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The effects of three medicinal plants in the feeds of juvenile Nile tilapia (Oreochromis niloticus) were investigated on growth, survival, immunity, and digestive histology at various inclusion levels: (A) Guiera senegalensis at 0, 1, 2, 4, and 8%; (B) Pluchea odorata at 0, 0.5, 1, 2, and 4%; (C) Piliostigma reticulatum at 0, 1, and 2%; and (D) a mixture of the three at 0, 1, and 2%. After 28 days of feeding, fish were infected with Aeromonas hydrophila for 12 days. The results showed that, except for G. senegalensis, the inclusion of the medicinal plants, alone or combined, enhanced the immune response. The diet with 4% P. odorata significantly increased plasma lysozyme and bactericidal activities without affecting feed conversion efficiency or growth. Despite improved immunity, none of the treatments enhanced post-infection survival rates. However, fish fed the 1% mixture showed healthier livers and intestines, with reduced cell swelling and normal lipid deposits, followed by the 2% mixture and the control. These results highlight the potential benefits of incorporating P. odorata and the plant mixture into the diets of Nile tilapia juveniles for enhancing their immune response against A. hydrophila. [ABSTRACT FROM AUTHOR]

The appearance of the pseudo-albino phenotype was investigated in developing Senegalese sole (Solea senegalensis, Kaup 1858) larvae at morphological and molecular levels. In order to induce the development of pseudo-albinos, Senegalese sole larvae were fed Artemia enriched with high levels of arachidonic acid (ARA). The development of their skin pigmentation was compared to that of a control group fed Artemia enriched with a reference commercial product. The relative amount of skin melanophores, xanthophores and iridophores revealed that larval pigmentation developed similarly in both groups. However, results from different relative proportions, allocation patterns, shapes and sizes of skin chromatophores revealed changes in the pigmentation pattern between ARA and control groups from 33 days post hatching onwards. The new populations of chromatophores that should appear at post-metamorphosis were not formed in the ARA group. Further, spatial patterns of distribution between the already present larval xanthophores and melanophores were suggestive of short-range interaction that seemed to be implicated in the degradation of these chromatophores, leading to the appearance of the pseudo-albino phenotype. The expression profile of several key pigmentation-related genes revealed that melanophore development was promoted in pseudo-albinos without a sufficient degree of terminal differentiation, thus preventing melanogenesis. Present results suggest the potential roles of asip1 and slc24a5 genes on the down-regulation of trp1 expression, leading to defects in melanin production. Moreover, gene expression data supports the involvement of pax3, mitf and asip1 genes in the developmental disruption of the new post-metamorphic populations of melanophores, xanthophores and iridophores. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the effects of vitamin A levels in the larval diet of Dicentrarchus labrax, (a) on the shape of juvenile skeleton and (b) on the development of pelvic fins. To exclude the side-effects of skeletal abnormalities on skeleton shape, morphometric analysis was performed on normal individuals only. Geometric morphometric analysis revealed a significant effect of larval nutrition on the shape of juvenile skeleton (Wilk's λ=0.0188, P<0.001), 55 days after the application of the different nutritional regimes. Between-groups shape differences mainly concerned the position of anterior dorsal pterygiophore, which was associated with a significant ( P<0.05) increase of the number of dorsal lepidotrichia and hard spines at low levels of vitamin A (3-9 × 10 IU kg dry food). At the lowest vitamin A levels (3 × 10 IU kg dry food), the development of pelvic fins was abnormal, with severe bilateral (44±10%, mean±SD) or unilateral (22±9%) lack of the fin lepidotrichia, hard spines and their supporting elements. In the 82-94% of the unilaterally deformed individuals, deformation concerned the left pelvic fin. Concerning the shape of pelvic fins in the normally developed individuals, results demonstrated a significant effect of nutritional conditions on the size and position of all the elements of the pelvic fin area (basipterygium, lower metacleithrum, cleithrum, scapula) (Wilk's λ=0.3087, P<0.001). Our results demonstrate a significant nutritionally driven phenotypic plasticity in D. labrax, with dietary levels of vitamin A determining the skeleton shape and the left-right symmetry of pelvic fins. [ABSTRACT FROM AUTHOR]

Abstract: The influence of dietary vitamin D3 (VD3) on survival, growth and morphogenesis during the larval development of European sea bass (Dicentrarchus labrax) was evaluated until 45days post hatching. Diets contained 4% of the standard vitamin mix (VM) recommended by the National Research Council (NRC) and incorporated 0, 19.2, 38.4, or 140IU of VD3 per gram of diet to give VD-0, VD-1, VD-2 and VD-3 dietary treatments, respectively. The present study revealed for the first time an impact of dietary VD3 on the sea bass digestive system ontogenesis that consequently conditioned the ossification process and morphogenesis. All dietary VD3 levels were in the “adequate range” based on larval survival. Nevertheless, growth, intestinal maturation and ossification at the end of the larval stage were harmed by the minimum dose of VD3 tested and resulted in the appearance of malformations. VD-2 and VD-3 groups showed satisfactory growth and ossification levels at the end of the larval period. However, results of enzymatic activity and expression of genes involved in the VD3 pathway (bone morphogenetic protein 4, osteocalcin, vitamin D receptors and transient receptor potential cation channel-subfamily V, member 6-) gave evidence of complications during the ossification process as revealed by the high percentage of deformed larvae. A VD3 level of 19.2IU/g diet appeared necessary to obtain harmonious larval morphogenesis. [Copyright &y& Elsevier]

The number of sources of anthropogenic magnetic and electromagnetic fields generated by various underwater facilities, industrial equipment, and transferring devices in aquatic environment is increasing. These have an effect on an array of fish life processes, but especially the early developmental stages. The magnitude of these effects depends on field strength and time of exposure and is species-specific. We review studies on the effect of magnetic fields on the course of embryogenesis, with special reference to survival, the size of the embryos, embryonic motor function, changes in pigment cells, respiration hatching, and directional reactions. We also describe the effect of magnetic fields on sperm motility and egg activation. Magnetic fields can exert positive effects, as in the case of the considerable extension of sperm capability of activation, or have a negative influence in the form of a disturbance in heart rate or developmental instability in inner ear organs. [ABSTRACT FROM AUTHOR]

A radioactive soluble model protein for studies of protein digestion, absorption and amino acid (AA) metabolism in larval fish was successfully produced in Atlantic salmon by oral administration of uniformly [U]-14C-labelled amino acids followed by blood sample withdrawal (48 h post-administration) and purification. The salmon serum protein (14C-SSP) was characterised in terms of the protein composition and specific activity of its amino acids. Most radioactivity was found in the three most abundant serum proteins, which had apparent molecular weights of 65, 75 and 120 kDa, respectively, of which labelling was found in all the amino acid residues of the SSP that were analysed. The digestibility of the 14C-SSP was tested by in vivo tube feeding using early stages of Atlantic halibut and was found to be more efficiently digested and utilised than the 14C-methylated bovine serum albumin (14C-BSA) that has been used in previous studies. This supports the notion that proteins labelled by 14C-methylation are not suitable as model proteins in metabolic studies due to modification of their 14C-methylated lysine residues. Further studies on the 14C-SSP demonstrated a digestibility of 59±13% in juvenile halibut, while at the pre-metamorphic stage, it was only 25±13%. This supports the hypothesis that there is a significant improvement in the ability to digest and utilise dietary proteins as the digestive system becomes fully developed, including a functional (acid-producing) stomach. [Copyright &y& Elsevier]

Pseudoplatystoma punctifer is an Amazonian catfish highly appreciated for its high flesh quality, size, and commercial value. Its aquaculture is pursued to satisfy the demands of an increasing population in the region. However, knowledge of the nutritional needs during the early life stages is necessary for improving growth and reducing the incidence of cannibalism, factors that limit the success of its commercial farming. This study aimed at evaluating the influence of four diets containing different protein and lipid levels (30:15, 30:10, 45:15, or 45:10 in %) in the digestive physiology and performance of early juveniles. The results showed that the dietary protein:lipid as well as carbohydrate levels and ratios influenced differently the whole-body proximate composition, the digestive physiology and development, and hence growth and survival. The 45:15 diet promoted the best growth, survival, and the most rapid development of the digestive system, as shown at histological (higher number of hepatocytes, goblet cells in the anterior intestine and enterocytes in all intestinal portions, and longer folds in the posterior intestine), molecular (highest amylase , lipoprotein lipase , phospholipase , trypsinogen, and pepsinogen gene expression), and biochemical (highest lipase and pepsin activities and higher alkaline phosphatase:leucine alanine peptidase activity ratio) levels. Lipids were favored over carbohydrates as source of energy, with lipids promoting a protein-sparing effect at adequate energy:protein ratio. Carbohydrate content higher than 25% was excessive for this species, leading to unbalanced lipid metabolism and fat deposition in the liver.