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There is growing evidence that a natural repellent, injury-released alarm cues, can be used to guide the movements of invasive fishes to achieve management goals. However, because this process involves perception, downstream cognitive processing of sensory information affects decisions regarding expression of antipredator behavior. Response habituation, wherein repeated or continuous exposure to a cue reduces behavioral response rates, is an oft-cited challenge for use of predation cues as conservation tools. Habituation may be delayed or prevented by altering the concentration and/or the temporal pattern of odor release (pulses of odor vs continuous application). We examined the effects of varying odor concentration and exposure regime (continuous vs pulsed) on behavioral response of adult sea lamprey (Petromyzon marinus) to conspecific alarm cue in a two-choice maze. We found that exposure to alarm cue induced more frequent and rapid upstream movement, regardless of exposure regime. There was also clear evidence of a speed-accuracy tradeoff, wherein sea lamprey that took longer to arrive at the bifurcation in the maze were more likely to avoid the arm activated with alarm cue. We could not ascertain the value of increasing concentration or pulsing the alarm cue on preventing habituation, as habituation did not occur. We hypothesize dishabituation to the alarm cue occurred immediately prior to testing due to handling that may have inadvertently simulated an unsuccessful predator attack. If true, incorporating dishabituating stimuli may prove a useful means to maintain the efficacy of alarm cue when applied as a repellent to manipulate the movements of sea lamprey. [ABSTRACT FROM AUTHOR]

A study examines whether the physiological evolution of two Drosophila melanogaster populations on opposite slopes of Lower Nahal Oren, Mt. Carmel, Israel, despite a spatial separation of only 100-400 meters, was idiosyncratic and temporary, or persisted over multiple years. Results show that interpopulation differences in thermotolerance were stable despite year-to-year and seasonal variation in environmental conditions and potential inter-slope migration.

Natural heat exposure of larval Drosophila melanogaster results in high rates of larval mortality and severe developmental defects in eclosing adults. Transgenic increases in copy number of the gene encoding the major inducible heat-shock protein (Hsp) of D. melanogaster, Hsp70, mitigate these effects yet increase mortality during benign thermal conditions. In two wild D. melanogaster populations studied, approximately 10% of adult flies reared from field-collected fruit had severe developmental anomalies of wing and abdominal morphology. The frequency of developmental abnormalities varied along a natural thermal gradient, reaching 4% in adults eclosing from larvae developing in cool, shaded fruit and exceeding 12% for flies from warm, sunlit fruit. Heat-induced wing deformities dramatically reduced mating success in male flies. When exposed to strong natural heat stress, D. melanogaster with the wild-type number of Hsp70 genes (10) had higher rates of larval mortality and developmental disruption than a transgenic sister strain with additional (22) copies of the Hsp70 gene. However, under conditions of little or moderate natural thermal stress, larvae possessing 22 Hsp70copies had higher mortality rates than larvae possessing 10 Hsp70 copies. These results support the hypothesis of an evolutionary trade-off of the benefits and adverse consequences of Hsp70 expression.

We investigated whether polymorphisms at the 87A7 hsp70 cluster, which includes 2 of the 5 genes encoding the inducible molecular chaperone/heat-shock protein Hsp70, respond to natural and laboratory thermal selection in Drosophila populations. Our principal foci were morphs originally reported by Goldschmidt-Clermont (1980, Nucleic Acids Res. 8) as clones 122 and 56H8, and detectable by PCR and RFLP analysis. Allele frequencies covaried with evolution temperature in Drosophila melanogaster lines that have been cultured at different temperatures for more than 20 years and that differ in Hsp70 expression and inducible thermotolerance. Replicate lines evolving at 28fC fixed the 56H8-type morph, while those evolving at 18fC and 25fC fixed the alternative allele. Populations selected for low knockdown temperature (Gilchrist & Huey, 1999, Heredity 83) also differed in 56H8-type allele frequencies from the control and high selected populations. To test if hsp70 allele frequencies covaries with temperature in natural Drosophila populations, we screened flies from 'Evolution Canyon,' a small canyon in Israel (200 m wide at base) with north- and south-facing slopes (NFS and SFS, respectively). Allele frequencies in the NFS differed significantly from those in the SFS. Allele frequencies also covaried with collection latitude in Australian Drosophila populations from tropical to temperate (gift of Ary A. Hoffmann). These results suggest that alleles at the hsp7087A7 cluster respond to thermal selection in both natural and laboratory environments. The functional significance of the alleles themselves (or of sequences linked to these markers) remains to be determined. Supported by NSF97-23298, 99-86158, BSF98-00443, and HHMI.

Brief exposure to sublethal high temperature induces protection against a variety of stresses (e.g., high temperature, oxidation, hypoxia) in many organisms. The breadth of protection conferred in this way suggests potential importance in defending the mammalian central nervous system against the detrimental effects of ischemia and hypoxia. As part of our investigation into the effects of hyperthermia on neuronal function, we used standard whole-cell patch clamp techniques to determine whether thermal pretreatment alters the frequency of spontaneous glutamatergic and glycinergic synaptic transmission between neurons of the mouse pre-B-tzinger complex during subsequent hyperthermia. Without thermal pre-treatment, heating the tissue from 30 [degrees] to 40 [degrees] C increased the frequency of spontaneous miniature postsynaptic currents elicited by both glutamate and glycine by 1104.1 [+ or -] 86.3% and 3582.8 [+ or -] 142.6%, respectively. However, a 15 min thermal pretreatment at 39.5 [degrees] - 41 [degrees] C one hour prior to such hyperthermia significantly reduced the increase in frequency of spontaneous transmission via glutamate to 456.5 [+ or -] 43.4% above 30 [degrees] C baseline (p [is less than] 0.005) and via glycine to 1120.9 [+ or -] 94.8% above baseline (p [is less than] 0.0005). Two hours following thermal pretreatment, hyperthermia-induced increases in spontaneous transmission frequency remained significantly lower than those in tissues undergoing hyperthermia for the first time (p [is less than] 0.005 for both neurotransmitters). These data indicate that exposure of nervous tissue to temperatures experienced during high fever or heat stroke induces an acclimatory response opposing extreme deviation from normal frequencies of spontaneous synaptic transmission.

Both the communities of plant biology researchers and animal biology researchers include multidisciplinary groups that combine physiology, ecology, biochemistry, biomechanics, and evolution, but historically these groups have often been as distinct as the organisms they study. This symposium will challenge this historic distinction by asking in what ways the study of plant and animal function in environmental/evolutionary context need be separate disciplines, what biological issues transcend the two communities, and how best can plant and animal biologists realize the synergies afforded by their complementary viewpoints and study organisms? To do this, the symposium will partner distinguished plant and animal biologists to discuss topics of mutual interest: global climate change; sensing, signalling, and responding to the environment; mechanisms and implications of dormancy; and behavior versus tolerance as alternative responses to environmental stress.

To determine how the hsp70 genes (4-5 copies total, at two chromosomal loci) coevolved with the diversification of the D. melanogaster species subgroup, we sequenced multiple alleles of each gene in representative species. The hsp70 genes display strikingly different patterns of molecular evolution among the eight species of the subgroup. In D. simulans and D. melanogaster, frequent gene conversion homogenizes all the hsp70 coding sequences, diversifies flanking sequences, and interacts with both purifying and balancing selection to drive rapid concerted evolution. By contrast, hsp70 pseudogenes are common in D. mauritiana: null alleles of three of the four hsp70 genes are at high frequency. These pseudogenes also participate in gene conversion; copies at different loci share the same degenerative mutations. The hsp70 genes of D. orena, basal member of the subgroup, evolve in a fashion similar to those of D. simulans. While hsp70 expression level, thermotolerance, and thermal niche breadth are strongly coupled to the hsp70 genes in D. melanogaster, the functional copy number and relative 'health' of the hsp70 genome is only a fair predictor of these traits in other species. If, when, and how natural selection acts on the hsp70 genes varies in a lineage- and locus-specific fashion.

How do two hsp70 genes become five? While a single two-copy gene cassette is primitive in the Diptera, Drosophila melanogaster has five copies, distributed among two loci (87A7 and 87C1). Using Southern blots, we localize an initial duplication (from two to four hsp70s) on a phylogeny of the melanogaster species group. In the melanogaster subgroup, only D. melanogaster has five hsp70s (Aa, Ab, Ba, Bb, Be). Sequence analysis identifies and orders specific evolutionary events: after the initial chromosomal duplication, a tandem duplication yielded hsp70Bc. Next, multiple conversion events transferred characteristic sequence motifs, stepwise from gene to gene. This concerted evolution via gene conversion maintains low intra- and interlocus nucleotide variability. However, a Zimbabwean hsp70Bb allele lacks the conversion signatures of other hsp70Bb alleles; the Zimbabwe population may have diverged before a conversion event shared by the remainder of the world's D. melanogaster. Supported by NSF97-23298 to MEF and a HHMI Predoctoral Fellowship to BRB.

When not folded in their native conformation, cellular proteins can aggregate, damaging the cell. Molecular chaperones are a class of proteins that deter unfolded proteins from aggregating and facilitate their folding and/or degradation. The best-known of these, the heat-shock proteins (Hsps), are highly conserved and occur in all living things. In the last decade, research has focused on functions of Hsps in vitro and in the cell, and the role of protein folding in disease. Recently, a complementary focus has arisen on physiological, ecological and evolutionary variation in Hsps. Although some species sometimes express Hsps in response to natural stress, the frequency of such expression is presently unclear. Scattered information suggests that the magnitude and threshold for Hsp expression varies along natural gradients of stress, but this suggestion presently awaits systematic confirmation. Work on hsp gene sequences is now elucidating both the ancient and recent molecular evolution of Hsps. Advances in genetic engineering are now facilitating physiological examinations of Hsps in entire multicellular eukaryotes. Supported by NSF97-23298.

In studies of thermotolerance, large differences among higher taxa and small differences within a species are normally separate realms of investigation, with genetic experimentation currently feasible for only the latter. In the virilis group of Drosophila, however, species can be interbred to yield viable and partially fertile hybrids. Our research groups together have examined several species which replace one another along a latitutidinal gradient of temperature. The high-latitude species have lower thermotolerance. Hybrids are intermediate in thermotolerance. Reciprocal matings yield similar outcomes, consistent with an autosomal basis. Two species chosen for detailed study, D. virilis [low latitude] and D. lummei [high latitude], differ correspondingly in levels of heat-shock proteins. In situ hybridization to and the cloning and sequencing of the hsp68 and hsp70 genes reveal both inter-and intra-specific variation in hsp70 gene copy number due to both tandem duplication and pseudogenization. Extension of this analysis to multiple species pairs should permit a well-replicated analysis of the molecular basis of variation in thermotolerance among and within species. Supported by Russian Grants for Basic Science 0304-48-918 and 0204-49121, NSF grants IBN99-86158 and IBN03-16627.

Naturally-occurring heat shock (HS) during pupation induces abnormal wing development in Drosophila; we examined factors affecting the severity of this induction. The proportion of HS-surviving adults with abnormal wings varied with HS duration and intensity, and with the pupal age or stage at HS administration. Pretreatment (PT), mild hyperthermia delivered before HS, usually protected development against HS. Gradual heating resembling natural thermal regimes also protected wing development against thermal disruption. Because of the roles of the wings in flight and courtship and in view of natural thermal regimes that Drosophila undergo, both HS-induction of wing abnormalities and its abatement by PT may have marked effects on Drosophila in nature. Because PT is associated with expression of heat-inducible molecular chaperones such as Hsp70 in Drosophila, we compared thermal disruption of wing development among hsp70 mutants as well as among strains naturally varying in Hsp70 levels. Contrary to expectations, lines or strains with increased Hsp70 levels were no more resistant to HS-disruption of wing development than counterparts with lower Hsp70 levels. In fact, wing development was more resistant to HS in hsp70 deletion strains than control strains. We suggest that, while high Hsp70 levels may aid cells in surviving hyperthermia, high levels may also overly stimulate or inhibit numerous signaling pathways involved in cell proliferation, maturation, and programmed death, resulting in developmental failure.