Variance of Female Genital Shape in Spiny Dogfish, Squalus Acanthias, a 2-D and 3-D Approach
Date
2018-07-02
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Abstract
This study aimed to investigate the presence and significance of
morphological variation in the internal female genitalia of spiny dog sharks,
Squalus acanthias. We used traditional linear morphometrics to examine the
relationship between the allometry of the vagina and the allometry of the pectoral
fin; however due to small sample size we did not detect an allometric trend. We
used traditional 2-D and relatively new 3-D geometric morphometrics (GM) to
look for variations in genital shape correlated with changing reproductive state
(Visibly Pregnant vs. reproductive but Not Visibly Pregnant). Surprisingly, only
the 2-D analysis detected significant shape variation associated with reproductive
state, however it was only significant after two sets of error replicates were
included. This information suggests that further geometric morphometric analyses
should include two sets of error models to better understand and compare the
different degrees of variation detected by 2-D and 3-D methods. The data from
both the 2-D and 3-D GM analyses did show that vaginal size is significantly
correlated with shape—supporting the idea that as vaginal size increases the shape
of the vagina becomes wider and more open, likely to accommodate for birth.
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Keywords
Geometric Morphometrics, Squalus acanthias