic and the pups can grow to adult age without apparent health problems. However, they undergo a growth retardation and knocked out females cannot feed their pups. Both effects are background dependent. -galactosidase mapping of nm23-M1 promoter activation during embryogenesis shows that the nm23-M1 gene is principally expressed in epithelial layer of tissues which require inductive epithelial–mesenchymal interactions for their formation. In conclusion, invalidated mice could be interesting models to analyze the role of nm23-M1 on signal transduction pathway regulation, or cancer induction and proliferation.     

Phenotypic plasticity of larval retreat design in a net-spinning caddisfly

Larval Macrostemum carolina caddisflies construct silken catchnetswithin protective retreats, often on submerged trees and branches(i.e., snags). In the Savannah River, M. carolina larvae constructthree distinct retreats that differ in the configuration ofthe water entrance hole: (1) at the end of a silken tube, (2)flush with the top of the retreat, and (3) backed by a 180-degreesilken backstop. To identify the proximate mechanism mediatingthis retreat polymorphism, we removed larvae of known phenotypefrom their original retreats and brought them into the laboratory,allowing them to construct new retreats. We found that (1) larvaecan construct more than one type of retreat, so variation inthis behavior is not under strict genetic control; (2) larvaedo not preferentially reconstruct their original retreat design,so these alternative behaviors apparently exhibit little heritability;and (3) larvae primarily construct each phenotype in a particularmicrohabitat (i.e., "tube" and "backstop" retreats are principallyconstructed on the downstream half of the snag, and "flush"retreats on the upstream–bottom quadrant). Therefore,the retreat polymorphism in M. carolina is phenotypically plasticand is controlled by microhabitat location or a correlated environmentalvariable. Most net-spinning caddisflies construct their netsin fairly specific microhabitats. However, behavioral plasticityallows M. carolina larvae to construct retreats all around asnag, thereby reducing potentially intense competition for spacewith other net-spinning caddisflies. Consequently, this maybe the ultimate reason this polymorphism evolved.     

Enhancement of antidepressant potency by a potentiator of AMPA receptors

1. AMPA receptor potentiators (ARPs) exhibit antidepressant-like activity in preclinical tests (for example, the forced swim test) that are highly predictive of efficacy in humans. Unlike most currently used antidepressants, ARPs do not elevate extracellular levels of biogenic amines (e.g., 5HT, NE) in prefrontal cortex at doses that are active in the forced swim test.2. The present series of experiments examined the effects of combining the ARP, LY 392098, with biogenic amine-based antidepressants in the forced swim test. Male, NIH Swiss mice were placed in a cylinder of water and observed for attempted escape behaviors and immobility.3. LY 392098 dose-dependently decreased immobility as did a range of classical antidepressants. At doses of LY 392098 below those that decreased immobility, this compound significantly increased the potency with which fluoxetine and citalopram (SSRI antidepressants), imipramine (tricyclic antidepressant), duoxetine (norepinephrine/serotonin uptake blocker), nisoxetine (norepinephrine uptake inhibitor), and rolipram (PDE4 inhibitor) decreased immobility in the forced swim test with potency shifts upward of 5-fold (fluoxetine, imipramine, and rolipram). Likewise, ineffective doses of the traditional antidepressants potentiated the effects LY 392098 with shifts in the dose-effect functions that were 10-fold or more for citalopram, fluoxetine, imipramine, and duloxetine.4. Combined with other evidence for a role of AMPA receptors in the efficacy of antidepressants, the current data suggest that the addition of an ARP may augment the activity and perhaps the onset of the therapeutic effects of biogenic amine and second messenger-based antidepressants.     

Development of pheromone-based mating disruption for control of the eye-spotted bud moth, Spilonota ocellana

The potential for pheromone-based mating disruption of eye-spotted bud moth (ESBM), Spilonota ocellana (Denis & Schiffermüller) (Lepidoptera: Tortricidae), in apple orchards in the Okanagan Valley of British Columbia was examined in small-plot trials. In a preliminary experiment, treatment of the orchard atmosphere with a 99:1 blend of Z8-tetradecenyl acetate (Z8-14:OAc) and Z8-tetradecenyl alcohol (Z8-14:OH) completely inhibited captures of male ESBM in pheromone-baited traps, but treatment with Z8-14:OAc alone did not. Therefore, all subsequent trials used the two-component blend as a disruptant. Mean catches of male ESBM in traps baited with 0.1, 1, 10, or 20 mg of 99:1 Z8-14:OAc and Z8-14:OH were significantly reduced (81–97%) in pheromone-treated plots relative to similar traps placed in control plots. In both control and treated plots, there was a significant positive relationship between trap bait dose and trap catch. In pheromone-treated plots, this suggests that high doses of trap baits over-ride the camouflage effect of disruption or overcome the effect of sensory adaptation and habituation. The number of virgin-female baited traps capturing at least one male ESBM was reduced by 96%, and mating of virgin females on mating tables was reduced by 95% in plots treated with the two-component pheromone. The total amount of Z8-14:OAc released from pheromone disruption dispensers during the latter field trials was estimated to average 6.4 g ha^-1 over 11 days or 26.4 mg ha^-1 h^-1. The low levels of Z8-14:OH released from disruption dispensers could not be estimated by GC analysis. Dispensers loaded with a 99:1 blend of Z8-14:OAc and Z8-14:OH were highly attractive to males in baited traps, indicating that they have the potential to induce false trail following.     

Behavioral syndrome over the boundaries of life--carryovers from larvae to adult damselfly

Activity is an important behavioral trait that mediates a trade-offbetween obtaining food for growth and avoiding predation. Activeindividuals usually experience a higher encounter rate withfood items and suffer higher predation pressure than less activeindividuals. I investigated how activity of the damselfly Lestescongener is affected by larval state and predator presence andif larval behavioral type (BT) can be used to predict larvalboldness, foraging success, and adult BT. Activity level ofindividual larvae was studied without predator at 2 differentphysiological states (hungry and fed) and in 2 predator treatments:familiar predator cues and unfamiliar predator cues. Larvaedid not adjust their activity depending on state or when subjectedto unfamiliar predator cues, but a general reduction in activitywas seen in the familiar predator treatment. Hence, active individualsremained active compared with their conspecifics, independentof state or predator treatment. Active individuals were alsobolder and more efficient foragers than their less active conspecifics.Furthermore, both adult activity and boldness were correlatedwith larval BT. The results illustrate that BT of a larvae iscarried over many different situations keeping active larvaeactive even in maladaptive situations, demonstrating how a behavioralsyndrome may constrain behavioral plasticity. Furthermore, resultsshowed that behavioral syndromes can carry over from larvaethrough metamorphosis and dictate the BT of the adult.