Modelling the future of the Hawaiian honeycreeper : an ecological and epidemiological problem

The Hawaiian honeycreeper (Drepanididae) faces the threat of extinction; this is believed to be due primarily to predation from alien animals, endemic avian malaria (Plasmodium relictum) and climate change. A deterministic SI modelling approach is developed, incorporating these three factors and a metapopulation approach in conjunction with a quasi-equilibrium assumption to simplify the vector populations. This enables the qualitative study of the behaviour of the system. Numerical results suggest that although (partial) resistance to avian malaria may be advantageous for individual birds, allowing them to survive infection, this allows them to become carriers of infection and hence greatly increases the spread of this disease. Predation obviously reduces the life-expectancy of honeycreepers, but in turn this reduces the spread of infection from resistant carriers; therefore the population-level impact of predation is reduced. Various control strategies proposed in the literature are also considered and it is shown that predation control could either help or hinter, depending upon resistance of the honeycreeper species. Captive propagation or habitat restoration may be the best feasible solution to the loss of both heterogeneity within the population and the loss of the species as a whole

Verified and potential pathogens of predatory mites (Acari: Phytoseiidae)

Several species of phytoseiid mites (Acari: Phytoseiidae), including species of the genera Amblyseius, Galendromus, Metaseiulus, Neoseiulus, Phytoseiulus and Typhlodromus, are currently reared for biological control of various crop pests and/or as model organisms for the study of predator¿prey interactions. Pathogen-free phytoseiid mites are important to obtain high efficacy in biological pest control and to get reliable data in mite research, as pathogens may affect the performance of their host or alter their reproduction and behaviour. Potential and verified pathogens have been reported for phytoseiid mites during the past 25 years. The present review provides an overview, including potential pathogens with unknown host effects (17 reports), endosymbiotic Wolbachia (seven reports), other bacteria (including Cardinium and Spiroplasma) (four reports), cases of unidentified diseases (three reports) and cases of verified pathogens (six reports). From the latter group four reports refer to Microsporidia, one to a fungus and one to a bacterium. Only five entities have been studied in detail, including Wolbachia infecting seven predatory mite species, other endosymbiotic bacteria infecting Metaseiulus (Galendromus, Typhlodromus) occidentalis (Nesbitt), the bacterium Acaricomes phytoseiuli infecting Phytoseiulus persimilis Athias-Henriot, the microsporidium Microsporidium phytoseiuli infecting P. persimilis and the microsporidium Oligosproridium occidentalis infecting M. occidentalis. In four cases (Wolbachia, A. phytoseiuli, M. phytoseiuli and O. occidentalis) an infection may be connected with fitness costs of the host. Moreover, infection is not always readily visible as no obvious gross symptoms are present. Monitoring of these entities on a routine and continuous basis should therefore get more attention, especially in commercial mass-production. Special attention should be paid to field-collected mites before introduction into the laboratory or mass rearing, and to mites that are exchanged among rearing facilities. However, at present general pathogen monitoring is not yet practical as effects of many entities are unknown. More research effort is needed concerning verified and potential pathogens of commercially reared arthropods and those used as model organisms in research

The Dynamics of an SIS Epidemic Disease with Contact and External Source

In this paper, we discuss the dynamical behavior of eco-epidemiological mathematical model consisting of prey-predator model involving SIS infectious disease in prey population, is proposed and analyzed. This disease passed from a prey to predator through attacking of predator to prey. It is assumed that the disease transmitted within the same species by contact between susceptible individuals and infected individuals, in additional to the external sources from the environment. The existence, uniqueness and boundedness of the solution of the system are studied. The local and global stability conditions of all possible equilibrium points are established. Finally, some numerical simulations are given to illustrate the analytical results. Keywords: prey-predator model, SIS epidemics disease, stability analysis, Lyapunov function

Direkte und indirekte Effekte von eingeschleppten Parasiten auf heimische Miesmuscheln

The role of parasites in invasion processes have become an increasing phenomenon due to the continuous increase in the rate of biological invasions in marine ecosystems. When parasites themselves are invasive and spill over to native species, they can exert a number of direct and indirect effects on their new host and interacting species. Direct effects often affect the new host in multiple ways that result in further indirect effects downstream. Moreover, the occurrence of indirect effects might change the interaction of the host to interacting species. As a result of both, direct and indirect effects, parasites can change the sensitivity of the host against further impacts like climate change and/or secondary infections. This can have profound ecological consequences for native biota. In combination, the challenges of invasion processes and climate change bear the risk of species homogenization and disease emergence. Against this background, it is an urgent task of marine science to assess future impacts and consequences of parasite invasions and climate change. The present study investigates the direct and indirect effects of the invasive parasite Mytilicola intestinalis on native blue mussels. The study is divided into three chapters; the first chapter addresses the direct effects, while the second and third chapter considers indirect effects.Mit der Zunahme biologischer Invasionen innerhalb des marinen Ökosystems wächst die Rolle von Parasiten in solchen Invasionsprozessen stetig. Wenn Parasiten selbst invasiv sind und auf heimische Arten überwechseln, können sie eine Reihe direkter und indirekter Effekte auf den neuen Wirt und die mit ihm interagierenden Arten ausüben. Direkte Effekte wirken auf vielfältige Weise auf den Wirt ein, daraus können wiederum indirekte Effekte hervorgehen. Indirekte Effekte können weiter auf die Interaktion zwischen Wirten und die mit ihnen wechselwirkenden Arten einwirken. Als Folge von beidem (direkten und indirekten Effekten) können Parasiten die Sensibilität eines Wirtes gegenüber weiteren Einflüssen, wie beispielsweise veränderten Klimabedingungen und/oder Sekundärinfektionen, beeinflussen. Dies hat tiefgreifende ökologische Auswirkungen für heimische Arten. Insgesamt bergen die Herausforderungen von Invasionsprozessen und dem Klimawandel das Risiko der Artenhomogenisierung und dem Aufkommen von Krankheiten. Vor diesem Hintergrund ist es eine der Hauptaufgaben der marinen Forschung zukünftige Einflüsse und Folgen von parasiten-beeinflussten Invasionen und dem Klimawandel abzuschätzen. In der vorliegenden Arbeit werden die direkten und indirekten Effekte des invasiven Parasiten Mytilicola intestinalis auf heimische Miesmuscheln untersucht. Die Arbeit gliedert sich in drei Kapitel, das erste Kapitel befasst sich mit den direkten Effekten, Kapitel zwei und drei mit den indirekten Effekten

Insight into the possible use of the predator Bdellovibrio bacteriovorus as a probiotic

The gut microbiota is a complex microbial ecosystem that coexists with the human organism in the intestinal tract. The members of this ecosystem live together in a balance between them and the host, contributing to its healthy state. Stress, aging, and antibiotic therapies are the principal factors aecting the gut microbiota composition, breaking the mutualistic relationship among microbes and resulting in the overgrowth of potential pathogens. This condition, called dysbiosis, has been linked to several chronic pathologies. In this review, we propose the use of the predator Bdellovibrio bacteriovorus as a possible probiotic to prevent or counteract dysbiotic outcomes and look at the findings of previous research

Cleaning symbiosis and the disease triangle

Pauline Narvaez found that the dedicated cleaner fish, Labroides dimidiatus, is susceptible to a diversity of parasites and can potentially transmit them to their fish clients. Her work presents a paradigm shift in the prevailing theory that cleaning symbiosis has predominantly positive impacts on coral reef fish communities

Analysis of a Mathematical Model in a Food Web System Containing Scavenger Species

في هذا البحث قد تم رياضيا صياغة ديناميكية أنواع صائد الفرائس في نموذج شبكة الغذاء بدمج التأخير الزمني و حصاد الفريسة. ان حدود جميع حلول النموذج قد تم تنفيذها. تمت مناقشة الوجود وكذلك تحليل الأستقرار لجميع احتمالات نقاط الأتزان الموجبة. كذلك في ظل تأخير زمني معين أثبتنا أن نموذجنا. قد أظهر تشعب هوبف دون الحرج. وعلاوة على ذلك فاننا قد درسنا المحاكاة العددية للنموذج لتأكيد اكتشافنا التحليلي.In this paper, the dynamics of scavenger species  in a web food model  incorporating time delay and  prey harvesting  is formulated mathematically. Boundednes of all  solutions of the model carried out. The existence as well as stability analysis of all possible positive equilibrium points are discussed. Also, we proved that under certain time delay, our model exhibits a subcritical Hopfbifurcation. Furthermore, to confirm our analytical finding, we studied numerical simulation for the model

The Ecology and Natural History of the Northern Leopard Frog, Rana pipiens Schreber, in West Virginia

The purpose of this study was to gather ecological and life history data for the Northern Leopard Frog, Rana pipiens Schreber, in West Virginia. In Chapter 1, natural history data, such as morphometrics (larval and adult), dorsal coloration, and emergence time were recorded. In Chapter 2, it was discovered that Aeromonas hydrophila and Pseudomonas ssp. skin infections affecting R. pipiens could be identified using BIOLOG analysis. The scope of Chapter 3 was to analyze habitat partitioning between 3 sympatric anurans (R. pipiens, R. catesbeiana, and R. clamitans melanota). The following habitat partitioning gradient was discovered. Rana pipiens was the most terrestrial species and R. catesbeiana was the most aquatic species. Rana c. melanota inhabited the transition zone between the terrestrial and aquatic habitats. The purpose of Chapter 4 was to analyze the diet composition of R. pipiens. It was discovered that Coleopterans, Annelids, and Hymenopterans comprised 22.9%, 17.3% and 11.9% of the diet, respectively

Population dynamics of the rat tapeworm, 'Hymenolepis Diminuta'

Imperial Users onl