Fluctuation of algal alkaline phosphatase activity and the possible mechanisms of hydrolysis of dissolved organic phosphorus in Lake Barato

For freshwater cyanobacteria, the autofluorescence of phycocyanin is quite high while the in vivo fluorescence (IVF) yield of chlorophyll-a is relatively low, apparently because of low chlorophyll concentrations associated with photosystem II. In eucaryotic phytoplankton, even those with phycobili-protein accessory pigments (e.g. some cryptophytes), the opposite is true. Thus, an IVF ratio which relates phycocyanin to chlorophyll-a signals could be a good index of relative cyanobacterial abundance in the field. Spectrofluorometric scans of whole cells from laboratory cultures indicated that the ratio Em₆₆₀ @ Ex₆₃₀/Em₆₈₀ @ Ex₄₃₀ could be a very sensitive cyanobacterial indicator. Tandem flowthrough fluorometers were then fitted with the appropriate interference filters and their discriminatory power was evaluated with mixtures of cyanobacterial and eucaryotic phytoplankton. Although subject to many of the constraints of other IVF assays, tandem fluorometry should be particularly appropriate for real-time mapping of the relative spatial and temporal distributions of broad phytoplankton taxa in continuous vertical of horizontal profiles in lakes.     

EVIDENCE FOR A MOSAIC HYBRID ZONE IN THE GRASS SHRIMP PALAEMONETES KADIAKENSIS (PALAEMONIDAE) AS REVEALED BY MULTIPLE GENETIC MARKERS

Molecular techniques provide powerful tools for studying the geographic structure of hybrid zones and the dynamics of gene exchange between incipient species. We examined allozyme variation at five loci (PGM, GPI, MDH-1, MDH-2, and LDH) for 27 populations of Palaemonetes kadiakensis from the central, coastal, and eastern regions of Texas. Central Texas populations of P. kadiakensis exhibited highly significant linkage disequilibrium and departures from Hardy-Weinberg genotype proportions. In populations with linkage disequilibrium, allelic differences at GPI defined two types of P. kadiakensis, designated A and B. Both types existed in central Texas with little or no evidence of interbreeding, whereas the populations from all other localities showed complete introgression of type B alleles into the type A gene pool. We also examined ribosomal DNA (rDNA) and mitochondrial DNA (mtDNA) variation in a subset of populations, chosen to cover a range of geographic locations and levels of linkage disequilibrium. Two groups of mtDNA haplotypes and two restriction fragment patterns for the rDNA corresponded to allozyme type A and B individuals in populations exhibiting linkage disequilibrium. In populations with ongoing hybridization, all hybrid animals (N= 15) exhibited type A mtDNA. Exhibition of type A mtDNA indicated that type A females had mated successfully with type B males, but type B females had not mated successfully with type A males. Genotype distributions suggest reduced reproduction by hybrid offspring in central Texas populations. These patterns are consistent with a mosaic model of hybrid zone dynamics.     

In vivo control of Mycosphaerella pinodes on pea leaves by a crude bulb extract of Eucomis autumnalis

We previously reported on the in vitro antifungal activity of a crude whole plant extract from Eucomis autumnalis against seven economically important plant pathogenic fungi. A crude extract of the bulb showed similar in vitro mycelial growth inhibition of the same plant pathogenic fungi as well as that of an eighth fungus, Mycosphaerella pinodes, the cause of black spot or Ascochyta blight, in peas. Subsequently, fourth internode leaves were removed from 4 wk old pea plants, placed on moist filter paper in Petri dishes and inoculated with an M. pinodes spore suspension before and after treatment with the extract. The control of Ascochyta blight by different concentrations of the crude E. autumnalis extract was followed in vivo by leaf symptoms over a 6 day period at 20°C in a growth cabinet. The crude extract prevented M. pinodes spore infection of the leaves when the leaves were inoculated with spores both before or after treatment with the extract, confirming complete inhibition of spore germination. The crude E. autumnalis extract showed no phytotoxic reaction on the leaves even at the highest concentration applied.     

Mitochondrial phylogeography and population history of pine martens Martes martes compared with polecats Mustela putorius

The flora and fauna of Europe are linked by a common biogeographic history, most recently the Pleistocene glaciations that restricted the range of most species to southern refugial populations. Changes in population size and migration, as well as selection, have all left a signature on the genetic differentiation. Thus, three paradigms of postglacial recolonization have been described, inferred from the patterns of DNA differentiation. Yet some species, especially wide-ranging carnivores, exhibit little population structuring between the proposed refugia, although relatively few have been studied due to the difficulty of obtaining samples. Therefore, we investigated mitochondrial variation in pine martens, Martes martes, in order to understand the extent to which they were affected by glacial cycles, and compared the results with an analysis of sequences from polecats, Mustela putorius. A general lack of ancient lineages, and a mismatch distribution that is consistent with an expanding population, is evidence that the present-day M. martes and Mu. putorius in central and northern Europe colonized from a single European refugium following a recent glaciation. There has also been interspecific mitochondrial introgression between M. martes and the sable M. zibellina in Fennoscandia.     

PHOTOACCLIMATION IN THE TROPICAL CORALLINE ALGA HYDROLITHON ONKODES (RHODOPHYTA, CORALLINACEAE) FROM A FRENCH POLYNESIAN REEF

Pigment concentration, in vivo absorption, and photosynthetic parameters of the coralline alga Hydrolithon onkodes (Heydrich) Penrose and Woelkerling were compared among samples from a lagoon and from a reef crest of Tahiti Island. Four groups of specimens were considered, differing in their natural exposure to PAR. For specimens collected from the lagoon, the tissues from low-light samples had significantly higher pigment concentration, particularly chl a and phycobilins, compared with the high-light exposed plants that contained more total carotenoids. The in vivo absorption spectra normalized to chl a (called a* values) also revealed differences. The low-light samples had a reduced absorption capacity and a well-marked phycobilin absorption signature, whereas sunlit samples showed a greater absorption at wavelengths absorbed mainly by chl a and carotenoids. The decrease of a* when pigment concentration increased is interpreted as a consequence of the pigment packaging. Significantly lower α (chlorophyll basis) and higher E_k values were found in the shaded plants. The values of P _max for the four groups of specimens were not significantly different. The samples showed various degrees of photoinhibition depending on the light exposure during growth, and this effect was more pronounced in the shaded plants. The specimens from the reef crest deviate from the general model presented for the lagoon samples and show a mix of sun- and shade-exposed characteristics. We have shown that the coralline alga H. onkodes responds to its light environment, probably by acclimation rather than ecotypic genetic variation, by adjusting its physiology, but some morphological differences are also involved. Photoacclimation can explain partly the wide distribution of this species over the reef ecosystem and its major contribution to the building of the reef.     

Presence of haemocyte-like cells in coccinellid reflex blood

Abstract.  Contrary to current assumptions, the reflex blood of two-spot ladybirds, Adalia bipunctata , and seven-spot ladybirds, Coccinella septempunctata , contains haemocyte-like cells. Furthermore, DNA can be extracted and amplified from coccinellid reflex blood, confirming the presence of haemocyte-like cells and demonstrating a nondestructive method of DNA extraction.     

Response of muscle-based biochemical condition indices to short-term variations in food availability in post-flexion reared sea bass Dicentrarchus labrax (L.) larvae

Six condition indices based on RNA, total soluble protein and two metabolic enzymes [lactate dehydrogenase (LDH) and citrate synthase (CS)] were analysed in muscle tissue of individual larvae, post-flexion reared sea bass Dicentrarchus labrax using DNA and total soluble protein as standards for size. In addition, the effect of 2 days of food deprivation on the cell proliferation rates was assessed. The RNA:DNA best reflected short-term changes in feeding conditions. If standardized by DNA content, LDH activity was a better indicator of condition than any other index but RNA:DNA. Further, the analysis of cell proliferation rates in muscle from 26 day-old larvae proved useful in distinguishing continuously fed larvae from individuals subjected to 2 days of fast.     

Transfection of a DNA/protein complex into nuclei of mammalian cells using polyoma capsids and electroporation

We used empty capsids ofpolyoma virus to transfer DNA fragments and DNA/protein complexes into human cells. We encapsulated labeled and unlabeled single stranded DNA fragments by viral capsids. A complex of DNA with a DNA binding protein, recA, will also be taken up by the capsids, whereas the free protein is not incorporated. We further compared this gentle biological method of DNA transfection with a well-established physical method, electroporation. Electroporation also allows the transfer of DNA as well as protein into cells, although there is no proof that a DNA/protein complex can survive the procedure functionally. Whereas the viability of capsid transfected cells is unaffected (100%), electroporation reduces the viability to 90–95%. On the other hand, the amount of DNA found in the nucleus of electroporated cells is higher than for cells treated with loaded viral capsids.