Seasonal change of nest survival and related aspects in an aggregation ofLasioglossum duplex (Dalla torre), a eusocial halictine bee (Hymenoptera: Halictidae)

Nest survival in an aggregation of a eusocial halictine bee, Lasioglossum duplex, was censused through an annual cycle. Out of 2,500 nests marked at the beginning of solitary phase in the spring, only 25.5% attained eusocial phase. But 60.5% of 636 nests attaining eusocial phase successfully produced sexual offspring. This shows that solitary phase is the most vulnerable period in the annual cycle. A very low productivity in eusocial phase in the census year was clarified from examination of 99 nests in the autumn. The number of prospective foundresses surviving to the next year was estimated upon the number of brood cells in examined nests and of old females surviving these nests. Deviation between this estimate and the number of nests made in the next spring was 8.8%, confirming a drop of population size to less than one third in the next year. Some nests solitarily made in the summer by dispersed females were examined. Productivity in such nests was extremely low, hence these nests should contribute virtually nothing to the next generation. Possible factors affecting the low productivity in eusocial phase were enumerated though none of these were supported by concrete evidence. Some considerations were given on the relation between obtained results and colony life cycle in eusocial insects, particularly in halictine bees.     

Morphology,ultrastructure, and development of the parasitic larva and its surrounding trophamnion of Polypodium hydriforme Ussov (Coelenterata)

Summary The larval stage of Polypodium hydriforme is planuliform and parasitic inside the growing oocytes of acipenserid fishes. The larva has inverted germ layers and a special envelope, the trophamnion, surrounding it within the host oocyte. The trophamnion is a giant unicellular provisory structure derived from the second polar body and performing both protective and digestive functions, clearly a result of adaptation to parasitism. The trophamnion displays microvilli on its inner surface, and irregular protrusions anchoring it to the yolk on its outer surface. Its cytoplasm contains long nuclear fragments, ribosomes, mitochondria, microtubules, microfilaments, prominent Golgi bodies, primary lysosomes, and secondary lysosomes with partially digested inclusions.The cells of the larva proper are poorly differentiated. No muscular, glandular, neural, interstitial, or nematocyst-forming cells have been found. The entodermal (outer layer) cells bear flagella and contain rough endoplasmic reticulum; the ectodermal (inner layer) cells lack cilia and contain an apical layer of acid mucopolysaccharid granules. The cells of both layers contain mitochondria, microtubules, and Golgi bodies; their nuclei display large nucleoli with nucleolonema-like structure, decondensed chromatin, and some perichromatin granules. At their apical rims, the ectodermal cells form septate junctions; laterally, the cells of both layers form simple contacts and occasional interdigitations. The lateral surfaces of entodermal cells are strengthened by microtubules.     

The levels of natural Nosema spp. infection in Apis mellifera iberiensis brood stages

Nosema ceranae is the most prevalent endoparasite of Apis mellifera iberiensis and it is a major health problem for bees worldwide. The infective capacity of N. ceranae has been demonstrated experimentally in honey bee brood, however no data are available about its prevalence in brood under natural conditions. Thus, brood combs from 10 different hives were analyzed over two consecutive years, taking samples before and after winter. A total of 1433 larvae/pupae were analyzed individually and N. ceranae (3.53%) was the microsporidian most frequently detected, as opposed to Nosema apis (0.42%) which was more frequently detected in conjunction with N. ceranae (0.71%). The active multiplication of both microsporidians was confirmed by the expression (real-time-PCR) of the N. ceranae polar tube protein 3 gene and/or the N. apis RNA polymerase II gene in 24% of the brood samples positive for Nosema spp. Both genes are related to microsporidian multiplication. As such, N. ceranae multiplication was confirmed in 1.06% of the samples, while N. apis multiplication was only observed in co-infections with N. ceranae (0.07%). Brood cells were analyzed for the presence of Nosema spp., as those are the immediate environment where the brood stages develop. The brood samples infected by Nosema spp. were in brood cells in which that microsporidians were not detected, while brood cells positive for N. ceranae hosted brood stages that were not apparently infected, indicating that this is unlikely to be the main pathway of infection. Finally, the colonies with brood infected by N. ceranae showed higher levels (numbers) of infected adult bees, although the differences were not significant before (P = 0.260), during (P = 0.055) or after (P = 0.056) brood sampling. These results show that N. ceranae is a bee parasite ubiquitous to all members of the colony, irrespective of the age of the bee. It is also of veterinary interest and should be considered when studying the epidemiology of the disease.     

Vitamin e hypervitaminosis in laying hens

The aim of this investigation was to contribute to the problem of overdosing vitamin E. A total of 80 laying hens, divided into 5 groups, were fed diets supplemented with 0; 100, 1000, 10 000 and 20 000 mg/kg vitamin E over a period of 20 weeks within two brooding tests. Laying performance and hatching parameters were registered. All vitamin E doses did not significantly influence health and performances of hens. Vitamin E content of eggs increased from 1 to 4, 21, 46 and 51 mg per egg with vitamin E supplementation. High doses decreased oxidative stability of abdominal fat, vitamin A concentration of liver and egg yolk colour. In both tests vitamin E supplements of 10 000 and 20 000 mg/kg feed resulted in a decrease of living hatched chicken, which demonstrated an adverse effect. Further studies seem to be necessary to explain the effect.     

Dispersal behavior of the parasitic wasp Cotesia urabae (Hymenoptera: Braconidae): A recently introduced biocontrol agent for the control of Uraba lugens (Lepidoptera: Nolidae) in New Zealand

Estimates of the dispersal range of a recently introduced biocontrol agent in its new environment are vital to understanding its relative searching capacity, and to foresee the maximum area that could be covered in a release event. In New Zealand, the solitary endoparasitoid Cotesia urabae Austin and Allen (Hymenoptera: Braconidae) was first released in January 2011 as a biological control agent for the gum leaf skeletoniser, Uraba lugens Walker (Lepidoptera: Nolidae). The objective of this study was to utilize an experimental approach to quantify the dispersal behavior of one generation of C. urabae. In our experiment, which used sentinel larvae as target hosts, parasitoids dispersed up to 20 m away from the release point but parasitism was highest within 5 m of the release site. A high level of parasitism was observed at the release tree (87.6%) which suggests that most of the females released may have stayed there. According to the dispersal model developed from the data collected, Cotesia would be able to disperse up to 53 m in one release event. In addition, significant differences were found between the different directions tested for dispersal, showing a clear downwind effect on dispersal suggesting that wind has a direct effect on the dispersal behavior of C. urabae in the field.     

Ultrastructure of early stages of Rozella allomycis (Cryptomycota) infection of its host, Allomyces macrogynus (Blastocladiomycota)

This study reconstructs early stages of Rozella allomycis endoparasitic infection of its host, Allomyces macrogynus. Young thalli of A. macrogynus were inoculated with suspensions of R. allomycis zoospores and allowed to develop for 120 h. Infected thalli at intervals were fixed for electron microscopy and observed. Zoospores were attracted to host thalli, encysted on their surfaces, and penetrated their walls with an infection tube. The parasite cyst discharged its protoplast through an infection tube, which invaginated the host plasma membrane. The host plasma membrane then surrounded the parasite protoplast and formed a compartment confining it inside host cytoplasm. The earliest host-parasite interface within host cytoplasm consisted of two membranes, the outer layer the host plasma membrane and the inner layer the parasite plasma membrane. At first a wide space separated the two membranes and no material was observed within this space. Later, as the endoparasite thallus expanded within the compartment, the two membranes became closely appressed. As the endoparasite thallus continued to enlarge, the interface developed into three membrane layers. Thus, host plasma membrane surrounded the parasite protoplast initially without the parasite having to pierce the host plasma membrane for entry. Significantly, host-derived membrane was at the interface throughout development.     

GENETIC AND GEOGRAPHIC VARIATION IN REJECTION BEHAVIOR OF CUCKOO EGGS BY EUROPEAN MAGPIE POPULATIONS: AN EXPERIMENTAL TEST OF REJECTER-GENE FLOW

Host responses toward brood parasitism have been shown to differ among populations depending on the duration of sympatry between host and parasite, although populations not currently parasitized show rejection behavior against parasitic eggs. The persistence of rejection behavior in unparasitized host populations and rapid increases of rejection rate in parasitized ones have sometimes been explained as the result of gene flow of rejecter genes from sympatry to allopatry (rejecter-gene flow hypothesis). We present data on the rejection behavior of magpies (Pica pica) the main European host of the great spotted cuckoo (Clamator glandarius), in 15 populations (nine sympatric six allopatric) across their distribution range in Europe. Rejection rates of mimetic and nonmimetic model eggs were significantly higher in sympatric than in allopatric magpie populations, although differences in rejection rate of both mimetic and nonmimetic model eggs between magpie populations were significantly correlated even after controlling tor phylogenetic effects, with differences between sympatric and allopatric magpie populations being larger for mimetic than for nonmimetic model eggs. Differences in rejection of mimetic model eggs were related to both genetic and geographic distances between populations, but differences in rejection rate of nonmimetic model eggs were unrelated to these distances. However, when comparing only sympatric populations, differences in rejection rate of both mimetic and nonmimetic model eggs were related to geographic distances. A multiple autocorrelation analysis revealed that differences among populations in rejection rates of mimetic model eggs had a strong geographic component whereas the main component of rejection rate of nonmimetic model eggs was genetic rather than geographic. These results support the rejecter-gene flow hypothesis. We discuss differences in rejection rates of mimetic and nonmimetic model eggs that suggest the egg-recognition ability of the host is genetically based, but is affected by a learning process for fine tuning of recognition.     

Experimentally delayed hatching triggers a magnified stress response in a long-lived bird

In birds, the timing of breeding is a key life-history trait with crucial fitness consequences. We predicted that parents may value a brood less if it hatched later than expected, thereby decreasing their parental effort. In addition, breeding effort would be further modulated by the age-specific decline of future breeding opportunities. We experimentally investigated whether snow petrels, Pagodroma nivea, were less committed to care for a chick that hatched later than expected. The timing of hatching was manipulated by swapping eggs between early and late known-age pairs (7-44 years old), and investigations on hormonal and behavioral adjustments were conducted. As a hormonal gauge of parental commitment to the brood, we measured the corticosterone stress response of guarding adults. Indeed, an acute stress response mediates energy allocation towards survival at the expense of current reproduction and is magnified when the current brood value is low, as it is expected to be in young and/or delayed parents. As predicted, egg desertion and the magnitude of the stress response was stronger in delayed pairs compared to control ones. However, the treatment did not decrease the length of the guarding period, chick condition and chick survival. In addition, old parents resisted stress better (lower stress-induced corticosterone levels) than young ones. Our study provides evidence that snow petrels, as prudent parents, may value a brood less if it hatched later than expected. Thus, in long-lived birds, the responsiveness to stressors appeared to be adjusted according to the individual prospect of future breeding opportunities (age) and to the current brood value (timing of breeding).     

The effects of experimentally infecting Australian tree frogs with lungworms (Rhabdias pseudosphaerocephala) from invasive cane toads

Invasive species may transmit novel pathogens to native taxa, and lacking a history of coevolutionary interactions with the pathogen, the new hosts may be severely affected. Cane toads (Rhinella marina) were introduced to Australia in 1935, bringing with them a lungworm (Rhabdias pseudosphaerocephala) not found in Australian frogs. Previous studies suggest that most frog species are unaffected by this parasite, but one tree-frog (Litoria caerulea) can harbour high numbers of lungworm. More detailed laboratory studies confirm and extend the earlier results on L. caerulea and show that Rhabdias infection severely depresses the viability of metamorphs of an allied tree-frog species, Litoria splendida. Parasitic larvae infected both of these two closely related tree-frog species, but the two anurans differed in the consequences of infection. Parasitism reduced the survivorship of L. splendida and the stamina of both species. Lungworms did not consistently reduce growth rates or affect heart rates in either tree-frog species. Although L. splendida is potentially vulnerable to the arrival of toad-transported lungworms, rates of host-switching may be reduced by low levels of habitat overlap between the frogs (which are rock-dwelling and arboreal) and the toads (which are terrestrial and most abundant in disturbed habitats).