Freeze avoidance: a dehydrating moss gathers no ice

Using cryo‐SEM with EDX fundamental structural and mechanical properties of the moss Ceratodon purpureus (Hedw.) Brid. were studied in relation to tolerance of freezing temperatures. In contrast to more complex plants, no ice accumulated within the moss during the freezing event. External ice induced desiccation with the response being a function of cell type; water‐filled hydroid cells cavitated and were embolized at ?4 °C while parenchyma cells of the inner cortex exhibited cytorrhysis, decreasing to ～20% of their original volume at a nadir temperature of ?20 °C. Chlorophyll fluorescence showed that these winter acclimated mosses displayed no evidence of damage after thawing from ?20 °C while GCMS showed that sugar concentrations were not sufficient to confer this level of freezing tolerance. In addition, differential scanning calorimetry showed internal ice nucleation occurred in hydrated moss at ～?12 °C while desiccated moss showed no evidence of freezing with lowering of nadir temperature to ?20 °C. Therefore the rapid dehydration of the moss provides an elegantly simple solution to the problem of freezing; remove that which freezes.     

How Much Water is in the Tank? Model Calculations for Two Epiphytic Bromeliads

Water-impounding foliage (=tank) characterizes many bromeliadspecies but, to date, a quantitative evaluation of the effectivenessof these structures to bridge rainless periods is not available.We present a model that analyses the capacity of these phytotelmatato supply moisture to the bromeliad as a function of plant size,and parameterize it for two epiphyte species,Tillandsia fasciculataandGuzmaniamonostachya. All parameters related to the recharging of a tank(e.g. catchment area, or tank capacity) and those related towater loss from the tank (e.g. tank water surface, or waterabsorption from the tank by the plant) changed with plant size.For both species a similar qualitative size-related patternemerged: smaller individuals dried out much faster than largerconspecifics. Modelling the changes in tank water content foran entire year revealed that in the seasonal climate of BarroColorado Island, Panama, tanks of smaller plants (1 g d. wt)are expected to lack water for up to 110 d (inT. fasciculata).Regardless of plant size, individuals ofG. monostachyawere consistentlymore efficient thanT. fasciculatain maintaining moisture intheir tanks. Our results provide insight into the limitationsof water-impounding tanks as an adaptation to cope with an intermittentwater supply typical for epiphytic habitats. These limitationsare particularly pronounced for smaller individuals.Copyright1999 Annals of Botany Company. Epiphytes, water relations, Barro Colorado Island, bromeliads, water tanks, phytotelmata.     

Action Mechanisms of the Secondary Metabolite Euplotin C: Signaling and Functional Role in Euplotes

ABSTRACT. Among secondary metabolites, the acetylated hemiacetal sesquiterpene euplotin C has been isolated from the marine, ciliated protist Euplotes crassus, and provides an effective mechanism for reducing populations of potential competitors through its cytotoxic properties. However, intracellular signaling mechanisms and their functional correlates mediating the ecological role of euplotin C are largely unknown. We report here that, in E. vannus (an Euplotes morphospecies that does not produce euplotin C and shares with E. crasssus the same interstitial habitat), euplotin C rapidly increases the intracellular concentration of both Ca²⁺ and Na⁺, suggesting a generalized effect of this metabolite on cation transport systems. In addition, euplotin C does not induce oxidative stress, but modulates the electrical properties of E. vannus through an increase of the amplitude of graded action potentials. These events parallel the disassembling of the ciliary structures, the inhibition of cell motility, the occurrence of aberrant cytoplasmic vacuoles, and the rapid inhibition of phagocytic activity. Euplotin C also increases lysosomal pH and decreases lysosomal membrane stability of E. vannus. These results suggest that euplotin C exerts a marked disruption of those homeostatic mechanisms whose efficiency represents the essential prerequisite to face the challenges of the interstitial environment.     

Advances in introgression technologies for precision breeding within the Lolium - Festuca complex

The anticipated complexity of multifunctional grasslands with environment‐friendly and sustainable management practices demands better understanding of traits, their interactions, and their genetic control. Intergeneric hybrids between closely related Lolium and Festuca species are being used to broaden the gene pool and provide the plant breeder with options to combine complementary traits aimed at high quality but more robust grass varieties for the future. New techniques in introgression mapping provide opportunities for precision breeding whereby desirable gene combinations transferred from one species into another are selected preferentially, with the exclusion of deleterious alien genes. The close homology between genomes of Lolium and Festuca species allows high levels of chromosome pairing and recombination. Using genomic in situ hybridisation (GISH) on Lolium/Festuca hybrids and their derivatives, recombination between Lolium and Festuca chromosomes is observed at any point along the chromosome. The system provides unlimited access to any combination of Lolium and Festuca DNA sequence. Moreover, genes transferred between homoeologous chromosome sites are expected to function normally at their new locations. Alien chromosome segments may be reduced in size by further recombination events thereby reducing linkage drag. Molecular markers such as AFLPs, SSRs, SNPs, or RFLPs are being targeted to genes of interest to allow their selection through different generations in plant breeding programmes. Relatively simple PCR‐based marker systems are used for specific traits as breeders' toolkits in plant breeding programmes.     

The effect of ploidy level on fitness in parthenogenetic flatworms

Although polyploidy plays an important role in speciation, its impact on fitness is still debated. One problem is that its adaptive significance can only be inferred by comparing forms with different ploidy that are identical in all other traits. This situation is uncommon, presumably because ploidy types often differ in reproduction mode, genetic background or habitat. Here we compare fitness in a system of triploid and tetraploid karyotypes of the planarian flatworm Schmidtea polychroa . Both types have the same type of sperm-dependent parthenogenesis and share the same genetic background and habitat. Hence, fitness differences, if any, can be attributed to different ploidy levels only. Contrary to the general assumption of a positive correlation between fitness and ploidy level, we showed that triploids produced 58% more offspring than tetraploids. Within each ploidy type, we identified groups of highly related clones using microsatellites. Significant variation among clonal groups in body size, offspring and cocoon number and hatching time indicated a genetic basis for variance in these traits. A small model shows that despite low fitness of tetraploids, stable coexistence of triploids and tetraploids can be explained by the recurrent origin of triploids from tetraploids and vice versa.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 191–198.     

Differential taphonomy of modern brachiopods (San Juan Islands, Washington State): effect of intrinsic factors on damage and community-level abundance

The differences in shell structure and population turnover between organic-poor, impunctate (Hemithiris) and organic-rich, punctate brachiopod (Terebratalia) in a mixed-bottom, siliciclastic setting (San Juan Islands, WA) lead to different taphonomic damage and fidelity with respect to community-level abundance in death assemblages. In comparing shell interiors of similar-sized specimens, Terebratalia is predominantly affected by fibre detachment and shows almost no microbioerosion at the SEM scale; whereas, Hemithiris shows less marked fibre detachment at the SEM scale and is more intensely affected by microbioerosion both at SEM and light microscope (LM) scales. Fibre detachment related to rapid, microbially-induced organic matter decay appears to be the main destructive process acting on Terebratalia. Higher bioerosion levels in Hemithiris at SEM and LM scales are probably related to a combination of a low maceration rate and a preferential settlement by borers. From their vastly different abundances in life assemblages it can be deduced that Terebratalia produces dead shells at a much higher rate than Hemithiris. Therefore, the proportion of altered Terebratalia, relative to Hemithiris, is expected to be decreased due to its higher production of recently dead cohorts. That Terebratalia is also characterized by high damage levels shows that differential population turnover alone is not responsible for the differences in taphonomic damage. This shows that organic-rich and organic-poor shells are characterized by differential post-mortem durability. Although very few Hemithiris are present in the life assemblages, high durability ensures its relative over-representation in death assemblages. Terebratalia is not strongly under-represented in death assemblages, despite its high destruction rate, because of large production of recently dead shells. Even with the biasing effect of differential durability, the good fidelity reported in previous live-dead studies can be enhanced by higher population turnover of numerically dominant taxa, leading to constant input of recently dead shells into death assemblages.     

Phylogenetic relationships of the north-eastern Atlantic and Mediterranean blenniids

The phylogenetic relationships of 27 north-eastern Atlantic and Mediterranean blennioids are analysed based on a total of 1001 bp from a combined fragment of the 12S and 16S mitochondrial rDNA. The most relevant results with implications in current blenniid taxonomy are: (1) Lipophrys pholis and Lipophrys (=  Paralipophrys ) trigloides are included in a well-supported clade that by the rule of precedence must be named Lipophrys ; (2) the sister species of this clade are not the remaining species of the genus Lipophrys but instead a monotypic genus comprising Coryphoblennius galerita ; (3) the smaller species of Lipophrys were recovered in another well-supported and independent clade, which we propose to be recognized as Microlipophrys ; (4) although some authors included the genera Salaria and Lipophrys in a single group we have never recovered such a relationship. Instead, Salaria is more closely related to the genera Scartella and Parablennius ; (5) the genus Parablennius , which was never recovered as a monophyletic clade, is very diverse and may include several distinct lineages; (6) the relative position of Aidablennius sphynx casts some doubts on the currently recognized relationships between the different blenniid tribes. Meristic, morphological, behavioural and ecological characters support our results and are also discussed. The possible roles of the tropical West African coast and the Mediterranean in the diversification of blenniids are discussed.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 86 , 283–295.     

Genome redundancy and plasticity within ancient and recent Brassica crop species

The crop species within the genus Brassica have highly replicated genomes. Three base 'diploid' species, Brassica oleracea , B. nigra and B. rapa , are likely ancient polyploids, and three derived allopolyploid species, B. carinata , B. juncea and B. napus , are created from the interspecific hybridization of these base genomes. The base Brassica genome is thought to have hexaploid ancestry, and both recent and ancient polyploidization events have been proposed to generate a large number of genome rearrangements and novel genetic variation for important traits. Here, we revisit and refine these hypotheses. We have examined the B. oleracea linkage map using the Arabidopsis thaliana genome sequence as a template and suggest that there is strong evidence for genome replication and rearrangement within the base Brassicas, but less evidence for genome triplication. We show that novel phenotypic variation within the base Brassicas can be achieved by replication of a single gene, BrFLC , that acts additively to influence flowering time. Within the derived allopolyploids, intergenomic heterozygosity is associated with higher seed yields. Some studies have reported that de novo genomic variation occurs within derived polyploid genomes, whereas other studies have not detected these changes. We discuss reasons for these different findings. Large translocations and tetrasomic inheritance can explain some but not all genomic changes within the polyploids. Transpositions and other small-scale sequence changes probably also have contributed to genomic novelty. Our results have shown that the Brassica genomes are remarkably plastic, and that polyploidy generates novel genetic variation through gene duplication, intergenomic heterozygosity and perhaps epigenetic change.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 665–674.     

ODOR IDENTIFICATION ABILITY PREDICTS CHANGES IN SYMPTOMS OF PSYCHOPATHOLOGY FOLLOWING 56 H OF SLEEP DEPRIVATION

ABSTRACTS

A person's ability to identify odors provides an index of the functional integrity of the brain's prefrontal cortex. Some evidence suggests that the functional activity of the prefrontal cortex, when well rested, may predict individual differences in the ability to sustain performance when subsequently sleep deprived. It was hypothesized that odor identification accuracy, when rested would predict the vulnerability to sleep deprivation‐mediated elevations of affective symptoms of psychopathology, as measured on the Personality Assessment Inventory (PAI). Twenty‐two healthy volunteers completed the University of Pennsylvania Smell Identification Test (SIT) and the PAI when rested. After 56 h of continuous wakefulness, participants were re‐administered the PAI. Poorer odor identification at baseline correlated with increased symptoms of depression and borderline negative relationships. In contrast, higher SIT scores correlated with increased manic irritability. Results suggest that better olfactory identification in the well‐rested state (a putative index of orbitofrontal cortex integrity) predicts affective stability during subsequent sleep deprivation.

PRACTICAL APPLICATIONS

The findings of the study showed that a brief, portable and easily administered test of olfactory perception was effective at identifying individuals that were likely to show degradation of emotional and cognitive performance when sleep deprived. With further validation, odor identification tasks, such as the Smell Identification Test, may provide quick screening tools to aid in identifying and selecting personnel that may operate most effectively under adverse conditions of prolonged wakefulness.