Drought stress was evaluated with polyethylene glycol 6000 (PEG 6000) treatment in Dunaliella salina, a microalga known for its great ability to withstand salinities of more than 30%. The aim was to explore the acclimation mechanisms used by the microalga to regulate its growth and physiology during coping with drought stress. The microalga was subjected to culture mediums containing 2 and 5% PEG for 25 days and was compared with a control culture medium. Significant decrease in growth parameters such as specific growth rate, biomass and number of divisions per day was demonstrated in PEG-treated algae. During PEG treatment, chlorophylls slightly increased, while β-carotene and total protein were not affected. Osmolytes, as well as carbohydrates, were found to be significantly higher in PEG-treated algae than in control. Increased catalase and ascorbate peroxidase activities were proportionally related to PEG concentrations in the cultures. The PEG-treated cells accumulated a considerable amount of hydrogen peroxide and malondialdehyde, especially at higher PEG concentrations. Electrolyte leakage increased, regardless of the PEG concentrations applied, while DNA fragmentation was not observed after 25 days of treating with PEG. It was concluded that Dunaliella cells could respond to the drought stress, probably by using a higher accumulation of a range of osmolytes and also more stimulation of the antioxidant enzymatic system.

The catostylid jellyfish, Crambionella annandalei was originally described by Rao (1932) based on a preserved specimen collected from the Andaman Sea. Since then, no detailed taxonomic studies have been conducted and the species is often misidentified. Here, we provide a detailed morphological re-description of C. annandalei from fresh material collected at a variety of locations along the east coast of India. The species can be distinguished from its congeners by a combination of morphological characters, the most important of which are the proportion of terminal club length to oral arm length (0.48 ± 0.031), the proportion of the distal portion of the oral arm to naked proximal portion (7.25 ± 0.268) and the body colour. The occurrence of intra-specific colour variation in fresh specimens was also observed in the present study.

The present study investigated the effects of a fish weir, a fixed trap used by artisanal fisheries, on the intertidal macrobenthic infauna of a macrotidal sandy beach on the Amazon coast. Biological and sediment samples were collected from within the weir and at five points of increasing distance (10 cm, 50 cm, 1 m, 2 m, 5 m and 50 m) from the external portion of the trap. The sediments from the weir and at 10 cm were dominated by mud, with a gradual decline in fine grains, water content and organic matter with increasing distance from the weir to 50 m (control). Taxon abundance and richness were significantly higher in the weir and at 10 cm than at the other sampling points. There was a trend of decreasing density and richness of the infauna from the weir to 1 m (which was a point of transition between the muddy and sandy sediments), after which the biological descriptors tended to increase once again. A shift was also observed in the dominant trophic groups, with a decrease in the abundance of the deposit feeders with increasing distance from the weir. By contrast, predators were more abundant at the points further from the weir. Our results indicate that fish weirs alter the associated sedimentary habitats, due to the increased protection from the action of waves and currents, with a micro-scale (from a few centimetres to 1–2 m) influence on the local macrofauna.

This study presents two years of characterization of a warm temperate rhodolith bed in order to analyse how certain environmental changes influence the community ecology. The biomass of rhodoliths and associated species were analysed during this period and in situ experiments were conducted to evaluate the primary production, calcification and respiration of the dominant species of rhodoliths and epiphytes. The highest total biomass of rhodoliths occurred during austral winter. Lithothamnion crispatum was the most abundant rhodolith species in austral summer. Epiphytic macroalgae occurred only in January 2015, with Padina gymnospora being the most abundant. Considering associated fauna, the biomass of Mollusca increased from February 2015 to February 2016. Population densities of key reef fish species inside and around the rhodolith beds showed significant variations in time. The densities of grouper (carnivores/piscivores) increased in time, especially from 2015 to 2016. On the other hand, grunts (macroinvertebrate feeders) had a modest decrease over time (from 2014 to 2016). Other parameters such as primary production and calcification of L. crispatum were higher under enhanced irradiance, yet decreased in the presence of P. gymnospora. Community structure and physiological responses can be explained by the interaction of abiotic and biotic factors, which are driven by environmental changes over time. Biomass changes can indicate that herbivores play a role in limiting the growth of epiphytes, and this is beneficial to the rhodoliths because it decreases competition for environmental resources with fleshy algae.

Marine hydroids, the polyp stage of hydrozoans, are assumed to be carnivores and play an important role in benthic-pelagic coupling processes by regulating zooplankton populations and transferring energy. The known hydroid diets mainly consist of zooplankton as well as some benthic diatoms and metazoans, almost all of which have smaller dimensions than the polyp. In the present study, a large-scale breeding failure of the early juveniles of the ivory shell Babylonia areolata (Mollusca: Gastropoda: Babyloniidae) was found in a local aquaculture farm in Fujian, China in July 2018. About 640,000 out of 800,000 early juveniles (80%) died due to predation by a millimetre-sized colonial hydroid species that was initially overlooked. The hydrozoan species was identified as Eirene sp. (Cnidaria: Hydrozoa: Eirenidae) via the integration of morphological and molecular data. A laboratory feeding experiment showed that the hydroid predation led to an overall mortality of ivory shell juveniles of up to 92.6% after 48 h. The predation process was observed in the laboratory and a video showing the entire process was prepared. This is the first report of hydroids preying on gastropod juveniles, revealing a previously unknown threat to mollusc aquaculture including ivory shells. Several management practices are suggested to mitigate this newly recognized threat.

The family Syllidae, aside from representing the most species-rich family in Annelida, is characterized by a number of sexual and asexual reproductive strategies. With the exception of a few viviparous species, the subfamily Syllinae is characterized by schizogamous reproduction with pelagic larval stages and without parental care. Laboratory rearing of ripe specimens of Syllis rosea showed a different reproductive strategy, hitherto unknown in this subfamily. While male stolons rapidly degenerated after fertilization, female ones released large eggs in a gelatinous cluster attached to the middle-posterior chaetigers. The gel mass progressively compacted as a cocoon wrapped by the stolon body; 7 days after the deposition the larvae hatched out from the cocoon at the metatrochophore stage and the female stolon died after a few days. After hatching the larvae remained associated to the stolon, and young specimens of S. rosea survived up to the 3-chaetiger stage. Until now cocoon brooding by the stolon has only been reported for some Autolytinae. The production of gelatinous egg masses and parental care are known in basally branching clades within Syllidae, suggesting that this reproduction mode might retain some ancestral features. The scarce knowledge about reproductive cycles in Syllinae does not allow clarification whether this strategy is unique for S. rosea, or it occurs in other congeneric species. Further research is needed to understand possible relationships between sexual reproduction and phylogeny, stolon morphology and its adaptation to parental care, and ultimately between reproductive strategies and ecology.

In Thailand, two species of rhizostome jellyfish, Rhopilema hispidum and Lobonemoides robustus, are commercially harvested. The cnidomes, nematocyst size and toxicities were compared between these species. Rhopilema hispidum and L. robustus each had four types of nematocysts on their oral arms. For R. hispidum, these nematocyst types included two types of isorhiza and two types of rhopaloid, while in L. robustus, there were three types of isorhiza and one type of rhopaloid. For R. hispidum, tubule lengths of the largest nematocyst type (large round isorhiza; mean ± SD = 313.8 ± 62.2 μm) were significantly longer than those of L. robustus (large ellipsoid rhopaloid; 162.1 ± 38.5 μm). Using the freshwater shrimp, Palaemon paucidens, in a bioassay, we determined that the lethal nematocyst concentrations for R. hispidum and L. robustus were 5705.3 ± 1118.1 and 3408.3 ± 1032.9 unit g−1 wet weight, respectively, and that these concentrations were significantly higher in the former than in the latter.

Coral reefs have experienced extensive degradation across the world over the last 50 years as a result of a variety of stressors operating at a range of spatial and temporal scales. In order to assess whether declines are continuing, or if reefs are recovering, detailed baseline information is required from across wide spatial scales. Unfortunately, for some regions this information is not readily available, making future reef trajectories difficult to determine. Here we characterized the current benthic community state for coral reefs in the Wakatobi region of Indonesia, one of the most biodiverse marine regions in the world. We surveyed 10 reef sites (5, 10 and 15 m depth) to explore spatial variation in coral reef benthic communities and provide a detailed baseline. Previous data (2002–2011) were available for coral, sponges, algae and soft coral at six of our study sites. Using this information, we determined if any changes had occurred in dominance of these benthic groups. We found that benthic assemblage composition differed significantly over relatively small spatial scales (2–10 km) and hard coral cover was highly variable, ranging from 7–48% (average 19.5% ± 1.5 SE). While coral cover appears to have declined at all sites where data were available since 2002, we found little evidence for widespread increases in other benthic groups or regime shifts. Our study provides a comprehensive baseline dataset for the region that can be used in the future to determine rates of change in benthic communities.

A thermo-tolerant diatom species has been isolated from Tunisian hot spring water (40°C). The isolated diatom has been molecularly identified and classified into the genus Halamphora. The growth kinetics, lipid content and distribution of fatty acids were assessed at 20 and 30°C temperature levels and constant irradiance in controlled batch cultures (11 days). Halamphora sp. showed better growth (μ = 0.53 day−1) and a higher lipid yield (25% of the dry weight) at a higher temperature (30°C). Under the two temperatures tested, the highest lipid and fatty acid contents were mainly reached during the stationary growth phase. The fatty acid profile showed a significant content of two essential fatty acids, eicosapentaenoic acid (EPA, 20:5n-3) and arachidonic acid (AA, 20:4n-6), reaching ~15% and ~21% of the total fatty acids, respectively, at 20°C and 30°C. The distribution of the different components of the fatty acids showed that EPA and AA were mainly located in the neutral lipid fraction in the stationary phase.

We report on the relationships between some conspicuous Mediterranean photophilous sponge species and Caulerpa cylindracea, a non-indigenous species. A diversification of defence strategies and behaviour is highlighted in target species belonging to different orders of Demospongiae from a western Mediterranean Marine Protected Area (NW Sardinian Sea). Caulerpa cylindracea displays a strongly invasive behaviour during body colonization of the Irciniidae Sarcotragus spinosulus and Ircinia retidermata (order Dictyoceratida). These sponges possess pre-adaptive defensive morpho-functional and physiological traits enabling them to partly withstand algal invasion. Also Aplysina aerophoba (order Verongiida) seems to be able to control colonization. Successful anti-Caulerpa strategies characterize the rarely affected Crambe crambe (order Poecilosclerida). Species-specific competitive strategies are displayed at different levels of body architecture, behaviour and physiology by native sponge species. The invasion patterns on sponges, the invasion dynamics in 2016–2017 and topographic distribution of C. cylindracea on S. spinosulus confirm this algal species as a threat, with potential long-term effects on sponge assemblages. Data suggest other kinds of poorly investigated synergic stressors affecting these habitat-forming species. Defence strategies of sponge species take the form of: (1) passive deterrence by morpho-functional pre-adaptive traits as growth form, biomass amount, surface traits, and microhabitat within the sponges' aquiferous system; (2) active physiological defence, whereby the morphology/anatomy of the sponge body is adapted to control invaders, by body remodelling and regenerative processes within the aquiferous system and at the sponge surface; (3) presumed active chemical defence by exudation processes of bioactive compounds.

Calcareous green alga in the genus Halimeda are important contributors to the marine carbonate budget. Dongsha Island is located in the northernmost South China Sea and is a seagrass-dominated ecosystem with intermixed Halimeda macroloba patches, making it an excellent system to better examine the extent of carbonate contribution by H. macroloba in such an ecosystem. To this end, we examined the standing stock and actual CaCO3 contribution of H. macroloba in the seagrass-dominated ecosystem (herein Dongsha Island) and compared them with those in Halimeda-dominated ecosystems. The density, growth rate, calcification rate and CaCO3 content of H. macroloba at four life stages were investigated. The mean density of H. macroloba was around 8.82 ± 1.57 thalli m−2 and the estimated standing stock was 61,740 to 72,730 thalli. Thalli produced 1 to 2 new segments day−1, giving a growth rate of 0.003 ± 0.001 g dry weight thallus−1 day−1. Calculated algal biomass and annual areal production were 0.03 g m−2 and 9.66 g m−2 year−1. In each square metre of this area, H. macroloba produced 8.82 to 17.64 new segments day−1, accumulating 0.002 ± 0.001 g CaCO3 thallus−1 day−1 or around 6.44 g CaCO3 m−2 year−1. Mean CaCO3 content was 0.32 ± 0.05 g thallus−1. As expected, the growth rate and CaCO3 production of H. macroloba in Dongsha Island were lower than in other studies from Halimeda tropical ecosystems. Overall, this work provides the baseline of carbonate production of H. macroloba in Dongsha Island and relevant systems where the ecosystem is dominated by seagrasses.

Changes in phytoplankton composition of the Golden Horn Estuary were investigated following remediation, through seawater transfer from the Strait of Istanbul to the estuary. Average values of Secchi depth, salinity and dissolved oxygen increased during this study when compared with a previous study. The average number of species (S) and species diversity (H′) increased and they correlated positively with Secchi depth, salinity and dissolved oxygen. There was a similar phytoplankton group composition between this and a previous study, however, the species composition differed. A total of 127 taxa consisting of diatoms (66 taxa), dinoflagellates (49 taxa) and others (12 taxa) were identified. Abundance of dinoflagellates and phytoflagellates and their relative contribution to the total phytoplankton abundance increased during this study, however, the abundance of diatoms and their relative contribution decreased notably, as compared with the previous study. There was a significant positive correlation between salinity and dinoflagellates and phytoflagellates (P < 0.01), and also between Secchi depth and dinoflagellates (P < 0.01) in the upper estuary. Additionally, salinity and Secchi depth correlated positively with species diversity (H′) and number of species (S) (P < 0.01). The increase in water transparency probably contributed to the increase in abundance of dinoflagellates and phytoflagellates. The results revealed that water transparency was one of the most important factors affecting phytoplankton composition in the study area. Changes in some environmental conditions following seawater transfer appear to have changed phytoplankton composition. As a result, phytoplankton species were confirmed as a very good indicator of changed environmental conditions.

Moonshine worms are a popular bait species used for fishing. The taxon was not detected during surveys of the macrobenthos conducted in Knysna in the 1940s and 1990s, and was first reported as a harvested bait species in the mid-2000s, suggesting that it appeared for the first time in the estuary in the last three decades. A previous molecular analysis identified the worms as Diopatra aciculata, a species first described from Australia. This study provides an updated detailed morphological description of D. aciculata in South Africa to facilitate future identifications and also investigates the species' distribution and population size in the Knysna Estuary. Specimens were examined by scanning electron, stereo- and compound microscopes. Diopatra aciculata has tubes that protrude from the sediment in sandy areas, often decorated with algae and shell fragments; a large body size, up to 600 mm long and 11.5 mm wide. It has 10–18 rings on ceratophores; 5–10 teeth on pectinate chaetae; uni- and bidentate pseudo-compound falcigers and dorsal cirri approximately as long as branchiae. Diopatra aciculata was detected up to 12 km from the mouth of the Knysna Estuary with densities measured at 18 sampled sites. Statistical analysis retrieved high and low density groups that were significantly different from one another (Kruskal-Wallis H(14, 800) = 376.55; P = 0.01), but distribution of high density sites was patchy. We estimate that the population comprises 20–24 million individuals. Given the size of individual worms and the population estimate, this species can be expected to have significant ecological impacts in the estuary.

Ostracods and foraminifera are excellent indicators of environmental change and can act as proxies for the presence of seagrass meadows. These proxies have been under-utilized in vulnerable coastal ecosystems in South-east Asia, and the fundamental habitat and environmental parameters required for such application in environmental monitoring have not yet been established. We investigated the habitat preferences of ostracods and foraminiferal species in seagrass and non-seagrass habitats within Sungai Pulai Estuary (Johor, Malaysia), a system currently undergoing major coastal changes. Samples consisted of surficial and downcore sediments collected from two seagrass meadows and a non-seagrass habitat. Multivariate analysis determined the variations in spatial and depth distribution of the meiofauna. Species dominance, abundance and distribution varied between sites, whereas diversity and community structure varied with sediment depth. We found fewer ostracod individuals (N = 1133) than foraminifera (N = 7242). Ostracods were more species-diverse (H′ = 3.34) in the non-vegetated area compared with seagrass areas (H′ = 2.74), whereas foraminifera species were most diverse (H′ = 3.60) in seagrass areas. Opportunistic species, such as Loxoconcha lilljeborgii, Asterorotalia pulchella, Murrayinella globosa, Ammonia tepida and Elphidium neosimplex dominated the meiofaunal assemblages. The presence of Nummulitidae and Paracyprididae in downcore samples provided information related to rare species and families. Salinity, organic matter and percentage of sand explained much of the meiofaunal distribution. Our findings provide new insight into the factors influencing the presence and distribution of ostracods and foraminifera in the estuary, comprising baseline information for understanding the vulnerability of such habitats to anthropogenic changes.

We present the description of a new species of genus Timea and the re-description of T. hechteli from cryptic habitats in the Gulf of Mexico. Timea alcoladoi sp. nov. is an encrusting, pale orange sponge, with megascleres ranging from styles to subtylostyles (185–990 μm long) and a single category of microscleres, spherostrongilaster characterized by a prominent rounded centre (5–15 μm in diameter). Timea hechteli was established by Lehnert & Heimler, based on the description of a very small specimen, previously recorded as Halicometes stellata by Little, and transferred to the genus Timea by Hechtel. However, because the name ‘stellata’ was preoccupied by the type species, T. stellata, the species was renamed T. hechteli, to honour George Hechtel. After the revision of Little's material and new material, we present the re-description of T. hechteli. For both species, partial sequences of COI mtDNA and ITS1-5.8S-ITS2 rDNA region were obtained in order to complement our morphological taxonomy and establish their molecular systematic position among tethyids. Tree topologies for both loci were congruent by grouping together our species as a sister group of the main Tethyida clade, which is according to the current systematics of the group. The COI fragment showed Timea as polyphyletic due to two sequences of Timea (from GenBank) that were clustered with other sponge groups. The species described here are the first record of the genus Timea from the Mexican coast of the Gulf of Mexico. A taxonomic key for West Atlantic Timea species is also presented.

Morphological and genetic investigations have led to the identification of Spiophanes adriaticus sp. nov. (Polychaeta: Spionidae) from the North Adriatic Sea (Central Mediterranean). A total of 81 specimens were recorded along the sublittoral zone between 8 and 27.5 m of depth. This species differs from other congeners by having: two pairs of black eyes, a cirriform occipital antenna, dorsal ciliated organs as thin bands usually extending to chaetigers 11–12, dorsal ciliated crests from chaetiger 14–17, undulate glandular opening on chaetigers 5–7, unhooded hooks from the 15th chaetiger and Y shaped tubes. A detailed description and illustrations are provided for the new species. Through DNA barcoding results and comparison of DNA sequences of the new species with those of other congeners available in the GenBank database, the validity of the new finding was confirmed. Spiophanes adriaticus sp. nov. represents the eighth species of Spiophanes recorded for the Mediterranean Sea. A key for the identification of Mediterranean Spiophanes species is also provided.

Recruitment is related to the occupation of the substrate by fouling organisms. It plays an important role in the maintenance and distribution of benthic populations, being under the influence of biotic and abiotic factors. In the present work, the recruitment of calcareous sponges was monitored over two years in a marina at Todos os Santos Bay, a large bay in the tropical portion of the Brazilian coast. Artificial plates were immersed, being replaced bimonthly and the potential influence of the seawater temperature, photoperiod and precipitation on the number of sponge recruits was tested. The results showed that the number of calcareous sponge recruits had significant temporal variation. Nevertheless, different species showed different patterns over time. Significant differences were observed for Sycon avus, Sycon sp. and Leucandra serrata, and the periods with the highest number of recruits were different amongst them. Sycon bellum, Paraleucilla incomposita, Leucilla sp. and Heteropia glomerosa did not show significant variation in the number of recruits over time. None of the three tested environmental factors were correlated with the number of recruits, but results indicated S. avus recruitment might be driven by seawater temperature. Our results contribute to improve the current knowledge on the dynamics of each species found on the plates and reinforce the general view that the pattern of recruitment varies greatly in Calcarea, even amongst sympatric species.

Although marine phylogeographers have accumulated knowledge of the evolutionary history of various invertebrates, there is a large bias among the taxa regarding genetic data. The order Polycladida is a typical example for which little genetic information at population level is available. Here, we focused on the polyclad flatworm Stylochoplana pusilla, distributed in the Japanese Pacific coastal area. Stylochoplana pusilla is known to have commensal relationships with certain intertidal snails, using snails (mainly Monodonta confusa) as a refugee house. During low tide, S. pusilla hides in the mantle cavity of snails to protect themselves from desiccation and predation. Here, we investigated the genetic structure of S. pusilla using a mitochondrial Cytochrome Oxidase I marker and the species diversity of snails used by it. We found that S. pusilla has high genetic diversity of its populations. While S. pusilla showed a significant genetic differentiation among populations, it was relatively low. In addition, we also showed that S. pusilla used several intertidal snail species which inhabit various coastal environments. The present study suggests S. pusilla has sufficient dispersal ability to connect among its local populations. Also, the range of available snails for S. pusilla may help the connectivity among local populations. We provide important knowledge about this invertebrate taxon with a unique ecology, which has been insufficiently studied.

Previous scientific studies have listed chemical compounds from sea cucumber species. The ability to produce bioactive metabolites derives from their response to various ecological stresses and avoidance of predation. In view of this, the present work aimed to evaluate the antibacterial activity and quantitatively assess the active components of different organs of the sea cucumber Holothuria foskali collected from the north-east of Tunisia. The antibacterial activity of ethyl acetate extracts was tested against Bacillus subtilis, Bacillus cereus, Escherichia coli and Pseudomonas aeruginosa. It was revealed that Escherichia coli and Bacillus subtilis were inhibited by the sea cucumber extracts. To identify the composition of these extracts, Gas Chromatography-Mass Spectroscopy (GC-MS) and Liquid Chromatography-Mass Spectroscopy (LC-MS) methods were used. The GC-MS revealed the presence of 25 major components, the most concentrated ones were characterized as C26H27N5O6 Morphinan-4,5-epoxy-3,6-diol, 6 amino;C17H31F3O2 3-trifluoroacetoxypentadecane; C31H50O2 Stigmasta-5,22-dien-3-ol,acetate; C11H14O2 1-Phthalanol,1,3,3-trimethyl 1-phenyl; C30H48O2 Ergosta-5,22-dien-3-ol,acetate and C25H40O2 (9E)-8-Phenyl-9-octadecenoic acid methyl ester; while the LC-MS revealed the presence of eight molecules, identified as phenolic acid, phytosterol and fat-soluble vitamins. Some molecules are interesting and deserve to be explored for their potential uses as ingredients in functional foods or as raw materials for new drug forms.

Three new species of echinoderid kinorhynchs are described from Daidokutsu, a submarine cave in Ryukyu Islands, Japan. Echinoderes gama sp. nov. is characterized by the presence of middorsal acicular spines on segments 4–8; lateroventral acicular spines on segments 7–9; lateroventral tubes on segment 5; sublateral tubes on segment 8; laterodorsal tubes on segment 10; and type-2 gland cell outlets in subdorsal and lateroventral position on segment 2. Echinoderes kajiharai sp. nov. is defined by the presence of middorsal acicular spines on segments 4, 6, 8; lateral accessory acicular spines on segment 9; lateroventral acicular spines on segments 6–8; lateroventral tubes on segments 2 and 5; midlateral tubes on segment 10; and type-2 gland cell outlets in laterodorsal position on segments 2 and 5, and subdorsal position on segments 8 and 9. Echinoderes uozumii sp. nov. is characterized by the presence of middorsal acicular spines on segments 4 and 6; lateroventral acicular spines on segments 6–9; lateroventral tubes on segments 2 and 5; sublateral tubes on segment 8; laterodorsal tubes on segment 10; type-2 gland cell outlets in subdorsal and lateral accessory position on segment 2; and blunt, short pectinate fringe teeth of primary pectinate fringe on segment 1. In addition, the Echinoderes multiporus species group including E. kajiharai sp. nov., and the Echinoderes bispinosus species group including E. uozumii sp. nov. are established. Furthermore, the distribution of the two species groups and the origin of Echinoderes species in Daidokutsu are discussed.