2008 NORTHEASTERN NATURALIST 15(4):515–522 Ectoparasite Prevalence in Myotis lucifugus and M. septentrionalis (Chiroptera: Vespertilionidae) During Fall Migration at Hayes Cave, Nova Scotia Joseph A. Poissant1 and Hugh G. Broders1,* Abstract - Intra- and inter-specific variation in ectoparasite prevalence was characterized by collecting and identifying parasites on Myotis septentrionalis (Northern Long-eared Bat) and Myotis lucifugus (Little Brown Bat) returning to a large hibernaculum during the autumn migratory and reproductive swarming event in Nova Scotia, Canada. Unlike males, female bats in the region are colonial roosters during the summer, which may facilitate ectoparasite transfer. On bats captured at Hayes Cave, NS, there were at least four species of ectoparasites including Myodopsylla insignis (Siphonaptera: Ischnopsyllidae), Spinturnix americanus (Acarina: Spinturnicidae), Cimex adjunctus (Hemiptera: Cimicidae), and a larval Trombiculid mite, Leptotrombidium myotis (Acarina: Trombiculidae). Parasite prevalence was 30.6% and 27.8% for adult M. septentrionalis females and males, respectively, and 25.6% and 16.3% for adult female and male M. lucifugus, respectively. Myodopsylla insignis, S. americanus, C. adjunctus, and L. myotis all represent new host records on both bat species in Nova Scotia, while S. americanus and L. myotis are new species records for the province. Introduction Most mammal species are known to harbor ectoparasites, and bats are no exception (Jones and Thomas 1983, Ritzi and Whitaker 2003, Samuel et al. 2001, Weaver and Aberton 2004, Whitaker 1982). The distribution and abundance of ectoparasites is poorly understood, but they may be present at critical times during the lives of their hosts (Lucan 2006) and may affect juvenile development and reproductive potential (Bize et al. 2003, Combes 1996). In many cases, ectoparasites are monoxenous, suggesting strong evolutionary ties between parasite and host (Dick 2007). In bats, ectoparasites tend to be common within enclosed roost sites due to the large number of potential hosts and relatively stable microclimate (Dick et al. 2003, Zahn and Rupp 2004). It has been hypothesized that one reason for roost switching in cavity-roosting bats is to minimize ectoparasite load (Jones 1998, Lewis 1995, ter Hofstede and Fenton 2005, Whitaker 1998). In fact, ectoparasites may decrease the energy available for reproduction because of grooming (Moller 1993); therefore, it should be advantageous for females to limit the number of parasites. Survivorship of the young could potentially decrease due to increased energy output for grooming as well as inability of immature immune systems to suppress transmitted diseases (Christe et al. 1Department of Biology, Saint Mary’s University, 923 Robie Street, Halifax, NS B3H 3C3, Canada. *Corresponding author - hugh.broders@smu.ca. 516 Northeastern Naturalist Vol. 15, No. 4 2000). Juvenile bats with high ectoparasite loading may remain at summer roosts longer to increase fat stores for migration and hibernation (Kunz et al. 1998, Zahn and Rupp 2004). Myotis lucifugus (Little Brown Bat) (LeConte) and Myotis septentrionalis (Northern Long-eared Bat) (Trouessart) select different summer roosting sites. While M. lucifugus are increasingly found in human-made structures, M. septentrionalis is a forest-interior specialist that roosts under exfoliating bark or within tree cavities (Broders and Forbes 2004, Foster and Kurta 1999). During the course of a summer, individual M. lucifugus will often remain in one roost (Davis and Hitchcock 1965, Humphrey and Cope 1976), but individual M. septentrionalis switch roosts almost daily (Broders and Forbes 2004, Garroway and Broders 2007, Owen et al. 2002). Males of both species roost individually or in small groups (Broders and Forbes 2004, Davis and Hitchcock 1965) and, in mid- to late August, return to the area of the hibernacula before the females (Davis and Hitchcock 1965). By late August or the beginning of September, large numbers of females and their young have migrated back to the area around the hibernacula, and reproductive activity commences (Fenton 1969). While the ectoparasites of many bat species have been identified across Canada and the United States, these studies have been primarily qualitative and have not compared prevalence of parasites (i.e., percent of total number of individuals sampled that are infected) among species or between age classes and sexes. Therefore, our specific objectives were to (i) identify ectoparasites of bats in Nova Scotia, and (ii) quantitatively characterize inter- and intra-specific variation in the prevalence of those parasites during the time immediately before hibernation. We predicted that adult females and juveniles of both sexes would have higher prevalence of ectoparasites than adult males due to their summer communal roosting habits. Methods From 21 August to 31 September 2006, bats were trapped near the entrance of Hayes Cave using a harp trap (Austbat Research Equipment, Lower Plenty, Victoria, Australia). Sex, age, and species of each individual were determined visually. Age class was determined by assessing the degree of ossification of the knuckles (Davis and Hitchcock 1965, Thomas et al. 1979). With bat in hand, both wings were checked for parasites using a 1-watt LED headlamp. The ears were examined externally around the pinna, while internally they were examined to the base of the tragus. The tips of the fur were initially scanned for ectoparasites and then we used a steel fine-toothed comb to part the hair and expose any parasites among the fur. To minimize search bias, all ectoparasite sampling was done by J.A. Poissant. Any parasites that were seen on each individual were collected using a pair of stainless steel pointed tweezers and were preserved in 1.5-milliliter Eppendorf tubes (Eppendorf Industries) with 70% ethanol. Collection proceeded until all visible parasites were removed. Each tube was labeled with the corresponding capture number. 2008 J.A. Poissant and H.G. Broders 517 In the lab, parasites were identified using keys and identification characteristics in Brennan and Goff (1977), Lewis and Lewis (1994), Roberts and Janovy (2005), Rudnick (1960), Usinger (1966), and Whitaker (1982). Specifically, the bat fleas Myodopsylla insignis (Rothschild) were identified by the presence of genal spines on the front portion of the head instead of the back, which is a trait common only to those fleas which infect bats. The plate which comprises the anterior portion of the head is wide and smooth and a pronotal comb is present. Also, the maxilla is truncate, and the genal comb contains two spines (Whitaker 1982). Males were used to identify the species since females of this species cannot be reliably distinguished from the bat flea M. gentilis (Jordan and Rothschild), which is common in western Canada, but overlaps in range as close as Ontario and Quebec (Lewis and Lewis 1994). Cimex adjunctus, (Barber) (Bat Bug) were identified by the hind femora being less than 2.6 times as long as the greatest width of said femora, and the long bristles at the sides of the pronotum are long and thin and only slightly serrated at the tips (Usinger 1966). The bristles are a diagnostic feature, as all other possible species have noticeably serrate bristles on the pronotum. There were two species of spider mites (Spinturnix spp.) that, based on distribution, could possibly be found in Nova Scotia. Spinturnix americanus (Banks) were identifiable by the presence of tiny posterodorsal setae of the III and IV femora and tiny proximal dorsal setae of femora I and II (Rudnick 1960). Spinturnix bakeri (Rudnick), a closely related species, has long posterodorsal setae of the III and IV femora (Whitaker 1982). A larval Trombiculid mite, Leptotrombidium myotis (Ewing), was identified by having branched dorsotibial palpal seta and nude palpal femoral, genual, laterotibial, and ventrotibial setae. In addition, the galeal setae are branched, and there are two genualae on leg I. The sensillae are flagelliform and branched (Whitaker 1982). Another chigger which has been found on these species of bats in Indiana, Euschoengastia pipistrelle (Brennan), is identified by having expanded sensillae on the scutum, nude galeal seta, and branched genual seta (Whitaker 1982). Results Over 60.6 harp trapping hours, 2060 bats (1641 Myotis lucifugus, 417 M. septentrionalis, and 2 Perimyotis subflavus (Menu) (Eastern Pipistrelle) were captured. Within the entire sample, 453 bats (22.0%) were identified to have at least one ectoparasite. No ectoparasites were found on the P. subflavus. Among Myotis spp. bat groups (i.e., particular species-age-gender groups), prevalence ranged from 16.3% in adult male M. lucifugus to 34.2% in juvenile male M. septentrionalis. Four species of ectoparasites from four genera were identified (Table 1). Spinturnix americanus was the most widely encountered ectoparasite; 70.0% (n = 317) of bats having any ectoparasite were infected with this species (Table 1). All S. americanus were found on the wing and tail membranes of the host and were typically located near a bone or joint or close to the 518 Northeastern Naturalist Vol. 15, No. 4 body. On average, for each species/age group, prevalence of this parasite was higher for females than males, except for juvenile M. septentrionalis. Juvenile M. lucifugus has a lower prevalence of this parasite than juvenile M. septentrionalis. No S. bakeri were recorded. The larval Trombiculid mite, L. myotis, was found only on the pinna and tragus of the ear, and was confirmed to be present in 3.2% (n = 66) of the individuals sampled. The prevalence was comparable between species, with 3.5% (n = 57) of M. lucifugus and 2.2% (n = 9) of M. septentrionalis infested. There was, however, considerable difference between sexes, with adult males of both species having higher rates of infestation (Table 1). Prevalence of M. insignis on all bat groups was also low, with minimal variation among species, sex, and age groups. Cimex adjunctus was found on only one bat—a juvenile female M. septentrionalis. Discussion The ectoparasites of bats have not been well studied in Canada, and the objective of most projects has been to identify species (Jones and Thomas 1983, Whitaker 1973, Whitaker and Wilson 1974, Wright 1979), not to assess patterns of ectoparasite prevalence. As such, inter- and intra-specific variability in ectoparasite prevalence was unknown. The species richness of ectoparasites on M. lucifugus and M. septentrionalis in Nova Scotia was comparable to that found in Prince Edward Island (Jones and Thomas 1983). The same ectoparasite species found in Nova Scotia have been recorded on Myotis species as far south as Texas and as far west as California (Sasse and Pekins 2000, Whitaker and Wilson 1974). Both Myotis species are hosts to other parasites throughout their range; these included Macronyssus crosbyi (Ewing and Stover) and Olabidocarpus whitakeri (McDaniel and Coffman) (J.O. Whitaker Jr., Indiana State University, Terre Haute, IN, pers. comm.), but neither was found in this population. While prevalence varied dramatically among species of parasites and their hosts, some trends were noticeable. Juvenile M. lucifugus had a substantially lower prevalence than adult females, possibly resulting from parasites favoring adults due to a lower survivorship of juveniles over the winter Table 1. Prevalence of visible ectoparasites by sex and age class of Myotis lucifugus (Little Brown Bat) and M. septentrionalis (Northern Long-eared Bat) from August 21st to September 30th 2006 at Hayes Cave, NS, Canada. M. lucifugus M. septentrionalis Adult Juvenile Adult Juvenile Female Male Female Male Female Male Female Male Number of bats sampled 551.0 633.0 211.0 246.0 147.0 97.0 97.0 76.0 Spinturnix americanus 21.1 8.5 14.2 7.3 25.2 20.6 19.6 30.3 Leptotrombidium myotis 2.2 4.3 1.9 5.7 0.7 5.2 2.1 1.3 Myodopsylla insignis 4.0 3.9 7.1 4.5 5.4 5.2 4.1 3.9 Cimex adjunctus 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 Any ectoparasite 25.6 16.3 20.9 16.7 30.6 27.8 26.8 34.2 2008 J.A. Poissant and H.G. Broders 519 and the potential for transmitting surviving parasites to maternity colonies the following spring (Zahn and Rupp 2004). Previous work on similar species in Europe found lower parasite prevalence on juveniles within maternity colonies after fledging, which further supports the possibility of specific host selection (Zahn and Rupp 2004). Unlike the other parasites identified, S. americanus spends its entire life cycle on the host bat (Christe et al. 2000, Rudnick 1960), which is a potential reason for the significantly higher prevalence relative to the other parasite species, which only spend a portion of their lives on a bat. Spinturnix americanus had the highest prevalence and from a grooming standpoint, it should be perhaps the most difficult parasite to remove. The location of these parasites, close to major joints in the wing and in the short fur near the body, may make them difficult to remove, and the extra time spent grooming might result in less time available for other activities (Giorgi et al. 2001). From a fitness perspective, it would be advantageous for S. americanus to favor females and juveniles in summer maternity colonies rather than solitary males, and it would be expected that horizontal transmission would be highest in the close quarters of these colonies, especially among older individuals who would have had longer potential exposure to the parasite. Not surprisingly, there was a high prevalence of this species on adult females relative to conspecific males. Prevalence of L. myotis was low, but overall they were more prevalent on males. The location of the parasite, on the tragus and within the pinna, and an apparent lack of mobility during the larval stage, would make for easy removal from one individual by another (Kerth et al. 2003). Because females appear to be more social than males during the summer (Broders and Forbes 2004, Garroway and Broders 2007), these parasites are more likely to be groomed off by cooperating females within the maternity colonies. Most trombiculid mites are only parasitic for 3 to 4 days during the larval stage (Shatrov and Kudryashova 2006), and in successive stages (i.e., nymphal and adult), they typically leave the host and move into the soil where they feed on the eggs and instars of arthropods (Baker et al. 1956). Myodopsylla insignis, like most fleas, only parasitizes a host while in the adult stage of its life cycle (Segerman and Braack 1988). The female deposits eggs in and around the roost site, where they hatch and feed on excreted waste, eventually developing into pupae after several molts and then spinning a cocoon to reach the adult stage (Lewis and Lewis 1994). They need warm and humid conditions for successful completion of their life cycle. It would be expected that prevalence would be much higher during the summer months, particularly on adult females, due to the suitable microclimate and higher number of available hosts within maternity colonies. The prevalence of this parasite was relatively even across the population sampled at Hayes cave, suggesting that horizontal transmission was occurring for M. insignis during mating in the fall. Since adult fleas cannot survive for extended periods without food, they have the ability to survive on their hosts through 520 Northeastern Naturalist Vol. 15, No. 4 hibernation (Lewis and Lewis 1994), which increases the possibility of gene flow for M. insignis. In the absence of a host, and with dropping temperatures, the development of the pupae ceases. This delay in development is integral to overwinter survival of the Bat Flea population. When the bats return to their summer roost sites, their presence triggers the release of dormant sub-adult fleas to continue the cycle (Smith and Clay 1988). Given that Cimex adjunctus can survive up to 18 months without food and typically needs only 5 to 10 minutes on the host to feed (Roberts and Janovy 2005), it is not surprising that prevalence of this species was so low. Its relatively large size (up to 5 mm), coupled with weak attachment to the host body, suggests that it may be advantageous for C. adjunctus to stay within the summer roosts versus risking death by remaining on the individual through migration and hibernation. The prevalence of ectoparasites suggests that they may play an important role in the life history of bats in Nova Scotia. However, this study only examined one stage of the life history of bats in the province, and ectoparasite prevalence should be further investigated, especially on females within maternity colonies, to determine what effect ectoparasites may have on the reproductive potential and roost switching of these individuals. 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