The cytochrome c oxidase subunit I (cox1) gene is the main mitochondrial molecular marker playing a pivotal role in phylogenetic research and is a crucial barcode sequence. Folmer’s “universal” primers designed to amplify this gene in metazoan invertebrates allowed quick and easy barcode and phylogenetic analysis. On the other hand, the increase in the number of studies on barcoding leads to more frequent publishing of incorrect sequences, due to amplification of non-target taxa, and insufficient analysis of the obtained sequences. Consequently, some sequences deposited in genetic databases are incorrectly described as obtained from invertebrates, while being in fact bacterial sequences. In our study, in which we used Folmer’s primers to amplify COI sequences of the crustacean fairy shrimp Branchipus schaefferi (Fischer 1834), we also obtained COI sequences of microbial contaminants from Aeromonas sp. However, when we searched the GenBank database for sequences closely matching these contaminations we found entries described as representatives of Gastrotricha and Mollusca. When these entries were compared with other sequences bearing the same names in the database, the genetic distance between the incorrect and correct sequences amplified from the same species was c.a. 65%. Although the responsibility for the correct molecular identification of species rests on researchers, the errors found in already published sequences data have not been re-evaluated so far. On the basis of the standard sampling technique we have estimated with 95% probability that the chances of finding incorrectly described metazoan sequences in the GenBank depend on the systematic group, and variety from less than 1% (Mollusca and Arthropoda) up to 6.9% (Gastrotricha). Consequently, the increasing popularity of DNA barcoding and metabarcoding analysis may lead to overestimation of species diversity. Finally, the study also discusses the sources of the problems with amplification of non-target sequences.

16S rRNA gene-based metagenomic analysis of the gut microbial community associated with the DUI species Unio crassus (Bivalvia: Unionidae)A short running title: Metagenomic analysis of bivalve gut microbiome

Erpobdella borisi n. sp. is a predatory leech inhabiting cave waters in Iran. Probably, it is either a troglobiont or troglophile. The leech has no eyes, and the complete mid-body somite is divided unequally into five annuli. Results of phylogenetic analysis based on morphological characters and COI gene sequence indicate the species to be closely related to Erpobdella japonica, E. octoculata and E. testacea.

Scientific diving is increasingly being used for numerous studies. Moreover, this form of diving allows for the conduction of interdisciplinary research. The current nomenclature of this type of dive is defined as scuba diving to collect information to support science by using diving techniques. Underwater research is particularly important in the natural sciences where it allows for the non-invasive observations of fauna and flora of aquatic ecosystems in their natural environment. At the same time, the use of diving for scientific purposes avoids mistakes made in random sampling, which is related to the use of classical sampling methods. As a result, such diving is crucial in systematic, ecological and behavioural analysis. Nevertheless, dive techniques, however versatile, require optimisation, separate study and systematisation, depending on the type of research conducted. This article is an attempt to present an outline of the topic, to systematise basic concepts in presenting the principles of legal regulations in Poland and abroad..