Consequences of fragmentation for the ability to adapt to novel environments in experimental <i>Drosophila</i> metapopulations

We used experimental populations of Drosophila melanogaster, which had either been subdivided (metapopulations) or kept undivided for 40 generations, to study the consequences of population subdivision for the tolerance and adaptive response after six generations of exposure to novel environmental factors (high temperature, medium with ethanol or salt added) for traits with different genetic architectures. In this setup, we attempted to separate the effects of the loss of fitness due to inbreeding (i.e., the survival upon first exposure to stress) from the loss of adaptive potential due to the lack of genetic variation. To place our experimental results in a more general perspective, we used individual-based simulations combining different options of levels of gene flow, intensity of selection and genetic architecture to derive quantitative hypotheses of the effects of these factors on the adaptive response to stress. We observed that population subdivision resulted in substantial inter-deme variation in tolerance due to redistribution of genetic variation from within demes to among demes. In line with the simulation results, the adaptive response was generally lower in the subdivided than in the undivided populations, particularly so for high temperature. We observed pronounced differences between stress factors that are likely related to the different genetic architectures involved in resistance to these factors. From a conservation genetics viewpoint, our results have two important implications: (i) Long-term fragmentation in combination with restricted gene flow will limit the adaptive potential of individual subpopulations because adaptive variation will become distributed among populations rather than within populations. (ii) The genetic architecture of the trait(s) under selection is of great significance to understand the possible responses to novel stresses that may be expected

Survival under conditions of variable food availability: Resource utilization and storage in the cold-water coral Lophelia pertusa

Cold‐water coral (CWC) reefs are hotspots of biodiversity and productivity in the deep sea, but their distribution is limited by the availability of food, which undergoes complex local and temporal variability. We studied the resource utilization, metabolism, and tissue storage of CWC Lophelia pertusa during an experimentally simulated 3‐day food pulse, of 13C15N‐enriched phytodetritus, followed by a 4‐week food deprivation. Oxygen consumption (0.145 μmol O2 [mmol organic carbon {OC}]−1 h−1), release of particulate organic matter (0.029 μmol particulate organic carbon [POC] [mmol OC]−1 h−1 and 0.005 μmol particulate organic nitrogen [mmol OC]−1 h−1), ammonium excretion (0.004 μmol NH4+ [mmol OC]−1 h−1), tissue C and N content, and fatty acid (FA) and amino acid composition did not change significantly during the experiment. Metabolization of the labeled phytodetritus, however, underwent distinct temporal dynamics. Initially, L. pertusa preferentially used phytodetritus‐derived C for respiration (2.2 ± 0.36 nmol C [mmol OC]−1 h−1) and mucus production (0.94 ± 0.52 nmol C [mmol OC]−1 h−1), but those tracer fluxes declined exponentially to <20% within 2 weeks after feeding and then remained stable, indicating that the remainder of the incorporated phytodetritus had entered a tissue pool with lower turnover. Analysis of 13C in individual FAs revealed a mismatch between the FAs incorporated from phytodetritus and the FA requirements of the coral. We suggest that feeding on other resources, such as lipid‐rich zooplankton, could fill this deficiency. A release of 10% of their total OC as respired C and POC during the 4‐week food deprivation underlines the importance of regular food pulses for CWC reefs.publishedVersio

Recycling pathways in cold-water coral reefs: Use of dissolved organic matter and bacteria by key suspension feeding taxa

Cold-water coral (CWC) reefs are one of the most diverse and productive ecosystems in the deep sea. Especially in periods of seasonally-reduced phytodetritus food supply, their high productivity may depend on the recycling of resources produced on the reef, such as dissolved organic matter (DOM) and bacteria. Here, we demonstrate that abundant suspension feeders Geodia barretti (high-microbial-abundance sponge), Mycale lingua (low-microbial-abundance sponge) and Acesta excavata (bivalve) are able to utilize 13C-enriched (diatom-derived) DOM and bacteria for tissue growth and respiration. While DOM was an important potential resource for all taxa, utilization of bacteria was higher for the sponges as compared to the bivalve, indicating a particle-size differentiation among the investigated suspension feeders. Interestingly, all taxa released 13C-enriched particulate organic carbon, which in turn may feed the detritus pathway on the reef. Especially A. excavata produced abundant (pseudo-)fecal droppings. A second stable-isotope tracer experiment revealed that detritivorous ophiuroids utilized these droppings. The high resource flexibility of dominant reef suspension feeders, and the efficient recycling of their waste products by the detritivore community, may provide important pathways to maintain the high productivity on cold-water coral reefs, especially in periods of low external food supply.publishedVersio

Increased aortic exclusion in endovascular treatment of complex aortic aneurysms

Purpose: Perioperative risk assessments for complex aneurysms are based on the anatomical extent of the aneurysm and do not take the length of the aortic exclusion into account, as it was developed for open repair. Nevertheless, in the endovascular repair (ER) of complex aortic aneurysms, additional segments of healthy aorta are excluded compared with open repair (OR). The aim of this study was to assess differences in aortic exclusion between the ER and OR of complex aortic aneurysms, to subsequently assess the current classification for complex aneurysm repair. Methods: This retrospective observational study included patients that underwent complex endovascular aortic aneurysm repair by means of fenestrated endovascular aneurysm repair (FEVAR), fenestrated and branched EVAR (FBEVAR), or branched EVAR (BEVAR). The length of aortic exclusion and the number of patent segmental arteries were determined and compared per case in ER and hypothetical OR, using a Wilcoxon signed-rank test. Results: A total of 71 patients were included, who were treated with FEVAR (n = 44), FBEVAR (n = 8), or BEVAR (n = 19) for Crawford types I (n = 5), II (n = 7), III (n = 6), IV (n = 7), and V (n = 2) thoracoabdominal or juxtarenal (n = 44) aneurysms. There was a significant increase in the median exclusion of types I, II, III, IV, and juxtarenal aneurysms (p < 0.05) in ER, compared with hypothetical OR. The number of patent segmental arteries in the ER of type I-IV and juxtarenal aneurysms was significantly lower than in hypothetical OR (p < 0.05). Conclusion: There are significant differences in the length of aortic exclusion between ER and hypothetical OR, with the increased exclusion in ER resulting in a lower number of patent segmental arteries. The ER and OR of complex aortic aneurysms should be regarded as distinct modalities, and as each approach deserves a particular risk assessment, future efforts should focus on reporting on the extent of exclusion per treatment modality, to allow for appropriate comparison.Vascular Surger

Hoor de Hofbogen: een onderzoek naar de geluidsbeleving

Research in and through artistic practic

Primary extraskeletal osteosarcoma of omentum majus

Extraskeletal osteosarcoma is a rare malignant soft tissue tumor. Here we present a case of a primary extraskeletal osteosarcoma arising from omentum majus in a 40-year-old Chinese woman. Ultrasonography of the pelvic cavity showed a large soft tissue mass with marked calcification. Complete surgical resection of the primary tumor was performed and the histopathological diagnosis was extraskeletal osteosarcoma of omentum majus. She was followed up without adjuvant radiotherapy and chemotherapy, and died from widespread intra-abdominal, lung and liver metastases 7 months postoperatively