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Molecular identification and distribution of insect larvae in the Lower Danube River

Menabit Selma, Iancu Lavinia, Pavel Ana B., Popa Adrian, Lupascu Naliana, Purcarea Cristina

Oceanological and Hydrobiological Studies

2022

Vol. 51, No. 1

74--89

As a major component of freshwater ecosystems, insect species play an important role in nutrient cycling and are often used as bioindicators of water pollution. Although extensive studies have characterized insects from freshwater habitats, little is known about the distribution of these species along the Lower Sector of the Danube River. Therefore, this survey conducted in the Danube section within the Romanian territory aimed to identify insect larvae belonging to seven different species of Odonata, Trichoptera, Ephemeroptera, Lepidoptera and Megaloptera by DNA barcoding and to investigate their distribution, density and frequency. A total of 41 quantitative macrozoobenthic samples were collected during two consecutive years (2019 and 2020). Species showed large differences in the distribution and density along different sections, and an overall tendency to populate downstream areas, except for Sialis morio. On the other hand, only Hydropsyche bulgaromanorum, Triaenodes bicolor and S. morio larvae were identified in the upstream section (Sulina branch). These data provide baseline information on the larger range of some of the most common aquatic insects in the Romanian Danube section in relation to several environmental parameters based on the first molecular identification of these species using COI gene sequencing.

Characteristics of the grey seal (Halichoerus grypus) diet in the Vistula River mouth (Mewia Łacha Nature Reserve, southern Baltic Sea), based on the osteological and molecular studies of scat samples

Keszka Sławomir, Panicz Remigiusz, Stepanowska Katarzyna, Biernaczyk Marcin, Wrzecionkowski Konrad, Zybała Mikołaj

Oceanologia

2020

No. 62 (3)

387--394

The study analyses for the first time the diet composition of grey seals inhabiting the Polish Baltic Sea coast. Samples of seal scat were collected in the Mewia Łacha Nature Reserve at the mouth of the Vistula River. Using genetic and osteological methods, the remains of organisms included in the grey seals diet were analysed for their taxonomy (families and species). Based on the analysis of 49 scat samples from grey seals, 761 hard parts that could be identified by taxon were isolated. The predominant species in the samples were perch, Perca fluviatilis (almost 78% of samples); pikeperch, Sander lucioperca (67%); lamprey, Lampetra fluviatilis (almost 35% of samples); Baltic cod, Gadus morhua callarias (almost 31% of samples) and sea trout, Salmo trutta trutta (26.5%). Genetic analysis confirmed the presence of Atlantic cod DNA in 69% and sea trout in 63% of samples. The genetic material of the Atlantic herring, Clupea harengus has not been identified in the analysed scat samples. Information on grey seals feeding on river lampreys seems to be valuable in the context of lack of knowledge on the occurrence of lampreys in the Vistula River. The methodology used showed that seals fed on species that were the most abundant in the area which is directly associated with the migration cycle of fish. The results of our study allowed the conclusion that the grey seal is an opportunistic predator and its diet reflects and exploits the variations in its habitat.