The present study reviews Perinereis Group 2 species from the Eastern and South-eastern Asian seas based on morphological analysis of the types, non-types and original descriptions, and the use of molecular evidence (COI and 16S rDNA) from newly collected material. These species are characterized by having two bar-shaped paragnaths on pharyngeal area VI, which are often deemed conical when small and pointed, triggering misidentifications as to Neanthes species. New terminology and definition for this particular type of bars are proposed, and the generic position of some resembling Neanthes species is also re-assessed. Five species are transferred to Perinereis: Perinereis babuzai comb. nov., P. belawanensis comb. nov., P. kinmenensis comb. nov., P. shigungensis comb. nov. and P. vitabunda comb. nov. ‘Perinereis aibuhitensis’ species group is newly proposed by encompassing species having proximal dorsal ligule similar throughout the body, dorsal cirri short, and blades of heterogomph falcigers straight with long terminal tooth forming a distinct tendon. Perinereis belawanensis comb. nov., P. linea and P. vitabunda comb. nov. are redescribed. Perinereis linea is regarded as a senior synonym of Nereis (Neanthes) orientalis and Perinereis vancaurica tetradentata based on type material, whereas its exotic status in the Mediterranean Sea is questioned. An identification key to all currently valid species within Perinereis Group 2 is also provided.

No prior comprehensive information on the reproductive biology and trophodynamics of Aluterus monoceros was globally available. The present study was performed on 1036 individuals landed along the western Bay of Bengal during 2017 to 2019. Length ranged between 25.3–64.4 cm in females (mean at 48.34 cm) and from 21.5–64.1 cm in males (mean at 47.83 cm). Growth was negatively allometric with no significant difference between sexes. Sex ratio (F:M) was 1.03 with variations based on sizes and months. Size at sexual maturity for females and males was 40.85 and 41.60 cm, respectively. The species spawned throughout the year with major and minor peaks during February to May and October and November. Absolute fecundity increased linearly with length and weight and ranged from 33,640 eggs to 12,39,202 eggs. Stomachs were empty or with trace amounts of food in 59.17%, part-full in 34.07% and full in 6.76% of the fishes. Stomach vacuity and fullness and predator–prey weight ratios varied with an increase in body size, implying higher feeding intensity in large-sized fishes. Feeding activity was more intense during June–August and less during the peak spawning months. The species is omnivorous and a bottom feeder. Teleosts contributed the most to the prey items (43.23% by Index of Preponderance) implying preference for carnivory. Ontogenetic shifts and seasonal variations in prey items were observed. The present study provides paramount information that can significantly contribute to the management and conservation of monacanthid stocks in northern Indian Ocean.

Evolution and population genetic structure of marine species across the Persian Gulf and Gulf of Oman are shaped by two complex factors: the geological history and the present pattern of marine currents. Characterizing and comparing the genetic structures of co-existing species, such as host–parasite associations, allow the discrimination of the relative importance of environmental factors and life history traits that influenced gene flow and demographic events. In this study, we compare two associated Clausidium copepod species (C. persiaensis Sepahvand & Kihara 2017 and C. iranensis Sepahvand, Kihara & Boxshall 2019) along the south coast of Iran in two geological settings. We analysed partial nucleotide sequences of the mtCOI gene using divergence estimates (FST) and haplotype networks to infer intraspecific population connectivity in the two Gulfs. The results obtained demonstrate the existence of two genetically and geographically distinct clades, corresponding to the Persian Gulf and Gulf of Oman populations. Our results also indicate high diversity, population expansion and high connectivity among populations of C. persiaensis and C. iranensis in the Persian Gulf and Gulf of Oman.

This study provided biological information on 146 specimens of the poorly known deepwater mastigoteuthid squid Idioteuthis cordiformis. Mantle length ranged from 200–500 mm for males and 270–702 mm for females. The largest female weighed just under 12 kg. The majority of males were mature and all females were immature. The fins were larger and thicker than the mantle. Mantle weight of males and females was 44.8% and 55.2% of fin weight, respectively, and were significantly different. There was a significant sex effect on mantle length, total weight, mantle weight and fin weight, with females having greater values in all categories. There was a small season effect for mantle weight and fin weight. There was little ingested prey material except fluid and oil in the caecum that was typically bright orange or red. Total fluid volume ranged from 23–230 ml and 20–550 ml for males and females, respectively. The per cent oil component of total fluids in the caecum ranged from 6.9–50% and 10.8–50% for males and females, respectively, with no significant difference in per cent oil between males and females. There was a significant positive relationship between total weight and oil volume for females, and for males and females combined. The function of the oil is uncertain. While this study provided information on sex differences in the body size, sexual dimorphism and caecum oil content, information is still incomplete regarding reproduction due to the lack of any mature females captured in this study.

Fish assemblages inhabiting a complex of south Tyrrhenian seamounts and banks were characterized using a remotely operated vehicle (ROV). Fish distribution was assessed through surveying 15 ROV transects. Video segments of each transect were split into two bathymetric ranges, above and below 200 m depth. In total 28 fish taxa belonging to 22 families were recorded. The number of species observed at the Marettimo Banks and the Aceste Seamount was higher compared with the Tiberio and Scuso Seamounts. The number of species recorded in the shallow part (<200 m depth) of the Marettimo Banks and the Aceste Seamount was higher than in the deeper zone (>200 m). Assemblages were numerically dominated by Anthias anthias, Callanthias ruber and Helicolenus dactylopterus. The occurrence of some elasmobranchs of conservation concern, such as Squatina aculeata, Hexanchus griseus, Squalus blainville and Galeus melastomus, was noteworthy. Differences in fish assemblage composition were observed between the Aceste Seamount and the other sites and especially between the two bathymetric ranges. The fish distribution pattern showed significant relationships with bottom slope and some substrate types. A large occurrence of lost fishing gear characterized the sites closest to the coast (the Marettimo Banks and the Scuso Seamount), providing, along with scanty observations of commercially important fishes, evidence of heavy fishing activities. The adoption of conservation and management actions in the investigated seamounts and banks, such as their inclusion in the Natura 2000 network, would be very helpful to protect some threatened elasmobranchs and restore valuable deep-sea habitats.

Oceanic islands and seamounts are considered biodiversity hotspots. Here, we present a taxonomy and community analyses of hyperiid amphipods collected near oceanic islands and over seamounts of the Juan Fernández Archipelago and Desventuradas Archipelago in the South-east Pacific. Both archipelagos are separated by about 800 km over the meridional gradient, suggesting the existence of different hyperiid communities because of apparent geographic isolation and distinctive oceanographic characteristics between regions. To test this hypothesis, zooplankton samples were collected from 19 stations during the CIMAR 22 ‘Oceanic Island’ cruise in October–November 2016. In total, 56 species of hyperiids were found, of which Phrosina semilunata, Lestrigonus schizogeneios, Hyperietta stephenseni, Hyperioides longipes, Phronimella elongata and Primno latreillei were the most abundant and recurrent species. The species richness (S), Shannon–Wiener diversity (H’) and dominance (D) of both the archipelagos were not significantly different. Additionally, except for a small group of rare species, the species composition was similar in both areas. Most species showed greater abundances than those observed in the coastal upwelling zone off Chile, whereas shared species between regions suggested the presence of a single biogeographic unit comprising the coastal transition zone and oceanic area off Chile within which both archipelagos are included. Correlation analysis indicated that salinity was the best predictor for the community structure, which provides evidence that the contributions of previously described water masses of the South-east Pacific may influence the spatial distribution and composition of the hyperiid community.

Marine capture of Sphyraena putnamae along western Bay of Bengal has been increasing. Owing to scarcity of information available on feeding dynamics globally, the present study was conducted using 763 individuals captured during 2017–19, to decipher trophic ecology and relationships. Of the individuals analysed, 54.8% had their stomachs either empty or with trace amounts of food, 27.3% had part-full stomachs and 18.0% had full stomachs. Stomach vacuity and fullness as well as predator–prey weight ratio varied with increase in body size, implying higher feeding intensity in large-sized fishes. Feeding activity was highest during July–November and lowest during March–April. The species is an opportunistic piscivorous pelagic predator that feeds on teleosts (>85%) and cephalopods. Sardines were the major prey, followed by whitebait, squid, bigeye scad, Indian scad, silverbellies and Indian mackerel. Diet contents were similar between sexes (82.17%); however, it varied among seasons (56.86–69.85%). Shifts in prey preferences from sardines, squid and bigeye scad to ribbonfish, shad, grunter, Indian mackerel, horse mackerel and Acetes were observed with increase in fish size, and diet varied between individuals sized <60.0 and >60.0 cm. Trophic level value was 3.51 ± 0.13 and Levin's Standardized Niche Breadth Index was 0.21. Dietary niche breadth varied across seasons and sizes, with higher values during summer and winter (0.36–0.41) and in fish measuring >45.0 cm (0.50–0.68), which implies generalized feeding behaviour. The present study represents the first detailed report on the diet of S. putnamae and will provide a substantial contribution to stock management through understanding of trophic interactions.

On 19 July 2019 an estimated 20 bottlenose dolphins (Tursiops truncatus) were observed in the Marsdiep, a tidal inlet connecting the North Sea and the Dutch Wadden Sea, between Den Helder and the island of Texel. Photographs and video recordings were made and nine individuals were matched with known dolphins from the Moray Firth, NE Scotland. These are the first matches of this east coast of Scotland population outside the UK and Ireland. Subsequent observations of individuals from this group show that at least some of the animals have returned to Scottish waters, while others were photographed in Danish waters. Furthermore, we report on a photo identification match of a solitary bottlenose dolphin between France and the Netherlands. These matches suggest that bottlenose dolphins, in the Netherlands, originate from two different genetically distinct populations: ‘Coastal South’ and ‘Coastal North’. This evidence of previously unknown long-range movements may have important implications for the conservation and management of this species in European waters.

For decades, the Brazilian north-east coast has been a recognized feeding area for five sea turtle species. However, it still lacks information about stranding patterns. A decade of a beach monitoring programme (from 2010–2019) provided information on the composition, abundance and spatio-temporal distribution of stranded sea turtle species along a semiarid coast in the western equatorial Atlantic. A total of 905 individuals of four species were recorded in a route of ~130 km. The most stranded group was the juvenile green turtles (Chelonia mydas), followed by Lepidochelys olivacea, Eretmochelys imbricata and Caretta caretta. The strandings present a seasonal and geographic pattern, and therefore any conservation measure to be implemented must consider these patterns. Also, the possible occurrence of fibropapillomatosis tumours calls for additional studies to understand its causes. Lastly, stranded sea turtles eventually show marks of fishery interaction, which indicate the need for environmental education programmes with fishing communities.

The reproductive characteristics of co-occurring freespine flathead, Ratabulus diversidens, and mud flathead, Ambiserrula jugosa, that interact with fisheries across continental shelf waters of eastern Australia were examined. Samples were collected across three depth strata and two locations on a monthly basis over two years. Males of both species matured younger and at smaller total lengths (TL) than females. Estimated TL and age (years) at maturity (L50 and A50, respectively) of R. diversidens also varied between locations, but differences were not related to differential growth. Although some mature individuals of both species occurred year-round, they were most prevalent and gonadosomatic indices greatest, between the austral spring and autumn. Mature R. diversidens almost exclusively occurred in deeper offshore waters, whereas the opposite was evident for A. jugosa. Both species displayed asynchronous oocyte development, and were thus considered capable of spawning more than once throughout each spawning season. Potential batch fecundity was positively related to TL for R. diversidens, but not A. jugosa, possibly due to the small size of the latter species. The sex ratios for R. diversidens varied between locations and length categories, and like A. jugosa the larger categories were skewed towards females, a result of divergent growth between sexes. Macroscopic and microscopic evidence indicated both species were gonochoristic. The data provide new information for fisheries management consideration and contribute to the data-poor international knowledge base of platycephalid biology.

The complete larval development of the spider crab Maguimithrax spinosissimus (Lamarck, 1818) is re-described and illustrated in detail from laboratory-reared material. The development consisted of the typical pattern reported for the Majoidea, two zoeal stages and one megalopa. The complete larval development from hatching to first crab lasted 5–6 days at temperatures that ranged between 24–28 °C. Both zoeal stages of M. spinosissimus exhibited moderate reduction in the number of setae in the maxilla and maxillipeds, from the first to the second zoeal stage, when compared with other closely related species. Maguimithrax spinosissimus can be easily distinguished from other species belonging to the closely related genus Mithrax by the (i) setation of the endopod of the maxillule, maxilla and second maxilliped in both zoeal stages; (ii) setation of the scaphognathite of the maxilla in the first zoeal stage; (iii) setation of the basis of maxilliped I in the second zoeal stage and megalopa; (iv) morphology of the antennule and antenna in the second zoeal stage; and (v) setation of the antennule, coxal endite of maxilla, and exopod of second maxilliped in the megalopa. All these characters support the recent generic status of Maguimithrax within the Mithracidae. Additional morphological details, not available previously, are provided. This study will provide support for conservation strategies in this species.

The present study reports polychaetes that bore into limestone rocks along the east coast of the Aegean Sea (eastern Mediterranean). Rock materials were collected at two depth intervals (0–5 and 5–10 m) at 15 stations in four localities of Ildırı Bay. A total of 276 specimens belonging to 12 species and four families (Eunicidae, Spionidae, Cirratulidae and Sabellidae) were recorded. Specimens belonging to Dodecaceria and Pseudopotamilla were identified at the genus level, because they differ from described species, were few in number or were in poor condition. Dipolydora giardia is a new species to the marine fauna of Turkey. The most dominant and frequent family in the area was Eunicidae, followed by Spionidae. Lysidice ninetta and L. margaritacea comprised 59% of the total number of individuals. The number of species and individuals, and the diversity index did not change with regard to depth or locality. Two species assemblages were found in the area, mainly formed by Dipolydora and Lysidice species. The Lessepsian species, Palola valida, which is a new record for the Aegean Sea, occurred abundantly at the study sites, posing a risk of damage to limestone rocks in the Mediterranean Sea. The morphological features of the species identified at the generic level and the burrow structure of these species are presented. The burrow shapes of Palola siciliensis and P. valida were described for the first time in the present study; they constructed complicated galleries, including more than four entrances.

In this letter we highlight the inconsistencies and dismantle the arguments used by Korshunova et al. (2021) where the authors have treated the nudibranch species Polycera norvegica as a junior synonym of Polycera capitata (original designation: Thecacera capitata). We show that in accordance with the International Code of Zoological Nomenclature, Thecacera capitata should be considered a nomen dubium, and we reinstate Polycera norvegica as the valid name of this species.

We report two separate sightings of the ornate eagle ray Aetomylaeus vespertilio (Bleeker, 1852) in the Bazaruto Seascape of southern Mozambique. In May 2021, a single individual was encountered at a depth of 30 m during an in-water survey in the Bazaruto Archipelago National Park. Another solitary individual was documented ~55 km away during an aerial survey in the Vilanculos Coastal Wildlife Sanctuary three days later. These represent the first documented sightings of A. vespertilio in the Inhambane Province of Mozambique, confirming the presence of the species in the region and extending the known range northward along the south-east African coastline. Given the rarity of reported sightings, additional records are particularly valuable for these threatened and elusive rays in order to expand current knowledge of their distribution and range.

The humpback whales which breed in the Mexican Pacific represent an important fraction (~38%) of the estimated population of the North Pacific. Despite the importance of Mexican waters for the reproductive habits of this species, little is known about the ecology of these whales, along the continental coast of Mexico. We analysed the temporal variation of abundance, group types, and inter- and intra-annual recapture rates in the waters adjacent to Isabel Island National Park as well as intra- and inter-seasonal movements with Banderas Bay breeding areas. Inter- and intra-annual recapture rates in Isabel Island National Park were low (1.8%); while 34% of 222 individuals photo-identified in Isabel Island National Park were also recaptured in Banderas Bay. Groups with calves were uncommon (9.5%), while pairs (33.5%) and competitive groups (29.5%) were more common. Intense singing activity was detected in the waters adjacent to Isabel Island. These waters seem to function as a reproductive corridor for the so-called ‘coastal stock’ of humpback whales in the waters adjacent to the continental coast of the Mexican Pacific. Therefore, mid- and long-term studies are needed to understand the dynamics of these displacements. Our findings suggest that Isabel Island National Park is an important area for the mating ecology of the humpback whales of the continental waters of the Mexican coast, and support the initiative to incorporate a Marine Protected Area within the Isabel Island National Park.

Ecological and biogeographic information for marine gastropods has lagged behind taxonomic, molecular and phylogenetic information, limiting understanding of evolutionary processes. We investigated niche separation and speciation in rapinine whelks that represent a rare deep estuarine penetration by muricid gastropods. We studied the genetic and ecological differentiation of four Indothais morphotypes, distributed along a salinity gradient in Brunei (Borneo, South East Asia). Our molecular analyses, based on three mitochondrial genes (COI, 12S rRNA and 16S rRNA) and one nuclear gene (28S rRNA), revealed three species having the following relationship [Indothais rufotincta (Tan & Sigurdsson, 1996), [I. javanica (Philippi, 1848), [I. gradata (Jonas, 1846)]]]. This pattern coincided with their salinity-related distributions, such that I. rufotincta occurred alone in the open coastal waters, and I. javanica and I. gradata extended into the upper estuary. This suggests speciation through divergent selection and local adaptation, specifically synapomorphic low salinity tolerance by I. javanica and I. gradata. The observed intertidal vertical separation where the species co-occur suggests competitive exclusion of the others by the most-recently evolved I. gradata. This species also showed greatest morphological and genetic variation, and unique niche expansion involving feeding on both hard surface and muddy sediment organisms. Our study presents a novel hypothesis for the speciation of these snails.

The peacock-tail shrimp Ancylocaris brevicarpalis Schenkel, 1902, is an obligate symbiont of sea anemones and well known for its remarkable colouration. Yet, very little information is available about its population structure and life-history traits, including reproductive parameters (fecundity, embryo volume and reproductive output). A total of 574 individuals were collected from the Gulf of Mannar, Tamil Nadu, India between February 2017 and July 2018, out of which 214 were males (37.28%), 355 were females (61.84%), and 5 (0.87%) juveniles. The highest percentage of individuals were observed in the post-monsoon season (38.10%) followed by monsoon (34.85%), pre-monsoon (15.02%), and summer seasons (12.01%). The overall sex ratio was skewed towards female individuals (0.55 male: 1 female). Fecundity was higher in females carrying early-stage embryos and embryo volume did increase, but not statistically significantly from early to late stages. The reproductive output was negatively allometric to the mean female body weight. The present study provides first-of-its-kind information on the population as well as individual-level reproductive characteristics of A. brevicarpalis.

The Caymanostellidae is a family of rarely encountered wood-dwelling deep-sea sea-stars, with only six species, in two genera, described to date. During the COBERPES 5 expedition on board the RV ‘Justo Sierra’, off Tabasco, Gulf of Mexico in 2013, 12 specimens were recovered from a single piece of sunken wood. Herein we describe a new genus and species of caymanostellid, Crinitostella laguardai gen. nov., sp. nov. This species represents the shallowest known caymanostellid (418–427 m depth), and the first known occurrence of the Caymanostellidae from the Gulf of Mexico. The family Caymanostellidae displays affinities with several groups, such as Asterinidae and Korethrasteridae, making it difficult to infer its phylogenetic position evidenced by the myriad of contrasting phylogenetic hypotheses proposed. In an attempt to shed some light on the phylogenetic relationships of the family, sequences of nuclear and mitochondrial DNA of the new species were generated and combined with published data. As previously suggested, caymanostellids seem to be part of valvatacean polytomy rather than velatids.

Sagittal otolith morphology and otolith shape of two megrim species, Lepidorhombus boscii and Lepidorhombus whiffiagonis, were compared using descriptive morphological characters and Wavelet shape coefficients. Differences in otolith shape were examined by linear discriminant analysis (LDA). The first discriminant axis explained 66.6% of the variation between the groups, and the second axis 28.5%. Otolith classification based on LDA showed that in 79.5% of cases an otolith can be correctly classified based only on its shape. Relationships between otolith morphometric parameters (length and width) and fish size (total length) were described by fitting simple linear regression models. For L. boscii the highest positive correlation was found between right otolith width and total body length (R2 = 0.82), and for L. whiffiagonis between left otolith length and total body length (R2 = 0.39).