ResearchPad - crustaceans https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[The 2015-2016 El Niño increased infection parameters of copepods on Eastern Tropical Pacific dolphinfish populations]]> https://www.researchpad.co/article/elastic_article_7672 The oceanographic conditions of the Pacific Ocean are largely modified by El Niño (EN), affecting several ecological processes. Parasites and other marine organisms respond to environmental variation, but the influence of the EN cycle on the seasonal variation of parasitic copepods has not been yet evaluated. We analysed the relation between infection parameters (prevalence and mean intensity) of the widespread parasitic copepods Caligus bonito and Charopinopsis quaternia in the dolphinfish Coryphaena hippurus and oceanography during the strong 2015–16 EN. Fish were collected from capture fisheries on the Ecuadorian coast (Tropical Eastern Pacific) over a 2-year period. Variations of sea surface temperature (SST), salinity, chlorophyll a (Chl-a), Oceanic Niño Index (ONI), total host length (TL) and monthly infection parameters of both copepod species were analysed using time series and cross-correlations. We used the generalised additive models for determine the relationship between environmental variables and infection parameters. The total body length of the ovigerous females and the length of the eggs of C. bonito were measured in both periods. Infection parameters of both C. bonito and Ch. quaternia showed seasonal and annual patterns associated with the variation of environmental variables examined (SST, salinity, Chl-a and ONI 1+2). Infection parameters of both copepod species were significantly correlated with ONI 1+2, SST, TL and Chl-a throughout the GAMLSS model, and the explained deviance contribution ranged from 16%-36%. Our results suggest than an anomaly higher than +0.5°C triggers a risen in infection parameters of both parasitic copepods. This risen could be related to increases in egg length, female numbers and the total length of the ovigerous females in EN period. This study provides the first evidence showing that tropical parasitic copepods are sensitive to the influence of EN event, especially from SST variations. The observed behaviour of parasitic copepods likely affects the host populations and structure of the marine ecosystem at different scales.

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<![CDATA[Perceived socio-economic impacts of the marbled crayfish invasion in Madagascar]]> https://www.researchpad.co/article/N7a6c5db8-4016-4d26-87a6-87422e70e8c1

The negative environmental and economic impacts of many invasive species are well known. However, given the increased homogenization of global biota, and the difficulty of eradicating species once established, a balanced approach to considering the impacts of invasive species is needed. The marbled crayfish (Procambarus virginalis) is a parthenogenetic freshwater crayfish that was first observed in Madagascar around 2005 and has spread rapidly. We present the results of a socio-economic survey (n = 385) in three regions of Madagascar that vary in terms of when the marbled crayfish first arrived. Respondents generally considered marbled crayfish to have a negative impact on rice agriculture and fishing, however the animals were seen as making a positive contribution to household economy and food security. Regression modeling showed that respondents in regions with longer experience of marbled crayfish have more positive perceptions. Unsurprisingly, considering the perception that crayfish negatively impact rice agriculture, those not involved in crayfish harvesting and trading had more negative views towards the crayfish than those involved in crayfish-related activities. Food preference ranking and market surveys revealed the acceptance of marbled crayfish as a cheap source of animal protein; a clear positive in a country with widespread malnutrition. While data on biodiversity impacts of the marbled crayfish invasion in Madagascar are still completely lacking, this study provides insight into the socio-economic impacts of the dramatic spread of this unique invasive species. Biby kely tsy fantam-piaviana, mahavelona fianakaviana” (a small animal coming from who knows where which supports the needs of the family). Government worker Analamanga, Madagascar.

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<![CDATA[Origin of the natural variation in the storage of dietary carotenoids in freshwater amphipod crustaceans]]> https://www.researchpad.co/article/N905bc2f7-7243-429f-9b99-7855ae079227

Carotenoids are diverse lipophilic natural pigments which are stored in variable amounts by animals. Given the multiple biological functions of carotenoids, such variation may have strong implications in evolutionary biology. Crustaceans such as Gammarus amphipods store large amounts of these pigments and inter-population variation occurs. While differences in parasite selective pressure have been proposed to explain this variation, the contribution of other factors such as genetic differences in the gammarid ability to assimilate and/or store pigments, and the environmental availability of carotenoids cannot be dismissed. This study investigates the relative contributions of the gammarid genotype and of the environmental availability of carotenoids in the natural variability in carotenoid storage. It further explores the link of this natural variability in carotenoid storage with major crustacean immune parameters. We addressed these aspects using the cryptic diversity in the amphipod crustacean Gammarus fossarum and a diet supplementation protocol in the laboratory. Our results suggest that natural variation in G. fossarum storage of dietary carotenoids results from both the availability of the pigments in the environment and the genetically-based ability of the gammarids to assimilate and/or store them, which is associated to levels of stimulation of cellular immune defences. While our results may support the hypothesis that carotenoids storage in this crustacean may evolve in response to parasitic pressure, a better understanding of the specific roles of this large pigment storage in the crustacean physiology is needed.

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<![CDATA[Na+/H+ exchanger (NHE) in Pacific white shrimp (Litopenaeus vannamei): Molecular cloning, transcriptional response to acidity stress, and physiological roles in pH homeostasis]]> https://www.researchpad.co/article/5c803c66d5eed0c484ad88a5

Na+/H+ exchangers are the most common membrane proteins involved in the regulation of intracellular pH that concurrently transport Na+ into the cells and H+ out of the cells. In this study, the full-length cDNA of the Na+/H+ exchanger (NHE) from the Pacific white shrimp (Litopenaeus vannamei) was cloned. The LvNHE cDNA is 3167 bp long, contains a 5’-untranslated region (UTR) of 74 bp and a 3’-UTR of 456 bp and an open reading frame (ORF) of 2637 bp, coding for a protein of 878 amino acids with 11 putative transmembrane domains and a long cytoplasmic tail. LvNHE shows high sequence homology with mud crab NHE at the amino acid level. LvNHE mRNA was detected in the hepatopancreas, gill, eyestalk, skin, heart, intestine, muscle, brain and stomach, with the highest abundance in the intestine. In the shrimp intestinal fragment cultures exposed to gradually declining pH medium (from pH 8.0 to pH 6.4), the LvNHE mRNA expression was significantly stimulated, with the highest response when incubated in pH 7.0 medium for 6 h. To investigate the functional roles of LvNHE in pH regulation at the physiological and cellular levels, the LvNHE mRNA expression was silenced by siRNA knockdown. Upon low-pH challenge, the hemolymph pH was significantly reduced in the LvNHE mRNA knockdown shrimp. In addition, knockdown of LvNHE mRNA reduced the recovery capacity of intracellular pH in intestinal fragment cultures after acidification. Altogether, this study demonstrates the role of NHE in shrimp response to low pH stress and provides new insights into the acid/base homeostasis mechanisms of crustaceans.

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<![CDATA[Common bottlenose dolphin (Tursiops truncatus) behavior in an active narrow seaport]]> https://www.researchpad.co/article/5c75ac7ad5eed0c484d08871

The Galveston Ship Channel (GSC) is a narrow, congested waterway that supports large-scale shipping, commercial fishing, dolphin tourism, and recreation. Human activity and common bottlenose dolphins (Tursiops truncatus) converge in the GSC with potentially negative consequences on the dolphins. Elevated land-based tracking and behavioral observation of dolphins and vessels were conducted along the GSC in June-August 2013 using a digital theodolite. Positional information was used to calculate dolphin movement patterns and proximity to vessels. Log-likelihood ratio and Chi-square contingency tests were used to assess behavioral states, and generalized additive models were used to analyze movement patterns (i.e., swimming speed, reorientation rate, and linearity) relative to endogenous and exogenous factors and vessel presence. Dolphins regularly use the GSC to forage (57% of observed behavioral states) and socialize (27%), and it is not a travel corridor for accessing other favorable sites (traveling = 5%). Dolphin behavior varied significantly based on time of day, group size, calf presence, and general boat presence. When boats were present, the proportion of time dolphins spent socializing and foraging was significantly less than expected by chance. Swimming speeds increased significantly in the presence of small recreational boats, dolphin-watching tour boats, shrimp trawlers, and when tour boats and shrimp trawlers were both present. Reorientation rate increased significantly in the presence of tour boats and trawlers. Dolphin behavioral responses to vessel presence may result in decreased energy consumption due to disrupted foraging activity. Without proper management, the observed behavioral changes may be detrimental to individuals within this population in the short term, with potential long-term consequences to health and survivorship.

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<![CDATA[The polymeric immunoglobulin receptor-like protein from Marsupenaeus japonicus is a receptor for white spot syndrome virus infection]]> https://www.researchpad.co/article/5c648d59d5eed0c484c82645

Viral entry into the host cell is the first step towards successful infection. Viral entry starts with virion attachment, and binding to receptors. Receptor binding viruses either directly release their genome into the cell, or enter cells through endocytosis. For DNA viruses and a few RNA viruses, the endocytosed viruses will transport from cytoplasm into the nucleus followed by gene expression. Receptors on the cell membrane play a crucial role in viral infection. Although several attachment factors, or candidate receptors, for the infection of white spot syndrome virus (WSSV) were identified in shrimp, the authentic entry receptors for WSSV infection and the intracellular signaling triggering by interaction of WSSV with receptors remain unclear. In the present study, a receptor for WSSV infection in kuruma shrimp, Marsupenaeus japonicus, was identified. It is a member of the immunoglobulin superfamily (IgSF) with a transmembrane region, and is similar to the vertebrate polymeric immunoglobulin receptor (pIgR); therefore, it was designated as a pIgR-like protein (MjpIgR for short). MjpIgR was detected in all tissues tested, and its expression was significantly induced by WSSV infection at the mRNA and protein levels. Knockdown of MjpIgR, and blocking MjpIgR with its antibody inhibited WSSV infection in shrimp and overexpression of MjpIgR facilitated the invasion of WSSV. Further analyses indicated that MjpIgR could independently render non-permissive cells susceptible to WSSV infection. The extracellular domain of MjpIgR interacts with envelope protein VP24 of WSSV and the intracellular domain interacts with calmodulin (MjCaM). MjpIgR was oligomerized and internalized following WSSV infection and the internalization was associated with endocytosis of WSSV. The viral internalization facilitating ability of MjpIgR could be blocked using chlorpromazine, an inhibitor of clathrin dependent endocytosis. Knockdown of Mjclathrin and its adaptor protein AP-2 also inhibited WSSV internalization. All the results indicated that MjpIgR-mediated WSSV endocytosis was clathrin dependent. The results suggested that MjpIgR is a WSSV receptor, and that WSSV enters shrimp cells via the pIgR-CaM-Clathrin endocytosis pathway.

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<![CDATA[Marine environmental DNA biomonitoring reveals seasonal patterns in biodiversity and identifies ecosystem responses to anomalous climatic events]]> https://www.researchpad.co/article/5c6730a5d5eed0c484f37e31

Marine ecosystems are changing rapidly as the oceans warm and become more acidic. The physical factors and the changes to ocean chemistry that they drive can all be measured with great precision. Changes in the biological composition of communities in different ocean regions are far more challenging to measure because most biological monitoring methods focus on a limited taxonomic or size range. Environmental DNA (eDNA) analysis has the potential to solve this problem in biological oceanography, as it is capable of identifying a huge phylogenetic range of organisms to species level. Here we develop and apply a novel multi-gene molecular toolkit to eDNA isolated from bulk plankton samples collected over a five-year period from a single site. This temporal scale and level of detail is unprecedented in eDNA studies. We identified consistent seasonal assemblages of zooplankton species, which demonstrates the ability of our toolkit to audit community composition. We were also able to detect clear departures from the regular seasonal patterns that occurred during an extreme marine heatwave. The integration of eDNA analyses with existing biotic and abiotic surveys delivers a powerful new long-term approach to monitoring the health of our world’s oceans in the context of a rapidly changing climate.

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<![CDATA[Mesoscale circulation determines broad spatio-temporal settlement patterns of lobster]]> https://www.researchpad.co/article/5c5df326d5eed0c484580db3

The influence of physical oceanographic processes on the dispersal of larvae is critical for understanding the ecology of species and for anticipating settlement into fisheries to aid long-term sustainable harvest. This study examines the mechanisms by which ocean currents shape larval dispersal and supply to the continental shelf-break, and the extent to which circulation determines settlement patterns using Sagmariasus verreauxi (Eastern Rock Lobster, ERL) as a model species. Despite the large range of factors that can impact larval dispersal, we show that within a Western Boundary Current system, mesoscale circulation explains broad spatio-temporal patterns of observed settlement including inter-annual and decadal variability along 500 km of coastline. To discern links between ocean circulation and settlement, we correlate a unique 21- year dataset of observed lobster settlement (i.e., early juvenile & pueruli abundance), with simulated larval settlement. Simulations use outputs of an eddy-resolving, data-assimilated, hydrodynamic model, incorporating ERL spawning strategy and larval duration. The latitude where the East Australian Current (EAC) deflects east and separates from the continent determines the limit between regions of low and high ERL settlement. We found that years with a persistent EAC flow have low settlement while years when mesoscale eddies prevail have high settlement; in fact, mesoscale eddies facilitate the transport of larvae to the continental shelf-break from offshore. Proxies for settlement based on circulation features observed with satellites could therefore be useful in predicting broadscale patterns of settlement orders of magnitudes to guide harvest limits.

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<![CDATA[Efficacy assessment of commercially available natural products and antibiotics, commonly used for mitigation of pathogenic Vibrio outbreaks in Ecuadorian Penaeus (Litopenaeus) vannamei hatcheries]]> https://www.researchpad.co/article/5c5b52ebd5eed0c4842bd266

Bacterial diseases cause high mortality in Penaeus (Litopenaeus) vannamei postlarvae. Therefore, appropriate application of efficient therapeutic products is of vital importance for disease control. This study evaluated through in vitro analyses the antimicrobial effectiveness of commercial therapeutic products used for P. vannamei bacterial diseases and antibiotics against pathogenic Vibrio strains circulating in Ecuadorian hatcheries. Twenty strains were isolated from 31 larvae samples with high bacterial counts from 10 hatcheries collected during mortality events. The strains virulence was verified through challenge tests with Artemia franciscana nauplii and P. vannamei postlarvae. Through 16S rRNA sequence analysis, strains showed a great similarity to the Vibrio sequences reported as pathogens, with 95% belonging to the Harveyi clade. Through antibiograms and minimal inhibitory concentration (MIC) in vitro tests we found that furazolidone, ciprofloxacin, chloramphenicol, norfloxacin, nalidixic acid, florfenicol, fosfomycin and enrofloxacin inhibited the growth of all or most of the strains. Less efficient antibiotics were penicillin, oxytetracycline and tetracycline. A multiple antibiotic resistance (MAR) index of 0.23 showed some level of resistance to antibiotics, with two MAR prevalent patterns (Penicillin-Oxytetracycline and Penicillin-Oxytetracycline-Tetracycline). From a total of 16 natural products (five probiotics, nine organic acids and two essential oils), only three (one probiotic, one organic acid and one essential oil) were effective to control most of the strains. Shrimp producers can apply relatively simple in vitro analyses, such as those employed in this study, to help take adequate management decisions to reduce the impact of bacterial diseases and increase profit.

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<![CDATA[Sensitivity of multispecies maximum sustainable yields to trends in the top (marine mammals) and bottom (primary production) compartments of the southern North Sea food-web]]> https://www.researchpad.co/article/5c58d64ed5eed0c484031b3c

In marine ecosystems, maximum sustainable yield considerations are affected by any substantial changes that occur in the top and bottom compartments of the food-web. This study explores how the southern North Sea’s fisheries may need to adjust their fishing efforts to maintain optimum yields of sole, plaice, cod and brown shrimps under increased marine mammal populations and a reduced primary productivity. We constructed plausible scenarios of ongoing food-web changes using the results of Bayesian age-structured population models to estimate carrying capacities of harbour porpoises (Phocoena phocoena) and grey seals (Halichoerus grypus). Losses in primary productivity were predicted by lower trophic level ecosystem models. These scenarios were implemented in a food-web model of the southern North Sea. For each scenario, we sought mixed-fleet fishing efforts that would deliver maximum yields of sole, plaice, cod and brown shrimp combined. We also did so for a baseline run with unaltered mammal and primary production, and compared the differences in optimal fishing strategies, predicted yields, and states of the stocks between the scenarios. We found stocks and yields to be far more sensitive to changes in primary productivity than to increased marine mammal predation. The latter predominantly impacted cod, and even benefitted brown shrimps compared to the baseline run. Under 30% reduced primary productivity, fishing efforts had to be reduced by 50% to still provide maximum yields, whereas the marine mammal scenario induced no need to adjust the fishing regime. This draws attention to the potential gains of incorporating bottom-up processes into long-term management considerations, while marine mammal predation may be less of a concern, in particular for flatfish fisheries in the North Sea, and may even benefit shrimp trawlers because of reduced predation on shrimp from fish predators.

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<![CDATA[Predicting ecosystem components in the Gulf of Mexico and their responses to climate variability with a dynamic Bayesian network model]]> https://www.researchpad.co/article/5c521879d5eed0c484798772

The Gulf of Mexico is an ecologically and economically important marine ecosystem that is affected by a variety of natural and anthropogenic pressures. These complex and interacting pressures, together with the dynamic environment of the Gulf, present challenges for the effective management of its resources. The recent adoption of Bayesian networks to ecology allows for the discovery and quantification of complex interactions from data after making only a few assumptions about observations of the system. In this study, we apply Bayesian network models, with different levels of structural complexity and a varying number of hidden variables to account for uncertainty when modeling ecosystem dynamics. From these models, we predict focal ecosystem components within the Gulf of Mexico. The predictive ability of the models varied with their structure. The model that performed best was parameterized through data-driven learning techniques and accounted for multiple ecosystem components’ associations and their interactions with human and natural pressures over time. Then, we altered sea surface temperature in the best performing model to explore the response of different ecosystem components to increased temperature. The magnitude and even direction of predicted responses varied by ecosystem components due to heterogeneity in driving factors and their spatial overlap. Our findings suggest that due to varying components’ sensitivity to drivers, changes in temperature will potentially lead to trade-offs in terms of population productivity. We were able to discover meaningful interactions between ecosystem components and their environment and show how sensitive these relationships are to climate perturbations, which increases our understanding of the potential future response of the system to increasing temperature. Our findings demonstrate that accounting for additional sources of variation, by incorporating multiple interactions and pressures in the model layout, has the potential for gaining deeper insights into the structure and dynamics of ecosystems.

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<![CDATA[Comparative transcriptome analysis reveals osmotic-regulated genes in the gill of Chinese mitten crab (Eriocheir sinensis)]]> https://www.researchpad.co/article/5c40f75ad5eed0c484385f57

Salinity is one of the most important abiotic factors directly affecting the reproduction, molting, growth, immune, physiological and metabolic activities of Chinese mitten crab (Eriocheir sinensis). This species has strong osmoregulatory capacity and can maintain stringent internal homeostasis. However, the mechanisms conferring tolerance to salinity fluctuations are not well understood. To reveal the genes and pathways involved in osmoregulation, adult male crabs (body weight = 110 ± 5 g) were acclimated for 144 h in freshwater (FW, 0 ppt) or seawater (SW, 25 ppt). Changes in the transcriptome of crab gills were then analysed by RNA-Seq, and 174,903 unigenes were obtained. Comparison of genes between FW- SW-acclimated groups identified 932 genes that were significantly differentially expressed in the gill, comprising 433 and 499 up- and downregulated transcripts. Gene Ontology functional enrichment analysis revealed that important biological processes related to salt stress were significantly enriched, including energy metabolism, ion transport, signal transduction and antioxidant activity. Kyoto Encyclopaedia of Genes and Genomes enrichment analysis mapped the differentially expressed genes to 241 specific metabolic pathways, and pathways related to energy metabolism, oxidative phosphorylation and the tricarboxylic acid (TCA)/citrate cycle were significantly enriched. Salinity stress altered the expression of many enzymes involved in energy metabolism, ion transport, signal transduction and antioxidant pathways, including citrate synthase (CS), Na+/K+-ATPase (NKA), Na+-K+-2Cl cotransporter-1 (NKCC1), dopamine receptor D1 (DRD1), synaptic binding protein 1 (STXBP1), Cu2+/Zn2+ superoxide dismutase (SOD1) and glutathione S-transferase (GST). Additionally, the obtained transcriptomic sequencing data provided a useful resource for identification of novel genes, and further physiological analysis of Chinese mitten crab.

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<![CDATA[The transcriptome sequencing and functional analysis of eyestalk ganglions in Chinese mitten crab (Eriocheir sinensis) treated with different photoperiods]]> https://www.researchpad.co/article/5c478c7bd5eed0c484bd294c

Photoperiod plays an important role in individual growth, development, and metabolism in crustaceans. The growth and reproduction of crabs are closely related to the photoperiod. However, as of yet, there are still no transcriptomic reports of eyestalk ganglions treated under different photoperiods in the Chinese mitten crab (Eriocheir sinensis), which is a benthonic crab with high commercial value in Asia. In this study, we collected the eyestalk ganglions of crabs that were reared under different photoperiods, including a control group (L: D = 12 h: 12 h, named CC), a constant light group (L: D = 24 h: 0 h, named LL) and a constant darkness group (L: D = 0 h: 24 h, named DD). RNA sequencing was performed on these tissues in order to examine the effects of different photoperiods. The total numbers of clean reads from the CC, LL and DD groups were 48,772,584 bp, 53,943,281 bp and 53,815,178 bp, respectively. After de novo assembly, 161,380 unigenes were obtained and were matched with different databases. The DEGs were significantly enriched in phototransduction and energy metabolism pathways. Results from RT-qPCR showed that TRP channel protein (TRP) in the phototransduction pathway had a significantly higher level of expression in LL and DD groups than in the CC group. We found that the downregulation of the pyruvate dehydrogenase complex (PDC) gene and the upregulation phosphoenolpyruvate carboxykinase (PPC) gene were involved in energy metabolism processes in LL or DD. In addition, we also found that the upregulation of the expression level of the genes Gαq, pyruvate kinase (PK), NADH peroxidase (NADH) and ATPase is involved in phototransduction and energy metabolism. These results may shed some light on the molecular mechanism underlying the effect of photoperiod in physiological activity of E. sinensis.

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<![CDATA[Upwelling modulation of functional traits of a dominant planktonic grazer during “warm-acid” El Niño 2015 in a year-round upwelling area of Humboldt Current]]> https://www.researchpad.co/article/5c46653ed5eed0c484518309

Climate change is expected to exacerbate upwelling intensity and natural acidification in Eastern Boundaries Upwelling Systems (EBUS). Conducted between January-September 2015 in a nearshore site of the northern Humboldt Current System directly exposed to year-round upwelling episodes, this study was aimed at assessing the relationship between upwelling mediated pH-changes and functional traits of the numerically dominant planktonic copepod-grazer Acartia tonsa (Copepoda). Environmental temperature, salinity, oxygen, pH, alkalinity, chlorophyll-a (Chl), copepod adult size, egg production (EP), and egg size and growth were assessed through 28 random oceanographic surveys. Agglomerative clustering and multidimensional scaling identified three main di-similitude nodes within temporal variability of abiotic and biotic variables: A) “upwelling”, B) “non-upwelling”, and C) “warm-acid” conditions. Nodes A and B represented typical features within the upwelling phenology, characterized by the transition from low temperature, oxygen, pH and Chl during upwelling to higher levels during non-upwelling conditions. However, well-oxygenated, saline and “warm-acid” node C seemed to be atypical for local climatology, suggesting the occurrence of a low frequency oceanographic perturbation. Multivariate (LDA and ANCOVA) analyses revealed upwelling through temperature, oxygen and pH were the main factors affecting variations in adult size and EP, and highlighted growth rates were significantly lower under node C. Likely buffering upwelling pH-reductions, phytoplankton biomass maintained copepod reproduction despite prevailing low temperature, oxygen and pH levels in the upwelling setting. Helping to better explain why this species is among the most recurrent ones in these variable yet productive upwelling areas, current findings also provide opportune cues on plankton responses under warm-acid conditions, which are expected to occur in productive EBUS as a consequence of climate perturbations.

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<![CDATA[Sexual system, reproductive cycle and embryonic development of the red-striped shrimp Lysmata vittata, an invader in the western Atlantic Ocean]]> https://www.researchpad.co/article/5c478c82d5eed0c484bd2c2a

Several decapod crustaceans are invaders, but little is known about the biological characteristics that potentiate the success of these decapods in invaded ecosystems. Here, we evaluate and describe some aspects of the reproductive biology and development of Lysmata vittata, an invasive shrimp species in the Atlantic Ocean. In addition, we intend to provide important insights into the biology of invasion by comparing the reproductive traits of this shrimp with some of the predictions about aquatic invasive species. We used experimental and laboratory observations to evaluate the functionality of protandric simultaneous hermaphroditism (PSH), the macro and microscopic development of the ovarian portion of the ovotestes, the reproductive cycle, and the embryonic development of L. vittata. We confirm the functionality of PSH in L. vittata. This shrimp has a rapid reproductive cycle; the ovarian portion of the ovotestes develops (mean ± SD) 6.28 ± 1.61 days after spawning. Embryonic development also occurs over a short time, with a mean (± SD) of 8.37 ± 0.85 days. The larvae hatch without macroscopically visible yolk reserves. Our study provides evidence that the invasive shrimp L. vittata has reproductive and embryonic developmental characteristics (i.e., short generation time and high reproductive capacity) that may be favorable to the establishment of populations during invasive processes.

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<![CDATA[Characterization of longitudinal canal tissue in the acorn barnacle Amphibalanus amphitrite]]> https://www.researchpad.co/article/5c1813bed5eed0c484775b26

The morphology and composition of tissue located within parietal shell canals of the barnacle Amphibalanus amphitrite are described. Longitudinal canal tissue nearly spans the length of side shell plates, terminating near the leading edge of the specimen basis in proximity to female reproductive tissue located throughout the peripheral sub-mantle region, i.e. mantle parenchyma. Microscopic examination of stained longitudinal canal sections reveal the presence of cell nuclei as well as an abundance of micron-sized spheroids staining positive for basic residues and lipids. Spheroids with the same staining profile are present extensively in ovarioles, particularly within oocytes which are readily identifiable at various developmental stages. Mass spectrometry analysis of longitudinal canal tissue compared to tissue collected from the mantle parenchyma reveals a nearly 50% overlap of the protein profile with the greatest number of sequence matches to vitellogenin, a glycolipoprotein playing a key role in vitellogenesis–yolk formation in developing oocytes. The morphological similarity and proximity to female reproductive tissue, combined with mass spectrometry of the two tissues, provides compelling evidence that one of several possible functions of longitudinal canal tissue is supporting the female reproductive system of A. amphitrite, thus expanding the understanding of the growth and development of this sessile marine organism.

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<![CDATA[Individual and combined effects of low dissolved oxygen and low pH on survival of early stage larval blue crabs, Callinectes sapidus]]> https://www.researchpad.co/article/5c141eded5eed0c484d289a2

A large number of coastal ecosystems globally are subjected to concurrent hypoxic and acidified conditions that will likely intensify and expand with continued climate change. In temperate regions, the spawning of many important organisms including the Atlantic blue crab Callinectes sapidus occurs during the summer months when the severity of coastal hypoxia and acidification is the greatest. While the blue crab earliest larval stage can be exposed to co-occurring hypoxia and acidification observed in many coastal ecosystems, the effects of these concurrent stressors on larval blue crab survival is unknown. This study investigated the individual and combined consequences of low dissolved oxygen (DO) and low pH on blue crab larvae survival through a series of short-term experiments. During 14-day experiments with moderately hypoxic conditions (117–127 μM O2 or 3.74–4.06 mg L-1) and acidified conditions (pH on total scale of 7.16–7.33), low DO and low pH individually and significantly reduced larval survival by 60% and 49%, respectively, with the combination of stressors reducing survival by 87% compared to the control treatment (210–269 μM O2 or 6.72–8.61 mg L-1, 7.91–7.94 DO and pH, respectively). During 4-day experiments with lower DO levels (68–83 μM O2 or 2.18–2.62 mg L-1) and comparable pH levels of 7.29–7.39, low DO individually reduced survival by >90% compared to the control (261–267 μM O2 or 8.35–8.54 mg L-1, 7.92–7.97 DO and pH, respectively), whereas low pH had no effect and there was no interaction between stressors. Over a 4-day period, the DO threshold at which 50% of the larval blue crab population died (LC50) was 121 μM O2 (3.86 mgL-1). In 14-day experiments, the DO and pH effects were additive, yielding survival rates lower than the individual treatments, and significantly correlated with DO and pH concentrations. Collectively, these findings indicate that blue crab sensitivity to both low DO and low pH are acute within the larval stage, depend on the intensity and duration of exposure, and leads to mortality, thereby potentially contributing to the interannual variability and possible regional declines of this fishery.

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<![CDATA[What are the sympatric mechanisms for three species of terrestrial hermit crab (Coenobita rugosus, C. brevimanus, and C. cavipes) in coastal forests?]]> https://www.researchpad.co/article/5c1ab82cd5eed0c484026fe2

Terrestrial hermit crabs play a significant role in coastal ecology. For example, as seed dispersers and debris scavengers in coastal forests, they accelerate the decomposition of organic substances. In the Indo-Pacific Ocean, Coenobita rugosus, C. brevimanus, and C. cavipes are the three most common species of terrestrial hermit crab. Because the mechanisms that contribute to the sympatry of these three species of crab have not been identified, this study investigated the three most likely explanations: niche differences, competition, and predation. The results showed that the three species displayed niche differences in terms of seasonal activity, habitat, utilization of shells, and food preference, suggesting that competition for resources is avoided. The habitat of terrestrial hermit crabs in Taiwan is closely associated with that of humans. Our study helps improve our understanding of the ecology of terrestrial hermit crabs and their conservation.

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<![CDATA[Analysis of the transcriptome data in Litopenaeus vannamei reveals the immune basis and predicts the hub regulation-genes in response to high-pH stress]]> https://www.researchpad.co/article/5c117b33d5eed0c4846983c7

Soil salinization erodes the farmlands and poses a serious threat to human life, reuse of the saline-alkali lands as cultivated resources becomes increasingly prominent. Pacific white shrimp (Litopenaeus vannamei) is an important farmed aquatic species for the development and utilization of the saline-alkali areas. However, little is known about the adaptation mechanism of this species in terms of high-pH stress. In the present study, a transcriptome analysis on the gill tissues of L. vannamei in response to high-pH stress (pH 9.3 ± 0.1) was conducted. After analyzing, the cyclic nucleotide gated channel-Ca2+ (CNGC-Ca2+) and patched 1 (Ptc1) were detected as the majority annotated components in the cAMP signaling pathway (KO04024), indicating that the CNGC-Ca2+ and Ptc1 might be the candidate components for transducing and maintaining the high-pH stress signals, respectively. The immunoglobulin superfamily (IgSF), heat shock protein (HSP), glutathione s-transferase (GST), prophenoloxidase/phenoloxidase (proPO/PO), superoxide dismutase (SOD), anti-lipopolysaccharide factor (ALF) and lipoprotein were discovered as the major transcribed immune factors in response to high-pH stress. To further detect hub regulation-genes, protein-protein interaction (PPI) networks were constructed; the genes/proteins “Polymerase (RNA) II (DNA directed) polypeptide A” (POLR2A), “Histone acetyltransferase p300” (EP300) and “Heat shock 70kDa protein 8” (HSPA8) were suggested as the top three hub regulation-genes in response to acute high-pH stress; the genes/proteins “Heat shock 70kDa protein 4” (HSPA4), “FBJ murine osteosarcoma viral oncogene homolog” (FOS) and “Nucleoporin 54kDa” (NUP54) were proposed as the top three hub regulation-genes involved in adapting endurance high-pH stress; the protein-interactions of “EP300-HSPA8” and “HSPA4-NUP54” were detected as the most important biological interactions in response to the high-pH stress; and the HSP70 family genes might play essential roles in the adaptation of the high-pH stress environment in L. vannamei. These findings provide the first insight into the molecular and immune basis of L. vannamei in terms of high-pH environments, and the construction of a PPI network might improve our understanding in revealing the hub regulation-genes in response to abiotic stress in shrimp species and might be beneficial for further studies.

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<![CDATA[Pelagic shrimp play dead in deep oxygen minima]]> https://www.researchpad.co/article/5c08422cd5eed0c484fcc0f1

Pelagic crustaceans are arguably the most abundant group of metazoans on Earth, yet little is known about their natural behavior. The deep pelagic shrimp Hymenopenaeus doris is a common decapod that thrives in low oxygen layers of the eastern Pacific Ocean. When first observed in situ using a remotely operated vehicle, most specimens of H. doris appeared dead due to inactivity and inverted orientation. Closer inspection revealed that these animals were utilizing small, subtle shifts in appendage position to control their orientation and sink rate. In this mode, they resembled molted shrimp exoskeletons. We hypothesize that these shrimp may avoid capture by visually-cued predators with this characteristic behavior. The low metabolic rates of H. doris (0.55–0.81 mg O2 kg-1 min-1) are similar to other deep-living shrimp, and also align with their high hypoxia tolerance and reduced activity. We observed similar behavior in another deep pelagic decapod, Petalidium suspiriosum, which transiently inhabited Monterey Canyon, California, during a period of anomalously warm ocean conditions.

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