Accurately predicting errors related to preservation, lipid extraction, and lipid normalization on chemical tracers would enable the use of archived samples in long-term studies of trophic ecology and habitat use of aquatic species. We determined whether stable carbon and nitrogen isotope ratios and concentrations of 14 trace elements can be accurately predicted from dimethyl sulfoxide (DMSO)-preserved mammal skin, which would provide equivalent estimates to that from unpreserved tissue. We tested 3 lipid-correction approaches for applicability to cetacean skin, a largely unexplored taxon and tissue, and provide a model for evaluating impacts of errors from lipid extraction or normalization on diet composition estimated using isotopic mixing models. DMSO had unpredictable effects on trace element concentrations, rendering DMSO-preserved samples inefficient for retrospective studies. However, lipid extraction and DMSO preservation resulted in predictable and similar, although not identical, effects on isotopic signatures across 4 cetacean species with different skin structure and thickness, making correction for these effects a potentially viable alternative to lipid and DMSO extraction. Generally, lipid-normalization models were reliable when applied to cetacean skin, as errors were similar to those from other species or tissues. Because model fit generally improved with data specificity, developing tissue-and species-specific parameters and equations is probably more important than model choice, although the mass-balance model was considered the most robust across aquatic vertebrates and tissues. The effects of errors associated with the various treatments and lipid normalization on isotopic mixing results increased as the isotopic distance among prey sources decreased, suggesting that empirical corrections as an alternative to δ 13 C determination from lipid-extracted duplicate samples need to be evaluated a priori relative to study objectives and anticipated results.

Carbon (δ13C) and nitrogen (δ15N) stable isotope ratios are increasingly used in ecological studies to evaluate diet composition and trophic relationships. However, lipids may influence stable isotope ratios due to the depletion of 13C in adipose tissues relative to proteins and carbohydrates. δ13C values can be corrected by lipid extraction or normalization models. The aims of our study were to evaluate the effects of lipid extraction on stable isotope ratios in a terrestrial mammal, the caribou (Rangifer tarandus caribou), and to propose relevant lipid normalization models that are method‐ and tissue‐specific for δ13C values. We also evaluated whether four δ13C lipid normalization and correction models proposed in the literature were applicable to our study species. Stable isotope ratios were obtained for hair, plasma, and red blood cell samples of 44 caribou in the Gaspésie National Park (Québec, Canada). The effects of lipid extraction on stable isotope ratios were tested using a paired t‐test. A simple linear model was used to correct for the effects of lipid extraction and to assess its performance compared to that of published equations. Lipid content significantly influenced δ13C values in caribou hair. The four lipid normalization equations commonly used in the literature did not accurately predict δ13Clipid‐free values of caribou hair. Based on our results, we recommend controlling systematically for lipids in terrestrial systems and analyzing δ13C (lipid‐free) and δ15N (bulk) from two separate aliquots to reach a greater precision. We also recommend controlling for lipids in hair tissue. If not possible, we recommend using a lipid normalization model that is tissue‐, method‐, and species‐specific or applying a model that has been previously validated for the tissue and species of interest.

Carbon and nitrogen stable isotope ratios are used widely to describe wildlife animal diet composition and trophic interactions. To reconstruct consumer diet, the isotopic differences between consumers and their diet items—called the trophic discrimination factor (TDF)—must be known. Proxies of diet composition are sensitive to the accuracy of TDFs. However, specific TDFs are still missing for many species and tissues because only a few controlled studies have been carried out on captive animals. The aim of this study was to estimate TDFs for hair and blood for carbon and nitrogen stable isotopes for caribou, moose, white-tailed deer, eastern coyote, and black bear. We obtained stable isotope ratios for diet items, hair, and blood samples, of 21 captive adult mammals. Diet–tissue discrimination factors for carbon in hair (∆ 13CLE) ranged from 0.96‰ to 3.72‰ for cervids, 3.01‰ to 3.76‰ for coyote, and 5.15‰ to 6.35‰ for black bear, while nitrogen discrimination factors (∆ 15N) ranged from 2.58‰ to 5.95‰ for cervids, 2.90‰ to 3.13‰ for coyote, and 4.48‰ to 5.44‰ for black bear. The ∆ 13CLE values in coyote blood components ranged from 2.20‰ to 2.69‰ while ∆ 15N ranged from 3.30‰ to 4.41‰. In caribou serum, ∆ 13CLE reached 3.34 ± 1.28‰ while ∆ 15N reached 5.02 ± 0.07‰. The TDFs calculated in this study will allow the evaluation of diet composition and trophic relationships between these five mammal species and will have important implications for the study of endangered caribou populations for which the use of noninvasive tissue sampling is highly relevant.

Stable isotopes and trace elements reflect interactions between individuals and their environment over shorter periods than genetic tracers and may capture contemporary patterns relevant to stock conservation and management. The endangered eastern Hudson Bay (EHB) belugas Delphinapterus leucas and those from the non-endangered western Hudson Bay (WHB) population are harvested during migration through Hudson Strait (HS), making protection of the endangered stock difficult. We assessed whether chemical tracers of beluga feeding ecology, i.e. carbon and nitrogen isotope ratios and concentrations of 27 trace elements, can help delineate wintering assemblages and successfully define summering stocks and their relative contributions to aboriginal harvests in HS. Skin was obtained from 1032 belugas in 9 regions of Hudson Bay, HS and southeast Baffin Island from 1989 to 2009. Isotopic signatures and trace element concentrations varied regionally and seasonally and suggest that several summering stocks and at least 3 winter assemblages exist. The use of isotopically defined summering stocks as sources in a discriminant function analysis indicates that the endangered EHB belugas account for 20 to 49% of the southern HS fall harvest. Low misclassification rates (≤10%) when using haplotypes unique to, or typical of, EHB belugas as a validation indicate that the isotopic approach is reliable. The analysis combining isotopes with trace elements is promising, although sample size is currently too small to define summering stocks. Spring signatures suggest that Cumberland Sound belugas winter in a separate area and may be differentiated from belugas found elsewhere in southeast Baffin Island, a contemporary pattern relevant to management.

Documenting trophic niche partitioning and resource use within a community is critical to evaluate underlying mechanisms of coexistence, competition, or predation. Detailed knowledge about foraging is essential as it may influence the vital rates, which, in turn, can affect trophic relationships between species, and population dynamics. The aims of this study were to evaluate resource and trophic niche partitioning in summer/autumn between the endangered Atlantic‐Gaspésie caribou (Rangifer tarandus caribou) population, moose (Alces americanus) and their incidental predators, the black bear (Ursus americanus) and coyote (Canis latrans), and to quantify the extent to which these predators consumed caribou. Bayesian isotopic analysis showed a small overlap in trophic niche for the two sympatric ungulates suggesting a low potential for resource competition. Our results also revealed that caribou occupied a larger isotopic niche area than moose, suggesting a greater diversity of resources used by caribou. Not surprisingly, coyotes consumed mainly deer (Odocoileus virginianus), moose, snowshoe hare (Lepus americanus), and occasionally caribou, while bears consumed mainly vegetation and, to a lesser extent, moose and caribou. As coyotes and bears also feed on plant species, we documented trophic niche overlap between caribou and their predators, as searching for similar resources can force them to use the same habitats and thus increase the encounter rate and, ultimately, mortality risk for caribou. Although the decline in the Gaspésie caribou population is mostly driven by habitat‐mediated predation, we found evidence that the low level of resource competition with moose, added to the shared resources with incidental predators, mainly bears, may contribute to jeopardize the recovery of this endangered caribou population. Highlighting the trophic interaction between species is needed to establish efficient conservation and management strategies to insure the persistence of endangered populations. The comparison of trophic niches of species sharing the same habitat or resources is fundamental to evaluate the mechanisms of coexistence or competition and eventually predict the consequences of ecosystem changes in the community.

Background In recent years, major advance has been made in the treatment of rheumatoid arthritis (RA). The efficacy of tumor necrosis factor-α (TNF-α) inhibitor has been demonstrated in different controlled clinical trials and observational studies. However, some patients have inadequate response to TNF-α inhibitors and may switch to an alternative treatment from a different class of drugs, such as abatacept (ABA), tocilizumab (TCZ) and rituximab (RTX). ABA, TCZ and RTX are indicated for use after inadequate response to traditional disease-modifying antirheumatic drugs (DMARD) or TNF-α inhibitors for the treatment of RA. Objectives The objective of this study was to assess in Canadian clinical practice the survival rate in patients with RA treated with a TNF-α inhibitor such as etanercept (ETN) and adalimumab (ADA) and alternative treatments such as ABA, TCZ and RTX. Methods Charts of all RA patients taking ETN, ADA, ABA, TCZ and RTX at the Centre de Rhumatologie de l'Est du Québec were reviewed and detailed data including 28-joint disease activity score (DAS28-ESR), start and end date and motive for discontinuation were recorded. Survival estimation was explored using Kaplan-Meier analysis and the log rank test was used to check for differences between the Kaplan-Meier curves using the statistical software R. Results A total of 474 RA patients starting treatment with ETN, ADA, ABA, TCZ or RTX were enrolled in this study. 158 patients were on ETN, 128 patients were on ADA, 73 patients were on ABA, 54 patients were on TCZ and 61 patients were on RTX therapies. Overall, DAS28-ESR decreased from 4.37 at baseline to 2.80 at month 24 for ETN, from 4.37 to 2.98 for ADA, from 4.58 to 4.06 for ABA, from 5.31 to 3.24 for TCZ and from 4.65 to 2.97 for RTX. After 24 months, using Kaplan-Meier curves plotted for all treatments, 56% of patients are still on ETN, 39% of patients are still on ADA, 38% of patients are still on ABA, 55% of patients are still on TCZ and 67% of patients are still on RTX. However, for biologic-naïve patients, 57% of patients are still on ETN, 48% of patients are still on ADA, 63% of patients are still on ABA, 73% of patients are still on TCZ and 100% of patients are still on RTX (n=2) at month 24. Statistical tests of comparison between treatment revealed significant differences (log-rank: p=0.000125). Conclusions The present study suggests that the survival rate for biologic-naïve patients is higher than on patients who failed to respond to their previous biologic. It also suggests that RTX has a better survival rate than ETN, ADA, ABA and TCZ in second line treatment. Also, ADA, ABA and TCZ has better profile when used as a first-line agent. References Girolomoni et al., 2012, Karlsson et al., 2008, Hublein et al., 2012, Strand et al., 2013 Disclosure of Interest None declared DOI 10.1136/annrheumdis-2014-eular.3681

Background Psoriatic arthritis (PsA) is characterised by arthritis, psoriasis, sacroilitis, enthesitis and dactylitis. The efficacy of tumor necrosis factor-α (TNF-α) inhibitor has been demonstrated in different controlled clinical trials and observational studies. However, some patients have inadequate response to TNF-α inhibitors and no alternative mechanism of action is available for those who failed more than one anti-TNF. Ustekinumab is an efficacious treatment for psoriasis and may be useful in patients with active psoriatic arthritis. Objectives The objective of this study was to assess in Canadian clinical practice the efficacy of ustekinumab in patients with psoriatic arthritis who failed to one or more TNF-α inhibitors agents. Methods Charts of patients taking ustekinumab at the Centre de Rhumatologie de l'Est du Québec were reviewed and detailed data including demographic information, disease characteristics, 28-joint disease activity score (DAS28-CRP), BASDAI, BASFI, SPARCC and Health Assessment Questionnaire-Disease Index (HAQ-DI) were collected. Descriptive statistics were used to describe patients initiating ustekinumab in this real-world setting. Results A total of 9 patients starting treatment with ustekinumab were enrolled in this study. Patients have failed an average of 3.66 anti-TNF agents. Overall, DAS28-CRP decreased from 4.39 at baseline to 3.84 at month 12. HAQ-DI decreased from 1.97 to 1.52. BASDAI decreased from 8.16 to 6.9. BASFI decreased from 7.18 to 5.70. SPARCC increased from 2 to 3.66. Mean number of dactylitis decreased from 4.22 to 0. Finally, all patients have improved their psoriasis after 12 months. Two patients discontinued the treatment because of a secondary failure and an adverse event (nausea, low back pain). Conclusions The present study suggests that ustekinumab improved active psoriatic arthritis and may offer an alternative treatment for patients who failed to respond to their previous anti-TNF. The most impressive effect is the improvement of enthesitis and dactylitis. It is even more interesting that the response was good nevertheless the number who have failed to an anti-TNF. This suggests that another mode of action will probably be a part of the treatment in PsA as it is in rheumatoid arthritis. However, this is an exploratory study and a larger sample is needed for better interpretation. References McInnes et al., 2013. Efficay and safety of ustekinumab in patients with active psoriatic arthritis: 1 year results of the phase 3, multicentre, double-blind, placebo-controlled PSUMMIT 1 trial. Lancet 382:780-789. Mease, P.J., 2011. Measures of psoriatic arthritis, Arthritis Care and Research, 63(S11): S65-S85 GRAPPA, 2013. Group for Research and Assessment of Psoriasis and Psoriatic Arthritis. Disclosure of Interest None declared DOI 10.1136/annrheumdis-2014-eular.3688

Sexual size dimorphism is a common phenomenon in mammals, and researchers have been trying to demonstrate the evolutionary causes leading to sexual dimorphism. Two main hypotheses emerged: (1) the sexual selection hypothesis and (2) the sexual competition hypothesis (also called resource partitioning hypothesis). Here, we attempted to link sexual dimorphism in fishers ( Pekania pennanti (Erxleben, 1777)) with their fall diet using stable isotope profiling and body and skull measurements. We used the carcasses of 39 fishers which were caught in eastern Québec during fall 2014 by volunteer trappers as well as several potential prey items ranging from small rodents to cervids. We expected minimal niche overlap between sexes, as males should be able to exploit different prey species than females. We also expected to observe an effect of age class (adults vs. juveniles) on trophic niche. As expected, we found great evidence of sexual dimorphism in both body mass and skull measurements: males were heavier and longer than females and had a larger zygomatic and intracanine width and a longer skull. While proportions of prey in diet according to sex and age did not vary greatly, we found some evidence of niche partitioning using Layman's metrics. Indeed, females tended to have a less diversified and more similar diet compared to one another, whereas males showed more diversified and contrasted diets. Despite our limited sample size, our findings provide partial support to the sexual competition hypothesis, as the difference in body and skull size based on sex could have evolved to lessen intraspecific competition in fishers.