Vertical migration for horizontal transport while avoiding predators: I. A tidal/diel model

Research into the vertical migration behavior of scallop (Placopectenmagellanicus) veligers has led us to examine whether these,and possibly other small zooplankters, may migrate in responseto a combination of tidal and diel stimuli. This paper usesHill's (1991) model to evaluate the horizontal transport effectsof such migrations. We demonstrate that most types of verticalmigration behavior reported in the literature (e.g. nocturnal,twilight, midnight sink) appear at different phases of the lunarcycle. Moreover, migrating in response to both of these cuesmay provide horizontal transport advantages if the zooplankteris very small (unable to migrate the full water column depth)and/or has difficulty determining its position in the watercolumn (especially if the behavior also holds it in regionsof increased shear). Such behavior need not interfere with otheradvantages of vertical migration, including avoiding predation,avoiding UV light, searching for patchy food, etc. Tidal/dielmigration may have distinct advantages for occupying new habitatsor coping with local changes associated with altered currentregimes. Because averaging the results of several days, samplingless frequently than every 2 h or sequential sampling of differentsites is likely to obscure the tidal portion of a tidal/dielmigration, such behavior could be common without being obviousto researchers. Aliasing of the lunar and solar cycles (a 14.8day period) may allow the detection of tidal period migrationsin long-term records with lower sampling frequencies.     

Inbreeding depression for various traits in two cultured populations of the American bay scallop, Argopecten irradians irradians Lamarck (1819) introduced into China

This paper examines the effect of inbreeding level of population on the magnitude of inbreeding depression expressed by comparing them between two cultured populations (A and B) in the hermaphroditic animal of the bay scallop Argopecten irradians irradians. Population A is expected to have less genetic variations and higher inbreeding level due to longer cultured history (20 generations) and less “ancestral” individuals (26 individuals) than population B due to shorter cultured history (4 generations) and more “ancestral” individuals (406 individuals). Two groups within each population were produced, one using self-fertilization and one using mass-mating within the same population. Selfed offspring (AS and BS) from two populations both had lower fitness components than their mass-mated counterparts (AM and BM) and exhibited inbreeding depression for all examined traits, e.g. lower hatching, less viability and slower growth, indicating that inbreeding depression is a common feature in this animal. Fitness components in all traits of offspring from population A significantly differed those from population B and the magnitude of inbreeding depression for all traits in population A with higher inbreeding level was significantly smaller than that in population B with lower inbreeding level, indicating that both fitness components and magnitude of inbreeding depression were significantly affected by inbreeding level of populations and genetic load harbored in population A may be partially purged through inbreeding. Moreover, the magnitude of inbreeding depression in the two populations both varied among traits and life history stages. The present results support the partial-dominance hypothesis of inbreeding depression.     

Membrane Transport in Isolated Vesicles from Sugarbeet Taproot : II. Evidence for a Sucrose/H-Antiport

The process of sucrose transport was investigated in sealed putative tonoplast vesicles isolated from sugarbeet (Beta vulgaris L.) taproot. If the vesicles were allowed to develop a steady state pH gradient by the associated transport ATPase and 10 millimolar sucrose was added, a transient flux of protons out of the vesicles was observed. The presence of an ATPase produced pH gradient allowed [¹⁴C]sucrose transport into the vesicles to occur at a rate 10-fold higher than the rate observed in the absence of an imposed pH gradient. Labeled sucrose accumulated into the sealed vesicles could be released back to the external medium if the pH gradient was dissipated with carbonylcyanide-m-chlorophenyl hydrazone (CCCP). When the kinetics of ATP dependent [¹⁴C]sucrose uptake were examined, the kinetic profile followed the simple Michaelis-Menten relationship and a Michaelis constant of 12.1 millimolar was found. When a transient, inwardly directed sucrose gradient was imposed on the vesicles in the absence of charge compensating ions, a transient interior negative membrane potential was observed. This membrane potential could be prevented by the addition of CCCP prior to sucrose or dissipated by the addition of CCCP after sucrose was added. These results suggest that an electrogenic H⁺/sucrose antiport may be operating on the vesicle membrane.     

Evidence for two additional common alleles at the PGM1 locus (Phosphoglucomutase-E.C.:2.7.5.1)

Summary Lysates of erythrocytes, leukocytes, lymphocytes, and extracts of sperms were investigated for the PGM₁ isozymes by three techniques: starch gel electrophoresis, high voltage thin-layer agarose gel electrophoresis, and thinlayer isoelectric focusing on polyacrylamide gel. On starch, only the well known common phenotypes 1, 2-1, and 2 were demonstrable. On agarose, different distances of the two main cathodal bands (a, b) among the phenotypes 2-1 were noted. Furthermore, on agarose, some types considered as homozygous on starch gel had a single, sharp banded pattern, while others were broad and blurred. Optimal separation was achieved by isoelectric focusing on polyacrylamide gel. In 291 leukolysates, 10 different phenotypes were identified. These are considered as gene products of 4 different common alleles at the PGM₁ locus as suggested by preliminary family investigations. In a random population from Hessen these four alleles, had the following frequencies: PGM ₁ ^a1 0.6186, PGM ₁ ^a2 0.1718, PGM ₁ ^a3 0.1426, and PGM ₁ ^a4 0.067. The preliminary designation a1, a2, a3 and a4 was chosen as the assumed polymorphism was demonstrated on acrylamide and agarose. The sum of the frequencies PGM ₁ ^a1 and PGM ₁ ^a3 (the gene products of which have apparently the same electrophoretic mobility on starch) is similar to the frequency of the old PGM ₁ ¹ allele (0.757) in Caucasoids, PGM ₁ ^a2 and PGM ₁ ^a4 have a frequency of 0.2388 corresponding with the frequency of the old allele PGM ₁ ² .     

Spectroscopic studies on cadmium (II)- and cobalt(II)-substituted metallothionein from the crab Cancer pagurus. Evidence for one additional low-affinity metal-binding site

The binding of diamagnetic Cd(II) and paramagnetic Co(II) ions to the metal-free form of crab, Cancer pagurus, metallothionein (MT) was studied by various spectroscopic techniques. Both reconstituted and native Cd(II)-MT containing 6 mol Cd(II)/mol protein display electronic absorption, circular dichroism (CD) and magnetic circular dichroism (MCD) spectra which were indistinguishable. The stoichiometric replacement of Cd(II) ions in native Cd(II)6-MT by paramagnetic Co(II) ions enabled the geometry of the metal-binding sites to be probed. The electronic absorption and MCD spectra of Co(II)6-MT revealed features characteristic of distorted tetrahedral tetrathiolate Co(II) coordination for all six metal-binding sites. The stepwise incorporation of Cd(II) and Co(II) ions into this protein was monitored by electronic absorption and CD, and by electronic absorption and EPR spectroscopy, respectively. The results indicate that the metal-thiolate cluster structure is generated when more than four metal ions are bound. Below this titration point separate tetrahedral tetrathiolate complexes exist. This suggests that the cluster formation occurs in a two-step process. Furthermore, the spectroscopic features in both Cd(II)- and Co(II)-metal derivatives above the full metal occupancy of six suggest the existence of one additional metal-binding site. The subsequent loss of one Cd(II) ion from crab Cancer Cd(II)7-MT in the gel filtration studies demonstrate the low metal-binding affinity of the latter site. While the spectroscopic properties indicate an exclusively tetrahedral type of metal-thiolate sulfur coordination for the binding of the first six metal ions, they suggest that the seventh metal ion is coordinated in a different fashion.     

mtDNA variability in two Bantu‐speaking populations (Shona and Hutu) from Eastern Africa: Implications for peopling and migration patterns in sub‐Saharan Africa

In this study, we report novel data on mitochondrial DNA in two of the largest eastern Bantu‐speaking populations, the Shona from Zimbabwe and the Hutu from Rwanda. The goal is to evaluate the genetic relationships of these two ethnic groups with other Bantu‐speaking populations. Moreover, by comparing our data with those from other Niger‐Congo speaking populations, we aim to clarify some aspects of evolutionary and demographic processes accompanying the spread of Bantu languages in sub‐Saharan Africa and to test if patterns of genetic variation fit with models of population expansion based on linguistic and archeological data. The results indicate that the Shona and Hutu are closely related to the other Bantu‐speaking populations. However, there are some differences in haplogroup composition between the two populations, mainly due to different genetic contributions from neighboring populations. This result is confirmed by estimates of migration rates which show high levels of gene flow not only between pairs of Bantu‐speaking populations, but also between Bantu and non‐Bantu speakers. The observed pattern of genetic variability (high genetic homogeneity and high levels of gene flow) supports a linguistic model suggesting a gradual spread of Bantu‐speakers, with strong interactions between the different lines of Bantu‐speaker descent, and is also in agreement with recent archeological findings. In conclusion, our data emphasize the role that population admixture has played at different times and to varying degrees in the dispersal of Bantu languages. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.     

Evidence for low‐level hybridization between two allochronic populations of the pine processionary moth,Thaumetopoea pityocampa (Lepidoptera: Notodontidae)

Divergence between populations sharing the same habitat can be initiated by different reproductive times, leading to allochronic differentiation. A spatially localized allochronic summer population (SP) of the pine processionary moth Thaumetopoea pityocampa, recently discovered in Portugal, occurs in sympatry with the local winter population (WP). We examined the level of genetic differentiation between the two populations and estimated the current gene flow within the spatial framework of their co‐occurrence. Mitochondrial data indicated that the two sympatric populations were genetically closer than other WP populations. Conversely, microsatellite genotyping uncovered greater differentiation between the two sympatric populations than between allopatric ones. While male trapping confirmed that reproduction of SP and WP occurred at distinct times, clustering approaches demonstrated the presence of a few LateSP individuals emerging within the WP flight period, although genetically identified as SP. We also identified rare recent hybridization events apparently occurring mainly in the margins of the current SP range. The ongoing gene flow detected between the ancestral and the emerging allochronic populations revealed an incomplete reproductive isolation, which must therefore be taken into account and integrated with studies focussed on ecological drivers, so that a complete understanding of the ongoing speciation process might be achieved.     

A computer model for hydrodynamic shearing of DNA (Gibb's phenomenon): Part II.

This paper presents an extension of the distribution proposed during hydrodynamic shearing of DNA. In the Fourier least square approximation of uniform random distribution or a square wave, Gibb's phenomena occur at the boundaries. The same behavior occurs at the boundaries of the DNA strands undergoing hydrodynamic shearing of DNA. This hypothesis is corroborated by results from a computer simulation of hydrodynamic shearing of DNA. The evidence helps confirm the kinetic experiments of Britten and Kohne [4]. Furthermore the results predict that sequence very near the end (0.2 LAMBDA) should be the most intact.     

Copper(II) binding to two novel histidine-containing model hexapeptides: evidence for a metal ion driven turn conformation

The solution conformation and the copper(II) binding properties have comparatively been investigated for the two novel hexapeptides Ac-HPSGHA-NH₂ (P2) and Ac-HGSPHA-NH₂ (P4). The study has been carried out by means of CD, NMR, EPR and UV-Vis spectroscopic techniques in addition to potentiometric measurements to determine the stability constants of the different copper(II) complex species formed in the pH range 3-11. The peptides contain two histidine residues as anchor sites for the metal ion and differ only for the exchanged position of the proline residue with glycine. CD and NMR results for the uncomplexed peptide ligands suggest a predominantly unstructured peptide chain in aqueous solution. Potentiometric and spectroscopic data (UV-Vis, CD and EPR) show that both peptides strongly interact with copper(II) ions by forming complexes with identical stoichiometries but different structures. Furthermore, Far-UV CD experiments indicate that the conformation of the peptides is dramatically affected following copper(II) complexation with the P4 peptide adopting a β-turn-like conformation.     

E.s.r., visible and SOD studies of imidazolate bridged Cu(2)(II,II), Cu(II)Zn(II) and Cu(II)Ni(II) complexes with pentamethyldiethylenetriamine as capping ligand: a plausible model for superoxide dismutase

X-band e.s.r. and electronic spectra of imidazolate bridged homobinuclear Cu-Cu complex, [(PMDT)Cu-Im-Cu(PMDT)](ClO(4))(3) and heterobinuclear Cu-Zn and Cu-Ni complexes, viz. [(PMDT)Cu-Im-Zn(PMDT)](ClO(4))(3), [(PMDT)Cu-Im-Ni(PMDT)] (ClO(4))(3), where PMDT=pentamethyldiethylenetriamine, Im=Imidazolate ion and related mononuclear complexes, [(PMDT)Cu(OH(2))](2+) and [(PMDT)Cu(ImH)](2+) have been described. Superoxide dismutase activities of these complexes have also been measured.     

Evidence for the formation of superoxide ion from the reaction of Cu(II)-ethylenediamine complex with hydrogen peroxide.

Formation of superoxide ion (O2-) from the reaction of CuII(en)2 (en: ethylenediamine) with hydrogen peroxide (H2O2) was first determined spectrophotometrically by use of nitro blue tetrazolium (NBT) in aqueous solutions. From this result, it has been suggested that superoxide ion is generated as an intermediate at the first reaction step between CuII(en)2 and H2O2.     

Optimized isolation procedure for obtaining strongly actinide binding exopolymeric substances (EPS) from two bacteria (Sagittula stellata and Pseudomonas fluorescens Biovar II)

Different chemical extractants (NaCl, EDTA, HCl and NaOH) and physical methods (ultrasonication and heating) were examined by their efficacies of extracting “attached” exopolymeric substances (EPS) secreted by marine bacterium Sagittula stellata (SS) and terrestrial bacterium Pseudomonas fluorescens Biovar II (PF). Extraction by 0.5 N HCl for 3 h was best for SS while extraction by 0.05 N NaCl for 3–5 h was regarded as optimal for PF. Improvements in EPS purification included a pre-diafiltration step to remove the broth material and reduce the solution volume, thus the usage of ethanol, and time. The EPS harvested at the optimal time and purified by the improved method were enriched in polysaccharides, with smaller amounts of proteins, thus having amphiphilic properties. Isoelectric focusing of ²³⁴Th or ²⁴⁰Pu labeled EPS showed both actinides were strongly bound to macromolecules with low pI, similar to reported marine or soil colloidal natural organic matter (NOM).     

Evidence for long isolation among populations of a pacific cycad: genetic diversity and differentiation in Cycas seemannii A.Br. (Cycadaceae)

The genetic structure of Cycas seemannii A.Br. (Cycadaceae), sampled throughout its range in Vanuatu, New Caledonia, Fiji, and Tonga, was studied using starch-gel electrophoresis. Twenty enzyme loci in 13 enzyme systems were examined. Low genetic diversity within populations (A = 1.2, P = 21.3, Ho = 0.047, and He = 0.057) and a high degree of differentiation among populations (F(ST) = 0.594) were found. This, together with low gene flow estimates, suggests genetic drift by isolation to have been most critical to the current genetic structure of the species. Inbreeding may occur to some extent (F(IS) = 0.165). The decline in abundance of C. seemannii, coupled with the low level of genetic diversity, suggest that conservation strategies are urgently needed.     

Evidence for genetic differentiation of Octopus vulgaris (Mollusca, Cephalopoda) fishery populations from the southern coast of Brazil as revealed by microsatellites

Octopus vulgaris is a cephalopod species in several oceans and commonly caught by artisanal and industrial fisheries. In Brazil, O. vulgaris populations are mainly distributed along the southern coast and have been subjected to intensive fishing during recent years. Despite the importance of this marine resource, no genetic study has been carried out to examine genetic differences among populations along the coast of Brazil. In this study, 343 individuals collected by commercial vessels were genotyped at six microsatellite loci to investigate the genetic differences in O. vulgaris populations along the southern coast of Brazil. Genetic structure and levels of differentiation among sampling sites were estimated via a genotype assignment test and F-statistics. Our results indicate that the O. vulgaris stock consists of four genetic populations with an overall significant analogous F_ST (Φ_CT = 0.10710, P < 0.05) value. The genetic diversity was high with an observed heterozygosity of Ho = 0.987. The negative values of F_IS found for most of the loci examined suggested a possible bottleneck process. These findings are important for further steps toward more sustainable octopus fisheries, so that this marine resource can be preserved for long-term utilization.     

A stereochemical model for phospholipids. II: Conformational analysis and molecular packing of phosphatidylethanolamine (PE)

A partition energy method procedure was applied to select the energetically favoured conformations of phosphatidylethanolamine (PE) as polar constituents of phospholipid molecules. The result indicated a large degree of freedom for the two torsion angles of the ester bond of the phosphate and a gauche, gauche star conformation for the ethane bond.A packing process of the molecule was carried out through a potential energy calculation by considering the conformers selected above, using previously published procedure and conventions. All the arrangements which possess the best packing energy values were characterised by an orientation of the PN dipolar segment parallel to the lattice plain. Rotation of the internal torsion angles and rotation in the eulerian space of the molecule produced differences in the charged groups that interact. An additional minimum was present in the energy packing process of those conformers which have the first torsion angle of the phosphate in a trans conformation. This minimum, which corresponds to an orientation of the molecule orthogonal to the lattice plane, requires a complete neutralisation of the point charges on the system.The results of the calculation underline the importance of changes in the behaviour of the polar group of the phospholipids in the packing process.     

Evidence for C---C coupling between two mutually cis carbon ligands, η-crotyl and aryl in organopalladium(II) complexes

Some (η³-crotyl) (2,5-dichlorophenyl)palladium(II) complexes containing phosphine and phosphite ligands Pd(η³-CH₂CH-CHMe)(Ar)(PR₃) (Ar = C₆H₃Cl₂-2,5) were isolated as crystalline solids or generated in solution. These existed as a mixture of two geometrical isomers arising from a different way of risposition of the crotyl-methyl group and the aryl ligand. The electronic nature of the PR₃ ligand controlled the relative rates of the interconversion between the two isomers and the reductive elimination of the complexes which released MeCH=CHCH₂Ar and CH₂=CHCH(Me)(Ar). Electron-withdrawing phosphite ligands were particularly effective in enhancing the reductive elimination rate, making the contribution of the isomerization path almost negligible and allowing the formation of two coupling products to be followed separately by spectroscopic means. The observations demonstrated the occurrence of C---C coupling between mutually cis carbon ligands in (η³-allyl)(hydrocarbyl)palladium(II) complexes. The η¹-crotyl complex, (Pd(η¹-CH₂CH=CHMe)(Ar) (dppen) (dppen = cis-Ph₂PCH=CHPPh₂) was isolated and shown to exist as a sole regio-isomer in solution. Reductive elimination of this η¹-crotyl complex gave MeCH=CHCH₂Ar exclusively.     

中国橐吾属(菊科-千里光族)的分类学研究(二)：植夫橐吾的名实订正

通过文献和标本考证,发现《中国植物志》第77卷第2分册和《Flora of China》第20~21卷中均误将黑穗橐吾(Ligularia melanothyrsa Hand.-Mazz.)鉴定为植夫橐吾(L. fangiana Hand.-Mazz.),而真正的植夫橐吾应处理为川鄂橐吾[L. wilsoniana (Hemsl.) Greenm.]的异名。     

Evidence for search image in blackbirds (Turdus merula L.): short-term learning

A ‘search image’ is acquired as a result of a change in the ability of a predator to detect cryptic familiar prey. Blackbirds were presented with artificial prey dyed either to match the colour of the background (cryptic prey) or to contrast with the background (conspicuous prey). The results of experiment 1 provide some evidence that 10 wild blackbirds had more difficulty detecting cryptic prey than conspicuous prey. Detailed analysis of experiments 2 (11 wild blackbirds) and 3 (six captive blackbirds) revealed subtle changes in the reactions of the birds to cryptic prey. At first these birds were unable to detect cryptic prey, but subsequently improved their ability to detect such food. This short-term change is interpreted as evidence for search images.