Ascorbic acid status of mullet, Mugil cephalus Linn., exposed to cadmium

The effects of acute and chronic cadmium exposures on ascorbic acid concentrations and cadmium accumulation in the tissues of juvenile mullet, Mugil cephalus , are described. Hepatic ascorbic acid reserves were maintained in untreated mullet fed a diet containing ascorbate, but decreased 60% in individuals exposed to 10 mg Cd 1^-1 for six weeks. Ascorbic acid depletion was accompanied by a massive accumulation of cadmium in the liver. Similar changes were found in gill tissue. In contrast, ascorbic acid concentrations were largely unaffected in kidney tissue which had a limited capacity to accumulate the metal. There were marked fluctuations of ascorbic acid levels in the brain. Only small amounts of cadmium were accumulated by this tissue. These results indicate that in mullet liver, gill and brain ascorbic acid stores may be depleted during chronic cadmium poisoning.     

鄱阳湖发现鲻北大核心CSCD

鲻(Mugil cephalus)隶属于鲻形目(Mugiliformes)鲻科(Mugilidae)鲻属,为浅海中上层鱼类,广泛分布于太平洋、印度洋、大西洋、地中海、黑海等温带和热带近岸海区,我国沿海均有分布。鲻对盐度的适应广,在淡水、咸淡水和盐度高达40的海水中都能生活,适温范围3~35℃,喜暖水(区又君2015)。鲻个体大、生长快、食物链短,是我国沿海经济鱼种。鲻可栖息在近岸浅海、河口的咸淡水交界处及港湾内,在长江主要分布于其河口附近(毛节荣1991,倪勇等2006)。     

Effects of cadmium toxicity upon the in vivo and in vitro activity of proteins and five enzymes in blood serum and tissue homogenates of Mugil cephalus

This study reports changes in total protein and certain liver, heart, gill and serum enzymes after exposing fish or tissue homogenates and serum to Cd, i.e. in vivo and in vitro effects. Five enzymes were selected for assay; aspartate amino transferase (AAT), alanine amino transferase (A1AT), alkaline phosphatase (A1P), acid phosphatase (ACP) and lactic dehydrogenase (LDH). Total protein content in the exposed fish showed an increase in the liver, gill and serum while there was no change in heart protein. The sensitivity of the five assayed enzymes to Cd varied in different tissues. Gill AAT, A1AT were the most sensitive. Liver A1P and heart LDH showed the maximum inhibition at higher Cd concentrations.     

Extravascular circulation in the pituitary of Mugil cephalus (Teleostei)

Summary Extravascular circulation in the pituitary of Mugil cephalus was investigated by injecting live fish with horseradish peroxidase and studying the distribution of the enzyme in the gland. The principal components of the extravascular circulatory system are the pericapillary spaces, and, arising from them, the interlobular and circumhypophyseal spaces. Extensions of these spaces penetrate the glandular parenchyma of the pars distalis, where they merge with pericellular spaces. In the neurohypophysis, pericapillary spaces are connected to the periaxonal spaces.Capillaries penetrating from the proximal neurohypophysis into the pars distalis are accompanied by neurosecretory axons. These axons form a mass of tissue which is limited near the capillaries by the pericapillary spaces and near the adenohypophysis by the interlobular spaces. Toward the interior of the adenohypophysis the amount of nervous tissue accompanying the capillaries progressively diminishes, thus reducing the distance between pericapillary and interlobular spaces. Within the pars distalis, the neurosecretory axons accompanying the capillaries are sparse, and the secretory and stellate cells are mostly located directly adjacent to the pericapillary spaces. In the neuro-intermediate lobe, interlobular spaces outline the neuro-adenohypophyseal boundary.The relationship between extravascular spaces and hormone-secreting cells varies in the different regions of the adenohypophysis depending upon the type of neurosecretory innervation in the respective region. In the regions of prolactin and gonadotropin cells, where neurosecretory axons are in direct contact with the secretory cells, the hormone-secreting and stellate cells are adjacent to the pericapillary spaces. In the regions of ACTH and STH cells, secretory and stellate cells are found adjacent to the interlobular spaces, which are interposed between the cells and the neurosecretory axons.Abbreviations AH adenohypophysis - CH circumhypophyseal - DNH distal neurohypophysis - HRP horseradish peroxidase - NH neurohypophysis - NS neurosecretory - PD pars distalis - PI pars intermedia - PPD proximal pars distalis - RNH rostral neurohypophysis - RPD rostral pars distalis This research was supported by a grant from the National Council for Research and Development, Israel, and the GKSS Geesthacht-Tesperhude, Federal Republic of Germany     

鲻鱼嗅囊组织形态结构观察及功能探讨

实验用鱼为全长35.5~40.0 cm的野生鲻(Mugil cephalus),采用石蜡切片以及透射电镜技术对鲻的嗅囊以及嗅板细胞进行观察。结果表明:鲻的嗅觉器官由左右两个呈扁平椭球形嗅囊构成,分别由前后两个鼻孔与外界相通。嗅囊长径与眼径之比为0.80,长径与短径之比为2.09。嗅囊的嗅轴左右两边分别有垂直于嗅轴并向上倾斜排列整齐的18~25个披针形嗅板,只有初级嗅板未见次级嗅板。嗅板由中央髓和两侧的嗅上皮两部分构成,中央髓由疏松的结缔组织和毛细血管组成。嗅上皮又分为感觉区和非感觉区,感觉区位于嗅板的内侧,具有发达纤毛,呈连续分布状态,非感觉区位于嗅板边缘,细胞纤毛较少。通过光镜和电镜的综合研究结果显示嗅上皮细胞大致可分为5类:基细胞、支持细胞、纤毛非感觉细胞、纤毛感觉细胞和柱状细胞。文章讨论了鲻的感官活动类型。     

Effect of storage time on haematological parameters in mullet,Mugil cephalus

The aim of the present study was to assess the effect of storage time at +4 °C on red blood cell count (RBC), haematocrit (Hct), haemoglobin (Hb), white blood cell count (WBC), thrombocyte count (TC), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) in mullet (Mugil cephalus) using an automatic method. After blood collection (T₀), all samples were analyzed using both the manual and automatic method. To test the validation of the automatic method, a paired t‐test was applied, and no statistical difference was observed. The samples were successively divided into four different aliquots and stored at +4 °C to assess the haematological parameters using the automatic method. The first aliquot was refrigerated for 6 h, the second one for 24 h, the third one for 48 h and the last one at for 72 h. One‐way repeated‐measures ANOVA showed a significant effect of storage time (P < 0.05) on Hb, WBC, TC, MCH and MCHC. These results suggest that haematological parameters can be assessed within 6 h from blood collection when samples are stored at +4 °C because long‐term storage modifies the results of the analyses. Further studies on these parameters could be still needed in various fish species to validate an appropriate method for haematological analysis useful not only for the evaluation of the health status of animal living in captivity and in aquaculture but also to have reliability environmental haematological biomarkers. Copyright © 2012 John Wiley & Sons, Ltd.     

Ontogenetic dietary shifts and morphological correlates in striped mullet,Mugil cephalus

Synopsis Ontogenetic dietary shifts are well studied in fishes. However, these shifts are rarely correlated with habitat and morphology. This study investigates: (1) ontogenetic dietary changes in mullet; and if dietary shifts do occur (2) whether they are correlated with feeding location, feeding behavior and/or feeding morphology. Stomach contents from eight size classes, each with 25 individuals, were analyzed using a gravimetric sieve fractionation procedure, Czechanowski's Quantitative Index and cluster analysis. Core samples (5 mm deep) were also analyzed in the same manner. Morphological characters were measured to detect differences among the size classes. Cluster analysis showed three distinct trophic units for Mugil cephalus in Cross Bayou: (1) 20.0 mm standard length — 30.0 mm SL; (2) 30.0 mm SL — 40.0 mm SL; and (3) 40.0 mm SL — > 100 mm SL. Comparison of the gut contents to the sediment contents for each size class showed an increase in similarity as the fish grew. Mullet gut contents from fish 20–25 mm SL were only 45% similar based on the weights of the prey items to the sediment subsample prey items, while stomach contents from fish > 100 mm SL were 84% similar to the sediment subsample contents. Gill raker length and interraker spacing of four gill arches were allometric with respect to standard length. Prey particle size within size classes appeared to be more correlated with feeding behavior than gill interraker spacing because smaller particles than predicted by the interraker spacing were ingested. It is suggested that smaller fish may be browsing more selectively than larger fish which graze.     

Motile aeromonas infection of striped (grey) mullet Mugil cephalus

Infection of striped mullet (Mugil cephalus) with Aeromonas hydrophila results in an acute septicemic disease. The disease can be experimentally induced by intramuscular injection, skin or gill scarification or by the oral route using pellets purposely seeded with bacteria. The organism was isolated from the blood 1–2 days after infection and from all organs 24 hr or longer after infection. The disease is characterized by early inflammatory and proliferative changes and later necrotic changes. Enteritis and hepatic necrosis are constant findings in aeromonad disease of M. cephalus but surface lesions are not pathognomic for these infections in mullet. Death of infected fish may be attributed to bacterial toxins which cause necrosis of parenchymal organs and soft tissue structure.     

Haematological and serum protein profiles of Mugil cephalus: effect of two different habitats

The aim of this study was to assess the influence of two different habitats, Faro Lake (group A) and Tyrrhenian Sea (group B), on the haematological and serum protein profiles of Mugil cephalus. Our results showed significant differences of white blood cells, total proteins, prealbumin, albumin and α-globulins between groups A and B. These findings suggest that changes in haematological and serum protein profiles are important indices in monitoring the effects of aquatic habitat changes, representing an adaptive physiological response to different habitats of M. cephalus.     

Isolation and characterization of microsatellite loci in the striped mullet,Mugil cephalus

Forty‐three microsatellites were isolated from grey mullet (Mugil cephalus) of Mediterranean origin using the standard enrichment methods followed by enhanced chemiluminescence for the rapid identification of clones containing microsatellites. Eleven microsatellites were characterized to assess genetic diversity of different populations surrounding the island of Sardinia in Italy. The versatility of these markers was also assessed using an Australian population. All 11 microsatellites were highly polymorphic with a mean heterozygosity of 0.834. The number of alleles ranged from 14 to 38 in the Sardinian populations and from 11 to 25 in the Australian samples.     

Cascading effects of the flathead grey mullet Mugil cephalus in freshwater eutrophic microcosmos

Flathead grey mullet (Mugil cephalus L.) stocked in fish ponds were long considered to feed primarily on detritus. However, recent research has found that they obtain much of their food from plankton and that they have a detrimental effect on pond zooplankton and large phytoplankton, whilst enhancing small phytoplankton. It has been suggested that flathead grey mullet may also increase the internal phosphorus loading of the ecosystem, which would also increase phytoplankton density. To test whether zooplankton removal or nutrient release from the sediment is the better explanation for phytoplankton enhancement in the presence of flathead grey mullet, the ecosystems of fish-less tanks, tanks with a 60 m mesh filter and tanks stocked at a fish density of 243 g m^-3 were compared. In the presence of flathead grey mullets, cladocerans, ostracods and chironomid larvae became scarcer than in the control tanks, while there were more small phytoplankton and mud snails. The green algae Cladophora sp. did not occur at all. The presence of a mechanical filter also reduced cladoceran, ostracod and chironomid densities and increased phtyoplankton and mud snail density. However, the situation observed in filter tanks was intermediate between that observed in the fish tanks and the control tanks, due to the lower filtering efficiency of the mechanical filter. The organic matter content of the sediment decreased throughout the experiment in the control and filter tanks, but remained stable in fish tanks. Phosphorus and nitrogen concentrations were not affected by any treatment. These results showed that flathead grey mullet enhanced phytoplankton development due to the removal of large cladocerans and not as a consequence of nutrient release. Furthermore, the flathead grey mullet strongly modified the benthic community, probably due to direct predation.     

Involvement of Enterobacter cloacae in the mortality of the fish, Mugil cephalus

Aims:  To identify the causative agent of the mortality in the fish, Mugil cephalus , in Muttukadu lagoon.
Methods and Results:  An enteric bacterium from the kidneys of moribund fish M. cephalus , was isolated and identified as Enterobacter cloacae (MK). Mugil cephalus was experimentally infected by this isolate and was re-isolated from the kidneys of the moribund fish. Enterobacter cloacae isolates from the lagoon water (MW1, MW2 and reference strain ATCC 13047) and the reference strain were not able to induce similar pathogenesis. The putative factor imparting pathogenicity to the MK isolate was identified as a cationic molecule, which migrated towards the cathode on agarose gel electrophoresis.
Conclusions:  The Ent. cloacae (MK) isolate harbouring a cationic factor was the causative agent for the mortality of M. cephalus , found in Muttukadu lagoon.
Significance and Impact of the Study:  This study reveals that human enteric bacteria MK which is considered as nonpathogenic to fish, may become pathogenic to fish when it harbours this cationic factor. This cationic factor is found to be pathogenic to the fish M. cephalus leading to mortality. It was also found to be pathogenic to mice. Therefore, the shuttling of Ent. cloacae , harbouring cationic factor, between human and fish may be of human health importance.     

鲻幼鱼耗氧率、排氨率和窒息点的研究

为探讨鲻幼鱼的耗氧率、排氨率和窒息点,采用封闭流水式实验方法,在不同体质量、光照、放养密度、水流速度以及昼夜更替的条件下,测定鲻幼鱼的耗氧率和排氨率,并且观测体质量对幼鱼窒息点和窒息时间的影响。实验期间水温为19℃±1℃,盐度30,pH7.7。研究结果显示:鲻幼鱼的耗氧率随体质量增加而上升,其变化趋势可用幂函数方程表达:Y=0.4759X0.1878(R2=0.9454);光照对耗氧率的影响较大,对排氨率无明显影响;放养密度对耗氧率的影响差异显著(P0.05),对排氨率的影响差异极显著(P0.01);幼鱼的呼吸代谢旺盛时段在中午11∶00至夜间23∶00;流速对耗氧率和排氨率的影响差异均极显著(P0.01);不同体质量幼鱼窒息点和窒息时间的差异极显著(P0.01)。     

Melanization stimulating factors in the integument of the Mugil cephalus and Dicertranchus labrax

The pigment pattern expression resides in the chromatoblasts of the embryonic skin. The differentiation of these chromatoblasts is influenced by specific local factors such a melanization inhibiting factor (MIF) and a melanization-stimulating factor (MSF). We reveal the presence of these factors by means of a series of experiments on the skin of the marine species of fish Dicertranchus labrax and Mugil cephalus, each with different pigment pattern, the former having a light skin and the latter a darker one. Media conditioned by exposure to dorsal and/or ventral skin, stimulates the melanization of Xenopus laevis neural crest cells throughout a 3 day assay period. Similarly conditioned culture media tested on B16-F10 murine malignant melanocytes, revealed a considerable influence in enzymatic activities: dopachrome tautomerase (DCT), tyrosine hydroxylase and dopa oxidase. The use of media in a dose response basis suggests that the conditioned media may contain both melanophore stimulating and inhibiting factors. The results obtained may actually reflect the resultant activity of the two factors present.     

Luminous microflora associated with the fishes Mugil cephalus and Tachysurus arius

Abstract Luminous bacteria harboured in the skin, gill and gut of the fishes Mugil cephalus and Tachysurus arius were studies. Within the gut, the distribution of bacteria was studied regionwise, i.e., foregut, midgut and hindgut. In M. cephalus , maximum luminous bacterial population density was observed in the hindgut and minimum was found in the foregut. In T. arius , maximum luminous bacterial population density was recorded in the hindgut and minimum was found in the midgut. Luminous microflora associated with the host showed seasonal variation. Bacterial load of the surrounding medium and type of food governed the distribution of luminous microbiota in fish. Vibrio harveyi and V. fischeri were the two species identified, the former accounting for the majority of the isolates.     

Ontogenesis of osmotic regulation in the striped mullet, Mugil cephalus L.

The osmoregulatory capabilities of juvenile striped mullet, Mugil cephalus L ., of three size-groups (20–29, 30–39 and 40–9 mm s.l.) were compared in a series of six salinities ranging from fresh water to full sea water. The two smaller size-groups were able to tolerate instantaneous transfer from the brackish water in which captured, to all salinities but fresh water, while the 40–69 mm group were tolerant of instantaneous transfer to all experimental salinities. At high environmental salinities, the osmotic regulatory capabilities improved with growth in size to an apparently definitive condition in fish of 40–69 mm s.l. The smallest of these individuals were estimated to be about 7.5 months old. The osmotic regulatory capability in waters of low salinity had reached a definitive state with the development of tolerance to such salinities. The ontogenetic pattern for Mugil cephalus is virtually identical to that of the Atlantic salmon, Salmo salar .     

Dynamics of ciguatoxins from Gambierdiscus polynesiensis in the benthic herbivore Mugil cephalus: Trophic transfer implications

This study investigates ciguatoxin dynamics in mullet after controlled feeding of Gambierdiscus polynesiensis cells as a model to characterize the absorption, distribution, retention and accumulation of ciguatoxins into the second trophic level of southwestern Pacific coral reef ecosystems. Mullet (Mugil cephalus) were fed once every other day over a period of 16 days for nine toxic feedings, and ciguatoxin activity was assessed over time in blood and seven tissues using the Neuro2a assay. Within 3 h of feeding on G. polynesiensis cells, ciguatoxins attained maximal blood concentrations, indicating rapid absorption of toxins into the systemic circulation. The time course for distribution of the estimated total tissue burden of ciguatoxin closely followed the time course for blood toxin levels, indicating a rapid distribution of the ciguatoxins throughout the fish body. The large majority (95%) of the ciguatoxin ingested dose was eliminated from the examined fish tissues 24 h after a single toxic meal, indicating little retention potential for ciguatoxin. We found no evidence for ciguatoxin accumulation after nine repeated feedings spaced two days apart, indicating that mullet did not accumulate ciguatoxin. These results provide the first experimental evidence supporting the central tenet of Randall's food chain hypothesis that ciguatoxins enter the food chain by transfer from unicellular algae to herbivorous and detritus-feeding fish. We propose that a time-dependent transformation of oxopene ciguatoxins may be necessary for the concentration of ciguatoxin through higher trophic levels.     

Implication of somatolactin in the regulation of sexual maturation and spawning of Mugil cephalus

Specific antibody for chum salmon somatolactin (SL) was used for immunocytochemical investigation of SL cell activity of Mugil cephalus during the gonadal cycle in both natural habitat and captivity. The SL-immunoreactive cells showed strong and specific immunoreactivity to antichum salmon SL. The number of SL-immunoreactive cells increased, as did the secretory and synthetic activity during sexual maturation and spawning in the natural habitat. The SL cells were rather small and moderately immunoreactive in immature fish; they were enlarged, their numbers increased, and they frequently showed more SL immunoreactivity during gonadal development. In addition, during late stages of maturation, small cell size with more or less SL immunoreactive cells were noted, indicating an active release of SL granules. Prespawning females tended to have more enlarged SL cells with stronger immunoreactivity than equivalent males. The SL cells showed an increase in the secretory activity during spawning as indicated by small size and weak immunoreactivity. The SL cells of M. cephalus reared in captivity showed high activity. This may be due to the low concentration of calcium in fresh water. The gradual stimulation of SL synthesis and release during sexual maturation and spawning of M. cephalus suggest that SL may be involved in the control of some steps of reproductive processes, such as steroidogenesis, calcium metabolism, and energy mobilization.