ABSTRACT The Arabella iricolor species complex (Annelida: Oenonidae), inhabiting intertidal rocky shores worldwide, has been regarded as carnivorous; however, a taxonomic revision based on morphological and molecular evidence is required, and its feeding behaviour has not been documented in detail. Here, we report the nocturnal feeding behaviour of Arabella in Japan. Morphologically, it clearly differs from A. iricolor and is regarded as the same species as Arabella cf. iricolor from Korea. Furthermore, phylogenetic analysis based on mitochondrial COI gene sequences indicates that it is phylogenetically distant from A. iricolor from around the type locality. Although actual feeding was not observed during our survey, eight species belonging to Arthropoda, Mollusca, and Annelida were found enclosed within the mucus produced by Arabella cf. iricolor. Among them, the limpet Cellana toreuma (Patellogastropoda: Nacellidae) and the false limpet Siphonaria sirius (Heterobranchia: Siphonariidae) were covered with mucus secreted by Arabella cf. iricolor and their soft bodies were almost completely consumed by the worms. Given the wide geographic distribution of the A. iricolor species complex and its occasional abundance on rocky shores, predatory behaviour by Arabella represents a previously overlooked component of rocky shore food webs.

ABSTRACT The complex hydrography and coastal geomorphology of the Magellan region in Chilean Patagonia support a highly diverse yet largely unexplored benthic community. Establishing a baseline is essential for detecting future ecological change and informing conservation strategies. This study examines the spatial distribution of subtidal benthic communities in the Strait of Magellan. Megabenthic invertebrates were characterized across five localities along a depth gradient (5, 10, 15 and 20 m) using underwater photoquadrats. A total of 64 species were identified. PERMANOVA revealed no significant differences in community composition across depth, although species richness increased with depth. In contrast, significant differences were detected among localities, with Bell Bay showing the most distinct assemblage, largely driven by Arossia henryae (SIMPER). The high abundance of sessile species, including A. henryae, Magellania venosa, Didemnum studeri, Errina antarctica and Psolus sp., highlights the role of suspension feeders as ecosystem engineers that enhance habitat complexity and biodiversity. Cape San Isidro exhibited reduced sessile cover and extensive bare substrate, likely associated with environmental constraints. No clear depth-related pattern was observed for vagile species. These results emphasize the need to conserve these vulnerable subtidal habitats..

ABSTRACT This study examined the population genetic structure, connectivity, and demographic history of the mangrove snail, Terebralia palustris, along the coast of Tanzania through mitochondrial COI sequence analysis. Samples were collected from Tanga, Dar es Salaam, Mtwara, Mafia, Pemba, and Unguja. The extraction of genomic DNA was done from muscle tissue using CTAB method and the COI gene was amplified by PCR amplification with the LCO1490 and HCO2198 primer pair. Subsequent analyses of the COI sequences revealed a moderate haplotype diversity and a low nucleotide diversity. Although Tajima’s D and Fu’s Fs, were negative but non-significant (p > 0.05), a unimodal mismatch distribution and star-like haplotype network provided stronger evidence for recent demographic expansion in the population of T. palustris. Moderate genetic differentiation among populations was revealed by FST value, indicating substantial gene flow and the likelihood of a single panmictic population. The absence of significant genetic structure supports treating the T. palustris fishery along the Tanzanian coast as a single unit stock. Maintaining habitat quality remains important because healthy, connected habitats facilitate gene flow among sites, helping sustain genetic variation and enhancing the species’ long-term resilience.

ABSTRACT The pervasive presence of microplastics in marine ecosystems poses a significant threat to apex predators such as sharks, already vulnerable due to anthropogenic pressures. This study presents the first documented evidence of microplastics within mermaid’s purses, the protective structures nurturing embryonic sharks. Microplastic concentrations were quantified in egg cases from two oviparous shark species, Hasselt’s bamboo shark, Chiloscyllium hasseltii and coral catshark, Atelomycterus marmoratus. The results reveal that all examined egg cases contained microplastics, with significantly higher levels observed in A. marmoratus egg cases (21.42 ± 0.86 particles per egg case) compared to C. hasseltii (16.35 ± 1.82 particles per egg case). Additionally, a positive correlation between microplastic abundance and yolk mass suggests potential implications for embryonic development. Physico-chemical characterization identifies predominance of fibre morphology, dark-coloured microplastics, and rayon polymer type. These findings highlight the urgent need for targeted conservation strategies to mitigate the impacts of microplastic pollution on vulnerable shark populations and marine ecosystems. This study supports informed policies and concerted efforts to safeguard ocean health and preserve the integrity of apex predator populations, emphasizing the interconnectedness of marine ecosystems and the imperative of sustainable stewardship.

ABSTRACT Sacoglossan sea slugs are particularly famous for the ability of some species to retain photosynthetic chloroplasts in their cells. While it is still uncertain how and to what degree the slugs might benefit from these alien organelles (kleptoplasts), some studies investigated whether a phototactic behaviour could be related to increasing the kleptoplasts' photosynthetic activity. To address whether this behaviour is connected to increasing photosynthetic activity, we investigated Elysia viridis in a side-choice experiment and analysed the time the slugs spent in either white or red light compared to a shaded area. We also investigated the slugs' general mobility and determined the number of changes between the two areas. We performed our experiments with freshly fed and several weeks-starved animals, and performed the same experiments with animals constantly exposed to a photosynthetic blocker. Our results suggest that the photobehaviour of Elysia viridis is not connected to increasing the photosynthetic activity of the kleptoplasts. Yet, when tested under white light, the photosynthetic blocker induced a shift in behaviour during the first two weeks of starvation, leading to a more balanced distribution between shaded and illuminated areas. This shift could be linked to higher stress levels, potentially resulting from greater kleptoplast damage.

ABSTRACT This study investigated the physiological responses of phytoplankton to reduced light availability, a common feature of turbid coastal ecosystems, focusing on their acclimation and recovery under prolonged light exposure. Three irradiance treatments (low light [LL], medium light [ML] and high light [HL]) were administered for 15 hours, followed by a 3-hour recovery period at 10 μmol photons m−2 s−1. Exposure to prolonged HL significantly reduced the maximal photochemical efficiency of PSII (Fv/Fm) from 0.613 rel. units at initial incubation to 0.302 rel. units after one hour. The HL treatment showed significantly lower non-photochemical quenching (NPQ), indicating an impaired ability to dissipate excess light energy. However, despite this impairment, photoinhibition did not occur. Under HL treatments, a steady increase in photosynthetic capacity (rel.ETRmax) was observed after seven hours of incubation, suggesting that the phytoplankton fully utilized the available light for photosynthesis during the early stages of exposure. LL treatments maintained high photosynthetic efficiency (α) and displayed better overall photosynthetic performance compared to ML and HL treatments. Our findings highlight the significant photophysiological plasticity of turbid water phytoplankton, evidenced by their rapid recovery from light stress, a crucial trait for their survival and productivity in dynamic coastal environments.

ABSTRACT This report deals with the scleractinians collected during the four Spanish-Mauritanian multidisciplinary Maurit surveys, carried out between 2007 and 2010, along the coast of Mauritania, between 80 and 2000 m depth. A total of 13 species belonging to 10 genera and six families were identified. Caryophyllia (Caryophyllia) smithii Stokes & Broderip, 1828 and Thalamophyllia gasti (Döderlein, 1913) are reported herein for the first time from Northwest Africa. At the same time, Fungiacyathus (Bathyactis) marenzelleri (Vaughan 1906), Desmophyllum dianthus (Esper, 1794), Tethocyathus variabilis Cairns, 1979 and Balanophyllia (Balanophyllia) cellulosa Duncan 1873 are new records for Mauritanian waters. Some records reported here represent the southernmost records for some eastern Atlantic species. With six species recorded for the first time in Mauritania, the number of known scleractinians from the area is raised from 14 to 20 with this report. A checklist of the scleractinians occurring in the study area is also included.

ABSTRACT Climate change has increased the frequency, intensity, and duration of extreme thermal events. Our understanding of how marine heatwaves (MHWs) and marine cold spells (MCSs) affect coastal species remains limited, particularly in understudied regions. This study assessed the effects of short and extended extreme thermal events on the southern African whelk Burnupena lagenaria, through exposure to three treatments i.e. MCS, MHW, and a climatological mean (control), in both summer and winter. Mortality was recorded daily, and metabolic rate was assessed at the end of each experiment. Mortality was low and did not differ among treatments (MHW: 0.9%; MCS: 1.9%) or durations (short: 0.9%; extended: 1.9%) in winter experiments. In this cold season, metabolic rate was depressed under MCS conditions, but less so in the extended duration. In contrast, summer MHW conditions elevated mortality (MHW: 35%; MCS: 0%), this intensified with prolonged exposure (short: 7.4%; extended: 25%). Metabolic rate reduced under MHW conditions regardless of duration. This temperate whelk is thus unlikely to be negatively affected by MCSs, even during winter. However, summer MHWs are expected to pose a challenge, especially over extended periods. This is concerning considering the increase in occurrence and duration of MHWs along the southern African coast.

ABSTRACT Epibionts were identified from adult horseshoe crabs from Delaware Bay, New Jersey and Jamaica Bay, New York during the peak of the spawning season from 1997–2003 and 2012–2021. Acorn barnacles, bryozoans, slipper shells (Crepidula fornicata), polychaetes (Sabellaria vulgaris), and mussels (Mytilus edulis) were the most frequently occurring epibionts; barnacles, Crepidula, and Mytilus were more common in the Jamaica Bay population, whereas bryozoans and Sabellaria were more common in Delaware Bay. However, epibiont species composition was insufficiently distinctive between the two populations to be useful as a biological tag. Four previously unreported epibionts were found: the urochordate Molgula manhattensis, sponge Clathria (Microciona) prolifera, alga Gracilaria sp., and an unidentified chiton. Males were more heavily encrusted than females, which may be related to their mating behavior, in which the males cover a portion of the female's opisthosoma while they are attached to her. Jamaica Bay crabs had significantly more of their carapace encrusted than crabs from Delaware Bay, and the carapace condition index, an indicator of post-molt age, was significantly worse for Jamaica Bay animals. The preponderance of older aged adults in Jamaica Bay may be indicative of poor recruitment into this population and/or emigration of younger adults from Jamaica Bay.

ABSTRACT Understanding population genetic diversity and evolutionary dynamics of marine fish species can provide theoretical bases for fishery management and germplasm conservation, especially facing a changing environment. The rockfish species in genus Sebastiscus are economically important species for farming and sport fisheries in China, Japan and Korea. In this study, inter-annual and inter-specific comparisons on genetic diversity, population differentiation and historical demography of S. marmoratus and S. tertius collected from coastal waters of Zhangzhou, China were conducted using mitochondrial control region sequences. High levels of genetic diversity were observed in both species, indicating high adaptive potential to environmental changes. Demographic analyses detected recent population expansion in population S. tertius (Ste-2020) and population S. marmoratus collected in 2020 (Sma-2020), yet failed in population collected in 2016 (Sma-2016). Moreover, in population Sma-2020, novel haplotypes were detected and grouped into a separate sub-branch, revealed by neighbour-joining topology. Detected recent population expansion and novel haplotypes might be considered as a response to environmental changes. Besides, results of genetic differentiation analysis suggested high intra-specific genetic variation in both species. These genetic data and information will provide novel implications for strengthening the management of S. marmoratus and S. tertius fisheries in climate change scenarios.