Frequency Of Parasitism Research Articles

Performance of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) on eggs of Helicoverpa armigera (H\xfcbner) (Lepidoptera: Noctuidae)

Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is a polyphagous pest with a wide geographic distribution. This pest first arrived in Brazil in 2013, and since then studies on possible control methods for it have been necessary. A possible method for the control of H. armigera is using the egg parasitoid Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae). Therefore, the objective of this study was to evaluate the performance of T. pretiosum on H. armigera eggs, which are known to represent suitable hosts for the development of this parasitoid species in the laboratory. Parasitism and emergence rates and the duration of the egg-to-adult period of T. pretiosum were investigated following 24- and 48-h exposures of this parasitoid to H. armigera and Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) eggs. The longevity of offspring after the 24-h exposure was studied, as well as the frequency of parasitism and emergence, host preference, and the emergence of offspring from eggs of different ages or oviposited by lepidopterans on different days. Parasitism was 14.4 and 34.9% more frequent on C. cephalonica than on H. armigera after 24 and 48 h of exposure, respectively. In C. cephalonica, parasitism was 27.2% higher after 48 h. Parasitism was more frequent on C. cephalonica eggs collected on the second day of oviposition (76.2%), and on H. armigera on the third day of oviposition (71.1%). Parasitism frequency was lower on 2-day-old C. cephalonica eggs (63.3%) and on 3-day-old H. armigera eggs (41.3%). When tested with a chance of choice between hosts, T. pretiosum preferred H. armigera, while in the test with no chance of choice there was no difference in preference. Thus, T. pretiosum may be considered a tool for the Integrated Pest Management (IPM) of H. armigera.

Host Stage Preferences of Encarsia noyesi, Idioporus affinis, and Entedononecremnus krauteri: Parasitoids of the Giant Whitefly Aleurodicus dugesii (Hemiptera: Aleyrodidae)

Parasitoid wasps released as biological control agents may experience strong interspecific competition, which can lead to a reduction in pest control. The effects of competition can be mitigated if niche partitioning exists between species, such as parasitism preferences for different host stages. We examined host stage preferences for the parasitoids Encarsia noyesi Hayat (Hymenoptera: Aphelinidae), Idioporus affinis LaSalle and Polaszek (Hymenoptera: Pteromalidae), and Entedononecremnus krauteri Zolnerowich and Rose (Hymenoptera: Eulophidae). These parasitoids were introduced to the United States to control the giant whitefly Aleurodicus dugesii Cockerell (Hemiptera: Aleyrodidae), a pest of many economically important plants. Host stage preferences were examined using multiple metrics including: parasitism rates, relative preferences, handling times, and initial stage parasitism frequency. The data indicated differences in parasitoid preference hierarchies for the four A. dugesii nymphal stages. All A. dugesii nymphal stages were parasitized by I. affinis, which exhibited preference for the third instar. Unlike I. affinis, the first instar was not parasitized by E. noyesi, and its preference hierarchy differed with the fourth instar being the most preferred stage. The observed host-use breadth of E. krauteri was the narrowest observed of the three parasitoid species, only parasitizing the fourth and third instars, with a clear preference for the former. The observed differences in host-use breadth and stage preferences between parasitoid species in this system may promote their long-term coexistence in the field and facilitate biological control. Potential factors underlying the preferences exhibited by these parasitoids and their implications for biological control are discussed.

A laboratory study of host use by the cuckoo catfish Synodontis multipunctatus

The only known non-avian vertebrate obligate brood parasite is the cuckoo catfish (Synodontis multipunctatus), a Lake Tanganyikan endemic. The cuckoo catfish parasitizes Tanganyikan mouthbrooding cichlids, and under captive conditions, will also parasitize cichlids from other Rift Valley lakes. Here we examine the frequency of parasitism by the cuckoo catfish of Ctenochromis horei from Lake Tanganyika and three species from Lake Malawi and the greater Lake Victorian system in a laboratory setting. C. horei was parasitized significantly less (17%) than the allopatric species Haplochromis latifasciatus, Haplochromis nubilus, and Metriaclima estherae (combined parasitism rate of 28%). The lower rates of parasitism in C. horei may be due to differences in the mating ritual, oviposition (e.g., long periods of pseudo-spawning before actual oviposition), and behavioral adaptations (e.g., increased aggression towards the cuckoo catfish). The number of catfish eggs per parasitized brood was similar between C. horei, H. latifasciatus, H. nubilus, and M. estherae. Our results are comparable to findings from the field for C. horei parasitism frequency and number of cuckoo catfish per brood. We also analyzed the parasitism rate of the albino morph of Metriaclima zebra, a domestic strain. Parasitism rates and number of catfish per brood were the highest in the albino morphotype suggesting that the higher levels of parasitism may be related to lower aggressive behavior, lower visual acuity, or captive influence. Cuckoo catfish and mouthbrooding cichlids provide a model system for testing brood parasitism in a laboratory setting.

Are sleeping site ecology and season linked to intestinal helminth prevalence and diversity in two sympatric, nocturnal and arboreal primate hosts (Lepilemur edwardsi and Avahi occidentalis)?

BackgroundVarious factors, such as climate, body size and sociality are often linked to parasitism. This constrains the identification of other determinants driving parasite infections. Here, we investigate for the first time intestinal parasites in two sympatric arboreal primate species, which share similar activity patterns, feeding ecology, body size and sociality, and cope with the same climate conditions, but differ in sleeping site ecology: the Milne-Edward’s sportive lemur (Lepilemur edwardsi) and the Western woolly lemur (Avahi occidentalis). Comparison of these two species aimed to test whether differences in sleeping sites are related to differences in parasite infection patterns. Additionally, gender and seasonal factors were taken into account. Animals were radio-collared to record their sleeping site dynamics and to collect fecal samples to assess intestinal parasitism during both the dry and the rainy season.ResultsOnly low parasite diversity was detected, which is attributable to the strict arboreal lifestyle of these lemurs, limiting their contact with infective parasite stages. L. edwardsi, which sleeps in tree holes and repeatedly uses the same sleeping site, excreted eggs of strongyle and oxyurid nematodes, whereby strongyles always occurred in coinfection with oxyurids. In contrast, A. occidentalis, which sleeps on open branches and frequently changes sleeping sites, only excreted eggs of strongyle nematodes. This difference can be attributed to a potential favorable environment presented by tree holes for infective stages, facilitating parasitic transmission. Additionally, Strongylida in A. occidentalis were only observed in the rainy season, suggesting an arrested development during the dry season in the nematodes’ life cycle. Males and females of both lemur species showed the same frequency of parasitism. No differences in body mass of infected and non-infected individuals were observed, indicating that the animals’ body condition remains unaffected by the detected gastrointestinal parasites.ConclusionsThe comparison of two primate hosts with a very similar lifestyle suggests an influence of the sleeping site ecology on intestinal parasites. In A. occidentalis there was a clear seasonal difference in strongyle egg excretion. These results improve our understanding of the parasite ecology in these endangered primate species, which may be critical in the light of species conservation.

Distribution of Intestinal Parasites in Patients Hospitalized in Child Intensive Care Unit.

The purpose of the present study was to investigate the distribution of intestinal parasites in patients hospitalized in a child intensive care unit. The study was conducted on 150 patients between the ages of 2 months and 17 years between April 2016 and December 2016. Stool samples were tested by Native-Lugol, sedimentation (formol-ether solution), and acid fast method. Moreover, a questionnaire was used to obtain information about the socio-economic status of the patient, education level of the families, living conditions, and whether or not they have chronic illnesses. 40% of all patients were infected with one or more parasites 41.7% of girls and 38.2% of boys. In the present study, Giardia intestinalis (12.6%), Blastocystis hominis (12.6%), Entamoeba coli (7.3%), Cyclospora cayetanensis (5.3%), and Cryptosporidium spp. (2%) were detected. Statistical analysis was evaluated with the frequency of parasitism and revenue level, educational level of families, settlement area, whether there is a sewage network or not, whether animal husbandry is done or not, and source of water in home is from tap or well. The differences were not significantly. The possible reasons for the high rate of parasitosis, especially with G. intestinalis, E. coli, and B. hominis, are inadequate education, living in small houses with large numbers of people, sewage system, and lack of clean and safe drinking water.

Risk factors and infection due to Cryptosporidium spp. in dogs and cats in southern Rio Grande do Sul.

This study investigated the frequency of oocysts of Cryptosporidium spp. in feces from dogs and cats in five municipalities in the southern region of the state of Rio Grande do Sul. The risk factors associated with infection were also investigated. Feces samples from 110 dogs and 18 cats were stained using the auramine method. At the time of feces sampling, a questionnaire with semi-open-ended questions was applied to the animal guardians and all data obtained underwent statistical analysis. The real frequency of oocysts of Cryptosporidium spp. was 24.63% (27 dogs and two cats). Only four samples of dog feces were diarrheic and no presence of oocysts was observed in any of them. Variables that represented risk factors for infection were: homemade food, untreated water, circulation of animals on grassy terrain and living in the same environment as other animals (cattle). The results made it possible to inferring that within the population studied, the frequency of parasitism due to Cryptosporidium spp. in dogs was relevant and emphasize the asymptomatic nature of this infection. The adopting control measures are highlighted, particularly in relation to variables that represent risk factors for this infection.

Multi-modal defences in aphids offer redundant protection and increased costs likely impeding a protective mutualism.

The pea aphid, Acyrthosiphon pisum, maintains extreme variation in resistance to its most common parasitoid wasp enemy, Aphidius ervi, which is sourced from two known mechanisms: protective bacterial symbionts, most commonly Hamiltonella defensa, or endogenously encoded defences. We have recently found that individual aphids may employ each defence individually, occasionally both defences together, or neither. In field populations, Hamiltonella-infected aphids are found at low to moderate frequencies and while less is known about the frequency of resistant genotypes, they show up less often than susceptible genotypes in field collections. To better understand these patterns, we sought to compare the strengths and costs of both types of defence, individually and together, in order to elucidate the selective pressures that maintain multi-modal defence mechanisms or that may favour one over the other. We experimentally infected five aphid genotypes (two lowly and three highly resistant), each with two symbiont strains, Hamiltonella-APSE8 (moderate protection) and Hamiltonella-APSE3 (high protection). This resulted in three sublines per genotype: uninfected, +APSE8 and +APSE3. Each of the 15 total sublines was first subjected to a parasitism assay to determine its resistance phenotype and in a second experiment, a subset was chosen to compare fitness (fecundity and survivorship) in the presence and absence of parasitism. In susceptible aphid genotypes, parasitized sublines infected with Hamiltonella generally showed increased protection with direct fitness benefits, but clear infection costs to fitness in the absence of parasitism. In resistant genotypes, Hamiltonella infection rarely conferred additional protection, often further reduced fecundity and survivorship when enemy challenged, and resulted in constitutive fitness costs in the absence of parasitism. We also identified strong aphid genotype×symbiont-strain interactions, such that the best defensive strategy against parasitoids varied for each aphid genotype; one performed best with no protective symbionts, the others with particular strains of Hamiltonella. This surprising variability in outcomes helps explain why Hamiltonella infection frequencies are often intermediate and do not strongly track parasitism frequencies in field populations. We also find that variation in endogenous traits, such as resistance, among host genotypes may offer redundancy and generally limit the invasion potential of mutualistic microbes in insects.

Host specificity and aggregation for a widespread mistletoe in Campo Rupestre vegetation

Assessment of host infection and distribution patterns are crucial to understand the underling mechanisms that shape parasitic plant spread in natural ecosystems. However, such data remain scarce for mistletoes inhabiting Brazilian campo rupestre vegetation, old-growth montane fire-prone grasslands. We evaluated the host range and distribution patterns of the mistletoe Psittacanthus robustus (Loranthaceae) at seven 1-ha plots located at in Serra do Cipó, southeastern Brazil. We investigate if the frequency of parasitism by P. robustus is directly related to the relative abundance of host tree species in the community, and how prevalence and intensity of infection vary among different host tree species. Average mistletoe density was 120 individuals ha−1, which parasitized eight host species, including trees and shrubs in five families. Four tree species, Vochysia thyrsoidea, Qualea cordata (Vochysiaceae), Trembleya laniflora and Miconia ferruginata (Melastomataceae), comprised 95% of infected individuals. Twenty two percent of 1,108 trees sampled were parasitized by P. robustus, with host specificity within species in Myrtales Clade. Prevalence increased with host height for all tree species, with a highly aggregated distribution in few taller host trees within rocky outcrop patches in campo rupestre. The unveiling patterns of host infection and mistletoe distribution, support future studies addressing plant-plant, bird-plant and fire-plant interactions that might shape infection dynamics of this widespread mistletoe species in campo rupestre.

Occurrence of Bemisia tabaci (Hemiptera: Aleyrodidae) and Aphis gossypii (Hemiptera: Aphididae) on Okra Plants in a Semi-Arid Region of Brazil, with Notes on their Vertical Distribution and the Impact of Deltamethrin

The expansion of agriculture in the semi-arid region of northeastern Brazil has been associated to an increase in the number of insect pests and the indiscriminate use of agrochemicals. We performed a field survey of two major okra pests, Aphis gossypii and Bemisia tabaci, taking into consideration their within-plant vertical distribution. We also investigated the presence of parasitized insects and the short-time effect of the application of deltamethrin. Throughout the experiment, 59,787 phytophagous insects were collected, which were categorized in four groups: healthy nymphs/adults of Aphis gossypii (N = 31,767), A. gossypii parasitized by Hymenoptera (N = 4189), Bemisia tabaci eggs (N = 2507) and B. tabaci nymphs (N = 21,324). The abundance of A. gossypii was higher than that of B. tabaci at both, the control and the insecticide-treated area. The frequency of parasitism of A. gossypii by Hymenoptera was higher in the areas that did not receive deltamethrin. Higher numbers of A. gossypii occurred in the middle part of the plants and B. tabaci populations were lower in apical leaves.

Brood Parasitism Defense Behaviors Along an Altitudinal Gradient in the American Robin (Turdus Migratorius)

Some host species accept eggs from brood parasites over parts of their range and reject them in other areas representing an “evolutionary lag” in the development of rejection behavior or the loss of an adapative behavior when the selection pressure of brood parasitism is removed. Hosts may deter brood parasitism through egg rejection and aggressive nest defense behavior specifically targetting female brood parasites during the egg incubation period. In areas where parasitism frequencies are spatially and temporally variable, anti-parasite behaviors may decline as costs outweigh the benefits. Along the Colorado Front Range, American robins (Turdus migratorius) breed from low elevations where the brood parasitic Brown-headed Cowbird (Molothrus ater) is abundant to near timberline (3700 m) where cowbirds are uncommon. We tested the hypothesis that egg rejection and nest defense behaviors decline with reduced probability of parasitism. We found that robins accepted 100% of immaculate (robin-like) experimental eggs at both low and high elevations, but were more likely to reject spotted (cowbird-like) experimental eggs at low elevations than high elevations. Response to egg size was more variable than to egg color. When presented with a mount of a cowbird and Song Sparrow (Melospiza melodia) near the nest, robins responded more aggressively to cowbird models than to sparrows (control), and nest defense behavior towards cowbirds was longer and more aggressive at the lower elevation sites where cowbirds are common. These results suggest that egg rejection and nest-site aggression are costly adaptations to cowbird parasitism, and these behaviors decline when the threat of parasitism is reduced.

Patterns in parasitism frequency explained by diet and immunity

Patterns in parasitism frequency explained by diet and immunity

Enteric parasitic disease in children under 5 years of age, indigenous and non-indigenous, from rural communities in Paraguay

Official figures of mortality in children under five years of age in the Americas, report that infectious and parasitic diseases caused most of the deaths. To evaluate the frequency of intestinal parasites in vulnerable children, indigenous and non-indigenous, and their socio-environmental characteristics. We evaluated 247 children under five years of age, of both sexes. Descriptive study with an analytical component, transverse cutting. Copro-parasitological examinations were carried out and semi-structured interviews to collect socio-demographic data were conducted. The frequency of intestinal parasitic diseases was 56.1% and 35.5% in indigenous and non-indigenous children, respectively. In both populations, the most common pathogens were Blastocystis hominis and Giardia lamblia. We found a high frequency of parasitism in indigenous children at the expense of protozoa. Non-indigenous children still present the same parasitic species found in previous studies, suggesting the need to implement more control and prevention. The poor conditions in which they live favor the development of these diseases.

Grazing Impact on Brood Parasitism in the Black-capped Vireo

Grazing facilitates foraging opportunities for brown-headed cowbirds (Molothrus ater), an obligate brood parasite. Cowbirds can reduce productivity of their hosts, causing some host species to decline in abundance. Thus grazing indirectly influences productivity of some songbirds. The black-capped vireo (Vireo atricapilla) is an endangered songbird with most of its breeding range occurring in areas of ungulate grazing. A contributing factor to its endangered status is brown-headed cowbird parasitism. We monitored 382 black-capped vireo nests from 2012–2013 in Real, Kerr, Bandera, and Edwards Counties, Texas. We investigated how enclosed ungulate (characterized by the presence of enclosed ungulates) and wild ungulate–only (characterized by the absence of enclosed ungulates) systems influenced brood parasitism. We also examined how distance to water (distance from nest to nearest ungulate water source), nest concealment, and grassland in the landscape (proportion of grassland within 3 km of a nest) related to parasitism. Overall parasitism frequency was 30% (n = 166) in 2012 and 31% (n = 216) in 2013, moderate compared with other research, but above a proposed 30% threshold of concern. Grassland in the landscape was not important in predicting brood parasitism in wild ungulate–only grazing systems, but it was important in predicting brood parasitism in enclosed ungulate systems. In enclosed ungulate systems, there was low probability of brood parasitism with a small amount of grassland in the landscape and high probability of parasitism with a large amount of grassland in the landscape. Nest concealment and distance to water were not good predictors of brood parasitism.

Do parasitoids explain differential abundance of two syntopic orb-weaver spiders (Araneae: Araneidae)?

In this study, we examined the relative abundance of two congeneric species of orb-weaver spiders, Cyclosa fililineata and Cyclosa morretes, in an area of Atlantic forest in southeastern Brazil, and the relationship of this variable with fecundity and attacks by parasitoids. We also investigated responses to vibrational stimuli that simulated the approach of a wasp and described architectural changes in webs of parasitized individuals of C. fililineata. C. fililineata was more abundant throughout the year, although this species produced a lower number of egg sacs and a lower number of eggs per egg sac when compared with C. morretes. Both species showed similar types of behavioral responses to vibrational stimuli, but C. fililineata remained motionless more often. The frequency of parasitism by the wasp Polysphincta janzeni on adults and juveniles was low and similar for C. fililineata and C. morretes in both dry and wet seasons. The parasitoid caused alterations in the web design of C. fililineata similar of those observed in other orb-weavers attacked by ichneumonid wasps. Webs constructed by spiders parasitized by larvae in their last instar had a lower number of radii and sticky spirals were completely absent. An egg parasitoid, Baeus cyclosae, attacked C. morretes more often than C. fililineata, possibly as a consequence of its greater clutch size and/or larger eggs. These results indicate that egg mortality caused by B. cyclosae, but not subadult and adult mortality promoted by P. janzeni, may be an important factor determining the relative abundance of these two Cyclosa species.

The first morphometric and phylogenetic perspective on molecular epidemiology of Echinococcus granulosus sensu lato in stray dogs in a hyperendemic Middle East focus, northwestern Iran.

BackgroundHydatidosis is considered to be a neglected cyclo-zoonotic disease in Middle East countries particularly northwestern Iran which is caused by metacestode of tapeworm Echinococcus granulosus sensu lato. Human hydatidosis is a high public health priority in the area, however there is little known from a morphometric and phylogenetic perspective on molecular epidemiology of adult Echinococcus spp. in Iranian stray dogs.Methods80 dogs (38 males and 42 females) were collected during June 2013 to April 2014 in northwestern Iran. The isolated parasites from each dog were distinguished by morphometric keys including small, large hook length and blade length. Subsequently, isolates were confirmed by sequencing of mitochondrial cytochrome oxidase subunit 1 gene.Results16 (8 males and 8 females) (Prevalence 20 %) out of 80 dogs were infected to genus Echinococcus. With regard to demographic factors, the frequency of parasitism in both male, female adults and their age groups showed no difference (P > 0.05). The phylogenetic analyses of cox1 sequences firmly revealed the 13 sheep strains (G1), one buffalo strain (G3), one camel strain (G6) and one mixed infection. The findings of rostellar hook morphology show an intraspecies variation range among G1 isolates. However, hook measurements in Echinococcus derived from G1 (sheep strain) were not a significant difference from those G6 and G3 strains. Six unique haplotypes were identified containing a high range of diversity (Haplotype diversity 0.873 vs. Nucleotide diversity 0.02).ConclusionsFirst presence of camel strain (G6) in this region seems to indicate that potential intermediate hosts play a secondary role in the maintenance of camel-dog biology. Current findings have heightened our knowledge about determination of Echinococcus prevalence, strains of taxonomy and genotypic trait of parasite in Iranian stray dogs which will also help in the development of strategies for monitoring and control of infected stray dogs in the area.

No change in common cuckoo Cuculus canorus parasitism and great reed warblers’ Acrocephalus arundinaceus egg rejection after seven decades

The coevolutionary process among avian brood parasites and their hosts involves stepwise changes induced by the antagonistic selection pressures of one on the other. As long‐term data on an evolutionary scale is almost impossible to obtain, most studies can only show snapshots of such processes. Information on host behaviour, such as changes in egg rejection rates and the methods of rejection are scarce. In Hungary there is an interesting case between the common cuckoo Cuculus canorus and the great reed warbler Acrocephalus arundinaceus, where the level of parasitism is unusually high (around 50%). We compared host rejection rates and methods of rejection from within our own project to that of an early study carried out and published almost 70 yr ago in the same region. Our comparisons revealed high and stable rates of parasitism (range: 52–64%), and marked fluctuations in the ratio of multiply parasitized nests (range: 24–52%). No difference was revealed in egg rejection rates after 7 decades (34–39%). Linear mixed‐effects modelling revealed no year effect on the type host responses toward the parasitic egg(s) during the years of study (categorized as acceptance, ejection, burial, and nest desertion). Cuckoo egg rejection was primarily affected by the type of parasitism, as more cuckoo eggs were rejected during single parasitism than from multiply parasitized nests. Our comparison did not reveal any directional changes in this cuckoo–host relationship, except a slight decrease in the frequency of multiple parasitism, which is likely to be independent from coevolutionary processes.

Reproductive success of the specialist brood parasite Screaming Cowbird in an alternative host, the Chopi Blackbird

ABSTRACT The Screaming Cowbird (Molothrus rufoaxillaris) is the most specialized brood-parasitic cowbird, relying almost entirely on the Bay-winged Cowbird (Agelaioides badius) as host. Recently, Screaming Cowbirds have expanded their range to areas where Bay-winged Cowbirds are absent, and they are exploiting the Chopi Blackbird (Gnorimopsar chopi). Interactions between Screaming Cowbirds and Chopi Blackbirds are largely unexplored, as is the reproductive success of the parasite in this host. Screaming Cowbirds, Chopi Blackbirds, and Bay-winged Cowbirds coexist in northeastern Argentina, providing an ideal system to explore interactions between a specialist brood parasite and an alternative host and to compare the reproductive success of the parasite in its main host and in an alternative host. Screaming Cowbirds parasitized both hosts throughout their breeding seasons (Chopi Blackbirds, mid-October to mid-January; Bay-winged Cowbirds, mid-November to mid-March). Frequency of parasitism was lower in Chop...

High frequency but low impact of brood parasitism by the specialist Screaming Cowbird on its primary host, the Baywing

Brood-parasitic cowbirds (Molothrus spp.) exploit the parental care of other species (hosts) that raise their offspring. Parasitism by cowbirds reduces host reproductive success in several ways and quantifying such costs is an important step to better understand evolutionary interactions in host-parasite associations. We estimated the costs of parasitism by the host-specialist Screaming Cowbird (M. rufoaxillaris) to the reproductive success of its primary host, the Baywing (Agelaioides badius). We tested the effect of Cowbird parasitism on egg survival, hatching success, nestling survival and body mass at fledging of Baywings in a population of eastern Argentina where the frequency of parasitism by Screaming Cowbirds exceeds 90% of Baywing nests. Egg survival decreased with the number of Screaming Cowbird eggs laid during the egg-stage and, on average, host clutch-size was reduced by 10% per parasitic event. However, contrary to our expectations, we did not find any clear effect of parasitism on hatching success, nestling survival and body mass at fledging of Baywings. Our results suggest that, despite its high frequency, parasitism by Screaming Cowbirds has a rather little effect on the viability of Baywing offspring. We discuss how clutch rejection behaviour and flexible nest-provisioning rules of the hosts might help to explain this paradoxical result.

Parasitic isopods associated with sea turtles nesting in Brazil

Studies of sea turtle epibiosis have focused on the diversity and ecology of facultative commensalisms and less attention has been given to parasitic associations, in which the epibiont species derives nutrients from the tissue of the host turtle. We present the first description and quantitative survey of the parasitic isopods Excorallana costata, Excorallana bicornis and Excorallana oculata on loggerhead (N = 79) and hawksbill turtles (N = 23), and E. costata on olive ridley turtles (N = 9), nesting on Praia do Forte, Bahia, Brazil during the 2009–2010 season. Excorallana costata was the most common isopod species (N = 651), followed by E. bicornis (N = 77) and E. oculata (N = 20). Patterns include: (1) E. costata exhibited a higher frequency and intensity of parasitism than E. bicornis and E. oculata and (2) loggerheads hosted parasitic isopods at a higher frequency and intensity than hawksbills and olive ridleys. We also detected temporal shifts in the occurrence and intensity of parasitism across the nesting season, which strongly suggests that turtles were parasitized by all three isopod species during their internesting periods. Because parasitic isopods were observed only rarely prior to the 2009–2010 turtle-nesting season and have continued to be common in subsequent seasons, it is important to gain a better understanding of the basic biology of these interactions, the reasons for their recent emergence, and the potential biological impacts on turtle, as well as isopod, populations.

Nesting ecology of grassland songbirds: effects of predation, parasitism, and weather

Understanding the breeding ecology of grassland birds is vital for understanding the mechanisms underlying their widespread population declines. We describe the breeding biology of Sprague's Pipit (Anthus spragueii), Vesper Sparrow (Pooecetes gramineus), Savannah Sparrow (Passerculus sandwichensis), Baird's Sparrow (Ammodramus bairdii), and Western Meadowlark (Sturnella neglecta) and quantify the effects of nest predation, brood parasitism, and weather on the nest survival of these species in southeastern Alberta. Nest predation was the primary cause of nest failure, accounting for 75% of all nest losses. Daily survival rates were higher during incubation than the nestling stage for the three sparrow species, and nest survival of Baird's Sparrows was highest at intermediate temperatures. For all five species, clutch size, hatching success, and fledging success were within the range of values previously reported for these species in other parts of their range. Brown-headed Cowbirds parasitized nests of all species except Sprague's Pipit, with 4–11% of nests containing cowbird eggs. Savannah Sparrow experienced the highest frequency of brood parasitism and was the only species to successfully fledge cowbird young. Parasitized nests of Savannah Sparrows had reduced clutch size and hatching success, and fledged fewer young compared to non-parasitized nests. The overall cost of parasitism to Savannah Sparrows was at least 1.7 young per successful nest.