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BackgroundCichlid fishes have radiated into hundreds of species in the Great Lakes of Africa. Brightly colored males display on leks and vie to be chosen by females as mates. Strong discrimination by females causes differential male mating success, rapid evolution of male color patterns and, possibly, speciation. In addition to differences in color pattern, Lake Malawi cichlids also show some of the largest known shifts in visual sensitivity among closely related species. These shifts result from modulated expression of seven cone opsin genes. However, the mechanisms for this modulated expression are unknown.ResultsIn this work, we ask whether these differences might result from changes in developmental patterning of cone opsin genes. To test this, we compared the developmental pattern of cone opsin gene expression of the Nile tilapia, Oreochromis niloticus, with that of several cichlid species from Lake Malawi. In tilapia, quantitative polymerase chain reaction showed that opsin gene expression changes dynamically from a larval gene set through a juvenile set to a final adult set. In contrast, Lake Malawi species showed one of two developmental patterns. In some species, the expressed gene set changes slowly, either retaining the larval pattern or progressing only from larval to juvenile gene sets (neoteny). In the other species, the same genes are expressed in both larvae and adults but correspond to the tilapia adult genes (direct development).ConclusionDifferences in visual sensitivities among species of Lake Malawi cichlids arise through heterochronic shifts relative to the ontogenetic pattern of the tilapia outgroup. Heterochrony has previously been shown to be a powerful mechanism for change in morphological evolution. We found that altering developmental expression patterns is also an important mechanism for altering sensory systems. These resulting sensory shifts will have major impacts on visual communication and could help drive cichlid speciation.

A SARS-CoV-2 variant B1.1.7 containing a mutation Δ69/70 has spread rapidly in the UK and shows an identifiable profile in ThermoFisher TaqPath RTqPCR (S-gene target failure; SGTF). We analysed recent test data for trends and significance. Linked Ct values for respiratory samples showed that a low Ct for ORF1ab and N were clearly associated with SGTF. Significantly more SGTF samples had higher inferred viral loads between 1x10 7 and 1x10 8. Our conclusion is that patients whose samples exhibit the SGTF profile are more likely to have high viral loads, which may explain higher infectivity and rapidity of spread.

Objectives The COVID-19 pandemic has highlighted the extreme vulnerability of older people and other individuals who reside in long term care, creating an urgent need for evidence-based policy that can adequately protect these community members. This study aimed to provide synthesized evidence to support policy decision-making. Design Rapid narrative review investigating strategies that have prevented or mitigated SARS-CoV-2 transmission in long term care. Setting and Participants Residents and staff in care settings such as nursing homes and long term care facilities. Methods PubMed/Medline, Cochrane Library and Scopus were systematically searched, with studies describing potentially effective strategies included. Studies were excluded if they did not report empirical evidence (for example commentaries and consensus guidelines). Study quality was appraised on the basis of study design; data were extracted from published reports and synthesised narratively using tabulated data extracts and summary tables. Results Searches yielded 713 articles; 80 papers describing 77 studies were included. Most studies were observational with no randomized controlled trials identified. Intervention studies provided strong support for widespread surveillance, early identification and response, and rigorous infection prevention and control (IPC) measures. Symptom or temperature based screening, and single point-prevalence testing, were found to be ineffective, and serial universal testing of residents and staff was considered crucial. Attention to ventilation and environmental management, digital health applications and acute sector support were also considered beneficial although evidence for effectiveness was lacking. In observational studies, staff represented substantial transmission risk and workforce management strategies were important components of pandemic response. Higher performing facilities with less crowding and higher nurse staffing ratios had reduced transmission rates. Outbreak investigations suggested that facility-level leadership, inter-sectoral collaboration and policy that facilitated access to critical resources were all significant enablers of success. Conclusions and Implications High quality evidence of effectiveness in protecting LTCFs from COVID-19 was limited at the time of this study, though continues to emerge. Despite widespread COVID-19 vaccination programs in many countries, continuing prevention and mitigation measures may be required to protect vulnerable long term care residents from COVID-19 and other infectious diseases. This rapid review summarises current evidence regarding strategies which may be effective.