Biometric and statistical investigations on the cnidoma of the genus Hydra (Cnidaria, Hydrozoa)

Maria I Deserti,Mauricio O Zamponi

doi:10.1590/s0073-47212012000300008

Maria I Deserti, Mauricio O Zamponi

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https://doi.org/10.1590/s0073-47212012000300008

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Abstract

This paper deals about the nematocysts like a source of biometric information for comparison between the species Hydra vulgaris Pallas, 1766, Hydra vulgaris pedunculata Deserti et al., 2011 and Hydra pseudoligactis (Hyman, 1931). This biometric tool lets us carry out statistical comparisons and adding these results to the identification of specimens from different classificatory groups. In this particular study, we obtained significant differences between species, individuals of each species and nematocysts type when compared the biometry of its nematocysts. Another result was the variation in of particular nematocysts, like atrichous isorhiza and holotrichous isorhiza for the species H. vulgaris in relation to the column size.

Highlights

This paper deals about the nematocysts like a source of biometric information for comparison between the species Hydra vulgaris Pallas, 1766, Hydra vulgaris pedunculata Deserti et al, 2011 and Hydra pseudoligactis (Hyman, 1931)
An inventory of all the cnidae types present in the tissues of a cnidarian is known as its cnidoma (Weill, 1926) but no information on cnidae size is implicit in this definition (Williams, 1998)
Standard deviation and range for the morphological variables height of column (HC) and HC/WC are shown in table I and for length, width and biometry parameter of nematocysts in table II

Summary

Introduction

This paper deals about the nematocysts like a source of biometric information for comparison between the species Hydra vulgaris Pallas, 1766, Hydra vulgaris pedunculata Deserti et al, 2011 and Hydra pseudoligactis (Hyman, 1931) This biometric tool lets us carry out statistical comparisons and adding these results to the identification of specimens from different classificatory groups. Itô (1951) found statistically significant differences in shapes and sizes of stenoteles and holotrichous isorhiza from populations of Hydra robusta (Itô, 1947) collected from widely separated localities, but this differences was not present for populations located in habitats more nearby (Forrest, 1963) This polyp has been used in many different fields of biology, yet the individual species themselves have been difficult to define (Martinez et al, 2010) and the taxonomy and phylogenetic relationships of the species within the genus have always been uncertain (Ewer, 1948)

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