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Pokey, a new DNA transposon in Daphnia (cladocera: crustacea).

We report the complete sequence of two representatives of the transposable element, Pokey, isolated from the ribosomal DNA of the cladoceran, Daphnia pulicaria. We describe the general features of this element, which confirms its classification as a DNA transposon. We show that Pokey is similar to piggyBac and, as such, is a member of the TTAA-specific family of elements. Pokey is putatively autonomous, possessing an open reading frame that encodes a putative protein with similarity to piggyBac's transposase, in addition to putative proteins from Drosophila and human LOOPER elements, and several human proteins of unknown function. We show that these proteins all contain amino acid motifs that are perhaps conserved for similar functions. We demonstrate that Pokey is carrying several regions of similarity to Daphnia pulex IGS sequences, likely the result of some sort of recombination event with the host genome. Pokey inserts into a conserved region of the large subunit ribosomal RNA gene known to contain other arthropod elements, suggesting that this location is a hot spot for insertional activity. However, Pokey is unique in that it is the only DNA transposon yet known to insert into this region, as other such insertions are non-LTR retrotransposons. It is now clear that this "ecological niche" has been effectively exploited by both retrotransposons and DNA transposons.

Amino Acid Sequence↗

Highly variable polymorphism of the alpha-amylase gene family in Litopenaeus vannamei (Crustacea Decapoda).

Alpha-amylase from the tropical shrimp Litopenaeus vannamei presents a high degree of polymorphism and at least eight different electromorphs are detected by electrophoresis. Based on nucleotide sequences, three cDNAs have been previously characterized. In this paper we report on the organization and the evolution of corresponding alpha-amylase genes, determined after PCR amplification. Three AMY genes have been characterized, spanning over 3.3 kb and encoding mature proteins of 495 amino acids (aa), which are all expressed in the digestive gland. The existence of nine short introns, ranging from 86 to 454 bp, located at the same positions for each of the different genes, and presenting no similarity between them, is reported. Between 11 and 15% of changes are observed in the coding aa sequences of genes II and III compared to the gene I sequence respectively. One 5' putative promoter sequence has been sequenced and shows no classical TATA box upstream to the coding sequence. Based on the intron size difference, a single PCR (producing the S-R fragments) allows the separation of a partial gene I (750 bp), corresponding to cDNA 20, from the others (650-680 bp). Sequencing different S-R PCR fragments from one shrimp shows at least eight different haplotypes. A complex microsatellite repeat is present in intron 6 of gene II. Using size and sequence differences in this repeated portion, it is possible to characterize two gene subfamilies (IIa and IIb) encoding previously described cDNAs 28 and 37, respectively. For the gene II family, two to four alleles are present in one shrimp corresponding to these two genes. Within the Panama natural population, 35 different alleles are shown at this locus. Regarding alpha-amylase gene structure in the shrimp, many recombinants are present from a set of individuals and constitute an important mechanism of evolution of alpha-amylase function.

Amino Acid Sequence↗

Toxicity of the crude oil water-soluble fraction and kaolin-adsorbed crude oil on Daphnia magna (Crustacea: Anomopoda).

Crude oil is a complex mixture of hydrocarbons entering aquatic environments from accidental or normal marine and transportation activities. Toxicologic crude oil analysis is usually performed on the basis of the water-soluble fraction. However, this yields only a partial estimate of the damage caused by these contaminants because a substantial hydrophobic amount can be adsorbed onto suspended solids (biotic and abiotic), which directly affects filter-feeding species and permits bioaccumulation through trophic relationships. This study determined the acute toxic damage sustained after 48 hours caused by seven types of crude oil from Tabasco, Mexico on the cladoceran Daphnia magna. Comparisons were documented based on the responses of D. magna from application of the water-soluble fraction and exposure to entire crude oil samples adsorbed on kaolin clay. Oil-sorbed kaolin was more toxic than the water-soluble fraction in acute exposure. This confirms that tests of the water-soluble fraction tend to underestimate the toxic damage that can be produced in natural environments. Furthermore, chronic toxicity (21 days) was evaluated for crude oil samples adsorbed on kaolin at sublethal concentrations as established from Application Factors (AF) criteria. Results showed that in most cases, it is impossible to predict safe concentrations on the basis of LC(50) values because samples with lower acute toxicity exercised a greater influence on D. magna reproduction and survival when subjected to chronic exposure.

Adsorption↗

Impact of waterborne copper on the structure of gills and hepatopancreas and its impact on the content of metallothionein in juvenile giant freshwater prawn Macrobrachium rosenbergii (Crustacea: Decapoda).

This study aims to elucidate both the impact of copper on the structure of the gills and hepatopancreas and the induction of metallothionein (MT) during waterborne copper exposure in juvenile Macrobrachium rosenbergii. Structural observations were performed with light microscopy, and the MT titrations were performed with the cadmium saturation assay. The structural changes that occurred in the gills and hepatopancreas appeared to result from copper accumulation, and the degree of damage observed in both tissues was relevant to the elevated waterborne copper concentration. Exposure to copper concentrations ranging from 0.01 mg/L to 0.4 mg/L for 7 days resulted in profound structural changes including the accumulation of hemocytes in the hemocoelic space; swelling and fusion of the lamellae; abnormal gill tips; and hyperplastic, necrotic, and clavate-globate lamellae in the gills. Similarly, hemocytic infiltration in the interstitial sinuses, an increased number of hemocytes, thickening and ruptures of the basal laminae, and necrosis of the tubules were observed in the hepatopancreas. The MT measurements showed no significant differences in MT contents between the control group and the group treated with 0.01 mg/L waterborne copper. The maximum MT content was observed at the level of 0.4 mg/L waterborne copper.

Animals↗

Calcium translocations during the moulting cycle of the semiterrestrial isopod Ligia hawaiiensis (Oniscidea, Crustacea).

Terrestrial isopods moult first the posterior and then the anterior half of the body. During the moulting cycle they retain a significant fraction of cuticular calcium partly by storing it in sternal CaCO(3) deposits. We analysed the calcium content in whole Ligia hawaiiensis and the calcium distribution between the posterior, the anterior ventral, and the anterior dorsal cuticle during four stages of the moulting cycle. The results indicate that: (1) overall, about 80% of the calcium is retained and 20% is lost with the exuviae, (2) in premoult 68% of the calcium in the posterior cuticle is resorbed (23% moved to the anterior ventral cuticle, 17% to the anterior dorsal cuticle, and the remaining 28% to internal tissues), (3) after the posterior moult 83% of the calcium in the anterior cuticle is shifted to the posterior cuticle and possibly to internal storage sites, (4) following the anterior moult up to 54% of the calcium in the posterior cuticle is resorbed and used to mineralise the new anterior cuticle. (45)Ca-uptake experiments suggest that up to 80% of calcium lost with the anterior exuviae may be regained after its ingestion. Whole body calcium of Ligia hawaiiensis is only 0.7 times that of the fully terrestrial isopods. These terrestrial species can retain only 48% of whole body calcium, suggesting that the amount of calcium that can be retained by shifting it between the anterior and posterior integument is limited. We propose that fully terrestrial Oniscidea rely to a larger degree on other calcium sources like internal stores and uptake from the ingested exuviae.

Animals↗

Enzymatic, analytical and structural aspects of electron-dense granules in cells of Ucides cordatus (Crustacea, Decapoda) hepatopancreas.

Electron-dense granules (EDGs) are singular structures found in the tissues of several vertebrate and invertebrate organisms. Two types of EDGs were observed in hepatopancreatic cells of the crab Ucides cordatus: (1) a non-mineralized EDG, found mainly inside vacuoles, which reacted positively to acid phosphatase and D-amino acid oxidase, possibly formed by degradation of lipid membranes, and (2) a mineralized EDG surrounded by endoplasmic reticulum membranes that gave a positive reaction for glucose-6-phosphatase. In this study we show the fine structure and composition of the mineralized EDGs using cytochemistry, analytical transmission electron microscopy and field-emission scanning electron microscopy. They are formed of microvesicle-like structures that are arranged in concentric spherical layers in the most mineralized portions of the granule. Analytical microscopy of mineralized EDGs indicated that they are composed of amorphous calcium-magnesium phosphate. Isolated EDGs treated with NaOCl lose several elements, including P, when compared with EDGs treated with deionized water. Removal of the organic matrix by NaOCl induced marked changes in the mineralized EDGs, showing that the organic matrix plays an important role in its elemental composition and structure.

Acid Phosphatase↗

Ontogeny of the antennal glands in the crayfish Astacus leptodactylus (Crustacea, Decapoda): immunolocalization of Na+,K+-ATPase.

The involvement of the antennal urinary glands in the ontogeny of osmoregulatory functions was investigated during the development of Astacus leptodactylus by measurements of hemolymph and urine osmolality in juvenile and adult crayfish and by the immunodetection of the enzyme Na+,K+-ATPase. In stage II juveniles, 1-year-old juveniles, and adults, all of which were maintained in freshwater, urine was significantly hypotonic to hemolymph. In adults, chloride and sodium concentrations were much lower in urine than in hemolymph. During embryonic development, Na+,K+-ATPase was detected by immunocytochemistry in ionocytes lining the tubule and the bladder, at an eye index (EI) of 220-250 microm, and in the labyrinth, at EI 350 microm. In all regions, immunofluorescence was mainly located at the basolateral side of the cells. No immunofluorescence was detected at any stage in the coelomosac. In late embryonic stages (EI 410-440 microm), in stage I juveniles, and in adults, strong positive immunofluorescence was found from the labyrinth up to and including the bladder. These results show that, as early as hatching, juvenile crayfish are able to produce dilute urine hypotonic to hemolymph. This ability originates from the presence of Na+,K+-ATPase in ion-transporting cells located in the labyrinth, the tubule, and the bladder of the antennal glands and constitutes one of the main adaptations of crayfish to freshwater.

Animals↗

Ontogeny of the antennal glands in the crayfish Astacus leptodactylus (Crustacea, Decapoda): anatomical and cell differentiation.

The ontogeny of the antennal glands was studied during the embryonic and post-embryonic development of Astacus leptodactylus. The future glands arising from undifferentiated columnar cells were detectable at the metanauplius stage EI 150 microm (EI: eye index; approximately 440 microm at hatching). The tubule and labyrinth differentiated in embryos at EI 190 microm, and the bladder and coelomosac at EI 250 microm. At EI 350 microm, the tubule lengthened and divided into proximal and distal sub-regions. In later stages, the gland retained the same morpho-anatomy but the differentiation and size of each part increased. The cells of the coelomosac displayed the cytological features of podocytes in late embryonic development at EI 440 microm. Only small apical microvilli and a few mitochondria were observable in the labyrinth cells at EI 250 microm; by EI 440 microm, these cells presented well-shaped apical microvilli, formed bodies, basal infoldings and mitochondria. In the cells of the tubules and bladder, mitochondria and basal infoldings occurred at EI 440 microm and EI 250 microm, respectively. The differentiation of the tubules and bladder cells suggested that they were involved in active transport at EI 440 microm. Following hatching, the differentiation of the cells and the size of the glands increased. The ontogeny of the antennal glands thus starts in early embryos, the specific cellular functional features being differentiated in the various parts of the glands by EI 440 microm. The antennal glands are probably functional just before hatching, i.e., before the juveniles are confronted with the low osmolality of freshwater.

Animals↗

Immunolocalization of Na+,K+-ATPase in the branchial cavity during the early development of the crayfish Astacus leptodactylus (Crustacea, Decapoda).

The ontogeny of osmoregulation was examined in the branchial cavity of embryonic and early post-embryonic stages of the crayfish Astacus leptodactylus maintained in freshwater, at the sub-cellular level through the detection of the sodium-potassium adenosine triphosphatase (Na(+),K(+)-ATPase). The embryonic rate of development was calculated according to the eye index (EI) which was 430-450 microm at hatching. The distribution of the enzyme was identified by immunofluorescence microscopy using a monoclonal antibody IgGalpha5 raised against the avian alpha-subunit of the Na(+),K(+)-ATPase. Immunoreactivity staining, indicating the presence of Na(+), K(+)-ATPase appeared in the gills of late embryos (EI>/=400 microm), i.e. a few days before hatching time, and steadily increased throughout the late embryonic and early post-embryonic development. The appearance of the enzyme correlates with the ability to osmoregulate which also occurs late in the embryonic development at EI 410-420 microm and with tissue differentiation within the gill filaments. These observations indicate that the physiological shift from osmoconforming embryos to hyper-regulating late embryos and post-hatching stages in freshwater must originate partly from the differentiation in the gill epithelia of ionocytes which are the site of ion pumping, as suggested by the location of Na(+),K(+)-ATPase. Only the gills were immunostained and a lack of specific staining was noted in the lamina and the branchiostegites. Therefore, osmoregulation through Na(+)active uptake is likely achieved in embryos at the gill level; all the newly formed gills in embryos function in ion regulation; other parts of the branchial chamber such as the branchiostegites and lamina do not appear to be involved in osmoregulation.

Animals↗

Ultrastructural evidence for transepithelial calcium transport in the anterior sternal epithelium of the terrestrial isopod Porcellio scaber (Crustacea) during the formation and resorption of CaCO3 deposits

Before the molt, terrestrial isopods store large amounts of calcium carbonate between the epithelium and the old cuticle of the first four anterior sternites. In order to test whether the anterior sternal epithelium has specific structural differentiations indicative of transepithelial ion transport, the anterior sternal epithelium and, as a control, the posterior sternal epithelium were studied using electron-microscopical techniques. During the formation of calcium carbonate deposits, the basolateral plasma membrane of the anterior sternal epithelium forms an elaborate interconnected network of interstitial dilations and channels. Numerous osmiophilic granules occur within this basolateral intercellular network during resorption of the calcium carbonate deposits. Electron energy-loss spectroscopy of the osmiophilic granules indicates that they contain calcium. During the resorption of the calcium carbonate deposits, the apical plasma membrane of the anterior sternal epithelium has many subcuticular folds. An interstitial network, osmiophilic granules, and apical, subcuticular folds do not occur in the posterior sternal epithelium. Taken together, these structural features are indicative of transepithelial ion transport and are probably necessary for the formation and resorption of the anterior sternal calcium carbonate deposits.

Journal Article↗

Immunolocalization of Na+,K(+)-ATPase in the organs of the branchial cavity of the European lobster Homarus gammarus (Crustacea, Decapoda).

The localization of Na+,K(+)-ATPase in epithelia of the organs of the branchial cavity of Homarus gammarus exposed to seawater and dilute seawater was examined by immunofluorescence microscopy and immunogold electron microscopy with a monoclonal antibody IgG alpha 5 raised against the avian alpha-subunit of the Na-,K(+)-ATPase. In juveniles held in seawater, fluorescent staining was observed only in the epithelial cells of epipodites. In juveniles held in dilute seawater, heavier immunoreactivity was observed in the epithelial cells of epipodites, and positive immunostaining was also observed along the inner-side epithelial layer of the branchiostegites. No fluorescent staining was observed in the gill epithelia. At the ultrastructural level, the Na+,K(+)-ATPase was localized in the basolateral infolding systems of the epipodite and inner-side branchiostegite epithelia of juveniles held in dilute seawater, mostly along the basal lamina. The expression of Na+,K(+)-ATPase therefore differs within tissues of the branchial cavity and according to the external salinity. These and previous ultrastructural observations suggest that the epipodites, and to a lesser extent the inner-side epithelium of the branchiostegites, are involved in the slight hyper-regulation displayed by lobsters at low salinity. Enhanced Na+,K(+)-ATPase activity and de novo synthesis of Na+,K(+)-ATPase within the epipodite and branchiostegite epithelia may be key points enabling lobsters to adapt to low salinity environments.

Animals↗

High frequency and large number of polymorphic microsatellites in cultured shrimp, Penaeus (Litopenaeus) vannamei [Crustacea:Decapoda].

A total of 1479 recombinant clones were obtained from a Sau3A-digested genomic library of Penaeus (Litopenaeus) vannamei and used for probe hybridization. Of the 251 clones that tested positive to one or more of the probes and were sequenced, 173 (69%) contained 573 simple sequence repeats, or microsatellites, with 3 or more repeats. The frequency of microsatellites with 3, 5, and 10 or more repeats was 1 in 0.94 kb, 1 in 2.78 kb, and 1 in 5.94 kb, respectively. To increase the number of polymorphic markers for mapping, 136 primer sets that flanked microsatellites containing single or multiple motifs with 3 or more repeats were designed and tested. Of the 136 primers, 93 (68.0%) were polymorphic in cultured shrimp, with polymorphism information content (PIC) values ranging from 0.195 to 0.873, and observed heterozygosities ranging from 10% to 100%. These markers are being used along with other markers to construct a linkage map for P. vannamei.

Animals↗

The first internal transcribed spacer (ITS-1) of ribosomal DNA as a molecular marker for phylogenetic and population analyses in crustacea.

The objective of the present study is to explore the feasibility of using the first internal transcribed spacer (ITS-1) of ribosomal DNA as a molecular marker for studying the interspecific and intraspecific genetic variations among crustaceans. We designed primers that could amplify ITS-1 from a majority of taxonomic groups of crustaceans. The gene was found to exhibit a high degree of length polymorphism among different groups, ranging from 182 bp in the barnacle Balanus amphitrite to approximately 820 bp in the spiny lobster Panulirus japonicus. With respect to differences between congeneric species, it was found that the ITS-1 sequences of 3 mitten crabs, Eriocheir sinensis, Eriocheir leptognathus, and Eriocheir formosa, exhibit 5.4% to 16.3% nucleotide divergence, suggesting that ITS-1 is informative for phylogenetic analysis at the species level. Yet there are extensive (0.9%-2.3%) variations within individual E. formosa, so that phylogenetic analyses could be obscured. ITS-1 was found to vary between 2 geographical populations of the shrimp Penaeus japonicus. The variations involved substitutions as well as insertions/deletions between shrimp from Australia and South China Sea. These results show that ITS-1 is highly divergent among different crustaceans and could be an appropriate marker for molecular systematic studies at the species and population levels, although the presence of intragenomic variation needs to be taken into consideration.

Journal Article↗

Behavioral response in the terrestrial isopod Porcellio scaber (Crustacea) offered a choice of uncontaminated and cadmium-contaminated food.

The objective of this study was to find out whether Porcellio scaber discriminates against Cd-contaminated food. The foraging behavior in animals offered uncontaminated and Cd-contaminated food simultaneously was quantified for 48-h employing computer-aided video tracking. To see whether the isopods' selection of less contaminated food could diminish the influence Cd on food consumption, growth, metal assimilation, moulting and mortality, Cd-dosed food (20, 45, 200 and 450 mg kg(-1) dry weight) was offered together with untreated food for 3 weeks. Data from the video tracking experiments revealed that animals visited Cd-dosed food as often as untreated food, but spent much less time near Cd-dosed food. Discrimination against Cd-contaminated food increased with previous experience with contaminated food and/or with increased Cd body burden. In 3 weeks exposure uncontaminated food preference rose with time of exposure and cadmium concentration in food and reached a maximal preference ratio of 65% (untreated food): 35% (Cd-dosed food). The decreased consumption of Cd-dosed food was compensated by the increased consumption of control food. Cadmium body burden increased with time of exposure and cadmium concentration in food consumed, while the influence of Cd on food consumption, growth and moulting was diminished.

Animal Feed↗