New records of decapod crustaceans in the Jurassic of France

Four species of decapod crustaceans from the Middle Jurassic Opalinus Clay (Aalenian) of Northern Switzerland are described. Of these, Mecochirus cf. eckerti is the most common one, while Eryma cf. bedelta, Glyphea sp. and Aeger sp. were present as individuals, or only a few specimens. The preservation of these crustaceans ranges from moderate to excellent, reflecting the favourable taphonomic conditions of the depositional environment. An interesting aspect of the taphocoenosis in the Opalinus Clay is that the decapod crustaceans are by far outnumbered by small peracarid crustaceans (isopods and tanaids). This is interpreted as reflecting the original differences in abundance. Yet this distribution is not frequently encountered in sedimentary sequences where decapods (although rare) are far more common than isopods and tanaids. In rare instances, this reflects the original predominance of decapods, more often it is a consequence of the differential taphonomic behaviour of these two groups. A new model relating the ecology to the taphonomic behaviour of decapod and peracarid crustaceans is proposed. According to this model, decapods dominate in settings that were deposited under extremely dysoxic (peracarids wiped out by seasonal anoxia) as well as under fully oxic conditions (peracarids destroyed by taphonomic processes). Only in muddy dysoxic depositional environments are peracarid crustaceans frequently preserved. In these settings with equal preservation potential of decapods and peracarids, the original composition of the crustacean fauna would show a predominance of peracarid crustaceans. Examples from some well known fossiliferous settings are provided to illustrate the use of the new model.

An Aptian sponge-associated decapod crustacean assemblage from Cal Cassanyes (Catalonia, north-east Iberian Peninsula): Taxonomy and palaeoecological implications

Two components of the crustacean respiratory system — gill ventilation and perfusion — are required to meet the metabolic requirements for gas exchange. All crustaceans possess some means of moving the external medium past their gas exchange surfaces. In primitive forms such as Hutchinsoniella (Cephalocarida) and Branchionecta (Brachiopoda) the paired thoracic appendages are serially similar and by their paired phase-locked movements these appendages facilitate respiration, locomotion and feeding. In some smaller crustaceans an internal circulatory system to transport oxygen may not be necessary because sufficient gas exchange can occur by diffusion. Decapods and other large crustaceans, on the other hand, depend on a dual hydraulic pumping system to effect gas exchange between the external medium and the blood. In decapods the gills are enclosed within branchial chambers, and scaphognathites, modified portions of the 2nd maxillae located anterior to the gills, pump water or air through the gill chambers. The heart with possible assistance from accessory contractile structures, pumps blood throughout the body and internally perfuses the gills. In this paper I will focus on the scaphognathites and heart as pumps and discuss how these two systems are integrated to meet the range of demands placed on them. Other aspects of this topic are soon to be reviewed (McMahon and Wilkens, in press).

The aquaculture of decapod crustaceans is expanding continuously to supply protein source for human consumption. Therefore, intensive research is necessary to improve the quality of the feeds in decapod crustacean farming. Decapod crustaceans are slow feeders, and dietary inclusion of plant proteins reduces their intakes on the feeds. Dietary supplementation of chemoattractants (CA) (to reduce food searching duration) and feeding stimulants (FS) (to stimulate ingestion) is therefore necessary to solve these problems respectively. Amino acids are commonly used as the CA and FS in aquaculture, and the feeding response of aquatic animals to amino acids is species-specific. As the chemosensory systems of decapod crustaceans are complicated, and their feeding responses are different from fish, it is essential to understand which amino acids can function as the CA, FS or both to the targeted farmed species. This review provides an overview on the acceptance of some commercially farmed decapod crustaceans to amino acids. Topics related to the efficiency of amino acids being a CA and FS were discussed, and recommendations on how to present amino acids as a CA and FS efficiently in decapod crustacean farming were also made.

Full-length cDNAs encoding crustacean cardioactive peptide (CCAP) were isolated from several decapod (brachyuran and astacuran) crustaceans: the blue crab Callinectes sapidus, green shore crab Carcinus maenas, European lobster Homarus gamarus and calico crayfish Orconectes immunis. The cDNAs encode open reading frames of 143 (brachyurans) and 139-140 (astacurans) amino acids. Apart from the predicted signal peptides (30-32 amino acids), the conceptually translated precursor codes for a single copy of CCAP and four other peptides that are extremely similar in terms of amino acid sequence within these species, but which clearly show divergence into brachyuran and astacuran groups. Expression patterns of CCAP mRNA and peptide were determined during embryonic development in Carcinus using quantitative RT-PCR and immunohistochemistry with whole-mount confocal microscopy, and showed that significant mRNA expression (at 50% embryonic development) preceded detectable levels of CCAP in the developing central nervous system (CNS; at 70% development). Subsequent CCAP gene expression dramatically increased during the late stages of embryogenesis (80-100%), coincident with developing immunopositive structures. In adult crabs, CCAP gene expression was detected exclusively in the eyestalk, brain and in particular the thoracic ganglia, in accord with the predominance of CCAP-containing cells in this tissue. Measurement of expression patterns of CCAP mRNA in Carcinus and Callinectes thoracic ganglia throughout the moult cycle revealed only modest changes, indicating that previously observed increases in CCAP peptide levels during premoult were not transcriptionally coupled. Severe hypoxic conditions resulted in rapid downregulation of CCAP transcription in the eyestalk, but not the thoracic ganglia in Callinectes, and thermal challenge did not change CCAP mRNA levels. These results offer the first tantalising glimpses of involvement of CCAP in environmental adaptation to extreme, yet biologically relevant stressors, and perhaps suggest that the CCAP-containing neurones in the eyestalk might be involved in adaptation to environmental stressors.

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This chapter discusses general patterns of brooding in decapod crustaceans from aquatic to terrestrial environments, addressing behavioral adaptations as well as costs and benefits. Brooding embryos is a common feature among decapods. However, brooding exhibits a wide range of modes that are highly dependent on the environment. Brooding is less common in marine systems, whereas there is a general pattern of extended brooding with terrestrialization. Exceptions are crabs that have invaded land directly via the seashore, i.e. land crabs that have indirect development like their marine ancestors. During terrestrialization, adaption to environmental stressors like desiccation, UV radiation, temperature variability, mechanical support, and osmolality seemed to generally favor decreasing larval development and increasing duration of brood care. Thus, crustaceans developed more complex brooding mechanisms as adaptive responses to the colonization of land (e.g., osmoregulation of the maternal fluids, marsupial fluid, sealed and specialized marsupium, provision of nutritious material, grooming and cleaning, ventilation of the embryo masses). However, clear brooding behaviors are also observed among several marine species (e.g. grooming and cleaning, oxygen provision). The major efforts to characterize general brooding patterns among decapod crustaceans and describe brooding behaviors were not accompanied by comprehensive studies to understand the costs and the benefits of brooding. Several studies have addressed the positive influence of the mother on embryo development, but the efforts to quantify the impact on embryo survival are still limited. This chapter identifies problems that need further consideration to reach a deeper understanding of the evolution of brooding in decapod crustaceans.

Oyster reefs provide habitat for numerous fish and decapod crustacean species that mediate ecosystem functioning and support vibrant fisheries. Recent focus on the restoration of eastern oyster (Crassostrea virginica) reefs stems from this role as a critical ecosystem engineer. Within the shallow estuaries of the northern Gulf of Mexico (nGoM), the eastern oyster is the dominant reef building organism. This study synthesizes data on fish and decapod crustacean occupancy of oyster reefs across nGoM with the goal of providing management and restoration benchmarks, something that is currently lacking for the region. Relevant data from 23 studies were identified, representing data from all five U.S. nGoM states over the last 28 years. Cumulatively, these studies documented over 120,000 individuals from 115 fish and 41 decapod crustacean species. Densities as high as 2,800 ind m−2 were reported, with individual reef assemblages composed of as many as 52 species. Small, cryptic organisms that occupy interstitial spaces within the reefs, and sampled using trays, were found at an average density of 647 and 20 ind m−2 for decapod crustaceans and fishes, respectively. Both groups of organisms were comprised, on average, of 8 species. Larger-bodied fishes captured adjacent to the reef using gill nets were found at an average density of 6 ind m−2, which came from 23 species. Decapod crustaceans sampled with gill nets had a much lower average density, <1 ind m−2, and only contained 2 species. On average, seines captured the greatest number of fish species (n = 33), which were made up of both facultative residents and transients. These data provide general gear-specific benchmarks, based on values currently found in the region, to assist managers in assessing nekton occupancy of oyster reefs, and assessing trends or changes in status of oyster reef associated nekton support. More explicit reef descriptions (e.g., rugosity, height, area, adjacent habitat) would allow for more precise benchmarks as these factors are important in determining nekton assemblages, and sampling efficiency.

A structural and functional comparison of nematode and crustacean PDH-like sequences

The interactions of three sectors: deteriorated environment, weakening host and pathogen aggression are required to cause a disease outbreak. This paper reviews the existing information about the effects of physiological factors and environmental factors on the immune response in decapod crustaceans, particularly of freshwater prawn Macrobarchium rosenbergii. Emphasis is placed on intrinsic f actors and natural environments like gender, size, molting cycle, feeding rate, circadian rhythm and season. Primary physicochemical changes such as temperature, pH, dissolved oxygen, salinity, and pollutants such as ammonia and copper sulfate are also addressed. Immunological tools commonly used to evaluate immune response are hemocyte counts including THC (total hemocyte count) and DHC (differential hemocyte count), phenoloxidase activity, respiratory burst (release of superoxide anion), phagocytic activity, clearance efficiency (or antibacterial activity), and antimicrobial peptides. As an example, M. rosenbergii reared at high temperature (33-34℃), high pH (9.0-9.5), low pH (4.6-5.0), low DO (1.75-2.75 mg/l), and exposed to ammonia-N (0.55 mg/l) and copper sulfate (0.2 mg/l) experienced a decrease in phenoloxidase activity, leading to susceptibility to Lactococcus garvieae pathogen by reducing its immune ability. The immune responses of other decapod crustaceans under environmental changes and exposure to pollutants are also discussed.

Decapod crustaceans include three main groups and they are Macrura (or shrimps and lobsters), Brachyura (or crabs) and Anomura (i.e. hermit crabs and alikes). Only very limited species of decapod crustaceans, such as coconut crabs and land crabs, live on lands. Most decapod crustaceans have aquatic habitats and with highly diverse morphologies, ecology, and life histories etc. This article gives a general overview on the history of the study of the decapod crustacean fauna in Taiwan.

The aim of this study was to determine the reliability and accuracy of 3 commercially available handheld lactate meters when measuring hemolymph L-lactate in decapod crustaceans. The instruments tested were Accutrend Plus (AP), Lactate Scout (LS), and Lactate Plus (LP), and all models were tested in triplicate and compared with a commonly used enzymatic kit for L-lactate quantification (TB-kit). The Norway lobster Nephrops norwegicus and the European lobster Hommarus gammarus were used as model organisms, with emersion as an invoker of hemolymph L-lactate. Between-method comparisons were investigated by determining correlations (Pearson's r) and concordance (concordance correlation coefficient (CCC) and Bland-Altmand's 95% limit of agreement (95% LOA)) between handheld instruments and TB-kit. Within-instrument variation was tested by calculating the coefficient of variation (CV), and the average absolute deviation from the mean (AD). The within-instrument variation was low for all models (CV, 3.8–6.1%; AD, <0.3 mM), showing high reproducibility of technical replicates. A significant correlation with TB-kit was found for all handheld instruments (AP, r = 0.970; LS, r =; 0.956; LP, r = 0.950). For both AP and LS, there was a moderate and significant concordance with TB-kit (AP, CCC = 0.945; LS, CCC = 0.940). The mean difference from TB-kit was -1.42 mM (95% LOA,-4.50–1.66 mM) for AP and 1.19 mM (95% LOA,-3.13–5.51 mM) for LP. Emersion experiments with the European lobster showed that AP and LS were in line with TB-kit in terms of detecting differences in L-lactate levels between groups of animals. As a result of the high frequency of error readings from LP, this instrument was not considered reliable when measuring L-lactate in decapod crustaceans. In conclusion the handheld instruments AP and LS are found to be reliable instruments when measuring hemolymph L-lactate in decapod crustaceans. Comparison of results from different methods should be avoided, and in cases when accurate absolute measurement of L-lactate is needed, methods allowing for greater accuracy and resolution should be used.

Simple SummaryDecapod crustaceans live in practically all marine, freshwater, and semi-terrestrial habitats on Earth, and exhibit a remarkable variation in their feeding behavior, from filter feeding, grazing, and scavenging to hunting. However, most knowledge about digestive biochemistry in crustaceans has come from studies on a few economically relevant species due to the importance of optimized formulated feeds for aquaculture success. Moreover, most data on α-amylases in decapods derived from studies in herbivore and omnivore species. There are few reviews addressing different aspects of the digestive physiology of decapods, including data on digestive enzymes, but no comprehensive review is available on α-amylases in this group and, in general, information on carnivorous species is often neglected. This review summarizes the information obtained on decapods’ α-amylases and uses recent data from a carnivorous lobster as a connecting thread to compare features of α-amylases from species with different feeding habits, drawing a more comprehensive view of the role of α-amylases across decapods crustaceans.Decapod crustaceans are a very diverse group and have evolved to suit a wide variety of diets. Alpha-amylases enzymes, responsible for starch and glycogen digestion, have been more thoroughly studied in herbivore and omnivore than in carnivorous species. We used information on the α-amylase of a carnivorous lobster as a connecting thread to provide a more comprehensive view of α-amylases across decapods crustaceans. Omnivorous crustaceans such as shrimps, crabs, and crayfish present relatively high amylase activity with respect to carnivorous crustaceans. Yet, contradictory results have been obtained and relatively high activity in some carnivores has been suggested to be a remnant trait from ancestor species. Here, we provided information sustaining that high enzyme sequence and overall architecture conservation do not allow high changes in activity, and that differences among species may be more related to number of genes and isoforms, as well as transcriptional and secretion regulation. However, recent evolutionary analyses revealed that positive selection might have also occurred among distant lineages with feeding habits as a selection force. Some biochemical features of decapod α-amylases can be related with habitat or gut conditions, while less clear patterns are observed for other enzyme properties. Likewise, while molt cycle variations in α-amylase activity are rather similar among species, clear relationships between activity and diet shifts through development cannot be always observed. Regarding the adaptation of α-amylase to diet, juveniles seem to exhibit more flexibility than larvae, and it has been described variation in α-amylase activity or number of isoforms due to the source of carbohydrate and its level in diets, especially in omnivore species. In the carnivorous lobster, however, no influence of the type of carbohydrate could be observed. Moreover, lobsters were not able to fine-regulate α-amylase gene expression in spite of large changes in carbohydrate content of diet, while retaining some capacity to adapt α-amylase activity to very low carbohydrate content in the diets. In this review, we raised arguments for the need of more studies on the α-amylases of less studied decapods groups, including carnivorous species which rely more on dietary protein and lipids, to broaden our view of α-amylase in decapods crustaceans.

Global warming is a challenge to animal health because of the increased environmental temperature, with subsequent induction of immune suppression and increased susceptibility to disease during summer. The Toll-like receptor (TLR) family is an essential pattern recognition receptor (PRR) that initiates the innate immune response by sensing conserved molecular patterns of pathogens. However, research on the TLR gene family in decapod crustaceans has been conducted sporadically, without systematic naming, and the relationship between pathogen immunity adaptation and adaptive evolution of immune-related genes is unclear. In this study, various TLR gene sequences in decapod crustaceans were collected, and the unified name of Fenneropenaeus chinensis was confirmed using sequence alignment. Structural characteristics and evolutionary analyses of TLR genes in decapod crustaceans were performed, and ten FcTLR genes were identified in F. chinensis. Protein domain analysis revealed that FcTLR proteins contain 4–25 LRR domains used to recognize different pathogens. Selection pressure analysis revealed that TLR1 and TLR9 were subjected to positive selection pressure in decapod crustaceans, which may be related to their resistance to environmental changes. Furthermore, the expression of ten TLR genes was detected in F. chinensis following white spot syndrome virus (WSSV) infection. The results demonstrated that FcTLR1, FcTLR7, and FcTLR9 responded positively, which was also consistent with the results of the protein domain and selection pressure analyses. This study provides new insights into the immune response and adaptive evolution of TLRs in decapod crustaceans to prevent environmental damage, such as pathogens and high temperature.

Decapod crustaceans are important components of the fauna of soft-bottom habitats. In this work, the records of decapod crustaceans are provided through the analysis of a large soft-bottom benthic macroinvertebrates dataset of the Central Mediterranean Sea. Decapod crustacean assemblages were collected in the last twenty years by a Van Veen grab in 42 study sites located along the Italian coasts at depths ranging from 1 up to 120 m. The spatial distribution of the crustaceans examined, which include 120 species belonging to 40 families, was investigated according to the biogeographical zones identified in the Italian seas. The spatial distribution of 36 species was updated, comparing the ISPRA decapod crustacean dataset with the most recent Italian checklists. For the species updated, the number of specimens, the year and season of sampling, and environmental data, such as the bathymetric range and habitat details, are provided for each site investigated. Data are discussed and compared with the existing literature, also referring to what is reported in the World Register of Marine Species (WoRMS), with the aim of contributing to the knowledge of the biodiversity of the marine species and supporting the updating of checklists and registers in the Mediterranean Basin.