Calcium regulation in wild populations of a freshwater cartilaginous fish, the lake sturgeon Acipenser fulvescens

Lake sturgeon, Acipenser fulvescens, are one of a few species of cartilaginous fishes that complete their life cycle entirely in freshwater. Sturgeons maintain very low concentrations of circulating calcium (Ca²⁺) compared with other vertebrates, and therefore, face unique challenges in regard to Ca²⁺ regulation, which are likely to be magnified during vitellogenic stages of the reproductive cycle. In the present study, Ca²⁺ concentrations and associated hormones of female and male lake sturgeon were examined in two wild populations, and were related to reproductive stage. In both populations, free, bound and total Ca²⁺ were low, peaking in mid-late vitellogenic females. Internal Ca²⁺ and phosphate (PO₄³⁻) concentrations were inversely related to environmental concentrations, suggesting that these ions are preferentially retained and that mechanisms for mobilization are up-regulated under diminished environmental concentrations. Plasma 17β-estradiol, 11-ketotestosterone and testosterone, peaked in mid-late vitellogenic females, while the androgens peaked in spawning males. Urine Ca²⁺ was more tightly regulated than other divalent ions and decreased in spawning fish. Therefore, the increases in free plasma Ca²⁺, the very low circulating concentrations of free and total Ca²⁺, and the increase in PO₄³⁻ and bound Ca²⁺ in low Ca²⁺ environments indicate unique adaptations to Ca²⁺ regulation in the lake sturgeon.     

The primary localization of ascorbate and its synthesis in the kidneys of acipenserid (Chondrostei) and teleost (Teleostei) fishes

The kidneys of the rainbow trout Oncorhynchus mykiss, the channel catfish Ictalurus punctatus (both Teleostei), and the white sturgeon, Acipenser transmontanus (Chondrostei) displayed similar profiles of ascorbate distribution irrespective of the capability of synthesizing ascorbic acid. The head kidney was found to be the richest in ascorbate, whereas the trunk kidney showed significantly lower ascorbate levels in all three species. The head kidney richness in ascorbate was correlated with the localization of the cortical and chromaffin tissues known to accumulate ascorbate in some fish and mammals. Based on ascorbate concentration, it was possible to distinguish the head from the trunk kidney in salmonids and sturgeons which have an antero-posterior-fused kidney. The absence of l-gulonolactone oxidase activity in the kidneys of the channel catfish and the rainbow trout was asserted biochemically. We also confirmed that the ascorbic acid-synthesizing enzyme exists in white sturgeon kidney, and found that the enzyme distribution was inversely correlated with ascorbate concentrations. An active transport of ascorbate might exist in the head kidney of both acipenserids and the teleosts in order to maintain this vitamin at high concentrations. This report suggests a link between ascorbate concentration and its physiological functions in kidneys of lower vertebrates.Abbreviations AA ascorbic acid - TAA total ascorbic acid - DHA dehydroascorbic acid - DCIP dichloroindophenol - EDTA ethylenediaminetetra-acetic acid - GLO l-gulonolactone oxidase     

Changes in sodium,calcium and magnesium ion concentrations in sturgeon (Huso huso) urine and in kidney morphology

During adaptation to brackish water the young great sturgeon Huso huso is able to regulate its serum osmolarity and ion concentrations. After transfer from fresh water to brackish water the ion concentrations in the urine increase and the urine becomes isoosmotic to the blood serum after 24h. The Na⁺ and K⁺ concentrations in the urine increase during the first 12 h by 4.4 and 7.7 times, respectively, later decreasing again. The Mg²⁺ and Ca²⁺ concentrations in the urine increase by 3.4 and 14 times during the first 72h in brackish water and remain high thereafter. These results suggest that the kidneys play an important part in the regulation of serum osmolarity and in the removal of Ca²⁺; however, in contrast to teleosts, Mg²⁺ must be removed extrarenally. During adaptation to a hyperosmotic medium the diameters of the Malpighian bodies, the glomeruli and the diameter of the tubules initially all decrease, but the distal tubules become morphologically differentiated into two regions and the diameter of the distal section later increases again. It is suggested that this is the site of Ca²⁺ secretion into the urine.     

The ultrastructure and vascular supply of the different fibre types in the axial muscle of the sturgeon Acipenser stellatus,Pallas

Summary The ultrastructure and vascular supply of the different fibre types in the lateral muscles of the sturgeon Acipenser stellatus were studied by light- and electron microscopy and morphometry. Three fibre types form separate layers without intermingling. The red fibres are superficial, the white fibres deep and the intermediate fibres between them. From morphometric analyses, the mitochondrial volume fraction in red fibres is 30%, in intermediate fibres 3.7% and in white fibres 0.7%. Z lines are most fuzzy in the red fibres. Triads of the sarcotubular system are always situated at the level of the Z discs. In red fibres the three elements are arranged in a series along the myofibrils, whereas in white fibres they are arranged transversely and in the intermediate fibres they are aligned obliquely. The number of capillaries surrounding each fibre is 2.3, 0.9 and 0.2 for the red, intermediate and white fibres, respectively. In red fibres 16% of the surface is directly covered by capillaries. The corresponding percentages for intermediate and white fibres are 5 and 1, respectively. Per unit volume of the fibre, the directly vascularised fibre surface in red fibres is about ten times larger than that of white fibres.The degree of vascularisation of the fibre types is directly related to the volume fraction of mitochondria, and thus to their aerobic capacities.     

Monoclonal antibodies to plasma high density lipoprotein (HDL) of eel (Anguilla japonica)

Six week-old female mice (Balb/c) injected intraperitonealy with 50 μg of eel high density lipoprotein (HDL) emulsified with equal volume of adjuvant three times every two weeks. Three weeks after the third injection, hyperimmunized mice were boosted by injection of 100 μg of HDL. After 5 days, the best responding mouse to injected HDL was sacrificed, and spleen cells were fused with mouse myeloma cells (Sp2/O–Ag14), and hybridomas were cultured in a selection medium. Monoclonal antibodies specific to apolipoprotein A-I or A-II (apoA-I or apoA-II) of HDL were obtained by cloning and recloning the hybridomas. Eighteen monoclonal antibodies specific to apoA-I and/or apoApII were isolated. Antibodies in the culture medium were purified by a HiTrap Protein G or an eel-HDL column. These purified antibodies belong to the subclass IgG1. The monoclonal antibodies specific to eel apoA-I and apoA-II secreted by clone 10D12 and 2G3, respectively, interact with serum proteins of some fish species such as red-sea bream and carp. The anti-eel apoA-I antibody of 10D12 did not bind to serum proteins of rat, rabbit, and chicken, while the anti-eel apoA-II of 2G3 antibody did.     

Age/size effects on juvenile green sturgeon, Acipenser medirostris, oxygen consumption, growth, and osmoregulation in saline environments

The green sturgeon, Acipenser medirostris, is an anadromous species that migrates from freshwater (FW) to seawater (SW) relatively early in its life history, although the ages and sizes of juveniles at SW entry are not known. Developmental constraints of osmoregulatory organs may either prohibit (i.e., due to salinity tolerance limits) or minimize (i.e., due to substantial osmoregulatory or ionoregulatory energetic costs) SW entry in small fish. Interestingly, larger green sturgeon are often encountered in brackish water (BW) estuaries, perhaps due to an energetic advantage in occupying these near-isosmotic environments. To test hypotheses concerning fish-size effects on the energetic costs of occupying habitats of different salinities, we measured oxygen consumption rates in green sturgeon representing three age groups (100, 170, and 533 days post hatch; dph), which were acclimated for 5 weeks to one of three salinities (FW, <3‰; BW, 10‰; or SW, 33‰). Also, after 7 weeks, final wet masses were compared and blood and muscle tissue samples were taken to assess osmoregulatory abilities. There were no differences in body-mass-adjusted oxygen consumption rates between any salinities or ages, indicating that the energetic costs were not prohibitively high to occupy any of these salinities. The only mortalities occurred in the 100 dph SW group, where 23% of the fish died, from apparent starvation. Final wet masses were comparable between FW and BW for each age group and with the 533 dph SW group, but were lower in SW groups at 100 and 170 dph. Similarly, osmoregulatory abilities, in terms of plasma osmolality, Na⁺, K⁺, lactate, and protein concentrations, and muscle water content, were comparable in FW and BW groups at all ages, and with the SW group at 533 dph. These results indicated an age/body size effect in hyperosmotic adaptability, and that juvenile green sturgeon may be found in FW or BW at any age, but only have the ability to enter SW by 1.5 years (75 cm, 1.5 kg) of age.     

First report on embryonic and larval development of 2n/3n mosaic sterlet

Mosaicism is frequently observed in aquaculture practices, and it adversely affects the production as well as the restoration programme of the sturgeon. The purpose of the present study was the induction of 2n/3n mosaic in sterlet, Acipenser ruthenus L., and compare their embryonic and larval development with diploid control sterlet. Microsatellite DNA loci genotyping was conducted for the identification of the genotypes and parentage analysis. Embryonic development was monitored in experimental groups at every 24 h interval. Identification of individual stages of embryonic development was recorded based on a 36-degree scale of development. Additionally, the BW and body length (LT) of experimental fishes were taken during 110 days of the rearing period. The Fulton’s condition coefficient (F), length-weight parameters, and specific growth rate (SGR) coefficient were calculated. The analysis of embryonic development of the 2n/3n mosaic and the diploid control group did not show differences. However, higher mortality (88%) was observed in 2n/3n mosaic groups in comparison to the diploid control groups (55%). BW and body length of 2n/3n mosaic sterlet were slightly lower than the diploid control sterlet, but the differences were not statistically significant. F analysis did not confirm a lower growth performance of the fishes in the 2n/3n mosaic group. Microsatellite DNA loci genotyping confirmed both the incidence of polyspermy and retention of the second polar body. This paper presents the first report on embryonic development and growth performance of 2n/3n mosaic sturgeons.     

不同喂食方法对产后野生中华鲟的摄食促进

2006年1月13日~7月15日,研究了不同喂食方法对产后野生雌性中华鲟(Acipenser sinensis)的摄食促进效果。研究表明,经人工繁殖后的中华鲟身体较虚弱,在人工环境下无主动摄食行为。野生中华鲟对投洒的人工配合饲料及天然饲料均无摄食反应,水下直接喂食天然饲料的效果依赖于中华鲟主动摄食能力的恢复,而采用导管喂食方法可以实现中华鲟的被动摄食,摄食量由76g逐步增加至382g,20d后开始出现主动摄食行为,日食量逐步上升至1822g并趋于稳定。导管喂食过程中健康状况也逐步得到改善,胸围和腹围开始提高,主动摄食后健康状况得到彻底改善。实验表明产后野生中华鲟的体能恢复有望在水族馆较好的环境条件中得以实现。     

In vitro sperm maturation in sterlet,Acipenser ruthenus

The aim of the study was to examine sperm maturation in sturgeon and to establish the localization of the maturation. We demonstrated that sperm maturation occurs in sturgeon outside the testes via dilution of sperm by urine. The process involves the participation of high molecular weight (>10 kDa) substances and calcium ions.     

鲟鱼鱼肠抗氧化肽的提取及抗氧化性

探讨酶法制备具有抗氧化活性的鲟鱼鱼肠抗氧化肽的方法,并进行体外抗氧化活性的测定。结果表明,比较4种蛋白酶酶解产物的抗氧化能力,确定胃蛋白酶为制备鲟鱼鱼肠抗氧化肽的最佳水解用酶;通过单因素试验和正交实验分析得出最适酶解工艺是:胃蛋白酶加酶量3 200 U/g,酶解时间1.5 h,料液比1∶20,温度35℃。其体外抗氧化能力随肽质量浓度增大而增大,在浓度为1.5 mg/mL时,鲟鱼鱼肠抗氧化肽清除DPPH·能力达到Vc的83.64%,对·OH清除率为78.06%,还原力大小约为Vc溶液的1/3。胃蛋白酶酶解鲟鱼鱼肠制备的抗氧化肽具有较好的抗氧化活性,其作为一种潜在的商业抗氧化剂具有良好的应用前景。