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1.
The sex and stage of gonadal development of longfinned river eels Anguilla reinhardtii , captured from nine river catchments in New South Wales, Australia, between 1999 and 2001, were determined macroscopically. Sex was verified by histology. Histology was also necessary, however, to accurately define stages of gonadal development, particularly in individuals <600 mm in total body length. Anguilla reinhardtii displayed asynchronous gamete development. The most advanced cells present in migrating male and female A. reinhardtii were spermatocytes and pre-vitellogenic oocytes, respectively. Gonadal development stages were positively correlated with body size in both sexes. Females, however, were significantly larger than males and their gonads matured over a broader size range. Size at sexual differentiation (42–60 cm for males and 50–76 cm for females) was much larger than for most other anguillids that have been studied, with the exception of the New Zealand longfinned eel Anguilla dieffenbachii . Corresponding with its large range in size at sexual differentiation was a relatively large range in size at migration for both males (44–62 cm) and females (74–142 cm). 相似文献
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D C Pease 《Journal of ultrastructure research》1966,14(3):379-390
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The first recorded incidence of dicephalia in a bull shark Carcharhinus leucas is reported from a foetus collected by a fisherman in the Gulf of Mexico near Florida, U.S.A. External examination, Radiography and magnetic resonance imaging revealed a case of monosomic dicephalia where the axial skeleton and internal organs were found to divide into parallel systems anterior to the pectoral girdle resulting in two well‐developed heads. 相似文献
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James B. Pease Matthew W. Hahn 《Evolution; international journal of organic evolution》2013,67(8):2376-2384
When speciation events occur in rapid succession, incomplete lineage sorting (ILS) can cause disagreement among individual gene trees. The probability that ILS affects a given locus is directly related to its effective population size (Ne), which in turn is proportional to the recombination rate if there is strong selection across the genome. Based on these expectations, we hypothesized that low‐recombination regions of the genome, as well as sex chromosomes and nonrecombining chromosomes, should exhibit lower levels of ILS. We tested this hypothesis in phylogenomic datasets from primates, the Drosophila melanogaster clade, and the Drosophila simulans clade. In all three cases, regions of the genome with low or no recombination showed significantly stronger support for the putative species tree, although results from the X chromosome differed among clades. Our results suggest that recurrent selection is acting in these low‐recombination regions, such that current levels of diversity also reflect past decreases in the effective population size at these same loci. The results also demonstrate how considering the genomic context of a gene tree can assist in more accurate determination of the true species phylogeny, especially in cases where a whole‐genome phylogeny appears to be an unresolvable polytomy. 相似文献
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Sarah Louise Mackie Rodney Hughes Margaret Walsh John Day Marion Newton Colin Pease John Kirwan Marianne Morris 《PloS one》2015,10(5)
Objectives
To explore patients’ concepts of stiffness in polymyalgia rheumatica (PMR), and how they think stiffness should be measured.Methods
Eight focus groups were held at three centres involving 50 patients with current/previous PMR. Each group had at least one facilitator and one rapporteur making field notes. An interview schedule was used to stimulate discussion. Interviews were recorded, transcribed and analysed using an inductive thematic approach.Results
Major themes identified were: symptoms: pain, stiffness and fatigue; functional impact; impact on daily schedule; and approaches to measurement. The common subtheme for the experience of stiffness was “difficulty in moving”, and usually considered as distinct from the experience of pain, albeit with a variable overlap. Some participants felt stiffness was the “overwhelming” symptom, in that it prevented them carrying out “fundamental activities” and “generally living life”. Diurnal variation in stiffness was generally described in relation to the daily schedule but was not the same as stiffness severity. Some participants suggested measuring stiffness using a numeric rating scale or a Likert scale, while others felt that it was more relevant and straightforward to measure difficulty in performing everyday activities rather than about stiffness itself.Conclusions
A conceptual model of stiffness in PMR is presented where stiffness is an important part of the patient experience and impacts on their ability to live their lives. Stiffness is closely related to function and often regarded as interchangeable with pain. From the patients’ perspective, visual analogue scales measuring pain and stiffness were not the most useful method for reporting stiffness; participants preferred numerical rating scales, or assessments of function to reflect how stiffness impacts on their daily lives. Assessing function may be a pragmatic solution to difficulties in quantifying stiffness. 相似文献9.
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