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  • 1
    Electronic Resource
    Electronic Resource
    The influence of phytoestrogens and oestradiol-17β on growth and sex determination in the European eel (Anguilla anguilla) (2004)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 35 (2004), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Under aquaculture conditions, European eels (Anguilla anguilla) produce a high percentage of males (80–95%) that normally stop growing at 100–200 g. Females continue to grow to 500–750 g and obtain higher market value. Therefore, increasing the percentage of females in a population would be beneficial to the culture of eels. The present study was carried out in order to examine the effect of oestradiol and phytooestrogens on sex differentiation and growth rate of eels. Juvenile European eels with undifferentiated gonads were fed pellets containing oestradiol-17β (E2) or phytooestrogens for 100–150 days. Feeding E2 resulted in 50–61% increase in body weight compared with the control. Oestradiol-17β and phytooestrogens both elevated significantly the percentage of females in the population. Feeding E2 at 20 mg kg−1 feed resulted in 70% females, while lower concentration of E2 (2 mg kg−1) resulted in only 30% after 100 days (Experiment 1). The same dose given for 150 days (Experiment 2) resulted in 88% females, indicating that both, the concentration and duration of E2 treatments had a significant effect on sex differentiation. Fish fed genistein at 2 mg kg−1 for 100 days, resulted in 55% of females, but at a higher dose of 20 mg kg−1 there were only 15% females. These results demonstrate that phytooestrogens can be used as alternatives to gonadal steroids for sex manipulation in eels, but the optimal concentrations and duration are still to be determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2109.2004.01129.x
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  • 2
    Electronic Resource
    Electronic Resource
    Application of RAPD and cytochrome b sequences to the study of genetic variations in F1 and F2 generations of two different strains of guppy (Poecilia reticulata, Peter 1854) (2004)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 35 (2004), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The DNA of two laboratory strains of guppy (Poecilia reticulata), Black Yellow (BYS) and Red Flame (RFS), was studied with respect to their colour differences, in two generations (F1 and F2). Their varying morphological colours were related to their cloned fragments of cytochrome b mitochondrial DNA (mtDNA) and random-amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). The F1 generation was characterized by various forms. The male BYS could be divided into 68% having black–yellow tails and 14% having black–yellow–red tails. The other variations were found in very low percentages. The percentage of black–yellow-tailed males increased to 85 in the F2 generation, and the percentages of the various other forms consequently decreased. Only 63% of BYS males had black–yellow dorsal fins in the F1 generation, but this percentage increased to 84 in F2. Compared with the males, fewer variations were found in female colour patterns in the F1 generation. A high percentage of BYS females (81%) colour was found with no significant increase in the F2 generation. However, variations decreased in the F2 females. On the other hand, a very high variation was found in female fins in the F1 generation: only 32% were of BYS colour and 25% had no-colour fins. However, a significant increase in BYS colour was found in the F2 generation (61%) and 39% had no colour. The variation in RFS was lower than BYS in the F1 generation: 81% of the F1 males had red–yellow tails with colour, 46% of the fins were yellow and 36% were red–white. In females, a very high percentage (84%) had red–yellow tails and 76% had no-colour dorsal fins. Mitochondria DNA markers and genomic DNA were studied in various laboratory strains. In the clone of the fragments of cytochrome b, the bands correlated to the colour phenotype. A fragment of the cDNA sequence was determined from a 268-bp cloned with fragments of the guppy cytochrome b mtDNA gene. The genes varied for the two strains in only two base pairs, starting at the nucleotide position 171 and ending at position 174. Three primers showed good results in the RAPD-PCR and were found suitable for the study of DNA variations in guppy. The high variation detected in BYS, in comparison with RFS, was reflected by changes in band-sharing (BS) values ranging from 0.66 to 1, versus 0.8 to 1 in RFS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2109.2004.01071.x
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  • 3
    Electronic Resource
    Electronic Resource
    Growth and behaviour of six species of amphibian larvae in a winter pond in Israel (1986)
    Springer
    Hydrobiologia 140 (1986), S. 5-10 
    Details
    ISSN: 1573-5117
    Keywords: growth ; behaviour ; tadpoles ; niches ; pond
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of different ecological niches on growth and behaviour of larvae of four frogs (Bufo viridis, Hyla arborea, Pelobates syriacus, Rana ridibunda), and two salamanders (Salamandra salamandra and Triturus vittatus) found in a winter pond was studied. S. salamandra, T. vittatus, R. ridibunda and B. viridis were found most of the time on the bottom of the pond. However, H. arborea tadpoles were found throughout the pond and were usually sedentary, as compared with P. syriacus which moved up and down constantly. S. salamandra, T. vittatus, R. ridibunda and R viridis tadpoles from the bottom of the pond grew faster than the tadpoles from the surface of the pond. However, tadpoles of H. arborea and P. syriacus growing at the bottom or on the surface developed at similar rates. The invertebrate biomass increases during the summer and was higher at the bottom of the pond than at the surface. However the amount of chlorophyll a was about the same at the surface and at the bottom of the pond. S. salamandra and T. vittatus tadpoles feed on various types of of invertebrates, R. ridibunda and H. arborea and B. viridis tadpoles feed on vascular plants and algae, and P. syriacus tadpoles feed on both invertebrates and plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00006723
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of dietary carbohydrates and temperatures on slow growing juvenile eels Anguilla anguilla (1987)
    Springer
    Environmental biology of fishes 18 (1987), S. 149-154 
    Details
    ISSN: 1573-5133
    Keywords: Fish ; Nutrion ; Corn starch ; Glucose ; Diet ; Protein ; Lipid ; Body composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis The influence of the level of carbohydrate in a purified diet on the growth of slow-growing Anguilla anguilla maintained at different temperatures was examined. The average weight increase of eels maintained at temperatures of 25° or 27° C and fed a diet containing 20% or 30% glucose, was significantly higher than the mean weight increase of eels maintained at the same temperature but fed a diet containing soluble corn starch, at the same percentages. There was no significant difference in the mean weight of slow growing eels fed 10%, 20% and 30% soluble corn starch or 10% glucose. There was no significant difference in protein content (wet weight) among the experimental groups. However, elvers that were fed a high percentage of carbohydrates (glucose or starch) and maintained at 27° C had a higher percentage of lipids in body weight compared with the other experimental groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00002603
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  • 5
    Electronic Resource
    Electronic Resource
    Food composition of the fish community in Lake Agmon (1998)
    Springer
    Hydrobiologia 380 (1998), S. 49-57 
    Details
    ISSN: 1573-5117
    Keywords: Fish community ; Lake Agmon ; freshwater ; feeding habits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Agmon was created in the Hula Valley in Israel, in the northern part of the dried-up Hula Lake site, in summer, 1994. Samples of fish at ten stations were taken by electroshocker once a month, from January to December, 1996. The fish species whose food composition in the gut was examined in this study were: Tilapia zillii, Gambusia affinis, Clarias gariepinus, Cyprinus carpio, Pseudophoxinus kervillei, Acanthobrama lissneri, Hemigrammocapoeta nana and Oreochromis aureus. Food components were determined qualitatively and quantitatively. Assessment of the organism biomass in the gut contents was based on available data of phytoplankton and zooplankton. The food of G. affinis changed during the year, consisting high level of algae in winter and spring, and insects and crustaceans in summer. In T. zillii, a high percentage of algae were found in winter, and a high percentage of plants in summer. The food of H. nana consisted mainly of phytoplankton, but included high plants during most months; P. kervillei ingested mainly insects and crustaceans, with a high percentage of Daphnia spp.; and the diet of C. gariepinus comprised fish and invertebrates species, which varied with the seasons. C. carpio ate mainly invertebrates; O. aureus are vegetarian, and A. lissneri fed on both animals and plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003225210226
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of 3,3′,5-triiodo-L-thyronine and 17-α-methyltestosterone on growth and body composition of the glass stage of the eel (Anguilla anguilla L) (1986)
    Springer
    Fish physiology and biochemistry 1 (1986), S. 145-151 
    Details
    ISSN: 1573-5168
    Keywords: methyltestosterone ; thyroid hormone ; growth ; protein ; fat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study was undertaken to determine the influence of orally administered 3,3′,5-triiodo-L-thyronine (T3) or 17-α-methyltestosterone (MT) on growth and body composition of the eel (Anguilla anguilla L.) during the glass stage. Elvers receiving 20 or 40 ppm of T3 in the food weighed significantly more (P 〈 0.05) than controls. However, after 61 days of treatment a dosage of 60 ppm was not efficacious. Terminal percentages of body protein were significantly lower (P 〈 0.05) in elvers that received 20 ppm or 40 ppm T3 in their diets, than in the control. Crude body fat content was higher (P 〈 0.05) in elvers receiving 20 ppm (29% fat) or 40 ppm (28% fat), than in the controls (26% fat). Compared to the control, diets containing T3 at 20 or 40 ppm increased the body glucose concentration. Glass eels fed a diet containing 1 or 10 ppm MT grew significantly more slowly (P 〈 0.05) than the controls. Total body protein content was higher (P 〈 0.05), but total body crude fat content was lower (P 〈 0.05) in elvers fed a diet with 1 or 10 ppm MT compared to the controls. Total body glucose concentration of elvers administered 10 ppm MT was significantly lower (P 〈 0.05) than that of the control groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02290255
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of insulin in the diet on the growth of European eels (Anguilla anguilla L.) (1992)
    Springer
    Fish physiology and biochemistry 10 (1992), S. 223-227 
    Details
    ISSN: 1573-5168
    Keywords: eel ; insulin ; growth ; diet
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of oral administration of insulin, in various concentrations, on the growth of European eels (Anguilla anguilla L.) was studied. In order to determine whether the insulin penetrated through the stomach or gills to the blood system, 5 ml insulin, suspended in an 0.6% solution of NaCl, was inserted via the mouth of eels, and the insulin content in the blood measured by radioimmunoassay immediately, and at one and two hours after administration. A control group was given 0.6% NaCl alone. Significantly increased levels of insulin in the blood plasma were found in eels which received high insulin concentrations compared to the control group. Eels administered 20 ppm and 40 ppm insulin in the diet grew significantly faster than a control group fed a diet without insulin, and a group fed 5 ppm insulin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00004516
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  • 8
    Electronic Resource
    Electronic Resource
    Distribution of amphibian larvae in Israeli habitats with changeable water availability (1999)
    Springer
    Hydrobiologia 405 (1999), S. 49-55 
    Details
    ISSN: 1573-5117
    Keywords: biotic ; abiotic ; pond ; stream ; niche ; adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Forty-one amphibian habitats of various types in northern Israel were examined, in which water availability ranged from one month in the year to all year round. Larvae of all six species of amphibians native to the region, Salamandra salamandra, Triturus vittatus (Urodela), Hyla arborea, Bufo viridis, Rana ridibunda and Pelobates syriacus (Anura), were studied. The distribution of the species was governed by biotic and abiotic factors in the habitats, but not by the type of water body. Thus, larvae of all six species were found in temporary winter ponds, but only Salamandra and Bufo in streams and springs during the winter, and Rana during the summer. Ambient temperature, duration of water availability and elevation of the water body were major factors in species distribution. Species distribution also varied according to season. Species diversity increased from winter to summer. The growth rate of small larvae was found to be slower than that of larger larvae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003796820900
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  • 9
    Electronic Resource
    Electronic Resource
    Amphibian tadpole interaction in a winter pond (1982)
    Springer
    Hydrobiologia 96 (1982), S. 3-7 
    Details
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Six species of amphibian tadpoles (Bufo viridis, Hyla arborea, Pelobates syriacus, Rana ridibunda, Salamandra salamandra and Triturus vittatus) were studied during winter and summer in a winter pond. S. salamandra emerged immediately after the pond was filled by rain in winter. In spring and summer T. vittatus tadpoles were found. B. viridis tadpoles were found in the Sasa pond during spring and R. ridibunda tadpoles during summer, until the pond dried up. P. syriacus and H. arborea tadpoles, however, were found throughout spring and summer. The diversity of the tadpole species was elevated from April to June and then decreased until August. The distribution of the amphibian tadpoles in Sasa pond is explicable by their different adaptations to temperature and food.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00006274
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