Santiago Plischuk

South American native bumblebees (Hymenoptera: Apidae) infected by Nosema ceranae (Microsporidia), an emerging pathogen of honeybees (Apis mellifera)

As pollination is a critical process in both human-managed and natural terrestrial ecosystems, pollinators provide essential services to both nature and humans. Pollination is mainly due to the action of different insects, such as the bumblebee and the honeybee. These important ecological and economic roles have led to widespread concern over the recent decline in pollinator populations that has been detected in many regions of the world. While this decline has been attributed in some cases to changes in the use of agricultural land, the effects of parasites could play a significant role in the reduction of these populations. For the first time, we describe here the presence of Nosema ceranae, an emerging honeybee pathogen, in three species of Argentine native bumblebees. A total of 455 bumblebees belonging to six species of genus Bombus were examined. PCR results showed that three of the species are positive to N. ceranae (Bombus atratus, Bombus morio and Bombus bellicosus). We discuss the appearance of this pathogen in the context of the population decline of this pollinators.

The invasion of southern South America by imported bumblebees and associated parasites

The Palaearctic Bombus ruderatus (in 1982/1983) and Bombus terrestris (1998) have both been introduced into South America (Chile) for pollination purposes. We here report on the results of sampling campaigns in 2004, and 2010-2012 showing that both species have established and massively expanded their range. Bombus terrestris, in particular, has spread by some 200 km year(-1) and had reached the Atlantic coast in Argentina by the end of 2011. Both species, and especially B. terrestris, are infected by protozoan parasites that seem to spread along with the imported hosts and spillover to native species. Genetic analyses by polymorphic microsatellite loci suggest that the host population of B. terrestris is genetically diverse, as expected from a large invading founder population, and structured through isolation by distance. Genetically, the populations of the trypanosomatid parasite, Crithidia bombi, sampled in 2004 are less diverse, and distinct from the ones sampled later. Current C. bombi populations are highly heterozygous and also structured through isolation by distance correlating with the genetic distances of B. terrestris, suggesting the latters expansion to be a main structuring factor for the parasite. Remarkably, wherever B. terrestris spreads, the native Bombus dahlbomii disappears although the reasons remain unclear. Our ecological and genetic data suggest a major invasion event that is currently unfolding in southern South America with disastrous consequences for the native bumblebee species.

Invasive Bombus terrestris (Hymenoptera: Apidae) parasitized by a flagellate (Euglenozoa: Kinetoplastea) and a neogregarine (Apicomplexa: Neogregarinorida)

The flagellate Crithidia bombi and the neogregarine Apicystis bombi have been found in individuals of Bombus terrestris, a Palaearctic species of bumble bee commercially reared and shipped worldwide for pollination services. B. terrestris has recently entered into the northwestern Patagonia region of Argentina from Chile, where it was introduced in 1998. Prevalence was 21.6% for C. bombi and 3.6% for A. bombi (n=111). The pathogens were not detected in 441 bumble bees belonging to five of the eight known Argentine native species (Bombus atratus, Bombus morio, Bombus bellicosus, Bombus opifex, Bombus tucumanus) collected elsewhere in the country. Although the absence of natural occurrence of C. bombi and A. bombi in Argentine native bumble bees cannot be ascertained at present due to the limited surveys performed, it is important to report their detection in invasive B. terrestris. The invasion event is relatively recent and the accompanying pathogens are not species specific within the genus Bombus.

Apicystis bombi (Apicomplexa: Neogregarinorida) parasitizing Apis mellifera and Bombus terrestris (Hymenoptera: Apidae) in Argentina

The neogregarine Apicystis bombi is considered a low prevalence parasite of Bombus spp. Before our work it has only once been detected in one single specimen of the Western honeybee Apis mellifera. This contribution reports the presence of A. bombi parasitizing both A. mellifera and Bombus terrestris at a site in Northwestern Argentine Patagonia (Bariloche, close to the border with Chile) and analyses its possible absence in the Pampas region, the most important beekeeping region of the country. In Bariloche, prevalence of A. bombi in A. mellifera was 7.6% in 2009, and 13.6% in 2010, whereas in B. terrestris it was 12.1%. Infections were not detected in 302 bee hives periodically prospected along 3 years (almost 400 000 honeybee specimens) in the Pampas. Analysis with the probability program FreeCalc2 suggested a possible absence of A. bombi in this area. Because of high virulence showed in several species of Bombus in the Northern hemisphere, A. bombi should be closely monitored in A. mellifera and in native Bombus species or other Apidae.

Effects of the organic acids produced by a lactic acid bacterium in Apis mellifera colony development, Nosema ceranae control and fumagillin efficiency.

The European honey bee Apis mellifera is known to be affected by many parasites and pathogens that have great impact over the insect development. Among parasites affecting bee health, Nosema ceranae is one of the main biotic factors affecting colony populations. As honey bee populations decline, interest in pathogenic and mutualistic relationships between bees and microorganisms has increased. The main goal of the current study was to assess the effect of the oral administration of the metabolites produced by Lactobacillus johnsonii CRL1647 (mainly organic acids) supplemented in syrup, on: (I) N. ceranae sporulation dynamics before and after fumagillin application, and (II) performance of A. mellifera colonies. Different experiments were conducted to evaluate the effects of these bacterial metabolites on bees: in vitro administration revealed no toxic effects against bees. Colonies fed with the lactic acids incremented their beehive population and also the amount of fat bodies per bee. Finally, the organic acids reduced the intensity of the pathogen after the second application of treatment as well as enhanced the fumagillin efficiency. This study provides important information for the development of new control substances against nosemosis.

ANNUAL DIET OF THE LITTLE HAIRY ARMADILLO, CHAETOPHRACTUS VELLEROSUS (MAMMALIA, DASYPODIDAE), IN BUENOS AIRES PROVINCE, ARGENTINA

Abstract Analysis of the stomach contents of 28 little hairy armadillos (Chaetophractus vellerosus), collected during a 14-month period at Pipinas, Argentina, showed that about 63.6% of the weight of prey items was composed of animal remains, 18% was plant material, and the remaining 18.4% was undetermined organic remains. Insects were the most frequent diet item, followed by plant material, amphibians, reptiles, and lastly birds and mammals in similar proportion. During autumn, plant material was the most abundant item, followed by vertebrates and invertebrates. During winter invertebrates prevailed, followed by a lower percentage of vertebrates and scarce plant remains. Invertebrates also were predominant during spring, whereas plant material and vertebrates composed very low percentages.

Genetic variability of the neogregarine Apicystis bombi, an etiological agent of an emergent bumblebee disease.

The worldwide spread of diseases is considered a major threat to biodiversity and a possible driver of the decline of pollinator populations, particularly when novel species or strains of parasites emerge. Previous studies have suggested that populations of introduced European honeybee (Apis mellifera) and bumblebee species (Bombus terrestris and Bombus ruderatus) in Argentina share the neogregarine parasite Apicystis bombi with the native bumblebee (Bombus dahlbomii). In this study we investigated whether A. bombi is acting as an emergent parasite in the non-native populations. Specifically, we asked whether A. bombi, recently identified in Argentina, was introduced by European, non-native bees. Using ITS1 and ITS2 to assess the parasite’s intraspecific genetic variation in bees from Argentina and Europe, we found a largely unstructured parasite population, with only 15% of the genetic variation being explained by geographic location. The most abundant haplotype in Argentina (found in all 9 specimens of non-native species) was identical to the most abundant haplotype in Europe (found in 6 out of 8 specimens). Similarly, there was no evidence of structuring by host species, with this factor explaining only 17% of the genetic variation. Interestingly, parasites in native Bombus ephippiatus from Mexico were genetically distant from the Argentine and European samples, suggesting that sufficient variability does exist in the ITS region to identify continent-level genetic structure in the parasite. Thus, the data suggest that A. bombi from Argentina and Europe share a common, relatively recent origin. Although our data did not provide information on the direction of transfer, the absence of genetic structure across space and host species suggests that A. bombi may be acting as an emergent infectious disease across bee taxa and continents.

Status of the alien pathogen Paranosema locustae (Microsporidia) in grasshoppers (Orthoptera: Acridoidea) of the Argentine Pampas

Abstract After experimental introductions from North America in 1978–1982, the biocontrol agent Paranosema locustae became established in grasshopper communities of the western Pampas region of Argentina. The use and establishment of P. locustae in Argentina constitute both a case of neoclassical or new association biological control (use of an alien species against native pests) and a case of pathogen pollution (anthropogenic introduction–establishment of an infectious disease in populations of native species). Since P. locustae is a multihost pathogen among grasshoppers, its presence in the western Pampas represents an additional factor disrupting grasshopper communities according to the differential susceptibility of each species and possibly threatening some species. Microscopic examination of 504 grasshopper samples (the mean number of individuals per sample = 185) belonging to 43 species from 93 localities throughout the Pampas revealed an establishment area of approximate 90,000 km2 from about 35° North to 38° South and from 61° East to 65° West. Field infections by P. locustae have now been detected in 21 grasshopper species in the western Pampas. Susceptible species with geographic distributions mostly restricted to the establishment area and with numerically small populations, like the melanopline Scotussa daguerrei, are predicted to be the ones facing higher risks of negative impacts.

Tubulinosema pampeana sp. n. (Microsporidia, Tubulinosematidae), a pathogen of the South American bumble bee Bombus atratus

An undescribed microsporidium was detected and isolated from the South American bumble bee Bombus atratus collected in the Pampas region of Argentina. Infection intensity in workers averaged 8.2 × 10(7)spores/bee. The main site of infection was adipose tissue where hypertrophy of adipocytes resulted in cyst-like body formation. Mature spores were ovoid and monomorphic. They measured 4.00 μm × 2.37 μm (fresh) or 3.98 μm × 1.88 μm (fixed). All stages were diplokariotic and developed in direct contact with host cytoplasm. Isofilar polar filament was arranged in 16 coils in one or, posteriorly, two layers. Coiling angle was variable, between perpendicular and almost parallel to major spore axis. Late meronts and sporogonial stages were surrounded by vesicles of approximately 60 nm in diameter. Based on both new and already designed primers, a 1827 bp (SSUrRNA, ITS, LSUrRNA) sequence was obtained. Data analyses suggest that this microsporidium is a new species of the genus Tubulinosema. The name Tubulinosema pampeana sp. n. is proposed.

The tracheal mite Locustacarus buchneri in South American native bumble bees (Hymenoptera: Apidae)

As in other regions of the world, bumble bees (Bombus spp.) are important pollinators in the neotropics. Despite its relevance, knowledge on their health is still limited in the region. While external acari are known to occur in these insects, presence of the internal, tracheal mite Locustacarus buchneri is here reported for first time. After the examination of 2,508 individuals of eight Bombus species from Argentina, two workers of Bombus bellicosus and one of Bombus atratus were found parasitized by L. buchneri in localities within San Luis and Buenos Aires provinces, respectively. The rare occurrence recorded agrees with findings from elsewhere in the world.