Browsing by Author "Debus, L."

The sturgeon microsatellite LS-39 was amplified across 10 different species of Acipenserinae and exhibited the potential to identify the black caviar producer Acipenser stellatus on a genomic DNA level. This was because of a fixed allele of 111 bp, which was absent in the other species which were investigated. Concerning the source of sturgeon species, LS-39 is the first nuclear marker described to examine black caviar. Furthermore, new light is shed on the controversial ploidy state of sturgeons. The present authors findings at this microsatellite locus support the hypothesis that extant similar to 120 chromosomal species are modern diploids, whereas sturgeons with similar to 240 chromosomes should be considered as modern tetraploids.

The aim of this study was to develop and establish a molecular method for species identification of sturgeon products, esp. black caviar, used in the international trade. Sequences of the entire cytochrome b (cytb) gene from 858 fish specimens were used for discriminating between 22 sturgeon species, and potential species-specific restriction sites were determined. No single restriction endonuclease can be used for the differentiation of all species. Depending on the species, from one to four different enzymes are necessary for species identification. Overall, using seven different restriction endonucleases, 17 acipen-seriform species can be separated on the mtDNA level on the basis of characteristic species-specific restriction patterns. Three species of the genus Scaphirhynchus (S. albus, S. platorhynchus and S. suttkusi), as well as Acipenser gueldenstaedti and A. persicus, were not differentiated. Our approach provides an opportunity to identify and control the trade in sturgeon products outside of the three main caviar producing species, A. gueldenstaedti, A. stellatus, and Huso huso. Besides the trade, the method is important for the management and conservation programs. The necessity to combine nuclear and mtDNA markers for more precise identification is also discussed. The following hybrids were observed using mitochondrial and nuclear markers: one A. gueldenstaedtilA. stellatus hybrid, one A. gueldenstaedtil Acipenser ruthenus hybrid, five hybrids between A. gueldenstaedti or A. persicus and A. nudiventris.

Eleven of 34 sturgeons caught in the River Volga classified morphologically as Acipenser gueldenstaedtii were identified as Acipenser baerii from sequence analysis of the mitochondrial cytochrome-b gene. The Caspian Sea and its tributaries including the Volga are not native habitats of A. baerii No A. baerii haplotype was observed in A. gueldenstaedtii from the Sea of Azov or the South Caspian Sea. Genetic contamination of A. gueldenstaedtii with A. baerii or A. baerii hybrids has occurred in the Volga. Crosses and backcrosses of these specimens with native A. gueldenstaedtii resulted in the loss of the morphological diagnostic A. baerii features. These findings are of special concern for conservation and management programmes, as well as for specimen identification for caviar trading control.

Data from 1238 fishes from 19 sturgeon species and 1 paddlefish were used to analyze heteroplasmy in sturgeon. Lengths of central repeat units ranged from 74 to 83 bp among sturgeon species. No repeat sequence was found in the paddlefish, Polyodon spathula. A general feature of the repeat units was the presence of termination associated sequence (TAS) motifs. About 50% of 138 interspecific mutations observed among the D-loop sequences are located 10 bp down- and upstream from these TAS motifs. Interestingly, most homoplasmic species showed deletions upstream to the TAS motifs, whereas deletions downstream to the TAS motifs: observed in two species do not seem to preclude heteroplasmy. Calculations of secondary structures and thermal stabilities of repeat units showed DeltaG values for all heteroplasmic species to be <-8 and for most homoplasmic species G value to be >-8. Most heteroplasmic fishes had two and/or three repeat units. No homoplasmic sturgeon with >2 repeat units were observed. Molecular phylogeny based on the entire cytochrome b showed that heteroplasmy probably resulted fr om a single evolutionary event. Our data demonstrate that heteroplasmy is present in most sturgeon species and suggest that the thermal stability of the secondary structure of the repeat unit in combination with mutations downstream of the TAS sequences influences heteroplasmy.