Importance of Nematocysts in Taxonomy of Acontiarian Sea Anemones (Cnidaria, Actiniaria): A Statistical Comparative Study

Many papers describe the cnidae from acontiarian sea anemone species, but comparative studies involving significant data amounts, combined with adequate statistical treatment have not been realized. The aim of the present paper is to carry out a comparative study of acontian cnidae from the species Haliplanella lineata (Verrill, 1869), Tricnidactis errans Pires, 1988 (Haliplanellidae) and Anthothoe chilensis (Lesson, 1830) (Sagartiidae). Five living specimens of each species were used; the length of 50 unfired capsules was measured and taken randomly from the following nematocyst categories: b-rhabdoids, p-rhabdoids B1b, p-rhabdoids B2a. A total of 2,000 measurements was done. The data were analyzed with descriptive statistics (mean, standard deviation, median, maximum, minimum, and semiinterquartile range) and Shapiro-Wilks test, Box-Cox transformation, Kruskal-Wallis test and single factor ANOVA. The normal distribution of the dataset must be tested for each nematocyst type in any quantitative study of the cnidae. We conclude that variation in nematocyst size should not be used as an element of conclusive value in the diagnosis of species of acontiarian sea anemones. For these purposes, other characters have to be used to define precisely each taxon, including qualitative variation of the cnidae.