Carbohydrate components of lipovitellin of the sand crab Emerita asiatica

Evaluation of the Role of Soybean Lecithin, Egg Yolk Lecithin, and Krill Oil in Promoting Ovarian Development in the Female Redclaw Crayfish Cherax quadricarinatus

The optimal supplementation of lipid nutrients in the diet showed crucial physiological functions in gonadal development and maturation in adult female aquatic animals. Four isonitrogenous and isolipidic diets with no extra lecithin supplementation (control), 2% soybean lecithin (SL), egg yolk lecithin (EL), or krill oil (KO) supplementation were formulated for Cherax quadricarinatus (72.32 ± 3.58 g). Ovary development and physiological characteristics of crayfish were evaluated after a 10-week feeding trial. The results indicated that SL, EL, or KO supplementation all significantly increased the gonadosomatic index, especially in the KO group. Crayfish fed the diet with SL showed the highest hepatosomatic index compared with those fed the other experimental diets. KO was more efficient than SL and EL in promoting triacylglycerol and cholesterol deposition in the ovary and hepatopancreas but also showed the lowest concentration of low-density lipoprotein cholesterol in the serum. KO significantly increased yolk granule deposition and accelerated oocyte maturation than other experimental groups. Furthermore, dietary phospholipids significantly enhanced the gonad-stimulating hormone concentration in the ovary and reduced the secretion of gonad-inhibiting hormones in the eyestalk. KO supplementation also significantly improved organic antioxidant capacity. From the ovarian lipidomics results, phosphatidylcholine and phosphatidylethanolamine are two main glycerophospholipids that respond to different dietary phospholipids. Polyunsaturated fatty acids (especially C18:2n-6, C18:3n-3, C20:4n-6, C20:5n-3, and C22:6n-3) were pivotal participants during ovarian development of crayfish regardless of lipid type. Combined with the ovarian transcriptome, the best positive function of KO was due to activated steroid hormone biosynthesis, sphingolipid signaling, retinol metabolism, lipolysis, starch and sucrose metabolism, vitamin digestion and absorption, and pancreatic secretion. As a consequence, dietary supplementation with SL, EL, or KO all improved the ovarian development quality of C. quadricarinatus, especially KO, which was the optimum choice for promoting ovary development in adult female C. quadricarinatus.

N-glycan moieties of the crustacean egg yolk protein and their glycosylation sites

Vitellogenin (Vg) is the precursor of the egg yolk glycoprotein of crustaceans. In the prawn Macrobrachium rosenbergii, Vg is synthesized in the hepatopancreas, secreted to the hemolymph, and taken up by means of receptor-mediated endocytosis into the oocytes. The importance of glycosylation of Vg lies in its putative role in the folding, processing and transport of this protein to the egg yolk and in the fact that the N-glycan moieties could provide a source of carbohydrate during embryogenesis. The present study describes, for the first time, the structure of the glycan moieties and their sites of attachment to the Vg of M. rosenbergii. Bioinformatics analysis revealed seven putative N-glycosylation sites in M. rosenbergii Vg; two of these glycosylation sites are conserved throughout the Vgs of decapod crustaceans from the Pleocyemata suborder (N 159 and N 660). The glycosylation of six putative sites of M. rosenbergii Vg (N 151, N 159, N ,168 N ,614 N 660 and N 2300) was confirmed; three of the confirmed glycosylation sites are localized around the N-terminally conserved N-glycosylation site N 159. From a theoretical three-dimensional structure, these three N-glycosylated sites N 151, N 159, and N 168 were localized on the surface of the Vg consensus sequence. In addition, an uncommon high mannose N-linked oligosaccharide structure with a glucose cap (Glc1Man9GlcNAc2) was characterized in the secreted Vg. These findings thus make a significant contribution to the structural elucidating of the crustacean Vg glycan moieties, which may shed light on their role in protein folding and transport and in recognition between Vg and its target organ, the oocyte.

Isolation and characterization of a heparin with low antithrombin activity from the body of Styela plicata (Chordata-Tunicata). Distinct effects on venous and arterial models of thrombosis

INTRODUCTION

A heparin preparation with low antithrombin activity and different disaccharide composition than mammalian heparin was isolated from the body of the ascidian Styela plicata (Chordata-Tunicata). The disaccharide composition and the effect of the invertebrate glycan on venous and arterial models of thrombosis was investigated.

METHODS AND RESULTS

High performance liquid chromatography of the products formed by a mixture of heparin lyases showed that the ascidian heparin is composed mainly by delta UA(2SO4)-1-->4-beta-d-GlcN(SO4) (47.5%), delta UA(2SO4)-1-->4-beta-d-GlcN(SO4)(6SO4) (38.3%) disaccharides and smaller amounts of the disaccharides delta UA(2SO4)-1-->4-beta-d-GlcN(SO4)(3SO4)(6SO4) (2.8%) and delta UA(2SO4)-1-->4-beta-d-GlcN(SO4)(3SO4) (8.0%). The invertebrate heparin has an aPTT activity of 18 IU/mg and an antithrombin-mediated antithrombin and anti-factor Xa activities 10-fold lower than that of mammalian heparin. In a venous model of thrombosis in the vena cava, S. plicata heparin inhibits only 80% of thrombosis at a dose 10-fold higher than that of the mammalian heparin that inhibits 100% of thrombosis. However, in an arterio-shunt model of arterial thrombosis, both S. plicata and mammalian heparin possess equivalent antithrombotic activities. It is also shown that at equivalent doses, ascidian heparin has a lower bleeding effect than mammalian heparin.

CONCLUSION

The antithrombin-mediated anticoagulant activity of heparin polymers is not directly related to antithrombotic potency in the arterio-venous shunt. The results of the present work suggest that heparin preparations obtained from the body of S. plicata may have a safer therapeutic action in the treatment of arterial thrombosis than mammalian heparin.

The Hemolymph of the Ascidian Styela plicata (Chordata-Tunicata) Contains Heparin inside Basophil-like Cells and a Unique Sulfated Galactoglucan in the Plasma

The hemolymph of ascidians (Chordata-Tunicata) contains different types of hemocytes embedded in a liquid plasma. In the present study, heparin and a sulfated heteropolysaccharide were purified from the hemolymph of the ascidian Styela plicata. The heteropolysaccharide occurs free in the plasma, is composed of glucose ( approximately 60%) and galactose ( approximately 40%), and is highly sulfated. Heparin, on the other hand, occurs in the hemocytes, and high performance liquid chromatography of the products formed by degradation with specific lyases revealed that it is composed mainly by the disaccharides DeltaUA(2SO(4))-1-->4-beta-d-GlcN(SO(4)) (39.7%) and DeltaUA(2SO(4))-1-->4-beta-d-GlcN(SO(4))(6SO(4)) (38.2%). Small amounts of the 3-O-sulfated disaccharides DeltaUA(2SO(4))-1-->4-beta-d-GlcN(SO(4))(3SO(4)) (9.8%) and DeltaUA(2SO(4))-1-->4-beta-d-GlcN(SO(4))(3SO(4))(6SO(4)) (3.8%) were also detected. These 3-O-sulfated disaccharides were demonstrated to be essential for the binding of the hemocyte heparin to antithrombin III. Electron microscopy techniques were used to characterize the ultrastructure of the hemocytes and to localize heparin and histamine in these cells. At least five cell types were recognized and classified as univacuolated and multivacuolated cells, amebocytes, hemoblasts, and granulocytes. Immunocytochemistry showed that heparin and histamine co-localize in intracellular granules of only one type of hemocyte, the granulocyte. These results show for the first time that in ascidians, a sulfated galactoglucan circulates free in the plasma, and heparin occurs as an intracellular product of a circulating basophil-like cell.

Characterization of the major egg glycolipoproteins from the perivitellin fluid of the apple snail Pomacea canaliculata

Ovorubin and PV2 are the major lipoglycocarotenoproteins present in the perivitellus of the freshwater snail eggs of Pomacea canaliculata, a rapidly expanding rice field pest. We have previously characterized these two particles regarding their lipid and protein compositions, their synthesis and tissular distribution, and their contributions of energy and structural precursors for the developing embryo. In the present study, we have characterized the glycosidic moieties associated to these perivitellines. Both proteins were isolated from egg homogenates by ultracentrifugation, and high performance liquid chromatography (HPLC) using anionic exchange and size exclusion columns. Total carbohydrates accounted for 17.8% and 2.5% (w/w) of the apparent molecular mass of ovorubin and PV2, respectively. Analysis by size exclusion chromatography showed that the amount of O-linked oligosaccharides is higher than that of the N-linked species (59% and 67% w/w of total carbohydrates of ovorubin and PV2, respectively). Glycosylation patterns were determined by a set of biotinilated lectins onto blotted purified proteins. Lectin affinities confirmed the presence of aspargine-linked carbohydrates, probably of hybrid and high mannose types. Jacaline affinity suggested the presence of O-linked residues derived from the T-antigen. Total carbohydrate composition determined by gas liquid chromatography (GLC) showed that mannose was the major monosaccharide in both perivitellins followed by GlcNAc and Gal in ovorubin, and Gal and GlcNAc in PV2. Only one fatty acid (22:1 n-9) accounted for 46% and 56% of the fatty acids present in ovorubin and PV2, respectively. Carbohydrate role on these reserve proteins during embryogenesis of the apple snail is discussed.

Breeding biology of the intertidal sand crab, Emerita (Decapoda: Anomura)

Emerita is a burrowing mole crab or sand crab, adapted to life in wave-washed sandy beaches of temperate and tropical seas. The reproductive biology of this anomuran crab presents several peculiarities, all contributing to its adaptation to this harsh environmental niche. We discuss the following aspects: 1) sex ratio and size at sexual maturity, 2) neoteny and protandric hermaphroditism, 3) mating behaviour and sperm transfer strategy, 4) synchronisation of moulting and reproduction, 5) environmental impact on reproductive cycle and egg production, 6) biochemistry of yolk utilisation and energetics, 7) larval development, dispersal and settlement and 8) the value of Emerita as indicator species. These aspects are discussed in the light of the life history pattern, comprising a sedentary adult and pelagic larval phases. The successful colonisation of the physically challenging habitat of the sandy beach by Emerita is attributable largely to reproductive strategy and the larval developmental and recruitment pattern. Sensitivity to changing environmental conditions, including pollution, make this intertidal crab an indicator species for monitoring anthropogenic impact.

Vitellogenin precursors in the liver of the oviparous lizard, Podarcis sicula

In reptiles, as in the other oviparous vertebrates, vitellogenin (VTG) synthesis is stimulated in the liver by ovarian estrogens. In this article, the presence of VTG precursors was detected in liver subcellular fractions of the oviparous lizard, Podarcis sicula, in the reproductive period. The rough endoplasmic reticulum (RER) and the smooth microsomal fraction (SMF), which includes smooth endoplasmic reticulum and Golgi complex, were separated by means of two different sucrose gradients. The successful separation was controlled at the electron microscope. The contents of the different compartments were extracted by means of n-octyl-beta-D-glucopiranoside detergent and subjected to SDS-PAGE. Western Blotting with homologous anti/VTG antibody revealed two immunoreactive proteins of about 84 and 70 kDa in the RER, and four proteins of about 180, 150, 60, 50 kDa in the SMF; all these proteins appeared phosphorylated and glycosylated. The differences in the molecular weight of these VTG precursors are discussed.

Endocrine-mediated effects of UV-A irradiation on grass shrimp (Palaemonetes pugio) reproduction

Although much is known regarding photoperiodic effects on crustacean egg production, the effects of ultraviolet (UV) light on reproduction has not been investigated. Likewise, little is known concerning the interaction between UV and xenobiotic exposure on crustacean reproductive cycles. In this study, male and female grass shrimp, Palaemonetes pugio, were exposed to sublethal concentrations of endosulfan (200 ng/l and 400 ng/l ES) under both white fluorescent (WF) and UV-A (315-400 nm) light conditions for 50 days in laboratory bioassays. Female endocrine (vitellogenin, ecdysteroids, and cholesterol), reproductive (percent gravid, clutch size), and embryo (days to hatch, hatching success, and hatching survival) responses were assessed. UV-exposure alone caused a significant (>4-fold) increase in total Palaemonetes pugio female egg production over the course of 50 days. Exposure to ES and UV significantly lowered the percentage of gravid females relative to UV controls, whereas ES-exposed shrimp under WF lighting did not exhibit these trends. Although higher vitellogenin concentrations and lower ecdysteroid titers were correlated with increased female egg production, cholesterol titers only exhibited a dose-dependent change when exposed to ES. Embryos from females exposed to UV had significantly lower ecdysteroid titers and shorter hatching times but there were no differences in embryo vitellogenin concentrations, hatching success, or hatching survival. These results indicate that UV-A exposure has a pronounced effect on grass shrimp (Palaemonetes pugio) reproduction and is likely mediated through 5-hydroxytrptamine (5-HT)-related neuroendocrine pathways. The implications for decapod aquaculture and evaluating chronic contaminant effects are discussed.