Abstract
An account is given of the karyotypes of Hydramagnipapillata Itô, 1947, H.oxycnida Schulze, 1914, and Pelmatohydraoligactis (Pallas, 1766) (Cnidaria, Hydrozoa, Hydridae). A number of different techniques were used: conventional karyotype characterization by standard staining, DAPI-banding and C-banding was complemented by the physical mapping of the ribosomal RNA (18S rDNA probe) and H3 histone genes, and the telomeric (TTAGGG)n sequence by fluorescence in situ hybridization (FISH). We found that the species studied had 2n = 30; constitutive heterochromatin was present in the centromeric regions of the chromosomes; the “vertebrate” telomeric (TTAGGG)n motif was located on both ends of each chromosome and no interstitial sites were detected; 18S rDNA was mapped on the largest chromosome pair in H.magnipapillata and on one of the largest chromosome pairs in H.oxycnida and P.oligactis; in H.magnipapillata, the major rRNA and H3 histone multigene families were located on the largest pair of chromosomes, on their long arms and in the centromeric areas respectively. This is the first chromosomal mapping of H3 in hydras.
Highlights
Hydras are simple freshwater invertebrates belonging to one of the most ancient members of the animal kingdom, the phylum Cnidaria
The karyotype was found to consist of 30 m/sm chromosomes (2n = 30), it is symmetrical in structure, with chromosomes showing a regular gradation in size
Basic features of karyotypes revealed here in Hydra magnipapillata, H. oxycnida, and Pelmatohydra oligactis agree with those reported for these species previously (Anokhin and Kuznetsova 1999; Anokhin and Nokkala 2004; Anokhin et al 2010)
Summary
Hydras are simple freshwater invertebrates belonging to one of the most ancient members of the animal kingdom, the phylum Cnidaria (class Hydrozoa, order Hydrida, family Hydridae). Some species of hydras are relatively easy animals to culture and maintain in the laboratory, they have been used as model organisms in many different areas of biological research, primarily in developmental biology often referred to as “evo-devo”, i.e. evolutionary developmental biology research (Slobodkin and Bossert 2001; Galliot 2012). Jankowski et al (2008) suggested 12– 15 really different hydra species, whereas Bouillon et al (2006) reported approximately 30 valid species, and the World Register of Marine Species lists 40 species (Schuchert 2018). Schulze (1914, 1917) divided hydras into three genera, Hydra, Chlorohydra Schulze, 1914, and Pelmatohydra Schulze, 1914, and their validity was substantiated elsewhere Schulze (1914, 1917) divided hydras into three genera, Hydra, Chlorohydra Schulze, 1914, and Pelmatohydra Schulze, 1914, and their validity was substantiated elsewhere (e.g. Collins 2000; Stepanjants et al 2000; Anokhin 2002)
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