103 research outputs found
A Comparative Functional Approach to the Host Detection Behaviour of Parasitic Wasps. 1. A Qualitative Study on Eucoilidae and Alysiinae
We studied host detection behaviour in Alysiinae (Braconidae; Ichneumonoidea) and Eucoilidae (Cynipoidea), the larvae of which are endoparasitoids of fly larvae and in- vestigated whether this behaviour is determined by their descent or can be considered an adaptation to different environments. We compared the searching behaviour of fe- males of 32 alysiine and 25 eucoilid species from a variety of microhabitats and from different dipteran hosts by using qualitative behavioural variables. Three main modes of searching were detected: vibrotaxis, ovipositor searching and antennal searching, and the species could be classified according to the role these different modes play in the detection of host larvae. The searching modes are largely dependent upon the taxonomic position of the species. In most cases species belonging to one genus show a similar behaviour pattern. However, we also encountered examples of radiation; closely related species that search differently. The function of the three searching modes has not been elucidated so far. Therefore we cannot say that similar searching modes in unrelated species are examples of adaptive convergence. Especially in Drosophila parasitoids we encountered great differences in searching behaviour be- tween different species living in the same microhabitat. We believe differences at all levels of searching, including host detection behaviour may contribute to niche segre- gation and create possibilites for different parasitoid species to coexist in the same microhabitat, even when they attack the same host species
Superparasitism and host discrimination by Asobara tabida nees (Braconidae: Alysiinae), a larval parasitoid of Drosophilidae.
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Het smalle pad. Beperkingen van individuen en de evolutie van levensgemeenschappen
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Why Five Fingers? Evolutionary Constraints on Digit Numbers
Evolutionary changes in the number of digits and other limb elements appear to be severely constrained, probably as a result of a low level of modularity during limb development. Reduced limb structures typically develop through a process of construction followed by destruction and amniotes have evolved many digit-like structures rather than actual extra digits. In amniotes, limb development occurs during the crucial phylotypic stage, when many inductive interactions are occurring throughout the body. As a result, changes in limb development usually engender changes in other body parts. Thus, mutations that change the number of limb bones are expected to have many pleiotropic effects, which severely reduces the chance of such mutations being successful. In amphibians with aquatic larvae, limb development occurs after the phylotypic stage and limb development is decoupled from the interactivity of the phylotypic stage. The constraint of pleiotropic effects is, therefore, expected to be weaker. This expectation agrees with the larger variability in the number of hand and foot structures in amphibians, with frogs even occasionally possessing six toes. These facts once again emphasize the importance of pleiotropic effects as constraints to evolutionary change, including their role in the conservation of body plans
Rapid establishment of a regular distribution of adult tropical Drosophila parasitoids in a multi-patch environment by patch defence behaviour
Advice of the Scientific Advisory Committee on Seal Rehabilitation in the Netherlands
Two species of seal breed in the Netherlands, the grey seal (Halichoerus grypus) and the harbour seal (Phoca vitulina). The populations of both species have increased markedly over the past 40 years. Harbour seals have recovered from a minimum number of around 500 in 1980 to some 9,000 seals in 2016 (Figure 1). Grey seals were effectively absent from the Netherlands until 1980, but have made a remarkable recovery; the numbers counted during the annual moult increased to around 5,100 in 2016. The number of pups born each year for both species is equivalent to around 20% of the number of seals counted during the moult
Elevated risk of infection with SARS-CoV-2 Beta, Gamma, and Delta variants compared with Alpha variant in vaccinated individuals
The extent to which severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOCs) break through infection- or vaccine-induced immunity is not well understood. We analyzed 28,578 sequenced SARS-CoV-2 samples from individuals with known immune status obtained through national community testing in the Netherlands from March to August 2021. We found evidence of an increased risk of infection by the Beta (B.1.351), Gamma (P.1), or Delta (B.1.617.2) variants compared with the Alpha (B.1.1.7) variant after vaccination. No clear differences were found between vaccines. However, the effect was larger in the first 14 to 59 days after complete vaccination compared with ≥60 days. In contrast to vaccine-induced immunity, there was no increased risk for reinfection with Beta, Gamma, or Delta variants relative to the Alpha variant in individuals with infection-induced immunity.</p
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