BackgroundStearoyl-CoA desaturases (SCDs) are key enzymes involved in de novo monounsaturated fatty acid synthesis. They catalyze the desaturation of saturated fatty acyl-CoA substrates at the delta-9 position, generating essential components of phospholipids, triglycerides, cholesterol esters and wax esters. Despite being crucial for interpreting SCDs roles across species, the evolutionary history of the SCD gene family in vertebrates has yet to be elucidated, in particular their isoform diversity, origin and function. This work aims to contribute to this fundamental effort.ResultsWe show here, through comparative genomics and phylogenetics that the SCD gene family underwent an unexpectedly complex history of duplication and loss events. Paralogy analysis hints that SCD1 and SCD5 genes emerged as part of the whole genome duplications (2R) that occurred at the stem of the vertebrate lineage. The SCD1 gene family expanded in rodents with the parallel loss of SCD5 in the Muridae family. The SCD1 gene expansion is also observed in the Lagomorpha although without the SCD5 loss. In the amphibian Xenopus tropicalis we find a single SCD1 gene but not SCD5, though this could be due to genome incompleteness. In the analysed teleost species no SCD5 is found, while the surrounding SCD5-less locus is conserved in comparison to tetrapods. In addition, the teleost SCD1 gene repertoire expanded to two copies as a result of the teleost specific genome duplication (3R). Finally, we describe clear orthologues of SCD1 and SCD5 in the chondrichthian, Scyliorhinus canicula, a representative of the oldest extant jawed vertebrate clade. Expression analysis in S. canicula shows that whilst SCD1 is ubiquitous, SCD5 is mainly expressed in the brain, a pattern which might indicate an evolutionary conserved function.ConclusionWe conclude that the SCD1 and SCD5 genes emerged as part of the 2R genome duplications. We propose that the evolutionary conserved gene expression between distinct lineages underpins the importance of SCD activity in the brain (and probably the pancreas), in a yet to be defined role. We argue that an expression independent of an external stimulus, such as diet induced activity, emerged as a novel function in vertebrate ancestry allocated to the SCD5 isoform in various tissues (e.g. brain and pancreas), and it was selectively maintained throughout vertebrate evolution.

Background, aim and scopeRia de Aveiro (Portugal) is a shallow coastal lagoon of high economic and ecological importance. Hardly any data on its chemical pollution by polar organic pollutants are available in literature. This study focused on the presence and sources of a series of phenolic endocrine-disrupting compounds (EDCs) in this area, including parabens, alkylphenolic compounds and bisphenol-A (BPA). A number of possible sources of pollution are present in the area, including the large harbours present in the lagoon, the city of Aveiro and the rivers discharging into the area. A recently constructed submarine wastewater outfall, located a few kilometres from the lagoon inlet has also been suggested as a possible source of pollution to Ria de Aveiro in several publications. The aim of the current field study was to investigate the occurrence and main sources of phenolic endocrine disruptors in Ria de Aveiro.Materials and methodsAn extensive sampling campaign was performed, with surface water and wastewater grab samples taken at over 50 locations, in duplicate on different days. Samples were treated using solid phase extraction and analysed by liquid chromatography tandem mass spectrometry.Results and discussionConcentrations in lagoon water were generally low: not exceeding 20 ng/L for most analytes. Levels in river water exceeded those in the lagoon by a factor 3 to 500 (o-phenylphenol (PhP) and nonylphenoxy ethoxy acetic acids (A9PEC), respectively), with concentrations up to 700 ng/L for BPA and 7,300 ng/L for A9PEC. Samples from the harbours showed EDC levels similar to those in the rest of the lagoon, but in the city of Aveiro, elevated concentrations were observed for alkylphenol ethoxylates (A9PEO), A9PEC, PhP and BPA. Wastewater effluents showed low levels for parabens, whilst alkylphenolic compounds reached several micrograms per litre. The effluents are discharged into the ocean via a submarine outfall, but as marine water near the outfall showed slightly elevated concentrations only for A9PEO, it does not seem to be a significant source of these EDCs for the area.ConclusionsAll the studied phenolic EDCs were detected in the study area, with high levels found in some of the rivers discharging into the lagoon, and generally low concentrations in the lagoon itself. The main sources for all investigated EDCs were the rivers Caster and Antuã which discharge into the lagoon. The city of Aveiro was identified as a secondary source. As the tidal water exchange volume is much larger than the freshwater input from the rivers, concentrations of phenolic EDCs remained low in the lagoon.Electronic supplementary materialThe online version of this article (doi:10.1007/s11356-009-0275-5) contains supplementary material, which is available to authorized users.

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Dietary long chain polyunsaturated fatty acids (FA) have been recognized of crucial importance in early development of vertebrates, contributing to the impressive morphological and physiological changes both as building blocks and to energy production. The importance of lipids along development depends on ontogenetic, phylogenetic and environmental parameters. The expression patterns of FA metabolism genes have not been characterized in developing fish embryos nor compared to lipid class profiles. Full lipid metabolism only occurred after hatching, as revealed by alterations in lipid profiles and FA gene expression. Nonetheless, transcriptional changes of some FA genes were already present in embryos at notochord formation. Many genes displayed an expression profile opposed to the decrease of lipids along the development, while others responded solely to starvation. Transcription of most genes involved in FA metabolism had a strong correlation to PPARs' mRNA levels (α1, α2, β, γ). The comparison of mRNA expression of the genes with the lipid profiles produced new insights into the FA metabolism and regulation during the development of turbot larvae, providing the basis for future studies including comparative approaches with other vertebrate species.

Nucella lapillus (L.) is a marine gastropod mollusc widely used as a bioindicator of TBT pollution in the North Atlantic coastlines. The species reproductive cycle and the male penis length seasonal/spatial variation were studied at a single site at Aveiro seashore (NW Portugal) between December 2005 and June 2007. The main objective of this work is to assess if the "Relative Penis Size Index" (RPSI)--an important imposex assessment index--varies seasonally and spatially in the same sampling site and how this can affect results obtained in imposex monitoring programmes. Animals able to reproduce were found every month but a seasonal pattern in N. lapillus reproductive cycle was evident. Female gametogenic maturation varied seasonally and a decrease in capsule gland volume and condition factor occurred in late summer/early autumn. The gametogenesis in males did not show a significant seasonal variation as in females but the condition factor, penis length, amount of sperm and prostate volume also diminished in late summer/early autumn. On the other hand, males that were close to egg capsules clusters had larger penises than those far away from clusters. The temporal and spatial male penis length variation introduces a bias on imposex assessment results when using RPSI and the magnitude of the error involved is evaluated for different TBT pollution levels scenarios. We consider that RPSI provides interesting and complementary information that should not be excluded from monitoring programmes, but temporal or spatial comparisons of imposex should be based on other more reliable imposex indices like the VDSI.