The brittle star Ophiocoma scolopendrina, a dominant species in the polluted intertidal sediments of Qeshm Island in the Persian Gulf, faces chronic exposure to heavy metals such as cadmium (Cd), a persistent anthropogenic pollutant known for its toxicity to marine biota. This study provides the first histological evidence of Cd-induced delays in arm regeneration in O. scolopendrina, highlighting its vulnerability as a benthic echinoderm in contaminated ecosystems. Specimens were collected, acclimated, and subjected to arm amputation, with regenerative histology monitored at intervals (24 hours, 72 hours, 7 days, 14 days, 21 days, 35 days, and 42 days post-amputation) under control conditions and Cd exposure (50 µg/l CdCl2). Regeneration followed a typical epimorphic process, involving repair, early regenerative, intermediate regenerative, and advanced regenerative phases, characterized by epidermal migration, re-epithelialization, and formation of a regenerative bud with proliferative cellular accumulations. Cd exposure significantly delayed wound closure (from 24 hours in controls to 72 hours in treated samples), reduced arm length (12 vs. 17.65 mm at 42 days), and redirected resources towards podial development and coelomic expansion rather than axial regrowth. Histological anomalies included disorganized skeletal ossicles and fragile connective tissues, indicative of Cd’s interference with calcium-dependent biomineralization, as further demonstrated by supplementary video evidence of mechanical fragility in regenerated arms, suggesting potential long-term impairment in further regeneration or survival under stress. These findings underscore the ecotoxicological risks of Cd pollution to echinoderm regeneration and ecosystem functions in the Persian Gulf, offering baseline data for biomonitoring and conservation in heavy metal-impacted marine habitats.

Eve Caroline Southward (1930–2023) was a multi-talented scientist, motivated by her curiosity and love of nature. Since she was never paid as a scientist, Eve was an amateur, in the best sense of the word. She was highly proficient at transmission electron microscopy and made lasting contributions to polychaete taxonomy, morphology and ecology. Eve was internationally respected, especially for her studies on the Siboglinidae, mouthless and gutless tubeworms (formerly called Pogonophora) that are found worldwide in the deep-sea. She described how the siboglinids obtained nutrition from symbiotic, sulphur-oxidising bacteria and described similar symbiotic relationships in several bivalve species. Eve wrote over 140 scientific publications and described 56 new benthic species, 47 being mouthless and gutless ‘pogonophores’. Eve assisted her husband Alan Southward in starting broad-scale intertidal surveys around the British Isles and Northwest Europe. These surveys formed the foundation for the time-series, later continued by others, that allowed assessments of the influence of climatic fluctuations, using intertidal rocky shore biota as indicators. Eve contributed, with Alan, to what became a 50-year study describing the long-term effects on intertidal communities of the oil pollution and excessive dispersant use resulting from the Torrey Canyon oil spill in 1967. Eve also co-wrote the Linnaean Society Synopsis on Echinoderms of the British Isles and helped complete unpublished work by Alan Southward and others on barnacle taxonomy.

Since the taxonomic revision of the Ophidiasteridae by H.L. Clark (1921), in which 20 genera were recognized as valid, several new genera and species were included in this family, and the boundaries between some of them became largely arbitrary. This also applies to Narcissia Gray, 1840, whose morphology and taxonomy are still very poorly understood today. The main goals of this research were: review the taxonomy of the genus Narcissia, from morphological studies; redescribe N. trigonaria Sladen, 1889 s. str.; characterize N. canariensis (d'Orbigny, 1839) and N. gracilis A.H. Clark, 1916, the two valid species most similar to N. trigonaria; review the validity of N. ahearnae Pawson, 2007 and N. trigonaria var. helenae Mortensen, 1933; review the validity of N. gracilis malpeloensis Downey, 1975. Altogether 370 specimens were analysed. All morphological structures of taxonomic importance have been illustrated, and, for the first time, the internal characters of this group were studied, from electron microscopy and microtomography. A new diagnosis for the genus Narcissia was constructed. Narcissia trigonaria was redescribed from a large specimen, from the type locality (Bahia, Brazil). Narcissia ahearnae is considered a valid species, and N. canariensis and N. trigonaria distinct entities. Narcissia trigonaria var. helenae is placed in the synonymy of N. trigonaria, and N. gracilis malpeloensis into the synonymy of N. gracilis. The dataset obtained in this work is by far the most complete acquired for the genus Narcissia.

The present paper, dedicated to the legacy of local geologist–engineer Peter Jozef (Sjeuf) Felder, who died in 2009, confirms his view that bioclasts constitute a valuable tool in the correlation of outcrops and borehole cores across the type area of the Maastrichtian Stage in the vicinity of Maastricht. His approach of interpreting changes in bioclast contents as having been influenced by Milankovitch cyclicity has here been applied successfully to the entire sedimentary complex of Maastrichtian (latest Cretaceous) age in the study area. In the present approach, results are corroborated by index fossils, mainly dinoflagellate cysts but also calcareous nannofossils, which allow correlation with the Stevns-1 core reference section in eastern Denmark. With the exception of local remnants of Belemnella obtusa Zone age, the Maastrichtian Stage in its type area encompasses the last 4.6 Ma of the Cretaceous Period (i.e. the Belemnella sumensis/Acanthoscaphites tridens Zone up to the K/Pg boundary). P.J. Felder's bioclast analyses have enabled the detection of twelve 400 kyr eccentricity cycles of Milankovitch cyclicity in the area. However, the section is not continuous; there is a hiatus of c.700 kyr between the Gulpen and Maastricht formations at the ENCI-HeidelbergCement Group quarry. In addition, smaller hiatuses, usually in the range of several 20 kyr cycles, have been detected in the upper Maastricht Formation.

A new species of holothurian of the genus Psolus Oken, 1815 is described. Psolus rufus sp. nov. was found in the central Cantabrian slope (Bay of Biscay) at 1500 m depth. The new species is characterized by having: ovoid body, reddish colour in vivo; dorsal area enclosed in a complete test composed of imbricating scales; 10 triangular plates of the same size surrounding mouth; 10 oral tentacles; no dorsal papillae; tube feet in two rows in the ventrolateral radii but one single row in the medial third or the body; ossicles are big dorsal plates and small plates in the sole, which are smooth, irregular and perforated. The molecular study of the COI gene supports the morphological results, grouping P. rufus sp. nov. together with other members of the genus. However, the new species is genetically distinct from the two groups (Antarctic and Canadian) of the available sequenced Psolus species. Furthermore, a key to the Psolus species of the north-eastern Atlantic Ocean is provided.

The sea star Anasterias minuta broods the embryos in the oral region; embryos then block the mouth and prevent the parent from taking up nutrients during the brooding period. Here, we analysed content of carbohydrates in different organs as well as in eggs, embryos and juveniles of A. minuta. We found that these biochemical components are used mainly by the pyloric caeca and the body wall as reserve substances to endure the periods of reduced consumption rates of non-brooding females and males and the long-term starvation of brooding females. The ability to translocate carbohydrates from females to embryos and juveniles observed in other species of sea stars was not confirmed.

Although in vivo and in vitro approaches appear to be very different, they are related and complementary techniques and both are essential for the investigation of diverse biological topics. The employment of both techniques was considered particularly appropriate to investigate the role of 17β-oestradiol and testosterone in echinoid reproductive biology. The relationship between sex-steroids and echinoid reproduction has not been clearly determined yet, due to the highly variable and sometimes contrasting results obtained from steroid administration experiments. These might be due to the activation of protective metabolic mechanisms that can prevent the exogenous molecules from exerting their biological functions, as observed in our previous research. To clarify these aspects, in the present study we explored sex-steroid involvement in the reproduction of the sea urchin Paracentrotus lividus, employing both in vivo and in vitro approaches: (1) an experiment involving hormone dietary administration was performed and different reproductive parameters were deeply analysed; (2) ovarian cells were cultured in the presence of the same steroids and morphological and biochemical analyses were carried out. According to our results, sex-steroids appear not to be involved in sea urchin gonad development and gamete maturation, as neither in vivo administration nor in vitro exposure influenced gonad and gamete growth. In addition, in vitro hormonal treatment did not affect sea urchin Major Yolk Protein content. Overall, the present work complements our previous research providing information on sex-steroid involvement in echinoid reproduction and illustrates new methodological approaches that will be useful for future research on invertebrate biology and physiology.

The seastar Ophidiaster ophidianus is a vulnerable and protected species in the Mediterranean Sea but is common on North Atlantic islands such as the Azores and Madeira archipelagos. This work presents new insights into the phylogeography and genetic diversity of O. ophidianus from the Azores, based on 67 sequences of the 16S mitochondrial gene and 46 sequences of the nuclear ATP intron 5 gene. Twenty-six samples from the Mediterranean and seven samples from Madeira were used as out-groups. The results revealed that there is a lack of genetic differentiation between O. ophidianus from the Azores and the out-groups. All, therefore, belong to the same lineage and argue for a fast and recent range expansion of this species into the Azores. Our results also suggest the existence of distinctive periods of strong gene flow followed by periods of either low or non-existent gene flow between the Mediterranean Sea and this archipelago, which could explain the presence of private haplotypes in all studied areas.

The warm water Ophidiaster ophidianus has a protected status in the Mediterranean Sea and also occurs in the shallow subtidal of the Azorean Archipelago. From April 2007 to August 2009, the population structure and seasonal abundance of O. ophidianus was studied at different depths within a marine conservation area offshore from São Miguel (SAC: PTMIG0020, Natura 2000). Ophidiaster ophidianus showed a marked seasonal trend in abundance, with higher numbers being recorded from 5 m depth during spring and autumn, and higher numbers at 10 m depth in summer and winter. Densities ranged from 9 to 16 individuals per 100 m2 over the sampling period. The size–frequency distribution of O. ophidianus was uni-modal for each sampling month. Small individuals dominated at 5 m depth, intermediate-sized individuals at 10 m and larger individuals were more frequent at 15 m. The present study establishes population parameters for O. ophidianus and provides the necessary information for management purposes at the north-western periphery of its range in the Azores.

This study assessed the Zanzibar sea cucumber fishery using a multidisciplinary approach.Data was collected by (i) interviewing various groups of actors in the fishery andreviewing management documentation and legislation, (ii) by monitoring catches and (iii)through a visual census of coastal sea cucumber populations in areas open and closed tofishing. The fishery showed clear signs of being unsustainable with high fishing effort,and weak formal and informal management institutions. The fishery operation wascharacterised by an intricate cross-scale structure with both fishers and sea cucumberproducts being transported across national borders. The visual census of commercial seacucumber stocks at three sites open to fishing around Zanzibar showed low densities acrossthe range of sea cucumber value groups including low value species. Furthermore, thediversity of commercial sea cucumber species was lower in fished reefs than on a protectedreef. The poor status of the sea cucumber populations was confirmed by the perception ofan overfished resource by the interviewed actors active in the fishery. This was alsodepicted by the paucity of high value species, and high representation of low value andnewly commercialised species in fishers catch. We conclude that the current state ofZanzibar’s sea cucumber populations is compromising the fisheries self-replenishment andexistence and that the fishery is in urgent need of a complete management reform.

This study presents the first extensive investigation of echinoderm distribution in the area of mobile bottoms in the open part of the northern and middle Adriatic Sea. Five hundred and eighteen bottom trawl hauls were performed at 56 predetermined permanent stations along ten transects over different sediment types, at depths of 10 to 430 m. A total of 34 species of Echinodermata were identified (9 from the class Holothuroidea, 12 from the class Asteroidea, 4 from the class Ophiuroidea and 9 from the class Echinoidea). The list of the species, together with data on depth and sediment distribution, and the stations where individual species were found, are presented.

Two new species of Ordovician echinoderms are described: Pleurocystites mitratus from the Kiln Mudstones (Caradoc) at Craighead, and Homocystites beggi from the Starfish Bed (Ashgill) of Threave Glen. Description of the former necessitated a review of the composition and status of the family Pleurocystitidae. The genus Dipleurocystis Jaekel 1918 and the subgenera Pleurocystites s.s. and Pleurocystella Paul, 1967 are rejected. The number and type of pectinirhombs; size of the periproct, composition of its border and nature of its covering plates (periproctals), and the ornament of the thecal plates and proximal columnals, are the most useful taxonomic criteria within the Pleurocystitidae. Pleurocystites mitratus is characterized by three conjunct pectinirhombs, a symmetrical theca without a rectal lobe and small periproctals each with a central pit. Homocystites beggi is distinguished from the closely related H. constrictus by strong granular ornament on the thecal plates.

Other echinoderm remains include plates of a cheirocrinid cystoid from the Kiln Mudstones.