In the Communal Bee Andrena Scotica (Hymenoptera, Andrenidae) Rj Paxton, I Fries, Nj Pieniazek, J Tengö
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High incidence of infection of an undescribed microsporidium (Microspora) in the communal bee Andrena scotica (Hymenoptera, Andrenidae) Rj Paxton, I Fries, Nj Pieniazek, J Tengö To cite this version: Rj Paxton, I Fries, Nj Pieniazek, J Tengö. High incidence of infection of an undescribed microsporid- ium (Microspora) in the communal bee Andrena scotica (Hymenoptera, Andrenidae). Apidologie, Springer Verlag, 1997, 28 (3-4), pp.129-141. hal-00891412 HAL Id: hal-00891412 https://hal.archives-ouvertes.fr/hal-00891412 Submitted on 1 Jan 1997 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. 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Original article High incidence of infection of an undescribed microsporidium (Microspora) in the communal bee Andrena scotica (Hymenoptera, Andrenidae) RJ Paxton I Fries2 NJ Pieniazek J Tengö 1 Lehrstuhl Entwicklungsphysiologie, Zoologisches Institut der Universität Tübingen, Auf der Morgenstelle 28, D-720 76 Tübingen, Germany; 2 Department of Entomology, Swedish University of Agricultural Sciences, Box 7044, S-750 07 Uppsala, Sweden; 3 Division of Parasitic Diseases, Centers for Disease Control and Prevention, 4770 Buford Highway NE, Mailstop F13, Atlanta, GA 30341, USA; 4 Ecological Research Station of Uppsala University, Ölands Skogsby 6280, S-386 93 Färjestaden, Sweden (Received 7 March 1997; accepted 25 June 1997) Summary — We document the abundance and distribution of the spores of an undescribed species of microsporidium within its host, the communal bee Andrena scotica, and relationships between this parasite and its host. Only the host’s adipose tissue (fat bodies) appeared infected, with up to 118 x 106 spores per bee. All hosts at one field site were infected. High spore load within hosts appeared to curtail female reproductive activity. However, we were unable to discern the microsporidium’s effects on male fecundity in that some males with a high spore load did undertake mate searching activ- ity. Longevities of naturally infected A scotica males and females in a flight cage were apparently unaf- fected by the microsporidium. Spores were found in A scotica from other field sites but not in other species of bees, suggesting the microsporidium has a high degree of host specificity. Andrena scotica / communal bee / infection / Microspora / microsporidium INTRODUCTION though for many their host specificity is lit- tle known. Their effects on hosts vary from Microspora is a large group of obligate intra- the benign to highly pathogenic, and they cellular parasites that appear to affect all may have significant effects on the popula- major animal groups. They are particularly tion dynamics of their hosts (Briano et al, widespread and abundant in arthropods, 1995).. * Correspondence and reprints Tel: (49) 7071-2975342; fax: (49) 7071-296950; e-mail: [email protected] Notwithstanding their apparent preva- 1989). It is univoltine, imagines flying from May lence in arthropods, only three species of to early July at our principal study site, Törn- bottens on the Baltic island of microsporidia are currently known from the Stugby, Öland, SE Sweden (16°34’ E, 56°29’ N, 35 m asl). At over 20000 described species of bees this site, all nests of A scotica have been 1974). Nosema perma- (Apoidea) (Michener, apis nently marked with plastic and metal tags. Adult and Nosema ceranae are of the parasites female bees are communal, that is, two or more, ventricular epithelial cells of Apis mellifera and rarely up to several hundred, females share a and Apis cerana, respectively (Fries et al, common nest entrance (Paxton et al, 1996). 1996). The former can have a severely debil- Beneath the nest entrance, each female constructs itating effect upon its host in temperate cli- her own brood cells in the soil, mass provisions mates (Fries, 1993). Nosema bombi, origi- them with pollen and nectar, and in each she lays one Larvae consume the stored food and nally confused with N apis (eg, Showers et egg. then metamorphose into adults before entering al, 1967, but see and Vette, 1993; Eijnde winter diapause in their natal cells (Paxton et al, McIvor and Malone, is an infection of 1995), 1997). Offspring emerge above ground in the apparently numerous species of Bombus following spring through their mother’s nest across the world (MacFarlane et al, 1995). It entrance; sons remain above ground in search of parasitises cells of host Malpighian tubules, mates whilst mated daughters construct and pro- and possibly other tissue types too (Eijinde vision their own cells in fossorial nests. Imag- ines that and in one do not sur- and Vette, 1993), though its effects on its emerge fly year vive to the hosts are seemingly benign (Fisher and following year. Pomeroy, 1989). In a recent study of Euro- pean bumble bees, Shykoff and Schmid- Collection of material Hempel (1991b) found a low prevalence of N bombi. However there is in general little from the host bee, A scotica data on the abundance and distribution of microsporidian parasites in natural popula- A random sample of host males and females was collected from Törnbottens Stugby in 1995 as tions of or on their effects on hosts. hosts, they first emerged in May and June from their In this paper we report on a high inci- natal nests (for details, see Paxton and Tengö, These A scotica were dence of the spores of a currently unde- 1996). ’emerging’ weighed scribed microsporidium within the haemo- on an electronic benchtop balance to ± 0.1 mg to provide an estimate of their size (Rust, 1991). coel of imagines of a primitively social (communal) bee Andrena scotica Perkins Additional, reproductively active males were 1916 (= Andrena jacobi Perkins 1921) in collected at random from Törnbottens Stugby in 1995 as undertook their characteristic mate SE Sweden. We document the distribution they searching flights (Tengö, 1979) over bushes and and abundance of these microsporidian low trees (2-10 m height), and additional, repro- and some spores within and among hosts ductively active females were collected at random relationships between host and microsporid- in the same year as they returned to nests at Törn- ium. A full description of the microsporid- bottens Stugby with pollen provisions. The head ium will be given by Fries et al in a future widths of these imagines, termed ’field’ bees, were measured under a dissection paper. microscope using an eyepiece graticule to ± 0.03 mm (16 x magnification) in lieu of weight as an estimate of body size because weights of field bees vary con- AND MATERIALS METHODS siderably depending upon the quantity of nectar and pollen that they carry. The host, Andrena scotica ’Overwintering’ adults were excavated from their underground natal cells at Törnbottens The host, A scotica, is a fossorial bee, common Stugby in the winter of 1995-96 and their head and widespread in northern Europe (Westrich, widths were also measured. Adipose tissue (fat bodies), brain, Dufour’s carefully examined for the presence of gland, Malpighian tubules, ovarioles, small intes- microsporidian spores. In 1996, A scotica female tine, thoracic muscle and the ventriculus of ’field’ bees were also collected from flowers at infected imagine hosts were carefully examined Kalmar on the Swedish mainland, 14 km west using phase contrast light microscopy (400 x of Törnbottens Stugby. Fat bodies of some of magnification) to locate microsporidian spores. these bees were carefully examined for Spores were removed from host tissue, fixed and microsporidia whilst other Kalmar ’field’ bees stained for transmission electron microscopy to were homogenised to quantify the numbers of aid in identification (Fries et al, unpublished microsporidian spores they contained, as data). described above. To determine the incidence of infection of A small number of bees of other Andrena ’emerging’ host bees at Törnbottens Stugby, species was collected from Törnbottens Stugby imagines were dissected under insect saline (0.9% and Kalmar in 1996 and examined for NaCl) and scored for the presence or apparent microsporidian spores. In addition, imagines of absence of microsporidian spores in their adi- a cleptoparasitic bee, Nomada marshamella pose tissue. For other ’emerging’ hosts, and all (Kirby, 1802) (Hymenoptera, Anthophoridae), ’field’ and ’overwintering’ bees collected from whose larvae consume the offspring egg or young Törnbottens Stugby, we quantified the number of larva in an A scotica cell and then consume the spores per bee by homogenising imagines in I food stores of that cell, were collected as they or 10 mL of insect saline and counting first emerged in spring 1995 from the natal nests microsporidian spores in the homogenate using of their host A scotica at Törnbottens Stugby. a Neubauer Improved haemocytometer (depth They were also carefully examined for the pres- 0.1 mm, see Cantwell, 1970). ence of microsporidian spores. Longevity of infected host bees Statistical analysis To document the relationship between the abun- A log-linear model (logit analysis, Norusis, 1990) dance of the in a host and host microsporidium was used to compare (i) differences among host A scotica were collected as longevity, imagines sex, (ii) differences among host nest of origin, from their natal nests at Törnbot- they emerged and (iii) the interaction between host sex and tens in 1995, and Stugby weighed individually nest of origin in the proportions of A scotica marked on their thoraxes. Then were held in they emerging with or apparently without spores in a m x 1 m x 1 m) in nylon netting flight cage (1 1995 at Törnbottens Stugby.