A reference growth curve for nutritional experiments in zebrafish (Danio rerio) and changes in whole body proteome during development

Abstract

Zebrafish is one of the most used vertebrate model organisms in molecular and developmental biology, recently gaining popularity also in medical research. However, very little work has been done to assess zebrafish as a model species in nutritional studies in aquaculture in order to utilize the methodological toolbox that this species represents. As a starting point to acquire some baseline data for further nutritional studies, growth of a population of zebrafish was followed for 15 weeks. Furthermore, whole body proteome was screened during development by means of bi-dimensional gel electrophoresis and mass spectrometry. Fish were reared under best practice laboratory conditions from hatching until 103 days post-fertilization (dpf) and regularly fed ad libitum with Artemia nauplii from 12 dpf. A growth burst occurred within 9-51 dpf, reaching a plateau after 65 dpf. Fork length and body weight were significantly lower in males than in females from 58 dpf onwards. Proteomics analysis showed 28 spot proteins differently expressed through development and according to sex. Of these proteins, 20 were successfully identified revealing proteins involved in energy production, muscle development, eye lens differentiation, and sexual maturation. In summary, zebrafish exhibited a rapid growth until approximately 50 dpf, when most individuals started to allocate part of the dietary energy intake for sexual maturation. However, proteomic analysis revealed that some individuals reached sexual maturity earlier and already from 30 dpf onwards. Thus, in order to design nutritional studies with zebrafish fed Artemia nauplii, it is recommended to select a period between 20 and 40 dpf, when fish allocate most of the ingested energy for non-reproductive growth purposes.

Zebrafish pituitary gene expression before and after sexual maturation

“…Development from the juvenile to the sexual maturity stage marks the transition from a state of rapid body growth to a state of slow somatic growth (Gomez-Requeni et al 2010). Unexpectedly, the transcriptional levels of gh in the pituitary gland remained the highest among the pituitary transcripts without a significant change at 45 and 90 dpf (Table 2 and Fig.…”

“…Zebrafish grow rapidly from birth to w50 dpf when most individuals begin to allocate part of their dietary energy intake to sexual maturation, which coincides with a decrease in growth rates (Gomez-Requeni et al 2010). The pituitary gland is a key regulator of body homeostasis during development.…”

“…Under standard laboratory conditions, zebrafish normally exhibit a growth burst stage within 9-51 dpf, coinciding with the critical stage of their sex differentiation. Their growth rates usually significantly decrease after 65 dpf (Gomez-Requeni et al 2010). Numerous gene expression profiling studies have been carried out using different organs or tissues, but very few studies have addressed questions on the developmental changes in pituitary gene expression due to maturation and somatic growth processing in zebrafish.…”

Dietary Protein Source Influence on Body Size and Composition in Growing Zebrafish

“…3 Another recent work reports fish that appear to be significantly larger than those in the present study, with a final length of *33 mm and a body weight of 350 mg. 24 Whether strain differences partially account for these growth differences has not been evaluated. Given the larger starting and final lengths, 24 it would be of interest to determine if dietary composition differences produced similar growth responses in another zebrafish strain background or if earlier initiation of formulated feeds altered the growth parameters. Additionally, tank densities were different between the two studies, with the current study having three times the density of the previous work (e.g., current: *5.5 fish/L vs. *1.6 fish/L).…”

“…requirements may be predicted based on other nutrition studies using teleost models, [20][21][22][23] few nutrient requirement studies have been formally presented in the research literature for zebrafish. 3,24,25 Nevertheless, although zebrafish nutrition and obesity research is still developing compared with rodent models, 26 the information reported from decades of rodent nutrition research may be used to rapidly test dietary compositions for a variety of growth and eventual health-related outcomes.…”