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.