Crustacean Species Research Articles

Keanekaragaman Kelas Crustacea Sub-Kelas Malacostraca pada Ekosistem Mangrove Pantai Padadita Kabupaten Sumba Timur

The purpose of this study was to determine the diversity of the Crustacea Class Diversity Subclass (Malacostraca) in the mangrove ecosystem of Padadita Beach, East Sumba Regency. The research method used was the quadratic transect and analyzed using a quantitative descriptive approach with the diversity index formula Shannon-Wiener. This study used a sampling technique, namely purposive sampling with a plot size of 2 x 2 meters placed perpendicular to the depth of 200 meters using a plot of 27 plots. The environmental factors measured were temperature, salinity, degree of acidity (pH) and levelsoxygen (DO). Measurements were made at each observation station. The results showed that 5 species of Crustaceans (Malacostraca) that is Gelasimus vocans, Eriphia verrucosa, Ashtoret lunaris, Thalamita stimpsoni and Metopograpsus latifrons. The diversity index obtained is in the moderate category with a value of H’ =1,369.

Marine and estuarine crustacean diversity and assemblage structure in eastern Brazil three years after the Fundão mining dam failure

The present study investigates the spatial and temporal patterns of species richness and assemblage structure of decapod and stomatopod crustaceans in the area impacted by the Fundão dam collapse (Rio Doce basin, Brazil) in November 2015. From October 2018 to September 2019, monthly bottom-trawl samples were collected in estuarine and marine waters of the Rio Doce (directly impacted area) and three other localities. Forty-one crustacean species were recorded, with the overall community structure dominated by six species. The seabob shrimp Xiphopenaeus kroyeri was the most common species, with the coastal marine area near to the Rio Doce mouth being an important fishery ground. Species composition changed significantly among localities, habitats, and seasons, with marine and estuarine assemblages shaped by freshwater discharge. Distribution patterns of species were significantly influenced by the environmental variables potentially altered by tailings, such as turbidity and pH. Species richness and abundance differed among localities; as expected, they were generally higher on the inner shelf than in estuaries and higher during the dry season than the rainy season. Due to the lack of information before the disaster, the low number of species found in the Rio Doce estuary cannot be solely attributed to the disaster but also its freshwater condition. This is the first broad study of the estuarine and coastal marine decapod and stomatopod crustaceans in the region, and we suggest the need for long-term monitoring considering that the effects of this disaster are not easy to detect and probably need multi-year study to be evidenced.

Molecular characterization and transcriptional response to TiO2–GO nanomaterial exposure of two molt-related genes in the juvenile prawn, Macrobrachium rosenbergii

In recent years, with the widespread use of TiO2–GO nanocomposite in industry, especially in the remediation of water environments, its toxic effects on aquatic organisms have received increasing attention. As molting is extremely important for crustaceans in their growth, in this study, we cloned the full-length cDNA sequences of two key genes related to molting, nuclear hormone receptor E75 (E75) and nuclear hormone receptor HR3 (HR3), in Macrobrachium rosenbergii, examined the gene expression profile, and investigated their toxicological effects on crustacean molting through nanomaterial exposure. The amino acid sequences for E75 and HR3 were respectively determined to encode 1138 and 363 acid residues. Sequence analysis showed that both E75 and HR3 contain a HOLI domain, with the E75 of M. rosenbergii being more closely related to the E75 of Palaemon carinicauda. These two genes were expressed at the highest levels in muscle, followed by hepatopancreas. The results showed that the expressions of E75 and HR3 in hepatopancreas and muscle tissues were significantly decreased after exposure to 0.1 mg/L of TiO2–GO composite nanoparticles (P < 0.05). This study will serve as a foundation for subsequent research into the evaluation of nanomaterial toxicity on crustacean species.

A Shift in Communities of Conspicuous Macrocrustaceans Associated with Caribbean Coral Reefs following A Series of Environmental Stressors

In 2015, the communities of reef-associated motile macrocrustaceans (decapods and stomatopods) were compared between two coral reefs with contrasting levels of degradation in Puerto Morelos (Mexican Caribbean), “Limones”, less degraded, with a healthy live coral cover, and “Bonanza”, more degraded, with less live coral and more macroalgae. Since then, several stressors have impacted Puerto Morelos. Massive influxes of floating Sargassum, which reached record levels in 2018, 2021, and 2022, have exacerbated the already high eutrophication of the reef lagoon. An outbreak and rapid propagation of the Stony Coral Tissue Loss Disease in 2018 changed the functionality of reefs. Three back-to-back hurricanes struck the coast close to Puerto Morelos in October 2020 and another one in August 2021. We repeated the study in 2022 to examine the potential changes in the habitat and communities of reef-associated crustaceans since 2015. Reef degradation did not increase significantly between 2015 and 2022, but crustacean species richness, diversity, evenness, and dominance, which differed between reefs in 2015, became similar between reefs in 2022, as did the crustacean community composition. The abundance of herbivore crabs increased in Limones, displacing the coral- and hydrocoral-mutualistic crabs and the abundance of detritivore hermit crabs increased in Bonanza. These results suggest a taxonomic homogenization between reefs, apparently related to subtle ecological changes not necessarily captured by standard metrics of reef condition.

Epilimnetic zooplankton communities in soft-water lakes with isoetids in northern Poland

Soft-water lakes are valuable natural habitats and an important aquatic ecosystems. Lobelia lakes, which are classified based on the occurrence of isoetids, are the most characteristic of this group. The aim of our research was to assess the species richness and structure of pelagic zooplankton communities in the epilimnion of 45 Polish soft-water lakes. The lakes analyzed included a wide range of trophic states from oligotrophic to eutrophic. We noted 79 species of zooplankton, including 49 rotifer, 23 cladoceran, and seven copepod species. The species composition of epilimnetic zooplankton communities in these soft-water lakes was poor, and the species richness and zooplankton biomass were low. In these lakes, the species with the highest frequencies accounted for an important part of the total zooplankton biomass of the zooplankton communities, but the species occurring at lower frequencies differed among the lakes. The most common rotifer taxa were: Keratella cochlearis, Keratella cochlearis var. hispida, Polyarthra euryptera, Gastropus stylifer, and Trichocerca similis. The most important crustacean species in the soft-water lakes were: Macrocyclops albidus, Ceriodaphnia quadrangula, and Eudiaptomus sp. The major factors influencing rotifer species richness were total phosphorus, conductivity, and the trophic state of the lakes. Cladoceran species richness was positively related to lake area and pH, while the species richness of copepod communities was negatively related to chlorophyll a concentrations.

IgE-Mediated Shellfish Allergy in Children.

Shellfish, including various species of mollusks (e.g., mussels, clams, and oysters) and crustaceans (e.g., shrimp, prawn, lobster, and crab), have been a keystone of healthy dietary recommendations due to their valuable protein content. In parallel with their consumption, allergic reactions related to shellfish may be increasing. Adverse reactions to shellfish are classified into different groups: (1) Immunological reactions, including IgE and non-IgE allergic reactions; (2) non-immunological reactions, including toxic reactions and food intolerance. The IgE-mediated reactions occur within about two hours after ingestion of the shellfish and range from urticaria, angioedema, nausea, and vomiting to respiratory signs and symptoms such as bronchospasm, laryngeal oedema, and anaphylaxis. The most common allergenic proteins involved in IgE-mediated allergic reactions to shellfish include tropomyosin, arginine kinase, myosin light chain, sarcoplasmic calcium-binding protein, troponin c, and triosephosphate isomerase. Over the past decades, the knowledge gained on the identification of the molecular features of different shellfish allergens improved the diagnosis and the potential design of allergen immunotherapy for shellfish allergy. Unfortunately, immunotherapeutic studies and some diagnostic tools are still restricted in a research context and need to be validated before being implemented into clinical practice. However, they seem promising for improving management strategies for shellfish allergy. In this review, epidemiology, pathogenesis, clinical features, diagnosis, and management of shellfish allergies in children are presented. The cross-reactivity among different forms of shellfish and immunotherapeutic approaches, including unmodified allergens, hypoallergens, peptide-based, and DNA-based vaccines, are also addressed.

A member of the immunoglobulin superfamily lrig-1 might be involved in the immune priming of Scylla paramamosain in response to the infection and re-infection by Vibrio parahaemolyticus

A member of the immunoglobulin superfamily designated leucine-rich repeats and immunoglobulin-like domains protein-1 (lrig-1) encoding a protein with 1109 amino acids with a characteristic IGc2 domain was identified from the transcriptome data of mud crab Scylla paramamosain. Lrig-1 contained: one signaling peptide; one LRR_NT domain; nine LRR domains; three LRR_TYP domains; one LRR_CT domain; three IGc2 regions; one transmembrane region; C-terminal cytoplasmic tail. lrig-1 was widely expressed in all tissues of mud crab and was responsive in hemocytes to first and second Vibrio parahaemolyticus infections. lrig-1 knockdown mediated by RNAi repressed expression of several antimicrobial peptides significantly. Its orthologs in 19 crustacean species were identified and showed high conservation. These results suggest that lrig-1 have a vital role in mud crabs against V. parahaemolyticus infection through expression of multiple antimicrobial peptides. The results obtained in the present study imply the potential roles the lrig-1 played in immune priming in crabs.

Influence of hydrogen peroxide on hatching of nauplii Artemia sp.

Nauplii of the brine shrimp Artemia sp. are the optimal starter food for many fish and crustaceans species. For this reason, technologies for their production are being improved, including the activation of cysts. The effect of different concentrations of hydrogen peroxide on hatching process a as activator was studied. Its optimal concentration has been determined; it amounts to 0.2-0.4 ml/l. The reasons for various impacts of hydrogen peroxide on different Artemia cysts are formulated. The dynamic of brine shrimp hatching with and without the activator was studied. It has been established that the addition of a hydrogen peroxide solution as an activator increases the hatching of Artemia nauplii, however, it does not impress on the rapidity of Artemia nauplii release from cysts.

Scutellaria polysaccharide mediates the immunity and antioxidant capacity of giant freshwater prawn (Macrobrachium rosenbergii).

The giant freshwater prawn (Macrobrachium rosenbergii) is a commercially valuable freshwater crustacean species that frequently appears a death affected by various diseases, resulting in substantial economic losses. Improving the survival rate of M. rosenbergii is a hot and essential issue for feeding the prawns. Scutellaria polysaccharide (SPS) extracted from Scutellaria baicalensis (a Chinese medicinal herb) is conducive to the survival rate of organisms by enhancing immunity and antioxidant ability. In this study, M. rosenbergii was fed 50, 100, and 150mg/kg of SPS. The immunity and antioxidant capacity of M. rosenbergii were tested by mRNA levels and enzyme activities of related genes. The mRNA expressions of NF-κB, Toll-R, and proPO (participating in the immune response) in the heart, muscle, and hepatopancreas were decreased after four weeks of SPS feeding (P<0.05). This indicated that long-term feeding of SPS could regulate the immune responses of M. rosenbergii tissues. The activity levels of antioxidant biomarkers, alkaline phosphatase (AKP), and acid phosphatase (ACP) had significant increases in hemocytes (P<0.05). Moreover, catalase (CAT) activities in the muscle and hepatopancreas, as well as superoxide dismutase (SOD) activities in all tissues, significantly decreased after four weeks of culture (P<0.05). The results demonstrated that long-term feeding of SPS could improve the antioxidant capacity of M. rosenbergii. In summary, SPS was conducive to regulating the immune capacity and enhancing the antioxidant capacity of M. rosenbergii. These results provide a theoretical basis for supporting SPS addition to the feed of M. rosenbergii.

Involvement of insulin-like growth factor binding proteins (IGFBPs) and activation of insulin/IGF-like signaling (IIS)-target of rapamycin (TOR) signaling cascade in pacific white shrimp, Litopenaeus vannamei exposed to acute low-salinity

Acute low-salinity induces multiple stress responses and significantly impact the health of aquatic animals. However, the molecular regulation network and metabolic adaptation of low salinity stress in aquatic organisms remain unclear. The insulin-like growth factor binding proteins (IGFBPs) and insulin/IGF-like signaling (IIS)-target of rapamycin (TOR) signaling cascade are evolutionarily conserved regulators known to play crucial roles in response to various stressors. In this study, we used the euryhaline Pacific white shrimp (Litopenaeus vannamei) as a model organism to investigate the involvement of IGFBP and IIS-TOR signaling cascade in acute low-salinity response. We found seven LvIGFBPs and evaluated 18s as one of most stable internal reference genes under acute low salinity stress. The expression of LvIGFBP4, LvSIBD1, and LvSIBD2 was significantly increased after 6-hours 5‰ salinity treatment. LvSIBD2 was specifically expressed on the surface of gill branch axis. Acute low-salinity significantly induced the phosphorylation of Akt and S6K in the gill but not in the muscle. We found acute low-salinity increased the levels of total essential amino acids, including leucine and arginine, while decreasing the total non-essential amino acid levels in the gill. Furthermore, glucose and key metabolites in glycolysis and tricarboxylic acid cycle (TCA cycle) were increased, indicating remodeling of energy metabolism occurred. These results demonstrate the involvement of IGFBP and IIS-TOR signaling cascade in acute low-salinity response and provide new insights into understanding the mechanism of osmoregulation in euryhaline crustacean species.

The role of pattern recognition receptors in crustacean innate immunity

AbstractCrustacean species are among the most valued seafood with socioeconomic and ecological implications in the global fisheries sector. Microbial infections to the farming stock due to continued expansion and aquaculture puts global crustacean production at risk. Understanding and reviewing the complex innate immune system of crustaceans would be pivotal in formulating informed decisions for the control and management of epidemic diseases, thus making the global crustacean aquaculture industry sustainable. Under the purview of innate immunity in crustaceans, pattern recognition receptors (PRRs) represent the sensors capable of discriminating non‐self pathogenic modules and invoking the activation of immune responses. The immunity to infections can be manifested at cellular (via phagocytosis, apoptosis, nodulation and encapsulation) and humoral (effected by prophenoloxidase cascade, lectins, antimicrobial proteins) levels leading to the elimination of pathogens or subversion of the pathogenic implications. In this review, we discuss the participatory role of 12 types of PRRs identified from crustacean species with an exhaustive focus on structural and functional specificities in binding to pathogens and possible execution of the immune activity. Moreover, we have elaborated on the PRRs‐associated or possible signalling cascades (Toll‐NFκB, IMD‐NFκB and JAK‐STAT) in crustacean species that could bridge our understanding of the resistance or susceptibility of the host to varied pathogenic infections thus providing clues to the regulatory mechanisms involved in pathogenesis of infectious diseases and mechanisms of immunity.

Legacy and Emerging Per- and Polyfluoroalkyl Substances in a Subtropical Marine Food Web: Suspect Screening, Isomer Profile, and Identification of Analytical Interference.

The ban/elimination of legacy per- and polyfluoroalkyl substances (PFASs) has led to a dramatic increase in the production and use of various emerging PFASs over the past decade. However, trophodynamics of many emerging PFASs in aquatic food webs remain poorly understood. In this study, samples of seawaters and marine organisms including 15 fish species, 21 crustacean species, and two cetacean species were collected from the northern South China Sea (SCS) to investigate the trophic biomagnification potential of legacy and emerging PFASs. Bis(trifluoromethylsulfonyl)imide was found in seawater via suspect screening (concentration up to 1.50 ng/L) but not in the biota, indicating its negligible bioaccumulation potential. A chlorinated perfluorooctane sulfonate (PFOS) analytical interfering compound was identified with a predicted formula of C14H23O5SCl6- (most abundant at m/z = 514.9373). Significant trophic magnification was observed for 22 PFASs, and the trophic magnification factors of cis- and trans-perfluoroethylcyclohexane sulfonate isomers (1.92 and 2.25, respectively) were reported for the first time. Perfluorohexanoic acid was trophic-magnified, possibly attributed to the PFAS precursor degradation. The hazard index of PFOS was close to 1, implying a potential human health risk via dietary exposure to PFASs in seafood on the premise of continuous PFAS discharge to the SCS.

RNAi Analysis of Potential Functions of Cyclin B3 in Reproduction of Male Oriental River Prawns (Macrobrachium nipponense).

Cyclin B3 (CycB3) is involved in the metabolic pathway of the cell cycle, playing essential roles in the regulation of cell proliferation and mitosis. CycB3 is also predicted to be involved in the reproduction of male oriental river prawns (Macrobrachium nipponense). In this study, the potential functions of CycB3 in M. nipponense were investigated using quantitative real-time PCR, RNA interference, and histological observations. The full-length DNA sequence of CycB3 in M. nipponense was 2147 base pairs (bp) long. An open reading frame of 1500 bp was found, encoding 499 amino acids. A highly conserved destruction box and two conserved cyclin motifs were found in the protein sequence of Mn-CycB3. Phylogenetic tree analysis revealed that this protein sequence was evolutionarily close to that of CycB3s of crustacean species. Quantitative real-time PCR analysis results suggested that CycB3 was involved in the process of spermiogenesis, oogenesis, and embryogenesis in M. nipponense. RNA interference analysis showed that CycB3 had a positive regulatory relationship with insulin-like androgenic gland hormone (IAG) in M. nipponense. In addition, sperm were rarely observed in the testis of double-stranded CycB3-injected prawns after 14 days of treatment, and sperm abundance was dramatically lower than that in the double-stranded GFP-injected prawns on the same day. This result indicated that CycB3 can regulate the testis reproduction in M. nipponense through inhibiting the IAG expressions. Overall, these results indicated that CycB3 plays essential roles in the regulation of male reproduction in M. nipponense, which may promote the studies of male reproduction in other crustacean species.

The use of polarized light in the zonal orientation of the sandhopper Talitrus saltator (Montagu)

It is well known that the celestial polarization is used as a compass cue by many species of insects and crustaceans. Although it has been shown that the sandhopper Talitrus saltator perceives polarized light and possesses an arrangement of the rhabdomeres that could allow e-vector interpretation and utilization, T. saltator does not use the e-vector of the skylight polarization as a compass cue when making excursions along the sea–land axis of sandy shores. We performed tests in confined conditions to clarify if skylight polarization is somehow involved in the zonal recovery of T. saltator. We observed the directional responses of sandhoppers in a transparent bowl under an artificial sky (an opaline Plexiglas dome). The bowl was covered by a blue gelatin filter with a grey filter (control condition) and a linear polarizing filter (experimental conditions) positioned under the blue one in such a way as to occupy half of the upper surface of the Plexiglas bowl so as to create a linear polarization gradient. Our experiments confirm that T. saltator perceives polarized light and highlight that this visual capability determines the perception, or perhaps the increase, of the radiance and/or spectral gradient and their use as compass cues in the zonal orientation. Moreover, our findings confirm that the radiance gradient is used as a chronometric compass orienting reference in the absence of other celestial orienting cues.

Diet and Temperature Effects on the Survival of Larval Red Deep-Sea Crabs, Chaceon quinquedens (Smith, 1879), under Laboratory Conditions

Declines in commercial crustacean species (such as lobsters, king crab, etc.) have caused an increased interest in the harvest of the red deep-sea crab Chaceon quinquedens. The red deep-sea crab is a federally managed fishery; however, little is known about the species’ general biology, especially the conditions required for larval survival. We aimed to answer two main questions about the life history of the red deep-sea crab. First, is there a common larval hatching pattern between adult female crabs? Specifically, our inquiries are about the duration of the hatching process, daily peak hatching time, and the relationship between female morphometry and the total larvae hatched. Second, which are the factors affecting the survival and development of larval red deep-sea crabs? In order to answer these research questions, we studied the effects of diet (rotifers, Artemia sp., algae, and unfed), temperature (9 °C, 15 °C, and 20 °C), and aquaculture settings. Ovigerous females were obtained from commercial traps and transported to the NOAA James J. Howard Laboratory, NJ. They were placed in the Females Husbandry and Hatching Collection System (FHCS), where the larvae hatched. Hatching of adult females was monitored and measured by volume. A simple linear regression (SLR) was calculated to predict the number of larvae hatched based on the measured volumes, and it was significant (F = 1196; df = 1, 13; R2 = 0.9892, p = 3.498 × 10−14). Duration of hatching period showed an approximate 30 days for adult females red deep-sea crabs, with a common daily maximum hatching time at 22:00 hrs (hatching time seem to follow the sun cycle and the first hours after sunset, Perez, pers. observation). Linear polynomial quadratic regressions were conducted for both years with an interaction term for the two continuous variables (diet and temperature), and were used to model the proportion of larval survival through time. In both years, a highly significant difference was obtained (F = 56.15; df = 4, 2134; R2 = 0.09353; p = &lt; 2.2 × 10−16). There is an effect of diet and temperature in the survival of red deep-sea crabs, but not a combined effect of them.

Artificial Seaweed Substrates Complement ARMS in DNA Metabarcoding-Based Monitoring of Temperate Coastal Macrozoobenthos

We used DNA metabarcoding to compare macrozoobenthic species colonization between autonomous reef monitoring structures (ARMS) and artificial seaweed monitoring systems (ASMS). We deployed both substrates in two different locations (Ría de Vigo and Ría de Ferrol, NW Iberian coast) and collected them after 6, 9, and 12 months to assess species composition of the colonizing communities through high-throughput sequencing of amplicons within the barcode region of the mitochondrial cytochrome c oxidase I (COI-5P) and the V4 domain of the 18S rRNA genes. We observed a consistently low similarity in species composition between substrate types, independently of sampling times and sites. A large fraction of exclusive species was recorded for a given substrate (up to 72%), whereas only up to 32% of species were recorded in both substrates. The shape and structural complexity of the substrate strongly affected the colonization preferences, with ASMS detecting more exclusive crustacean and gastropod species and a broader diversity of taxonomic groups (e.g., Entoprocta and Pycnogonida were detected exclusively in ASMS). We demonstrate that despite the customary use of ARMS for macrozoobenthos monitoring, by using ASMS we complemented the recovery of species and enlarged the scope of the taxonomic diversity recorded.

Phototaxis in Two Shallow-Water Zeuxo Species (Crustacea: Tanaidacea).

Different crustacean species can differ in their response to light. In Tanaidacea, a small group of aquatic, benthic crustaceans, previous studies suggested that several species may be positively phototactic based on their attraction to nocturnal light traps, but no experimental investigations of phototaxis had been conducted on this group. Here we show experimentally that two species in the genus Zeuxo are phototactic but exhibit opposite reactions to light; Zeuxo ezoensis, which inhabits the blades and stipes of seaweeds, was positively phototactic, whereas Zeuxo molybi, which inhabits muddy sediments overlying bedrock, was negatively phototactic. This differential response may reflect differences in photoenvironment between these species' microhabitats.

Simple pot modification improves catch efficiency and species composition in a tropical estuary mud crab (Scylla serrata) fishery

Pots are widely used fishing gear type for targeting different crustacean and fish species. Pot entrance size and design are among the most important technical parameters that influence the catch efficiency of certain species. An optimal pot entrance design should allow an efficient entry for the target species while preventing subsequent escape. The tropical estuary pot fishery targeting mud crab (Scylla serrata) in Vembanad Lake, India, employs rectangular pots with rectangular-shaped entrances. Low catch rates for target species and high bycatch rates are observed in this fishery. This study was carried out to investigate if a simple pot modification by extending the entrance of the traditional pots, can improve the catch efficiency of mud crab. Further, we estimated and compared the catch composition in this small-scale fishery using the traditional and modified entrance pots. The results showed that the catch efficiency for all sizes of mud crab is on average more than six times higher with the modified entrance pots compared to the traditional pots (622% (CI: 344–1867%)). However, significant quantities of juvenile crabs are caught in modified pots. Further, the bycatch ratio was significantly reduced for modified compared to the standard entrance pots in this fishery. These results show that such pot modifications have potential to significantly improve the catches in mud crab pot fisheries without increase in capture of bycatch species. However, additional mechanisms for excluding undersized crabs from pot catches should be investigated.

Hidden in plain sight: two new species of decapod crustaceans (Palaemonidae and Porcellanidae) discovered in the Red Sea on a university campus in Saudi Arabia.

Two new symbiotic species of decapod crustaceans, a palaemonid shrimp and a porcellanid crab, are described from the same type locality situated on the campus of the King Abdullah University of Science and Technology (KAUST) in Thuwal, on the Red Sea coast of Saudi Arabia. The palaemonid shrimp Palaemonella jamila sp. nov. is described based on one male and one female, whereas the porcellanid crab Enosteoides habibi sp. nov. is described based on three males and two females. Unfortunately, the originally collected and studied specimens were lost shortly after study. However, subsequent recollection of one specimen of P. jamila sp. nov. and one specimen of E. habibi sp. nov. enabled to deposit a holotype of each new species in the collections of the Florida Museum of Natural History, Gainesville, USA. Both species inhabit burrows of goby-associated snapping shrimps, Alpheus spp., in the shallow subtidal areas, at depths less than 1 m. In addition, a single female specimen of Palaemonella aliska Marin, 2008 collected at Al Fahal reef off KAUST represents the first record of the species in the Red Sea and the Indian Ocean, and a considerable range extension of its previously known distribution range. This species may be a close relative of P. jamila sp. nov., to which it is also ecologically similar. The present study highlights the necessity of prospecting the largely neglected and still undersampled shallow subtidal habitats of the Red Sea, and the Indo-West Pacific in general.

Development of a yeast reporter gene assay to detect ligands of freshwater cladoceran Daphnia magna ultraspiracle, a homolog of vertebrate retinoid X receptors.

Endocrine-disrupting chemicals (EDCs) often affect homeostatic regulation in living organisms by directly acting on nuclear receptors (NRs). Retinoid X receptors (RXRs), the most highly conserved members of the NR superfamily during evolution, function as partners to form heterodimers with other NRs, such as retinoic acid, thyroid hormone, and vitamin D3 receptors. RXRs also homodimerize and induce the expression of target genes upon binding with their natural ligand, 9-cis-retinoic acid (9cRA), and typical EDCs organotin compounds, such as tributyltin and triphenyltin. In the present study, we established a new yeast reporter gene assay (RGA) to detect the ligands of freshwater cladoceran Daphnia magna ultraspiracle (Dapma-USP), a homolog of vertebrate RXRs. D.magna has been used as a representative crustacean species for aquatic EDC assessments in the Organization for Economic Corporation and Development test guidelines. Dapma-USP was expressed along with the Drosophila melanogaster steroid receptor coactivator Taiman in yeast cells carrying the lacZ reporter plasmid. The RGA for detecting agonist activity of organotins and o-butylphenol was improved by use of mutant yeast strains lacking genes encoding cell wall mannoproteins and/or plasma membrane drug efflux pumps as hosts. We also showed that a number of other human RXR ligands, phenol and bisphenol A derivatives, and terpenoid compounds such as 9c-RA exhibited antagonist activity on Dapma-USP. Our newly established yeast-based RGA system is valuable as the first screening tool to detect ligand substances for Dapma-USP and for evaluating the evolutionary divergence of the ligand responses of RXR homologs between humans and D.magna.