A new record of the diogenid hermit crab Dardanus callichela Cook 1989 is described from the Visayan Sea, Central Philippines. Four specimens of D. callichela were caught in fish traps deployed at depths of about 30–40 m adjacent to islands to the north (Nagarao Island, Masbate) and south (Baliguian Island, Iloilo) of the Visayan Sea. The morphological description and colour photographs are provided. Partial sequences of the cytochrome oxidase subunit I (COI) are provided for two specimens and deposited in GenBank. This new record brings the total number of known Dardanus in the Philippines to 16 species.

The first record of the parasite Alebion carchariae in the waters of Ascension Island collected from Galapagos sharks, Carcharhinus galapagensis (Carcharhinidae), is described. No previous record of this parasite exists for Ascension Island, nor have Galapagos sharks previously been listed as a host. Specimens of A. carchariae were identified using morphological techniques and DNA barcoding of the cytochrome c oxidase I subunit (COI) gene. This study provides the first COI barcodes for this species and a brief review of known hosts. We recommend further research to understand the life cycle of this parasite, its plasticity in terms of host/habitat selection, and to determine the implications of its presence on the hosts it inhabits.

The species composition and distribution of marine invertebrates varies greatly in different bathymetric regions. Nevertheless, the process of exchange between faunas of different depths has occurred repeatedly throughout the evolution of marine biodiversity. In high latitudes, this process should occur most actively due to absence of strong temperature stratification. The presence of physiological adaptations that allow northern shallow-water organisms to live at greater depth has been demonstrated in a series of experiments. However, known cases of recent colonization by species confined to a highly productive shallow-water zone in unusually deeper Arctic habitats are almost absent. The present study describes finding of population of the gastropod Onoba aculeus (Gould, 1841) in two samples from the lower continental shelf of the Arctic Ocean. Onoba aculeus is a shallow-water amphiatlantic species widely distributed in the temperate regions. The finding reported here is at the same time, the northernmost, easternmost, and most remote from the coast location. We assume that the detection of molluscs indicates the presence of an abundant isolated population in the region.

The Chilean torpedo Tetronarce tremens is recorded for the first time in the Mexican Pacific. A single male specimen was captured by artisanal fishermen using a bottom-set gillnet off San Agustinillo, Oaxaca. The specimen identification was based on morphology and confirmed by DNA barcoding of the cytochrome oxidase subunit I gene and its comparison with sequences available in online repositories. A phylogenetic analysis of Tetronarce resulted in the clustering of three species that inhabit the Pacific Ocean: Tetronarce tremens, Tetronarce californica and Tetronarce tokionis. This study provides the northernmost record of Tetronarce tremens in the Eastern Pacific Ocean, an atypical sighting beyond its native distribution range in tropical and temperate waters off South America.

We report the first record of Ramari's beaked whale (Mesoplodon eueu) from the temperate Southwestern Atlantic. Our analysis is based on an adult female and a plausibly associated calf/juvenile that stranded on the coast of Canelones Department, Uruguay. The species of the two individuals was identified via a combination of morphometric and molecular mitochondrial data and provide new insights into the Ramari's beaked whale, including previously unknown polymorphisms in the mitochondrial genome and a re-estimated date of divergence from Mesoplodon mirus at 2.5902 Mya.

The Red Sea is a largely homogeneous water column beyond the top 300 m, unique in exhibiting warm bottom water (~21.5 °C) at depths down to ~2900 m. The unusual conditions coupled with barriers to colonization by primary deep-sea species has resulted in an impoverished but distinct deep fauna. This study presents a rare investigation of the deep Red Sea. The bigeye hound shark Iago omanensis is a known deep-sea shark in the Red Sea. However, its full depth distribution has never been conclusively studied. Here, we confirm with videographic evidence the presence of I. omanensis at depths to 2522 m in the Red Sea, along with observations of other deep-sea species. Iago omanensis was the only species of scavenging fish observed and only in moderate numbers. The additional six species were mostly crustacea in low abundance. The lack of scavenging species present in the deep Red Sea is likely explained by the low productivity of the overlying surface waters and unusually warm water temperature resulting in low energetic input but high metabolic demands in deep communities.

Several individuals of the sea anemone Telmatactis cricoides (Duchassaing, 1850) (order Actiniaria) were observed in the Mediterranean continental Spanish coast (Almeria) and the Balearic Islands (Mallorca) showing an expansion of the species, possibly related to rising sea water temperatures. This finding contributes to increase the knowledge on the geographical distribution range of this actiniarian in the Mediterranean basin.

Marine megafauna occurrence was recorded in the deep-sea region bordering the abyssal plain ~400 km north-west of Luanda, Angola. The survey took place during an Environmental Baseline Study (EBS), prior to drilling exploration activities, with the goal of characterizing the habitat and biodiversity of the region. Offshore shipboard surveys were conducted during September 2018 in water depths ranging from 2350–3850 m. We recorded daytime sightings of marine mammals and sea turtles and at night made audio recordings using passive acoustic monitoring (PAM) methods focused on capturing the sounds of vocalizing marine mammals. A variety of species were visually detected, including the humpback whale (Megaptera novaeangliae), sperm whale (Physeter macrocephalus), common dolphin (Delphinus spp.), striped dolphin (Stenella coeruleoalba), Atlantic spotted dolphin (S. frontalis), and olive ridley turtle (Lepidochelys olivacea). Acoustic click bouts similar to those made by several odontocete species, possibly including beaked whales, were recorded within the 25–48 kHz range. The humpback whale was the most frequently sighted species, accounting for 56% of mammal sightings, indicating a potential far offshore migratory habitat in this region. Most notably, right whales (probable Eubalaena australis) were visually observed. This is the first confirmed record of right whales in Angolan waters since the early 1900s. As development expands in this offshore region, these data can usefully inform future monitoring and mitigation strategies focused on minimizing impacts to wildlife.

Identifying species and updating marine biodiversity is fundamental to understanding the evolution of ecosystems and adopting appropriate management strategies. These ecosystems are threatened by climate change causing species mobility, mortality, etc. An important zoological group in the marine ecosystem, octocoral gorgonians have a wide geographic and bathymetric distribution. However, the knowledge of their presence on the Atlantic West African coasts remains limited. Herein, we note the accurate geographic distribution of two species, Leptogorgia dakarensis (Stiasny, 1936) and Eunicella racemosa (Milne Edwards & Haime, 1857), reporting their northern distributional limits. The gaps in the previous knowledge hypothesis of the oceanic warming effects explaining the northward mobility of these species are discussed here.

Abnormal embryonic development may result from mutations caused by genetics, environmental conditions or viruses. This study reports cases of cyclopia and a mouth malformation in two embryonic blue shark Prionace glauca collected off southern Brazil (South-western Atlantic). Such malformations are likely to reduce the chances of survival of embryos and neonates.

We describe Pericelis nivea sp. nov. from sunken wood collected 330 m deep, off the coast of Owase, Japan. This is the first record of Pericelis from the bathyal zone. Unlike other congeners, P. nivea sp. nov. is characterized by the absence of eyespots. We provide a partial sequence of the mitochondrial cytochrome c oxidase subunit I gene as a DNA barcode for the new species. Phylogenetic analyses based on concatenated sequences of nuclear 18S and 28S ribosomal DNA showed that P. nivea sp. nov. was nested in the clade of Pericelis with high support; however, the relationship between P. nivea sp. nov. and other Pericelis species was unclear.

The implementation of consistent and continuous biodiversity survey efforts over a long period of time is imperative to the examination of temporal diversity patterns and the evaluation of existing conservation measures' effectiveness. In Hong Kong, a marine biodiversity hotspot in the South China Sea, reef fish diversity has been poorly documented due to inconsistent and sparse biodiversity surveys, posing considerable challenges to long-term monitoring of biodiversity dynamics. To fill in the data gap, regular scuba underwater visual surveys were conducted across 55 dive sites in Hong Kong during the wet seasons from 2018–2021. After ~3171 hours of underwater survey, 31 reef fish species from 14 families that are new to Hong Kong have been recorded, including species from Acanthuridae, Chaetodontidae, Diodontidae, Gobiidae, Labridae, Mullidae, Nemipteridae, Pinguipedidae, Pomacanthidae, Pomacentridae, Ptereleotridae, Solenostomidae, Tetraodontidae and Tetrarogidae. As Hong Kong sits within the natural distribution range of the newly recorded species, the possibility of artificial release was eliminated after careful consideration. These species were all found outside the currently established Marine Protected Areas (MPAs) in Hong Kong, indicating the need for comprehensive research to identify potential marine reef fish hotspots in areas that are unprotected thus far. Our findings demonstrate the need to establish a long-term monitoring programme that can fill in data gaps of local marine biodiversity to enable the establishment of effective MPAs, and to lay down a baseline for future research and monitoring, so as to safeguard Hong Kong's marine biodiversity in the long term.

This study focused on a jellyfish monitoring and sampling programme along the eastern Qatar seawaters and reports the first jellyfish records for the Qatar pelagic ecosystem and the occurrence of three scyphozoans: the semaeostome Chrysaora cf. caliparea and the rhizostomes Marivagia stellata and Catostylus perezi, considered as first records of Scyphomedusae for Qatar. Jellyfish monitoring, underwater photography and sample collection were carried out along an inshore-offshore transect composed of five stations along the eastern coast of Qatar. Jellyfish material examined, systematic description, general distribution and sting risk of the three species are provided. The discussion section highlights the blooming capabilities of Chrysaora cf. caliparea and Catostylus perezi, while Marivagia stellata seems scarcer, being spotted for the first time since we started our jellyfish investigation programme in August 2018.

Sea anemones have developed various strategies for interspecific interaction with other organisms and their own ability to obtain food, due to their coevolutionary history, ranging from mutualistic (e.g. clownfish, crustaceans, etc.) and symbiotic associations (zooxanthellae or zoochlorellae) to depredation (e.g. sea slug). This study aims to record some observations on feeding habits and interspecific interactions of Actinostella flosculifera (Le Sueur, 1817) in the locality of Pedra da Sereia in Vila Velha, Espírito Santo, Brazil, and to describe the hunting strategy of the sea slug Spurilla braziliana MacFarland, 1909 and the escape strategy of A. flosculifera. We found that the habitat of A. flosculifera is characterized by shallow pools ~10 cm deep at low tides, and this functions as a trap for many organisms and some biowaste (e.g. bones or fish drifting in from nearby populations) that fall into the oral disc. This is the first report of S. braziliana predating on A. flosculifera. We also report interspecific relationships between A. flosculifera with four species of crustaceans: Omalacantha bicornuta (Latreille, 1825), Menippe cf. nodifrons Stimpson, 1859, Alpheus cf. angulosus McClure, 2002, and Alpheus cf. carlae Anker, 2012.

In the present paper, we report the collection of a specimen of the West central Atlantic Stegastes variabilis in the shores of Israel, eastern shore of the Mediterranean. This record was preceded by a record of this species from Malta, in the central Mediterranean. The present record suggests that S. variabilis has established a small population in the Mediterranean.

A eulimid gastropod of the genus Ophieulima, parasitic on the disc of the ophiactid brittle star Ophiactis dyscrita, was collected from 256–343 m deep off Kanagawa, central Japan. This represents the first record of the genus from Japanese waters and even from the North Pacific Ocean. Here we describe it as Ophieulima yoshiharai n. sp. The generic assignment is justified by its conchological characters including (1) a small, conical shape with convex teleoconch whorls, (2) many fine growth lines and some strong growth pause scars on the teleoconch, (3) a well-developed, twisted columella, and (4) a multispiral, brownish transparent protoconch. Ophieulima yoshiharai n. sp. is distinguishable from the three (two named and one undescribed) extant, as well as two fossil congeners by its slender shell with the length of 2.1 times larger than width, a small aperture and a protoconch of 3.5 whorls. The new species is also characterized by its bathymetric distribution, which is shallower than the extant species of Ophieulima. On the other hand, the hosts of Ophieulima species are so far restricted to ophiuroids of the genus Ophiactis and the three named species have mostly been found attached to the lateral and/or dorsal sides of the host's disc, suggesting their similar parasitic ecology.

We present the distribution of the parthenopid crab species Distolambrus maltzami from the North-east Atlantic with a first record from UK seas. The distribution of D. maltzami in the Celtic-Biscay area in the eastern Atlantic, is both described based on recent records from survey data and estimated from modelling its environmental niche. The predicted probability of occurrence is greatest in areas with fluctuating tidal currents and water masses that are rich in chlorophyll-a, cold (minimum bottom temperature lower than 10°C) and oxygen-rich. We include a simple key to distinguish the two parthenopid crab species previously encountered in the region and highlight the importance of a multidisciplinary approach to fisheries data collection.

Two species of deep-sea skates, Amblyraja frerichsi and Notoraja martinezi, are reported for the first time in Peruvian waters, representing the first record of their respective genera from the country. Earlier, A. frerichsi was known from both the southwestern Atlantic (off Brazil, Uruguay, and Argentina) and southeastern Pacific (off Chile), while N. martinezi was known from Costa Rica to Ecuador in the eastern-central and southeastern Pacific. This study contributes to the limited knowledge of deep-sea fish diversity along the South American west coast, and stresses the need of further taxonomic research in the region, particularly in light of the ecological importance of this group of fishes in marine ecosystems and its conservation state worldwide.

The present study enhances knowledge of the biodiversity of diatoms in Chuuk, Micronesia following our 2018 study on the seaweed-associated diatoms. We collected planktonic samples of diatoms from five sites of reef flats using a 20 μm mesh net, and two samples of seaweeds with epiphytes by hand from an islet on the barrier reef. In addition, the seaweed-associated diatoms from our 2018 study were analysed using scanning electron microscopy. A total of 109 diatom taxa are documented in the present study. Of these, 70 species were from net samples, and 39 species from the seaweed-associated diatoms. Thirty-one species are newly recorded from Micronesian waters. Most taxa are benthic or tychoplanktonic; euplanktonic diatoms were rare. The occurrence of benthic diatoms from the water column might be related to the Chuuk environmental conditions which include shallow water, strong light intensity and high grazing pressure, to which benthic diatoms seem to be able to better adapt than planktonic diatoms.

Nine hundred and ninety-two (992) specimens of Pseudocyclops lerneri Fosshagen, 1968 (Copepoda: Pseudocyclopidae) were collected from the largest South Atlantic coral reef, Abrolhos bank (17°20′–18°10′S; 38°35′–39°20′W). Specimens were distinguished from other Pseudocyclops spp. by a close examination of the female and male fifth leg. This is the first record of the family Pseudocyclopidae in the South Atlantic. We further indicate that the low number of studies on this species, and as a consequence, the poorly understood ecology of Pseudocyclopidae may be caused by the use of inadequate sampling methods, indicating the use of demersal-focused samplers, such as emergence traps as an alternative to the sampling of these bottom-dwelling copepods.