Polyamine Content Related to Seed Storage Performance in Zea mays

As part of a search for biochemical indicators of seed withgood survival characteristics during storage, polyamine (PA)levels were measured in embryos for Zea mays seeds. PA levelswere determined in individual embryos of Mean Generation Analysis(MGA) of crosses between lines which show good (C²) and poor(C⁶) storage characteristics. A correlation was found betweenhigher PA contents (putrescine and spermidine) and superiorsurvival characteristics within the populations that were analysedby MGA. Titres of putrescine (PUT) and spermidine (SPD) showedthat three-quarters of the F² resembled the C² parent and aquarter resembled the C⁶ parent. Furthermore, the backcrossC⁶F¹ showed that half of the embryos had PUT levels above theparental C⁶ line. A maternal inheritance effect was not observed.Neither spermine nor cadaverine content was correlated withthe survival inheritance pattern. Given the survival kineticsobtained, it is suggested that both the PA titres and the seedsurvival characteristics are determined by nuclear dominantfactors. Key words: Polyamines, Zea mays, seeds     

Can a sponge feeder be a herbivore? Tylodina perversa (Gastropoda) feeding on Aplysina aerophoba (Demospongiae)

Feeding biology in mollusks has important biological, ecological and evolutionary implications because many of the characteristics we observe in mollusks arise from their co-evolution with diet organisms. We investigated the relationship between the opisthobranch Tylodina perversa and the sponges Aplysina aerophoba and Aplysina cavernicola in order to ascertain the trophic interactions between them. The opisthobranch preferred specimens of Aplysina aerophoba inhabiting shallow overdeep waters, ectosome of Aplysina aerophoba over choanosome, and showed no preference for Aplysina cavernicola . The sponge Aplysina cavernicola lacks the cyanobacteria abundant in the ectosome of Aplysina aerophoba . Our study shows that the opisthobranch Tylodina perversa actively selects for sponges or sponge zones with high concentration of cyanobacteria, i.e. only a fraction of the ingested material is of animal origin. Addition of cyanobacteria to symbiont-free sponge material induced a shift in mollusk preference. Our results cast doubt over the widely recognized qualification of Tylodina perversa as a carnivorous sponge feeder and show evidence that cyanobacteria determine the opisthobranch food selection. Whether this is an isolated example of how symbionts may determine trophic interactions between hosts and predators or it is widespread in benthic organisms remains an open question that requires further investigation.  © 2003 The Linnean Society of London . Biological Journal of the Linnean Society , 2003, 78 , 429–438.     

SELECTION OF ASSESSORS BASED ON THEIR SKILL IN IDENTIFYING BASIC TASTES IN LOW CONCENTRATION SOLUTIONS

A method for the first step in the selection of trained sensory assessors, based on their skill in identifying basic tastes in low concentration solutions, was defined and evaluated. The solutions used were: 0.4 and 0.8% sucrose; 0.03, 0.04 and 0.06% citric acid; 0.08 and 0.15% sodium chloride; 0.02 and 0.03% caffeine. Concentration ranges were found adequate. The criterion for selection was to have over 65% correct answers. Out of 226 candidates who received the test, 141 (62%) were selected. The probability of a candidate having more than a certain percentage of correct answers was calculated. The influence of the dilution water quality on the perception of basic tastes was significant; distilled water was the most adequate.     

Light limitations to algal growth in tropical ecosystems

1. Spatial and temporal variations in algal concentrations are controlled in many aquatic ecosystems by the availability of solar irradiance, rather that nutrients or grazing. In such light limiting conditions, changes in the optical or hydrological characteristics of the water column will directly impact biomass concentrations. Here we develop and test an approach based on the relationship between available solar irradiance within the mixed layer and algal biomass concentrations. 2. As with most nutrient/biomass relationships, an increase in available solar energy favours an increase in biomass when light limitation prevails. The ratio between light/biomass is then used to determine a critical light requirement that can be used to estimate critical depth and compensation irradiance and open the way to exploring how changes in mixing depth and vertical attenuation may influence algal biomass concentrations. 3. This approach is used to describe real conditions in two disparate algal communities; the phytoplankton community in Lake Victoria, East Africa and the microphytobenthos community in the lacustrine system of Esteros del Iberá (South America). 4. Differences in the critical light requirement were used to examine the relative efficiency of the algal communities in their use of available solar energy. The tropical phytoplankton community showed similar energetic requirements to theoretical estimates and were found to be less efficient when compared with the phytobenthos community.     

Mitochondrial DNA diversity and taxa delineation in the land snails of the Iberus gualtieranus (Pulmonata,Helicidae) complex

Iberus gualtieranus is a species complex of land snails that is endemic to the Iberian Peninsula. The species taxonomy of the group is based merely on the basis of shell morphology, but validity of the existing taxonomy is uncertain. Using mitochondrial DNA (mtDNA) data (cytochrome oxidase I and 16S rRNA sequences) we were able to validate the observed phylogenetic taxa within the I. gualtieranus s.l. complex by means of the analysis of specimens of the different morphospecies, together with the study of topotypes. Strong incongruences were obtained between morphology and molecular data. The Iberus alonensis morphospecies comprised several genetically divergent but morphologically cryptic lineages. Considering (1) the allopatric distribution of the operational taxonomic units (OTUs), (2) the morphological differentiation, (3) the possible occurrence of hybridization among the different lineages, and (4) the strong differentiation of the mtDNA phylogroups, we suggest the main lineages obtained, for the time being, may be treated as evolutionary species. The robust phylogenetic reconstruction obtained allows us to consider I. alonensis s.s., Iberus campesinus, Iberus carthaginiensis, and Iberus gualtieranus s.s. as valid species. Two additional unnominated taxa of the alonensis shell type have also been identified. Further subdivisions are also considered, including Iberus gualtieranus mariae and Iberus gualtieranus ornatissimus. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154 , 722–737.     

A NEW SPECIES OF BERTHELLA BLAINVILLE, 1824 (OPISTHOBRANCHIA: NOTASPIDEA) FROM THE CANARY ISLANDS (EASTERN ATLANTIC OCEAN), WITH A RE-EXAMINATION OF THE PHYLOGENETIC RELATIONSHIPS OF THE NOTASPIDEA

Berthella canariensis is described from Canary Islands. Themantle is smooth and its ground colour is grey, with black andopaque white spots scattered regularly all over the dorsal surface.White spots are less abundant than black ones. The posterior halfof the mantle has areas of with a paler ground colour that are variablein size. Berthella canariensis has several features that distinguishit from other described members of Berthella. It had a broadradula with numerous teeth per half-row. However, other aspectsof its anatomy, such as the absence of a medial buccal glandand the presence of a tuberculate gill, distinguish it fromother species with a broad radula. As the present species has two features found in some speciesof Pleurobranchus and several new higher taxa have been describedrecently, Willan's (1987) phylogenetic hypothesis was re-analysed.This analysis largely supports the hypothesis presented by Willan. The sister-group relationship of B. Canariensis with B. californiais supported by two synapomorphies. The relationship of thesetwo species to other species of Berthella is poorly resolvedin the present analysis and requires additional study of allmembers of the genus. Similarly, questions of the monophylyof Bathyberthella, Polictenidia, Parabathyberthella, Tomthompsoniaand Berthella require the consideration of additional speciesand comparison with other member of Berthella and Berthellina. Despite the need for further study, the mohophyly of the cladecontaining Bathyberthella, Polictenidia, Parabathyberthellais well supported. Similarly, numerous synapomorphic featuresconfirm the monophyly of the clade containing Bathyberthella,Polictenidia, Parabathyberthella, Tomthompsonia, Berthellinaand Berthella, and its sister-group relationship with the Pleurobranchus. The present study reveals that the Notaspidea have three distinctconfigurations of triaulic reproductive systems, not previouslydifferentiated. (Received 19 January 1998; accepted 15 November 1999)     

Habitat effects on resource tracking ability: do wintering Blackcaps Sylvia atricapilla track fruit availability?

If resource availability shapes population distribution, changes in resource abundance should cause parallel changes in population numbers. However, tracking ability may be disrupted by different environmental and behavioural factors that act at different spatial and temporal scales. Here we analyse the ability of wintering Blackcap Sylvia atricapilla populations to track spatio-temporal variation in fruit availability in southern Spain in two habitats (forests and shrublands) with different population structure. Former studies had shown that forests are equally used by both adult migrant and local Blackcaps, whereas shrublands are nearly monopolized by juvenile migrants. These differences might affect resource tracking: it should be disrupted in forests, as local birds remain over winter in their breeding territories, but not in shrublands where similarly competitive juvenile migrants can freely track the spatial distribution of fruits. We analysed the fruit-tracking ability of Blackcap populations among sites and years in both habitat types using a habitat-matching model, which predicts spatio-temporal changes in population abundance proportional to changes in resource availability. We counted Blackcaps and fruiting shrubs (dominated by Lentiscs Pistacia lentiscus and Wild Olives Olea europaea sylvestris ) during four winters in forest and shrubland patches. The abundance of fruits was always higher in shrublands than in forests. In shrublands, Blackcaps seemed to move freely across fruit-rich habitat patches, tracking changes in fruiting-shrub abundance among sites and years. However, such tracking was not observed in forests. This supports the view that fruit-tracking ability may be constrained by local factors, such as the social structure of populations occurring in different habitat types, which introduces spatio-temporal variation in the way fruit availability shapes the abundance distribution of these birds in their Mediterranean wintering grounds.     

Effects of habitat heterogeneity and local adaptation on the body condition of a forest passerine at the edge of its distributional range

We studied fluctuating asymmetry and feather growth rates as indicators of fitness of blackcaps ( Sylvia atricapilla ) breeding at the border of their distribution range in the Iberian Peninsula. Iberian blackcaps increase their abundance with increasing rainfall and ground cover of brambles. In border habitats, they are sedentary and morphologically different from migrants, suggesting that they could be adapted to peripheral conditions. We tested whether juvenile body condition depends on (1) distance from the centre of the range, (2) mean precipitation or (3) bramble cover. Controlling for environmental variation, we tested for differences between migratory and sedentary populations. Body condition varied across the Iberian gradient in parallel with changes in precipitation. Controlling for this effect, sedentary populations were in better body condition than migratory populations. Our results support the idea that environmental heterogeneity causes fitness to fluctuate across species' ranges, and also that local adaptation may mean that peripheral populations are more than a 'tail end' of the species.  © 2003 The Linnean Society of London . Biological Journal of the Linnean Society , 2003, 78 , 479–488.     

Calcium Regulates the Regeneration of Cilia in Tetrahymena thermophila

A study of calcium metabolism in Tetrahymena during the regeneration of cilia evidenced that the process is inhibited by nifedipine and trifluoperazine. This suggests that calcium ions play an important regulatory role in this process. This was confirmed by studies on calcium uptake and efflux which showed that there was a net increase in calcium uptake prior to the reinitiation of motility. The increase coincided with a period of sensitivity to the calcium antagonist TMB-8 and with an increase in the intracellular level of cGMP. The process was also inhibited by neomycin and stimulated by phorbol esters, which suggests that hydrolysis of phosphatidylinositol phosphates may take place as part of the calcium regulatory network during the regeneration of cilia.     

Polymorphism of intron-1 in the voltage-gated sodium channel gene of Anopheles gambiae s.s. populations from Cameroon with emphasis on insecticide knockdown resistance mutations

Sequence variation at the intron-1 of the voltage-gated sodium channel gene in Anopheles gambiae M- and S-forms from Cameroon was assessed to explore the number of mutational events originating knockdown resistance ( kdr ) alleles. Mosquitoes were sampled between December 2005 and June 2006 from three geographical areas: (i) Magba in the western region; (ii) Loum, Tiko, Douala, Kribi, and Campo along the Atlantic coast; and (iii) Bertoua, in the eastern continental plateau. Both 1014S and 1014F kdr alleles were found in the S-form with overall frequencies of 14% and 42% respectively. Only the 1014F allele was found in the M-form at lower frequency (11%). Analysis of a 455 bp region of intron-1 upstream the kdr locus revealed four independent mutation events originating kdr alleles, here named MS1 -1014F, S1-1014S and S2-1014S kdr- intron-1 haplotypes in S-form and MS3-1014F kdr- intron-1 haplotype in the M-form. Furthermore, there was evidence for mutual introgression of kdr 1014F allele between the two molecular forms, MS1 and MS3 being widely shared by them. Although no M/S hybrid was observed in analysed samples, this wide distribution of haplotypes MS1 and MS3 suggests inter-form hybridizing at significant level and emphasizes the rapid diffusion of the kdr alleles in Africa. The mosaic of genetic events found in Cameroon is representative of the situation in the West–Central African region and highlights the importance of evaluating the spatial and temporal evolution of kdr alleles for a better management of insecticide resistance.