Metabolic pattern of the heart of haemoglobin- and myoglobin-free Antarctic fish Channichthys rhinoceratus

Summary Maximum activities of energy metabolism related enzymes, myofibrillar ATPase and concentrations of carnitine, lipids and myoglobin have been assayed in heart and white muscle of the ice-fish Channichthys rhinoceratus. Results are compared with those of the redblooded Paranotothenia magellanica. Increased activities of glycolytic enzymes and extremely high lactate dehydrogenase activity have been found in icefish heart, suggesting a substantial involvement of anaerobic glycolysis under conditions of oxygen depletion. During normoxia, ATP generation is achieved via oxidative pathways of carbohydrate or fatty acid catabolism. Possible implication of the myocardium in homeostatic regulation by lactate oxidation is also discussed.     

银鱼的产量能预报吗

将离散Ｌogistic模型应用于银鱼种群数量变动研究,通过对滇池等４个典型湖泊或水库的银鱼年产量变动的初步分析和模拟,发现现的有的湖泊或水库银鱼产量的参数值都落入了混沌区间,在自然生态系统中找到了混沌行为的证据。同时指出：（１）混沌行为使银鱼产量长期预报不可能实现,只有短期预报才能保证必要的精度。（２）严格控制捕劳对尚未繁殖的亲鱼的影响,保留足够的繁殖亲鱼,才能保证资源的持续利用。另一方面,如谷获得相对稳定的产量,可能控制捕捞死亡率Ｆ来改变增增长率参数μ,防止银鱼产量剧烈波动。（３）水域污染和其他破坏水域饵料生物种群结构的因素能导致银鱼的内禀自然增长率γ值和最大种群数量Ｎmax发生变化,从而引起种群的数量变动。     

Apparent deficiency of metallothionein in the liver of the Antarctic icefish Chionodraco hamatus. Identification and isolation of a zinc-containing protein unlike metallothionein.

1. A zinc-binding protein has been isolated and purified from the liver of the icefish Chionodraco hamatus. 2. The icefish Zn-protein has characteristics distinct from those of metallothionein. 3. The amino acid composition shows a low content of cysteine and a high content of glutamate and aspartate. 4. No metallothionein has been detected in the extracts from icefish liver.     

Degradation of icefishes (Salangidae) in the Yangtze River basin of China: threats and strategies

The Yangtze River basin has been a major area in terms of icefish diversity conservation and fisheries. In the past two to five decades, however, the wild icefish resources have degraded continuously in both the brackish estuary and freshwater portions of the basin. Stocks have declined in all icefish fisheries, resulting in an annual fishing yield decrease from the maximum of 4,000 metric tons to less than 1,300 metric tons in this river basin. The stocks decline significantly (t = −6.74, df = 1, p < 0.001) correlated with icefish fishing stress in the estuary. Meanwhile, species composition changed markedly with smaller sized icefish species increased relative to the number of larger ones in terms of their relative abundances. Following the stocks decline and size reduction, icefish commercial value decreased to the point that 91.9% of the traditional icefish-producing waters (57 out of 62) terminated their icefish fisheries and some species became locally extinct. Based on the degradation process, we suggest that these changes in stock size and species diversity are the result of overfishing and habitat loss and degradation. We propose a number of measures aimed at the conservation and restoration of the wild icefish resources in the Yangtze River basin.     

Structure and expression of genes involved in transport and storage of iron in red-blooded and hemoglobin-less antarctic notothenioids

Antarctic notothenioids are characterized by a drastic reduction of the hemoglobin content, a condition that reaches its extreme in icefish that, following a gene deletion event, are completely devoid of hemoglobin. To answer the question on what type of adaptive changes occurred in icefish to prevent accumulation of potentially dangerous ferrous iron, we investigated the genes of four proteins known to play a key role in iron metabolism. For this purpose, we cloned and sequenced the cDNAs encoding ceruloplasmin, transferrin, ferritin and divalent metal transporter 1. While the inferred amino acid sequences of transferrin from different Antarctic fish species showed a high level of similarity with the homologous proteins from other species, ceruloplasmin sequence featured amino acid substitutions affecting a copper binding site. Another peculiarity was the presence in subunit H of the icefish ferritin of the two sets of sites involved in iron oxidation and iron mineralization, which in mammals are located on two distinct ferritin subunits. Significant differences in the expression levels of the four genes were found between hemoglobinless and red-blooded notothenioids. An increased expression of ceruloplasmin mRNA in icefish was interpreted as a compensatory mechanism to prevent accumulation of ferrous iron in hemoglobinless fish. In icefish, the amounts of ferritin H-chain mRNA measured in liver, blood and head kidney were lower than in the same organs of the red-blooded fish. In the spleen of both fishes, the expression levels of ferritin H-chain were significantly lower than in the spleen of a "pink-blooded" notothenioid with an intermediate hemoglobin content. Finally, the amount of divalent metal transporter mRNA measured in the head-kidney was lower in the icefish than in the same organ of its red-blooded counterpart. These results indicate that the loss of hemoglobin in icefish is accompanied by remodulation of the iron metabolism.     

The heart of the Antarctic icefish as paradigm of cold adaptation

The stenothermal Antarctic fishes, particularly the hemoglobinless icefish, have developed biochemical, metabolic and morpho-functional features of cardiac performance that can help to decipher some mechanisms underlying cardiac cold adaptation. Examples taken from different levels of cardiac biology in Antarctic fish as a paradigm of cold adaptation include: the function of myoglobin in the icefish species that either express or do not express this pigment; the metabolic and ultrastructural reshaping of the myocardiocytes; and the intrinsic mechanical characteristics of the icefish heart ventricle as a low rate, low pressure and high volume pump.     

The blood proteins of the Antarctic icefish Channichthys rhinoceratus: biological significance and purification of the two main components

The lack of hemoglobin and of carbonic anhydrase in the blood of icefish suggest that substantial adaptations of the acid-base balance should occur in order to ensure blood pH homeostasis. The level of peptidic histidyl and of reactive -SH groups per unit of body mass in icefish plasma are 12–13 times higher than those of Notothenia rossii, a common red-blooded Antarctic species. It is proposed that the high level of imidazole ring in icefish plasma improves the non-bicarbonate buffering capacity and that the reactive sulfhydryls are involved in a redox buffer as in some other hypoxia tolerant species. After plasma fractionation on Ultrogel AcA 34, the two main icefish serum proteins have been purified by DEAE cellulose chromatography (IFI) and by HPLC on anion exchange column (IF2). IFI has been identified as a cysteine-rich para-albumin and IF2 as an histidine-rich immunoglobulin-like protein.     

Freshwater icefishes (Salangidae) in the Yangtze River basin of China: Spatial distribution patterns and environmental determinants

Synopsis We surveyed 86 lakes affiliated to the Yangtze River to assess the status of natural freshwater icefishes, and to study their spatial distribution patterns and environmental relationships. Results showed that the spatial patterns of icefish diversity and the occupancy of each species related closely to the historical process of habitat fragmentation. Statistical analyses indicated that the spatial structure of the icefish assemblage significantly related to the area- and isolation-related environmental variables. These results illustrated the significant impacts of hydrological engineering (dykes and floodgates) on the historical dynamics of the icefish populations, and shed light on the essentiality and feasibility of conserving and wise using freshwater icefishes by managing suitable habitats and re-connecting the river-lake network in the Yangtze River basin.     

Growth and reproduction of the non‐native icefish Neosalanx taihuensis Chen, 1956 (Salangidae) in a plateau lake,southwestern China

Growth, reproduction and abundance traits of the invasive icefish Neosalanx taihuensis Chen, 1956 were investigated monthly from July 2009 to May 2011 in Lake Erhai on the Yunnan‐Guizhou Plateau, south‐western China, in order to explore the changes in life‐history traits after translocation. The results indicated that the icefish exhibited obvious plasticity in growth and reproduction traits. Growth of the fish in Lake Erhai was faster than that in native waters and in other translocated reservoirs. By fitting the von Bertalanffy growth model to the data, it was estimated that icefish obtain an asymptotic size of 96.12 mm, a K of 1.61, and a t₀ of ‐0.26; the calculated overall growth performance index φ′ was 4.17. The strategy of reproduction changed from multiple‐ to single‐spawning. The spawning period was from October to December with the absolute and relative fecundities of 1250 ± 169 eggs per ind and 2557 ± 245 eggs per g, respectively. Plasticity in icefish growth and reproduction in Lake Erhai greatly facilitated its population establishment, making it one of the most abundant fish species. The icefish invasion in the lake may be one of the reasons for the decrease or extinction of native fish species populations, and some measures for the control of this invasive fish are suggested.     

Changes in abundance of the icefish Neosalanx pseudotaihuensis Zhang (Salangidae) and the impact on the zooplankton community of Xujiahe Reservoir,central China

The icefish Neosalanx pseudotaihuensis Zhang is a small and commercially exploited zooplanktivorous fish in Xujiahe Reservoir (central China). Data of catch per unit effort (CPUE) from June 1995 to December 1997 show that the abundance of the icefish varied dramatically, which is reflected in the populations of the dominant cladocerans. The densities of Leptodora kindti, Daphnia galeata and Diaphanosoma dubia were the highest in 1997 when the abundance of the icefish was the lowest, and the reverse was the case for Boimina spp. These results document that the population of this annual fish is very variable and high biomass of the fish could exert a pronounced effect on the zooplankton community.     

Drinking in Antarctic fishes

Drinking rates have never been measured in Antarctic fish. Drinking rates were measured in four species of notothenioid fish, including a hemoglobinless icefish, found in the near-freezing waters of the Ross Sea of the Southern Ocean. All of the fish, with the exception of the icefish, had low drinking rates and high serum osmolalities relative to temperate seawater fish. The icefish had significantly higher drinking rates and serum osmolalities relative to the Antarctic fishes containing hemoglobin, including Trematomus bernacchii. Warm acclimation of T. bernacchii, from −1.5°C to +4°C for 4 weeks, significantly increased their drinking rates 4.6-fold, significantly decreased their serum and intestinal osmolality by 11% and 12%, respectively, relative to cold-acclimated fish. These results indicate that increased drinking rates in Antarctic fish at elevated temperatures are involved in maintaining a lower serum osmolality.     

中国银鱼的多样性及其保护对策

中国是世界银鱼（银鱼科Salangidae的简称）的起源地和主要分布区,在中国东部近海和各大水系的河口共分布有世界17种银鱼中的15种,其中特有种6种。银鱼营养价值和经济价值均很高,是重要的经济鱼类。银鱼生活周期短、世代离散、生殖力和定居能力强。作为典型的r对策者,银鱼对环境变化敏感且反应迅速,种群消长快,在漫长的进化过程中形成了其种间食性、生长和繁殖等生物学和生态学特征的丰富的多样性。然而我国的银鱼天然资源却因围湖造田、过度捕捞、环境污染和生境破碎化等多种因素的影响而持续衰退,各种银鱼的天然资源都不同程度地下降,物种分布范围显著缩小,个别物种渐危。本文在综述我国银鱼生物学、生态学和生物多样性研究的基础上,分析了我国银鱼研究及其物种多样性和种质资源保护工作中所面临的问题;呼吁审视银鱼移植增殖的生态效应,加强银鱼的基本生态学研究和生物多样性保护,并提出我国银鱼资源保护和可持续利用的对策。     

Shedding new light on the life cycle of mackerel icefish in the Southern Ocean

Mackerel icefish have a widespread distribution in the Atlantic and Indian Ocean sectors of the low-Antarctic region. Biological characteristics differ considerably between populations in the southern Scotia Arc and those living further to the north. Fish living in the north mature 1 year earlier than in the south. They have a much shorter life span and die after they have spawned two to three times. The number of eggs produced per gram of body mass is higher in the north. Stocks have declined in most parts of the distributional range due to the impact of fishing and due to natural causes. Increases in populations of Antarctic fur seals at South Georgia and parts of the Indian Ocean appear to have led to increased predation on stocks of icefish. Shifts in hydrological regimes in the northern part of the distributional range have either started to lead or will lead to deteriorating living conditions for mackerel icefish in the near future. Fish stock assessment needs to take these constraints into consideration when providing advice on total allowable catches for fisheries management.     

Blood rheology of Antarctic fishes: viscosity adaptations at very low temperatures

Viscosity of whole blood and plasma from Antarctic fishes were compared over a temperature range of −1.5 to 5°C; human samples and water provided reference values. Blood viscosity of nototheniids was greater than that of the haemoglobinless icefish, reflecting differences in packed cell volume, being 5.27 v. 3.27 cP at 0°C for Notothenia coriiceps and Chaenocephalus aceratus , respectively. The reduction in MCHC, rather than haematocrit, in nototheniids suggests that selection pressure has not acted at the level of oxygen transport. However, icefish plasma viscosity was similar to human, but greater than that of Notothenia spp., suggesting that viscometric influences on cardiac afterload may be adaptive for the latter. Indeed, handling stress induced a significant increase in viscosity of both whole blood and plasma which may impair cardiovascular performance. Such a response was not observed in icefish, and in view of the large blood vessels it is unlikely that viscosity plays any significant role in limiting activity of this species.     

Growth of the Icefish Neosalanx pseudotaihuensis (Salangidae) in Xujiahe Reservoir,Central China

The icefish Neosalanx pseudotaihuensis(Salangidae) is a small (to 70mm TL), transparent fish that occurs naturally in central and eastern China. It is commercially important in many lakes and reservoirs, and recently has been introduced into other waters. However, very little is known about its biology including growth. In this paper we studied the population structure and the growth of the icefish in Xujiahe Reservoir (central China) from May 1995 to December 1997. The icefish completed its life cycle within about one year and the population consisted of one cohort. The main growth period was May to December and little growth occurred at other times. Remarkable seasonal and interannual variations in the growth rates were found and these are discussed in relation to food availability, water temperature and fishing activity.     

Antarctic icefishes (Channichthyidae): a unique family of fishes. A review, Part II

Icefish or white- blooded fish are a family of species unique among vertebrates in that they possess no haemoglobin. With the exception of one species which occurs on the southern Patagonian shelf, icefish live only in the cold-stable and oxygen-rich environment of the Southern Ocean. It is still questionable how old icefish are in evolutionary terms: they may not be older than 6 Ma, i.e. they evolved well after the Southern Ocean started to cool down or they are 15–20 Ma old and started to evolve some time after the formation of the Antarctic Circumpolar Current. Individuals of most icefish species with the exception of species of the genus Champsocephalus have been found down to 700–800 m depth, a few even down to more than 1,500 m. Icefish have been shown to present organ-level adaptations on different levels to compensate for the ‘disadvantages’ of lacking respiratory pigments. These include a low metabolic rate, well perfused gills, increased blood volume, increased cardiac output, cutaneous uptake of oxygen, increased blood flow with low viscosity, enlarged capillaries, large heart, and increased skin vascularity. Biological features, such as reproduction and growth, are not unique and are comparable to other notothenioids living in the same environment. Icefish produce large yolky eggs which have a diameter of more than 4 mm in most species. Consequently, the number of eggs produced is comparatively small and exceeds 10,000–20,000 eggs in only a few cases. With the exception of species of the genus Champsocephalus which mature at an age of 3 to 4 years, icefish do not attain maturity before they are 5–8 years old. Spawning period of most icefish species is autumn–winter. The incubation period spans from 2 to 3 months in the north of the Southern Ocean to more than 6 months close to the continent. Growth in icefish to the extent it is known is fairly rapid. They grow 6–10 cm in length per annum before they reach spawning maturity. Icefish feed primarily on krill and fish. Some icefish species were abundant enough to be exploited by commercial fisheries, primarily in the 1970s and 1980s with Champsocephalus gunnari as the main target species. Most stocks of this species had been overexploited by the beginning of the 1990s, some had further declined due to natural causes. Other species taken as by-catch species in fisheries were Chaenocephalus aceratus, Pseudochaenichthys georgianus, and Chionodraco rastrospinosus. Chaenodraco wilsoni was the only species exploited on a commercial scale in the high-Antarctic. Part I was published in the preceding issue of Polar Biology. DOI 10.1007/s00300-005-0019-z.