Risk perception and its influence on ant foraging

Mrówki są modelowym przykładem eusocjalnych zwierząt. Współpraca między ich osobnikami pozwala na wykształcenie zaawansowanych mechanizmów optymalizujących efektywność żerowania, a percepcja oraz komunikowanie ryzyka jest jednym z nich. Celem niniejszej pracy była weryfikacja hipotezy, że umieszczenie mrówki unieruchomionej lub martwej, sugerujące potencjalne ryzyko, obok źródła pokarmu wpłynie na liczbę żerujących mrówek. W przeprowadzonym eksperymencie wykorzystano pospolity w Europie gatunek mrówki – Lasius niger. Za źródło pokarmu posłużyły karmidła zrobione z probówek wypełnionych wodą z cukrem, które rozstawiono na zmiennowilgotnej łące. Po dwóch godzinach przy części karmideł zabito lub unieruchomiono mrówki a następnie odczekano godzinę by przeprowadzić kolejne obserwacje. W próbie kontrolnej przy 64% karmidłach zaobserwowano zwiększenie liczby mrówek. W próbie z unieruchomioną mrówką liczba mrówek spadła przy 72% karmideł, a w grupie z mrówką zabitą spadłą przy 90%. Stwierdzono, że względne zmiany liczby mrówek w kolejnych obserwacjach różniły się istotnie między grupą kontrolną a grupą z mrówkami unieruchomionymi oraz między grupą kontrolną a grupą z mrówkami zabitymi (test Kruskala-Wallisa: P = 0,0147, testy post hoc P < 0,05). Można zatem wnioskować, że umieszczenie mrówki unieruchomionej lub zabitej przy karmidełku miało negatywny wpływ na liczbę furażujących mrówek.Ants are a model example of eusocial animals. Cooperation between their individuals allows the development of advanced mechanisms to optimize foraging efficiency, and risk perception and communication is one of them. The aim of the present study was to verify the hypothesis that placing an immobilized or dead ant, which suggests a potential risk, in the vicinity of a displayed feeder affects the number of foraging ants. Lasius niger, a common ant species in Europe, was used in the experiment. Feeders made of test-tubes filled with water and sugar, and the test-tubes were set up on a wet meadow. After 2 hours either an immobilized ant was placed at the feeder (1st experimental group) or a killed ant was placed there (2nd experimental group), the third group was a control trial without intervention. After one hour, observation of the number of foraging ants was made. In the control sample, an increase in ant numbers was observed at 64% of the feeders. At the sample with an immobilized ant, ant numbers decreased at 72% of the feeders. At the sample with a killed ant, the number of foraging ants also decreased in the vast majority of cases, as a decrease was observed at 90% of the feeders. It was found that the relative changes in the number of ants in subsequent observations differed significantly between the control group and the immobilized ant group as well as between the control group and the killed ant group (Kruskal-Wallis test: P = 0,0147, post hoc tests P < 0.05). Therefore, it can be concluded that placing an immobilized or killed ant at the feeder deters foraging ants

The Pre-Transplant Drop in Panel-Reactive Antibodies Titer Evaluated Using Complement-Dependent Cytotoxicity (PRA-CDC) and the Risk of Early Acute Rejection in Sensitized Kidney Transplant Recipients

Background: The panel-reactive antibodies that use the complement-dependent cytotoxicity test (PRA-CDC) are still a standard method for monitoring the degree of immunization in kidney transplant candidates on active waiting lists in some countries, including Poland. The aim of this study was to analyze the relationship between the maximum and the last pre-transplant PRA titer on the percentage of positive cross-matches and rate of early acute rejection episodes. Material and methods: The retrospective analysis included 528 patients from two transplant centers. All patients were divided into three groups, depending on their peak and last pre-transplant PRA titers. There were 437 (82.8%) patients with peak PRA &lt;20% (non-sensitized group, non-ST) and 91 (17.2%) patients with peak PRA &gt;20%. Among the latter group, 38 had maintained PRA level &gt;20% at the time of transplantation (sensitized patients, ST), whereas 53 had pre-transplant PRA &le;20% (previously sensitized patients, prev-ST). Results: The percentages of positive crossmatches were 76.9% in ST and 53.7% in prev-ST groups versus 18.4 in non-ST group (both p &lt; 0.001). The acute rejection rates were 18.9, 17.6 and 6.8%, respectively (p &lt; 0.001 for ST or prev-ST versus non-ST). The pre-transplant PRA titer drop did not decrease the risk of early acute rejection [OR = 1.09 (95% CI: 0.31&ndash;3.85)] in a multiple logistic regression analysis. The occurrences of primary graft non-function and delayed graft function were similar in all study groups. Conclusions: Previously immunized kidney transplant candidates even with substantial decrease in pre-transplant PRA-CDC levels are still at high immunological risk when compared with non-immunized patients, and they should receive lymphocyte-depleting induction therapy