Fish Fertilizer Research Articles

Reproductive Biology and Quantity Evaluation of the Black-Striped Pipefish <i>Syngnathus abaster</i> (Eichwald, 1831) in the Zaporozhian Reservoir

The article presents the results of biology and ecology studies about the black-striped pipefish Syngnathus abaster (Eichwald, 1831) in the Zaporozhian Reservoir. Quantity and biomass of fish fingerlings and yearlings in different parts of the reservoir was determined. For the first time the reproductive indicators of pipefish in Zaporozhian Reservoir were investigated: the timing of spawning, fish fertility analysis, information on the number of embryos in the brood chamber of males were shown.

Reproductive Biology and Quantity Evaluation of the Black-Striped Pipefish <i>Syngnathus abaster</i> (Eichwald, 1831) in the Zaporozhian Reservoir

The article presents the results of biology and ecology studies about the black-striped pipefish Syngnathus abaster (Eichwald, 1831) in the Zaporozhian Reservoir. Quantity and biomass of fish fingerlings and yearlings in different parts of the reservoir was determined. For the first time the reproductive indicators of pipefish in Zaporozhian Reservoir were investigated: the timing of spawning, fish fertility analysis, information on the number of embryos in the brood chamber of males were shown.

Weed Management, Training, and Irrigation Practices for Organic Production of Trailing Blackberry: II. Soil and Aboveground Plant Nutrient Concentrations

Organic production of blackberries is increasing, but there is relatively little known about how production practices affect plant and soil nutrient status. The impact of cultivar (Black Diamond and Marion), weed management (nonweeded, hand-weeded, and weed mat), primocane training time (August and February), and irrigation (throughout the summer and none postharvest) on plant nutrient status and soil pH, organic matter, and nutrients was evaluated from Oct. 2012 to Dec. 2014 in a mature trailing blackberry (Rubus L. subgenus Rubus Watson) production system. The study site was certified organic and machine harvested for the processed market. The planting was irrigated by drip and fertigated with fish hydrolysate and fish emulsion fertilizer. Soil pH, organic matter content, and concentrations of soil nutrients, including ammonium-nitrogen (NH4-N), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), copper (Cu), manganese (Mn), and zinc (Zn), were greater under weed mat than in hand-weeded plots. Soil K and boron (B) were below recommended standards during the study, despite a high content of K in the fish fertilizer and supplemental B applications. Primocane leaf nutrient concentrations were below the N, K, Ca, and Mg sufficiency standards in ‘Black Diamond’ and were lower than in ‘Marion’ for N, phosphorus (P), Ca, Mg, S, B, and Zn in at least one year. In contrast, floricane leaves and fruit tended to have higher nutrient concentrations in ‘Black Diamond’ than in ‘Marion’. Weed management strategy affected many nutrients in the soil, leaves, and fruit. Often, use of weed mat led to the highest concentrations. Withholding irrigation postharvest had limited effects on plant nutrient concentrations. Primocane training time affected the nutrients in each plant part differently depending on year.

Production of viable trout offspring derived from frozen whole fish.

Long-term preservation of fish fertility is essential for the conservation of endangered fishes. However, cryopreservation techniques for fish oocytes and embryos have not yet been developed. In the present study, functional eggs and sperm were derived from whole rainbow trout that had been frozen in a freezer and stored without the aid of exogenous cryoprotectants. Type A spermatogonia retrieved from frozen-thawed whole trout remained viable after freezing duration up to 1,113 days. Long-term-frozen trout spermatogonia that were intraperitoneally transplanted into triploid salmon hatchlings migrated toward the recipient gonads, where they were incorporated, and proliferated rapidly. Although all triploid recipients that did not undergo transplantation were functionally sterile, 2 of 12 female recipients and 4 of 13 male recipients reached sexual maturity. Eggs and sperm obtained from the salmon recipients were capable of producing donor-derived trout offspring. This methodology is thus a convenient emergency tool for the preservation of endangered fishes.

MicroRNA profiles reveal female allotetraploid hybrid fertility.

BackgroundThe bisexual fertile tetraploid fish is important in biological evolution. Tetraploid fish fertility is the key factor for stable inheritance. Therefore, elucidating tetraploid fish fertility at the molecular level is essential. MicroRNAs regulate gene expression and are involved in many aspects of gonad development.MethodsTotal RNA was isolated using TRIzol, followed by constructing small RNA libraries. And then, the qualified libraries were sequenced with the HiSeq 2500 SE50 system. The obtained clean reads were analyzed to identify conserved and novel miRNAs, and evaluate the expression, and also predict the target genes. The differential expressions of miRNAs were confirmed by RT-PCR.ResultsIn this study, allotetraploid hybrid fish (4nAT) and diploid red crucian carp (RCC) ovaries were used to compare miRNA profiles. The results indicated that most of the highly expressed miRNAs were closely correlated with ovary maturation, and displayed no significant differences in expression. Moreover, 34 up-regulated and nine down-regulated miRNAs were found in 4nAT. The differentially expressed miRNAs were primarily involved in metabolism, defense mechanisms, and cytoskeleton production.ConclusionsThis is the first study to provide new epigenetic evidences for tetraploid fish fertility and phenotypic changes as a result of increased ploidy.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-015-0276-y) contains supplementary material, which is available to authorized users.

Developmental exposure of zebrafish (Danio rerio) to 17α-ethinylestradiol affects non-reproductive behavior and fertility as adults, and increases anxiety in unexposed progeny

Exposure to estrogenic endocrine disruptors (EDCs) during development affects fertility, reproductive and non-reproductive behavior in mammals and fish. These effects can also be transferred to coming generations. In fish, the effects of developmental EDC exposure on non-reproductive behavior are less well studied. Here, we analyze the effects of 17α-ethinylestradiol (EE2) on anxiety, shoaling behavior and fertility in zebrafish after developmental treatment and remediation in clean water until adulthood. Zebrafish embryos were exposed from day 1 to day 80 post fertilization to actual concentrations of 1.2 and 1.6ng/L EE2. After remediation for 82days non-reproductive behavior and fertilization success were analyzed in both sexes. Males and females from the 1.2ng/L group, as well as control males and females, were bred, and behavior of the untreated F1 offspring was tested as adults.Developmental treatment with 1.2 and 1.6ng/L EE2 significantly increased anxiety in the novel tank test and increased shoaling intensity in both sexes. Fertilization success was significantly reduced by EE2 in both sexes when mated with untreated fish of opposite sex. Progeny of fish treated with 1.2ng/L EE2 showed increased anxiety in the novel tank test and increased light avoidance in the scototaxis test compared to control offspring.In conclusion, developmental exposure of zebrafish to low doses of EE2 resulted in persistent changes in behavior and fertility. The behavior of unexposed progeny was affected by their parents' exposure, which might suggest transgenerational effects.

Liquid Corn and Fish Fertilizers Are Good Options for Fertigation in Blackberry Cultivars Grown in an Organic Production System

The impact of organic fertilizer source on the growth, fruit quality, and yield of blackberry (Rubus L. subgenus Rubus Watson) cultivars (Marion and Black Diamond) grown in a machine-harvested, organic production system for the processed market was evaluated from 2011 to 2013. The planting was established in Spring 2010 using approved practices for organic production and was certified in 2012. Plants were irrigated using a dripline under a woven polyethylene groundcover (weed mat) installed for weed management. Two sources of liquid fertilizer were evaluated: 1) a corn steep liquor and fish waste digestion blend (“corn”; 2.5N–1.1P–1.2K); and 2) a fish solubles and molasses blend (“fish”; 4N–0P–1.7K). Fertilizers were applied by fertigation through the drip system at rates of 56 kg·ha−1 nitrogen (N) per year in 2011–12 and 90 kg·ha−1 N in 2013. The impact of fertigation on drip system performance was evaluated with two maintenance options, “flushing” and “no flushing” of the driplines. Total yield differed among years, whereas fruit soluble solids concentration and firmness as well as floricane biomass at pruning showed a year × cultivar interaction. ‘Black Diamond’ had greater total yield and average fruit weight than ‘Marion’, but produced a greater proportion unmarketable fruit. There was no effect of fertilizer source on yield, fruit quality, primocane length, or primocanes/plant in any year with the exception of fruit weight, which was greater with corn than with fish. ‘Marion’ had a greater floricane biomass when fertilized with fish than with corn. Soil nutrients were within the recommended range, except for boron (B), which was below recommended levels. Only soil nitrate-N was affected by fertilizer source, which was greater in ‘Marion’ than in ‘Black Diamond’ when fertilized with fish. Primocane leaf tissue nutrient concentrations were within recommended levels for all nutrients, except for calcium (Ca) and B, which were below recommended standards in both cultivars. Primocane leaf potassium (K) and zinc (Zn) concentrations were greater with fish than with corn. There was no fertilizer source or maintenance effect on emitter flow rate of the drip system in either year. However, flow rates decreased an average of 4.5% in the first year and 19% in the second year. Overall, there were no differences between the fertilizers on plant growth, yield, or fruit quality, and both fertilizers were suitable for planting establishment.

A controllable on-off strategy for the reproductive containment of fish

A major impediment to the commercialization and cultivation of transgenic fish is the potential ecological risks they pose to natural environments: a problem that could be solved by the production of sterile transgenic fish. Here, we have developed an on-off reproductive containment strategy for fish that renders the offspring sterile but leaves their parents fertile. TG1 (Tol2-CMV-GFP-pA-CMV-gal4-pA-Tol2) and TG2 (Tol2-CMV-RFP-pA-5 × UAS-as/dnd-pA-Tol2) zebrafish lines were established using a GAL4/UAS system. While the parental lines remained fertile, in the hybrid offspring, GAL4 induced 5 × UAS to drive the transcription of antisense dnd, which significantly down-regulated endogenous dnd expression. This disrupted the migration of primordial germ cells (PGCs), led to their apoptosis, and resulted in few or no PGCs migrating to the genital ridge. This process induced sterility or reduced fertility in adult fish. This on-off strategy is a potentially effective means of generating sterile fish for commercialization while retaining fertility in brood stocks, and offers a novel method to mitigate the ecological risks of fish introductions.

Evaluation of an Organic Nitrogen Source in a Yellow Squash–Collard Rotation

In-season nitrogen (N) management is a common challenge in organic vegetable production. This is especially true when using polyethylene mulch combined with fertigation. Soluble organic N sources suitable for fertigation in organic vegetable production are needed. The objective of this research was to evaluate an organic fish fertilizer in a squash/collard rotation and to compare its effectiveness to inorganic sources. A 2-year crop sequence of yellow squash (Cucurbita pepo) and collards (Brassica oleracea var. acephala) was used. To eliminate the rotation order effect, the crops were switched each year: yellow squash-collard in Year 1 and collard-yellow squash in Year 2. Three N sources were used along with a zero N control: hydrolyzed fish fertilizer (HFF), inorganic N source with secondary and micronutrients (INORGWM), and inorganic N without secondary or micronutrients (INORGWO). Three N rates and a control were also included: 1) N at the recommended rate (152 kg·ha−1 for yellow squash and 110 kg·ha−1 for collards); 2) N at 80% of the recommended rate; 3) N at 60% of the recommended rate; and 4) a zero N control. Year 2012 yellow squash had a 30% higher yield when grown with inorganic N as compared with squash grown in HFF. Year 2012 collards had a 21% higher yield when grown with INORGWM as compared with collards grown in the HFF. In the second year, highest yields of collards were again produced in the INORGWM treatments followed by those grown in the HFF treatments. Second-year squash grown in the inorganic N treatments produced highest yields, and squash grown in the HFF had a 16% lower yield as compared with those grown in the two inorganic N sources. INORGWO produced lower marketable collard yields than INORGWM or HFF as a result of sulfur deficiency. Although yields were reduced in the crops grown in HFF treatments, the premium price and resultant profit associated with organic products were enough to offset the reduced yield. If growers can obtain the price premiums associated with organic produce, the use of HFF could be an economically feasible option in organic vegetable production.

Influence of Iodine on Efficiency of Fish

In accordance with the level of iodine consumption in the composition of granulated compound feedstuff given to the youngsters of the Lena sturgeon the influence of increased iodine norms on the synthesis of thyroxin, functional state of thyroid, fish fertility, feedstuff costs upon the amount of growth and economic efficiency has been marked.

Caracterización de parámetros espermáticos del pez vivíparo Jenynsia multidentata (Cyprinodontiformes: Anablepidae)

Several sperm parameters have been employed as useful tools to evaluate fish fertility. Within teleosts, approximately 3% of fish species are known to be viviparous. The Order Cyprinodontiformes includes several species with internal fertilization, and within this group most of the studies about sperm quality have been mainly focused on the Poeciliidae family. The livebearing fish Jenynsia multidentata (Anablepidae) inhabits an extensive area of the Neotropical region and it has been used as a useful fish laboratory model to evaluate the effects of xenobiotics through different biomarkers. The present work characterized the sperm of this species through a simple protocol of semen collection. Sperm population showed linearity greater than 89% and 70% of fish have a straight line and curvilinear velocity valued between 50 and 100 μm/s. Although 85% of individuals showed a proportion of live sperm higher than 60%, the male population had a high degree of heterogeneity in its sperm count. Morphometry analyses showed a total sperm and head lengths of 46.66 ± 2.06 μm and 3.46 ± 0.41 mm, respectively. A rather long midpiece region (9.12 ± 0.65 μm) was registered, which may indicate high energy-producing capabilities of the spermatozoa. This study established basic parameter values which could be useful for evaluating reproductive potential of J. multidentata populations.

MICROBIAL CONTENT OF ACTIVELY AERATED COMPOST TEA AFTER VARIATIONS OF INGREDIENTS OR PROCEDURES

Compost tea describes a procedure where compost is mixed with water. The mixture may be left to stand with minimal disturbance (also called “compost extract” or “steepage”) or actively supplied with oxygen by an aquarium pump to stimulate population growth of aerobic microbes. This project examined actively aerated compost tea. Over a three-year period, 25 experiments were conducted where a standard recipe was compared to variations of ingredients or procedures. Identification and count of microbial content was done by direct microscopy. The “standard recipe” was 15 L of tap water (pH 7.0), 485 g of composted yard waste, 285 g of commercial worm castings, 30 ml of humic extract, 30 ml of commercial kelp Ascophyllus nodosum and 30 ml of fish fertilizer. The procedure was to aerate water for 60 min in a commercial brewer, add ingredients which are removed after five hours, then maintain brewing for another 17 hours at room temperature of 20°C. Results indicate that longer brewing time increased protozoa activity; addition of humic acid stimulated fungi activity; addition of kelp stimulated protozoa activity; addition of fish fertiliser stimulated fungi activity and increased nutrient content; use of worm castings resulted in increased fungi content; and mixing protein food with compost ahead of brewing resulted in higher protozoa activity. However, replicated experiments were difficult as the microbial content changes continuously over time and it was not possible to accurately measure a large number of samples in a short period.

Production of AM fungus colonized seedlings under organic management: suitability of hydrolyzed fish vs. blood meal as options for N addition

The potential benefits of the arbuscular mycorrhizal (AM) symbiosis to crop growth and farm sustainability make utilization of AM fungus inoculum of particular interest to organic farmers. An important consideration in ensuring the colonization of vegetable seedlings by AM fungi during the greenhouse growth phase of production is supplying sufficient nitrogen and other nutrients for plant growth while limiting levels of phosphorus to avoid P-mediated inhibition of colonization. A greenhouse experiment was conducted to compare growth and AM fungus colonization of Allium porrum L. cv. Musselburgh seedlings in two organic potting media amended with high N and low P organic fertilizers vs. a chemical fertilizer solution known to produce well-colonized seedlings. Though amendment of the media with granular blood meal tended to produce the largest seedlings, formation of mycorrhizae was inhibited relative to 3 × per week additions of inorganic control or hydrolyzed fish fertilizers (4.5% vs. 28% and 16% of root length, respectively). A follow-up experiment in a controlled environment chamber demonstrated no detrimental effect of 3 × per week addition of blood meal in aqueous suspension relative to the chemical fertilizer. The incorporation of blood meal into the media had no impact on mycorrhizal development through the first 2 weeks, but inhibited development of new infection units and colonization of roots relative to the other treatments after 5 weeks (7% vs. 38% of root length). Proper choice of organic fertility amendment is essential to produce AM fungus colonized seedlings ready to take advantage of the symbiosis immediately upon outplanting.

Hydrolyzed Organic Fish Fertilizer and Poultry Litter Influence Total Phenolics and Antioxidants Content but Not Yield of Amaranth, Celosia, Gboma, and Long Bean

Dietary intake of a variety of vegetables is very important for disease prevention and may help in the treatment of certain maladies. Experiments were conducted to evaluate yield and the content of antioxidants and phenolics of vegetable Amaranth (Amaranthus hybridus), Celosia (Celosia argentea), Gboma (Solanum macrocarpon), and Long Bean (Vigna unguiculata) in response to poultry litter (PL) and a hydrolyzed fish fertilizer [Megabloom (MB)]. The experiments were conducted as a randomized complete block design with a four × three factorial treatment and four replications. The treatments were applied based on soil test recommendations in a single band 15 to 20 cm away from the plants 1 week after transplanting. Plants were harvested sequentially during the season as foliage and fruits became physiologically mature and once over at the end of the season. Species were analyzed for vitamin C content, total phenolics, and β-carotene content as well as antioxidant capacity. Organic amendments did not significantly influence biomass production, whereas species impacted fresh and dry biomass. Amaranth, Celosia, and Long Bean produced greater fresh and dry biomass than did Gboma. Vitamin C content was highest among Amaranth and Celosia plants receiving nitrogen–phosphorus–potassium (NPK) compared with the other two treatments, whereas that of Gboma was higher among plants receiving MB.

Sustainable Production of Marigold and Calibrachoa with Organic Fertilizers

Experiments were conducted to evaluate organic fertilizers in production of greenhouse-grown calibrachoa (Calibrachoa ×hybrida Llave & Lex) and marigold (Tagetes erecta L.) and nitrogen (N) leaching from containers during production. Calibrachoa was grown with five fertilizer treatments: one chemical, one organic-based, and three organic (liquid fish, oilseed extract, and a combination of oilseed extract and liquid fish). Marigold was grown with seven fertilizer treatments: one chemical and three organic (liquid fish, oilseed extract, and alfalfa pellets) used either alone or in combination. Chemical or organic-based fertilizers produced the best quality calibrachoa based on plant appearance and size. Liquid fish fertilizer produced healthy plants but smaller plants than those grown with chemical or organic-based fertilizers. Plants grown with oilseed extract were stunted and showed chlorosis. If oilseed extract was combined with liquid fish, the plants were similar to those grown with the chemical or organic-based fertilizers in size and quality. Chemical or liquid fish fertilizers produced the highest quality marigold based on plant appearance. Plants fertilized with alfalfa pellets were sparse and pale green. Oilseed extract produced the poorest growth and quality. If oilseed extract was combined with liquid fish or alfalfa, marigold plants were close in size and development to chemical-fertilized plants without nutrient deficiency and with some enhancement of nutrient levels in the leaves. The combination of alfalfa and liquid fish produced similar results. The highest N leaching resulted from plants fertilized by liquid fish, mostly in the form of ammonium nitrogen (NH4-N). Combining liquid fish with alfalfa or oilseed extract reduced the amount of N leached from the pots. The results suggest that organic fertilizers can be used successfully to grow commercial greenhouse crops but should be combined for good plant quality and environmental sustainability.

Sperm Attractant in the Micropyle Region of Fish and Insect Eggs1

In some animals, such as fish, insects, and cephalopods, the thick egg coat has a narrow canal-a micropyle-through which spermatozoa enter the eggs. In fish, there is no indication that spermatozoa are attracted by eggs from a distance, but once spermatozoa come near the outer opening of the micropyle, they exhibit directed movement toward it, suggesting that a substance exists in this defined region to attract spermatozoa. Since Coomassie Blue (CB) binds preferentially to the micropyle region in flounder, herring, steelhead, and other fish, it probably stains this sperm guidance substance. This substance-a glycoprotein based on lectin staining-is bound tightly to the surface of the chorion, but can be removed readily by protease treatment. Although fertilization in fish (flounder) is possible after removal of this substance, its absence makes fertilization inefficient, as reflected by a drastic reduction in fertilization rate. The sperm "attraction" to the micropyle opening is species specific and is dependent on extracellular Ca(2+). Eggs of some insects, including Drosophila, have distinct micropyle caps with CB affinity, which also may prove to assist sperm entry. Our attempts to fertilize fly eggs in vitro were not successful.

Ca2+ signaling during activation and fertilization in the eggs of teleost fish

Interest in the morphological and physiological events that take place during fertilization in fish eggs began as early as the late 1800s. In these initial studies, and up to the present day, fertilization has been investigated in a range of different fish species. In this short review, we focus on just one aspect of fertilization in fish; the role of Ca2+ signaling. Somewhat surprisingly, to date, the Ca2+ dynamics at activation/fertilization have been visualized in only two teleost species, the medaka (Oryzias latipes) and the zebrafish (Danio rerio), where their year-round breeding potential and small size, as well as the optical clarity of the eggs and ex utero fertilization, have made them the model of choice of researchers studying fertilization and early development. In these two species, activation/fertilization is accompanied by a single self-propagating Ca2+ wave, unlike the multiple regenerating waves reported for mammals, ascidians, certain amphibians (urodeles) and annelids. During medaka and zebrafish fertilization, the Ca2+ wave is initiated at the micropyle, the point of sperm/egg contact located at the animal pole, and then it propagates at ∼10–12μm/s to its antipode at the vegetal pole.

Effect of pH and cation concentrations on spermatozoan motility of sea trout (Salmo trutta m. trutta L.)

Environmental conditions during external fertilization in fish have a significant effect on spermatozoan motility (MOT) and fertilization ability. Even in the same family of fish, spermatozoa might differ in sensitivity to ions present in the external medium. Elucidation of such differences within a species would help to understand spermatozoan biology and to determine external conditions that would optimize spermatozoan MOT and successful fertilization. Objectives of the current study were to determine the effects of pH and of sodium, potassium, and calcium ion concentrations in the activation solution on sea trout spermatozoan MOT. Six parameters characterizing MOT (MOT, curvilinear velocity [VCL], linearity, amplitude of lateral head displacement, beat cross frequency, and duration of MOT) in spermatozoa activated in prepared buffers were traced by computer-assisted sperm analysis. Sea trout spermatozoa were motile over a wide range of pH values, and increasing pH did influence MOT, VCL, linearity, amplitude of lateral head displacement, and MOT duration. The optimum pH for sperm MOT was established at approximately 10. Increasing K+ ion concentration within the observed range caused a decrease in MOT and VCL. Spermatozoan movement ceased at 8 mM KCl concentrations. In Ca2+ buffers, sperm were motile within the range of 0 to 70 mM CaCl2 concentration; although beyond 8 mM concentration, VCL and MOT gradually declined. Spermatozoan aggregation was observed at the highest ion concentrations tested. Increasing CaCl2 concentration affected MOT pattern from initiation to termination of spermatozoan movement in a similar manner as changes associated with increasing pH. At concentrations of CaCl2 higher than 0.5 mM and in buffers with pH values 10 to 11, movement of spermatozoa was characterized by high initial linearity followed by its gradual reduction. In contrast to the effects of KCl and CaCl2, increasing NaCl concentration up to 90 mM Na+ concentration prolonged the duration of spermatozoan movement and, up to 60 mM Na+ concentration, slightly increased sperm velocity as well. Above the concentration of 90 mM NaCl, these parameters decreased; and at 240 mM of Na+, spermatozoa did not activate.

Transcriptional and proteomic profiling of flatfish (Solea senegalensis) spermatogenesis

The Senegalese sole (Solea senegalensis) is a marine flatfish of high economic value and a target species for aquaculture. The efforts to reproduce this species in captivity have been hampered by the fact that farmed males (F1) often show lower sperm production and fertilization capacity than wild-type males (F0). Our knowledge on spermatogenesis is however limited to a few studies. In a previous work, we identified by 2-D DIGE several potential protein markers in testis for the poor reproductive performance of F1 males. Therefore, the objectives of the present study were, first, to investigate changes in genes and proteins expressed in the testis throughout spermatogenesis in F0 males by using a combination of transcriptomic and proteomic approaches and, second, to further compare the testis proteome between late spermatogenic stages of F0 and F1 fish to identify potential indicators of hampered reproductive performance in F1 fish. We identified approximately 400 genes and 49 proteins that are differentially expressed during the progression of spermatogenesis and that participate in processes such as transcriptional activation, the ubiquitin-proteasome system, sperm maturation and motility or cytoskeletal remodeling. Interestingly, a number of these proteins differed in abundance between F0 and F1 fish, pointing toward alterations in cytoskeleton, sperm motility, the ubiquitin-proteasome system and the redox state during spermiogenesis as possible causes for the decreased fertility of F1 fish.

Physiological studies on the effect of copper nicotinate (Cu–N complex) on the fish, Clarias gariepinus, exposed to mercuric chloride

Female catfish, Clarias gariepinus, were collected from the Nile River at Assiut region, were divided into 7 groups. The first group was left as control, and the second was treated with mercuric chloride (MC) for 3 weeks following by normal water for 1 week. The third, fourth and fifth groups were provided by MC (150 μg/ l of water). This treatment was continued for 3 weeks. Then, the fish were received CN instead of MC, for 1 week, with 15 and 25 mg CN/100 g wet food. The fifth fish group received diet supplemented with vit E (α-tocopherol) (100 mg/kg wet diet), for 1 week, instead of MC treatment. Vitamin E was used as standard antioxidant drug. Following 3 weeks of normal ambient water, the sixth and seventh aquaria received only CN for 1 week, with 15 and 25 mg CN respectively/100 g wet food, respectively. At the end of the experiment, Samples of liver, kidneys (posterior part), gills (right gills) and ovary were excised. The measurement included the oxidative stress parameters: carbonyl protein and total peroxide and the antioxidant enzyme activities superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) in all selected organs. MC treatment induced harmful effect in fish, probably due to its enhancing effect on reactive oxygen species (ROS) production in fish organs especially the respiratory and osmoregulatory organs namely gills. The result suggests that this gill damage may exert hypoxic case, anoxia for different organs and some Cu excretion resulting in a magnification of ROS overproduction. Also, the observed oxidative stress in ovary tissue of MC-treated fish may affect fish fertility. The addition of CN in fish diets could protect the fish C. gariepinus against MC-induced oxidative damage showing recovery of fish organs. It could suggest that the detoxifying mechanism of action of CN is mainly due to its scavenging activity of free radicals rather than tissue healing.