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Quantitative analysis of organismal form is an important component for almost every branch of biology. Although generally considered an easily-measurable structure, the quantification of gastropod shell form is still a challenge because shells lack homologous structures and have a spiral form that is difficult to capture with linear measurements. In view of this, we adopt the idea of theoretical modelling of shell form, in which the shell form is the product of aperture ontogeny profiles in terms of aperture growth trajectory that is quantified as curvature and torsion, and of aperture form that is represented by size and shape. We develop a workflow for the analysis of shell forms based on the aperture ontogeny profile, starting from the procedure of data preparation (retopologising the shell model), via data acquisition (calculation of aperture growth trajectory, aperture form and ontogeny axis), and data presentation (qualitative comparison between shell forms) and ending with data analysis (quantitative comparison between shell forms). We evaluate our methods on representative shells of the genus Opisthostoma, which exhibit great variability in shell form. The outcome suggests that our method is a robust, reproducible, and versatile approach for the analysis of shell form. Finally, we propose several potential applications of our methods in functional morphology, theoretical modelling, taxonomy, and evolutionary biology.
The first version of this manuscript was submitted to PeerJ on December 16, 2013 and has gone through three rounds of peer-review (January 2, 2014, March 4, 2014 & July 21, 2014). This version is the same as the second version which the Materials and Methods and Results and Discussions have been expanded based on the reviewers and editor constructive comments. In addition, the references list was updated. This paper was rejected by editor and reviewers (July 21, 2014). Please find the attached supplementary files for peer-review history. Any comments and suggestions are welcomed.
A complete peer-review history from December 16, 2013 - July 21, 2014
This file consists of all reviewer's report, rebuttal letters, and track change file of the three rounds of peer-review (January 2, 2014, March 4, 2014 & July 21, 2014). This manuscript has been improved by constructive comments from editor and reviewers. However, we could not agree to follow all the suggestion of reviewers and editor. Thus, this paper was rejected by editor and reviewers (July 21, 2014).