Tremoctopods are epipelagic argonautoid octopods characterized by their expanded dorsal webs and strong sexual size dimorphism, with dwarfed males. The scarcity of taxonomic features attributed to this genus presents a challenge, and there is growing evidence of species misidentification in Tremoctopus genus on a molecular level. In this study, we investigated four female specimens of blanket octopus Tremoctopus violaceus caught by purse seine fishing in the Central Eastern Adriatic Sea in 2019. Individuals had smooth, firm and muscular bodies, dark bluish purple on the dorsal and iridescent silvery on the ventral side, with dorsal mantle lengths of 113, 82, 80 and 78 mm. The constructed phylogenetic trees based on the 16S ribosomal RNA and cytochrome c oxidase subunit I sequences of investigated Adriatic specimens and publicly available sequences showed strong support for the T. violaceus clade, consisting of individuals collected from the Adriatic Sea, Mediterranean Sea and Atlantic Ocean, with the exclusion of Indo-Pacific clade most probably corresponding to T. gracilis. To fully understand the life-history traits of Tremoctopus species, future research should focus on DNA-based methods for correct species identification combined with morphological characters, geographic distribution and ecological information.

This study gives the first data on the body and beak morphometric characteristics, age, and genetic structure of neon flying squid, a rarely caught cephalopod in the Adriatic Sea. We identified specimens as recently resurrected Ommastrephes caroli species using two mitochondrial markers, 16S ribosomal RNA gene and cytochrome c oxidase subunit I gene. Overall, 23 juveniles (3 females, 3 males, and 17 unsexed), with a dorsal mantle range of 65–152 mm, were caught in September 2020 in the waters of the Korčula Channel, island of Palagruža, and island of Jabuka, thus providing the most abundant sample of this species in the Mediterranean waters. The length–weight relationship showed an isometric growth. The results of the beak/length regressions suggest hood length is a useful characteristic for biomass estimation studies, as it showed a good linear fit to the dorsal mantle length. Statolith growth increments were easily visible and statolith microstructure analysis was successfully used to determine the age of 22 individuals. The estimated age ranged from 36 to 64 days (mean = 48 days). The back-calculation analysis showed that the squid hatched during July and August 2020, indicating that O. caroli spawns during the warmer, summertime period. Considering the size and age of the caught individuals, the Adriatic Sea could represent a potential feeding ground for this species. The genetic structure analyses indicate the existence of separate Atlantic and Mediterranean/Adriatic subclusters; however, this warrants further investigation.

Background/Objectives: Non-indigenous species are increasingly reshaping Mediterranean marine ecosystems, particularly under ongoing climate warming. The rayed pearl oyster Pinctada radiata, a thermophilic species originating from the Indo-Pacific region, is one of the earliest and most successful invaders in the Mediterranean Sea and has recently established populations in the Adriatic Sea. Methods: This study integrates preliminary shell morphometric data with molecular genetic analyses based on mitochondrial cytochrome c oxidase subunit I (COI) and nuclear internal transcribed spacer 2 (ITS2) markers to confirm species identity and examine patterns of genetic variation in comparison with other Mediterranean Sea regions and the Persian Gulf. Results: Phylogenetic analyses based on COI confirmed P. radiata as a distinct and well-supported monophyletic lineage, whereas the nuclear ITS2 marker showed limited resolution and interspecific overlap. Mediterranean and Adriatic populations showed low COI haplotype and nucleotide diversity and weak genetic structuring, consistent with recent colonization and secondary expansion, whereas Persian Gulf populations were more genetically diverse. Conclusions: Future studies should employ larger sample sizes and broader geographic sampling across both the Mediterranean Sea and the full native range of P. radiata, combined with high-resolution genome-wide nuclear markers, to better resolve connectivity and invasion dynamics.