1,720,965 research outputs found
The control of reproduction in finfish species through GnRH treatments
Full text linkFish in captivity can show some dysfunctions, at different levels, in the physiological processes of reproduction, due to
the lack of synthesis or release of gonadotropins (GtHs) by hypophysis. As a consequence, a worsening of quality and
quantity of spawned gametes, or a lack of egg and sperm spawning, can be observed. The farmers can act on fish reproductive
cycle manipulating the environmental parameters of rearing, the diet, the genetics or using GnRH treatments.
Nowadays, they are used mainly GnRH, synthesized in laboratory as analogues. These releasing factors, naturally produced
by hypothalamus, let to overcome the technological and biological limits of the “traditional” hormonal treatments
with hCG, being more effective, cheaper and easily available on market. This article makes a historical survey of the conditioning
treatments for fish reproduction and also considers the future perspectives of these treatments, examining the
topics that research will have to focus, in order to make these treatments common worldwide, in any hatchery and for
each farmed species of finfish
Comparative study on milt quality features od different finfish species
Full text linkThe aim of this research was to study the main sperm characteristics of three different finfish species. Twenty-one gilthead
sea bream (Sparus aurata), 20 brown trout (Salmo trutta, morpha fario) and 15 rainbow trout (Oncorhynchus
mykiss) male broodstocks, farmed under optimal conditions for each species and fed standard diets for broodstocks, were
manually stripped. Brown trout yielded small amounts of sperm (4.5 vs 18.13 ml) that were very concentrated (≅ 8.5 x
109 vs 1.24 x 109 Szoa/ml) with respect to the other species. The duration of spermatozoan motility for gilthead sea
bream sperm was significantly longer (almost 50 min), in comparison to the one-minute motility of Salmonids. Single
fatty acids of brown trout sperm were higher than in the other two species for almost all detected fatty acids. In particular,
eicosapentaenoic acid (EPA) was at least three times more concentrated in brown trout than in rainbow trout or gilthead
sea bream sperm (1238.3 μg/g vs 305.6 and 333.3 μg/g, respectively; P < 0.01). Saturated, polyunsaturated and
total unsaturated fatty acid classes were significantly higher in brown trout sperm than in the other two species - almost
double with respect to gilthead sea bream sperm and more than double in comparison to RT sperm (P < 0.01)
Effects of vitamin E and phosphatidylcholine on qualitative and quantitative parameters of rainbow trout (Oncorhynchus mykiss) milt
No full textThe aim of this work was to investigate the effects of vitamin E and phosphatidylcholine on rainbow trout
(Oncorhynchus mykiss) milt. One hundred and twelve rainbow trout (RB) broodstock (2n, 1030± 20g
body weight, male:female ratio = 50:50) were fed four isoproteic and isolipidic diets for 110 days. Diets
were differing for the type of vitamin premix and phosphatidylcholine supplied: Control (vitamin premix
without Vit. E, no phosphatidylcholine); Vit.E (a premix with Vit. E, no phosphatidylcholine); PhC, (vitamin
premix without Vit. E, phosphatidylcholine 2.5%); Vit.E +PhC, (vitamin premix with Vit. E and phosphatidylcholine
2.5%).
Sperm total volume, in sexually mature males (3+; 966±114g body weight), ranged between 18.57ml
(Control) and 34.31ml (Vit. E). Sperm density varied between 1.76x109 Szoa/ml (Control) and 1.16x109
Szoa/ml (Vit. E+PhC), while relative density (related to male body weight) tended to increase with Vit. E
(>50x109 Szoa/ml) and to reduce with Vit. E + PhC (85%
in all treatments, while motility duration was around 2.37min for Vit. E and Control reached only 0.97min.
After overnight storage (+4°C, for 18 hours) motility decreased, 75-80% in gamete motility and 3.39-
56.7% in time motility.
PhC dietary supplements significantly increased arachidonic acid contents of sperm with respect to
Control (>120 vs 73μg/ g), while Vit. E caused a huge increase in C20:3 n-3 (10.25 vs 2.27ppm).
DHA/EPA ratio was significantly lower in Control (>2; p<0.05), while n-3/n-6 ratio was significantly the
highest for Vit. E (9.46 vs <7.3)
The effect of dietary coconut oil on reproductive traits and egg fatty acid composition in rainbow trout (Oncorhynchus mykiss)
No full textTwo hundred and twenty rainbow trouts (IBW: 700 g) were randomly allotted to four tanks,
with a male/female ratio of 0.56. Fish were fed for 168 d with four experimental diets containing herring
oil, cod liver oil and coconut oil with the following inclusion rates: diet A: 12-1-0% respectively;
diet B: 6-1-6%; diet C: 0-1-12%; diet D: 0-0-13%. Irrespective of the dietary treatment, weight gains of
broodstocks were high (> 3 g/d) and FCR below 2. No significant difference was observed concerning
the total amount of eggs spawn, egg average weight (82.5 mg/egg) and lipid content (5.4 mg/egg).
However, the fatty acid profile of eggs was significantly affected by the dietary treatments. The content
of unsaturated fatty acids, particularly the n-3 fatty acid series (EPA and DHA) significantly decreased
with increasing levels of coconut oil in the diet
. The effects of coconut oil on reproductive traits and fatty acid eggcomposition of rainbow Oncorhynchus mykiss, Walbaum)
Full text linkTwo hundred and twenty rainbow trouts (IBW: 700 g) were randomly allotted to four tanks,
with a male/female ratio of 0.56. Fish were fed for 168 d with four experimental diets containing herring
oil, cod liver oil and coconut oil with the following inclusion rates: diet A: 12-1-0% respectively;
diet B: 6-1-6%; diet C: 0-1-12%; diet D: 0-0-13%. Irrespective of the dietary treatment, weight gains of
broodstocks were high (> 3 g/d) and FCR below 2. No significant difference was observed concerning
the total amount of eggs spawn, egg average weight (82.5 mg/egg) and lipid content (5.4 mg/egg).
However, the fatty acid profile of eggs was significantly affected by the dietary treatments. The content
of unsaturated fatty acids, particularly the n-3 fatty acid series (EPA and DHA) significantly decreased
with increasing levels of coconut oil in the diet
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Oregano (Origanum Vulgare) extract enhances zebrafish (Danio Rerio) growth performance, serum and mucus innate immune responses and resistance against Aeromonas Hydrophila challenge
No full textThere has been extensive research addressing the positive effects of medicinal plant extracts using food fish as animal models. The present research was an attempt to assess zebrafish viability, considering the 3Rs approach, as an animal model for dietary experiments for fish nutrition studies, particularly evaluating novel additives for further implications in food fish. We have found oregano (Origanum vulgare) extract to be remarkably effective on fish growth and the fish immune system, enabling fish to fight a bacterial invasion. This study evaluated the dietary effects of an ultrasound-assisted extract of Origanum vulgare on the growth, antioxidant and immune responses (serum and mucosal) and resistance of zebrafish (Danio rerio) against Aeromonas hydrophila. Four hundred and forty adult zebrafish were distributed into 12 tanks and fed 4 experimental diets including 0% (control), 0.5% (M1), 1% (M2) and 2% (M3) of the extract per kg-1 diet for eight weeks. Fish were then challenged with A. hydrophila and mortality was recorded for 10 days. Results revealed that the extract exerted potent effects on growth parameters of weight gain and specific growth rate. The feed conversion ratio was significantly lower in fish fed extract-incorporated diets. O. vulgare extract improved antioxidant and immune responses, resulting in less sensitivity to oxidative stress and a higher survival rate when challenged with A. hydrophila. Overall, the greatest effects were observed in individuals with 1% dietary inclusion of the extract. These results suggest that the extract from the plant Origanum vulgare possesses a great potential to be used in the aquaculture industry and that zebrafish is an appropriate model for nutrition studies
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