The Role of Teleost Grazers in a Relatively Pristine Seagrass Ecosystem

Trophic downgrading of ecosystems necessitates a functional understanding of trophic cascades. Identifying the presence of cascades, and the mechanisms through which they occur, is particularly important for seagrass meadows, which are among the most threatened ecosystems on Earth. Shark Bay, Western Australia provides a model system to investigate the potential importance of top-down effects in a relatively pristine seagrass ecosystem. The role of megagrazers in the Shark Bay system has been previously investigated, but the role of macrograzers (i.e., teleosts), and their importance relative to megagrazers, remains unknown. The objective of my dissertation was to elucidate the importance of teleost macrograzers in transmitting top-down effects in seagrass ecosystems. Seagrasses and macroalgae were the main food of the abundant teleost Pelates octolineatus, but stable isotopic values suggested that algae may contribute a larger portion of assimilated food than suggested by gut contents. Pelates octolineatus is at risk from numerous predators, with pied cormorants (Phalacrocorax varius) taking the majority of tethered P. octolineatus. Using a combination of fish trapping and unbaited underwater video surveillance, I found that the relative abundance of P. octolineatus was greater in interior areas of seagrass banks during the cold season, and that the mean length of P. octolineatus was greater in these areas compared to along edges of banks. Finally, I used seagrass transplants and exclosure experiments to determine the relative effect of megagrazers and macrograzers on the establishment and persistence of three species of seagrasses in interior microhabitats. Teleost grazing had the largest impact on seagrass species with the highest nutrient content, and these impacts were primarily observed during the warm season. My findings are consistent with predictions of a behaviorally-mediated trophic cascade initiated by tiger sharks (Galeocerdo cuvier) and transmitted through herbivorous fishes and their predators.

Bird predation experiments in tropical agroforestry landscapes of the Napu Valley in Central Sulawesi, Indonesia

We performed bird predation experiments (dummy experiments), using artificial prey and bird community data to investigate the importance of predator diversity vs. predator identity in cacao agroforestry landscapes. All sample sites were situated at the northern tip of Napu Valley in Central Sulawesi, Indonesia. After an initial mapping of the study area, we selected 15 smallholder cacao plantations as sites for our exclosure experiments in March 2010. For our predation experiment, we selected 10 (out of 15) study sites and 5 cacao trees per site for the application of artificial prey for birds (dummy caterpillars made of plasticine). Our study trees (numbered from 1 to 5 per site) were randomly chosen and we kept spacing of at least two unmanipulated cacao trees between two study trees to avoid clumped distribution. To quantify both daytime/diurnal predation and night-time/nocturnal predation (e.g. birds vs. bats), we applied 7 caterpillar dummies on all study trees and controlled them for predation marks in the early morning (05:00-06:00 am), in the evening (17:00-18:00 pm) and in the early morning on the next day (completing one survey round). In total, we performed four survey rounds per study site (in June and July 2011). The caterpillar dummies were always applied in the same order and on three different parts of each cacao study tree: One 'control dummy' (located on first branching of the cacao tree); 3 'branch dummies' (located on one main branch coming from first branching; 20-25 cm between single dummies) and 3 'leaf dummies' (3 medium aged cacao trees adjacent to main branch were selected and single dummies placed in the center of each cacao leaf). The different positions were chosen to control for different foraging modes of predators (e.g. branch gleaners versus leaf gleaners). During day- and nighttime surveys, we controlled if the dummy caterpillars were still present in their original position, if they were absent and could not be relocated on the ground or if they were fallen to the ground, but could still be recorded. Eaten dummies were counted as 1 mark usually, except for those dummies, where two or more different kind of arthropods had eaten parts of the dummy (2 marks or more). Other predation marks were added to this number. For each dummy, we counted the total number of different predation marks. We focused on predation marks that could be identified with certainty (based on preliminary observations and/or literature): marks of birds, rodents and snails. Finally, we analysed the relationship of bird predation marks and bird community parameters (abundance vs. diversity), as well as effects of local and landscape management on the avian predation success.

Cacao trees in tropical agroforestry landscapes of the Napu Valley in Central Sulawesi, Indonesia

All sample sites were situated at the northern tip of Napu Valley in Central Sulawesi, Indonesia. After an initial mapping of the study area, we selected 15 smallholder cacao plantations as sites for bird and bat exclosure experiments in March 2010. On each study site, we established 4 treatments for these exclosure experiments (bird exclosure - closed during daytime and open during night; bat exclosure - closed overnight and opened during daytime; full exclosure of both birds and bats - always closed and unmanipulated/open control treatments - always open). In each treatment, there were 2 cacao trees (total of 8 cacao trees per study site), surrounded by nylon filament (2x2 cm mesh size) that was opened and closed according to the activity period of day and night active flying vertebrates (05:00-06:00 am and 17:00-18:00 pm) on a daily basis. The mean tree height and diameter at breast height (dbh) result from two measures of all study trees at the beginning of the exclosure experiment (June 2010) and 6 months later (February 2011).

Avian species identity and predation success in tropical cacao agroforestry of the Napu Valley in Central Sulawesi, Indonesia

Avian ecosystem services such as the suppression of pests are considered being of high ecological and economic importance in a range of ecosystems, especially in tropical agroforestry. But how bird predation success is related to the diversity and composition of the bird community, as well as local and landscape factors, is poorly understood. The author quantified arthropod predation in relation to the identity and diversity of insectivorous birds, using experimental exposure of artificial, caterpillar-like prey on smallholder cacao agroforestry systems, differing in local shade management and distance to primary forest. The bird community was assessed using both mist netting (targeting on active understory insectivores) and point count (higher completeness of species inventories) sampling. The study was conducted in a land use dominated area in Central Sulawesi, Indonesia, adjacent to the Lore Lindu National Park. We selected 15 smallholder cacao plantations as sites for bird and bat exclosure experiments in March 2010. Until July 2011, we recorded several data in this study area, including the bird community data, cacao tree data and bird predation experiments that are presented here. We found that avian predation success can be driven by single and abundant insectivorous species, rather than by overall bird species richness. Forest proximity was important for enhancing the density of this key species, but did also promote bird species richness. The availability of local shade trees had no effects on the local bird community or avian predation success. Our findings are both of economical as well as ecological interest because the conservation of nearby forest remnants will likely benefit human needs and biodiversity conservation alike.

Bird observation and sampling in tropical agroforestry landscapes of the Napu Valley in Central Sulawesi, Indonesia

We investigated the local bird community in Central Sulawesi (Indonesia), with focus on insectivorous species in the agroforestry landscapes adjacent to the Lore Lindu National Park. All study sites were situated at the northern tip of Napu Valley in Central Sulawesi, Indonesia. After an initial mapping of the study area, we selected 15 smallholder cacao plantations as sites for our study in March 2010. These sides were mainly used for bird and bat exclosure experiments. All sited were situated along a local gradient (shade availability on each plantation) and a landscape gradient (distance to primary forest), which were independent from each other. In September 2010 and from February until June 2011, we assessed the bird community on our 15 study sites using monthly point count and mist netting sampling. Point count (20 minutes between 07 am and 10 am and in between the net checking hours) and mist netting surveys (12 hours, between 05:30 am and 17:30 pm) were conducted simultaneously but only once per month on each study site, to avoid habituation of the local bird community to our surveys. Further, point counts were conducted at least 100 m apart from the mist netting sites, to avoid potential disturbance between the two methods. We discarded all observations beyond 50 m (including those individuals that flew over the canopy) from the statistical analysis, as well as recaptures of individuals within identical mist netting rounds.

The role of teleost grazers in a relatively pristine seagrass ecosystem

Trophic downgrading of ecosystems necessitates a functional understanding of trophic cascades. Identifying the presence of cascades, and the mechanisms through which they occur, is particularly important for seagrass meadows, which are among the most threatened ecosystems on Earth. Shark Bay, Western Australia provides a model system to investigate the potential importance of top-down effects in a relatively pristine seagrass ecosystem. The role of megagrazers in the Shark Bay system has been previously investigated, but the role of macrograzers (i.e., teleosts), and their importance relative to megagrazers, remains unknown. The objective of my dissertation was to elucidate the importance of teleost macrograzers in transmitting top-down effects in seagrass ecosystems. Seagrasses and macroalgae were the main food of the abundant teleost Pelates octolineatus, but stable isotopic values suggested that algae may contribute a larger portion of assimilated food than suggested by gut contents. Pelates octolineatus is at risk from numerous predators, with pied cormorants (Phalacrocorax varius) taking the majority of tethered P. octolineatus. Using a combination of fish trapping and unbaited underwater video surveillance, I found that the relative abundance of P. octolineatus was greater in interior areas of seagrass banks during the cold season, and that the mean length of P. octolineatus was greater in these areas compared to along edges of banks. Finally, I used seagrass transplants and exclosure experiments to determine the relative effect of megagrazers and macrograzers on the establishment and persistence of three species of seagrasses in interior microhabitats. Teleost grazing had the largest impact on seagrass species with the highest nutrient content, and these impacts were primarily observed during the warm season. My findings are consistent with predictions of a behaviorally-mediated trophic cascade initiated by tiger sharks (Galeocerdo cuvier) and transmitted through herbivorous fishes and their predators.

Successful transplant of mesenchymal stem cells in induced osteonecrosis of the ovine femoral head: preliminary results

PURPOSE: Evaluate the bone tissue recovery following transplantation of ovine mesenchymal stem cells (MSC) from bone marrow and human immature dental-pulp stem cells (hIDPSC) in ovine model of induced osteonecrosis of femoral head (ONFH). METHODS: Eight sheep were divided in three experimental groups. First group was composed by four animals with ONFH induced by ethanol through central decompression (CD), for control group without any treatment. The second and third group were compose by two animals, six weeks after ONFH induction received transplantation of heterologous ovine MSC (CD + oMSC), and hIDPSC (CD + hIDPSC), respectively. In both experiments the cells were transplanted without application of any type of immunosupression protocol. RESULTS: Our data indicate that both cell types used in experiments were able to proliferate within injured site providing bone tissue recovery. The histological results obtained from CD+hIDPSC suggested that the bone regeneration in such animals was better than that observed in CD animals. CONCLUSION: Mesenchymal stem cell transplant in induced ovine osteonecrosis of femoral head by central decompression technique is safe, and apparently favors bone regeneration of damaged tissues.

Extracorporeal membrane oxygenation support after heart explantation: a proposal on how to deal with hyperacute rejection of heart transplant

Purpose: In extreme situations, such as hyperacute rejection of heart transplant or major bleeding per-operating complications, an urgent heart explantation might be the only means of survival. The aim of this experimental study was to improve the surgical technique and the hemodynamics of an Extracorporeal Membrane Oxygenation (ECMO) support through a peripheral vascular access in an acardia model. Methods: An ECMO support was established in 7 bovine experiments (59±6.1 kg) by the transjugular insertion to the caval axis of a self-expanded cannula, with return through a carotid artery. After baseline measurements of pump flow and arterial and central venous pressure, ventricular fibrillation was induced (B), the great arteries were clamped, the heart was excised and right and left atria remnants, containing the pulmonary veins, were sutured together leaving an atrial septal defect (ASD) over the cannula in the caval axis. Measurements were taken with the pulmonary artery (PA) clamped (C) and anastomosed with the caval axis (D). Regular arterial and central venous blood gases tests were performed. The ANOVA test for repeated measures was used to test the null hypothesis and a Bonferroni t method for assessing the significance in the between groups pairwise comparison of mean pump flow. Results: Initial pump flow (A) was 4.3±0.6 L/min dropping to 2.8±0.7 L/min (P B-A= 0.003) 10 minutes after induction of ventricular fibrillation (B). After cardiectomy, with the pulmonary artery clamped (C) it augmented not significantly to 3.5±0.8 L/min (P C-B= 0.33, P C-A= 0.029). Finally, PA anastomosis to the caval axis was followed by an almost to baseline pump flow augmentation (4.1±0.7 L/min, P D-B= 0.009, P D-C= 0.006, P D-A= 0.597), permitting a full ECMO support in acardia by a peripheral vascular access. Conclusions: ECMO support in acardia is feasible, providing new opportunities in situations where heart must urgently be explanted, as in hyperacute rejection of heart transplant. Adequate drainage of pulmonary circulation is pivotal in order to avoid pulmonary congestion and loss of volume from the normal right to left shunt of bronchial vessels. Furthermore, the PA anastomosis to the caval axis not only improves pump flow but it also permits an ECMO support by a peripheral vascular access and the closure of the chest.

Disposition of oral valganciclovir during continuous renal replacement therapy in two lung transplant recipients

Background: Oral valganciclovir (VGC) is hydrolysed into active ganciclovir (GCV) which is eliminated in the kidney by filtration and secretion. VGC dosage has to be adapted in renal failure with continuous renal replacement therapy (CRRT), a condition sometimes encountered early after solid organ transplantation. This investigation aimed to determine whether VGC 450 mg every 48 hours provides appropriate GCV exposure for cytomegalovirus (CMV) prophylaxis during CRRT. Methods: GCV pharmacokinetics were extensively studied during CRRT in two lung transplant recipients with acute renal failure receiving VGC 450 mg every 48 hours trough a nasogastric tube. In vitro experiments using blank whole blood spiked with GCV further investigated exchanges between plasma and erythrocytes. Results: GCV disposition was characterised by an area under the curve (AUC) of 98.0 and 55.4 mg h/L, resulting in trough concentrations of 0.7 and 0.2 mg/L, an apparent total body clearance of 3.3 and 5.8 L/h, a terminal half-life of 16.9 and 14.1 h, and an apparent volume of distribution of 60.3 and 104.9 L. The observed sieving coefficient (filtrate/plasma) was 1.05 and 0.96, and the hemofiltration clearance 3.3 and 3.1 L/h, respectively. High sieving values could be explained by an efflux of GCV from erythrocytes. In vitro experiments confirmed that erythrocytes are loaded with significant GCV amount and release it quickly into plasma, thus contributing to the apparent efficacy of hemofiltration. Conclusion: These results indicate that a VGC dosage of 450 mg every 48 hours was adequate for CMV prophylaxis during CRRT, providing GCV levels similar to those reported using 900 mg qd in transplant recipients with normal renal function.

Disposition of valganciclovir during continuous renal replacement therapy in two lung transplant recipients.

OBJECTIVES: To determine whether valganciclovir 450 mg every 48 h for cytomegalovirus (CMV) prophylaxis provides appropriate ganciclovir exposure in solid organ transplant recipients during continuous renal replacement therapy (CRRT). PATIENTS AND METHODS: Ganciclovir pharmacokinetics was intensively studied in two lung transplant recipients under valganciclovir 450 mg every 48 h over one dosing interval. In vitro experiments using blank whole blood spiked with ganciclovir further investigated exchanges between plasma and erythrocytes. RESULTS: Ganciclovir disposition was characterized by apparent total body clearance of 3.3 and 5.8 L/h, terminal half-life of 16.9 and 14.1 h, and apparent volume of distribution of 60.3 and 104.9 L in Patients 1 and 2, respectively. The observed sieving coefficient was 1.05 and 0.96, and the haemofiltration clearance was 3.3 and 3.1 L/h. In vitro experiments confirmed rapid efflux of ganciclovir from red blood cells into plasma, increasing the apparent efficacy of haemofiltration. CONCLUSIONS: A valganciclovir dosage of 450 mg every 48 h appears adequate for patients under CRRT requiring prophylaxis for CMV infection, providing concentration levels in the range reported for 900 mg once daily dosing outside renal failure.

CCL8 and the Immune Control of Cytomegalovirus in Organ Transplant Recipients.

Monitoring of cytomegalovirus cell-mediated immunity is a promising tool for the refinement of preventative and therapeutic strategies posttransplantation. Typically, the interferon-γ response to T cell stimulation is measured. We evaluated a broad range of cytokine and chemokines to better characterize the ex vivo host-response to CMV peptide stimulation. In a cohort of CMV viremic organ transplant recipients, chemokine expression-specifically CCL8 (AUC 0.849 95% CI 0.721-0.978; p = 0.003) and CXCL10 (AUC 0.841, 95% CI 0.707-0.974; p = 0.004)-was associated with control of viral replication. In a second cohort of transplant recipients at high-risk for CMV, the presence of a polymorphism in the CCL8 promoter conferred an increased risk of viral replication after discontinuation of antiviral prophylaxis (logrank hazard ratio 3.6; 95% CI 2.077-51.88). Using cell-sorting experiments, we determined that the primary cell type producing CCL8 in response to CMV peptide stimulation was the monocyte fraction. Finally, in vitro experiments using standard immunosuppressive agents demonstrated a dose-dependent reduction in CCL8 production. Chemokines appear to be important elements of the cell-mediated response to CMV infection posttransplant, as here suggested for CCL8, and translation of this knowledge may allow for the tailoring and improvement of preventative strategies.

Étude de l’immunité antivaricelleuse chez l’enfant transplanté au moyen de moelle osseuse ou de sang de cordon ombilical

L’infection primaire au VZV et la réactivation du VZV latent sont fréquemment observées à la suite d’une GMO ou d’une GSCO, ce qui cause de sérieuses complications chez le patient. Pour prévenir ces infections, une prophylaxie antivirale est administrée systématiquement chez tous les greffés de MO ou de SCO, alors qu’il n’existe aucun consensus sur la durée optimale d’une telle prophylaxie. Pour résoudre ce problème, notre objectif est de développer et valider une méthode ELISpot-VZV-IFN- qui permettra de suivre la reconstitution de l’immunité à médiation cellulaire anti-VZV chez les receveurs de GMO ou de GSCO et ainsi déterminer le moment opportun pour réduire ou interrompe la prophylaxie chez les receveurs de greffes de CSH. Dans un premier temps, des valeurs-seuil de la réponse à médiation cellulaire anti-VZV chez la population pédiatrique saine ont dû être générées. À la lumière de nos résultats, un enfant avec un résultat ELISpot-VZV-IFN- > 190.0 SFU/106 PBMC devrait être protégé contre une possible infection à VZV. Pour valider cette étude, une étude prospective de la reconstitution immunitaire anti-VZV a été effectuée chez 9 enfants greffés de MO ou de SCO. Nos résultats préliminaires ont montré qu’il n’y avait eu aucune reconstitution significative de l’immunité à médiation cellulaire anti-VZV dans les 18 premiers mois post-transplantation chez 8 de ces 9 enfants. Les résultats de ces expériences vont fournir d’importantes informations quant à la reconstitution de l’immunité anti-VZV à la suite d’une GMO ou d’une GSCO et pourraient permettre l’amélioration des soins apportés aux receveurs de GMO ou de GSCO.

Local adaptation in moss life histories: population-level variation and a reciprocal transplant experiment

We examine the extent of population-level differentiation in life history traits of Pogonatum aloides, Polytrichum commune and Polytrichum juniperinum (Polytrichaceae) between upland and lowland localities within Britain. Reciprocal transplant studies are used to estimate the relative importance of genetic versus environmental effects on observed differences. We demonstrate significant life history differentiation between moss populations, and show that at least some of these are genetically determined, although environment and phenotypic plasticity are also significant components of the observed variation. The transplant experiments indicate divergence among populations in plasticity of male reproductive effort and of investment in vegetative shoots by females. Two tradeoffs are identified; one between the number and the size of spores, and the second between reproduction by spores versus vegetative reproduction. The patterns of life history variation observed between populations of Polytrichum juniperinum are consistent with selection along these implied tradeoff curves, and we propose that they reflect selective pressures arising from the spatial and demographic distribution of mortality at upland versus lowland sites. The results underscore the need for more studies of intra-specific life history variation in mosses.

Seawater carbonate chemistry and MgCO3 concentration in bryozoan Myriapora truncata branches during experiments, 2011

There are serious concerns that ocean acidification will combine with the effects of global warming to cause major shifts in marine ecosystems, but there is a lack of field data on the combined ecological effects of these changes due to the difficulty of creating large-scale, long-term exposures to elevated CO2 and temperature. Here we report the first coastal transplant experiment designed to investigate the effects of naturally acidified seawater on the rates of net calcification and dissolution of the branched calcitic bryozoan Myriapora truncata (Pallas, 1766). Colonies were transplanted to normal (pH 8.1), high (mean pH 7.66, minimum value 7.33) and extremely high CO2 conditions (mean pH 7.43, minimum value 6.83) at gas vents off Ischia Island (Tyrrhenian Sea, Italy). The net calcification rates of live colonies and the dissolution rates of dead colonies were estimated by weighing after 45 days (May-June 2008) and after 128 days (July-October) to examine the hypothesis that high CO2 levels affect bryozoan growth and survival differently during moderate and warm water conditions. In the first observation period, seawater temperatures ranged from 19 to 24 °C; dead M. truncata colonies dissolved at high CO2 levels (pH 7.66), whereas live specimens maintained the same net calcification rate as those growing at normal pH. In extremely high CO2 conditions (mean pH 7.43), the live bryozoans calcified significantly less than those at normal pH. Therefore, established colonies of M. truncata seem well able to withstand the levels of ocean acidification predicted in the next 200 years, possibly because the soft tissues protect the skeleton from an external decrease in pH. However, during the second period of observation a prolonged period of high seawater temperatures (25-28 °C) halted calcification both in controls and at high CO2, and all transplants died when high temperatures were combined with extremely high CO2 levels. Clearly, attempts to predict the future response of organisms to ocean acidification need to consider the effects of concurrent changes such as the Mediterranean trend for increased summer temperatures in surface waters. Although M. truncata was resilient to short-term exposure to high levels of ocean acidification at normal temperatures, our field transplants showed that its ability to calcify at higher temperatures was compromised, adding it to the growing list of species now potentially threatened by global warming.

In-situ seawater pH and temperature during and fitness traits of a calcifying polychaete after a reciprocal transplant experiment in June-July near Ischia, italy

Ocean acidification (OA) is likely to exert selective pressure on natural populations. Our ability to predict which marine species will adapt to OA, and what underlies this adaptive potential, are of high conservation and resource management priority. Using a naturally low pH vent site in the Mediterranean Sea (Castello Aragonese, Ischia) mirroring projected future OA conditions, we carried out a reciprocal transplant experiment to investigate the relative importance of phenotypic plasticity and local adaptation in two populations of the sessile, calcifying polychaete /Simplaria /sp. (Annelida, Serpulidae, Spirorbinae): one residing in low pH and the other from a nearby ambient (i.e. high) pH site. We measured a suite of fitness related traits (i.e. survival, reproductive output, maturation, population growth) and tube growth rates in laboratory-bred F2 generation individuals from both populations reciprocally transplanted back into both ambient and low pH /in situ/ habitats. Both populations showed lower expression in all traits, but increased tube growth rates, when exposed to low pH compared to high pH conditions, regardless of their site of origin suggesting that local adaptation to low pH conditions has not occurred. We also found comparable levels of plasticity in the two populations investigated, suggesting no influence of long-term exposure to low pH on the ability of populations to adjust their phenotype. Despite high variation in trait values among sites and the relatively extreme conditions at sites close to the vents (pH < 7.36), response trends were consistent across traits. Hence, our data suggest that, for /Simplaria /and possibly other calcifiers, neither local adaptations nor sufficient phenotypic plasticity levels appear to suffice in order to compensate for the negative impacts of OA on long-term survival. Our work also underlines the utility of field experiments in natural environments subjected to high level of /p/CO_2 for elucidating the potential for adaptation to future scenarios of OA.