Experimental evidence of the grazing impact of <Emphasis Type="Italic">Boeckella poppei</Emphasis> on phytoplankton in a maritime Antarctic lake

The zooplankton biomass of Lake Boeckella (Hope Bay, Antarctic Peninsula) is strongly dominated by the calanoid copepod Boeckella poppei Mrázek. This work analyses the grazing impact of this copepod on the two dominant fractions of phytoplankton, pico- and nanoplankton, and on the bacterioplankton. By means of in-situ experiments using microcosms, the following hypotheses were tested: (a) the early stages of the copepod mainly graze on phytoplankton; (b) the pre-adult and adult stages graze on phytoplankton and benthic algae. Copepods were separated into two groups of maturity: early stages, and pre-adult and adult stages. The following treatments were performed: (1) only nano- and picoplankton, (2) nano- and picoplankton+periphyton, and (3) only periphyton, for each one of the two copepod maturity groups, and (4) control (without copepods). The variation in nano-phytoplankton density was analysed after 2 and 4 days. The results determined a significant grazing on the nano-phytoplankton fraction in all microcosms containing copepods of both maturity groups (P<0.01). The effect on the nano-phytoplankton was greater when the copepods did not have another source of food (P<0.01). No significant differences between the maturity groups were observed (P>0.05). We also conclude that the copepods use the periphyton as an alternative source of food, which was corroborated by the analysis of gut content. In general, no significant differences among treatments were recorded for the pico-sized fraction (pico-phytoplankton and bacterioplankton), which would suggest that no direct grazing on this fraction exists.     

Phylogeographical analysis reveals multiple conservation units in brook lampreys Lampetra planeri of Portuguese streams

The populations of brook lamprey Lampetra planeri of Portuguese Rivers were analysed phylogeographically using a fragment of 644 bp of the mitochondrial control region of 158 individuals from six populations. Samples representing L. planeri and migratory lampreys Lampetra fluviatilis of rivers draining to the North Sea and the Baltic Sea were also included to assess the relationships of Portuguese samples. The data support a clear differentiation of all the populations studied. Several populations, which are isolated among themselves and also from the migratory lampreys, proved to be entirely composed of private haplotypes, a finding that supports some time of independent evolutionary history for these populations. This, combined with the geographic confinement to small water bodies, justifies the recognition of at least four conservation units in the Portuguese rivers Sado, São Pedro, Nabão and Inha.     

Paleobiogeography of two Iberian endemic cyprinid fishes (Chondrostoma arcasii-Chondrostoma macrolepidotus) inferred from mitochondrial DNA sequence data

We tested different hypotheses related to the origin and evolution of the endemic Iberian fishes Chondrostoma arcasii and Chondrostoma macrolepidotus from northern and central regions of the Iberian Peninsula. We evaluated the monophyly of the populations within each species and sought to determine if diversification of the populations coincided in time with the formation of the Iberian drainages dating back to the upper Pliocene (2.5-1.8 million years ago). A molecular phylogenetic analysis of the mitochondrial cytochrome b gene showed that the different populations of the northern Iberian Peninsula are clustered into five phylogroups and do not fit into the dichotomy C. arcasii-C. macrolepidotus. We propose that species differentiation occurred prior to the upper Pliocene formation of the present hydrographic basins and that endorheic basins, a system of inland lakes found in Spain during the Mio-Pliocene, played an important role in this diversification and differentiation process.     

Diabetes induces changes of catecholamines in primary mesangial cells

Diabetes mellitus is a frequent cause of kidney function damage with diabetic nephropathy being predominantly related to glomerular dysfunction. Diabetes is capable of interfering with distinct hormonal systems, as well as catecholamine metabolism. Since mesangial cells, the major constituent of renal glomerulus, constitute a potential site for catecholamine production, the present study was carried out to investigate alterations in catecholamine metabolism in cultured mesangial cells from the nonobese diabetic mouse, a well-established model for type I diabetes. We evaluated mesangial cells from normoglycemic and hyperglycemic nonobese diabetic mice, as well as cells from normoglycemic Swiss mice as control. Mesangial cells from normoglycemic mice presented similar profiles concerning all determinations. However, cells isolated from hyperglycemic animals presented increased dopamine and norepinephrine production/secretion. Among the studied mechanisms, we observed an upregulation of tyrosine hydroxylase expression accompanied by increased tetrahydrobiopterin consumption, the tyrosine hydroxylase enzymatic cofactor. However, this increase in synthetic pathways was followed by decreased monoamine oxidase activity, which corresponds to the major metabolic pathway of catecholamines in mesangial cells. In addition, whole kidney homogenates from diabetic animals also presented increased dopamine and norepinephrine levels when compared to normoglycemic animals. Thus, our results suggest that diabetes alters catecholamine production by interfering with both synthesizing and degrading enzymes, suggesting a possible role of catecholamine in the pathogenesis of acute and chronic renal complications of diabetes mellitus.     

Heterozygous indels as useful tools in the reconstruction of DNA sequences and in the assessment of ploidy level and genomic constitution of hybrid organisms.

In this paper we describe a simple approach using double peaks in chromatograms generated as artefacts in the vicinity of heterozygous indels, to identify the specific sequences present in individual strands of a given DNA fragment. This method is useful to assign bases in individuals that are heterozygous at multiple sites. In addition, the relative sizes of the double peaks help to determine the ploidy level and the relative contribution of the parental genomes in hybrids. Our interpretation was confirmed with the analysis of artificial mixtures of DNA of two different species. Results were robust with varying PCR and sequencing conditions. The applicability of this method was demonstrated in hybrids of the Squalius alburnoides complex and in heterozygotes of Chondrostoma oligolepis. Far from being limited to these fish models and the gene where it was tested (beta-actin), this sequence reconstruction methodology is expected to have a broader application.     

Fertile triploid males: an uncommon case among hybrid vertebrates

The endemic Iberian minnow Squalius alburnoides is a complex of fishes of hybrid origin including both males and females with distinct ploidy levels and varying proportions of the parental genomes. In this paper we demonstrated that in contrast to many vertebrate hybrid lineages the sperm of triploid hybrid males of S. alburnoides is viable and fully functional. Flow cytometry and analysis of sequences of a fragment of the beta-actin nuclear gene applied to progenitors and offspring evidenced that these males produced their sperm clonally, as already described for diploid hybrids. The presence of different types of fertile males (nonhybrid diploids with normal meiosis and both diploid and triploid hybrids) coupled with hybridogenetic meiosis in females endows this vertebrate complex with a high level of independence from other species and contributes to maintain its genetic variability.     

Identification of ESUs in the critically endangered Portuguese minnow <Emphasis Type="Italic">Chondrostoma lusitanicum</Emphasis> Collares-Pereira 1980, based on a phylogeographical analysis

In this paper, we analysed the phylogeography of the Critically Endangered fish Chondrostoma lusitanicum (Cyprinidae) endemic to Portugal. A fragment of the mitochondrial cyt b gene and one from the nuclear beta-actin gene were sequenced. The results support recognition of 3 ESU's distributed as follows: 1) Sado River, 2) the Tagus River basin and 3 independent nearby coastal rivers (collectively named "West") and 3) Lagoa de Albufeira, a small coastal lagoon between Tagus and Sado basins.     

Establishment of a coastal fish in the Azores: recent colonisation or sudden expansion of an ancient relict population?

The processes and timescales associated with ocean-wide changes in the distribution of marine species have intrigued biologists since Darwin''s earliest insights into biogeography. The Azores, a mid-Atlantic volcanic archipelago located >1000 km off the European continental shelf, offers ideal opportunities to investigate phylogeographic colonisation scenarios. The benthopelagic sparid fish known as the common two-banded seabream (Diplodus vulgaris) is now relatively common along the coastline of the Azores archipelago, but was virtually absent before the 1990s. We employed a multiple genetic marker approach to test whether the successful establishment of the Azorean population derives from a recent colonisation from western continental/island populations or from the demographic explosion of an ancient relict population. Results from nuclear and mtDNA sequences show that all Atlantic and Mediterranean populations belong to the same phylogroup, though microsatellite data indicate significant genetic divergence between the Azorean sample and all other locations, as well as among Macaronesian, western Iberian and Mediterranean regions. The results from Approximate Bayesian Computation indicate that D. vulgaris has likely inhabited the Azores for ∼40 (95% confidence interval (CI): 5.5–83.6) to 52 (95% CI: 6.32–89.0) generations, corresponding to roughly 80–150 years, suggesting near-contemporary colonisation, followed by a more recent demographic expansion that could have been facilitated by changing climate conditions. Moreover, the lack of previous records of this species over the past century, together with the absence of lineage separation and the presence of relatively few private alleles, do not exclude the possibility of an even more recent colonisation event.