In many species with encapsulated larval development, the larvae play an active role in hatching. However, the factors that control when the larvae hatch from each egg-capsule within an egg-mass are largely unknown. Advanced egg-masses of the gastropod Crepipatella peruviana were used to determine the hatching time of capsules from each egg-mass. After each female was detached, the egg-mass was also removed from the substrate and all capsules were then counted and measured. All capsules were examined to determine the time of hatching and the order in which capsules hatched from each egg-mass. Larvae were collected from each hatched egg-capsule and the number, size and weight of larvae from each capsule were determined. After 50–60% of the capsules from each egg-mass had hatched, the same characteristics of the remaining unhatched larvae from sister capsules were documented. Larvae were found to have hatched when they reached a size of 354 ± 22 μm (n = 245). Larvae from capsules within the same egg-mass hatched over a period of up to 12-days. The order of hatching in capsules from the same egg-mass was determined by larval content: capsules with fewer larvae and smaller capsules with heavier larvae hatched first. The hatching from one capsule in any given egg-mass did not induce the hatching of its sister capsules. Furthermore, hatching also occurred successfully in the mother absence, suggesting that this process is largely or completely controlled by the encapsulated larvae, although a possible maternal role in synchronizing hatching cannot be excluded.

Ionella fimbriata sp. nov. is described from a pair of bopyrid isopods attached to a male specimen of the ghost shrimp Neocallichirus grandimana collected in Veracruz, Mexico. This is the fifth species belonging to Ionella but the first one recorded from the Atlantic Ocean, which represents an important extension of its distribution range because until now all Ionella species were known from the Pacific Ocean. Females of I. fimbriata sp. nov. can be differentiated from the others of the genus by a barbula with one stout, acute, falcate projection on each side and medial margin with triangular rounded projections; seven pairs of pereopods with elongate cuticular extensions on bases and ischia, and five pairs of tuberculated biramous pleopods of pinnate shape. Males can be recognized by five pairs of globose biramous pleopods, in which endopods are longer than exopods, and uropods longer than pleopods. Description and illustrations of both the female and male I. fimbriata sp. nov. are provided, as well as keys for both sexes of all species in the genus. The fecundity, embryo size and volume of I. fimbriata sp. nov. are reported.

In this study, a single specimen of Pacific black scabbardfish Aphanopus arigato Parin, 1994 was collected at a depth of ~500 m near Dongsha Island in southwestern Taiwan (18°49′ to 20°45′N and 112°46′ to 116°15′E), on 14 March 2023. This is the southernmost record of A. arigato, with a significantly wide range extension from northern Japan, and southern Kuril Islands to the South China Sea. We also provide comparisons of the morphological measurements, first description of sagittae otoliths, and a partial sequence of the cytochrome oxidase subunit I gene for the specimen studied in this study.

We report on four brachyuran crabs collected from the carapaces of loggerhead sea turtles Caretta caretta nesting on Yakushima Island in Kagoshima prefecture, Japan. Three of these crab species have not been previously reported as epibionts on sea turtles. Our research suggests that physical damage to a turtle's carapace, such as cracks and holes created by other epibionts like the burrowing barnacle Tubicinella cheloniae, can create unique habitats for these opportunistic crabs.

This study investigates the reproductive biology of Holothuria arguinensis over one year (December 2016 to December 2017) from two locations on the Atlantic coast of Morocco: Skhirat (North Atlantic) and Souiria K'dima (Central Atlantic), including the sex ratio, size at sexual maturity, and reproductive cycle. Monthly sampling was carried out, along with the collection of environmental and biometric data at each site. The sex ratio did not differ significantly from 1:1 at either study site. The gonadosomatic index (GSI) reached its peak during spring (April and May) for both sexes, and the spawning period was observed from summer to autumn (June–October) at both locations, suggest annual spawning. GSI was correlated with increasing or high chlorophyll-a concentrations, salinity, and spawning with rainfall periods. The estimated size at sexual maturity was 15.9 cm body length, 189.1 g total body weight, and 92.5 g gutted body weight. The minimum mean oocyte diameter was recorded during the recovery stage (31 ± 11 μm (mean ± SD) at Skhirat and 34 ± 23 μm (mean ± SD) at Souiria K'dima), while the highest values were observed in the partial spawning stage (112 ± 27 μm (mean ± SD) at Skhirat and 104 ± 19 μm (mean ± SD) at Souiria K'dima). This study highlights the need for further research to expand our knowledge of the biological and ecological characteristics of H. arguinensis populations, to facilitate the cultivation of juveniles in captivity, and to develop fishing regulations based on scientific findings. As a fishery management strategy, we suggest a closed season from April to October to protect the reproductive period of H. arguinensis on the Moroccan coast.

The amphipod Ampithoe bizseli Özaydinli and Coleman, 2012 is a cryptogenic species that was recently described in Turkey. Although to date it has only been recorded in the Mediterranean Basin, it is potentially native to the Red Sea and Indian Ocean. During a macrozoobenthos sampling campaign carried out in the Canary Islands in 2023, 25 individuals of A. bizseli were found in association with some fish farm facilities. This work represents the first report of this amphipod in European Atlantic waters and increases knowledge of the ecology of this non-indigenous species.

Cheilopogon arcticeps (Günther, 1866) is recorded for the first time from the Indian coastal waters. Two specimens of C. arcticeps (158–167 mm SL) were collected from the Petuaghat fishing harbour of Purba Medinipur, West Bengal, India. The present paper reports the species for the first time from Indian waters and thus, the distributional range of the species is extended from Western Pacific Ocean to the Bay of Bengal, Indian Ocean. This paper provides more detailed information on the taxonomy and morphometric of the poorly known species.

A new species of polychaete annelid, Armandia ramanamurthyi n. sp., is described from the sandy sediments off Tamil Nadu coast, Bay of Bengal, northern Indian Ocean. The major feature distinguishing A. ramanamurthyi n. sp. from other species of the genus is bearing a non-papillated anal tube and the presence of a bulbous, orbicular papilla ventrally placed at the proximal end of the anal tube. The orbicular papilla bears black pigmentation and posteriorly ends in an oblique cirrus. Additionally, Ophelina arabica Parapar, Al-Kandari, Barroso & Moreira, 2023 described from Kuwait waters is recorded for the first time in Indian waters since its original description.

The diogenid hermit crab, Calcinus morgani Rahayu & Forest, 1999, is reported from the Andaman Islands in the eastern Indian Ocean. It was previously recorded as Calcinus gaimardii (H. Milne Edwards, 1848) from the Nicobar Islands, south of the Andaman Islands, in 1865 about 160 years ago, but there were no additional records of the species in the Andaman and Nicobar Islands. The diagnosis of C. morgani is provided on the basis of the present specimens for helping the identification. A key to species of the genus Calcinus known from the Andaman and Nicobar Islands is also provided.

This work focuses on the study of three pelagic fish species of the same genus, caught from the south-western coasts of the Mediterranean. It concerns lipid content, fatty acid profile and nutritional quality (atherogenic index, thrombogenicity index, ratio between hypocholesterolemic and hypercholesterolemic fatty acids and n6-to-n3 ratio) of Trachurus trachurus, Trachurus mediterraneus and Trachurus picturatus. Lipid extraction and esterification were carried out on the flesh of each species, and fatty acid methyl esters were analysed using gas chromatography-mass spectrometry. The obtained results show that lipid content mean values vary between 2.87 and 5.06%, saturated fatty acids contents range from 37.51 to 53.23%, monounsaturated fatty acids content range from 29.24 to 37.65% and polyunsaturated fatty acids content range from 9.11 to 33.24% according to species. Also, the different mean values of indexes describing the nutritional quality vary significantly depending on species. That confirms the good quality of studied species and their importance for human nutrition and health, hence the urgent need to preserve their stocks.

Identifying cryptic species and juveniles in the Ophiuroidea has always been a challenge. However, post-larval developmental studies have the potential to uncover the identity of these cryptic species and juveniles, as they offer valuable information that is not often found in adults. Although the importance of studying growth series is well-known in ophiuroids, it is difficult to obtain and identify the juvenile stages. For this reason, most studies are restricted to brooding species and information is lacking for many species, including those of the genus Ophiocoma. In this study, a growth series was developed to show the main differences during the development of two similar species of Ophiocoma: Ophiocoma echinata and Ophiocoma trindadensis. Using morphometry and scanning electron microscopy, we describe in detail the juveniles, intermediate stage, and adults of O. echinata and O. trindadensis. Differences in the shape of the ventral arm plate and dorsalmost arm spines, the number of tentacle scales, and the presence of granules ventrally were highlighted in the separation and identification of juveniles of both species.

The present study described and illustrated the larval morphology of the three first zoeal stages (zoea I–III) of Synalpheus fritzmuelleri and compared with the previous described larvae of this species. The results pointed out a variety of differences among the descriptions, most of them related to the type and number of setae and articulation of appendages. The first zoea demonstrates similarities shared with the zoea I within the genus besides the diagnostic described characteristics. Other incongruences were also found such as the lack of information about some structures, such as the maxillule in the zoea I, and the use of ambiguous terms do designate type of setae. Moreover, the more advanced the zoea, additional differences were found among the previous and the current descriptions. Due to that, the necessity to review and also add new descriptions for Synalpheus larvae proves imminent to establish a standardization in the morphological description that will strengthen the comparative relationship in the genus.

The Japanese flying squid, Todarodes pacificus, is distributed mainly in the northwest Pacific and the Japan Sea. The present study was conducted for a better understanding of the mechanisms behind its migration routes. The ratios of strontium to calcium (Sr:Ca) in the statoliths can be associated with the water temperatures the squid experienced in the sea. Using specimens collected in the northern Japan Sea in summer and Lagrangian backward tracer experiments, a strong negative correlation was obtained between the Sr:Ca in the statoliths and the empirical water temperatures estimated through a regional ocean model. These backward tracer experiments were continuously conducted at depths of 6, 15, and 30 m. The greatest determination coefficient of the regression expression appeared for a nearshore tracer group of the experiment at a depth of 15 m. In addition, the regression expression provided reasonable lifetime empirical water temperature variations of the squids collected in the sea areas east of Tsushima Island and west of the Goto Islands in winter. The combination of Ca:Sr analytical chemistry and tracer experiments with the ocean dynamic model used in this study improved our understanding of the migration path of T. pacificus.

Members of the genus Actinia are familiar members of rocky shore communities across much of the world. However, to date, no Actinia species have been reported from the North American continent. Here, we report Actinia from an approximately 22 km length of the New Jersey, US shoreline, where it was first discovered in 2021. Morphology and DNA barcoding data (mitochondrial cytochrome c oxidase I and nuclear internal transcribed spacer) indicate that these populations are Actinia equina. The presence of these populations close to major ports in New Jersey, New York, and Philadelphia suggests a probable introduction from shipping activities.

This study on distribution of Ophiothrix savignyi was carried out from 2017 to 2022 in the Iranian waters of the Persian Gulf. Nineteen locations were sampled from coastal waters, including 16 newly reported areas. O. savignyi was epizoic, associated mostly with sponges, sea urchins, and soft corals. This survey shows O. savignyi as the most common and widespread brittle star in the northern and eastern Persian Gulf. In this study, O. savignyi, has been described again from the Persian Gulf.

The fortune jack (Seriola peruana), a pelagic fish typically found along the Tropical Eastern Pacific, has been recorded in the northernmost Gulf of California (GC) region. The first record in the Upper Gulf and habitat expansion of S. peruana is reported based on the meristic, morphometric, and biological data of three specimens caught by local artisanal fishermen in April 2024. The lack of commercial value likely explains the region's absence of records for this species. The increased presence of S. peruana distribution in the Upper GC could have significant ecological implications, which warrants further fish habitat use and climate change research.

Understanding the population structure and genetic diversity of green turtles is crucial for effective conservation. This study investigated the occurrence, genetic composition, and potential origins of green turtles (Chelonia mydas) in the Potiguar Basin, northeastern Brazil, based on stranding data from 2010 to 2019. Analysis revealed that 87.36% of the population consisted of juveniles, primarily females with a curved carapace length (CCL) between 30 and 59.9 cm. Genetic analysis of the mtDNA control region (481 bp, n = 39) revealed eight haplotypes, with CM-A8 (48.7%) and CM-A5 (30.8%) being the most common. This may be related to the geographic position of the Potiguar Basin, located in the ‘corner’ of the South American continent. High haplotype diversity and low nucleotide diversity were observed, consistent with other Brazilian foraging grounds. Mixed stock analysis identified Ascension Island as the primary source population, followed by Guinea-Bissau and Surinam. The results highlight the importance of the Potiguar Basin as a foraging area for green turtles and emphasize the need for comprehensive conservation strategies to protect this vulnerable population.

The magnificent shrimp, Ancylomenes magnificus (Bruce, 1979), is a sea anemone associated marine ornamental organism exploited from Indo-Pacific waters, for the marine aquarium trade, as it has attractive coloration. However, there are no reports available yet on its population and reproductive characteristics (population structure, length–weight relationship, fecundity, sexual dimorphism, sex ratio and maturity stages). The present investigation provides information for the first time on the population and reproductive parameters of A. magnificus. In this study, a total of 158 individuals were collected from the intertidal regions of the Gulf of Mannar, Tamil Nadu, India from August 2021 to April 2022, out of which 61.4% (97 individuals) were females and 38.6% (61 individuals) were males. The estimated mean size (CL ± SD) of females was 4.93 ± 0.78 mm, while that of males was 3.22 ± 0.56 mm. The estimated mean body weight was 0.091 and 0.219 g in males and females, respectively. The study indicated strong sexual dimorphism in this species and considerable variation appeared in the carpus and chela of the second major pereopod, carapace and total length. The carapace length and weight showed a negative allometric relationship with a significant coefficient. Fecundity was relatively lower and embryo volume increased with size groups. Interestingly, the study revealed year-round breeding activity with a peak in the post-monsoon (January to March) and monsoonal period (October to December) for this species. The present investigation provides the first baseline information on the population and reproductive parameters of A. magnificus.

In the present study we update the distributional, bathymetric ranges and taxonomic characters of the carnivorous sponge Asbestopluma (Asbestopluma) magnifica Lopez, Bravo & Hajdu, 2011 providing new records for Argentinian jurisdictional waters in the SW Atlantic Ocean, including the Marine Protected Area Namuncurá/Burdwood Bank. The shallowest bathymetric range is now changed to the upper bathyal (289 m depth). We also amend the original description after re-examination of type materials, when markedly different micrometric values were observed for their subtylostyles and acanthotylostrongyles. We noticed a remarkable similarity between Asbestopluma (Asbestopluma) sarsensis Goodwin, Berman, Downey & Hendry, 2017 and A. (A.) magnifica and we suspect they may be synonymous, but we refrain from taking a formal decision pending revision of all materials reported for the younger taxon or a genetic analysis.