Abstract
We morphologically analyzed 79 cephalopod specimens from the North and Baltic Seas belonging to 13 separate species. Another 29 specimens showed morphological features of either
Alloteuthis mediaor
Alloteuthis subulata or were found to be in between. Reliable identification features to distinguish between
A. media and
A. subulata are currently not available. The analysis of the DNA barcoding region of the COI gene revealed intraspecific distances (uncorrected
p) ranging from 0 to 2.13 % (average 0.1 %) and interspecific distances between 3.31 and 22 % (average 15.52 %). All species formed monophyletic clusters in a neighbor-joining analysis and were supported by bootstrap values of ≥99 %. All COI haplotypes belonging to the 29
Alloteuthis specimens were grouped in one cluster. Neither COI nor 18S
rDNA sequences helped to distinguish between the different
Alloteuthis morphotypes. For species identification purposes, we recommend the use of COI, as it showed higher bootstrap support of species clusters and less amplification and sequencing failure compared to 18S. Our data strongly support the assumption that the genus
Alloteuthis is only represented by a single species, at least in the North Sea. It remained unclear whether this species is
A. subulata or
A. media. All COI sequences including important metadata were uploaded to the Barcode of Life Data Systems and can be used as reference library for the molecular identification of more than 50 % of the cephalopod fauna known from the North and Baltic Seas.