Reflecting optics in the diverticular eye of a deep-sea barreleye fish (Rhynchohyalus natalensis)

We describe the bi-directed eyes of a mesopelagic teleost fish, Rhynchohyalus natalensis, that possesses an extensive lateral diverticulum to each tubular eye. Each diverticulum contains a mirror that focuses light from the ventro-lateral visual field. This species can thereby visualize both downwelling sunlight and bioluminescence over a wide field of view. Modelling shows that the mirror is very likely to be capable of producing a bright, well focused image. After Dolichopteryx longipes, this is only the second description of an eye in a vertebrate having both reflective and refractive optics. Although superficially similar, the optics of the diverticular eyes of these two species of fish differ in some important respects. Firstly, the reflective crystals in the D. longipes mirror are derived from a tapetum within the retinal pigment epithelium, whereas in R. natalensis they develop from the choroidal argentea. Secondly, in D. longipes the angle of the reflective crystals varies depending on their position within the mirror, forming a Fresnel-type reflector, but in R. natalensis the crystals are orientated almost parallel to the mirror's surface and image formation is dependent on the gross morphology of the diverticular mirror. Two remarkably different developmental solutions have thus evolved in these two closely related species of opisthoproctid teleosts to extend the restricted visual field of a tubular eye and provide a well-focused image with reflective optics

Mitochondrial differentiation, introgression and phylogeny of species in the Tegenaria atrica group (Araneae, Agelenidae)

The relationships between the three members of the Tegenaria atrica group (T. atrica, T. saeva and T. gigantea) were examined with DNA sequence data from mitochondrial CO1, 16S rRNA, tRNAleu(CUN) and ND1 genes. Members of this group of large house spiders have overlapping distributions in western Europe and hybridize with each other to a variable degree. The close relatedness of all three species was supported by all analyses. T. saeva and T. gigantea are more closely affiliated than either is to T. atrica. Haplotypes clearly assignable to T. gigantea were also present in many specimens of T. saeva suggesting asymmetrical introgression of mtDNA from T. gigantea into T. saeva. Molecular clock calibrations (CO1) suggest that deeper divisions within the genus Tegenaria may be in excess of 10 million years old, and that the evolutionary history of the T. atrica group has been moulded by Quaternary glacial-interglacial cycles

A Cause Map Approach to Exploring MIS Benefits

This paper considers the problem of implementing large strategic MIS in the UK Health Sector, which has recently been the subject of wide-reaching institutional reforms involving the introduction of information technology. The paper details the empirical results from four case hospitals studied over two years. The research involved a cause map investigation of the collective constructs and organizational processes impacting upon the achievement of benefits, as perceived by the stakeholders. A model is proposed which gives some novel insights into the phenomena involved

Controlling Methicillin-Resistant Staphylococcus Aureus (MRSA) in a Hospital and the Role of Hydrogen Peroxide Decontamination: An Interrupted Time Series Analysis

Objectives The impact of surface disinfection versus detergent cleaning on healthcare associated infection rates remains unresolved. We aimed to evaluate the efficacy of hydrogen peroxide (HP) decontamination against methicillin-resistant Staphylococcus aureus (MRSA). Design Single centred retrospective before and after study design. Setting Launceston General Hospital, Tasmania, Australia. Participants Patients with MRSA infection or colonisation. Interventions Rooms occupied by patients with MRSA infection or colonisation were cleaned following discharge with either detergent or HP. Main outcome measures MRSA room contamination following cleaning; new MRSA acquisition in patients. ResultsOver 3600 discharge cleans were completed, with more than 32 600 environmental swabs processed. MRSA was isolated from 24.7% rooms following detergent cleaning and from 18.8% of rooms after HP (p Conclusions Use of HP disinfection led to a decrease in residual MRSA contamination in patient rooms compared with detergent. It may also have encouraged the reduction in patient MRSA acquisition despite several confounders including staff feedback on terminal cleaning, additional MRSA screening and quicker laboratory methods. Infection control is best served by concurrent interventions targeting both the patient and healthcare environment

The population biology of the living coelacanth studied over 21 years

Between 1986 and 2009 nine submersible and remote-operated vehicle expeditions were carried out to study the population biology of the coelacanth Latimeria chalumnae in the Comoro Islands, located in the western Indian Ocean. Latimeria live in large overlapping home ranges that can be occupied for as long as 21 years. Most individuals are confined to relatively small home ranges, resting in the same caves during the day. One hundred and forty five coelacanths are individually known, and we estimate the total population size of Grande Comore as approximately 300–400 adult individuals. The local population inhabiting a census area along an 8-km section of coastline remained stable for at least 18 years. Using LASER-assisted observations, we recorded length frequencies between 100 and 200 cm total length and did not encounter smaller-bodied individuals (\100 cm total length). It appears that coelacanth recruitment in the observation areas occur mainly by immigrating adults. We estimate that the mean numbers of deaths and newcomers are 3–4 individuals per year, suggesting that longevity may exceed 100 years. The domestic fishery represents a threat to the long-term survival of coelacanths in the study area. Recent changes in the local fishery include a decrease in the abundance of the un-motorized canoes associated with exploitation of coelacanths and an increase in motorized canoes. Exploitation rates have fallen in recent years, and by 2000, had fallen to lowest ever reported. Finally, future fishery developments are discussed

Observations on the brain of the coelacanth Latimeria chalumnae : External anatomy and quantitative analysis

New data on the brain of Latimeria indicate that previous estimates of the brain weight were too high by a factor of two. Our data suggest a brain weight of 1.1-1.5 grams for a specimen with a body weight of 30 kilograms. Quantitative data on major divisions of the brain are presented for the first time, and the relative size of the major brain divisions is similar to that of sturgeons and generalized sharks (such as hexanchids and squalids). Examination of brain component weight (s): body weight plots in a sample of non-teleost actinopterygian fishes indicates that all major divisions of the brain, except the telencephalon, are larger than in Latimeria. Brain component sizes in Latimeria are more similar to those extrapolated for amphibian brains than to those for actinopterygians. However, the cerebellum of Latimeria is considerably larger than that of amphibians.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50270/1/1051550205_ftp.pd

Retinal Specializations In The Eyes Of Deep-Sea Teleosts

Although living beyond the penetration limits of sunlight, many deep-sea teleosts possess large eyes, lenses capable of accommodation, and various adaptations for increasing sensitivity and extending their visual field. However, little is known of the extent of the visual field and whether the spatial resolving power of the eye is constant across the retina. In order to examine whether these fish are specialized for acute vision in particular regions of the visual field, retinal wholemounts were used to examine the regional differences in the density of retinal ganglion cells in 16 species from different depths, habitats and photic zones. It was found that the retinal ganglion cell topography changes markedly across the retina with a density range of 6.3-50.6 x 10/3 cells mm -2 in a pattern unique to each species. A number of mesopelagic species including the lanternfishes, Lampanyctus macdonaldi and Myctophum punctatum possess a concentric increase in cell density towards the retinal margins, putatively enhancing peripheral vision. Three tubular-eyed species including Scopelarchus michaelsarsi possess an area centralis in the centro-lateral region of the main retina supporting the premise that this specialization receives a focused image. Some benthic species such as the smoothhead Rouleina attrita and the searsid Searsia koefoedi also boast a structural specialization or fovea in temporal retina with centro-peripheral cell gradients exceeding 30:1. Benthic species such as the tripodfish Bathypterois dubius possess two regional increases in ganglion cell density or areae centrales, one nasal and the other temporal, thereby increasing spatial resolving power in the caudal and rostral visual fields, respectively. These quantitative analyses suggest that deep-sea fishes, like their shallow-water counterparts, also use a specific region of their visual field for acute vision. This may be an advantage for the detection and localization of bioluminescent light sources

Caracterización citológica de hepatopatías en perros y gatos

Diferentes técnicas diagnósticas complementarias se han aplicado durante losúltimos años en medicina veterinaria. Debido a su implementación se han realizado diagnósticosnovedosos en animales, pero aún es necesario determinar sensibilidad y especificidadde las mismas. Para la evaluación de las enfermedades hepáticas se dispone fundamentalmentede técnicas no invasivas, como las pruebas bioquímicas, la ultrasonografía y otras.La realización de biopsias es fundamental en muchos casos para determinar la causa o elpronóstico de las alteraciones encontradas, por lo cual todas estas técnicas deben considerarsecomo parte de un sistema de diagnóstico integrado. Se describen aquí los resultadosde la realización de la técnica de punción con aguja fina guiada por ecografía, aplicada aveintidós pacientes con sintomatología hepática, que concurrieron al Hospital de Clínicas dela Facultad de Ciencias Veterinarias de la UNNE durante el primer semestre del año 2007.Se detallan hallazgos citológicos significativos para la caracterización de diferentes hepatopatíasen perros y gatos

Retinal oxygen supply shaped the functional evolution of the vertebrate eye

The retina has a very high energy demand but lacks an internal blood supply in most vertebrates. Here we explore the hypothesis that oxygen diffusion limited the evolution of retinal morphology by reconstructing the evolution of retinal thickness and the various mechanisms for retinal oxygen supply, including capillarization and acid-induced haemoglobin oxygen unloading. We show that a common ancestor of bony fishes likely had a thin retina without additional retinal oxygen supply mechanisms and that three different types of retinal capillaries were gained and lost independently multiple times during the radiation of vertebrates, and that these were invariably associated with parallel changes in retinal thickness. Since retinal thickness confers multiple advantages to vision, we propose that insufficient retinal oxygen supply constrained the functional evolution of the eye in early vertebrates, and that recurrent origins of additional retinal oxygen supply mechanisms facilitated the phenotypic evolution of improved functional eye morphology