ultrastrucural study of bee louse varroa destructor anderson &trueman 2000 … ·...

Danish journal of Medical and Biology Sciences, July, 2015, Pages: 42-57

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Ultrastrucural study of bee louse Varroa destructor Anderson &Trueman 2000 (Acari: Varroidae) with resistance models from Apis mellifera L.

Khalaf Nour Abd el-Wahed Ammar

Zoology Dept., Faculty of Science; South Valley University, Qena, Egypt

A r t i c l e I n f o r m a t i o n A b s t r a c t

Article history: Received: 18 June Received in revised form: 27 June Accepted: 28 June Available online: July Keywords: mites Acari Apis mellifera Egyptian race Varroidae-sem Corresponding Author: Khalaf Nour Abd el-Wahed Ammar [email protected]

© 2015 Danish Journals All rights reserved

The ectoparasitic mite Varroa destructor is the most dangerous of honeybee Egyptian race Apis mellifera L. parasites, as it causes many losses in apiculture worldwide. Adult female mites were flattened and had a dome-shaped dorsal shield. By SEM revealed that the flat ventral surface was composed of a series of plates. There are 5 rows of small, chemorecptors papillae posterior to the genito – ventroanal shield, a unique respiratory structure (peritreme) was located laterally above Coxa III. Peritreme chitinized elongated area surrounding stigma opening, provider lid looks like the rose and curly with a thick inner membrane which has numerous teeth like projections. Legs of this mite appeared to be modified for ectoparasitism and each was tipped by one of distal empodium. Mouthparts appeared to be well modified for its diet of bee hemolymph, it has a powerful pedipalp used for host attachment and the posterior have a caruncle while the first has a concave sucker, and apparently these are unique to this species. High magnification revealed that different types of setae distributed on the body the mechano receptor pedipalp short and long anal setae and dorsal shield sensory simple setae. This work was conducted careful characterization Varroa destructor infesting local bees; resistance of honeybee against Varroa mites found in the debris of honey bee colonies.

To Cite This Article: Khalaf Nour Abd el-Wahed Ammar, , Zoology Dept., Faculty of Science; South Valley University, Qena, Egypt Danish journal of Medical and Biology Sciences,42-57, 2015

Introduction Honey bees, Apis mellifera L. are considered the wings of agriculture due to their important role in crop pollination and hive products (honey, propolis, royal jelly, wax, bee venom, pollen, queens and bee packages). However, honey bees are reliable to be attacked by many insect pests, birds, mites and diseases inducing severe damages. The Varroa mite has many deleterious impacts on honey bee colonies. These impacts are well known and include, the weakness of honey bees by feeding on the haemolymph (Rosenkranz et al. 2010), transportation of viruses to host bees including Kashmir bee virus (Chen et al. 2004), suppresses the immunity of honey bees (Shen et al. 2005), impact bee wing Shape (Cakmak et al. 2011) and can impact virgin queen s acceptance and mating success (Rateb et al. 2010). Varroa mite is obligate parasite throughout its life cycle; it does not have a free-living stage and is always found in close association with its host. This external parasite feeds on the hemolymph of adult bees, larvae, and pupae. Heavy parasitism results in heavy bee mortality and subsequent weakening of the colony and can lead to colony death. The genus Varroa includes at least four species. Varroa jacobsoni was described from Java in 1904 as a parasite of Apis cerana and has a wide distribution on this bee throughout Asia and on A. nigrocincta in Indonesia. Varroa underwoodi was first described from A. cerana in Nepal in 1987. Varroa rindereri was described from Apis koschevnikovi in Borneo in 1996. Varroa destructor was described from both A. cerana (its original host) and A. mellifera (a new host) in 2000; prior to its recognition, V. destructor was mistakenly lumped together with V. jacobsoni and most literature referring to V. jacobsoni prior to 2000 probably refers to the species now known as V. destructor. (Anderson and Trueman 2000; Rosenkranz et al. 2010) Oldroyd (1999) discusses aspects of the evolution of the varroa mite-honeybee association and notes that A. mellifera is the only Apis species believed to have escaped natural parasitism.


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Varroa mites were first introduced to the western honey bee (Apis mellifera) about 70 years ago after bringing A. mellifera to the native range of the eastern honey bee (Apis cerana). Varroa mites (Varroa jacobsoni) in eastern honey bee colonies cause little damage. But after switching hosts and being dispersed across the world through natural and commercial transportation of honey bee colonies, Varroa has became a major western honey bee pest since the 1980’s. Varroa destructor are now the most serious pest of western honey bee colonies and one of the primary causes of honey bee decline (Dietemann et al. 2012). A western honey bee colony with Varroa, that is not treated to kill the pest, will likely die within one to three years (Korpela et al. 1992; Fries et al. 2006). Varroa destructor was, until recently, thought to be a closely related mite species called Varroa jacobsoni . Both species parasitize the Asian honey bee, Apis cerana. However, the species originally described as V. jacobsoni by Oudemans in 1904 is not the same species that also attacks Apis mellifera. The jump to mellifera probably first took place in the Philippines in the early 1960s where imported Apis mellifera came into close contact with infected Apis cerana. Up until 2000, scientists had not identified Varroa destructor as a separate species. This late identification in 2000 by Anderson and Trueman corrected some previous confusion and mislabeling in the scientific literature. Nowadays the ectoparasitic mite Varroa destructor (Anderson and Trueman, 2000), formally named Varroa jacobsoni (Wongsiri et al., 1996; Oldroyd and Wongsiri, 2006). Cook et al. (2007) estimated that preventing Varroa destructor from establishing in Australia over the next 30 years would avoid costs of between 16 million and 40 million dollars (U.S.) per year. Since the contact between varroa and Apis mellifera, serious problems have been experienced worldwide in apiculture. The effects of the parasite on honey bees range from weakening to death of parasitized colonies, with the intensity of the problem being directly related to the level of infestation (De Jong, 1990). Climate and Apis mellifera race were found to be important factors that affect the development of this parasite (De Jong et al., 1984; Moretto et al., 1991; De Jong and Soares, 1997). the varroa mites are an agent which transmits several pathogenic microorganisms to apis mellifera L, it has been demonstrated that varroa can transmit both sacboord virus (SBV) Bailly 1991 and acute paralysis virus (APV) (Ball,1985 ,Ball and Allen,1988) by inoculating virus particles into the haemolymph of honey bees (Alippi et al.1995). It now is believed that varroa mites can transmit multiple viruses to their hosts and that these viruses, not the varroa mites themselves, may cause the majority of the damage that bees experience while hosting the mites (Webster and Delaplane 2001). V. destructor is a vector for various honey bee viruses. So far, about 18 different viruses have been isolated from honey bees and for Kashmir Bee Virus (KBV), Sacbrood Virus, Acute Bee Paralysis Virus (ABPV), Israel Acute Paralysis Virus (IAPV) and Deformed Wing Virus (DWV), it has been proven that they can be vectored by V. destructor. The ectoparasitic mite V. destructor is currently a worldwide and serious threat to beekeeping (De Jon g et al., 1982). One of the serious problems caused by varroa is the transmission of viruses to honey bees which cause deadly diseases (Kevan et al. 2006), such as bees growing with defective wings and high bee mortality rate (Rosen kranz et al., 2010). This parasitic mite cause's weight loss, malformation, a shortened life span in honey bees (De Jon g et al., 1982, (De Jong, 1990)., Kovac, Crailsheim, 1988). The existence of a correlation between the infestation with the mite and either viral dispersion, physical deficiencies or shortening of life expectancy (Bailey an d Ball 1991, Khalil, 1992). Several researches have demonstrated distinct levels of virulence of the mite and increased colony mortality rates due to its infestation ; Yousef et al,2014 report the mite's effects on hypopharyngeal glands(the main secretory products are royal jelly components, as well as


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other substances such as α -glucosidase ) of A. mellifera , and changes in the morphometrical Measurements of HPGs aciniat different ages of honey bee workers clear that the mean acinal surface area increased gradually from emergence until it reached the maximal area on the 12 day of worker age. Among the different types of Apis mellifera, Africanized bees show great resistance to varroa compared to bees of European races. One of the factors that is thought to be involved in this resistance is the fact that the reproductive ability of varroa females is known to be lower in Africanized bees than in European bees (Camazine, 1986; Moretto, 1988). Peng et al. (1987) observed that A. cerana has a strong defense mechanism against Varroa jacobsoni. When A. cerana workers were artificially infested with varroa females, 99% succeeded in ridding themselves of the parasite by performing body movements that expelled or removed it from their body. It was also observed that many of the mites that left the host worker were killed by the infested worker itself or its fellow workers. Defense mechanisms against the mite similar to those of Apis cerana have been identified in Africanized bees. Moretto et al. (1993) observed that 40% of Africanized bees rid themselves of the parasite when workers of 20 Africanized bee colonies were artificially infested. Correa-Marques (1996), in a study of mites collected from the bottom of Africanized bee colonies, noted the occurrence of mutilations in several parts of their body, indicating possible attacks by the workers. Recently, Anderson and Trueman (2000), after studying mtDNA Co-I gene sequences and morphological characters of many populations of V. jacobsoni from different parts of the world, considered it to be a species complex and split it into two species. Varroa jacobsoni s.s. Infests Apis cerana F. in the Malaysia-Indonesia region. Varroa destructor Anderson & Trueman, 2000 infests its natural host A. cerana on mainland Asia and also A. mellifera L. worldwide. The ectoparasitic mite,V.destructour L, is the most destructive pest of honey bees in Egyptian race Apis.mellifera because of the risks and disadvantages of using chemical treatments in mite infested colonies Thompson et al., 2003 . It is important to determine if honey bees have any heritable defense mechanisms against the mite which may be readily incorporated into breeding programs. Breeding for Varroa -resistant honey bees became the primary goal for a number of research groups around the world. Buchler et al, 2010 consider resistance in honey bees as the ability of a bee population to survive without therapeutic treatments in a given environment and management system. Resistance is therefore not an absolute trait, but rather has to b e viewed as the result of successful interactions in a specific environment. High levels of resistance occur in some untreated European bee populations. However, as most colonies are under strong influence of modern beekeeping management, which includes regular use o f acaricides and requeening with selected stock, Varroa resistance should be implemented on a broader scale in selective breeding activities. This implementation depends on having suitable test characters and an effective coordination o f breeding programs. Breeding for resistance t o Varroa destructor in North America provides the long-term solution to the economic troubles the mite brings. Rinderer et al. (2010) reports the development of two breeding successes that have produced honey bees of commercial quality that do not require pesticide treatment to control Varroa, high lights other traits that could be combined to increase resistance and examines the potential uses of marker-assisted selection (MAS) for breeding for Varroa resistance.


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Material and methods The mite Varroa , an important ectoparasite of the Egyptian honey bee , Apis mellifera lamarkii, in the present study, adult females were collected from infested Apis mellifera in Sohag during autumn and winter of 2014 and were examined by SEM. Bee colonies were infested heavily; up to 6 mites per host were recorded. The mite inserts itself between the abdominal sclera in adult bees where it penetrates the intersegmental membranes in order to ingest haemolymph. Sometimes it can also be found between the head and thorax. Mites collected from infected bees with the aid of a small forceps, were Stored in 70% Ethyl alcohol and , washed in 100% acetone followed by 100% Ethyl alcohol, and mounted directly into Hoyer’s mounting medium on glass slides . For Scanning Electron Microscope studies, the collected mites was washed with saline 0.9% fixed in 2.5% glutaraldhyde (ph.7.4) at 4 c. Specimens were washed three times in phosphate butter and post fixed in 1 % osmium tetroxide in 0% M phosphate buffer and dehydhrated was performed in two changes of absolute Ethyl alcohol. Specimens were then mounted on stubs. With double adhesive tape, coated with gold using spimodule vac / sputter coater. The samples were examined with a high resolution scanning Electron microscope (Joel, 200 Ex II) out the central laboratory, faculty of science, south valley university. Varroa mites also may be collected by the examination of the debris generated by bees themselves. An insert covered with a screen mesh is placed on the floor of the hive. Unless this insert is covered with such gauze, or smeared with grease, the bees will dispose of the mites outside the hive, a number of mites may be observed on the floor insert. Large amounts of debris can be examined in the laboratory using a flotation procedure. Result (Fig.1; Plates 1& 2&3): General characters:According to Evans (1992), the Acari form a large group of Arachnida characterized by their small size and the birefringence of body and leg setae, in which the main distinguishing characteristic is the position of the stigmata behind coxae III. The mite Varroa destructor (formerly Varroa jacobsoni) is a parasite of adult bees and their brood, visible to the naked eye. It penetrates the intersegmental skin between the abdominal sclera of adult bees to ingest haemolymph (blood). It can sometimes be found between the head and thorax. Adult female mites were flattened and had a dome-shaped dorsal shield. The flat ventral surface was composed of a series of plates. A unique respiratory structure was found. Legs of this mite appeared to be modified for ectoparasitism and each was tipped by one of distal empodia. Mouthparts appeared to be well modified for its diet of bee hemolymph , and apparently these are unique to this species. Varroa mites exhibit distinct sexual dimorphism. The body of both sexes is divided into two distinct parts - idiosoma and gnathosoma. The present female mites have flattened ellipsoidal idiosoma with greater width than length (measuring 1-1.8 mm long and 1.5-2mm wide). The adult female mites are reddish-brown to dark brown in color and oval in shape, the mite gnathosoma consists of mouthparts with two movable, sensory pedipalps (palpus) and two chelicerae, and has eight legs. The mite protrudes its gnathosoma vertically to the body axis. With the two chelicerae, each with two small teeth and moving like saw – blades. The entire surface of the body present filamentous, cluster of sensilla spines directed backwards and forwards is different in size and also in shape. The dorsal side decorated with network reticulations and carries large number of short simple setae; highly sclerotized; dorsoventrally flattened and a had dome–shaped dorsal shield. Tectum is absent. The opisthonotal margin of the dorsal side carries 22 pairs of thick hook –


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like spine. Ventrally, tritosternum is well developed and consists of a two long finely feathered lacinia sets on a trapizoidal base. The hypostome carries three pairs of seeming straight line and lacking the hypognathal denticles. The sternal shield is arch-like .The genito – ventro anal shield covered with network reticulations, being narrow anteriorly, wide medially and pointed posteriorly. It bears large number of short simple setae, a pair of simple para – anal setae, a single post – anal seta. The genital aperture is circular in shape and situated on the anterior part of the genito – ventro-anal shield while the anal area is triangular in shape and has 2 thin serrated valves in addition, five rows of small, dentate papilla posterior to the genito – ventro anal shield. Legs I – IV have seven segments (including pretarsus), each of which carries a large number of different sizes and long simple setae. Legs II – IV fold into deep pits (foveolae pedales. The length of legs from PI – PIV measure about 0.4 – 0.6 mm respectively. By S.E.M. revealed that the adult female were flattened and had a dome-shaped dorsal shield. The flat ventral surface was composed of a series of plates. The stigma of the adult female mite is located laterally above Coxa III and is enclosed with in a peritremated shield which has a slit at the end. Study by SEM approved that the respiratory apparatus of the mite of bees appears typically tracheal, as those of the insect and other Arachnida. Peritreme chitinized elongated area surrounding stigma opening . The peritreme is provider lid looks like the rose and curly with a thick inner membrane which has numerous teeth like projections. The pretarsus of the 3 pairs of the posterior Legs II – IV consists of two main parts a cuticular basal stalk and an extrudable membranous amblacral pad (The caruncle). While the first pair of legs, the pretarsus becomes concave sucker. The caruncle when fully extruded and expanded becomes a bilobed sucker and when deflated the entire caruncle is retracted into the basal stalk. The basal stalk of the pretarsus with the sucker fully retracted into it resembles an inverted cone with its narrow portion attached to the apex of the tarsus. High magnification revealed that all five segments of the pedipalp bear mechano receptor setae with a basal socket; p – l carries one simple seta, P – 2 carries a pair of simple setae, P – 3 (palpal tibia) bears five simple setae, P – 5 (palpal tarsus) carries nine pairs of simple setae, single solenodion and a thick palpal a potele which has two unequal tines at the base of palpal tarsus. Ultra structural study reveals that the outer surface of the body have cavities Walt possible help a function directorial, small spine cover the dorsal surfaces of the body .Scattered small sessile papillae are found in genitor-ventral shield. Cutaneous sense organs or sensella are the most widely distributed on all parts of the body and appendages. all setae are named according to their position on the body (anal, postpalpal, palpal, post-hypostomal, tarsus, coxae, basis chelicerae sense organs are temperature receptors the seta is a hollow cuticular process with comparatively thick walls, they are movable, articulated to the cuticule by a thin membranous ring around the base. Found on the outside of pedipalps a pair of stilettos (S) or the knife used by the mite instilled in the body of the bee. The present study showed the existence of forms and patterns varied resistance models against varroa mites is the result honey bee hygienic behavior are as follows (Plate 3) Full dump in the ventral side Completely cracking in the legs Completely cracking in the mouth parts Cracking in the dorsal side Crackdown in the dorsal side. Distorted abdomens, missing and stubby legs


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DISCUSSION: The parasitic mite (Acari: Mesostigmata: Varroidae) has been known as a major pest of honeybees around the world (Sammataro et al. 2000). Varroa mites attack honey bee colonies as an external parasite of adult and developing bees, by feeding on hemolymph (fluid of the circulatory system similar to blood), spreading disease, and reducing their lifespan. Varroa destructor (= jacobsoni ) is one of the most serious pests of the honey bee, Apis mellifera (Hymenoptera: Apidae), and its introduction into new countries is causing much concern to beekeepers throughout the world. Although the varroa complex includes multiple species, V. destructor is the species responsible for the vast majority of the damage attributed to mites from this genus. Until 2000, it was believed that V. jacobsoni Oudemans was the mite responsible for widespread honey bee colony losses. However, taxonomic work published in 2000 (Anderson and Trueman 2000) indicated that a previously-unidentified species of varroa (V. destructor) was responsible for the damage, while V. jacobsoni was shown to be only moderately harmful to western honey bees. Varroa destructor was, until recently, thought to be a closely related mite species called Varroa jacobsoni . Both species parasitize the Asian honey bee, Apis cerana. However, the species originally described as V. jacobsoni by Anthonie Cornelis Oudemans in 1904 is not the same species that also attacks Apis mellifera. The jump to mellifera probably first took place in the Philippines in the early 1960s where imported Apis mellifera came into close contact with infected Apis cerana. Up until 2000, scientists had not identified Varroa destructor as a separate species. This late identification in 2000 by Anderson and Trueman corrected some previous confusion and mislabeling in the scientific literature. Anderson and Trueman (2000) identified two haplotypes of V. destructor that infest A. cerana in Asia and have become pests of A. mellifera worldwide. Anatomically, female varroa mites are well-adapted bee parasites. Their curved, flattened shapes allow them to fit between the abdominal segments and are held there by the shape and arrangement of ventral setae. This protects them from the bee's normal cleaning habits. Furthermore, they have claws that allow them to grasp the bee and ventral setae that allow them to remain attached to the bee. Additionally, the cuticle is highly-sclerotized, thus occasionally protecting it from bee aggression. Females use teeth on third movable digits and stilettos (S) to open the wound on the host. The females attach to the adult bee between the abdominal segments or between body regions (head-thorax-abdomen), making them difficult to detect. These are also places from which they can easily feed on the bees' hemolymph. The adult bee suffers not only the loss of blood but may be subjected to microbial invasion, leading to a reduced life expectancy. The flattened shape of the female’s body makes it easy for the mite to hold on to a bee and move easily into the cells of developing bee brood. When on adult bees, female varroa are found mainly on the top of the bee’s thorax at the point where the wings attach, between the head and the thorax, between the thorax and the abdomen, or between overlapping segments of the abdomen. These are places where the mites can easily use their piercing mouthparts to penetrate the exoskeleton of their host and gain access to the bee’s hemolymph (blood). These are also places where mites are less likely to be removed by the bee’s grooming. Bautz and Coggins 1992 showed that the legs were tipped by one of 2 types of distal empodia. Another authors, Liu & Peng in 1990 concluded that the pretarsus consists of a bilobed sucker. While Ramirez & Malavasi 1991 suggested that the ambulacrum is not a sucker or a sticky pad but a structure with protractile claw – like sclerites as crochets to grasp the hairs of the bee and allow the mites to move rapidly on the adult bees and other substrata. In the present study as mentioned before, showed that the first leg. Bears a concave sucker and the posterior three carries the caruncle .


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Liu (1982) observed the dorsal shield is covered with numerous branched setae, and has a row of thick, short and curved setae at its lateral edges. While in the present work the dorsal shield is covered with pilose not branched setae, and has 22 pair of thick, strong curved setae at its lateral edges. Moreover there are 5 rows of small may be chemoreceptors papillae posterior to the Anus. Two blunt-tipped sensilla arising from the distal end of the tibia, five stout setae on the tarsus. The morphology of the mouth parts of Varroa mite and the mechanism of ingestion were examined by SEM and observation of living mite. For penetration of the host integument, the mite protrudes its gnathosoma vertical to the body axis. With the two chelicerae, each with two small teeth and moving like saw – blades, a pair of stilettos or the knife, the mite tears a wound in the bee’s integument. The out flowing blood is then sucked up by the muscular pharynx in the hypostoma. The same finding was record by Gelbe et al 1987. All 5 segments of the pedipalp bear mechanorceptor setae with a basal socket. The same finding recorded by Milani & Ritter (1991); But in the present study; the number and sizes are differing from them. By means of SEM studies, Puerta et al, (1990) found spores of Ascosphaera apis, Olive and Spiltoir and Aspergillus flavus, on the cuticle of adult female varroa. The mite is also one of the vectors of Hafnia aluei Moller, which causes septicemia (Strick and Madel, 1988) and of several other bacteria (Glinski and Jarosz, 1992). Also, Alippi, 1992 his studies have shown that V. jacobsoni carries viable spores of Paenibacillus larvae.in the present specimen's spores and viruses are present as clusters in the dorsal surface. Evidence suggests that Varroa and their vectored viruses affect the immune response of honey bees, making them more susceptible to disease agents (Yang and Cox-Foster 2005). The effects of the parasite on honey bees range from weakening to death of parasitized colonies, with the intensity of the problem being directly related to the level of infestation (De Jong, 1990). Among the different types of Apis mellifera, Africanized bees show great resistance to varroa compared to bees of European races. One of the factors that is thought to be involved in this resistance is the fact that the reproductive ability of varroa females is known to be lower in Africanized bees than in European bees (Camazine, 1986; Moretto, 1988). Ruttner and Hanel, (1992) mentioned that by investigating freshly killed mites it was concluded that the damage was caused by the mandibles of worker bees; SEM photographs of the mandibles indicate that they act like sharp scissors . Peng et al. (1987) observed that A. cerana has a strong defense mechanism against Varroa jacobsoni. Defense mechanisms against the mite similar to those of Apis cerana have been identified in Africanized bees. Moretto et al. (1993) observed that 40% of Africanized bees rid themselves of the parasite when workers of 20 Africanized bee colonies were artificially infested. Correa-Marques (1996), in a study of mites collected from the bottom of Africanized bee colonies, noted the occurrence of mutilations in several parts of their body, indicating possible attacks by the workers. A balanced host-parasite relationship has evolved between varroa and its natural host. A.cerana has two behavioral defenses which help maintain the numbers of mites within tolerable limits. These defenses are grooming and removal (hygienic) behaviors. In grooming, adult bees detect and remove phoretic mites from themselves (auto-grooming) or from nest mates (allogrooming) Peng et al, 1987a.in the process, the legs of the mites may be cut off or the cuticle of the idiosoma may be damaged by the bees mandibles, causing the damaged mite to fall in the bottom of the colony (Ruttner and Hanell, 1992). Successful grooming of mites has been demonstrated in A.cerana (Peng et al 1987a;Buchler et al ,1992;Fries et al,1996).A.mellifera of European origin also exhibits grooming behavior but to


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a lesser extent than A,cerana( Peng et al 1987a;Buchler et al ,1992; Buchler ,1994;Fries et al,1996), This is consistent with what is recorded in the present work. Removal behavior involves the ability of some bees to detect, uncap, and remove infested pupae from the cells. In addition, the immature mites are killed which decreased the average number of off spring per mother mite (Rath and Drescher, 1990; Fries et al, 1994). It is interesting to note, a heightened form of hygienic behavior called 'varroa sensitive hygiene' (VSH) has been found in some bees. VSH bees are able to detect varroa in capped cells and remove only those varroa that are reproducing. The ability to remove brood infested with Varroa has been bred to high levels in A. mellifera colonies bred for VSH (Harbo and Harris, 2005; Harris, 2008). VSH is more pronounced in infested worker brood than in drone brood suggesting that increased mite infestation may occur in VSH colonies when drone brood is abundant (Harris, 2008). As VSH bees uncap and remove infested brood, freed adult female mites usually transfer onto the bees removing the brood (Aumeier and Rosenkranz, 2001) but may eventually become free on the combs and exposed to attack by bees. Thakur et al. (1997) documented that honey bees can detect, grab and bite free moving mites. The mites may also become phoretic and exposed to grooming. Hence, VSH may be a basic mechanism which can enhance other traits such as nestmate grooming and an increased phoretic period (Ibrahim et al., 2007). Honey bee genotypes differ in their ability to resist the Varroa mite and this ability is related to the intensity of grooming behavior in these genotypes (Guzman-Novoa et al. 2012). An example of these tolerance genotypes is the African honey bees which have more tolerance ability than European honey bee races (Moretto and de Mello 1999). Honey bee races could be resistance to Varroa mite through grooming behavior, Varroa Sensitive Hygiene (Villa et al. 2009) or hygienic behavior (e.g. Ibrahim and Spivak (2006). These behaviors could be impacted by some factors, including temperature and humidity (Tahmasbi 2009). On the contrary, Bak et al. (2013) found no impact of the honey bee subspecies on Varroa population growth. NajiKhoei et al. (2011) found no relationship between colony strength as the number of workers within colonies and resistance against Varroa. Obtaining a resistance bee race to Varroa mite is a good option towards sustainable mite control. Conclusion. Honey bee colonies that survive infestations of this Varroa haplotype have one or more behavioral or physiological traits. Honey bees clean themselves (autogroom-ing) and nestmates (allogrooming) (Haydak, 1945). Grooming may injure or kill Varroa mites (Ruttner and Haenel, 1992), or it may cause mites to either move to other parts o f the autogroomer’s body, transfer to a new host or be removed from the bee’s body without causing visible injury (Büchler et al., 1992). Grooming is rarely observed directly. However, variation among honey bee stocks in grooming has been inferred from the proportion o f mites that drop to hive floors that are damaged, apparently from bees’ mandibles (Boecking and Spivak, 1999; Fries et al., 1996; Rinderer et al., 2001a; Arechavaleta-Velasco and Guzman-Novoa, 2001). They may also indicate grooming and actually be injured or debilitated (Thakur et al., 1997). Alternately, they may be healthy, fallen owing to hot weather (Webster et al., 2000). Injuries to mites may result from: (a) grooming, (b) removal of dead mites (Rosenkranz et al., 1997; Bienefeld et al., 1999), or (c) predation by wax moth larvae and ants (Szabo and Walker, 1995). Davis (2009) asserted that indentation on the mites’ idiosoma is not damage caused by bees but is acquired during mite development. However, pieces missing from the idiosoma and missing legs cannot be attributed to normal mite development. There are two genetic lines that breeders have been working on in the U.S. One line is called the "leg-biters"--as its name would suggest, these bees are prone to attack varroa, typically biting off the legs of the mites. The other genetic line exhibits what I think is called varroa-


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sensitive hygiene (VSH). In these bees, the workers can detect developing larvae and pupae that are infested with varroa, and then the workers remove these larvae and pupae before the varroa mites can complete their life cycle on them.

Fig.1: Camera Lucida drawing whole mount adult Varroa destructor female: Note The flat ventral surface was composed of a series of plates. The body is divided into two distinct parts - idiosoma and gnathosoma , mouthparts with two movable, sensory pedipalps (palpus) and two chelicerae ( C ), and has eight legs (PI-PIV).The genital aperture (opening) is circular in shape and situated on the anterior part of the genito – ventro (gvp) plate while the anal area (a) is triangular in shape and has 2 thin serrated valves in addition, five rows of small, spine papilla posterior to anal shield.,(e) empodium., (t) tritosternum., (P) peritrem. Margin of the dorsal side carries 22 pairs of thick hook – like spine.


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Plate 1: Scanning electron micrographs of female V.destructor showing: Fig.b: ventral view of adult female, showing sternal, genitoventral anal plates (shields) including the anal plate at the posterior end, small setae around the anus which lying anterior The opisthonotal margin of the dorsal side carries 22 pairs of thick hook – like spine., Fig.a: dorsal view, gnathosoma protrudes vertically to the body axis magnified dorsal shield showing it's pilose Fig.e: magnified gnathosoma showing the two chelicerae, each with 2 small teeth and moving like saw-blades, a pair of stilettos(S). Fig.f: the mouthparts of the movable digit of the chelicerae appear as a long structure, coiled like a spring and lying between the pedipalps. Showing tritosternum short chelicerae and hypostome .


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Plate 2: Scanning electron micrographs of female V.destructor showing: Fig. a: a lateral view showing the dorsal plate, peritreme, stigma (spiracle) and the sites of attachment of the legs located laterally above Coxa III.,Fig.b: magnified a peritremated shield which has a slite at the end; The peritreme is provider lid looks like the rose and curly with a thick inner membrane which has numerous teeth like projections., Fig. c: magnified genitor-ventral shield and genital opening, scattered small sessile papillae are found.., Fig. d : posterior end showing 5 rows of papillae just post anus.. Fig.e: magnified anterior legs with concave lobed sucker (caruncle) showing its reasonable, Fig. f: Magnified of Cox seta notes that sitting in socket with a basal socket. Fig. g: the lateral sides showing small, strong and curved spines, different types of setae.


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Plate 3: Scanning electron micrographs showing resistance models: (Fig.c) full dump in the ventral side and Completely cracking in the legs; (Fig.f) Completely cracking in the mouth parts; (Fig.a&b&g) Partially cracking in the dorsal side; (Fig.a) Crackdown in the dorsal side showing spores on the dorsal shield surface , on the idiosome seta., (Fig.c&e) Distorted abdomens, missing and stubby legs.


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