Karyological investigation in natural hybrids of sturgeons of the lower Danube River and Black Sea

Ene AC. Suciu R. Danube Delta National and Development Institute Tulcea Adress: Babadag str. 165 Tulcea 8800, Romania

Four natural sturgeon hybrids were karyologically investigated. They were sampled in the Romanian sector of Danube River and Black Sea during 1996 - 2000. All of them were hybrids between the only octaploid species existing in Romanian waters, Acipenser gueldenstaedti (2n = 258±4) and tetraploid species H. huso and A. stellatus (2n = 118±2), respectively. Three hybrids (one A. gueldenstedti x Huso huso and two A. gueldenstaedti x A. stellatus) had an intermediate chromosome number (2n = 175 - 190) between tetraploid and octaploid species. The fourth one (A. gueldenstaedti x A. stellatus) had a non-intermediate chromosomal complement of 116-120. The hybrids A. gueldenstaedti x A. stellatus were morfologically distinct, representing three possible morphs of hybrids, already described by Antipa (1909). The aspect of morphological similarities between two snouts varieties of A. gueldenstaedti (var. acutirostris and var. longirostris) and two of the hybrids of A. gueldenstaedti (A. gueldenstaedti x Huso huso and one morph of A. gueldenstaedti x A. stellatus) is discussed. Karyologically investigations clearly indicate that two of the speeimens we investigated (A. gueldenstedti x Huso huso and one of the hexaploids A. gueldenstaedti x A. stellatus) are hybrids and not snout varieties of A. gueldenstaedti. According to our present knowledge, this is the first report on kariology in natural hybrids of sturgeons.