Ancient origin and maternal inheritance of blue cuckoo eggs

Maternal inheritance via the female-specific W chromosome was long ago proposed as a potential solution to the evolutionary enigma of co-existing host-specific races (or 'gentes') in avian brood parasites. Here we report the first unambiguous evidence for maternal inheritance of egg colouration in the brood-parasitic common cuckoo Cuculus canorus. Females laying blue eggs belong to an ancient (∼2.6 Myr) maternal lineage, as evidenced by both mitochondrial and W-linked DNA, but are indistinguishable at nuclear DNA from other common cuckoos. Hence, cuckoo host races with blue eggs are distinguished only by maternally inherited components of the genome, which maintain host-specific adaptation despite interbreeding among males and females reared by different hosts. A mitochondrial phylogeny suggests that blue eggs originated in Asia and then expanded westwards as female cuckoos laying blue eggs interbred with the existing European population, introducing an adaptive trait that expanded the range of potential hosts

Hatching Strategies in Monogenean (Platyhelminth) Parasites that Facilitate Host Infection

In parasites, environmental cues may influence hatching of eggs and enhance the success of infections. The two major endoparasitic groups of parasitic platyhelminths, cestodes (tapeworms) and digeneans (flukes), typically have high fecundity, infect more than one host species, and transmit trophically. Monogeneans are parasitic flatworms that are among the most host specific of all parasites. Most are ectoparasites with relatively low fecundity and direct life cycles tied to water. They infect a single host species, usually a fish, although some are endoparasites of amphibians and aquatic chelonian reptiles. Monogenean eggs have strong shells and mostly release ciliated larvae, which, against all odds, must find, identify, and infect a suitable specific host. Some monogeneans increase their chances of finding a host by greatly extending the hatching period (possible bet-hedging). Others respond to cues for hatching such as shadows, chemicals, mechanical disturbance, and osmotic changes, most of which may be generated by the host. Hatching may be rhythmical, larvae emerging at times when the host is more vulnerable to invasion, and this may be combined with responses to other environmental cues. Different monogenean species that infect the same host species may adopt different strategies of hatching, indicating that tactics may be more complex than first thought. Control of egg assembly and egg-laying, possibly by host hormones, has permitted colonization of frogs and toads by polystomatid monogeneans. Some monogeneans further improve the chances of infection by attaching eggs to the host or by retaining eggs on, or in, the body of the parasite. The latter adaptation has led ultimately to viviparity in gyrodactylid monogeneans

Host age selection behaviour of Trichogramma aurosum Sugonjaev & Sorokina (Hymenoptera: Trichogrammatidae)

Host age selection in several German strains of Trichogramma aurosum Sugonjaev & Sorokina was examined in laboratory choice tests under direct observation for 90 min., in order to select candidate strains for attempts at controlling the codling moth, Cydia pomonella L. (Lepidoptera: Tortricidae). Experiments were conducted at room temperature by exposing combinations of two host ages (zero vs. 4 and 1 vs. 5-day old) to a single female wasp. Host age did not appear to affect the wasps parasitization behaviour, although they spent longer time drilling on old eggs (4 and 5 days old) compared with fresh ones (0 and 1 day old). This not necessarily means that they preferred fresh eggs over old ones, since both type of hosts were parasitized in the choice test. Possibly an increased mechanical resistance of the chorion of older eggs was responsible for the prolonged drilling time. Mean drumming time was independent of host age. Mean duration of drilling and drumming was in general longest in the first and last egg attacked by all T. aurosum strains tested and for all host ages. Drilling time consumed more than 80% of the mean handling time of all strains tested for all host ages, followed by resting and walking

Cold-storage of Piezodorus guildinii (Hemiptera: Pentatomidae) eggs for rearing Telenomus podisi (Hymenoptera: Platygastridae)

Piezodorus guildinii (Hemiptera: Pentatomidae) is an important soybean pest, and one of its main natural enemies is Telenomus podisi (Hymenoptera: Platygastridae). Rearing of the parasitoid is constrained by the hosts' egg quality, which deteriorates after few generations in laboratory, therefore, cold-stored host eggs utilization could be a useful tool for augmentative biological control. Thus, the objective was to evaluate the quality of P. guildinii cold-stored eggs, on the performance of parental and F1 generation of T. podisi. Hosteggs 24 hour old were stored at -18°C for one (N= 53), two (N= 28) or three months (N= 29), and approximately 40 host eggs were offered to a T. podisi female per treatment, for 48 hours. The control treatment consisted of 24-hour-old non-frozen host eggs, obtained and kept at 24°C (N= 55). Parental generation parasitism and progeny´s emergence on frozen eggs was significantly lower than on non-frozen eggs, even for the shorter storage period. Male proportion and preimaginal development time of the progeny increased with freezing period. However, parasitism proportion caused by adults of F1, and emergence, male proportion, and preimaginal development time of F2 were not affected. Although the performance of T. podisi on frozen P. guildinii eggs was significantly lower than on nonfrozen ones, host eggs storage for up to two months allowed obtaining a parasitism rate of 40% with a high emergence rate. This could be helpful enough to maintain mass rearings, mainly during the host hibernation period, and to enhance field parasitism when host is scarce.Fil: Cingolani, Maria Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; ArgentinaFil: Greco, Nancy Mabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; ArgentinaFil: Liljesthrom, Gerardo Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; Argentin

Oviposition in the blood-sucking insect Rhodnius prolixus is modulated by host odors

Background: Triatomine bugs are blood-sucking insects, vectors of Chagas disease. Despite their importance, their oviposition behavior has received relatively little attention. Some triatomines including Rhodnius prolixus stick their eggs to a substrate. It is known that mechanical cues stimulate oviposition in this species. However, it is not clear if chemical signals play a role in this behavior. We studied the role of host cues, including host odor, in the oviposition behavior of the triatomine R. prolixus. Methods: Tests were carried out in an experimental arena and stimuli consisted of a mouse or hen feathers. The number of eggs laid and the position of those eggs with respect to the stimulus source were recorded. Data were analyzed using the Mann-Whitney and Kruskal-Wallis tests. Results: Both a mouse and hen feathers stimulated oviposition. In addition, hen feathers evoked a particular spatial distribution of eggs that was not observed in the case of mouse. Conclusions: We propose that volatile chemical cues from the host play a role in the oviposition behavior of triatomines that stick their eggs. Thus, host odor would stimulate and spatially guide oviposition.Fil: Guidobaldi, Fabio. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; ArgentinaFil: Guerenstein, Pablo Gustavo. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; Argentin

Host species determines egg size in Oriental cuckoo

© 2018 The Zoological Society of London.The Oriental cuckoo Cuculus optatus is an obligate brood parasite associated with species of the genus Phylloscopus. Four distinct phenotypes of Oriental cuckoo eggs, matching eggshell colour patterns of Arctic warbler Phylloscopus borealis, common chiffchaff (Siberian) P. collybita tristis, yellow-browed warbler P. inornatus and Pallas's leaf warbler P. proregulus, have been identified in the Russian part of its breeding area. We compared egg length, breadth and volume of Oriental cuckoo egg phenotypes with eggs of the corresponding hosts from three geographical regions in Russia: the Urals, Siberia and the Far East. We found significant oometric differences between Oriental cuckoo egg phenotypes. Egg breadth of each cuckoo group matched the egg breadth of the host species, while the length of cuckoo eggs did not match egg length in host species. Our results can be explained in terms of clutch geometry. An egg sticking out above the clutch is likely to be rejected by the host and so breadth should match the host's egg. This constrains cuckoos in maintaining large egg volumes, which are essential for providing a cuckoo chick with the energy required to eject the host eggs and chicks. An increased egg length might compensate for breadth constraints. We suggest that the size of cuckoo eggs might also be affected by parental care - when only one parent is involved in feeding, eggs need to be larger. This might explain why the longest cuckoo eggs belonged to the phenotype parasitizing the smallest host, Pallas's leaf warbler, where only one parent feeds the chicks. In our view, differences in egg sizes of Oriental cuckoo phenotypes provide evidence of their adaptations to brood parasitism on small leaf warbler species.Peer reviewe

The sight of an adult brood parasite near the nest is an insufficient cue for a honeyguide host to reject foreign eggs.

Hosts of brood-parasitic birds typically evolve anti-parasitism defences, including mobbing of parasitic intruders at the nest and the ability to recognize and reject foreign eggs from their clutches. The Greater Honeyguide Indicator indicator is a virulent brood parasite that punctures host eggs and kills host young, and accordingly, a common host, the Little Bee-eater Merops pusillus frequently rejects entire clutches that have been parasitized. We predicted that given the high costs of accidentally rejecting an entire clutch, and that the experimental addition of a foreign egg is insufficient to induce this defence, Bee-eaters require the sight of an adult parasite near the nest as an additional cue for parasitism before they reject a clutch. We found that many Little Bee-eater parents mobbed Greater Honeyguide dummies while ignoring barbet control dummies, showing that they recognized them as a threat. Surprisingly, however, neither a dummy Honeyguide nor the presence of a foreign egg, either separately or in combination, was sufficient to stimulate egg rejection

Comparing and contrasting development and reproductive strategies in the pupal hyperparasitoids Lysibia nana and Gelis agilis (Hymenoptera: Ichneumonidae)

In most animals, the optimal phenotype is determined by trade-offs in life-history traits. Here, I compare development and reproductive strategies in two species of solitary secondary hyperparasitoids, Lysibia nana and Gelis agilis, attacking pre-pupae of their primary parasitoid host, Cotesia glomerata. Parasitoid larvae of both species exploit a given amount of host resources with similar efficiency. However, adults exhibit quite different reproductive strategies. Both species are synovigenic, and female wasps emerge with no mature eggs. However, G. agilis must first host-feed to produce eggs, while L. nana does not host-feed but mobilizes internal resources carried over from larval feeding to initiate oogenesis. Further, G. agilis is wingless, produces large eggs, has a long life-span, and generates only small numbers of progeny per day, whereas these traits are reversed in L. nana. Given unlimited hosts, the fecundity curve in L. nana was “front-loaded,” whereas in G. agilis it was depressed and extended over much of adult life. In L. nana (but not G. agilis), wasps provided with honey but no hosts lived significantly longer than wasps provided with both honey and hosts. Differences in the fecundity curves of the two hyperparasitoids are probably based on differing costs of reproduction between them, with the wingless G. agilis much more constrained in finding hosts than the winged L. nana. Importantly, L. nana is known to be a specialist hyperparasitoid of gregarious Cotesia species that pupate in exposed locations on the food plant, whereas Gelis sp. attack and develop in divergent hosts such as parasitoid cocoons, moth pupae and spider egg sacs. Consequently, there is a strong match between brood size in C. glomerata and egg production in L. nana, but a mismatch between these parameters in G. agilis.

Metazoan-protozoan parasite co-infections and host body weight in St Kilda Soay sheep

For hundreds of years, the unmanaged Soay sheep population on St Kilda has survived despite enduring presumably deleterious co-infections of helminth, protozoan and arthropod parasites and intermittent periods of starvation. Important parasite taxa in young Soay sheep are strongyles (Trichostrongylus axei, Trichostrongylus vitrinus and Teladorsagia circumcincta), coccidia (11 Eimeria species) and keds (Melophagus ovinus) and in older animals, Teladorsagia circumcincta. In this research, associations between the intensity of different parasite taxa were investigated. Secondly, the intensities of different parasite taxa were tested for associations with variation in host weight, which is itself a determinant of over-winter survival in the host population. In lambs, the intensity of strongyle eggs was positively correlated with that of Nematodirus spp. eggs, while in yearlings and adults strongyle eggs and coccidia oocysts were positively correlated. In lambs and yearlings, of the parasite taxa tested, only strongyle eggs were significantly and negatively associated with host weight. However, in adult hosts, strongyles and coccidia were independently and negatively associated with host weight. These results are consistent with the idea that strongyles and coccidia are exerting independent selection on Soay sheep.</p

Influences of Host Density, Temperature, and Parasite Age on the Reproductive Potential of \u3ci\u3eBathyplectes Curculionis\u3c/i\u3e (Hymenoptera: Ichneumonidae), an Endoparasite of the Alfalfa Weevil (Coleoptera: Curculionidae)

Alfalfa weevil larvae were exposed to Bathyplectes curculionis (Thomson) to determine the effect of host density, temperature, and parasite age on the reproductive potential of curculionis. Percent parasitism was found to be inversely proportional to host density and most of the parasites distributed their eggs randomly regardless of host density. The number of eggs deposited was largely independent of temperature. Peak egg laying was reached in three days from which point the parasite\u27s capabilities diminished with increasing age. The longevity of ovipositing females was shorter than females that were not exposed to larvae