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Cryptic species complexes represent an important challenge for the adequate characterization of Earth's biodiversity. Oceanic organisms tend to have greater unrecognized cryptic biodiversity since the marine realm was often considered to lack hard barriers to genetic exchange. Here, we tested the effect of several Atlantic and Mediterranean oceanic barriers on 16 morphospecies of oceanic squids of the orders Oegopsida and Bathyteuthida using three mitochondrial and one nuclear molecular marker and five species delimitation methods. Number of species recognized within each morphospecies differed among different markers and analyses, but we found strong evidence of cryptic biodiversity in at least four of the studied species (Chtenopteryx sicula, Chtenopteryx canariensis, Ancistrocheirus lesueurii, and Galiteuthis armata). There were highly geographically structured units within Helicocranchia navossae that could either represent recently diverged species or population structure. Although the species studied here can be considered relatively passive with respect to oceanic currents, cryptic speciation patterns showed few signs of being related to oceanic currents. We hypothesize that the bathymetry of the egg masses and duration of the paralarval stage might influence the geographic distribution of oceanic squids. Because the results of different markers and different species delimitation methods are inconsistent and because molecular data encompassing broad geographic sampling areas for oceanic squids are scarce and finding morphological diagnostic characters for early life stages is difficult, it is challenging to assess the species boundaries for many of these species. Thus, we consider many to be in the "grey speciation zone." As many oceanic squids have cosmopolitan distributions, new studies combining genomic and morphological information from specimens collected worldwide are needed to correctly assess the actual oceanic squid biodiversity., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology.)

The Sebastes inermis complex includes three sympatric species ( Sebastes cheni , viz Sebastes inermis , and Sebastes ventricosus ) with clear ecomorphological differences, albeit incomplete reproductive isolation. The presence of putative morphological hybrids (PMH) with plausibly higher fitness than the parent species indicates the need to confirm whether hybridization occurs within the complex. In this sense, we assessed the dynamics of genetic divergence and hybridization within the species complex using a panel of 10 microsatellite loci, and sequences of the mitochondrial control region (D-loop) and the intron-free rhodopsin (RH1) gene. The analyses revealed the presence of three distinct genetic clusters, large genetic distances using D-loop sequences, and distinctive mutations within the RH1 gene. These results are consistent with the descriptions of the three species. Two microsatellite loci had signatures of divergent selection, indicating that they are linked to genomic regions that are crucial for speciation. Furthermore, nonsynonymous mutations within the RH1 gene detected in S. cheni and "Kumano" (a PMH) suggest dissimilar adaptations related to visual perception in dim-light environments. The presence of individuals with admixed ancestry between two species confirmed hybridization. The presence of nonsynonymous mutations within the RH1 gene and the admixed ancestry of the "Kumano" morphotype highlight the potential role of hybridization in generating novelties within the species complex. We discuss possible outcomes of hybridization within the species complex, considering hybrid fitness and assortative mating. Overall, our findings indicate that the genetic divergence of each species is maintained in the presence of hybridization, as expected in a scenario of speciation-with-gene-flow., Competing Interests: The authors declare that they have no competing interests., (© 2023 Deville et al.)

Mothocya parvostis (Isopoda: Cymothoidae) is a parasitic crustacean that infests the opercular cavities of fishes. Its main final host is the Japanese halfbeak, Hyporhamphus sajori . However, M. parvostis also infests the black sea bream, Acanthopagrus schelgelii , as an optional intermediate host. Understanding the use of optional intermediate hosts is important for understanding the life history of Cymothoidae, and further information should be obtained. In this study, we aim to investigate the life cycle of M. parvostis . We collected and examined 20 mancae and 144 juveniles of M. parvostis from 129 cobaltcap silversides, Hypoatherina tsurugae , and 494 yellowfin seabreams, Acanthopagrus latus . Molecular analysis of the cytochrome c oxidase subunit I gene and 16S rRNA genes revealed that cymothoid mancae and juveniles from the two fish species were identified to be M. parvostis . All M. parvostis on H. tsurugae and A. latus might be mancae or juveniles, with no adult parasites; thus, H. tsurugae and A. latus juveniles were optional intermediate hosts of M. parvostis . In the results of morphological description, M. parvostis juveniles infesting the final host H. sajori lacked swimming setae, while juveniles parasitizing the two optional intermediate hosts had them. Mothocya parvostis mancae infested juveniles of both species just after metamorphosis, grew with the host. As the fish grows further, the parasite detached from the fish. The parasitic status of M. parvostis in the three optional intermediate hosts indicated that M. parvostis likely reproduced from June to December, and different optional intermediate hosts were used depending on the time of year in Hiroshima Bay. Therefore, a parasitic strategy involving optional intermediate hosts might increase the infestation success of M. parvostis to H. sajori .

Cymothoid parasitic isopods infest a wide range of fish of different taxa living in marine, brackish, and freshwater environments. Most research on the reproductive season of Cymothoidae has been done by collecting or monitoring host fish afflicted with cymothoid parasites. However, collecting ecological data on cymothoid species that infest non-commercial or endangered fishes is complex and challenging. We used a quatrefoil light trap to investigate the seasonal change in species composition of cymothoid free-swimming stages in the Seto Inland Sea, Japan. We also collected preliminary data for efficient light-trap sampling and showed its effectiveness in cymothoid-related research. From October 2020 to December 2021, 613 cymothoid free-swimming stages were sampled monthly. All obtained individuals were identified as Mothocya parvostis (596), Ceratothoa verrucosa (12), and Ceratothoa carinata (5) by DNA barcoding using cytochrome c oxidase subunit I and 16S rRNA gene sequences. Based on the number of M. parvostis mancae collected each month, M. parvostis was anticipated to reproduce from June to December, with two reproduction peaks each year, and C. verrucosa and C. carinata were expected to reproduce in June, July, and September, and September and October, respectively. In addition, free-swimming juveniles were captured, presumably after they had left their optional intermediate hosts. Furthermore, the most effective time to harvest cymothoids with light traps may be during high tide on the night of the new moon. This study serves as a methodological framework for future research on cymothoids using light traps., Competing Interests: HF, KK, DD, and TU declare that they have no conflict of interest., (© 2022 The Authors.)

The embryonic development times, spawning timing and hatching rates of the black sea bream Acanthopagrus schlegelii were examined to investigate the potential effect of seawater temperature, tides and photoperiod on the reproductive rhythm of this species in Hiroshima Bay, Japan. Low temperatures decreased hatching rates and extended the hatching time, and the minimum temperature threshold for hatching was 15°C. Back-calculated spawning times indicated that the peak of spawning occurred just before sunset and the reduction in diurnal light intensity around the oyster rafts acted as a trigger for spawning. In contrast, no correlation was found between spawning rhythms and tidal cycle. The results highlight the important role of oyster farms in the reproductive cycle and population dynamics of A. schlegelii in Hiroshima Bay, the main spawning ground for this species in Japan. The study findings provide insights for the sustainable management of this important sparid species., (© 2022 Fisheries Society of the British Isles.)

Recent characterization of the whole saliva proteome led to contradictory pictures concerning the complexity of its proteome. In this work, 110 proteins were analysed by mass spectrometry allowing the identification of 10 accessions previously not detected on protein two-dimensional maps, including myosin heavy chain (fast skeletal muscle, IIA and IIB), phosphatidylethanolamine binding protein, secretory actin-binding protein precursor and triosephosphate isomerase. Further comparison with available data demonstrated simultaneously a low diversity in terms of variety of accessions and a high complexity in terms of number of protein spots identifying the same accession, the two thirds of identified spots corresponding to amylases, cystatins and immunoglobulins. This diversity may be of interest in the development of non invasive diagnostic tool for several disease.