The goniadid polychaete Goniadella gracilis (Verrill, 1873), currently considered as a non-indigenous species in European waters, is reported for the first time in Italian waters of the Tyrrhenian and Ionian Seas. A detailed description of individuals of this species from the Mediterranean Sea is provided, including the pigmentation pattern of the specimens, which to our knowledge has never been reported before in literature. In addition, new molecular data, 18S and COI sequences, from Mediterranean specimens are presented and compared with data from the North-Eastern Atlantic. On the basis of the available evidence, the status of G. gracilis in the Mediterranean basin is discussed, and the species is here proposed to be considered as a questionable species in the area.

Calcifying macroalgae play a critical role in coastal ecosystems, but rising sea temperatures pose a significant threat to their survival. This study aims to investigate the thermal sensitivity of the three marine macroalgal species Padina boryana, Halimeda opuntia, and H. macroloba. Photosynthetic performance, metabolism, pigment content, and oxidative stress–related parameters were measured at temperatures of 28°C, 32°C, 36°C, and 40°C and the thermal performance curves (TPCs) were determined for Fv/Fm, Fv/F0, ϕPSII, and oxygen production to assess maximum rate (Rmax), optimum temperature (Topt), critical thermal maximum (CTmax), and thermal safety margin (TSM) of these three macroalgal species. The results showed that 40°C had the most negative effect on all three species with P. boryana demonstrating better performance compared to both Halimeda species. TPCs from photosynthetic performance revealed thermal sensitivity variations by species and P. boryana exhibited a broader thermal tolerance range compared to Halimeda. On the other hand, TPCs of oxygen production provided similar CTmax values. Based on TPC projections, all three species might survive future ocean warming and marine heatwaves, though these conditions will have significant effects, with P. boryana showing greater tolerance than both Halimeda species. This study highlights the differential thermal responses and sensitivities of these macroalgae, contributing to understanding their potential resiliencies under future climate change scenarios.

Many ascidian (sea squirt) species are common members of fouling communities, particularly on floating substrates such as docks and pilings and through maritime transport, have been introduced worldwide. For the past 30 years, marinas in Southern California have been regularly monitored for introduced species due to their proximity to the international shipping terminals in Los Angeles and Long Beach Harbors. Here, we report on the first record in the eastern Pacific of an ascidian in the family Corellidae (O. Phlebobranchia), Corella japonica, found at the Newmarks Yacht Centre in Los Angeles Harbor. This study further highlights the importance of continuously monitoring harbors and marinas to detect the early arrival of new non-native species.

Fjord ecosystems serve as crucial habitats for elasmobranchs, supporting them across all life stages. Chilean Patagonia provides one of the most complex and extensive networks of fjord ecosystems in the world, displaying high marine biodiversity, including elasmobranchs. However, little is known about this ecologically important group of fishes in these ecosystems. This study investigates the biodiversity of elasmobranchs in the Comau Fjord over a period of 6 months by combining morphological and molecular data. In total, 309 specimens within a radius of 7.5 km were recorded, belonging to six families and nine species: Hexanchus griseus (77.5–178 cm LT), Notorynchus cepedianus (180.6 cm LT), Schroederichthys bivius (35–65.2 cm LT), Scymnodon macracanthus (37.3 cm LT), Centrophorus squamosus (87.4 cm LT), Deania calceus (58.3–98.6 cm LT), Squalus acanthias (25.5–101.1 cm LT), Dipturus chilensis (62.9–152 cm LT), and Dipturus trachyderma (69.8–194 cm LT). This included records of three species previously unknown in the fjord and was equivalent to nearly 20% of the elasmobranch richness found in Southern Chile. The results further suggest that the Comau Fjord could be a primary nursery ground for several species of elasmobranchs. This is the first time that a species inventory of elasmobranchs is conducted in a Chilean fjord system. The outcomes of this research provide an elasmobranch species checklist with biological aspects from the Comau Fjord, which are essential data to inform decision makers, conservation managers, and future research.

Polychaetes (Phylum Annelida) respond to sensory stimuli through the usage of sensory organs and appendages, such as palps, which vary in shape and structure depending on lifestyle. The typical palps of nereidid polychaetes are tapered appendages constituted by two articles. The palpophore is the wider and longer basal article, followed by the thinner and shorter palpostyle that contains the majority of sensory cells. Previous studies on Hediste diversicolor palps were focused on these sensory cells. To achieve a more comprehensive view of the histology and ultrastructure of the palps, H. diversicolor specimens were collected from the northern Portuguese Atlantic coast and the palps were processes for light (semithin sections) and transmission electron microscopy. The current study revealed details of the cuticle, which is thinner in the palpostyle than in the palpophore. Five types of secretory cells were distinguished mainly based on the characteristics of their secretory vesicles. Two of these types could be classified as protein-secreting cells, and the other three as mucus-secreting cells. Granulocytes and eleocytes were found in the celom cavity of the palps. The latter contained lipid droplets and a very large amount of glycogen. In the central region of the palpophore, a ring of muscle cells responsible for the retraction of the palpostyle encircled the main palp nerve. The latter was formed by numerous axons and glial cells containing bundles of filaments and gliosomes.

Anthuroid isopods in the genus Mesanthura (52 valid species) typically have a body with conspicuous dorsal pigmentation, with differences in the female pigmentation pattern being one of the main characters used to distinguish species. Five Mesanthura species have been reported to date from Japan. Here, we describe Mesanthura sol sp. nov. from Irabu Island and Okinawa main island, Okinawa, Japan, and illustrate its sexual dimorphism in colour pattern, with conspecificity between males and females confirmed with molecular data. We provide a description of Mesanthura miyakoensis based on specimens collected from Kochi, Shikoku, Japan. We present the first records of Mesanthura cinctula and Mesanthura nigrodorsalis, following their original descriptions. Finally, we provide partial sequences of the 16S rRNA gene for these four species and present a phylogenetic tree based on the sequences.

Brittle stars undergo remarkable morphological changes during their transition to adulthood, extending beyond metamorphosis. Members of the genus Ophioderma exhibit particularly noteworthy morphological changes between the juvenile and adult stages. These growth changes have been a persistent source of misidentification in Ophioderma, even leading to the misclassification of juveniles to a different genus. In this study, the growth changes of three common eastern Pacific Ophioderma species were characterised: Ophioderma aija, Ophioderma occultum, and Ophioderma panamense. Their growth series, ranging from 2.5 to 26.7 mm disc diameter, were analysed by combining morphology, morphometrics, and DNA barcoding. Three size groups within the species were identified. In general, the morphological changes shown by the three species were highly similar and occurred at comparable sizes, allowing a pattern to be identified and reconstructed. However, differences between the species were observed throughout the series in quantitative (arm length, dorsal arm plates, number of arm spines) and qualitative (radial shields, colouration) characters. This work represents one of the few available contributions on the growth changes of Ophiuroidea from the eastern Pacific and so far in the genus Ophioderma.

Despite the importance of the commercially harvested benthopelagic fish Beryx mollis, little information is available on their adult phase and reproduction. This is likely due to the low abundance of this species compared to Beryx splendens and Beryx decadactylus as well as misidentification of Beryx spp. In this study, early life stages of B. mollis were found in the southwest region off Sri Lanka during a survey with research vessel Dr Fridtjof Nansen in 2018, coinciding with the southwest monsoon period. As morphological characteristics of eggs and larval stages of the three Beryx spp. are very similar, visual identification to differentiate to species level has always been challenging. Therefore, in this study, DNA barcoding was carried out targeting the mitochondrial COI gene. Molecular analysis confirmed that the collected egg and larvae belonged to the B. mollis species due to their high identity (>99%) with reference to previously submitted adult B. mollis sequences in the GenBank. Phylogenetic analysis showed a closer evolutionary relationship among B. mollis and B. splendens than with B. decadactylus. To the best of our knowledge this is the first genetic and morphological confirmation of B. mollis egg and larvae worldwide and suggests the southwest coastal area in Sri Lanka, in the north central Indian Ocean, as a potential spawning ground for this species.

Although octopuses are the third most fished marine invertebrate species in Puerto Rico, there is a lack of information about this fishery. Here, we present the first small-scale study assessing the genetic diversity and connectivity of Octopus vulgaris in Puerto Rico. To achieve this, we applied double-digest restriction-site associated DNA sequencing, using the restriction enzymes EcoRI and SphI in 43 specimens captured from ten locations representing three geographic regions. We used F-statistics and Bayesian analysis to evaluate over 2000 polymorphic loci. We found high genetic connectivity (FST = 0.0008, FST = 0.005), high nucleotide diversity (π ≈ 0.1), and moderate genetic diversity (HO ≈ 0.255–0.361, HE ≈ 0.258–0.373) between the studied regions. In contrast to our expectations, given oceanographic characteristics and distance between the geographic regions, our results suggest a single admixed population of O. vulgaris in Puerto Rico, with no differentiation between the sampled regions. Even though genomics techniques are powerful for inferring population connectivity, researchers should be cognizant of protocol limitations to retain the most reliable information possible.

A single specimen of the Australian stargazer, Xenocephalus australiensis, was recently collected from the southwest coast of India, Arabian Sea. Since its original description, from northwest Australia, there have been no detailed reports on the species occurrence. The present study documents the first geographical record of X. australiensis in the Arabian Sea, Western Indian Ocean. Morphological characters are enumerated and compared with the voucher specimens from the original description. A detailed description of the specimen is provided, contributing valuable insights into the characteristics of X. australiensis in the Indian waters along with major distinguishing characters of the species in the genus Xenocephalus. This study extends the known geographic range of the species from northwest Australia, Eastern Indian Ocean, to the Arabian Sea, Western Indian Ocean.

Eels of the congrid genus Coloconger are rare and poorly known for their distributions. This study reports on the collection of the Indo-west Pacific short tail conger Coloconger scholesi Chan 1967 from Indian waters of the Arabian sea for the first time based on a single specimen collected from the deep waters off Kollam, Kerala and provides an additional report about Anguilliformes of India. Previously a single species of the genus Coloconger raniceps Alcock 1889 has been reported from Indian waters up to now. This study adds details about another Coloconger species, C. scholesi, a photograph of the specimen in fresh condition is provided, and comparison with its co-occurring in Indian waters congener C. raniceps is included.

Saltmarshes are widely recognized as one of the most productive coastal habitats, and on the Amazon coast, Spartina alterniflora marshes are widespread on both marine and freshwater sites. On the Amazon coast, this ecosystem is subject to a wide array of environmental factors that influence its characteristics and associated macrobenthic fauna. However, few studies have been carried out in Amazonian saltmarshes when compared to others regions worldwide. Therefore, this study characterizes the vertical distribution of macrobenthic fauna in Amazon saltmarshes and their seasonal changes. Vertical stratified samples (0–10 and 10–20 cm) were collected during the rainy (April 2008) and dry seasons (November 2008) in saltmarshes located in an Environmental Protected Area located on the Northern Brazilian Amazon coast (Algodoal-Maiandeua island). The saltmarsh area varied between seasons, being denser and taller in the dry season. A total of 38 macrobenthic taxa were recorded, of which 11 were exclusively found in the dry season. The macrobenthic faunal structure varies among seasons, with higher density and richness in the dry season. Overall, higher densities and richness were found at near-surface layers in both seasons. We suggest that the vertical distribution of the macrobenthic fauna depend on the vegetation density in Amazon saltmarshes, since this vertical distribution is more prominent in the dry season where we observed higher Spartina density and most of the fauna is concentrated near the surface. Therefore, this study provides novel insights into macrobenthic distribution patterns, reinforcing that Amazonian saltmarshes have unique characteristics that strongly influence their distribution.

Climate change profoundly affects plant phenology. An important parameter in research on plant dynamics is the plastochrone interval (PI), which is define as the time interval between the formation of successive leaves. The PI has been used to evaluate seagrass demography and as a direct measure of shoot growth and age. Variations in PI determine the growth rates, maintenance, and success of seagrass beds. Global warming could affect the PI dynamics of Zostera marina and, consequently, alter the dynamics of seagrass beds. Using Bayesian linear regression with a time series composed of 316 biweekly sampling dates from 1998 to 2018, we evaluated PI dynamics in the Punta Banda Estuary in Baja California, Mexico. We found that the tendency of the series was linear with parameter values of β0 = 1.65 (SD ±0.19) and β1 = −0.012 (SD ±0. 001). The Bayesian analysis of variance showed strong evidence of differences in the PI among years, given probabilities from 3.2 to 1.88 × 106 times higher of differences than no differences. The largest differences were detected between cold and hot years. The climatology of the time series PI values showed changes in seasonality over time. Summer and autumn were found to be the most perturbed seasons. Finally, by linking the PI estimates with the sea surface temperature anomalies for the complete series, a good inverse correspondence was observed between hot years and high PI, as well as cold years and low PI values, suggesting that climate change has affected PI among years and seasons.

The pebble crab, Leucisca levigena, was recorded for the first time from the intertidal regions of South Andaman in the Andaman and Nicobar Islands, India. This comes after its holotype was described in 1976 from Western Australia. The species was found on the thallus of the green seaweed, Halimeda opuntia. Notably, the study included the first record of a male specimen, previously absent in its first description. L. levigena is characterized by its slightly concave dorsal carapace with a beaded margin, a raised gastric region extending to the front, and a smooth pterygostomial region. A brief description and illustrations of both the male and female species and a map showing the distribution of Leucisca species around the world are provided. L. levigena confirms its distribution from Western Australia to the Andaman Islands.

Coastal ecosystems have been subject to anthropogenic environmental stressors. Although exposed to different environmental pressures and susceptible to bioinvasion events, Todos-os-Santos Bay (TSB) (12oS, Bahia State, Brazil) has great ecological importance. Among the bioinvasive organisms, Tubastraea corals (the ‘sun corals’) are widespread in artificial and natural environments of the TSB less frequently. Given the lack of baseline information characterizing the original biofouling communities, surveys approaching the malacofauna under the influence of sun corals are essential to the knowledge of local biodiversity and future losses due to possible environmental changes. To provide information on the diversity of the malacofauna, the gastropods, bivalves, and polyplacophorans in the presence of sun corals at 10 sampling stations in the TSB were investigated. Eighty-one taxa of different size classes (micro- and macromolluscs) and mobility (mobile and sessile) were recorded. These species belong to distinct trophic groups (carnivorous, herbivorous, grazers, parasites, and suspensivorous/passive filtering) and life modes (endolithic, epifauna, infauna, and ectoparasitic). Gastropoda had the highest number of species, followed by Bivalvia and Polyplacophora. Cerithiopsidae and Pyramidellidae were the most representative families. Three exotic species and seven new records were identified for the bay. The malacofauna associated with artificial substrates with the presence of sun coral proved to be complex and diverse.

In situ observation of cephalopods is crucial for understanding their behaviour, ecology, and natural interactions. Scientific diving offers a minimally invasive approach to studying these elusive organisms, especially in shallow waters. This systematic review evaluates the application of scientific diving in cephalopod research over the past five decades, analysing trends, methodologies, and global representation. An initial database search was conducted, followed by a second, more targeted search to improve accuracy and coverage. This two-stage process significantly increased the capture rate of relevant studies, from an estimated 28% to 57%, of 225 publications meeting inclusion criteria since 1973. In total, 83 different species were studied, with Octopus cf vulgaris being the most recurrent complex species. Most studies were conducted within recreational and non-decompression diving limits, resulting in a higher representation of orders typically found within these depth ranges: Octopoda (52.7%), Sepiida (19.8%), and Myopsida (18.7%). Orders often inhabiting greater depths, such as Nautilida (4.9%) and Oegopsida (3.8%), were studied primarily through video recordings, egg collections, or specimen release. Manual collection (44%) and direct observations (35%) were the primary goal for diving uses. Publications concentrated in regions such as the West Coast of North and South America and the Mediterranean, with the United States leading contributions (21.2%). The initial under-representation of studies was largely due to inconsistent terminology and lack of direct reference to diving methods in titles, abstracts, or keywords. These findings highlight the need for standardized reporting to fully leverage scientific diving’s potential in cephalopod research.

Studying deep-water shark species presents inherent challenges stemming from the difficulty in accessing their habitats, coupled with factors such as low population densities, intricate behaviours, and complex biological attributes. The integration of citizen scientists, particularly fishers, offers a valuable avenue to make use of their life-long insights and expertise, thus facilitating the acquisition of crucial data that can effectively enhance the realm of shark research. Our collaborative engagement with fishers since 2017 has yielded an extensive documentation concerning elasmobranchs in the Caribbean region of Puerto Rico providing a unique opportunity to formally record species hitherto unreported. This is exemplified by the first documentation of the smalltooth sandtiger shark (Odontaspis ferox (Risso, 1810)). Despite its broad geographic range and widespread distribution in temperate and tropical marine environments, there is a lack of comprehensive scientific understanding and limited available knowledge regarding this species. A noteworthy finding on December 30, 2020, near Rincón (northwest coast) in Puerto Rico, disclosed a large shark that an experienced fisher had captured as an unidentified by-catch at a depth of 325 m. Through an interdisciplinary approach using molecular (355 bp, Cytochrome Oxidase Subunit 1) and morphological techniques, we successfully confirmed the identity of the specimen as a female smalltooth sandtiger shark. Given the limited information available (e.g., diversity, abundance, behaviour, reproduction, distribution) on shark species in the coastal and deep waters of Puerto Rico, this report provides valuable new data that can significantly contribute to the conservation efforts to protect these enigmatic yet ecologically vital predators.

This study marks the first update on Malaysia’s marine tardigrades after more than 50 years, presenting both the discovery of a new species, Batillipes malaysianus sp. nov., and a new record, Batillipes rotundiculus. The specimens were collected from the intertidal zone at Pantai Pancur Hitam, Labuan, Malaysia, during two separate sampling efforts. Despite extensive sampling, the density of marine tardigrades in the area was found to be exceptionally low, with only a single specimen of B. malaysianus sp. nov. and a limited number of other Batillipes individuals collected. The new species, B. malaysianus sp. nov., is distinguished by unique morphological features, including setae scattered across the ventral cuticle – a trait not observed in any other species of the genus – and constricted primary clavae, a characteristic absent in other species of the B1 toe arrangement group. Additionally, B. rotundiculus represents the first confirmed record of this species in Malaysia, expanding its known distribution. This study also updates the global species count of Batillipes to 42, incorporating recent taxonomic changes and this new addition. An updated dichotomous key for the genus is provided, incorporating all species described to date. These findings underscore the importance of exploring understudied marine habitats and highlight the potential for discovering more tardigrade species in Malaysia.

Ficopomatus uschakovi has been reported in Galveston Bay (GB), Texas, USA, in taxonomic lists and studies of biofouling communities since 2017; however, after 2 years (from 2022 to 2024) of no observations of this species in the system, we report the first seasonal outbreak after the landfall of Hurricane Beryl in the summer of 2024, followed by 2 weeks of heavy rain, decreasing the salinity at the collection site. In this study, we provide the first genetic characterization of the specimens of F. cf. uschakovi from GB using mitochondrial cytochrome oxidase b DNA sequence data. Results demonstrated that specimens of F. cf. uschakovi in GB belong to the same genetic species as reported on both of coasts of Mexico, the Gulf coast of Florida, and Thailand. The presence of shared haplotypes suggests possible initial introduction from Asia and subsequent expansion of F. cf. uschakovi populations. The comparison of the morphological characters with reports from nearby localities showed a variation in the number of rows and spines on the operculum and in the tube colouration. This study highlights the importance of morphological and genetic analysis for reliable identification of invasive species, the need for wide geographical sampling, as well as examinations of the ecological drivers of F. cf. uschakovi outbreaks.