Composition, biometry and statistical relationships between the cnidom and body size in the sea anemone Oulactis muscosa (Cnidaria: Actiniaria)

Abstract

biometry and statistical relationships between the cnidom and body size in the sea anemone Oulactis muscosa (Cnidaria: Actiniaria) This study analyses the possible relationships between body size and length of cnidae from different tissues of the sea anemone Oulactis muscosa. We describe the cnidom, providing new qualitative and quantitative data. Our description adds spirocysts for tentacles and acrorhagi, and is more precise about the ranges and types of basitrichs, microbasic b-mastigophores, and holotrichs. We distinguish two types of holotrichs in the acrorhagi, and differentiate between microbasic b-mastigophores and basitrichs in the actinopharynx and mesenterial filaments. A relationship between cnida length and body weight was not demonstrated. The results are based on a complete account of cnida types from all tissues, and considering the great number of capsules measured (5400) and the modern statistical tools employed, we think that a normal distribution of cnida lengths is uncommon, perhaps refuted. This finding is very important when a quantitative analysis of cnidae is necessary and an adequate statistical tool must be used. We have shown that generalized linear models are an alternative and therefore analyses can be done with parametric methods despite the non-normal distribution of cnida size. The use of these statistical tools should be generalized since appropriate package for analyses (like the R package) are available from the web and the obtained results are robust and powerful.

Drifting in the oceans: Isarachnanthus nocturnus (Cnidaria, Ceriantharia, Arachnactidae), an anthozoan with an extended planktonic stage

“…Development stages described Carlgren (1924);Calabresi (1928);Nair (1944) Medusozoa the size of the cnidocyst may be useful in species discrimination, in Anthozoa this character is less useful due to the continuous growth of cnidocytes (e.g, Acuña et al 2011, for sea anemones); this problem may apply particularly to efforts directed at linking larvae to adults of ceriantharians. Furthermore, at least in sea anemones, the complex biometry of the cnidocysts is in part an impediment to their use in taxonomy (Acuña et al 2011).…”

“…Furthermore, at least in sea anemones, the complex biometry of the cnidocysts is in part an impediment to their use in taxonomy (Acuña et al 2011). In the case of Isarachnanthus maderensis and I. nocturnus, Stampar et al (2012) remarked that "the length of several cnida types of specimens from different areas and different species overlapped and provided weak resolution to distinguish among species."…”

Biometry of sea anemone and corallimorpharian cnidae: statistical distribution and suitable tools for analysis

“…Despite this standard procedure, the taxonomic value of cnidocysts is relative and variable; some families or genera of sea anemones can be characterized by the composition of cnidocysts (Fautin 1988(Fautin , 2009). Moreover, the value of cnidocyst characteristics at species level is weaker, mainly due to the usual intraspecific variation of cnidae sizes (Allcock et al 1998;Watts et al 2000;Ardelean and Fautin 2004;Francis 2004;Acuña et al 2003Acuña et al , 2004Acuña et al , 2007Ryland et al 2004), and in these situations the cnidome should be used to complement other characters in arriving at an identification (Acuña et al 2003).…”

“…Several studies have dealt with biometrics data of cnidae in different groups of anthozoans, such as Actiniaria, Corallimorpharia, and Zoanthidea (Thomason 1988;Williams 1996Williams , 1998Williams , 2000Chintiroglou et al 1997;Allcock et al 1998;Acuña et al 2004Acuña et al , 2007Ardelean and Fautin 2004;Ryland et al 2004;Francis 2004;Acuña and Garese 2009). Statistical treatments of this kind of data have been variable according to the evaluation of their normality and acceptance or rejection of it.…”

“…By contrast, other authors directly applied nonparametric test or did so before refusing normality of the data (Acuña et al 2003). Furthermore, more recent studies proposed alternative analysis, more powerful than nonparametric ones, such as the implementation of generalized linear models (GLMs) (Acuña et al 2004(Acuña et al , 2007Acuña and Garese 2009). Williams (1996Williams ( , 1998Williams ( , 2000 focuses specifically on statistical methods to compare cnidae size on sea anemones and concluded that actiniarian cnidocyst data follow a normal (Gaussian) distribution.…”