The epibenthic euryhaline hydromedusa Vallentinia gabriellae Vannucci Mendes, 1948 is an olindiid species native to tropical Atlantic waters. Here, we describe the cryptic introduction of this species in an estuary along the coast of Kerala, in southwestern India. This study records the existence of V. gabriellae outside of Atlantic waters for the first time and documents its geographical range expansion. Our identification was based on a combined morphological and DNA barcoding assessment using the COI and 28S markers. Although we noted some morphological differences between our specimens and those from their native range, our findings were conclusive. We suggest that phenotypic plasticity may result from differences such as prey availability between the native and introduced habitats. V. gabriellae medusae are epibenthic and cling to a variety of hard and soft substrates, including bivalves. Our specimens were associated with the invasive fouling mussel Mytella strigata, and we suggest that V. gabriellae could have been transported along with these mussels to the Kerala coast.

For the bioassessment of tropical marine ecosystem, a survey of protozoa colonizing artificial substrate was conducted in the coastal waters of northern Bay of Bengal, Bangladesh. Protozoan samples were collected using glass slides from 1 and 2 m water depths at time intervals of 3, 7, 10, 14, 21, and 28 days during winter and monsoon seasons. Thus, the colonization processes of protozoa were assigned into three stages namely the initial (3 days), transitional (7 days), and equilibrium stages (10–28 days) at two depths in two seasons. Regression analyses demonstrated that the colonization dynamics of protozoa were well fitted to the MacArthur-Wilson model and logistic equation. Species richness reached equilibrium after 10–14 days and species abundance was maximum at a depth of 1 m. These results suggest that samples of protozoa can be collected at 1 m depth in winter season for monitoring the ecological health of tropical marine ecosystems.

Changes in abundance and distribution of marine top predators can indicate environmental change or anthropogenic pressure requiring management response. Here, we used an extensive dataset (21 years) to conduct a spatial and temporal analysis of grey seal strandings in Cornwall and the Isles of Scilly, close to the southern edge of the breeding range of the species. A total of 2007 strandings were reported from 2000 to 2020, increasing by 474% from 35 to 201 individuals per year during this period. The continued rise in strandings was consistent across all life stages and timeframes (5, 10 and 20 years), underpinning the suggestion of increasing abundance in the region. The observed seasonality differed by life stage, coinciding with the increased presence of animals near the coast for key life phases such as breeding, moulting and pupping. Strandings are widely distributed across the coast of Cornwall and the Isles of Scilly; however, most strandings were recorded on the north coast of Cornwall (70%) where major pupping and haul out sites are found. Despite hosting several pupping and haul out sites, a small proportion was recorded on the Isles of Scilly (5%) where it is thought that strandings are particularly underreported. Describing baselines in magnitude of strandings and life-stage compositions across space and time allows future deviations in frequency, demographic composition or spatial distribution to be detected and investigated. We demonstrate the utility of long-term citizen science data to provide valuable and cost-effective information on the distribution and abundance of a highly mobile marine mammal.

Despite holding the accolade as the largest animal ever to live on planet earth and ubiquitously inhabiting the world's major oceans, an acute paucity of information surrounds the geographical distribution and migration phenology of the endangered blue whale (Balaenoptera musculus) in the northeast Atlantic. Current migration and distribution information derived from robust scientific studies is required to ensure the formulation and implementation of successful conservation measures with a vision to support the ongoing recovery of the northeast Atlantic population. At 10:21 (UTC) on the 9th of November 2020, two blue whales were observed at position 55°13.99′N, 01°13.62′W, 18 km off the coast of the UK in the central North Sea just north of Newcastle at a water depth of 76 m. This is the first paper that has confirmed an account of live blue whales frequenting shallow waters of the central North Sea and represents a new area of occurrence within the accepted range of the northeast Atlantic population, an area in which sightings are extremely rare and may provide insight into the intricacies of migration routes and behaviour.

The alvinocaridid shrimp Shinkaicaris leurokolos Kikuchi and Hashimoto, 2000, is an evolutionarily important deep-sea species in hydrothermal vents of north-western Pacific. A genome survey of S. leurokolos was carried out in order to provide a foundation for its whole-genome sequencing. A total of 599 Gb high-quality sequence data were obtained in the study, representing approximately 118× coverage of the S. leurokolos genome. According to the 17-mer distribution frequency, the estimated genome size was 5.08 Gb, and its heterozygosity ratio and percentage of repeated sequences were 2.85 and 87.03%, respectively, showing a complex genome. The final scaffold assembly accounted for a total size of 9.53 Gb (32,796,062 scaffolds, N50 = 597 bp). Repetitive elements nearly constituted 45% of the nuclear genome, among which the most ubiquitous were long interspersed nuclear elements, DNA transposons and long-terminal repeat elements. A total of 12,121,553 genomic simple sequence repeats were identified, with the most frequent repeat motif being di-nucleotide (70.27%), followed by tri-nucleotide and tetra-nucleotide. From the genome survey sequences, the mitochondrial genome of S. leurokolos was also constructed and 71 single nucleotide polymorphisms were identified by comparison with previous published reference. This is the first report of de novo whole-genome sequencing and assembly of S. leurokolos. These newly developed genomic data contribute to a better understanding of genomic characteristics of shrimps from deep-sea chemosynthetic ecosystems, and provides valuable resources for further molecular marker development.

The sharpnose shark (Rhizoprionodon longurio) is among the top three shark species captured by artisanal fisheries of the Gulf of California. This study includes information regarding the feeding habits of this species using the stomach contents of 70 individuals ranged from 54 to 109 cm in total length (TL). Out of the 16 prey items identified, fish of the families Scombridae (Scomber japonicus; prey-specific relative importance index [%PSIRI] = 6.3) and Batrachoididae (%PSIRI = 5.5), the cephalopod Lolliguncula spp. (%PSIRI = 6.3), and the crustacean Pleuroncodes planipes (%PSIRI = 4.3) were the most important prey. Only female stomachs were obtained (N = 19) in the central area of the gulf, and the PSIRI indicated that the preferred prey were the cephalopod Lolliguncula spp. (%PSIRI = 10.5) and fish of the Sparidae family (Calamus brachysomus; %PSIRI = 5.8). The number of stomachs was not sufficient to analyse differences by sex. Regarding its trophic position, R. longurio was a tertiary consumer (TLK = 4.4). A TLK = 4.4 was calculated for the central area, and a TLK = 4.3 for the southern area. According to Levin's index (Bi), this shark is a specialist predator in the whole study area (Bi = 0.19), including the centre (Bi = 0.29). Conversely, it was considered a generalist predator in the southern area (Bi = 0.63). The high quantity of empty stomachs could relate to the time the sharks were caught in fishing a gear.

The reproduction of bopyrid isopod parasites is thought to occur immediately following host ecdysis, but direct observations supporting this hypothesis are limited. The aim of this study was to describe the reproductive behaviour of the bopyrid isopod Bopyrus crangorum relative to host ecdysis based on video recordings. Several hours after host ecdysis, biphasic moulting of female parasites was observed. The cuticle of the posterior body was shed before that of the anterior body at an interval of 1 h. Two hours after female moulting, the male repeatedly moved from its initial position between the female pleopods and stopped at the anterior end of the fifth oostegite, immediately above the gonopore. To our knowledge, this repeated visiting behaviour by males has not been previously observed in bopyrid isopods. Oviposition through the female gonopore occurred 33 min later. The male-removal experiment showed that females with their males removed after visits to the gonopore oviposited eggs, whereas females with their males removed before visits did not. We propose that repeated visits by males to the gonopore are attempts to inseminate the female. We hypothesised that sperm are released onto the external surface of each gonopore and that the eggs are fertilised as they pass through the opening, which would explain the synchronous development of fertilised eggs inside the marsupium. The present study provides new information on the life history of bopyrid isopods, which allows for a better understanding of the host–parasite relationship.

To cultivate zooplankton species with highly fragile mucoid structures, a new type of cultivation device was developed, which uses a novel method to gently circulate the water in the culture vessel. Using this device, a species of the fritillarid appendicularia (Fritillaria sp.) collected in Sagami Bay was successfully cultivated. This form resembles Fritillaria haplostoma or Fritillaria formica tuberculata, but some taxonomical characteristics differed from those of the latter forms. A novel device comprising a polycarbonate bucket with a motor-driven rotating cylinder inserted into the water in the bucket was developed and maintained Fritillaria sp. over ten filial generations in the laboratory. The animals reached trunk lengths of 1026 ± 85 μm (mean ± SD) four days after fertilization at 23°C. The instantaneous growth rates were calculated as 1.11–1.72 at 20–26°C, representing a 3.0–5.6-fold daily increase in body weight. The house constructed by this species is extraordinarily fragile, typically has a barrel-like or cylindrical shape, and accommodates its entire body and food-concentrating filter. At 23°C, the species produced houses at a rate of 28 ± 2.8 houses d−1. The new device is useful for the continuous cultivation of the fragile form of fritillarid appendicularia, and even for various other zooplankton. It also shows that Fritillaria sp. could be a significant secondary producer and transporter of organic matter in marine ecosystems due to its high growth and house production rates.

The spread of the brown seaweed Sargassum muticum is one of the best documented invasions of a non-native marine species. Observation of a potentially established population of S. muticum in the Orkney Islands archipelago, located off the northern coast of Scotland, was reported by recreational snorkellers in 2019 and 2020. The present study summarises a focussed investigation to confirm its presence and current local distribution, using data from 46 survey sites monitored as a part of the Orkney Islands Council Harbour Authority monitoring programme. Findings in this study represent the most northerly record of an established population of S. muticum in the United Kingdom, extending the latitudinal range in this country by 1.44° (159 km) northwards, and indicate only localised presence of this species. Analysis of a partial cytochrome oxidase I gene sequence confirmed the visual species identification. Possible vectors of introduction, gaps in the geographic range, local ecological and economic impacts, and the potential ameliorating factor of deep rockpools on wave exposed shores for S. muticum are discussed.

Polychaetes from tropical ecosystems of the eastern Pacific have been poorly studied; thus, the aim of this study was to analyse their taxonomic composition in the southern Mexican Pacific shelf and to examine their biogeographic affinities. A total of 3741 specimens from 82 species, 52 genera, and 27 families were identified from 38 stations at 42–109 m depth. The Sedentaria group was more diverse (40 species, 48.8%) and abundant (1753 ind., 46.9%) compared to the Errantia (36 species, 43.9%; 346 ind., 9.2%) and the Basal Annelida groups (6 species, 7.3%; 1642 ind., 43.9%). The families Onuphidae (14 spp.), Spionidae (8 spp.), and Paraonidae (8 spp.) were the most diverse. The Amphinomidae and Spionidae accounted for 72.6% of the fauna; the remarkably high abundance of both families together is unusual in the tropical eastern Pacific. The polychaete species had high biogeographic affinities with the Mexican tropical Pacific ecoregion (45.1%), which has tropical conditions, and the Cortezian (29.3%), which has warm-temperate characteristics. Twelve amphiamerican species and ten with worldwide distribution were found. The tropical eastern Pacific is one of the world regions with the lowest number of polychaete records, thus underlining the importance of the taxonomic and biogeographic information provided here. The sampling effort should increase, since the non-parametric estimators indicated that 116–138 species were expected, instead of the 82 species actually found.

The spatial and seasonal variability of the microphytoplankton and ciliates communities in relation to the environmental factors were studied in the southern coastal area of Sfax. Results revealed a striking difference between seasons regarding pH, with strong acidification in autumn generated by industrial activity. Spatial distribution of pH in autumn impacted the microorganisms in different ways: acidic stations to the south showed significant correlations with Cyanobacteria, dinoflagellates and loricate ciliates whereas higher pH values in spring (pH > 8) were linked to diatoms richness. The high availability of inorganic phosphate is associated with the high release of phosphate due to residue from a phosphate treatment manufacture along the coast; consequently, N/P ratios were low (1.34–13.43) suggesting nitrogen limitation. Microphytoplankton abundance shifted from dinoflagellates dominance in autumn to dominance of diatoms during winter and of Euglenophyceae in summer. Loricate ciliates accounted for the largest proportion of the ciliates community while aloricate ciliates were relatively scarce during all seasons. Variability of ciliate community appeared not directly linked to environmental conditions, but significant positive relationships between abundance of loricate ciliates and microphytoplankton suggest that these ciliates may feed on microphytoplankton.

Examination of the material collected by Taiwan deep-sea cruises reveals the presence of five species of the deep-sea shrimp genus Glyphocrangon A. Milne-Edwards, 1881, representing new records for Taiwan and Dongsha (Pratas Island; under jurisdiction of Taiwan). These species are Glyphocrangon albatrossae, G. caecescens, G. indonesiensis, G. major and G. proxima, all of which belong to the informal Glyphocrangon spinicauda species group. These findings bring the total number of species in the G. spinicauda species group reported in the waters around Taiwan and Dongsha to 11. The complex ornamentation of the body surface of each species is shown using micro-computed tomography. Diagnosis and illustrations showing diagnostic characters and living colouration are provided for most, if not all, of these species. Glyphocrangon grandis is placed under the synonymy of G. major based on morphology, because it was found that diagnostic characters proposed to distinguish these two taxa are variable within the current series of specimens. The biogeographical distributions of these species are presented, and a key is provided to help identify the 11 known species in this region.

The objective of this paper was to characterize bycatch in an experimental fishery for Patagonian toothfish in Ecuador during 2017–2021. Diversity was analysed using Shannon, Margalef, Simpson, and Dominance indices. Bycatch representativity was calculated as the difference percentage between the target catch and non-target, in weight. The bycatch comprised 51 taxa and was composed primarily of fish. In addition, 12 species of pelagic habits (i.e. fishes and sharks) were also captured during the deployment/retrieval of fishing gear. The most frequent species (by number of individuals) were chimaeras (Hydrolagus melanophasma), grenadiers (Antimora rostrata, Coryphaenoides delsolari, and Coryphaenoides armatus), and sharks (Etmopterus granulosus and Centroscymnus owstonii). The diversity was medium low, according to the Shannon indices (0.5–1.8), with a negative trend for dominance and a positive trend for equitability.

Two new species of Microlaimidae: Microlaimus paraaffinis sp. nov. and Pseudomicrolaimus major sp. nov. are described from Yangma Island, the Yellow Sea. M. paraaffinis sp. nov. is characterized by body length 662–785 μm, six inner and six outer labial sensilla papilliform, four short cephalic setae 3–4 μm in length, amphidial fovea cryptocircular at level of buccal cavity, spicules L-shaped with equal thickness, gubernaculum boat shaped, tail conico-cylindrical with short cylindrical portion. P. major sp. nov. is characterized by large body size, six inner labial sensilla papilliform, six outer labial sensilla and four cephalic sensilla setiform, eight subcephalic setae present, amphidial fovea cryptospiral, anterior pharynx region at the buccal cavity widened, posterior pharynx region with oval-shaped bulb, spicules curved with proximal portion enlarged, gubernaculum boat shaped, tail short and conical. Pictorial key to genus Pseudomicrolaimus is given.

The present study investigated the horizontal and vertical distribution of meiofauna community and Nematoda assemblages on two sandy beaches and two muddy tidal flats in a freshwater Amazon estuary governed by mesotides. Meiofauna density was significantly higher in muddy environments, explained by the higher food availability. On the one hand, there was no difference between sediment layers in both sandy environments, which suggests that individuals must have migrated to layers deeper than 10 cm. On the other, the highest densities and richness in muddy environments occurred in the upper layer due to higher food and oxygen availability in the surface sediment layer, which decreases with depth. Muddy environments differed on both beaches; they had the highest nematode genera densities and richness. This might be explained by the high nutrient enrichment in these environments. There was no significant difference in Nematoda density and richness between zones in any environment, likely due to the small mid-littoral extension (<40 m), which did not favour the high spatial variability of genera. Nematoda density was higher at a depth of 0–2 cm in both muddy environments, explained by the availability of oxygen and food. The high abundance of deposit-feeder genera in muddy environments indicates high organic enrichment, whereas the distribution of trophic types was more homogeneous on the beaches where abiotic factors tended to be more structuring than food availability.

The subfamily Polycerinae includes eight genera, from the monospecific Lamellana and Lecithophorus to the diverse Polycera and Gymnodoris, with 33 and 26 valid species, respectively. The monophyly of the subfamily has been tested by molecular data although not all genera were included. To date, relationships within the subfamily are not supported. In the present paper, three new species of polycerid nudibranchs are fully described based on specimens collected in Marshall Islands and Australia: one Palio species (Palio gaeli sp. nov.), one Polycera species (Polycera nimbsi sp. nov.) and a new genus (Paliota galactica gen. and sp. nov.). The new genus is described based on its peculiar radular teeth and genetic divergence.

The internal anatomy was studied by dissections and scanning electron microscope photographs. Partial sequences of mitochondrial cytochrome oxidase c subunit I (COI) and 16S ribosomal RNA (16S) as well as nuclear histone H3 (H3) were also obtained. A phylogenetic framework for two of these three species is proposed, also including for the first time the species Paliolla templadoi and Polycera melanosticta.

The family Syngnathidae contains 52 seahorse species, which inhabit a range of habitats including coral reefs, seagrass beds and coastal estuaries. The seahorse Hippocampus kelloggi is among the most widely distributed species, occurring from Indo-West Pacific to East Africa. This species was included in the IUCN Red List in 2017 and is classified as vulnerable according to A2cd criteria. In this study, three specimens collected from the central coast of Mozambique were investigated and based on morphology and mitochondrial subunit of cytochrome oxidase I (COI) were identified as H. kelloggi. These results confirmed for the first time the extensive range of occurrence of H. kelloggi on the central coast of Mozambique.

A new record of a white humpback whale (Megaptera novaeangliae) was made off Papeete, Tahiti in July 2019. The individual was completely white, except for grey patterns on its body and on the ventral part of the fluke. The presence of different colourations indicates that this individual is not an albino but a leucistic individual. According to field observations, the individual was likely a juvenile or a subadult. It was seen breaching several times and travelled further north of Papeete, where the animal was recaptured off Arue. White individuals are rare and offer unique opportunities to understand whale movement patterns and potential population connectivity among humpback whale populations.

Cephalopod populations have expanded over recent decades, both numerically and geographically. These expansions are particularly noteworthy because cephalopods are a taxon of quickly reproducing, high-metabolic rate predators that can have disproportionate impacts on naïve ecosystems. We report a new occurrence of an octopus species in 11.6 m of water in Burrows Bay, Washington, USA (coastal northeast Pacific Ocean). These newly identified individuals have several characteristics that clearly differentiate them from either of the two known octopus species that occur in shallow water within the area: Octopus rubescens and Enteroctopus dofleini. Instead, specimens superficially resemble Muusoctopus leioderma, a species which is found in the geographic area, but has never been reported at depths less than 70 m. Octopuses were collected for morphological and genetic comparison to known octopus species, focusing on other nominal Muusoctopus species. Genetic comparisons were conducted using three mitochondrial loci (12S ribosomal RNA, cytochrome oxidase subunit III, and cytochrome b) sequenced for the octopus along with two M. leioderma museum specimens, including the species' neotype. Observation of octopus behaviour revealed a unique burrowing behaviour. Morphology of the octopus found in Burrows Bay largely coincides with M. leioderma, with a few notable differences. Phylogenetic analysis revealed that Burrows Bay octopus forms a monophyletic clade with the M. leioderma neotype, but also suggested that M. leioderma is more closely related to Octopus californicus than to the other members of the genus Muusoctopus. These octopuses are thus attributed to M. leioderma but the generic placement of the species should be reviewed.

Photographs of a single shark specimen (1040 mm in total length) caught in the Oyodo River estuary, Miyazaki Prefecture, Kyushu, Japan, by a recreational angler and uploaded to the social networking service Facebook, were identified as a juvenile specimen of the bull shark Carcharhinus leucas. The photographic record, now deposited in the Kanagawa Prefectural Museum of Natural History collection, represents the northernmost record of this species in the western Pacific Ocean. Although C. leucas is known to utilize primarily tropical estuarine habitats as nursery grounds, a few reports exist regarding the utilization of subtropical and warm-temperate latitude estuaries, as in this case. From the perspectives of species conservation and shark-bite mitigation in warm-temperate latitudes, further information on C. leucas occurrence around its northern distribution limit is required.