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广东省气象局网上分析统计数据显示，进入4月以来，全省平均降水量19．5毫米，较常年同期偏少9成，破历史同期最少记录。各地降水量在0．4（新兴）～77．1毫米（顺德）之间。全省有65个市县位居其历史同期最少降水量前5位，其中40个市县破或平其历史同期记录。与常年同期相比，全省降水偏少5成以上，其中75个市县偏少8成以上， 相似文献
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The sex ratio of the feral Southern catfish was reported to be about 1:1, while the fish obtained by artificial fertilization
were always female. Hence, we examined the possible influence of the micro-environment during artificial insemination (pH
of the ovarian fluid and concentration of the semen) and early development (feed, hatching temperature, and water) on the
sex ratio of Southern catfish fry. In order to examine the possibility of the occurrence of gynogenesis during artificial
propagation, cytological observations on the insemination processes and the artificial induction of gynogenesis were also
performed. However, no male fish were obtained even in these experiments, excluding the possibilities of these micro-environmental
changes on catfish sex ratio and the occurrence of gynogenesis during artificial propagation. Female-to-male sex reversal
was achieved by treatment with fadrozole (an aromatase inhibitor) and tamoxifen (an estrogen receptor antagonist). Histological
analyses on the gonadal development of both female and induced male fish were subsequently performed. Moreover, several genes
involved in sex differentiation, such as dmrt1, foxl2, and cyp19, and three subunits of gonadotropin (gth), i.e., gthα, lhβ, and fshβ, were isolated. Their expression patterns were studied under normal gonadal development and sex reversal conditions. The
results revealed that dmrt1, foxl2, and cyp19a were closely related to catfish sex differentiation, and the gth subunits were possibly related to ovarian differentiation and oocyte development. Taken together, we hypothesized that estrogen
was highly responsible for the ovarian differentiation and feminization of catfish fry under artificial propagation, although
the mechanism involved remains elusive. 相似文献
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Isao Tsutsui Poonmanee Kanjanaworakul Prapansak Srisapoome Dusit Aue-umneoy Kaoru Hamano 《Aquaculture International》2010,18(4):545-553
Growth of juvenile giant tiger prawn, Penaeus monodon Fabricius, was evaluated at an aquarium-scale in co-culture with a discarded filamentous seaweed, Chaetomorpha ligustica (Kützing) Kützing. Juveniles at different ages in days were examined, designated as J 16, J 44, J 58, J 93 and J 128, where
a 1-day-old juvenile (J 1) is equivalent to a 20-day-old post-larva (PL 20)). Juveniles at every age group grazed directly
on live C. ligustica, even those fed an artificial shrimp diet to satiation. Mean specific growth rate (SGR: % day−1) was higher in early age juveniles. Compared to mono-culture, significant differences in growth were observed at J 16 (4.44% day−1) and J 44 (1.60% day−1); however, no significant differences were recorded at J 58 (1.16% day−1), J 93 (0.75% day−1) or J 128 (0.45% day−1). It was concluded that co-culture of giant tiger prawn with C. ligustica has a dietary advantage, especially in early age juveniles. 相似文献
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Paiboon Panase Bunyanuch Kamee Sakditad Moungmor Prameda Tipdacho Jaturong Matidtor Nantaporn Sutthi 《Fisheries Science》2018,84(6):1025-1036
This study was conducted to evaluate the effects of Euphorbia hirta leaf extract on the growth performance, hematological and organosomatic indices of hybrid catfish, Clarias macrocephalus?×?C. gariepinus. The fish were treated with 0 (control), 300, 500 and 800 mg/kg (ppm) for 90 days. The weight gain, average daily growth rate, and specific growth rate were at significantly higher levels in fish from all the treatment groups on days 75 and 90, while the feed efficiency and protein efficiency ratio were consistently higher in fish from all the treatment groups from day 60 up until day 90. The feed conversion rate significantly decreased from day 60 until day 90 in all treatment groups when compared with the control group, and the survival rate was significantly different from day 30 until day 90; a consistently higher rate was observed in fish fed 800 mg/kg. The highest viscerosomatic index and intraperitoneal fat were observed in the group fed 500 mg/kg (p?<?0.05). The hepatosomatic index was significantly increased alongside increasing levels of E. hirta extract. The total white blood cell count in the control group was significantly higher on day 30, but on day 90 all the treatment groups showed higher levels. Hematocrit percentage was significantly different on days 30 and 90. Lymphocyte, eosinophil and thrombocyte levels were shown to be significantly different (p?<?0.05) when different groups of fish were compared. In conclusion, 300 mg/kg of E. hirta leaf extract could improve growth performance, hematological and some organosomatic indices in hybrid catfish. 相似文献
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Sergey Menzikov 《Fish physiology and biochemistry》2018,44(2):583-597
This paper presents a comparative study of the roles of Cl? and HCO3 ? in the functioning of the GABAAR-associated Cl?/HCO3 ?-ATPase of the plasma membranes of the olfactory sensory neurons (OSNs) and mature brain neurons (MBNs) of fish. The ATPase activity of OSNs and its dephosphorylation were increased twofold by Cl?(15–30 mmol l?1), whereas the enzyme from MBNs was not significantly affected by Cl?. By contrast, HCO3 ?(15–30 mmol l?1) significantly activated the MBN enzyme and its dephosphorylation, but had no effect on the OSN ATPase. The maximum ATPase activity and protein dephosphorylation was observed in the presence of both Cl?(15 mmol l?1)/HCO3 ?(27 mmol l?1) and these activities were inhibited in the presence of picrotoxin (100 μmol l?1), bumetanide (150 μmol l?1), and DIDS (1000 μmol l?1). SDS-PAGE revealed that ATPases purified from the neuronal membrane have a subunit with molecular mass of ~?56 kDa that binds [3H]muscimol and [3H]flunitrazepam. Direct phosphorylation of the enzymes in the presence of ATP-γ-32P and Mg2+, as well as Cl?/HCO3 ? sensitive dephosphorylation, is also associated with this 56 kDa peptide. Both preparations also showed one subunit with molecular mass 56 kDa that was immunoreactive with GABAAR β3 subunit. The use of a fluorescent dye for Cl? demonstrated that HCO3 ?(27 mmol l?1) causes a twofold increase in Cl? influx into proteoliposomes containing reconstituted ATPases from MBNs, but HCO3 ? had no effect on the reconstituted enzyme from OSNs. These data are the first to demonstrate a differential effect of Cl? and HCO3 ? in the regulation of the Cl?/HCO3 ?-ATPases functioning in neurons with different specializations. 相似文献
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1. Long‐term data sets on macro‐algae, sediment invertebrates, shorebirds and physical parameters are explored for the Ythan estuary, Scotland. 2. Coverage by macro‐algal mats has increased over the last 40 years with significant impacts on the distribution and abundance of benthic invertebrates and their shorebird consumers. Areas of the estuary worst affected by the mats now support fewer Corophium volutator, whilst the abundance of this and other species has increased in areas less affected by mats, possibly through enrichment by non‐local macro‐algal detritus. 3. Shorebird abundance increased between the early 1960s and the 1980s, possibly in response to enhanced invertebrate abundance in unaffected areas, but has declined since, as algal mats continue to spread. 4. The cause of the increased biomass of macro‐algae is contentious, but the present analysis shows that the increase is unlikely to be related to changes in the physical characteristics of the estuary, which appear to have remained fairly constant over at least the last 30 years. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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Ruilong Wang Yun Gao Lihong Zhang Yike Zhang Zhanqiang Fang Jianguo He Weimin Zhang Guangzhi Ma 《Fish physiology and biochemistry》2010,36(2):157-164
Vitellogenins (Vtgs), the precursors for the yolk proteins, are very important for the embryonic development of teleosts,
and have also been studied extensively as biomarkers for environmental estrogenic mimics. The cDNA for a Vtg was isolated
from the liver of the female white cloud mountain minnow (Tanichthys albonubes) by 3′- and 5′-RACE methods. It is 4,171 bp in full length, and encodes a putative protein of 1,326 amino acids. This putative
Vtg, designated as wcmmVtg, contains complete portions of LVI and PV, but lacks the C-terminal half of LVII and thus belongs
to type I vitellogenin. In addition to the liver of the female fish, wcmmVtg was also shown to be expressed in the ovary.
During ovarian development, the mRNA expression of wcmmVtg in both the liver and ovary was continuously increased from the
previtellogenic to late vitellogenic stages, but then decreased significantly at post-spawning stage. In the male fish, expression
of wcmmVtg mRNA was induced in the liver by treatment with E2 (10 and 100 ng/l) for 14 days. These results suggest that the Vtg originated from the ovary of the white cloud mountain minnow
may also contribute to the accumulation of yolk proteins during oocyte growth, and that the male white cloud mountain minnow
is sensitive to the estrogenic treatment in terms of Vtg mRNA expression, which could also be applied to monitor the environmental
estrogenic mimics. 相似文献
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Hideyuki Imai Fumi Kashiwagi Jin-Hua Cheng Tzyy-Ing Chen Katsunori Tachihara Tetsuo Yoshino 《Fisheries Science》2009,75(2):343-350
Two morphologically similar species of gizzard shad, Nematalosa japonica Regan and N. come (Richardson), sympatrically distributed off Okinawa Island, Japan, were examined using an allozyme locus (SOD*) and two nuclear polymerase chain reaction (PCR)-based DNA markers (ITS-1 and CaM), which provided diagnostic identification of each species. In addition, a multiplex PCR-based mitochondrial DNA (mtDNA)
marker (16S) was used to characterize the distribution of mtDNA haplotypes among specimens. The species composition of sympatric
and allopatric population samples from Tungkang, southern Taiwan, to Okinawa and the Shikoku Islands, Japan, were also examined.
Gizzard shad with hybrid genotypes were detected in three populations from Okinawa Island, with hybrid frequency ranging from
1 to 67%. A backcross level of 2% was detected in the dominant hybrid frequencies of one population sample only. Morphological
examination of hybrids showed intermediate forms, with hybrid indices of three meristic characters falling between those of
the parental species (range 39–53; mean 45). Although principal component analysis showed differences between N. japonica and N. come based on the first principal component scores, hybrids were difficult to identify. Accordingly, satisfactory identification
of species and hybrids could be achieved only using genetic tools. We also discuss the cause of hybridization and its relationship
with recently conducted reclamation on Okinawa Island. 相似文献
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Are hatchery‐reared abalone naïve of predators? Comparing the behaviours of wild and hatchery‐reared northern abalone,Haliotis kamtschatkana (Jonas, 1845) 
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下载免费PDF全文 Abalone populations have declined worldwide, generating interest in enhancement using hatchery‐reared individuals. In many cases, such restoration efforts have met with limited success due to high predator‐induced mortality rates. Furthermore, the mortality rates of outplanted hatchery abalone are often considerably higher than for wild individuals. This study uses northern abalone (Haliotis kamtschatkana) as a case study to determine whether hatchery‐reared abalone behave differently than their wild counterparts. In the field, outplanted hatchery‐reared abalone were significantly less responsive than wild abalone, in terms of number of abalone responding and intensity of response, to nearby movement and to physical contact with an inert probe. Also, when encountering a cue to which all abalone responded (a seastar predator), hatchery‐reared individuals remained subdued. Anti‐predator behavioural deficits in hatchery‐reared abalone were more pronounced in 4‐year‐old individuals than in 1‐year‐old individuals, suggesting an influence of either age or amount of time spent in the hatchery environment. These behavioural differences are expected to increase the vulnerability of hatchery‐reared abalone to predators, and are likely a major cause of their elevated predator‐induced mortality when outplanted. 相似文献
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Gonadal steroid and prostaglandin F2α (PGF2α) plasma levels were evaluated in successfully (SP) and unsuccessfully ovulated (UN) female Piaractus mesopotamicus. Forty-one females were injected with crude carp pituitary extract (0.6 and 5.4 mg kg?1 with a 24-h interval between the doses) and sampled to determine the plasma concentration of 17β-estradiol (E2), 17α-hydroxyprogesterone (17α-OHP), 17α,20β-dihydroxy-4-pregnen-3-one (DHP), PGF2α, and testosterone (T) after each injection (first—A1 and second—A2), and at the time of ovulation for SP and UN. Two clusters were obtained using multivariate analysis: 1—composed of all A1, all A2, and some UN; and 2—composed of all SP and some UN. Median values of E2 plasma levels were similar between clusters; however, plasma levels of T, 17α-OHP, DHP, and PGF2α of cluster 2 (predominantly formed by SP) were higher than those of cluster 1. Since cluster 2 contained all SP and females of this cluster presented higher levels of PGF2α, T, 17α-OHP, and DHP, here we evidently shown in an unprecedented manner that concomitant increased levels of these substances were associated with successful ovulation in this species, but such an increase was not determinant for successful ovulation due to the presence of some UN females in the same cluster 2. These findings highlight the unexplored potential of PGF2α to be used as an accessory tool for inducing successful ovulation for fish farming purposes. 相似文献
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为了实现由应试教育向素质教育的转变 ,适应现代社会对高素质人才的需要 ,必须加强素质教育 ,而实现素质教育的核心问题是提高课堂教学质量 ,因此 ,创设最优化课堂教学、促进学生个性健康发展和素质的全面提高是极其必要的。本文拟就这一问题 ,举《淡水生物学》教学中之例 ,谈谈粗浅的“五字法”。一、精指授课“精”和板书“精”。1、授课“精”。教师讲课时照本宣科 ,会使学生无所适从 ,觉得枯燥乏味 ,甚至于“丢了西瓜 ,拣了芝麻”。因此 ,教师应深入钻研教材 ,挖掘课程体系 ,找出每章、每节课的难点和重点 ,分清轻重、强弱 ,强化重点和… 相似文献
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Junming Deng Kun Wang Kangsen Mai Liqiao Chen Lu Zhang Haifeng Mi 《Fish physiology and biochemistry》2017,43(4):941-954
A feeding trial was conducted to evaluate the effects of replacing fish meal with rubber seed meal (RSM) on growth, nutrient utilization, and cholesterol metabolism of tilapia (Oreochromis niloticus × Oreochromis aureus). Five experimental diets were formulated with 0, 150, 300, 450, and 600 g kg?1 RSM replacing graded levels of fish meal, respectively. Each diet was randomly assigned to triplicate groups of 25 fish (initial average weight 65.3 g) per aquarium in a rearing system maintained at 29 ± 1 °C for 8 weeks. Dietary 150 g kg?1 RSM inclusion did not affect the weight gain and daily growth coefficient, whereas these were depressed by a further inclusion. Additionally, feed efficiency ratio and protein efficiency ratio were not affected by dietary RSM inclusion regardless of inclusion level. However, the inclusion of 450 and 600 g kg?1 RSM decreased the mid-intestinal trypsin, lipase, and amylase activities; the hepatic acyl-CoA/cholesterol acyl transferase; low-density lipoprotein receptor; and 3-hydroxy-3-methyl-glutaryl-CoA reductase activities. Similarly, dietary 600 g kg?1 RSM inclusion inhibited the plasma catalase and hepatic glutathione peroxidase activities. These results indicated that 150 g kg?1 RSM can be included in tilapia diets, whereas higher inclusion of RSM inhibited the growth rate, digestive enzyme activity, antioxidant capacity, and cholesterol metabolism. 相似文献
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Rhoda Mae C. Simora Shangjia Li Nermeen Y. Abass Jeffery S. Terhune Rex A. Dunham 《Journal of fish diseases》2020,43(12):1553-1562
Cathelicidins are a class of antimicrobial peptides (AMPs) known to possess rapid and direct antimicrobial activities against a variety of microorganisms. Recently identified cathelicidins derived from alligator and sea snake were found to be more effective in inhibiting microbial growth than other AMPs previously characterized. The ability of these two cathelicidins along with the peptides, cecropin and pleurocidin, to protect channel catfish (Ictalurus punctatus, Rafinesque) and hybrid catfish (I. punctatus ♀ × blue catfish, Ictalurus furcatus, Valenciennes ♂) against Edwardsiella ictaluri, one of the most prevalent pathogens affecting commercial catfish industry, was investigated. Cathelicidin-injected fish (50 µg ml−1 fish−1) that were simultaneously challenged with E. ictaluri through bath immersion at a concentration of ~1 × 106 CFU/ml had increased survival rates compared with other peptide treatments and the infected control. Bacterial numbers were also reduced in the liver and kidney of channel catfish and hybrid catfish in the cathelicidin treatments 24 hr post-infection. After 8 days of challenge, serum was collected to determine immune-related parameters such as bactericidal activity, lysozyme, serum protein, albumin and globulin. These immune-related parameters were significantly elevated in fish injected with the two cathelicidins as compared to other peptide treatments. These results indicate that cathelicidins derived from alligator and sea snake can stimulate immunity and enhance the resistance to E. ictaluri infection in channel catfish and hybrid catfish. 相似文献
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Yisheng Huang Xiaobo Wen Shengkang Li Wenjia Li Dashi Zhu 《Aquaculture International》2016,24(5):1229-1245
The present study aimed at determining the growth performance, feed utilization, body composition and antioxidant status of chu’s croaker (Nibea coibor) juveniles fed with increasing levels of dietary lipid: 6 % (D6), 9 % (D9), 12 % (D12) and 15 % (D15). Each diet was assigned to triplicate groups of fish in a total of 12 floating pens (300 fish, 25 fish per pen). After a 49-day growth trial, survival rate was not affected. D12 and D15 led to significantly higher specific growth rate (SGR). Fish fed D12 showed the highest protein efficiency ratio (PER), protein and lipid retention efficiencies (PER and LRE, respectively). The hepatosomatic and viscerosomatic indexes (HIS and VSI, respectively) increased, while feed conversion ratio (FCR) and feed intake (FI) decreased. Body protein, ash and muscle lipid contents were not significantly affected, but significantly higher body and liver lipid were noticed in fish fed with D15. Monounsaturated fatty acid (MUFA) was found to decrease compared to the experimental diets in muscle, while high unsaturated fatty acid (HUFA) was selectively accumulated in all treatments. Serum alanine transaminase (ALT, 14.13–22.53 U/L), aspartate transaminase (AST, 34.31–51.25 U/L), cholesterol (CHO, 2.02–3.03 mmol/L) and triglyceride (TG, 5.61–8.50 mmol/L) were correlated with increasing dietary lipids. Liver malate dehydrogenase (MDA, 3.32–6.67 mmol/L) and superoxide dismutase (SOD, 42.69–52.86 U/mg prot) increased with dietary lipids, while total antioxidant capacity (t-AOC, 1.08–3.50 U/mg prot) decreased. Polynomial regression analyses between SGR and dietary lipid levels showed that the optimal dietary lipid requirement of chu’s croaker is 12.9 % of dry matter. 相似文献
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Imtiaz Ahmed 《Fish physiology and biochemistry》2010,36(4):1133-1143
An 8-week growth study was conducted to determine the effect of ration level, energy, and protein maintenance requirement
of catfish, Heteropneustes fossilis–Bloch, fingerling (7.90 ± 0.55 cm; 3.10 ± 0.28 g) by feeding casein–gelatin-based purified diet (40% CP; 3.61 kcal g-1 GE)
at six ration levels 1–6% of BW/day, at 0800 and 1700 h, in triplicate, with 20 fish per trough fitted with water flow-through
system of volume 55 L. Maximum live weight gain, best feed conversion ratio (FCR), best specific growth rate (SGR), and highest
protein efficiency ratio (PER) were evident for ration levels of 4–5% body weight. However, second-degree polynomial regression
analysis for weight gain, FCR, PER, protein, and energy retention data indicated that the break-points occurred at 5.08, 4.18,
4.05, 4.16, and 4.17% BW/day, respectively. Significantly (P < 0.05) higher body protein content was recorded at 4 and 5% rations. While a linear increase in body fat content with inverse
relationship in moisture content was evident with increasing rations. Ash content remained insignificantly (P > 0.05) low at higher rations. Protein and energy retention values also produced significant (P < 0.05) differences. Based on the results obtained, it is recommended that feeding in the range of 4 to 4.5% BW/day, corresponding
to 1.60–1.80 g protein and 14.46–16.27 kcal energy g100 g−1 of the diet/day is optimum for the growth and efficient feed utilization of H. fossilis, while 2–3% ration levels (0.80–1.20 g protein and 7.23–10.84 kcal energy) suggest that these amounts approximate to the maintenance
requirement of this fish. 相似文献
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The GreenshellTM mussel, Perna canaliculus, is a commercially important species forming New Zealand’s largest aquaculture export product. Losses of P. canaliculus spat from culture ropes between larval settlement and the time mussels reach initial reseeding size (c. 10 mm) are common. To test whether water velocity affects growth and retention of post-settlement P. canaliculus spat, and whether there is a threshold effect of increasing velocities on spat migration, a laboratory-based experiment was
conducted. Spat were grown for 8 weeks in experimental tanks on culture ropes at four velocities typical of velocities within
mussel farms (40, 10, 4, and 1 cm s−1). Spat migration was observed at all the velocities tested, but the number of spat migrating decreased as water velocity
increased. Spat retention was highest at the 40 cm s−1 velocity. Mean spat size increased significantly with increasing water velocity. At the highest velocity tested (40 cm s−1), migration increased as the spat grew suggesting that migration was density-driven. The results of this experiment indicate
the potential for mussel farmers to reduce seeded spat loss and to increase the growth rate of spat by modification of the
water flow within their farms, or placement of seeded ropes in locations of certain existing water velocities, and indicate
that velocities in the range 15–40 cm s−1 promote higher spat growth and spat retention for P. canaliculus. 相似文献