Anchita Casaubon

The molecular operational taxonomic unit (MOTU) Macrostylis sp. ML08 was particularly abundant in samples from the abyssal depths of the Vema Fracture Zone (VFZ) in the Atlantic Ocean. This MOTU exhibited an extensive distribution spanning thousands of kilometers across the Mid-Atlantic Ridge and was common and abundant in samples from the eastern VFZ, but rare in samples from the western VFZ. An earlier phylogenetic reconstruction based on 16S mitochondrial DNA (mtDNA) identified M. ML08 as a potential species complex. The present study used an integrative approach combining molecular genetics and geometric morphometrics to show that M. ML08 is a species complex comprising seven new species. The M. ML08 species complex is further characterized by extreme sexual dimorphism.

During the KH-23–5 expedition aboard the RV Hakuho Maru to the Kuril-Kamchatka (KKT) and Japan Trenches (JT) in September 2023, we deployed bottom trawls equipped with plankton nets, resulting in a high number of supra- and epibenthic benthic organisms, particularly of isopod crustaceans (Peracarida, Malacostraca). In total, we sampled 2656 specimens of Isopoda spanning at least 14 families and the suborder Epicaridea across 28 stations. Notably, five families were represented by more than 100 specimens each: Munnopsidae led with the highest number of specimens (1123 individuals), followed by Haploniscidae with 564, Macrostylidae with 430, Ischnomesidae with 245, and Desmosomatidae with 188 individuals. Station C8 yielded the highest number of individuals (502), while only one isopod was retrieved from station F11. Our findings document the efficacy of employing additional plankton nets,and we recommend the increased use of bottom trawls deployed with plankton nets in future expeditions.

Snapping shrimps of the genus Alpheus Fabricius, 1798 exhibit remarkable diversity, with over 300 described species. The genus is well-known for its prevalence of species complexes, necessitating the need of new tools to facilitate species discrimination. Traditional taxonomic methods in Alpheus have primarily relied on the examination of morphological traits or comparative morphometric measurements, with an emphasis on variation in the major chela and rostro-orbital region. We applied an integrated approach that combines molecular genetics and geometric morphometrics to investigate the A. gracilipes Stimpson, 1860 species complex. We additionally applied geometric morphometric techniques to study the major chela and the rostrum across different species, and used three mitochondrial genes (12S, COI, and 16S) to reconstruct phylogenetic relationships of this complex. Our results demonstrate the first application of geometric morphometric techniques to Alpheus snapping shrimps, and highlight the significance of the major chela and rostrum as taxonomically informative traits. Furthermore, we use DNA barcodes and geometric morphometric techniques to the A. gracilipes species complex to reveal two previously unidentified cryptic species. We present the first phylogenetic reconstruction of this species complex, with new localities and expanded distribution ranges reported for many species.