BINDURA UNIVERSITY OF SCIENCE EDUCATION AN ASSESSMENT OF INFESTATION BY PARASITIC WATER MITES ON DRAGONFLIES AT A MARSH ALONG MWENJE DAM, MAZOWE DISTRICT, ZIMBABWE BY CHARASHIKA ZAKARIA B1129476 SUPERVISOR: DR. C. PHIRI A DISSERTATION SUBMITTED TO BINDURA UNIVERSITY OF SCIENCE EDUCATION, IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE BACHELOR OF SCIENCE EDUCATION HONOURS DEGREE (BIOLOGY). JUNE 2014 1 ABSTRACT This study was done to determine the infestation levels by water mites (Hydrachnidae) on dragonflies (Anisoptera) that are found at a marsh along Mwenje Dam in Mazowe District, Zimbabwe. A total of 111 dragonflies comprising Aeshnidae (31.5%) and Libellulidae (68.5%) were collected over a period of four months (January to April 2014). The total length and gender of each individual was recorded, as well as number and attachment sites of the parasitic mites. Overall, a total of 28.8% insects were infected. Among the Aeshnidae, the proportion of males that were infected were significantly greater than the females (Chi- square, χ2, p < 0.05). However, for Libellulidae there was no significant difference in the proportions of infected males and females (Chi-square, χ2, p > 0.05). A significantly greater proportion of Aeshnidae was parasitized as compared to Libellulidae (Chi-square, χ2, p < 0.05). For both taxa, the parasites were attached on either the thorax or abdomen, with no significant difference in the number of parasites between the two attachment sites (ANOVA, p > 0.05). 2 ACKNOWLEDGEMENTS I would like to thank my supervisors Dr Phiri and Mr Munosiyei for guidance, encouragement and support during the research period especially when hope was oblique. The efforts of all the staff members in the Department of Biological Sciences, Bindura University of Science Education cannot go unnoticed and uncommented for, especially for the insight on the basics of conducting and writing the dissertation. Dr Manyanga (Chairman of the department) and Ms Bobo (project co-ordinator), your efforts are highly acknowledged. I also thank Mr. Mutune (The Head Gweshe High School) for all his supportive efforts. Above all, I would like to thank he who holds my future and watching us from a distance, God the Almighty. 3 DEDICATION This project is dedicated to my ever loving wife (Makunde Moline) who encouraged me throughout the course of my work as well as overwhelmingly supporting me financially and my dedication also goes to my beloved kids, Tinevimbo, Tinatsei and Makanaka who inspired me to do this work. Dedication also goes to my God given mother and my late father Mr R. Charashika. 4 CHAPTER 1 1.0 INTRODUCTION The Anisoptera has 5 living families (William and Feltmate 1992).The most common species are found in the equatorial and sub-tropical regions and these are Libellula lydia and Orthetrum glaucum . Dragonflies are vigorous predators especially of mosquitoes; they undergo incomplete metamorphosis during their life cycle (Forbes, 1991). They are often seen flying back and forth or dating about inconsistently especially along shores and over waters of marshes, ponds, rivers, lakes and swampy areas from early morning until late evening (Forbes, 1991). Though the dragonflies are voracious predators but they are also subject to predation by birds, fish, giant water bugs in the order Hemiptera and predacious diving beetles in the order Coleoptera (Corbet, 1962). They are also parasitized by water mites that tend to densely populate stagnant waters. These water mites especially those in the sub-order Hydrachnidae drain or suck considerable amounts of body fluids from their hosts (Abro, 1990). The water mites have the tendency of reducing lifetime and reproductive success of their host in a variety of ways (McGavin, 2001). When the Odonates emerge from the water to become an adult, the mites crawl from the exuvia (shed nymphal skin) onto the emerged adult on the exoskeleton whilst the skin is still soft and easy to pierce. Attack mostly occurs on the ventral areas of the thorax and abdomen of the dragon flies (nwdragonflier.blogspot.com/2012/01 online; Nagel et al 2011, retrieved on 12/01/14). 1.1 JUSTIFICATION Stagnant waters tend to accommodate most of the aquatic vertebrates and invertebrates. Among the aquatic invertebrates are the water mites which are the parasites of dragonflies. The parasitic effect of these water mites have negative impacts on the life if their hosts. However, their infestation levels seem to differ basing the ecosystem or geographical range. Silsby (2001) and von Ellenrieder (2003) posited that dragonflies and their parasites are found worldwide except in polar regions and the greatest diversity of dragonflies are found in tropical areas. Because, dragonflies spend majority of their time near water, laying their eggs in or close water and their immature nymphs are aquatic, make them prone to predation by the parasitic water mites (McGavin, 2001). 5 This project was embarking on the assessment of infestation levels of parasitic water mites (Arrenurus) on the dragonflies (Anisoptera), where catching of dragonflies and enumeration of water mites on infected fly was carefully done. The results from this assessment can then be used to make necessary adjustments on the levels of dragonfly infestation by water mites. The project will also in a way enlighten the people in Chiweshe on the use of a dragon fly as a biological control of pests /insects like mosquitoes , make people appreciate the main attraction for human aesthetics in dragonflies and to so extend signal to ecosystem quality (Loeng and Tay, 2009) 1.2 PROBLEM STATEMENT Dragonflies in the sub-order Anisoptera are conspicuous and bright coloured insects that are predators of a number of insects. Thus, they can be used to reduce the population of mosquitoes thereby reducing malaria cases. However, a number of parasites like trematodes parasitic wasps biting gnats in the family Ceratopogonidae (Borror, et-al 1989) affect these Odonates. These parasites especially the water mites (Arrenus spp) affect the life cycle of the dragonflies in a number of ways. Some researchers have often analysed the parasitic effects of these water mites citing the idea of reducing mating success, poor flight among others (Dunn, 1996; McGavin, 2001). 1.3 AIM OF THE STUDY The main aim of this study was to assess the infestation levels of water mites (Hydrachnidae) on the dragonflies. 1.4 OBJECTIVES OF THE STUDY The objectives of the research are: • To determine the prevalence of infestation of dragon by water mites. • To compare the number of parasitized dragonflies by water mites with regards to gender. • To assess the differences in proportions of insects parasitized amongst the dragon fly families. • To determine whether there are differences in infestation levels among attachment sites 6 1.5 RESEARCH QUESTIONS • Which sex of anisoptera is parasitized most by water mites? • Which parts on the adult dragonfly often carry the water mites? • What is the mean intensity of water mites on various families of dragonflies from the collected sample from the marsh? 7 CHAPTER 2 2.0 LITERATURE REVIEW 2.1 INTRODUCTION TO DRAGONFLIES 2.2 CLASSIFICATION OF DRAGON FLIES The organisms are in the kingdom Animalia and phylum Arthropoda. They belong to class Insecta and dominate the sub class Hexapoda. Dragon flies are in the order Odonata in sub order Anisoptera. They have a lot of families like the Aeshnidae, Libelullidae, Gomphidae, Corduliidae and Petaluridae to mention a few. They are further classified into genus and species where species like Anax speratus , Libellula lydia , Aeshnae cyanea and Sympetrum striolateum are found (Merrily, 2001). However the most common species in Zimbabwe include (southern hemisphere):-Trithemis kirbyi -Deplacodes lefebvrii -Sympetrum Flaveolum -Hemicordula tau 2.3 DIVERSITY OF DRAGON FLIES. Dragonflies belong to the order Odonata and sub-order Anisoptera. Currently there are eight recognized families and one hundred and twenty four (124) genera (Corbet, 1980 and McGavin 2001). There 5680 species of dragonflies however, this may change as many species are undescribed (Von Ellenrieder, 2003). Corbet, (1999) asserted that dragonflies are carnivorous insects with a lifestyle that is closely linked to freshwater aquatic habitats. Thus, they occupy fresh water habitats from small streams and seeps to large lakes and rivers, with a handful of species found in brackish and saline environment. 2.4 MORPHOLOGY AND LIFE CYCLE OF ANISOPTERA. Adult dragonflies have long slender bodies, large movable head and two pairs of membranous wings. They have large compound eyes that can see in all directions. If the compound eye is magnified each individual ommatidium appear to be hexagonal in shape (McGavin, 2001). The thorax carries transparent wings which have many veins with beautiful coloration in some species. The wings of a dragonfly are held out and perpendicular to the body when at rest and the wingspans can be about 1-8 inches (Silsby, 2001). They are the 8 fastest flying insects in the world such that they can propel themselves in all six directions (up-down-left-right-back-forward). Tillyard, (1997) claimed to have recorded a flight speed of 60 miles/hour in a rough field measurement for a Southern Giant Darner. The back wings for a dragonfly broaden near the base caudal to the connecting point at the body. Thus, their flying prowess is wonderful for them, but not so great for spectators who want to see their colours and figure out what species might they belong to (Borror, etal., 1989; McGavin, 2001). Furthermore, dragonflies have abdomen with colour spots, bands and lines with 10 segments. The dragonflies range from the arctic to the tropics and some are even found in desert regions where water is present (Hunt, 2012). Eggs are laid in water or water plants and hatch into aquatic nymph or naiads which depending on the species last for weeks to 5 years and molt several times in order to grow in size before it matures into an adult (Corbert, 1999).