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      Morphological variations caused by fixation techniques may lead to taxonomic confusion in Laeonereis (Polychaeta: Nereididae)

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          Abstract

          The nereidid polychaete Laeonereis acuta (Treadwell, 1923) is either considered to be a valid species, or a synonym of Laeonereis culveri (Webster, 1879). The species epithet, acuta, refers to the acuminate anterior region of the body followed by a widening that is visible up to the 10th setiger. The relative width of the anterior region of the body, however, has been reported in the taxonomic literature as variable for Laeonereis Hartman, 1945, a genus known from the eastern coast of North America to Patagonia (southern South America). To test whether variations in this character are real, or whether they correspond to an artifact, we analyzed morphological changes associated with different anesthesia and fixation techniques regularly used to prepare specimens of Laeonereis from southern Brazil (formerly reported as L. acuta). Six treatments, including combinations of anesthetics and fixative agents, and a control, were evaluated in groups of 25 adult animals. A simple model II regression analysis on living specimens showed that the growth is approximately isometric. One-way ANOVA was used to compare the treatment effect on the ratio of peristome width: setiger 6 width. This ratio was smaller in non-anesthetized individuals, especially when prepared in formalin and freshwater. When anesthetized with menthol and fixed in formalin with sea water, individuals retained a shape that was closest to their in vivo shape. Consequently, our results suggest that fixation without prior anesthesia is not recommended for morphological and taxonomical studies. Since morphology and morphometrics of the anterior region are consistently influenced by preparation techniques, it is likely that inadequate fixation routines have introduced several errors in the taxonomic and ecological literature of Laeonereis.

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                Author and article information

                Journal
                zool
                Zoologia (Curitiba)
                Zoologia (Curitiba)
                Sociedade Brasileira de Zoologia (Curitiba, PR, Brazil )
                1984-4670
                1984-4689
                February 2010
                : 27
                : 1
                : 146-150
                Affiliations
                [01] Pontal do Paraná Paraná orgnameUniversidade Federal do Paraná orgdiv1Centro de Estudos do Mar Brasil
                [02] Niterói Rio de Janeiro orgnameUniversidade Federal Fluminense orgdiv1Instituto de Biologia orgdiv2Departamento de Biologia Marinha Brasil
                Article
                S1984-46702010000100022 S1984-4670(10)02700122
                10.1590/S1984-46702010000100022
                8544f615-883c-473e-ab02-edeb5484fae7

                This work is licensed under a Creative Commons Attribution 4.0 International License.

                History
                : 23 March 2009
                : 26 January 2010
                Page count
                Figures: 0, Tables: 0, Equations: 0, References: 25, Pages: 5
                Product

                SciELO Brazil

                Self URI: Full text available only in PDF format (EN)
                Categories
                Taxonomy and Nomenclature

                morphology,methodological errors,preparation techniques,Laeonereis acuta,Laeonereis culveri

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