The gut microbiome of solitary bees is mainly affected by pathogen assemblage and partially by land use.

Pollinators, including solitary bees, are drastically declining worldwide. Among the factors contributing to this decline, bee pathogens and different land uses are of relevance. The link between the gut microbiome composition and host health has been recently studied for social pollinators (e.g. honeybees), whereas the information related to solitary bees is sparse. This work aimed at the characterization of the gut microbiome of the solitary bees Xylocopa augusti, Eucera fervens and Lasioglossum and attempted to correlate the gut microbial composition with the presence and load of different pathogens and land uses. Solitary bees were sampled in different sites (i.e. a farm, a natural reserve, and an urban plant nursery) showing different land uses. DNA was extracted from the gut, 16S rRNA gene amplified and sequenced. Eight pathogens, known for spillover from managed bees to wild ones, were quantified with qPCR. The results showed that the core microbiome profile of the three solitary bees significantly varied in the different species. Pseudomonas was found as the major core taxa in all solitary bees analyzed, whereas Lactobacillus, Spiroplasma and Sodalis were the second most abundant taxa in X. augusti, E. fervens and Lasioglossum, respectively. The main pathogens detected with qPCR were Nosema ceranae, Nosema bombi and Crithidia bombi, although differently abundant in the different bee species and sampling sites. Most microbial taxa did not show any correlation with the land use, apart from Snodgrassella and Nocardioides, showing higher abundances on less anthropized sites. Conversely, the pathogens species and load strongly affected the gut microbial composition, with Bifidobacterium, Apibacter, Serratia, Snodgrassella and Sodalis abundance that positively or negatively correlated with the detected pathogens load. Therefore, pathogens presence and load appear to be the main factor shaping the gut microbiome of solitary bees in Argentina.

HEMATOLOGIC METRICS FROM OLROG'S GULL (LARUS ATLANTICUS) DURING THE NONBREEDING SEASON IN ARGENTINA.

Ecophysiology and conservation studies often require the prior establishment of baseline physiologic metrics. For instance, expected reference intervals for health metrics are valuable tools for veterinarians and conservationists who monitor the health status of endangered populations and species. This study establishes reference intervals for hematologic metrics in free-ranging Olrog's gull (Larus atlanticus) during the nonbreeding season. Fifty-six gulls (immature and adults) were captured and studied in Mar del Plata and neighboring coastal areas (Buenos Aires, Argentina) during the winter of 2018 (n = 22) and 2019 (n = 34). Hematocrit, red blood cells (erythrocytes), hemoglobin, mean cell volume, mean cell hemoglobin (MCH), MCH concentration, white blood cells (WBC; leukocytes), heterophils, lymphocytes, eosinophils, monocytes, and basophils were analyzed. Additionally, the variability of hematologic metrics according to body weight, sex, age, and calendar year was examined. Hematologic metrics were in line with those reported in other seabird species. Males had greater body weight and MCH than females. The heterophil to lymphocyte ratio and lymphocyte levels were higher in adults than in immatures. Hematocrit, WBC, heterophils, and basophils also varied significantly between calendar years. The results highlight the importance of appropriate metrics and reference intervals for monitoring the health status of this threatened species, and it is recommended to implement such comparative assessments among populations.

SERUM BIOCHEMISTRY VALUES FOR THE OLROG'S GULL (LARUS ATLANTICUS): A STUDY BASED ON FREE-LIVING INDIVIDUALS.

Analysis of serum parameters provides information about body condition, nutritional state, and health status of individuals/species, and has broad application in ecological research and veterinary diagnosis. This study establishes baseline values for serum chemistries of the Olrog's gull (Larus atlanticus). Glucose, urea, uric acid, total protein, globulin, albumin, cholesterol, triglyceride, calcium, and phosphorus concentrations were determined, as was the activity of the following enzymes: alkaline phosphatase, creatine phosphokinase, aspartate aminotransferase, and alanine aminotransferase. Thirty nonbreeding gulls (juvenile and subadult individuals) were captured and studied in Mar Chiquita Reserve (Buenos Aires, Argentina) during the wintering periods 2016 (n = 17) and 2017 (n = 13). In general terms, most values for the parameters reported were in line with those previously described for other seabirds. The year had a significant effect on several of the biochemical parameters evaluated, and the sex had a significant effect on the alkaline phosphatase and calcium. This study has defined the serum biochemical reference signatures for free-ranging Olrog's gulls during the nonbreeding period, and contributes to the knowledge of the overall health status of this threatened and endemic species.