PHENOTYPIC PLASTICITY INDUCED IN TRANSPLANT EXPERIMENTS IN A MUTUALISTIC ASSOCIATION BETWEEN THE RED ALGA JANIA ADHAERENS (RHODOPHYTA,CORALLINALES) AND THE SPONGE HALICLONA CAERULEA (PORIFERA: HAPLOSCLERIDA): MORPHOLOGICAL RESPONSES OF THE ALGA1

The association between the red macroalga Jania adhaerens J. V. Lamour. and the sponge Haliclona caerulea is the most successful life‐form between 2 and 4 m depth in Mazatlán Bay (Mexican Pacific). J. adhaerens colonizes the rocky intertidal area and penetrates into deeper areas only when it lives in association with H. caerulea. The aposymbiotic form of the sponge has not been reported in the bay. To understand the ecological success of this association, we examined the capacity of J. adhaerens to acclimate in Mazatlán Bay using transplant experiments. The transplanted aposymbiotic J. adhaerens did not survive the first 2 weeks; however, J. adhaerens when living in association with H. caerulea, acclimated easily to depth, showing no sign of mortality during the 103 d of the experiment. We conclude that the ability of J. adhaerens to colonize in deeper areas in this hydrodynamic environment may in part rely on the protection provided by the sponge to the algal canopy. Both species contribute to the shape of the associated form. Nevertheless, the morphological variation in the association appears to be dominated by the variation in J. adhaerens canopy to regulate pigment self‐shading under light‐limited conditions and/or tissue resistance under high hydrodynamics. Consequently, our results are consistent with light as the abiotic controlling factor, which regulates the lower depth distribution of the association in Mazatlán Bay, through limiting the growth rate of J. adhaerens. Hydrodynamics may determine the upper limit of the association by imposing high mass losses.     

Ichtyotoxic activity of extracts from Mexican marine macroalgae

Seventy-three species of macroalgae from the Mexican Pacific, Atlantic and Caribbean coast were screened for ichtyotoxic activity. Ethanolic, acetonic and aqueous extracts were prepared and tested against the fish Carassius auratus. The extracts were classified on the basis of their effects as: toxic if the fish died in two hours or less; moderately toxic, if the organism behaved abnormally but death did notoccur, and non-toxic if the fish did not display any change. 79% species were ichtyotoxic to some degree. Extracts of 39 species were toxic, with at least one extract with lethal effects, 19 were moderately toxic and 15 species were non-toxic. Only the extracts ofDictyota bartayresiana, Dictyota cervicornis,Lobophora variegata, Bryothamnion triquetrum and Laurencia obtusa were toxic in all three solvents. The acetone and ethanol extracts were more active, and therefore are more suitable for extraction of toxic substances. This revised version was published online in August 2006 with corrections to the Cover Date.     

Conservation of highly repetitive DNA in cetaceans

It is controversial whether odontocetes (toothed whales) and mysticetes (whalebone whales) have a common ancestry. Cetacean karyological uniformity, which is unique among mammalian orders, suggests a monophyletic origin; however, several anatomical authorities have maintained that odontocetes and mysticetes are diphyletic. We investigated the issue using Southern blot hybridization. Two labelled restriction fragment probes from the DNA of the sei whale (a mysticete) were hybridized to restricted DNA of cetacean species representing all extant families except the Eschrichtiidae, the gray whales. The probes hybridized to specific restriction fragments in all odontocete and mysticete materials. Hybridizations showed preservation of hybridization homologies and a striking conservation of the length of highly repeated DNA sequences. The results are compatible with a common ancestry of odontocetes and mysticetes.     

The fluctuations in the level of endogenous growth regulators in seeds ofAcer pseudoplatanus L. in the course of stratification

In the course of cold stratification ofAcer pseudoplatanus L. fruits a statistically significant alternation occurs in their seeds of a rise and fall in the level of endogenous growth regulators. In the initial weeks the inhibitory effect slightly declines, or, on the contrary, the stimulatory effect slightly increases; in the middle phase of stratification a marked increase in inhibitions and reduction of stimulations appears, and towards the end of stratification the stimulatory effect of isolated substances in the individual biotests rises again, or their inhibition effect is decreased. No direct dependence was found between the decrease of the degree of dormancy and the drop of inhibitor, or increase of promotor levels. However, a certain analogy was observed between the time course of fluctuations in the level of growth regulators and the germination energy of the seeds investigated. An enhancement of the growth activity of the substances isolated (e.g. those of a gibberellin-like nature) in the last weeks of stratification can already be considered as the result of the release of fruits from dormancy.     

Conservation and chromosomal localization of DNA satellites in balenopterid whales

DNA satellites were isolated from three balenopterid species, viz. the minke, sei, and fin whales. In each of them at least two DNA satellites were recognizable with buoyant densities in neutral CsCl of =1.702/1.703 and =1.710/1.711, respectively. cRNAs from each satellite group were used for filter and in situ hybridisations. Homo- and heterologous DNA-cRNA hybrids within each satellite group yielded virtually identical melting curve profiles showing conservation of at least a considerable part of the DNA satellite sequences. There was no evident sequence homology between the =1.702/1.703 and the =1.710/1.711 satellites by filter hybridisation. — The in situ hybridisation showed that in each species the =1.702/1.703 satellite was located in centromeric-paracentromeric C-bands in a few pairs, whereas the =1.710/1.711 satellite was located in terminal C-bands throughout the karyotypes. — The data on the whale DNA satellites indicate that the quantitative evolution of the satellite DNA sequences preceded species divergence of the balenopterids and that the satellite sequences have remained relatively unaltered since the divergence took place. The function of satellite DNA is considered to imply the introduction of both chromosomal and genic polymorphisms and thus being of great importance in speciation. Based upon these concepts a model is postulated for the function of satellite DNA. According to this model at meiotic pairing euchromatin-heterochromatin overlapping between homologous chromosomes is considered to be of a general occurrence. This overlapping is presumed to be accentuated by the size heteromorphism frequently observed between homologous heterochromatic segments (C-bands). In the region of such euchromatin-heterochromatin overlapping, crossing-over would be excluded. The overlapping is suggested to be rectified progressively in the chromosome arms, leaving unaffected crossing-over distant to the euchromatin-heterochromatin junctions. The consequence of this will be that genes in the proximity of the junctions are collectively inherited and selected, whereas genes distant to the heterochromatin will be independently assorted and selected.     

Seasonal composition and temporal succession of necrophagous and predator beetles on pig carrion in central Argentina

Insects are the most important components of the terrestrial fauna associated with carrion because they recycle organic matter back into the ecosystem. They can be classified into four ecological categories comprising: necrophages; parasites and predators of necrophagous species; omnivores, and incidentals. To determine the composition and temporal succession of necrophagous and predator beetles on pig carrion, four experiments, one in each season, were carried out during 2004 in a rural area of Cordoba, central Argentina. Two pigs (Sus scrofa L.), weighing approximately 8 kg each, were used in each of the four experiments. The animals were killed by a sharp blow to the head and immediately placed in an appropriate trap. One pig was placed in the shade and the other in direct sunlight. Beetle fauna were collected daily during the first 4 weeks and thereafter every 2 or 3 days. Five stages of decomposition were observed and a total of 1586 adults and 4309 immatures of Coleoptera belonging to the Staphylinidae, Nitidulidae, Cleridae, Dermestidae, Histeridae, Anthicidae and Trogidae families were collected during the four experiments. The necrophagous community was represented by Dermestes maculates (De Geer), nitidulid species and members of the Trox genus. Staphylinidae, Cleridae and Histeridae species were considered to be the main predators of the necrophagous species.     

Cluster root formation and function vary in two species with contrasting geographic ranges

Plant and Soil - Southern South American Proteaceae can occupy soils that are rich in total phosphorus (P) but poor in available P (for example volcanic soils) thanks to their cluster roots (CR),...     

Immunogenicity of nuclear-encoded LTB:ST fusion protein from Escherichia coli expressed in tobacco plants

Enterotoxigenic Escherichia coli (ETEC) is one of the main causative agents of diarrhea in infants and for travelers. Inclusion of a heat-stable (ST) toxin into vaccine formulations is mandatory as most ETEC strains can produce both heat-labile (LT) and ST enterotoxins. In this study, a genetic fusion gene encoding for an LTB:ST protein has been constructed and transferred into tobacco via Agrobacterium tumefaciens-mediated transformation. Transgenic tobacco plants carrying the LTB:ST gene are then subjected to GM1-ELISA revealing that the LTB:ST has assembled into pentamers and displays antigenic determinants from both LTB and ST. Protein accumulation of up to 0.05% total soluble protein is detected. Subsequently, mucosal and systemic humoral responses are elicited in mice orally dosed with transgenic tobacco leaves. This has suggested that the plant-derived LTB:ST is immunogenic via the oral route. These findings are critical for the development of a plant-based vaccine capable of eliciting broader protection against ETEC and targeting both LTB and ST. Features of this platform in comparison to transplastomic approaches are discussed.     

Elevational trends in butterfly phenology: implications for species responses to climate change

1. Impacts of global change on the distribution, abundance, and phenology of species have been widely documented. In particular, recent climate change has led to widespread changes in animal and plant seasonality, leading to debate about its potential to cause phenological mismatches among interacting taxa. 2. In mountainous regions, populations of many species show pronounced phenological gradients over short geographic distances, presenting the opportunity to test for effects of climate on phenology, independent of variation in confounding factors such as photoperiod. 3. Here we show for 32 butterfly species sampled for five years over a 1700 m gradient (560–2260 m) in a Mediterranean mountain range that, on average, annual flight period is delayed with elevation by 15–22 days per kilometre. Species mainly occurring at low elevations in the region, and to some extent those flying earlier in the year, showed phenological delays of 23–36 days per kilometre, whereas the flight periods of species that occupy high elevations, or fly in late summer, were consistently more synchronised over the elevation gradient. 4. Elevational patterns in phenology appear to reflect a narrowing phenological window of opportunity for larval and adult butterfly activity of high elevation and late‐flying species. 5. Here, we speculate as to the causes of these patterns, and the consequences for our ability to predict species responses to climate change. Our results raise questions about the use of space–time substitutions in predicting phenological responses to climate change, since traits relating to flight period and environmental associations may influence the capacity of species to adapt to changing climates.