Antimicrobial-resistant bacteria pose serious public health risks, necessitating bioprospecting for novel antimicrobial drugs. The endophytic fungi of the mangrove ecosystem are hotspots for discovering new bioactive chemical compounds. In this context, an investigation was designed to determine the isolation of the major endophytic fungi inhabiting the leaves of Acanthus ilicifolius, a mangrove plant with a long history of traditional use in the Chinese and Indian medical systems. Based on the morphological characterizations and molecular analysis of internal transcribed spacer rDNA sequence data, the study identified three unique endophytic fungal species, namely, Periconia macrospinosa, Coprinopsis cinerea, and Alternaria sp. Of these, P. macrospinosa was identified as the most dominant one, with the highest relative frequency (35.22%). The antibacterial activity of P. macrospinosa isolate (CMFRI/fPM-01) was evaluated by the well and diffusion method against six human pathogens, viz., Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus. The results demonstrated a high and wide spectrum of antimicrobial action of the isolate against all the tested human pathogens, with no significant difference (P > 0.05) in the activity between the pathogens. The antibacterial activity was further confirmed by determining the fungal culture supernatant's minimum inhibitory concentration and minimum bactericidal concentration. Although the studied fungi are known from other sources, this is the first report of P. macrospinosa and C. cinerea as endophytes in A. ilicifolius leaves. The outcomes also showed that the P. macrospinosa isolate could be used to discover effective antibacterial drugs against various human diseases.

One specimen of tropical shad was caught from the Giang Thanh River, Kien Giang province, Vietnam in a survey on 16 October 2022. We identified the specimen as the hilsa shad, Tenualosa ilisha Hamilton, 1822 using morphological analysis, and further validated by its cytochrome oxidase subunit I (COI) sequence. The specimen was 418 mm long, 1428 g in weight, with a head length of 29.0% and pectoral fin length of 31.1% of its standard length. Notably, the presence of 34 scutes, a higher gill raker count and a caudal fin length within the moderate range for Tenualosa species distinguished it from T. macrura, T. toli and T. reevesii. The COI sequence of the sample matched closely to the T. ilisha. The results confirm that T. ilisha still endures Vietnamese water, where it was thought to be extinct. Climate change and Indo-Pacific Ocean currents may introduce expansion of distribution area of the T. ilisha. Further studies on distribution of the T. ilisha and other Tenualosa species and their dynamics are needed.

Post 2004 tsunami and earthquake, the landmass of Andaman and Nicobar Islands (ANI's) experienced uplift (North Andaman and Mayabunder) and subsidence (South Andaman & Nicobar Islands). The altered geomorphology modified the tidal regime, which resulted in mangrove degradation in their current locations and the formation of new intertidal zones potential for mangrove colonization. Avicennia species; a pioneer in mangrove succession was expected to colonize such new intertidal zones. Therefore, to understand the colonization pattern of Avicennia species in these new intertidal zones and their distribution in the old forests, we surveyed 79 sites across ANI's (55 Andaman and 24 Nicobar Islands). Our survey confirms the presence of three Avicennia species namely A. marina, A. officinalis, and A. alba – a new distribution record to the ANI's. Further, A. marina was found to be the most widely distributed, and abundant among three Avicennia species (Relative Abundance (RA) – 97.92%; Relative Frequency (RF) – 68.75%). In contrast, A. officinalis (RA – 1.93%; RF – 26.25%) and A. alba (RA – 0.16%; RF – 5%) were found limited in their distribution and abundance. As per the IUCN Red List, the Avicennia population is decreasing globally, whereas, its population may increase significantly across ANI's due to the availability of vast new intertidal zones. Hence, Avicennia spp. can be utilized in the plantation programs to facilitate rapid colonization in the unvegetated potential mangrove habitats across ANI's. Such an effort will improve the mangrove ecosystem services that were hampered due to mangrove degradation by the 2004 tsunami.

Climate change poses a major threat to marine ecosystems, with its effects felt worldwide. A major effect of climate change on marine ecosystems is the rise in water temperature, leading to a northward expansion of habitats for marine organisms. Herdmania momus, a species of ascidians (sea squirts), originally found in tropical and subtropical regions, was introduced to the Korean Peninsula. In this study, we examined the habitat of H. momus along the southeastern coast of the Korean Peninsula between 2016 and 2022. We found that H. momus settlements were observed across the entire survey area, with confirmed habitation in Busan in 2016, Ulsan in 2021, and Gyeongju (the northernmost location) in 2022. The observed habitation trend indicates a rapid geographical expansion, occurring approximately 79 years earlier than previously predicted. These observations demonstrate that marine organisms are undergoing a more rapid geographical expansion than previously projected. These unexpected findings should inform government policies related to proactive measures and strategies for managing the impact of climate change on marine ecosystems.

The evaluation of the effects of early starvation and feeding on survival and growth in the early stages of the life cycle of ornamental marine caridean shrimp species is fundamental to establish adequate feeding protocols in their culture. In this study, we determine the nutritional vulnerability in the early larval stages of ornamental shrimp Lysmata ankeri exposed to different periods of starvation or feeding. The larvae were separated into three groups (zoea I-ZI, zoea II with ZI fed, and zoea II with ZI unfed) and subjected to two experiments: (1) point-of-no-return (PNR), comprising one or two days of initial starvation followed by feeding; and (2) point-of-reserve-saturation (PRS), comprising one or two days of initial feeding followed by starvation. Each experiment was still composed of two control groups: continuous feeding and continuous starvation. Larvae tolerated some periods of starvation, with a high PNR value (2.00) and low PRS (0.50). Longer periods of starvation influenced both growth and survival rates in zoea II stages. The nutritional vulnerability index for zoea I was 0.25, which represents a low dependence on food supply. In this study, it was observed that ornamental shrimp L. ankeri larvae hatch with energy reserves, presenting facultative primary lecithotrophy, in which they are able to moult from zoea I to zoea II using such reserves in the absence of food. In this sense, the early larvae stages (zoeas I and II) can tolerate a certain period of starvation, indicating the great potential of this species for aquaculture.

Bivalve molluscs are a diverse group of animals with particular economic and ecological importance. Their morphological characteristics frequently confuse their identification leading to mislabelling of edible species. Genetic diversity is critical to the resilience of marine bivalve populations in the face of environmental stressors such as ocean acidification and warming. In this study, we characterized the phylogeny and defined the first DNA barcodes of six marine bivalves [Ostrea edulis (Linnaeus, 1758) Arca noae (Linnaeus, 1758), Pinctada radiata (Leach, 1814), Venus verrucosa (Linnaeus, 1758), Calllista chione (Linnaeus, 1758) and Ruditapes decussatus (Linnaeus, 1758)] sampled from different coastal areas of Aegean and Ionian Seas using the molecular markers cytochrome c oxidase subunit I (COI) and 18S ribosomal RNA (18S rRNA). Further, COI gene was employed to investigate the population genetic diversity since 18S rRNA exhibited no conspecific differences. The sequence of 18S rRNA successfully discriminated the bivalves at family or superfamily level but occasionally proved insufficient for species identification. Contrariwise, COI was highly informative and could reliably distinguish all species. Population haplotype diversity was moderate to high and was always accompanied by generally low nucleotide diversity, indicating genetically closely related haplotypes. The invasive Pinctada radiata was found to be panmictic even among distant sampling areas, while Ostrea edulis was the only species that exhibited moderate levels of population subdivision. Finally, here we report for the first time the presence of Ostrea stentina in Thermaikos Gulf sampled among Ostrea edulis specimens, demonstrating a new invasive bivalve species in Eastern Mediterranean.

Large-scale outbreaks of the dinoflagellate Karenia mikimotoi caused substantial mortality of abalone, Haliotis discus hannai in Fujian, China in 2012, resulting in 20 billion in economic losses to abalone industries. However, the mechanism behind the mortality, especially the reaction of abalone to this microalgal toxicity, which possibly differed significantly from the former ‘fish killer’ strain in the South China Sea (SCS). Our study revealed that K. mikimotoi FJ-strain exhibited a four-fold higher haemolytic toxicity than the SCS-strain during the late exponential phase. At the microalgal cell density of 3 × 107 cell L−1, the FJ-strain caused abalone mortality of 67% in 48 h, with decreased granulocyte–hyalinocyts ratio and phagocytic activity by 58.96% and 75.64%, respectively, increased haemocyte viability by 4.8-fold and severe gill damage. The toxic effect only worked for the haemolytic toxicity from active algal cells, which were probably produced under the contact of algal cells and abalone gills. However, under exposure to the SCS-strain, more than 80% of individuals survived under aeration. The results indicated that FJ-strain was a new K. mikimotoi ecotype with stronger toxicity. It evoked severe effects, with complete abalone mortality within 24 h under the cascading effect of non-aeration (dissolved oxygen declined to 2.0 mg L−1), when exposed to K. mikimotoi FJ-strain at the above density. Thus, apart from the microalgal toxicity, DO depletion exacerbated the mortality of abalone in the experiment. The massive abalone mortalities in Fujian were probably caused by the combination of microalgal toxic effects and oxygen depletion, leading to immunological depression and histopathological disruption.

The sea urchin Arbacia spatuligera is an echinoid distributed in the Southeastern Pacific Ocean from Peru to Chile. This species was previously reported from the subtidal zone with a bathymetric distribution up to 30 m depth. In this work, 128 individuals were found in four mesophotic reefs along the central coast off Chile using closed-circuit rebreathers in technical diving at higher depths than previously, ranging from 36 to 63 m in depth. A population exhibits unexpected morphological characters, requiring an emended diagnosis and description of a new morphotype for A. spatuligera. These morphological traits are further discussed as potential ecophenotypic adaptations.

Taxonomic intricacies and high interspecific similarity have hampered the identification of scyllarid phyllosoma larvae to the species level. The pygmy locust lobster, Scyllarus pygmaeus, is distributed across the Mediterranean Sea and in the eastern Atlantic; however, its phyllosoma larvae were previously recorded only from the western Mediterranean. We employed DNA barcoding using the mitochondrial COI gene to identify S. pygmaeus phyllosoma collected from the offshore waters of the southeastern Mediterranean Sea and described its morphology. We further discuss the lack of genetic structure in S. pygmaeus with potential implications for species connectivity and conservation.

Otoliths are an excellent tool for analysing the pattern of habitat use between adults and juveniles and connectivity between fish populations. Larimus breviceps is a species belonging to the family Sciaenidae, which has an important role in the marine food chain, as it is one of the most abundant and frequent species in the bycatch of coastal shrimp fisheries in Brazil. The present study aimed at comparing the otolith shape of specimens collected in three different Brazilian coastal areas: Sergipe (SE), northeastern region; São Paulo (SP), southeastern region; and Paraná (PR), southern region. In a laboratory, 88 otoliths were extracted, photographed, and the contour was analysed by the wavelet method (32 from SE, 28 from SP, and 28 from PR). The otolith contours varied between sampling sites. Linear discriminant analysis correctly reclassified 60.23% otoliths by the sampled sites, with the best reclassifications occurring in SE (62.5%), followed by PR (60.71%) and SP (57.14%). Multivariate analysis of variance also evidenced significant differences in contours among the sampling sites (F = 2.3; P < 0.005). Thus, two morphotypes of otoliths were found for L. breviceps: one from Sergipe (northeastern Brazil) and the second one from southeastern–southern Brazil, indicating connectivity between the populations off São Paulo and Paraná, to be confirmed by future genetic studies.

A new species of congrid eel genus, Ariosoma is described here based on two mature female specimens collected from trawl by-catch landings at Thoothukudi fishing harbour, off Thoothukudi, Bay of Bengal. The new species can be easily distinguished from its congeners in having pre-anal length 48.7–49.1% TL; dorsal-fin origin just before pectoral-fin insertion; body bicoloured, pale brown dorsally and silvery white ventrally; preopercular portion dark; pectoral fin reddish with dark spot at the base; SO canal with six pores; pre-dorsal vertebrae 10–11; pre-anal vertebrae 61–64; total vertebrae 162–163. Further, the new species differs from all the congeners of Indian waters in having more total vertebrae, except A. albimaculatum (162–163 vs 129–153 in others; 161–164 in A. albimaculatum). The new species identity was also supported by molecular analyses using the mitochondrial COI gene and the result revealed that the new species is closely related to Ariosoma maurostigma and Ariosoma albimaculatum with a pair-wise genetic distance of 11.4% and 11.6% followed by A. melanospilos with 16.8%.

Statolith growth increments were analysed in the bigfin reef squid, Sepioteuthis lessoniana lineage B, for estimating the age and growth in the Gulf of Mannar Biosphere Reserve (GOM), southeast coast of India. The identification of S. lessoniana lineage B was determined by mitochondrial cytochrome c oxidase I gene sequence. The statolith increment age analysis indicated that the wild-captured squid population of S. lessoniana in the study area undergoes rapid growth. The age of S. lessoniana in males ranged from 61 (95 mm dorsal mantle length (DML)) to 220 d (390 mm DML), while it was 64 (98 mm DML) to 199 d (340 mm DML) in females. The average daily growth rate in males and females was 1.63 and 1.55 mm DML d−1, respectively. The instantaneous growth rate varied from 0.85 (210 d) to 4.1% (110 d) for males and 0.65 (190 d) to 3.7% (110 d) for females. The age at first maturity was 114 and 120 d for males and females, respectively. Back-calculated hatching dates and the attainment of maturity in females suggested that the reproduction of S. lessoniana is year-round, with two distinct spawning peaks during July–August and February months; accordingly, the hatching dates were spread throughout the year, with the presence of two cohorts. Based on the statolith data, it can be concluded that S. lessoniana lineage B in the GOM has a potential lifespan of up to 7 months. This finding contradicts the previous growth estimates based on length-frequency data, which underestimated the true growth potential of this species.

A total of five specimens of sand crab, Jonas kalpakkamensis Barathkumar, Das & Satpathy, 2016 were recorded for the first time from the Western Indian Ocean. The sand crab specimens were collected from the bycatch of the commercial demersal trawler targeting crustaceans at a depth of 15–50 m operated along the western region of the Gujarat coastal waters. The collected specimen consists of 3 males and 2 females and it was identified by comparing with holotype and paratype specimens. Previously, J. kalpakkamensis was reported from the Eastern Indian Ocean in the Bay of Bengal region but there is no report or distribution of this sand crab in the Western Indian Ocean. The detailed taxonomic diagnostic character of the sand crab, J. kalpakkamensis and the key for all species under the genus Jonas reported globally is provided in the current study.

Sponges are important components of marine systems globally, and while sponges have generally been shown to tolerate ocean acidification (OA), most earlier studies have focused on demosponges with siliceous skeletons. In contrast, little is known of how calcareous sponges, with calcite or aragonite skeletons, may react to OA conditions. Here we measured tissue necrosis and respiration rate of the temperate New Zealand calcareous sponge Grantia sp. to simulated OA. Our treatment conditions were based on the IPCC RCP8.5 (pCO2 1131.9 ± 113 μatm) scenario over a 28 day experiment, and responses were compared to current day control conditions (pCO2 512.59 ± 23 μatm). Sponge respiration rate was not significantly different between the control and treatment sponges and there was no evidence of tissue necrosis over the course of the experiment. Overall, our study is consistent with earlier studies on demosponges, showing calcareous sponges to be resilient to OA.

In Peter the Great Bay (Russian waters of the Sea of Japan), rhizocephalan barnacle Peltogaster lineata Shiino, 1943, a common parasite of the hermit crab Pagurus brachiomastus (Thallwitz, 1891), was founded for the first time on the hermit crab Pagurus middendorffii Brandt, 1851 (Anomura: Paguridae). Taxonomical identification of the parasite was made using morphological and molecular methods. Pagurus middendorffii is the sixth host of P. lineata.

Polynesia is a hotspot for marine biodiversity in the South Pacific Ocean, yet the distribution of many invertebrate taxa in this region is still often poorly assessed. Information on the diversity and phylogeography of sponges in particular remains limited in spite of their importance for coral reef ecosystems. Recent expeditions to the island group of Wallis and Futuna enabled the first larger-scale assessment of the Wallis Island sponge fauna, resulting in the molecular identification of 82 unique Molecular Operational Taxonomic Units (MOTUs) from 339 sponge samples based on 28S C-region rDNA and CO1 mtDNA data. Faunal comparisons with both adjacent archipelagos and more distant Indo-Pacific regions were predominantly based on the MOTUs obtained from Wallis Island ecoregions, and suggest high levels of endemism of sponges in Wallis and Futuna, corroborating previous data on the biodiversity of sponges and other marine phyla in the South Pacific. The results of this molecular taxonomic survey of the Wallis and Futuna sponge fauna aim to lay solid foundations for a sustainable ‘Blue Economy’ in Wallis and Futuna for the conservation of their local coral reefs.

The brachiopod Argyrotheca cuneata (Brachiopoda: Megathyrididae) is reported for the first time from the southern coast of Türkiye. Twenty-three complete specimens were found in samples of shell grit taken from depths less than 5 m. The findings suggest that A. cuneata may be a common brachiopod species in shallow nearshore habitats along the southern coasts of the country. Widths of the largest and the smallest specimens were 3.7 mm and 0.71 mm, respectively. A comparison of shell dimensions of all specimens indicate an allometric change in the shape of A. cuneata during growth from being longer than wide to wider than long. The protegula preserved on the smallest specimens are described and illustrated possibly for the first time for this species.

We investigated how environmental conditions translate into reproductive success or failure in Aurelia aurita from the medusa to the polyp life stage. This study examined how: (i) settlement success and development of planula larvae and polyps vary across the year, (ii) the role of temperature in determining the successful settlement of larvae and growth of polyps, and (iii) the influence of maternal provisioning in the successful settlement of larvae and growth of polyps. Medusae were collected monthly from February to December 2019 from Horsea Lake, UK. Planula larvae were settled in conditions mimicking the in situ temperature and salinity of collection. For the individual treatments, planula collected in August settled most rapidly. Early development rates (<8 tentacles) were significantly higher than later growth rates (>8 tentacles) and were positively correlated with temperature, unlike later growth rates. Planula length, used as an indicator of maternal provisioning, varied significantly across the year. In July 2019, a high temperature anomaly coincided with an increased time spent by planula larvae in the water column. Increasing temperatures past thermal limits through the increasing occurrence of temperature anomalies is likely to be detrimental to larval settlement and indirectly to the replenishment of temperate polyp populations.

Egg masses from an unknown mollusc have been found in South-West Iceland since 2020, but it was not until September 2023 that the adult organism was collected. Morphological analysis of both adults and egg masses pointed towards the identification of the species as Melanochlamys diomedea. This was further confirmed through DNA analyses using COI, H3, and 16S rRNA markers, which established the presence of a new non-indigenous species in the North Atlantic. Members of the genus Melanochlamys have predominantly been found in the Indo-Pacific basin and the Pacific Ocean, with only one species known to exist across the Madeira Islands, Canary Islands, and Cape Verde in the Atlantic. The known distribution range of M. diomedea extends from Alaska to California on the Pacific side of North America, where it typically inhabits sandy-muddy areas of the littoral in the tidal zone and below. It is not known how the species arrived in Iceland. However, maritime transport through either ballast water or biofouling is being considered as the most likely mode of dispersal.

The introduction of non-native species is a constant concern around the world since it represents one of the main threats to biodiversity, impacting negatively on native populations, some of them with commercial importance. Hence, monitoring these introductions is fundamental to the management and conservation of the biodiversity of a region. Herein, we report the presence of Moerisia cf. inkermanica in the ballast water of oil tankers loaded at the Cayo Arcas oil terminal. The taxonomy of Moerisia members is uncertain due to the lack of comprehensive morphological descriptions and the few molecular data available. So, we provide a detailed morphological comparison among its congeners. The taxonomic identity of the specimens was determined based on the length of the perradial lobes of the manubrium, the number of tentacles, and the features of their nematocyst rings. Some Moerisids are considered invasive in different localities of the world. However, this genus had not been reported in coastal ecosystems of the Gulf of Mexico over the years until now. Sampled tankers came from different ports of the region, mainly from the northern Gulf of Mexico. Therefore, we encourage systematic monitoring of these ecosystems to recognize the establishment of this species as invasive in the region, know its population dynamics over time, and evaluate the possible ecological impacts that could exert on native populations.