Search

The brown shrimp Crangon crangon is an opportunistic feeder that is widely distributed in the Atlantic Ocean. It has a large pray spectrum and uses ambush tactics while hunting. To explore the possibility of memory and learning in this species, we attempted to condition specimens to a light stimulus using food (Mytilus edulis) as a reward. After starving the specimens for 32 hours prior to the experiment, several conditioning rounds (20 s light stimulus followed by 60 s of feeding) were absolved on four consecutive days. After conducting short-term experiments with four replicates as well as a long-term experiment (same group for all four trial days) we could not document a successful conditioning with the chosen experiment set up as there were no significant trends in the development of the specimens‘ behavior. We accredit the lack of conditioning mainly to unfavorable management of holding conditions, feeding management and stimulus application but cannot exclude the possibility of memory or learning in the brown shrimp Crangon crangon.

In this study, a microcosm experiment was conducted for 30 days to assess the impact of the presence of juvenile gray shrimp Crangon crangon on meiofauna. The results suggested that juvenile shrimp had a significant negative impact on the abundance of nematodes and copepods, but no effect on polychaetes. Moreover, nematodes showed a significant decline in individual weight. The collected nematodes were taxonomically identified and assigned to five functional traits: shapes of the tail and amphid, life history, feeding types, and adult length. The nematode traits were affected by the number of shrimp introduced, and descriptors followed normal or inversed bell-shaped curves. When no shrimp were present, the nematofauna had a higher species richness compared with treatments of 4, 8, and 12 shrimp. Bell-shaped curve patterns were common in relation to the two phases of feeding for C. crangon. During the first phase, C. crangon consumed the nematode species Oncholaimus campylocercoides; thereafter, shrimp fed mostly on the nematode Anticoma eberthi and copepods.

Globally, neonicotinoid contamination in aquatic environments, including estuarine areas, is a prevailing environmental concern. The estuarine resident marine crustacean sand shrimp Crangon uritai was previously found to have a higher tolerance to neonicotinoids than the marine crustaceans kuruma prawn Penaeus japonicus and mysid Americamysis bahia. Based on these findings, we aimed to explore the mechanisms underlying their differences in insecticide sensitivity. We hypothesized that differences in the structures of their nicotinic acetylcholine receptors (nAChRs) and/or the involvement of a metabolizing enzyme may confer sand shrimp resistance to neonicotinoids. No obvious differences were found in the amino acid residue (position 81) of the loop D region of the nAChR β-subunit among the three crustaceans. A synergistic toxicity bioassay was used to explore candidate metabolizing enzymes, esterase, glutathione S-transferase, and oxygenase. The three species were exposed to two neonicotinoids (acetamiprid and clothianidin) at concentrations equivalent to 1/15–1/10 of 96-h LC50 values and synergists (inhibitors of metabolizing enzyme) or combinations of both. Treatments with the oxygenase inhibitor and the neonicotinoids resulted in increased mortality in sand shrimps but not in kuruma prawns or mysids. Consequently, it was determined that oxygenase may explain the higher resistance of the sand shrimp to neonicotinoid insecticides.

Crangon crangon is economically a very important species. Recently, promising culture attempts have been made, but a major problem is the uncontrollable mortality during the grow-out phase. As of yet, the life cycle of C. crangon is not closed in captivity so wild-caught individuals are used for further rearing. Therefore, it is important to investigate the virome of C. crangon both in wild-caught animals as in cultured animals. In recent years, next-generation-sequencing (NGS) technologies have been very important in the unravelling of the virome of a wide range of environments and matrices, such as soil, sea, potable water, but also of a wide range of animal species. This will be the first report of a virome study in C. crangon using NGS in combination with the NetoVIR protocol. The near complete genomes of 16 novel viruses were described, most of which were rather distantly related to unclassified viruses or viruses belonging to the Picornavirales, Bunyavirales Nudiviridae, Parvoviridae, Flaviviridae, Hepeviridae, Tombusviridae, Narnaviridae, Nodaviridae, Sobemovirus. A difference in virome composition was observed between muscle and hepatopancreatic tissue, suggesting a distinct tissue tropism of several of these viruses. Some differences in the viral composition were noted between the cultured and wild shrimp, which could indicate that in sub-optimal aquaculture conditions some viruses become more abundant. This research showed that a plethora of unknown viruses is present in C. crangon and that more research is needed to determine which virus is potentially dangerous for the culture of C. crangon.

To evaluate the spatio-temporal variations in the community structure and biodiversity of commercially important crustaceans in the Yellow Sea and the northern East China Sea (NECS), the seasonal and regional changes in species composition, biomass structure, biodiversity and distribution of commercially important species were analyzed using bottom trawl survey data during 2014–2015. The results showed that the latitudinal gradient was obvious in species richness, dominant species and biodiversity. The indices of biodiversity increased with the decreasing latitude. When the sampling sites shifted south by one latitudinal degree, Margalef’s richness index (D), Pielou’s evenness index (J′) and Shannon–Wiener diversity index (H′) increased by 0.10, 0.03 and 0.09, respectively. The biomass proportion of the cold-temperate species represented by Crangon affinis declined with the decreasing latitude, and the warm-temperate species represented by Ovalipes punctatus and Portunus trituberculatus increased. Because of the growth regulation of crustaceans and the fishing moratorium, the biomass of commercially important crustaceans in the Yellow Sea and NECS was highest in October and August, respectively. Salinity had a more significant influence on H′ of commercially important crustaceans than other environmental factors (including zooplankton density, sea bottom temperature and water depth). Overall, the results of this study contribute to a better understanding of community dynamics of crustaceans in the Yellow Sea and NECS, and provide evidence to verify the latitudinal gradient theory in biodiversity.

Environmental fluctuations can impose energetic constraints on organisms in terms of food shortage or compensation for metabolic stress. To better understand the biochemical strategies that support adaptive physiological processes in variable environments, we studied the lipid dynamics of the brown shrimp Crangon crangon and the pink shrimp Pandalus montagui by analysing their midgut glands during an annual cycle. Both species have an overlapping distribu- tion range in the southern North Sea, but differ in their habitat preferences, reproductive strate- gies, and life-history traits. C. crangon showed minor total lipid accumulation in their midgut glands, ranging between 14 and 17% of dry mass (DM), dominated by phospholipids. In contrast, P. montagui stored significantly larger amounts of total lipid (47−70% DM, mainly triacylglycer- ols) and showed a distinct seasonal cycle in lipid accumulation with a maximum in summer. Fatty acid trophic markers indicated a wide food spectrum for both species, with higher preferences of P. montagui for microalgae. In C. crangon, feeding preferences were less distinct due the low total lipid levels in the midgut gland. PCA based on fatty acid compositions of both species suggested that C. crangon has a broader dietary spectrum than P. montagui. C. crangon seems to have the capacity to use sufficient energy directly from ingested food to fuel all metabolic requirements, including multiple spawnings, without building up large lipid reserves in the midgut gland. P. montagui, in contrast, relies more on the energy storage function of the midgut gland to over- come food scarcity and to allocate lipids for reproduction.

Cod (Gadus morhua), an important fish species in the Baltic Sea, is the paratenic host for many parasite species, including the zoonotic nematodes, Anisakis sp. and Contracaecum osculatum. We aimed to identify which invertebrate species (found in situ in the fish stomach) are responsible for infection of cod with zoonotic nematodes. We found that Crangon crangon and Gammarus sp., both invertebrate prey species of cod, were infected with Anisakis simplex and C. osculatum, respectively. These host–parasite systems are reported here for the first time, implicating C. crangon and Gammarus sp. as sources of infection of Baltic cod with zoonotic nematodes.

The studies of lakes and estuaries of the central and southern Primorye, conducted in 20052013 in the warm period of the year (MayOctober), allowed to distinguish them in the composition of fish catches and nektobenthos (crabs, prawns and shrimps). In accordance with the data of cluster analysis, 7 biocenotic complexes were identified in the studied reservoirs: lakes in the south of Primorye and the accessory system of the Razdolnaya river, the Gladkaya and Tesnaya rivers; the Ryazanovka, the Barabashevka rivers, the mouth of the Artyomovka river and the central Primorye rivers; the lower course of the river Razdolnaya, the Artyomovka and the Skotovka rivers, the upper part of the Sukhodol estuary; the main part of the Razdolnaya estuary; the Sukhodol estuary and the marine part of the estuaries of the central Primorye. The average specific biomass of hydrobionts in the lakes and estuaries of the southern and central Primorye was 6,4 g/m, or, which is also the same t/km, of which fish is 84,7% by weight. So-iuy mullet or redlip mullet Planiliza haematocheila (1,036) prevailed by biomass, young common rudd Tribolodon spp. (0,904) and Eriocheir japonica (0,606 g/m) followed it. In all seven biocenotic complexes Acanthogobius lactipes, Crangon spp., Gasterosteus nipponicus, Gymnogobius urotaenia, Palaemon spp., Pungitius sinensis, Tribolodon spp. and Tridentiger brevispinis were found. In total, 68 expeditions were carried out (700 catches) in the warm period of the year (MayOctober), 106 taxa of fish and nektobenthos were revealed.

The European brown shrimp, Crangon crangon, is a highly valued commercial species in Europe. These shrimp fisheries are characterized by strong seasonal variations in average landings. Attempts to 'catch and hold' wild adults in land-based rearing systems have been proven to be very difficult, due to inadequate feed, slow growth and high mortality. In this study, we have optimized design and operation procedures of a small-scale static larval rearing system for the culture of C. crangon larvae. Focus was on optimizing larval survival via water temperature, feed selection, feeding regime and density. This is the first report that shows that C. crangon larvae can be reared at high densities of 300 larvae L-1 with high survival of 73.5 (+/- 5.4)% under laboratory conditions. In these systems, larvae can be fed exclusively Artemia nauplii according to a feeding regime which is adjusted based on major moulting events. Addition of microalgae may further increase survival by 10%. The information gathered during this research can be applied to further optimize larval development in either flow-through or recirculation systems.

Tolerance of organisms towards heterogeneous and variable environments is highly related to physiological flexibility. An effective strategy to enhance physiological flexibility is the expression of polymorphic enzymes. This seems to be the case in the brown shrimp Crangon crangon. It shows high reproduction rates, feeds opportunistically on endo- and epibenthic organisms, and is apparently well adapted to variable environmental conditions. Previous electrophoretic studies revealed a high level of polymorphism and no consistent phenotype of digestive enzymes between individuals. In order to understand the underlying biochemical processes, we carried out a transcriptome-based study of digestive enzymes of C. crangon. Detailed sequence analyses of triacylglycerol lipase, phospholipase A2, alpha amylase, chitinase, trypsin and cathepsin L were performed to identify putative isoforms. The number of isoforms, and thus the degree of polymorphism varied among enzymes: lipases and carbohydrases showed higher numbers of isoforms in enzymes that besides their extracellular function also have diverse intracellular functions. Furthermore, cysteine proteinases showed a lower polymorphism than serine proteinases. We suggest that the expression of enzyme isoforms improves the efficiency of C. crangon in gaining energy from different food sources.

Stable isotope analysis has become one of the most widely used techniques in ecological studies. However, there are still uncertainties about the effects of sample preservation and pre-treatment on the ecological interpretation of stable isotope data and especially on Bayesian stable isotope mixing models. Here, Bayesian mixing models were used to study how three different preservation methods (drying, freezing, formalin) and two pre-treatments (acidification, lipid removal) affect the estimation of the utilized organic matter sources for two benthic invertebrate species (Limecola balthica, Crangon crangon) collected in the Baltic Sea. Furthermore, commonly used mathematical lipid normalization and formalin correction were applied to check if they were able to adjust the model results correctly. Preservation effects were strong on model outcomes for frozen as well as formalin preserved L. balthica samples, but not for C. crangon. Pre-treatment effects varied with species and preservation method and neither lipid normalization nor mathematical formalin correction consistently resulted in the desired model outcomes. Our analysis highlights that particularly small, not significant changes in stable isotope ratios introduced by different preservation and pre-treatments display a so far unrecognized source of error in stable isotope mixing models. We conclude that mathematical correction of benthic invertebrate stable isotopes data should be avoided for Bayesian mixing models and that previously unaddressed effects of sample preservation (especially those arising from preservation by freezing) have potentially biased our understanding of the utilization of organic matter in aquatic food webs.

The critical thermal maximum (CTMAX) is the temperature at which animals exhibit loss of motor response because of a temperature-induced collapse of vital physiological systems. A central mechanism hypothesised to underlie the CTMAX of water-breathing ectotherms is insufficient tissue oxygen supply for vital maintenance functions because of a temperature-induced collapse of the cardiorespiratory system. The CTMAX of species conforming to this hypothesis should decrease with declining water oxygen tension (PO2) because they have oxygen-dependent upper thermal limits. However, recent studies have identified a number of fishes and crustaceans with oxygen-independent upper thermal limits, their CTMAX unchanged in progressive aquatic hypoxia. The previous studies, which were performed separately on cold-water, temperate and tropical species, suggest the oxygen-dependence of upper thermal limits and the acute thermal sensitivity of the cardiorespiratory system increases with decreasing habitat temperature. Here we directly test this hypothesis by assessing the oxygen-dependence of CTMAX in the polar Antarctic krill (Euphausia superba), as well as the temperate Baltic prawn (Palaemon adspersus) and brown shrimp (Crangon crangon). We found that P. adspersus and C. crangon maintain CTMAX in progressive hypoxia down to 40 mmHg, and that only E. superba have oxygen-dependent upper thermal limits at normoxia. In E. superba, the observed decline in CTMAX with water PO2 is further supported by heart-rate measurements showing a plateauing, and subsequent decline and collapse of heart performance at CTMAX. Our results support the hypothesis that the oxygen-dependence of upper thermal limits in water-breathing ectotherms and the acute thermal sensitivity of their cardiorespiratory system increases with decreasing habitat temperature.

The brown shrimpCrangon crangonis a key component of the North Atlantic coastal food web and an important target species for the fishery economy. As the brown shrimp contains large amounts of protein and essential fatty acids, its consumption makes it a beneficial choice for humans. Commercially harvested crustaceans likeC. crangonare frequently affected by bacterial shell disease, with necrotizing erosions and ulcerations of the cuticle. To determine whether shell disease influences the nutritional value ofC. crangon, total protein and lipid contents, as well as fatty acid compositions of muscle tissue and hepatopancreas, together with the hepatosomatic index, were examined in healthy and affected individuals. The biochemical composition of the tissues did not differ significantly between the 2 groups. Also, the hepatosomatic index, as an indicator of energy reserves in shrimps, was similar between healthy and affected animals. Our results indicate that the nutritional value ofC. crangonis not affected by shell disease, as long as it remains superficial as in the present study.

Stable isotope analysis has become one of the most widely used techniques in ecology. However, uncertainties about the effects of sample preservation and pre-treatment on the ecological interpretation of stable isotope data and especially on Bayesian stable isotope mixing models remain. Here, Bayesian mixing models were used to study how three different preservation methods (drying, freezing, formalin) and two pre-treatments (acidification, lipid removal) affect the estimation of diet composition for two benthic invertebrate species (Limecola balthica, Crangon crangon). Furthermore, commonly used mathematical lipid normalization and formalin correction were applied to check if they improve the model results. Preservation effects were strong on model outcomes for frozen as well as formalin preserved L. balthica samples, but not for C. crangon. Pre-treatment effects varied with species and preservation method and neither lipid normalization nor mathematical formalin correction consistently resulted in improved model outcomes. Our analysis highlights that particularly small changes in δ15N introduced by different preservation and pre-treatments display a so far unrecognized source of error in stable isotope studies. We conclude that mathematical correction of stable isotopes data should be avoided for Bayesian mixing models and that previously unaddressed effects of sample preservation (especially those arising from preservation by freezing) have potentially biased our understanding of the utilization of organic matter in aquatic food webs.

The brown shrimp, Crangon crangon, is well adapted to the variable environmental conditions in the southern North Sea. It is very abundant, has high reproduction rates, and holds a key position in coastal ecosystems. This species has very low lipid deposits in the midgut gland, suggesting that the main function of the midgut gland is metabolic turnover rather than energy storage. Based on seasonal gene expression studies and established transcriptome data, we investigated key components of lipid metabolic pathways. Gene expression of triacylglycerol lipase, phospholipase, and fatty acid desaturase were analyzed and compared with that of other digestive enzymes involved in lipid, carbohydrate, and protein catabolism. Our results suggest that gene expression of digestive enzymes involved in lipid metabolism is modulated by the lipid content in the midgut gland and is related to food availability. Brown shrimp seem to be capable of using cellular phospholipids during periods of food paucity but high energetic (lipid) requirements. Two of three isoforms of fatty acid binding proteins (FABPs) from the midgut gland involved in fatty acid transport showed specific mutations of the binding site. We hypothesize that the mutations in FABPs and deficiencies in anabolic pathways limit lipid storage capacities in the midgut gland of C. crangon. In turn, food utilization, including lipid catabolism, has to be efficient to fulfill the energetic requirements of brown shrimp.

Decapod assemblages in Zostera marina beds from two bays adjacent to unvegetated habitats were investigated to assess their influence on decapod assemblages. Thirty-eight decapod species belonging to four taxa were collected using a small beam trawl at four habitat types from two different locations off the coast of Namhae Island, South Korea. Dominant decapod taxon at all habitats was the caridean shrimps, with Eualus leptognathus, Heptacarpus pandaloides, Latreutes anoplonyx, La. Laminirostris, and Palaemon macrodactylus being the most abundant caridean species. Crabs were characterized with the highest biomass, but with moderate species richness and abundance. Penaeoid and sergestoid shrimps only accounted for &lt, 1% of the total decapod abundance. The number of species and their abundance of decapod assemblages varied greatly by habitat type, season, and diel patterns, but not diversity. Species number and abundance peaked in seagrass beds of southern exposed bays during the autumn and were lowest in unvegetated habitats during the summer months. Diel decapod catch rates were higher at night. Dense seagrass vegetation and nighttime supported higher decapod mean densities, but not species richness and diversity. Multivariate analyses revealed that habitat type and season significantly affected the structure of decapod assemblages, but diel patterns had a minor influence. Among decapod species, Pa. macrodactylus and Pugettia quadridens characterized the decapod assemblages in seagrass beds at the northern semi-closed bay, while Telmessus acutidens, Crangon affinis, Cr. hakodatei, Charybdis (Charybdis) japonica, and Portunus sanguinolentus were significantly associated with both vegetated and unvegetated habitats at the southern exposed bay, with the former two species more abundant during the colder season.

Chitin is chemically extracted from crustacean shells whose composition and structure differ from one another. It is reported that mineral acids distort chitin's physiochemical properties compared to organic acids. Investigations on the effectiveness of these acids on chitin isolation from crab and shrimp exoskeleton are carried out. Shell particles were demineralized using acetic acid (CH3COOH) and HCl while NaOH was used for deproteinization. Acetic acid possesses low potency for complete CaCO3 removal from crab shell while it fully demineralizes shrimp shell. With the use of CH3COOH, the biopolymer extracted shows characteristics of chitin but with lower content and physicochemical properties compared to chitin isolated from the shells using HCl. Mineral acid (HCl) will thus isolate chitin from exoskeletons of marine invertebrates irrespective of their shell nature while organic acid (CH3COOH) will be effective for soft shells whose embedded chitin content is more than the mineral content such as shrimp shells.

Quantitative samples of fish, crabs and shrimps from the Razdolnaya estuary are analyzed. The area surveyed in May-September of 1990–2014 includes the internal estuary of this largest river of southern Primorye and its external estuary — the top of the Amur Bay with the depth < 13 m. In total, 478 samples were collected: 244 in the external estuary by trawl and 234 in the internal estuary by fry seine. Distribution density and biomass are calculated using the «areal» method with certain coefficients of catchability (1.0 for fry seine). The upper freshwater layer (salinity 0–5 ‰) was observed in the lower stream of the river till sandy bar, the brackish-water cline was traced at the river bottom from the mouth to the distance 10–15 km upstream. The seawater with salinity > 30 ‰ did not penetrate over sand bar to the river. Species diversity of fish and decapods was presented by 108 taxa (fishes — 88, decapods — 20) belonged to 43 families, among them 84 species were caught in the Amur Bay and 41 species in the Razdolnaya, but no more than 67 species were caught in the Amur Bay only and 24 species — in the Razdolnaya only, other 17 species were found in both external and internal estuaries (Acanthogobius flavimanus, Acanthogobius lactipes, Crangon septemspinosa, Crangon spp., Eriocheir japonica, Hypomesus nipponensis, Giporhamphus sajori, Konosirus punctatus, Liopsetta pinnifasciata, Oncorhynchus masou masou, Palaemon sp., Pholis nebulosa, Planiliza haematocheila, Pugettia quadridens, Salangichthys microdon, Syngnathus schlegeli and Tribolodon spp.). Total biomass was higher (9.1 g/m2 ) in the external estuary than in the internal estuary (6.7 g/m2 ) with the mean value 9.0 g/m2 . It was almost uniform over the internal estuary with only slight increasing on the distance about 5 km from the mouth. Simpson index of dominance increases from external to internal estuary but decreases in the river in the order: 0.127 at Peschany Peninsula — 0.168 in the northwestern Amur Bay — from 0.193 to 0.252 in the internal estuary — 0.164 in the river. Six clusters with similar species composition are defined, they change in direction from the sea to the river in the following order of the dominant species: L. pinnifasciata in the sea — prawns gen. Palaemon at the bar (upper part of the external estuary) — P. haematocheila at the river mouth (lower part of the internal estuary) — P. haematocheila and E. japonica in the main part of the internal estuary — Acanthorhodeus chankaensis and Gobio macrocephalus (with the highest biomass up to 22 g/m2 ) in the minor adjoining river stream — G. macrocephalus in the upper part of the internal estuary.

Crustacean decapod assemblages were surveyed inZostera marinabeds adjacent to tidal flats (ET) and rocky shore (ER), and in unvegetated habitats (UV). Decapod samples were collected monthly throughout 2002 using a small beam trawl from northern Jinhae Bay, Korea. Water temperature, salinity, eelgrass biomass, sediment composition and organic matter were also monitored to assess any correlation between environmental variables and decapod fauna. A total of 31 decapod species belonging to five taxa (three prawns, 13 caridean shrimps, one hermit crab, one mud shrimp and 13 crabs) were collected at three different habitats. To assess variations in decapod assemblages in relation to habitat type and season, various multivariate analyses were used. The dominant caridean shrimps werePalaemon macrodactylus, Alpheus digitalisandCrangon uritai,and the dominant crabs wereCharybdis japonica, Hemigrapsus penicillatusandCharybdis bimaculata. The number, abundance and diversity of decapod species varied greatly with habitat type and season, peaking in eelgrass beds and during spring, and showing the lowest catch rate in unvegetated habitat and during winter months. The nMDS ordination and multivariate analyses revealed that habitat type and season were determinant factors affecting the structure of decapod assemblages. Seasonal shifts in the abundance of decapods corresponded with changes in eelgrass biomass and loss on ignition (LOI), but not with water temperature or salinity.

The prevalence of black spot shell disease is increasing among marine crustaceans worldwide. Rising seawater temperatures – often stressful for ectothermic species – are assumed to enhance the occurrence of shell disease. In the North Sea > 50% of local populations of the brown shrimp (Crangon crangon) are affected by the disease. While fisheries are suffering because diseased crustaceans are barely merchantable, the impact of shell disease on life history traits of crustaceans is little understood. To determine the role of temperature on the development of black spots and its implications for survival and physiology in the brown shrimp, a prolonged (3 months) thermal stress experiment was performed. We measured the increment of shell disease and the effect of molting in shrimps kept at control (15 °C = equivalent to the seafloor temperature in the North Sea during sampling) and increased temperature (20 °C = according to predictions for the end of the century). The resting metabolic rate was analyzed to determine the physiological state of diseased compared to non-diseased animals. In the present study, the warmer temperature in the range of 20 °C did not increase the spot size of shell disease and no differences were observed between the two temperatures. The process of molting thereby seemed to diminish and in most of the cases even completely remove the signs of shell disease. At 15 °C but not at 20 °C, metabolic rate was reduced in diseased in contrast to healthy individuals. This study showed that shell disease might lead to a higher mortality rate and an impairment of the physiological state in C. crangon.

The restrictions and the concerted action of the global ban on the use and presence of tributyltin (TBT) in marine applications to protect ecosystems in the marine environment in 2008 was mainly based on the economic impact on shellfish industries and the dramatic extinction of local mollusk populations in the past. In contrast to the vast datasets on effects on mollusks, the knowledge on impacts on species from other taxa remained in the uncertain until almost two decades ago. The assumption on a long-term TBT-mediated pernicious metabolic bottom-up regulation of the crustacean Crangon crangon population was provoked by the outcome of an EU-project 'Sources, Consumer Exposure and Risks of Organotin Contamination in Seafood.' This study reported high TBT body burdens in C. crangon in 2003, at the start of the transition period to the global ban. Experimental research on the TBT impact in C. crangon focused on agonistic interference with natural ecdysteroid hormones at the metabolic pathways regulating growth and reproduction and the biogeochemical distribution of the chemical. In this paper, metabolic, topical and population-relevant biological endpoints in C. crangon and other crustaceans are evaluated in relation to the temporal and spatial trends on TBT's occurrence and distribution in the field during and after the introduction of the tributyltin restrictions and endocrine-related incidents. Arguments are forwarded to relate the German Bight incident on growth and reproduction failure in the C. crangon population, despite the lack of direct evidence, to the pernicious impact of tributyltin in 1990/91 and previous years. The extreme occurrence of TBT in C. crangon from other parts of the southern North Sea and evidence on the high body burdens as dose metrics of exposure also feeds the suspicion on detrimental impacts in those areas. This paper further demonstrates the complexity of distinguishing and assessing the individual roles of unrelated stressors on a population in an integrated evaluation at the ecosystem level.

The brown shrimp,Crangon crangon, is the most important target of the coastal crustacean fisheries in the German Bight. In order to evaluate the relation between the abundance of ovigerous females and larvae in spring and the recruitment success in autumn, we first analysed the seasonal appearance of ovigerous females and larvae from weekly samples throughout 2012. The spawning season in the German Bight extends over several months comprising multiple unsynchronized spawning events. The minimum shares of ovigerous females appeared in early autumn, and the highest shares in late winter bearing mostly early egg stages. We defined the putative start of the reproductive cycle for November when the frequency of ovigerous females started to increase. There was no distinct separation between winter and summer eggs, but a continuous transition between large eggs spawned in winter (the early spawning season) and batches of smaller eggs in spring and summer. Larval densities peaked in April/May. Consequently, regular annual larval surveys from 2013 to 2016 were scheduled for April/May and extended to six transects covering the inner German Bight. Ovigerous females were most abundant in shallow waters above the 20‐m isobaths, which also explained regional differences in abundance between the regions off North Frisia and East Frisia. No relation was obvious between the number of larvae in spring and recruited stock in autumn. Due to the short lifespan of C. crangon, the combination of various abiotic factors and predator presence seems to be the principal parameters controlling stock size.

This study aimed to evaluate and qualify field-based potential risks of seven neonicotinoid and phenylpyrazole (fipronil) insecticides on aquatic invertebrates, including estuary-resident marine crustaceans. One hundred and ninety-three estuarine water samples, with salinity ranging from 0.5 to 32.7, were collected from four estuarine sites in the Seto Inland Sea of Japan, in 2015–2018 and the insecticide levels were measured. Five neonicotinoid and fipronil insecticides were successfully identified, and their occurrence varied temporally. Marine crustaceans were simultaneously harvested every month from one of the estuarine water sampling sites in 2015–2017. Three predominant crustacean species, kuruma prawn (Penaeus japonicus), sand shrimp (Crangon uritai), and mysid (Neomysis awatschensis), were captured and their seasonal presence was species independent. A 96-h laboratory toxicity study with the insecticides using kuruma prawn, sand shrimp, and a surrogate mysid species (Americamysis bahia) indicated that fipronil exerted the highest toxicity to the three crustaceans. Using both toxicity data and insecticide occurrence in estuarine water (salinity ≥10, n = 169), the potential risks on the three marine crustaceans were quantified by calculating the proportion of mixture toxicity effects (Pmix). The Pmix of seven neonicotinoids on the crustaceans was less than 0.8%, which is likely to be too low to indicate adverse effects caused by the insecticides. However, short temporal detection of fipronil (exclusively in June and July) significantly affected the Pmix, which presented the maximal Pmix values of 21%, 3.4%, and 72% for kuruma prawn, sand shrimp, and mysid, respectively, indicating a significant effect on the organisms. As for estuarine water (salinity

Brown shrimp, Crangon crangon, inhabit highly productive sandy and muddy grounds of the southern North Sea. The stomachs of the shrimp contain variable and often high numbers of sediment grains. The function of sediment grains inside the stomach and the purpose of their ingestion are only poorly understood. We tested in laboratory experiments whether sediment and associated organic material complement the natural food of C. crangon or if sand grains may be used by the shrimp to support trituration and maceration of ingested food. The shrimp showed no notable preference for sediment with natural organic content over sediment with reduced organic content, limited ingestion of sediment upon starvation, and no additional uptake of sand grains after feeding. Instead, C. crangon took up sediment only while feeding on regular food, suggesting that sand grains are not ingested intentionally but rather incidentally as a side effect of hasty gobbling. This conclusion is supported by the highly variable uptake of sand grains among individuals. Under experimental conditions, sand grains from sediments do not seem to have a crucial function in food processing and digestion in brown shrimp.

Both cadmium and arsenic are the important metal/metalloid pollutants in the Bohai Sea. In this work, we sampled the dominant species, shrimp Crangon affinis, from three sites, the Middle of the Bohai Sea (MBS), the Yellow River Estuary (YRE) and the Laizhou Bay (LZB) along the Bohai Sea. The concentrations of metals/metalloids in shrimps C. affinis indicated that the YRE site was polluted by Cd and Pb, while the LZB site was contaminated by As. The metabolic differences between shrimps C. affinis from the reference site (MBS) and metal-pollution sites (YRE and LZB) were characterized using NMR-based metabolomics. Results indicated that the metal pollutions in YRE and LZB induced disturbances in osmotic regulation and energy metabolism via different metabolic pathways. In addition, a combination of alanine and arginine might be the biomarker of Cd contamination, while BCAAs and tyrosine could be the biomarkers of arsenic contamination in C. affinis.

In this study, we investigated the community structure of crustaceans (decapod and stomatopod) inhabiting the sandy mud bottoms of Laizhou Bay (northeastern China) monthly from May 2011 to April 2012. Investigation was stopped from December 2011 to February 2012 because of the extreme weather and sea ice. A total of 205,057 specimens belonging to 31 species (shrimp, 15; crab, 15; and stomatopod, 1) were collected in 148 hauls. From 2011 to 2012, Oratosquilla oratoria was the dominant biomass species (47.80%), followed by Charybdis japonica (15.49%), Alpheus japonicas (12.61%), Portunus trituberculatus (6.46%), and Crangon spp. (4.19%). Crangon spp. was the most dominant species by individual (32.55%). O. oratoria was the most-frequently encountered species (81.76%), followed by Palaemon gravieri (70.95%), C. japonica (65.54%), A. japonicas (62.16%), and P. trituberculatus (54.73%). The biomass density increased from August to September 2011 and decreased from March 2012 to April 2012. The dynamics of the ecological indices evolve in a similar manner, with high values of diversity and evenness and rich species from May to June 2011 and low values from September to October 2011. O. oratoria, C. japonica, and P. trituberculatus differed by biomass data between groups I (samples obtained from September to October 2011) and II (samples in other months). These species contributed more than 70% to the similarity of the crustacean community structure. Furthermore, the subsets of environmental variables that best matched the crustacean-assemblage structure were as follows: water depth (WD) in summer (June to August); sea surface temperature (SST), dissolved oxygen (DO), and WD in autumn (September to November); and DO, salinity, and WD in spring (March to May). The calculated correlation coefficients and significance level were higher in the period of July to August 2011 than in other months. Comparing 2011 to 2012 with 1982 to 1983, the species composition remained stable. However, the dominant species changed significantly. High value and large species, such as F. chinensis, P. trituberculatus, and T. curvirostris, have been replaced by low value and small species (i.e., Crangon spp., P. gravieri, and C. japonica).