An interpretation of oncoid mass-occurrence during the Late Silurian Lau Event, Gotland, Sweden

The geological significance of the microbial-formed oncoid is not as well understood as the recognized, analogous stromatolite but can, as well be used as an environmental indicator. In association with the larger Phanerozoic mass extinctions, a resurgence of microbialites as a disaster fauna is at present an accepted view. The same model, however, is under debate concerning whether or not it can be applied to minor extinction events such as the Lau Event, a coupled extinction-isotopic event recorded from Late Silurian. The Lau Event displays one of the largest positive carbon isotope excursions (CIE) during the entire Phanerozoic with detrimental effects on various marine fauna. The last appearance datum (LAD) of the conodont species P. siluricus in the uppermost Hemse Group on Gotland marks the commencement of the event and the superimposing Eke Formation is extremely rich in oncoids. To analyze the specific controlling determinants and the potential for oncoids as environmental indicators, I measured size and shape for over one hundred oncoids deriving from Gotland and Bjärsjölagård, Sweden. Thin sections and cross-sections of oncoids were produced and Rothpletzella was by far the most abundant calcimicrobe in oncoid cortex, often associated with Wetheredella. Results herein strengthen the theory of the mass abundant oncoids constituting an anachronistic facies. Furthermore, oncoid- shape and morphology are concluded herein to, with caution, be used as indicators of water energy which sets the deposition of the Eke Formation under a phase of transgression.Den geologiska signifikansen av onkoider, mikrobialiter uppbyggda av calcifierande mikroorganismer, är varken lika studerad eller vedertagen som för de likartade stromatoliterna. I samband med de större fanerozoiska utdöenderna är ett uppsving av dessa mikrobialiter ett accepterat bevis för en krisfauna vilken utgör ett anarchronistiskt facies. Desto mer omdebatterad är möjligheten att applicera denna modell även på mindre utdöenden som Lau Event, ett event kopplat till ett udöende samt till en av de största kolisotop anomalierna under hela Fanerozoikum. Utdöendet av konodonten P.siluricus markerar eventets början och den överlagrande Eke Formationen är väldigt rik i onkoider. För att analysera biologisk determinism och onkoidernas potential som miljöindikatorer har storlek och form på över hundra onkoider analyserats från södra Gotland och Bjärsjölagård i centrala Skåne. Ett representativt urval gjordes för vidare analys i form av bland annat genomskärning, isotopprov och tunnslipsframställning. Resultaten styrker teorin att onkoiderna utgör en krisfauna. Genom studier av tunnslip visas Rothpletzella vara den dominerande mikroorganismen i onkoidkortex. Fortsättningsvis, kontateras att onkoiders form och storlek är lämpliga parametrar för att i större utsträckning användas som indikatorer för vattenenergi. Detta sätter depositionen av Eke Formationen under en fas av trangression

Multicellular Tumour Spheroid as a model for evaluation of [(18)F]FDG as biomarker for breast cancer treatment monitoring

BACKGROUND: In order to explore a pre-clinical method to evaluate if [(18)F]FDG is valid for monitoring early response, we investigated the uptake of FDG in Multicellular tumour spheroids (MTS) without and with treatment with five routinely used chemotherapy agents in breast cancer. METHODS: The response to each anticancer treatment was evaluated by measurement of the [(18)F]FDG uptake and viable volume of the MTSs after 2 and 3 days of treatment. RESULTS: The effect of Paclitaxel and Docetaxel on [(18)F]FDG uptake per viable volume was more evident in BT474 (up to 55% decrease) than in MCF-7 (up to 25% decrease). Doxorubicin reduced the [(18)F]FDG uptake per viable volume more noticeable in MCF-7 (25%) than in BT474 MTSs. Tamoxifen reduced the [(18)F]FDG uptake per viable volume only in MCF-7 at the highest dose of 1 μM. No effect of Imatinib was observed. CONCLUSION: MTS was shown to be appropriate to investigate the potential of FDG-PET for early breast cancer treatment monitoring; the treatment effect can be observed before any tumour size changes occur. The combination of PET radiotracers and image analysis in MTS provides a good model to evaluate the relationship between tumour volume and the uptake of metabolic tracer before and after chemotherapy. This feature could be used for screening and selecting PET-tracers for early assessment of treatment response. In addition, this new method gives a possibility to assess quickly, and in vitro, a good preclinical profile of existing and newly developed anti-cancer drugs

Asymmetric Reproductive Isolation between Two Sympatric Annual Killifish with Extremely Short Lifespans

BACKGROUND: Interspecific reproductive isolation is typically achieved by a combination of intrinsic and extrinsic barriers. Behavioural isolating barriers between sympatric, closely related species are often of primary importance and frequently aided by extrinsic factors causing spatial and temporal interspecific separation. Study systems with a severely limited role of extrinsic factors on reproductive isolation may provide valuable insights into how reproductive isolation between sympatric species is maintained. We used no-choice experimental set-up to study reproductive barriers between two closely related sympatric African killifish species, Nothobranchius furzeri and Nothobranchius orthonotus. These fish live in small temporary savannah pools and have complete spatial and temporal overlap in reproductive activities and share a similar ecology. PRINCIPAL FINDINGS: We found that the two species display largely incomplete and asymmetric reproductive isolation. Mating between N. furzeri males and N. orthonotus females was absent under standard experimental conditions and eggs were not viable when fish were forced to mate in a modified experimental setup. In contrast, male N. orthonotus indiscriminately mated with N. furzeri females, the eggs were viable, and offspring successfully hatched. Most spawnings, however, were achieved by male coercion and egg production and embryo survival were low. Behavioural asymmetry was likely facilitated by mating coercion from larger males of N. orthonotus and at relatively low cost to females. Interestingly, the direction of asymmetry was positively associated with asymmetry in post-mating reproductive barriers. SIGNIFICANCE: We showed that, in fish species with a promiscuous mating system and multiple matings each day, selection for strong mate preferences was relaxed. This effect was likely due to the small proportion of resources allocated to each single mating and the high potential cost to females from mating refusal. We highlight and discuss the fact that males of rarer species may often coercively mate with females of a related, more abundant species

Does personality affect premating isolation between locally-adapted populations?

Background: One aspect of premating isolation between diverging, locally-adapted population pairs is female mate choice for resident over alien male phenotypes. Mating preferences often show considerable individual variation, and whether or not certain individuals are more likely to contribute to population interbreeding remains to be studied. In the Poecilia mexicana-species complex different ecotypes have adapted to hydrogen sulfide (H2S)-toxic springs, and females from adjacent non-sulfidic habitats prefer resident over sulfide-adapted males. We asked if consistent individual differences in behavioral tendencies (animal personality) predict the strength and direction of the mate choice component of premating isolation in this system. Results: We characterized focal females for their personality and found behavioral measures of ‘novel object exploration’, ‘boldness’ and ‘activity in an unknown area’ to be highly repeatable. Furthermore, the interaction term between our measures of exploration and boldness affected focal females’ strength of preference (SOP) for the resident male phenotype in dichotomous association preference tests. High exploration tendencies were coupled with stronger SOPs for resident over alien mating partners in bold, but not shy, females. Shy and/or little explorative females had an increased likelihood of preferring the non-resident phenotype and thus, are more likely to contribute to rare population hybridization. When we offered large vs. small conspecific stimulus males instead, less explorative females showed stronger preferences for large male body size. However, this effect disappeared when the size difference between the stimulus males was small. Conclusions: Our results suggest that personality affects female mate choice in a very nuanced fashion. Hence, population differences in the distribution of personality types could be facilitating or impeding reproductive isolation between diverging populations depending on the study system and the male trait(s) upon which females base their mating decisions, respectively

Population genomics of speciation and admixture

The application of population genomics to the understanding of speciation has led to the emerging field of speciation genomics. This has brought new insight into how divergence builds up within the genome during speciation and is also revealing the extent to which species can continue to exchange genetic material despite reproductive barriers. It is also providing powerful new approaches for linking genotype to phenotype in admixed populations. In this chapter, we give an overview of some of the methods that have been used and some of the novel insights gained. We also outline some of the pitfalls of the most commonly used methods and possible problems with interpretation of the results

Social network analysis resolves temporal dynamics of male dominance relationships

Social organization is often studied through point estimates of individual association or interaction patterns, which does not account for temporal changes in the course of familiarization processes and the establishment of social dominance. Here, we present new insights on short-term temporal dynamics in social organization of mixed-sex groups that have the potential to affect sexual selection patterns. Using the live-bearing Atlantic molly (Poecilia mexicana), a species with pronounced male size polymorphism, we investigated social network dynamics of mixed sex experimental groups consisting of eight females and three different-sized males over a period of 5 days. Analyzing association-based social networks as well as direct measures of spatial proximity, we found that large males tended to monopolize most females, while excluding small- and medium-bodied males from access to females. This effect, however, emerged only gradually over time, and different-sized males had equal access to females on day 1 as well as day 2, though to a lesser extent. In this highly aggressive species with strong social dominance stratifications, the observed temporal dynamics in male-female association patterns may balance the presumed reproductive skew among differentially competitive male phenotypes when social structures are unstable (i.e., when individual turnover rates are moderate to high). Ultimately, our results point toward context-dependent sexual selection arising from temporal shifts in social organization. © 2014 Springer-Verlag Berlin Heidelberg

Opposing patterns of intraspecific and interspecific differentiation in sex chromosomes and autosomes

Funding: Natural Environment Research Council grants to N.W.B., Grant/Award numbers: NE/G014906/1, NE/L011255/1; Orthopterists’ Society grant to P.A.M.Linking intraspecific and interspecific divergence is an important challenge in speciation research. X chromosomes are expected to evolve faster than autosomes and disproportionately contribute to reproductive barriers, and comparing genetic variation on X and autosomal markers within and between species can elucidate evolutionary processes that shape genome variation. We performed RADseq on a 16‐population transect of two closely‐related Australian cricket species, Teleogryllus commodus and T. oceanicus, covering allopatry and sympatry. This classic study system for sexual selection provides a rare exception to Haldane's rule, as hybrid females are sterile. We found no evidence of recent introgression, despite the fact that the species co‐exist in overlapping habitats in the wild and interbreed in the laboratory. Putative X‐linked loci showed greater differentiation between species compared to autosomal loci. However, population differentiation within species was unexpectedly lower on X‐linked markers than autosomal markers, and relative X‐to‐autosomal genetic diversity was inflated above neutral expectations. Populations of both species showed genomic signatures of recent population expansions, but these were not strong enough to account for the inflated X/A diversity. Instead, most of the excess polymorphism on the X could better be explained by sex‐biased processes that increase the relative effective population size of the X, such as interspecific variation in the strength of sexual selection among males. Taken together, the opposing patterns of diversity and differentiation at X versus autosomal loci implicate a greater role for sex‐linked genes in maintaining species boundaries in this system.PostprintPeer reviewe

Who ate whom? Paleoecology revealed through synchrotron microtomography of coprolites (fossil feces)

Fossil droppings, known as coprolites, are being increasingly recognized as a valuable source of paleoecological information with special regard to diets, parasitism, and physiology of extinct taxa. Here, it is suggested that the excellent preservation and amount of inclusions in the coprolites (e.g. food residues and parasites) qualifies them as Lagerstätten – deposits with exceptional paleontological information. However, two interlinked problems commonly arise when they are studied. Firstly, it is often difficult to tie coprolites to producers and, secondly, it is challenging to recognize the fragmented and randomly distributed inclusions in their matrix. Here I use propagation phase-contrast synchrotron microtomography (PPC-SRμCT) in combination with other techniques to solve these problems. As a result, the oldest known example of archosaurian osteophagy is uncovered based on inter alia the occurrence of serrated teeth and many crushed bones in coprolites assigned to the Late Triassic theropod-like archosaur Smok wawelski. Osteophagy has previously been thought to be rare among extinct archosaurs with the exception of Late Cretaceous tyrannosaurids. This suggests some degree of ecological convergence between the tyrannosaurids and S. wawelski. Furthermore, exceptionally-preserved beetle remains are discovered in coprolites tentatively assigned to the Triassic dinosauriform Silesaurus opolensis, which had a specialized dentition and possessed beak-shaped jaws that were likely used to peck insects off the ground. Moreover, pterosaur coprolites are shown to contain similar food residues as found in droppings of recent flamingos, implying that some Late Jurassic pterosaurs were filter feeders. I argue that such paleoecological studies have a large impact on our understanding of ancient animals, and that studies of coprolites can unravel parts of ancient food webs in unprecedented ways. Information on past food webs may, in turn, be used to analyze trophic changes through time, which could cast new light on big evolutionary events. This is demonstrated by reconstructing trophic structures in early Mesozoic assemblages that represent snapshots of three stages of early dinosaur evolution