Environmentally induced ontogenetic and phenotypic plasticity in zebrafish, Danio rerio (Hamilton 1822)

Fish are considered as a highly plastic group of organisms, capable of modifying their phenotype in relation to environmental conditions (Meyer 1987, Snyder & Dingle 1990, Swain & Foote 1990, Baker et al. 2005, Kristjansson, 2005, Sharpe et al. 2008, Gonda et al, 2009). The term “phenotypic plasticity” characterizes the ability of a single genotype to produce a variety of phenotypes, as a response to the different environmental conditions experienced during development. Environmentally induced phenotypic differences can be a result of differences in developmental timing and environmental factors may act upon the overall growth pattern, affecting the timing of developmental events and having long-term effects. Those uniform changes in the rate, or in the relative timing of developmental events, are defined by the term heterochrony (Rice 1997, McNamara 1997, Klingenberg 1998, Smith 2002, McNamara 2012, Odentaal & Adriaens 2014, Gunter et al. 2014). Ontogenetic time, age and developmental stages, are used as milestones in studies concerning growth and differentiation and that is because those two parameters already contain the functional concept of time in their definition and therefore in their practical application. So, since this study concerns the environmentally induced plasticity and heterochrony in zebrafish, one of the objects of this study turned to be the most accurate way of determining the ontogenetic stages of the developing fish, in dpf / dph or SL / TL. The length of the body was used as the most appropriate indicator of the ontogenetic stages and results were extracted and analyzed in relation to it. From there on, the main purpose of this work was to study the effect of developmental temperature (from fertilization up until the completion of the stage of metamorphosis) in zebrafish, Danio rerio (Hamilton, 1822) phenotypic plasticity. The effect of temperature was examined in the sex ratio, the body shape of zebrafish larvae and adults, the timing of the ontogeny of meristic characters and the expression of genes associated with development (igf1, npy, myog, mstna, tnni2a. 3, osteocalcin, mgp, eda, cryaa, pes) and sex determination, directly or indirectly (ar, dmrt1, sox9a, cyp19a1a, cyp19a1b, figla, bmp15, gdf9, hsd11b2, tp53). Gene expression was studies during development (ontogenetic gene expression profile) (NanoString technologies), and secondarily in tissues of adult male and female zebrafish (igf1, npy, myog, mstna, tnni2a.3, ar, dmrt1, sox9a, cyp19a1a, cyp19a1b, figla, bmp15, gdf9) (Real Time q-PCR). The effect of population density and co-effect of temperature and photoperiod was also examined in the SGR, in the sex ratio of zebrafish, the shape of the body of adult males and females (only under the influence of density) and the timing of the ontogeny of the meristic characters (only under the co-effect of temperature and photoperiod). The ultimate goal was the intergraded study (to the limits of the possible) of environmentally controlled phenotypic plasticity, under the influence of the above environmental factors, and mostly under the influence of the critical developmental temperature. Each experiment was conducted twice. The temperature effect (22, 28 and 32°C) on zebrafish plasticity was examined throughout the whole larval period, from the 1st dpf, up until ≈14mm TL. Results demonstrated a significant affect od temperature conditions in sex ratio, with the 22°C shifting the ratio in favor of males and differentiating statistically significant from the two warmer temperature regimes (p 0,05), while at 32°C increased photoperiod caused a significant increase in SGR (p 0,05), ενώ στους 32˚C η αύξηση της φωτοπεριόδου προκάλεσε σημαντική αύξηση του SGR (p<0,05). Οι παραπάνω παρατηρήσεις επιβεβαιώθηκαν και στις δύο πειραματικές επαναλήψεις. Σύμφωνα με τα αποτελέσματα, η θερμοκρασία και η φωτοπερίοδος συνεπιδρούν στο ρυθμό σωματικής αύξησης, με τον καθένα από αυτούς να ελέγχει τη δράση του άλλου. Μόνο στην θερμοκρασία των 22°C σε συνδυασμό με την φωτοπερίοδο 14:10 (L:D) και στη μία εκ των δύο πειραματικών επαναλήψεων, παρατηρήθηκε στατιστικά σημαντική διαφορά (G-test, p<0,05) στην αναλογία φύλου, με τα θηλυκά άτομα να είναι λιγότερα από τα αρσενικά (31% θηλυκά έναντι 69% αρσενικά zebrafish) (Εικόνα 4.4.2 1, Πίνακας 26). Τέλος, εξετάστηκε η οντογένεση των ακόλουθων μεριστικών χαρακτήρων: Αρχή κάμψης της νωτοχορδής (Flexion), εμφάνιση του εδρικού πτερυγίου (Anal), εμφάνιση του ραχιαίου πτερυγίου (Dorsal), ολοκλήρωση κάμψης της νωτοχορδής (Post-flexion), ολοκλήρωση του σχηματισμού της ουραίας διχάλας (Caudal) και εμφάνιση προπλασμάτων των κοιλιακών πτερυγίων (Abdominal). Εντός της ίδιας συνθήκης φωτοπεριόδου (14:10 L:D και 8:16 L:D), σχεδόν σε όλες τις περιπτώσεις, αύξηση της θερμοκρασίας από τους 22°C στους 28 ή στους 32°C, προκάλεσε επιτάχυνση της εμφάνισης – ολοκλήρωσης των εκάστοτε οντογενετικών χαρακτήρων. Με εξαίρεση την ανάπτυξη του εδρικού πτερυγίου στους 22°C, σε κάθε άλλη περίπτωση που παρατηρήθηκε στατιστικά σημαντική διαφορά μεταξύ των ίδιων θερμοκρασιών στις διαφορετικές συνθήκες φωτοπεριόδου, αυτή οφειλόταν σε καθυστέρηση της εμφάνισης ή της ολοκλήρωσης της ανάπτυξής τους στη μεγάλη φωτοπερίοδο, σε σχέση με τη μικρή

Growth and body composition of Zebrafish (Danio rerio) larvae fed a compound feed from first feeding onward : toward implications on nutrient requirements

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High Expression Levels of the Genes cyclin-A2 and glucocorticoid receptor Are Associated with High-Quality Embryos in Gilthead Sea Bream (Sparus aurata L.)

Identifying early egg-quality predictors is a major challenge in finfish hatcheries, and relevant research is now focused on the development of molecular markers. In our study, we examined whether fertilization rates and early morphological abnormalities in sea bream egg batches of high (HQ) and low quality (LQ) are associated with mRNA levels of cathepsin D, cathepsin Z, cyclin-A2, and glucocorticoid receptor. Additionally, we examined whether these early quality descriptors were associated with the development of skeletal abnormalities during the larval period. HQ egg batches were characterized by significantly higher rates of normal embryos (95.8 &plusmn; 2.3%) and lower rates of unfertilized (2.8 &plusmn; 1.0%) and abnormal eggs (1.3 &plusmn; 1.4%), compared to LQ (84.2 &plusmn; 0.8% normal embryos, 12.3 &plusmn; 12.3 unfertilized eggs, and 3.5 &plusmn; 1.4% abnormal eggs) (p &lt; 0.05, Mann&ndash;Whitney U test). Relative expression of cyclin-A2 and glucocorticoid receptor was found to be significantly higher in HQ embryos compared to those of LQ (respectively, p &lt; 0.01 and p &lt; 0.05, Mann&ndash;Whitney U test). No statistically significant differences were observed in the mRNA transcripts of cathepsin D and cathepsin Z (p &gt; 0.05, Mann&ndash;Whitney U test). Differences in the rate of skeletal abnormalities between the two quality groups of larvae were not significant (p &gt; 0.05, G-test), indicating that cyclin-A2 and glucocorticoid receptor may serve as reliable molecular markers for early prediction of fish egg quality but not for later larval stages

Effect of vitamin A on the skeletal morphogenesis of European sea bass, Dicentrarchus labrax (Linnaeus, 1758)

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