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Selected AbstractsLipid biomarker and carbon isotopic signatures for stromatolite-forming, microbial mat communities and Phormidium cultures from Yellowstone National ParkGEOBIOLOGY, Issue 1 2004Linda L. Jahnke ABSTRACT The molecular and isotopic compositions of lipid biomarkers from cultured filamentous cyanobacteria (Phormidium, also known as Leptolyngbya) have been used to investigate the community and trophic structure of photosynthetic mats from alkaline hot springs of the Lower Geyser Basin at Yellowstone National Park. We studied a shallow-water coniform mat from Octopus Spring (OS) and a submerged, tufted mat from Fountain Paint Pots (FPP) and found that 2-methylhopanepolyols and mid-chain branched methylalkanes were diagnostic for cyanobacteria, whereas abundant wax esters were representative of the green non-sulphur bacterial population. The biomarker composition of cultured Phormidium -isolates varied, but was generally representative of the bulk mat composition. The carbon isotopic fractionation for biomass relative to dissolved inorganic carbon (DIC; ,CO2) for cultures grown with 1% CO2 ranged from 21.4 to 26.1 and was attenuated by diffusion limitation associated with filament aggregation (i.e. cell clumping). Isotopic differences between biomass and lipid biomarkers, and between lipid classes, depended on the cyanobacterial strain, but was positively correlated with overall fractionation. Acetogenic lipids (alkanes and fatty acids) were generally more depleted than isoprenoids (phytol and hopanoids). The ,13CTOC for OS and FPP mats were somewhat heavier than for cultures (,16.9 and ,23.6, respectively), which presumably reflects the lower availability of DIC in the natural environment. The isotopic dispersions among cyanobacterial biomarkers, biomass and DIC reflected those established for culture experiments. The 7-methyl- and 7,11-dimethylheptadecanes were from 9 to 11 depleted relative to the bulk organic carbon, whereas 2-methylhopanols derived from the oxidation-reduction of bacteriohopanepolyol were enriched relative to branched alkanes by approximately 5,7. These isotopic relationships survived with depth and indicated that the relatively heavy isotopic composition of the OS mat resulted from diffusion limitation. This study supports the suggestion that culture studies can establish valid isotopic relationships for interpretation of trophic structure in modern and ancient microbial ecosystems. [source] Space use of the spotted sand lizard (Pedioplanis l. lineoocellata) under different degradation statesAFRICAN JOURNAL OF ECOLOGY, Issue 1 2010Bernd Wasiolka Abstract Although the effects of grazing-induced savannah degradation on animal diversity are well documented, knowledge of how they affect space use or responding behaviour remains poor. In this study, we analysed space use of the spotted sand lizard (Pedioplanis l. lineoocellata) in degraded versus nondegraded habitats of southern Kalahari savannah habitats. Lizards were radio tracked, daily movement distances recorded and home range sizes calculated. In degraded Kalahari savannah habitats where plant diversity and perennial grass cover are low but shrub cover high, P. lineoocellata moves larger distances (40.88 ± 6.42 m versus 27.43 ± 5.08 m) and occupies larger home ranges (646.64 ± 244.84 m2 versus 209.15 ± 109.84 m2) than in nondegraded habitats (high plant diversity, high perennial grass cover and low shrub cover). We assume that this increase in daily movement distances and home range sizes is a behavioural plasticity to limited food resources in degraded savannah habitats. Although P. lineoocellata is able to adjust to resource-poor savannah habitats, the increase in the lizard's movement activities is likely to result in a higher predation risk. This is supported by the lower availability of protective vegetation i.e. perennial grass cover. Hence, we conclude that despite behavioural plasticity of P. lineoocellata, overgrazing has a severe negative impact on the space use of P. lineoocellata. Résumé Bien que les effets de la dégradation de la savane due au pâturage sur la diversité animale soient bien documentés, on sait toujours peu de choses sur la façon dont ils affectent l'utilisation de l'espace ou les comportements de réponse. Dans cette étude, nous avons analysé l'utilisation de l'espace du lézard des sables tachetéPedioplanis l. lineoocellata, dans des habitats de savane dégradés ou non du sud du Kalahari. Des lézards furent suivis par radio, les distances parcourues par jour furent enregistrées, et l'on a calculé la taille des domaines vitaux. Dans les habitats de savane dégradés du Kalahari, où la diversité végétale et la couverture herbacée pérenne sont faibles mais la couverture arbustive élevée, Pedioplanis lineoocellata couvre de plus grandes distances (40.88 ± 6.42 m versus 27.43 ± 5.08 m) et occupe de plus vastes domaines vitaux (646.64 ± 244.84 m² versus 209.15 ± 109.84 m²) que dans les habitats non dégradés (grande diversité végétale, forte couverture herbacée pérenne et faible couverture arbustive). Nous supposons que cette augmentation de la distance parcourue chaque jour et de la taille des domaines vitaux est le résultat d'une plasticité comportementale face à des ressources alimentaires limitées dans les habitats dégradés de savane. Bien que P. lineoocellata soit capable de s'adapter à des habitats de savane pauvres en ressources, l'augmentation des déplacements du lézard est susceptible d'entraîner un plus grand risque de prédation. Cette hypothèse est confortée par la faible disponibilité de végétation protectrice, c.-à-d. d'une couverture herbacée pérenne. Dès lors, nous concluons que, malgré la plasticité comportementale de P. lineoocellata, le surpâturage a un effet négatif sévère sur son utilisation de l'espace. [source] Differences in diet and activity pattern between two groups of Alouatta palliata associated with the availability of big trees and fruit of top food taxaAMERICAN JOURNAL OF PRIMATOLOGY, Issue 8 2009Jacob C. Dunn Abstract The threat that forest fragmentation and habitat loss presents for several Alouatta taxa requires us to determine the key elements that may promote the persistence of howler monkeys in forest fragments and to evaluate how changes in the availability of these elements may affect their future conservation prospects. In this study we analyzed the relationship between the availability of both big trees of top food taxa (BTTFT) (diameter at breast height>60) and fruit of top food taxa (FrTFT) in the home ranges of two groups of Alouatta palliata mexicana occupying different forest fragments in Los Tuxtlas, Mexico, and their diet and activity pattern. Both study groups preferred big trees for feeding and the group with lower availability of BTTFT in their home range fed from more, smaller food sources. Furthermore, both study groups also increased the number of food sources when their consumption of fruit decreased, and the group with lower availability of FrTFT in their home range fed from more food sources. The increase in the number of food sources used under such conditions, in turn, set up a process of higher foraging effort and lower rest. In summary, our results support other studies that suggest that the availability of big trees and fruit may be two important elements influencing the persistence of howler monkeys in forest fragments. Am. J. Primatol. 71:654,662, 2009. © 2009 Wiley-Liss, Inc. [source] The problem of meeting dietary protein requirements in intensive aquaculture of marine fish larvae, with emphasis on Atlantic halibut (Hippoglossus hippoglossus L.)AQUACULTURE NUTRITION, Issue 3 2007A. KVÅLE Abstract Atlantic halibut (Hippoglossus hippoglossus) achieve a mature gastrointestinal tract approximately 2 months after first feeding (12 °C). The immature digestion may be the reason that compound diets fail to sustain growth and survival in first feeding halibut larvae and in larvae of other marine fish species. On the other hand, larvae fed with live feeds are capable of extraction of sufficient quantities of nutrients to sustain high growth rates. A lower availability of the protein in formulated diets compared with live prey is considered to be an important reason for the low performance of formulated diets. One approach to increase dietary protein availability is supplementation of pre-digested proteins. Experiments using tube fed individual larvae show that halibut larvae are able to utilize hydrolysed protein more efficiently than intact protein. However, Atlantic halibut in culture did not respond well to dietary supplementation of hydrolysed protein, in contrast to some other species. One reason may be extensive leaching of pre-hydrolysed proteins from the microparticulate feed. Atlantic halibut are slow feeders and may thus suffer more from nutrient leaching than species eating more rapidly. Feed formulation techniques affect dietary protein leaching, and in this paper, different techniques and their impact on feed properties are described. Microbound diets are most widely used in larval rearing, but show high rates of nutrient leaching. Lipid-based capsules seem to have the best potential to prevent leaching, however, they are not able to deliver a complete diet. The high need for improvements in larval feed formulation techniques are clearly stated, and some suggestions are given. Among these are production of complex particles, where small lipid-based capsules or liposomes containing the low molecular weight water-soluble nutrients are embedded. In such feed particles the water-soluble molecules are protected from leaching. Techniques for delivery of water-soluble nutrients that are needed in large quantities, i.e. free amino acids or hydrolysed and water-soluble protein, remain to be developed. [source] | |||||||||||||