A new species of parasitic isopod of the genus Ovobopyrus is described from one parasitized specimen of the snapping shrimp Alpheus carlae, collected from the state of Pernambuco, northeastern Brazil. It is the second species of the genus and the first record of the genus from Brazil. The adult female of Ovobopyrus odoya sp. nov. is diagnosed by having the head produced into small anterolateral projections: antennule with three articles; maxilliped subquadratic with a non-articulated palp bearing nine long setae, oostegite 1 having a digitate ridge with five small lobes, carpi of all pereopods with tufts of setae distally, and terminal pleomere bilobed. A comparative table, an identification key, and a distribution map for species of the genus are provided. In addition, an identification key for all Bopyrinae genera from Brazil is also provided.

The presence of the zebrette goby (Tigrigobius zebrellus) is reported for the first time in the Canary Islands, as well as in the eastern Atlantic. A new established colony around the floating docks of the Marina Santa Cruz de Tenerife harbour has been studied. Over two hundred individuals at different developmental stages have been counted. Its restricted distribution and population characteristic show that it has an established population but with no evidence of expansion to its vicinity. Our study indicates that the population of this exotic species could be easily eradicated to avoid any possible negative impact on local benthic communities. However, if such measures are not soon implemented by the local government this study can also be used as the early invasion stage of an exotic fish species across the Canary Islands.

A specimen of the genus Pandeopsis Kramp, 1959 was found in surface waters off the northeast Brazilian coast at 10.93°S, 36.48°W. The specimen was assigned to the family Pandeidae on the basis of the presence of more than four hollow marginal tentacles and the absence of divided radial canals, marginal tentacles with terminal cnidocyst cluster, and oral tentacles. Among Pandeidae, the specimen was assigned to Pandeopsis due to the absence of lateral diverticula, centripetal canals, and marginal cirri as well as the presence of more than two marginal tentacles, mesenteries, smooth gonads, and manubrium with a quadrangular base. To the moment, the unique morphological trait that is likely to distinguish the two species of the genus is the presence of medusa buds in the gonads of Pandeopsis prolifera, which was not present in the specimen we found. However, as this is not a strong trait to distinguish species, we consider the present specimen to be Pandeopsis cf. ikarii. This study represents the first record of the genus in the South Atlantic Ocean.

The genus Echinaster in Japanese waters was revised, resulting in the discovery of two new species, E. crystallus n. sp. and E. toyoshiomaruae n. sp., and one newly recorded species, E. stereosomus, from Japan. Molecular phylogenetic analyses including 22 echinasterid species indicate that another newly recorded species, Metrodira subulata, is grouped with the other Echinaster species. Since the revised diagnostic characteristics of the genus Echinaster are consistent with the morphology of Metrodira, we newly synonymize this genus with Echinaster. Consequently, the genus Echinaster includes six species in Japanese waters. Morphological descriptions of all Japanese Echinaster species were provided.

The cyclopoid family Bomolochidae Claus, 1875 is one of the most common groups of parasitic copepods infesting fishes worldwide. During a survey of marine fishes from northeast Brazil, a new species of Naricolax Ho, Do & Kasahara, 1983 was found in the nasal cavities of the littlescale threadfin Polydactylus oligodon (Günther, 1860) (Polynemidae) in the Maranhão Gulf, Brazil. Naricolax zafirae sp. nov. can be distinguished from all congeners because it has a pair of acutely pointed tines in the rostral area and an elongated last endopodal segment of leg 4, features that have never been reported in the genus. In addition, the new species differs from the closely related congeners by having a T-shaped rostral area, an outer spine on the second endopodal segment of leg 3 shorter than the segment, and by the apical seta on the last endopodal segment of leg 4 shorter than the rami. The present study provides the first report of a bomolochid parasitizing a fish of the family Polynemidae Rafinesque, 1815 as well as the first report of the genus Naricolax in the Atlantic Ocean. A dichotomous key for species of Naricolax is provided.

The Gulf of California, one of the world’s most biodiverse marine ecosystems, is also heavily exploited by fisheries. Among its fish fauna are species that, although currently underappreciated, may become commercially important in the future. Enhancing our biological knowledge of these species is crucial for monitoring population dynamics and community changes. Fish parasites offer valuable insights into host ecology, including feeding habits and population structure. In this study, we document the metazoan parasite fauna of Trichiurus nitens (Trichiuridae) from four locations in the eastern Gulf of California, Mexico. A total of 165 fish specimens were examined, revealing five parasite species identified using both morphological characteristics and molecular markers: the monogenean Octoplectanocotyla travassosi, the trematode Lecithochirium sinaloense, and three nematodes – Anisakis typica A, Skrjabinisakis brevispiculata, and Spinitectus sp. Among these, L. sinaloense was the most prevalent. Although parasite species richness was similar between small and large fish, overall parasite abundance was higher in larger specimens. Moreover, parasite assemblages did not vary significantly across the study locations. These findings suggest that T. nitens exhibits a specialized feeding strategy, relying on a narrow range of prey throughout its life, and that the oceanographic variability does not limit fish movement in the region. Future studies encompassing a broader geographical scale, additional fish size classes, and different climatic seasons are needed to further elucidate the ecological role of this species. This work provides novel insights into the host-parasite dynamics of T. nitens and establishes a valuable baseline for ecosystem monitoring under global change scenarios.

Perna perna mussel is a coastal benthic filter-feeder widely cultivated in mytiliculture farms and serves as a resource for local communities engaged in its harvest along the Brazilian coast. This study presents the isotopic ratios (δ13C and δ15N) in the soft tissues of adult mussels from six natural populations in Rio de Janeiro State, southeast Brazil, to evaluate whether they are sensitive enough to distinguish the origin of specimens. The COVID-19 pandemic served as temporal reference, as the quality of coastal waters was influenced by the restrictions imposed during the pandemic. The mean values of δ13C and δ15N ranged from −19.5‰ to −17.3‰, and 6.2‰ to 10.5‰, respectively. The spatial variation of δ13C-δ15N data in the analysed mussels was greater than the temporal variation. The k-means clustering method correctly identified 80% of populations during the pre-pandemic period, 67% in the pandemic, and 50% in the post-pandemic. In most samples, the spatial variation of δ15N (tracer of food source variability) was the primary variable distinguishing the groups of mussels. The isotopic ratios did not reveal a clear trend when using the COVID-19 pandemic as temporal reference. Consequently, the positive environmental changes brought about by the suspension or reduction of anthropogenic activities in coastal waters during the pandemic had minimal impact on the isotopic ratios of mussels at most sampling sites. The utilisation of δ13C-δ15N data to trace the origin of P. perna mussel from natural banks was only partially effective in distinguishing the origin of natural populations across the studied area.

This study provides the first case reported of Paraprionospio treadwelli (Hartman, 1951) in the Gulf of Mexico. Based on 242 individuals collected between 20.8 and 176 m depth during three oceanographic expeditions, we describe in detail the morphology of the identified specimens, including the description of the pygidium, so far unknown in this species, and provide SEM photographs to support their identification. Paraprionospio treadwelli was originally found in Chesapeake Bay, Northwestern Atlantic, and we now extend its distribution southwards to the Western Gulf of Mexico. Remarks on the environmental conditions where this spionid species was found and the observed abundance seasonal pattern are also provided.

The unique reproductive strategies of botryllid ascidians, which include both asexual and sexual mechanisms as well as an extensive capacity for regeneration, contribute to their fast population growth and wide-ranging ecological effects. These colonial organisms have unique ecological adaptations and responses to environmental factors, yet comprehensive comparative studies on their environmental preferences remain scarce. We conducted an experimental study to explore the asexual reproduction and regeneration response of Botrylloides niger and Botryllus humilis colonies to varying salinity (36.5–39.5 PSU) and temperature (26 ± 1–30 ± 1°C) levels. Experimental findings highlighted species-specific preferences and stress responses: B. niger demonstrated higher tolerance to elevated salinity (39.5 PSU) with optimal growth rates at 26 ± 1–30 ± 1°C, whereas B. humilis displayed a preference for lower salinity and tendencies towards vascular budding at higher temperatures (30 ± 1°C). These observations suggest potential niche differentiation and ecological success, particularly in Mediterranean conditions, implying possible coexistence without intense competition in similar habitats. This research offers insights into the adaptive mechanisms of these ascidians, shedding light on their ecological roles and potential implications in coastal ecosystems amid changing environmental scenarios.

Cancer, a multifactorial and heterogeneous disease, poses a significant global health challenge. Despite current treatments such as surgery, radiotherapy, and chemotherapy, tumour recurrence and treatment side effects are common. These pitfalls necessitate a dire need for alternative therapeutic strategies with minimal side effects. This necessity has broadened the horizons of drug discovery into the marine domain, an exciting frontier for novel therapeutic agents. The marine ecosystem serves as a hub of diverse chemical groups with potential anti-cancer properties. Few marine-derived drugs are approved for cancer, and preliminary studies show that marine lead compounds can inhibit cancer cell growth and induce apoptosis. In this context, this review encapsulates an overview of ‘the current state of marine biodiscovery’. It explores the ‘potential of marine natural products in combating cancer’ with a particular focus on glioblastoma multiforme as a case study. Additionally, it discusses the ‘key strategies for advancing marine-derived anti-cancer compounds from the research stage to clinical use’. By tapping into the vast, unlocking the hidden treasures of the ocean, marine natural compounds could offer a hopeful perspective in the fight against cancer.

This study investigated intestinal retraction and regeneration in the Japanese sea cucumber (Apostichopus japonicus) during high water temperature periods and compared these morphological changes with those during low water temperature conditions in the subarctic. We examined the intestinal morphology of A. japonicus during the aestivation and winter low-activity periods under natural-like environmental conditions, including the water temperature, photoperiod, and seawater quality. Water temperatures ranged from −1.1°C to 29.2°C. Aestivating individuals were observed from July to September when water temperatures were high. During this period, intestinal length, weight, and thickness decreased, with signs of recovery by November. The mucosal layer height also decreased, with partial loss or disappearance. In contrast, no intestinal retraction occurred from January to March at low temperatures. Additionally, under high temperatures, the muscle layer thinned significantly, and lipofuscin-like granules, thought to be residual material from intracellular digestion by lysosomes, appeared in the submucosal layer. A common feature in both temperature periods was the presence of haemolymph-like cells in the submucosal layer near the mucosa. These findings suggest that intestinal retraction and degeneration in A. japonicus under high temperatures may result from energy conservation mechanisms, fasting, or reduced food intake during aestivation and winter dormancy.

This pioneering study examined the wound healing and regeneration abilities of the upside-down jellyfish Cassiopea at the Cnidarian Laboratory of the ICAR-Tuticorin Regional Station, Central Marine Fisheries Research Institute (CMFRI), India. A total of nine specimens (5.8 ± 0.4 cm) were studied, including six control medusae, one accidentally injured jellyfish (cut into four unequal fragments), and two amputated jellyfish (each divided into four equal fragments, totalling eight fragments). All specimens were maintained in a recirculatory aquarium system under optimal seawater conditions. Species identification of the control was confirmed through Basic Local Alingment Search Tool (BLAST) analysis of the 16S rRNA gene, showing 98.91% similarity with Cassiopea xamachana (Bigelow 1892), from the United States of America (USA) GenBank Accession No. ON545804.1, and validated through phylogenetic analysis. Microscopic and morphological observations revealed that the oral arm tissue lacked pulsing activity and could not regenerate its body structure. In contrast, fragments of umbrella tissue from both amputated and injured specimens exhibited pulsing and successfully regained symmetry within 7–15 days. The first phase of self-healing involved the reformation of umbrella symmetry, regeneration of bell tissue, and resumed functions similar to those of the normal medusa. The development of canal systems, including anastomosing vessels radiating from the centre, oral arms extending from the mouth, vesicles from the arms, and the central disc, was documented. The experimental observations revealed sequential wound healing through regeneration and morphogenesis in amputated and injured medusa. This study established Cassiopea as a promising cnidarian model organism for regeneration studies, highlighting its remarkable self-repairing and regenerative capabilities.

Sabellaria miryaensis is capable of growing massive reefs of several meters long in the subtidal area. However, no occurrence of S. miryaensis has been recorded in the Arabian Sea since its original description in 1990. This manuscript presents a new record of S. miryaensis in the Bay of Bengal, confirming its presence there. In addition, details on its ecology, including environmental parameters and the associated benthic biodiversity of S. miryaensis reefs are included. Four 1-m2 quadrat samples were collected from subtidal sabellariid reefs (∼15 m depth) off Gopalpur in March 2024, and associated macrofauna were preserved in 5% formalin for taxonomic analysis. Water parameters (temperature, salinity, and pH) and sediment texture were measured using standard field and laboratory protocols. The reef built by this species supports high macrofaunal and meiofaunal diversity, particularly polychaetes and other invertebrates. Morphological analysis confirms its identity with minor intraspecific variations. The reef also serves as a critical habitat for commercially important fish, underscoring its ecological and economic value. These findings highlight the need for further ecological assessments and conservation of sabellariid reef ecosystems in Indian coastal waters.

A redescription of Cloeosiphon aspergillus is presented based on the type material and additional specimens from Madagascar, South Africa, and New Caledonia. Cloeosiphon aspergillus is characterized by its pineapple-shaped anal shield, bidentate hooks arranged in rings, and a continuous longitudinal muscle layer. Additionally, a new species, Cloeosiphon mexicanus sp. nov. is described from the southern Mexican Pacific. This new species differs from C. aspergillus by having an inconspicuous secondary tooth on posterior hooks and the absence of spherical units along the basal margin of the anal shield. Furthermore, a discussion on the synonyms of C. aspergillus is included. This study expands the taxonomic knowledge of the genus Cloeosiphon and highlights the importance of the detailed description for accurate species recognition.

The full understanding of the parasite fauna of a host species requires sampling individuals across their entire distribution range. However, very few studies include an analysis considering such geographical coverage. The Ocellated killifish, Floridichthys polyommus, is an endemic estuarine fish whose distribution spans from the southwestern Gulf of Mexico to Belize. Here, we aimed at describing the metazoan parasite fauna of F. polyommus in localities across the Yucatán Peninsula to assess the parasite species richness at regional and local scales. From 2022 to 2024, 409 specimens of F. polyommus were collected from six localities. Data from three localities from a previous study were also included. Individuals were dissected, and examined for ecto and endoparasites. Twenty-four metazoan parasite taxa were identified using morphological characters and/or molecular data. Thirteen parasite taxa correspond to larval stages. Nine parasite taxa represent new host records, increasing to 35 the total number of metazoan parasites known for F. polyommus. The nematode Contracaecum sp. was found in all sampled localities, whereas the cestode Glossocercus caribaensis and the copepod Ergasilus sp. were found in seven, with variable prevalence and mean intensity of infection values. Two general patterns were uncovered irrespective of the geographical scale of the analyses (local or regional): (1) Digeneans were the most species-rich parasite group and (2) F. polyommus harboured more larval parasite taxa than adults. It seems that the parasite fauna of the Ocellated killifish in each sampling site represent a subsample of the total species richness at the regional level.

Algal beds are biodiversity hotspots in coastal ecosystems, forming complex food webs based on seaweeds. Epifauna serve as important indicators of algal productivity and environmental change, interacting closely with their host seaweeds. This study compared the composition of epifaunal assemblages associated with different seaweed species in the Noto Peninsula, Japan, to elucidate their characteristics. A survey of epifaunal communities on 13 seaweed species around Tsukumo Bay revealed significant differences in abundance and composition among species. Epifaunal abundance was particularly high in Sargassum siliquastrum and Sargassum patens. Differences in assemblage structures were observed among seaweed species and sampling sites. Fucales seaweeds harboured more diverse epifaunal communities compared with Laminariales species. Variations in epifaunal composition among taxa suggest that interactions with host seaweed species play a crucial role in shaping assemblage structure.

Invasive non-native species proceed through the Invasion Process upon introduction to a new location, with stages comprising establishment, growth, spread, and invasive impact. High fecundity, driven by fast growth, short lifespan, and a long reproduction period, can lead to high population densities, facilitating stage progression. The Asian date mussel (Arcuatula senhousia) is a marine intertidal–subtidal species, recently established in the UK. Given its potential to impact ecosystem services in Northern Europe, understanding the Invasion Process stage it has reached is imperative for assessing potential invasiveness and informing management. Therefore, population parameters of subtidal A. senhousia in the UK were evaluated from April 2021 to March 2022 to assess invasion stage. Specimens were collected (n = 1,029) via dredging and processed for condition index, gonadosomatic index, gonad index, length-frequency distribution, and electronic length-frequency analyses. While densities were low (<1 individuals per m2), maximum lifespan was high (23 months) and growth rate was high (1.8 mm per month), relative to other populations within the species’ global range. Results confirmed June to October spawning as previously reported in the UK and France but also evidenced secondary spawning (in November) for the first time in Northern Europe. Successful recruitment from primary and secondary spawning in 2020 was also apparent. Findings indicate A. senhousia has reached the Growth stage, and that further spread within the UK and Northern Europe is likely. Climate change will likely increase larval survivorship and individual and population fecundity, facilitating progression to invasive impact, potentially within the next decade.