Not all jellyfish are equal: isotopic evidence for inter- and intraspecific variation in jellyfish trophic ecology

Jellyfish are highly topical within studies of pelagic food-webs and there is a growing realisation that their role is more complex than once thought. Efforts being made to include jellyfish within fisheries and ecosystem models are an important step forward, but our present understanding of their underlying trophic ecology can lead to their oversimplification in these models. Gelatinous zooplankton represent a polyphyletic assemblage spanning >2,000 species that inhabit coastal seas to the deep-ocean and employ a wide variety of foraging strategies. Despite this diversity, many contemporary modelling approaches include jellyfish as a single functional group feeding at one or two trophic levels at most. Recent reviews have drawn attention to this issue and highlighted the need for improved communication between biologists and theoreticians if this problem is to be overcome. We used stable isotopes to investigate the trophic ecology of three co-occurring scyphozoan jellyfish species (Aurelia aurita, Cyanea lamarckii and C. capillata) within a temperate, coastal food-web in the NE Atlantic. Using information on individual size, time of year and ;delta C-13 and delta N-15 stable isotope values, we examined: (1) whether all jellyfish could be considered as a single functional group, or showed distinct inter-specific differences in trophic ecology; (2) Were size-based shifts in trophic position, found previously in A. aurita, a common trait across species?; (3) When considered collectively, did the trophic position of three sympatric species remain constant over time? Differences in delta N-15 (trophic position) were evident between all three species, with size-based and temporal shifts in delta N-15 apparent in A. aurita and C. capillata. The isotopic niche width for all species combined increased throughout the season, reflecting temporal shifts in trophic position and seasonal succession in these gelatinous species. Taken together, these findings support previous assertions that jellyfish require more robust inclusion in marine fisheries or ecosystem models.

Intraspecific variation in nitrogen source utilisation by isolates of the ericoid mycorrhizal fungus Hymenoscyphus Ericae (Read) Korf and Kernan

Variation in the abilities of 35 isolates of the ericoid mycorrhizal fungal endophyte Hymenoscyphus ericae from two field sites to utilise inorganic and organic nitrogen sources in axenic culture has been investigated. While most isolates showed a preference for NH₄/^- as a sole nitrogen source, considerable variation was observed in the abilities of isolates to utilise amino acids and protein (BSA). In particular, large intraspecific variation was observed for glutamine and BSA utilisation, with some isolates thriving on these substrates while others produced little growth. The data suggest that individual isolates of H. ericae may vary considerably in their abilities to supply their host plants with nitrogen from different substrates in soil. (C) 2000 Elsevier Science Ltd.

Carbon availability affects nitrogen source utilisation by Hymenoscyphus ericae

We compared the ability of five strains of the ericoid mycorrhizal fungus Hymenoscyphus ericae to utilise glutamine, ammonium or nitrate at high or low carbon (C) availability. The pattern of intraspecific variation in growth was affected by C availability. When C supply was high, growth differences between strains were explained by the total amount of nitrogen (N) taken up, suggesting variation in uptake kinetics. Under C-limiting conditions, strain differences were linked with their nitrogen use efficiency, implying intraspecific differences in N metabolism. The relationship between growth on glutamine and pH shifts in the media indicated that there was intraspecific variation in glutamine transporters. In addition, the correlation between pH changes and the amount of glutamine-N recovered as ammonium in the media indicated that there were intraspecific variations within the enzymatic pathways involved in glutamine metabolism. Our findings, compared with those of a previous study involving the same ericoid strains, draw attention to the temporal variation in nitrogen source utilisation by ericoid mycorrhizal fungi when maintained in axenic culture.

The spatial ecology of the whiskered bat (Myotis mystacinus) at the western extreme of its range provides evidence of regional adaptation

Although widespread, the ecology of the whiskered bat, Myotis mystacinus in Europe remains poorly understood. Ireland is positioned at the most western extreme of this species' range. To ascertain the ecology of M. mystacinus at its geographic range extreme, the roosting behaviour, home range and habitat use of females in a maternity roost in Ireland was investigated by radio-tracking. M. mystacinus were active in a diversity of habitats: namely, mixed woodland, riparian vegetation, arable land and rough grassland. However, only mixed woodland and riparian habitats were selected as core foraging areas. This is in contrast to a previous study from Britain where only pasture was utilised but is in agreement with data from Slovakia, where woodland was also selected, whilst riparian areas were also utilised by this species in Germany. A high degree of overlap in the foraging areas of individuals was observed. A total of seven roosts were utilised by tracked bats and roost switching behaviour was observed. We discuss our contrasting results in respect to range limitations, regional variability in landscape structure and the composition of bat communities. The present results have implications for the conservation of M. mystacinus within Ireland and other parts of its range, highlighting the need for range wide ecological studies. Regional variability in the ecology of bats related to landscape factors is an important consideration for bat conservation and therefore must be incorporated into future management plans. (C) 2012 Deutsche Gesellschaft fur Saugetierkunde. Published by Elsevier GmbH. All rights reserved.

Relative Effects of Gamete Compatibility and Hydrodynamics on Fertilization in the Green Sea Urchin Strongylocentrotus droebachiensis

Intraspecific variation in gamete compatibility among male/female pairs causes variation in the concentration of sperm required to achieve equivalent fertilization levels. Gamete compatibility is therefore potentially an important factor controlling mating success. Many broadcast-spawning marine invertebrates, however, also live in a dynamic environment where hydrodynamic conditions can affect the concentration of sperm reaching eggs during spawning. Thus flow conditions may moderate the effects of gamete compatibility on fertilization. Using the green sea urchin Strongylocentrotus droebachiensis as a model system, we assessed the relative effects of gamete compatibility (the concentration of sperm required to fertilize 50% of the eggs in specific male/female pairs; F50) and the root-mean-square of total velocity (urms; 0.01-0.11 m s(-1)) on fertilization in four locations near a spawning female (water column, wake eddy, substratum, and aboral surface) in both unidirectional and oscillatory flows. Percent fertilization decreased significantly with increasing urms at all locations and both flow regimes. However, although gamete compatibility varied by almost 1.5 orders of magnitude, it was not a significant predictor of fertilization for most combinations of position and flow. The notable exception was a significant effect of gamete compatibility on fertilization on the aboral surface under unidirectional flow. Our results suggest that selection on variation in gamete compatibility may be strongest in eggs fertilized on the aboral surface of sea urchins and that hydrodynamic conditions may add environmental noise to selection outcomes.

Do ectomycorrhizal fungi exhibit adaptive tolerance to potentially toxic metals in the environment?

The effects of potentially toxic metals on ectomycorrhizal (ECM) fungi and their higher plant hosts are examined in this review. Investigations at a species and community level have revealed wide inter- and intraspecific variation in sensitivity to metals. Adaptive and constitutive mechanisms of ECM tolerance are proposed and discussed in relation to proven tolerance mechanisms in bacteria, yeasts and plants. Problems with methodology and research priorities are highlighted. These include the need for a detailed understanding of the genetic basis of tolerance in the ECM symbiosis, and for studies of ECM community dynamics in polluted sites.

Biological influences on inter- and intraspecific isotopic variability among paired chondrostome fishes

This study aimed at examining resource partitioning both at the inter- and intraspecific levels between paired chondrostome fishes: Chondrostoma nasus, the nase, C. toxostoma, the sofie, and their hybrid. The study was performed in the south of France and concerned a main river (the Durance River) and a tributary (the Buech River). In these rivers, C. nasus was an introduced species, originating in central Europe, and C. toxostoma was an endemic congener, in the south of France. Stable isotope analysis was used to analyse trophic and spatial niches. Isotopic differences indicated that individuals from the three taxa (C. nasus, C. toxostoma and their hybrid) have different spatial origins. At the interspecific level, the different chondrostomes originating from the Buech River showed a high level of trophic niche overlap. At the intraspecific level, nase individuals originating from the different spatial origins showed a resource polymorphism; differences in morphology were associated with variation in behaviour and life history traits. Their coexistence was a likely outcome of resource polymorphism. This study provides an example of the importance of considering the link between intra- and interspecific interactions to gain an understanding of the mechanisms driving the coexistence of species-pairs. (C) 2010 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Life history variation in Dasya ocellata (Dasyaceae, Rhodophyta)

Four of the five members of the Dasyaceae found in the British Isles, Dasya corymbifera J. Agardh, Dasya hutchinsiae Harvey, Dasya punicea Meneghini ex Zanardini and Heterosiphonia plumosa (Ellis) Batters, appear to have Polysiphonia-type life histories on the basis of evidence from field collections of tetrasporophytes and gametophytes. In collections from the British Isles of the fifth species, Dasya ocellata (Grateloup) Harvey, only tetrasporophytes have ever been observed, but there are two reports of gametophytes in this species from further south in Europe. Dasya ocellata tetraspores were isolated into culture from populations in Strangford Lough, Northern Ireland, and Agadir, Morocco, where one female thallus was collected amongst tetrasporophytes. Dasya ocellata from Ireland underwent a direct tetraspore-to-tetrasporophyte life history, which was followed through two complete cycles. Karyological studies showed that meiosis does not occur during tetrasporangial development: tetrasporangia are mitotic, with c. 64 small chromosomes. Comparison with chromosome numbers in meiotic tetrasporangia of D. hutchinsiae (n = c. 32) showed that this is the diploid chromosome complement. Tetraspores from the Moroccan isolate, by contrast, gave rise to gametophytes (although only the males became fertile) and tetrasporophyte recycling did not occur. Thalli sampled from a population in southern Portugal consisted only of tetrasporophytes. Dasya ocellata, like many members of the Ceramiales, shows intraspecific life history variability; a sexual life history apparently occurs only in southern populations.

Exploring molecular variation in Schistosoma japonicum in China

Schistosomiasis is a neglected tropical disease that affects more than 200 million people worldwide. The main disease-causing agents, Schistosoma japonicum, S. mansoni and S. haematobium, are blood flukes that have complex life cycles involving a snail intermediate host. In Asia, S. japonicum causes hepatointestinal disease (schistosomiasis japonica) and is challenging to control due to a broad distribution of its snail hosts and range of animal reservoir hosts. In China, extensive efforts have been underway to control this parasite, but genetic variability in S. japonicum populations could represent an obstacle to eliminating schistosomiasis japonica. Although a draft genome sequence is available for S. japonicum, there has been no previous study of molecular variation in this parasite on a genome-wide scale. In this study, we conducted the first deep genomic exploration of seven S. japonicum populations from mainland China, constructed phylogenies using mitochondrial and nuclear genomic data sets, and established considerable variation between some of the populations in genes inferred to be linked to key cellular processes and/or pathogen-host interactions. Based on the findings from this study, we propose that verifying intraspecific conservation in vaccine or drug target candidates is an important first step toward developing effective vaccines and chemotherapies against schistosomiasis.

A genome-wide linkage scan for genes controlling variation in urinary albumin excretion in type ll diabetes

The main hallmark of diabetic nephropathy is elevation in urinary albumin excretion. We performed a genome-wide linkage scan in 63 extended families with multiple members with type II diabetes. Urinary albumin excretion, measured as the albumin-to-creatinine ratio (ACR), was determined in 426 diabetic and 431 nondiabetic relatives who were genotyped for 383 markers. The data were analyzed using variance components linkage analysis. Heritability (h2) of ACR was significant in diabetic (h2=0.23, P=0.0007), and nondiabetic (h2=0.39, P=0.0001) relatives. There was no significant difference in genetic variance of ACR between diabetic and nondiabetic relatives (P=0.16), and the genetic correlation (rG=0.64) for ACR between these two groups was not different from 1 (P=0.12). These results suggested that similar genes contribute to variation in ACR in diabetic and nondiabetic relatives. This hypothesis was supported further by the linkage results.

Psychotic symptoms in Alzheimer's disease are not influenced by polymorphic variation at the dopamine receptor DRD3 gene

It has been suggested that genetic influences unmasked during neurodevelopment to produce schizophrenia may appear throughout neurodegeneration to produce AD plus psychosis. Risk of schizophrenia and psychosis in Alzheimer's disease (AD) has been linked to polymorphic variation at the dopamine receptor DRD3 gene implying similar causative mechanisms. We tested this association in a large cohort of Alzheimer's disease patients with a diagnosis of probable AD of 3 years or more duration from the relatively genetically homogenous Northern Irish population. We assessed relationships between genotypes/alleles of the DRD3 BalI polymorphism and the presence or absence of psychotic symptoms (delusions, hallucinations) in AD patients during the month prior to interview and at any stage during the dementia. No significant associations were found when delusions and hallucinations were cross-tabulated against S and G alleles and SS, SG and GG genotypes. Logistic regression failed to detect any influence of APOE, gender, family history or prior psychiatric history. In conclusion, we were unable to confirm previously reported associations between the DRD3 BalI polymorphism and psychotic symptoms in AD.