RESUMEN
Most humans carry mites in the hair follicles of their skin for their entire lives. Follicular mites are the only metazoans tha continuously live on humans. We propose that Demodex folliculorum (Acari) represents a transitional stage from a host-injuring obligate parasite to an obligate symbiont. Here, we describe the profound impact of this transition on the genome and physiology of the mite. Genome sequencing revealed that the permanent host association of D. folliculorum led to an extensive genome reduction through relaxed selection and genetic drift, resulting in the smallest number of protein-coding genes yet identified among panarthropods. Confocal microscopy revealed that this gene loss coincided with an extreme reduction in the number of cells. Single uninucleate muscle cells are sufficient to operate each of the three segments that form each walking leg. While it has been assumed that the reduction of the cell number in parasites starts early in development, we identified a greater total number of cells in the last developmental stage (nymph) than in the terminal adult stage, suggesting that reduction starts at the adult or ultimate stage of development. This is the first evolutionary step in an arthropod species adopting a reductive, parasitic or endosymbiotic lifestyle. Somatic nuclei show underreplication at the diploid stage. Novel eye structures or photoreceptors as well as a unique human host melatonin-guided day/night rhythm are proposed for the first time. The loss of DNA repair genes coupled with extreme endogamy might have set this mite species on an evolutionary dead-end trajectory.
RESUMEN
OBJECTIVES: This paper presents a systematic review of the emerging international research evidence for the use of situational judgement tests (SJTs) for testing important non-academic attributes (such as empathy, integrity and resilience) in selection processes. METHODS: Several databases (e.g. MEDLINE, PsycINFO, Web of Science) were searched to retrieve empirical studies relating to SJTs published between 1990 and 2010. Personal contact with experts in the field was made to identify any unpublished research or work in progress to obtain the most current material. Finally, reference lists were checked to access other relevant journal articles and further research. All research studies were required to meet specific inclusion criteria selected by two independent reviewers. RESULTS: Over 1000 citations were identified during the initial literature search; following the review of abstracts, full-text copies of 76 articles were retrieved and evaluated. A total of 39 articles that adequately met the inclusion criteria were included in the final review. The research evidence shows that, compared with personality and IQ tests, SJTs have good levels of reliability, predictive validity and incremental validity for testing a range of professional attributes, such as empathy and integrity. CONCLUSIONS: SJTs can be designed to test a broad range of non-academic constructs depending on the selection context. As a relatively low-fidelity assessment, SJTs are a cost-efficient methodology compared with high-fidelity assessments of non-academic attributes, such as those used in objective structured clinical examinations. In general, SJTs are found to demonstrate less adverse impact than IQ tests and are positively received by candidates. Further research is required to explore theoretical developments and the underlying construct validity of SJTs.
