Migratory behaviour and otolith chemistry suggest fine-scale sub-population structure within a genetically homogenous Atlantic Cod population

The question whether temperate marine fishes typically consist of self-sustaining populations or “open” populations still remains unresolved. At the heart of this population connectivity problem lays the nature of the stock separation mechanisms. Fish populations could be segregated either by environmental forcing, accompanied with opportunistic recruitment of juveniles to spawning areas, or by philopatric behaviours (i.e., inclination of an individual to return to or remain in its natal area). Here we report three, partly independent, studies on Atlantic Cod (Gadus morhua) stock separation in the Kattegat and Öresund (eastern North Sea): characterisation of spawning aggregations with genetic markers, tagging experiments, and analysis of chemical constituents in otolith cores of recaptured fish that could be linked to a specific spawning site. While the genetic investigation showed no population segregation, the observed migratory patterns indicated three separate spawning sites at close distances. The natal dependence on the choice of spawning site was tested by measuring the contents of various trace elements in the otolith core of recaptured tagged fish. Quantification of the trace elements: Ba, Br, Co, Cr, Cu, Fe, Mn, Mo, Ni, Sr, Ti, and Zn expressed as ratios to Ca were obtained using scanning micro PIXE. These results indicated that natal origin could be differentiated between spawning sites, supporting the hypothesis that natal homing is an important stock separating mechanism even over short distances (<100 km).     

Insight into Danube sturgeon life history: trace element assessment in pectoral fin rays

Sturgeon populations in the Danube River have experienced severe decline during the last several decades, mostly due to the poorly regulated fishery, river fragmentation and water pollution. This study focuses on gaining better understanding of sturgeon life history primarily by addressing the assessment of microelement accumulation in sturgeon pectoral fin rays, especially of strontium and calcium, as a method that can reveal migration patterns of anadromous sturgeons. Analysis was performed on pectoral fin samples of three anadromous Danube sturgeon species (beluga, Russian sturgeon and stellate sturgeon) by the use of a Nuclear Microprobe technique. The most frequent pattern in analyzed samples was represented by a low Sr:Ca ratio in the innermost annuli, followed by an increased ratio in the middle annuli segment, and often with a decreased ratio in the outermost annuli. Probability density estimate has revealed three distinguished maxima of the Sr:Ca ratio, 7.08 × 10⁻³, 8.98 × 10⁻³ and 9.90 × 10⁻³, which might correspond, respectively, to fresh, brackish and saltwater. Although the analysis of the Sr:Ca ratio in sturgeon pectoral fin rays has revealed changes that might indicate probable migration between habitats with different water salinity, further studies are needed for improvement of this method. This study represents the first analysis of this kind that was conducted on sturgeon species from the Black Sea basin.     

AIDS and associated malignancies

INTRODUCTION It has been over twenty years since the onset of the AIDS epidemic, and in spite of the tremendous progress made towards the understanding of the disease, the virus that causes the disease and the development of highly ef- fective anti-retrov…     

Fractionation of protein components of plasma membranes from the electric organ of Torpedo marmorata

A procedure has been developed for the separation of intrinsic proteins of plasma membranes from the electric organ of Torpedo marmorata. (Na⁺ + K⁺)-ATPase, nicotinic acetylcholine receptor and acetylcholinesterase remained active after solubilization with the nonionic detergent dodecyl octaethylene glycol monoether (C₁₂E₈). These components could be separated by ion exchange chromatography on DEAE-Sephadex A-25. Fractions enriched in ouabain-sensitive K⁺-phosphatase or (Na⁺ + K⁺)-ATPase activity showed two bands in sodium dodecyl sulphate polyacrylamide gel electrophoresis corresponding to the α- and β-subunits. The (Na⁺ + K⁺)-ATPase was shown to have immunological determinants in common with a 93 kDa polypeptide which copurified with the nicotinic acetylcholine receptor, also after solubilization in Triton X-100 and chromatography on Naja naja siamensis α-toxin-Sepharose columns. The data suggest that the α-subunit of (Na⁺ + K⁺)-ATPase associates with the acetylcholine receptor in the membranes of the electric organ.     

Removal or oxidation of surface membrane sialic acid inhibits formyl-peptide-induced polymorphonuclear leukocyte chemotaxis

Polymorphonuclear leukocyte (PMN) surface membrane glycoproteins are probably involved in the phenomenon of stimulus-response coupling. Consequently, we examined the effects of either removal or oxidation of surface membrane-associated sialic acid residues on some responses of human PMN to chemotactic factors. Treatment of human PMN with either neuraminidase or sodium metaperiodate did not affect the ability of these cells to migrate randomly, but did inhibit their ability to respond chemotactically to the synthetic peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP). Treated PMN responded normally, however, to the complement-derived peptide C5a, and to the lipoxygenase product leukotriene B4. Enzymatic removal or oxidation of membrane sialic acid residues did not affect either FMLP-induced PMN degranulation or FMLP-induced generation by PMN of superoxide anion radicals. Removal of sialic acid did not significantly alter specific binding of [3H]FMLP to its receptor(s) on the PMN membrane. These findings indicate that sialic acid residues on the PMN surface membrane play an important role in modulating PMN responses to FMLP.     

Flexible modes of anadromy in Baltic sea trout: making the most of marginal spawning streams

From examination of the ratios of strontium to calcium laid down as a lifetime record in the otoliths of sea trout Salmo trutta from Gotland, Baltic Sea, it was found that: (1) the shortest stream was used mostly by precociously emigrant or coastally hatched spawners; (2) longer streams had more fish that underwent normal smoltification; (3) sea-caught fish were predominantly coastally hatched (presumably near stream mouths). Furthermore, some otoliths showed no evidence of a freshwater history at all, raising the possibility of a contingent of the coastal population that does not depend on riverine spawning. The results emphasize the importance of the coastal zone as natal and early life habitat for sea trout in the Baltic, particularly with respect to a potential change to a warmer climate which may exacerbate conditions within small, ephemeral trout streams.     

Molecular phylogeography of Carapichea ipecacuanha,an amphitropical shrub that occurs in the understory of both semideciduous and evergreen forests

The medicinal shrub Carapichea ipecacuanha (ipecac) is an amphitropic species with three disjunct areas of distribution. In the Brazilian Atlantic and Amazonian ranges, the species was associated mostly with the understory of seasonal semideciduous forests, whereas in the Central American–Colombian range, the species occurred in the understory of moist evergreen forests. We examined the phylogeographic structure of ipecac using chloroplast trnT‐trnL and nuclear internal transcribed spacer (ITS) sequences from 120 and 46 specimens, respectively. To complement existing data on root alkaloid profiles, we used high‐performance liquid chromatography to assess the levels of emetine and cephaeline in 33 specimens from the two Brazilian ranges. The three ranges shared neither nuclear nor chloroplast haplotypes. The phylogeographic structures showed an uneven distribution of genetic diversity, sharp breaks and high levels of genetic differentiation among ranges. Our results suggest that the extant populations are descendents of at least four distinct ancestral lineages. The Atlantic ipecacs showed higher levels of genetic diversity than ipecacs from the other two ranges; it is likely that they derive from two ancestral lineages, with long‐term persistence in that region. The Amazonian ipecacs were monomorphic with respect to the ITS and cpDNA sequences, which supports the view that there was a recent expansion from a single parental source after a strong genetic bottleneck. The existence of a fourth distinct lineage is apparent from the high levels of genetic and chemical differentiation that we identified in the Central American–Columbian ipecacs.