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•Plastic particles crossing the intestinal barrier is debated.•PS-NP particles were tested in ex-vivo time series experiments using Ussing chambers.•Two PS-NP concentrations were ...tested on two locations of adult Seabass guts.•PS-NP directly crossed the intestinal barrier of adult Seabass within few minutes.•PS-NP translocation was confirmed by 3 complementary techniques.
Plastic pollution in marine ecosystems constitutes an important threat to marine life. For vertebrates, macro/microplastics can obstruct and/or transit into the airways and digestive tract whereas nanoplastics (NPs; < 1000 nm) have been observed in non-digestive tissues such as the liver and brain. Whether NPs cross the intestinal epithelium to gain access to the blood and internal organs remains controversial, however. Here, we show directly NP translocation across the intestinal barrier of a fish, the European seabass, Dicentrarchus labrax, ex vivo. The luminal side of median and distal segments of intestine were exposed to fluorescent polystyrene NPs (PS-NPs) of 50 nm diameter. PS-NPs that translocated to the serosal side were then detected quantitatively by fluorimetry, and qualitatively by scanning electron microscopy (SEM) and pyrolysis coupled to gas chromatography and high-resolution mass spectrometry (Py-GC-HRMS). Fluorescence intensity on the serosal side increased 15–90 min after PS-NP addition into the luminal side, suggesting that PS-NPs crossed the intestinal barrier; this was confirmed by both SEM and Py-GC-HRMS. This study thus evidenced conclusively that NPs beads translocate across the intestinal epithelium in this marine vertebrate.
During these last 20 years, many studies have focussed on the development of the digestive tract in marine fish larvae. Most of the studies aimed at acquiring knowledge on the optimal form of dietary ...supply for different nutrients, in order to formulate a compound diet able to totally replace live preys in the fish larvae feeding sequence. Consequently, most of the studies aimed at describing the effect of dietary adaptation on digestive enzymes profile, the morphology of the main organs, while others aspects of the physiology of the larvae digestive tract (gut hormones, intestinal transport…) were poorly investigated.
This review reports the more recent data on dietary modulation of digestive enzymes with a particular emphasis, when possible, on the molecular and hormonal mechanisms controlling enzyme expression in larvae. We examined how the dietary modulation of pancreatic and intestinal enzymes involved in protein digestion can provide useful information concerning the nature and molecular form of a dietary protein supply that would be adequate for larval stages. In the same way, data on lipase and phospholipase A2 paralleled with recent findings on lipid transport, strongly suggests that fish larvae handle phospholipids better than triglycerides.
A new field of research has been opened in fish larvae nutrition, with the study of the effects of some nutrients on the functioning of some metabolic pathways involved in development and their impact on larvae physiology and morphogenesis, as well as the further development of juveniles. These studies revealed cross-talks between some metabolic processes, particularly those concerning vitamin A and polyunsaturated fatty acids, during fish larvae development and unveil the necessity to design a global approach for determining the requirements of some nutrients.
The main goal of this work was to determine the effect of dietary live yeast
Debaryomyces hansenii on the enzymatic antioxidative status of sea bass
Dicentrarchus labrax larvae. Growth, activity and ...expression of the main antioxidative enzymes: catalase (CAT), glutathione peroxidase (GPX) and superoxide dismutase (SOD), and heat shock protein (HSP70) were measured in sea bass larvae at 23 and 48
days after hatching. Larvae were fed on two microdiets: group one, fed microdiet containing live yeast and the control group fed microdiet without yeast. Heat shock protein 70 showed the same expression levels in both fish larvae fed yeast and the control diet. The group fed
D. hansenii showed highest growth and lower activity and expression levels of GPX and SOD compared to fish fed control diet. In our work the differences in activity and gene expression patterns could only be attributed to the presence of yeast, assuming a possible involvement of superoxide anion retention in fish larvae, which could represent importance to the host to increase cell or tissue responsiveness to growth- and/or differentiation-enhancing factors.
Vitamins D and C are essential in many physiological functions. Vitamin D, a fat soluble vitamin, is crucial to preserve calcium and phosphate homeostasis and to protect the skeletal integrity. This ...hormone functions through the vitamin D receptor (VDR) inducing the expression of various calcium binding and transport proteins in the intestine to stimulate active calcium uptake, thus preserving normocalcemia and, indirectly, maintaining bone mineralization. Besides, vitamin D also acts directly on osteoblasts, the resident bone-forming cells of the skeleton, to inhibit proliferation, modulate differentiation, and regulate mineralization of the extracellular matrix. Vitamin C, a water soluble vitamin, acts as a co-substrate for hydroxylase and oxygenase enzymes involved in the biosynthesis of pro-collagen, carnitine and neurotransmitters, among other numerous physiological functions such as antioxidant or pro-oxidant. Both vitamins should be supplied by the diet because fish are unable to synthesize them. However, their wide range of action makes it difficult to adjust the adequate amount of these vitamins to achieve an optimal fish performance. Besides, the dietary vitamin needs of fish depend on several factors such as developmental stage, physiological, environmental/ecological and genetic conditions. In this sense, vitamin requirements of flatfish do not necessarily meet those of pelagic fish and depends also on their feeding habits (carnivorous, planktivorous or detritivorous); the dietary vitamin demands of an adult fish differ from those of a larva; and even within the same fish species and developmental stage, the environmental conditions would also influence the vitamin needs (i.e., under stress conditions, high vitamin C levels have been demonstrated to improve stress resistance and, consequently, growth).
The present paper gives a general overview about the requirements of vitamins D and C in fish and specifically reviews the role of these vitamins in fish skeletogenesis and their influence in the development of skeletal deformities. In addition, new insights on the molecular pathways involving these vitamins in the skeletal ossification process are provided.
This study examined the effect of a commercial mix of Bacillus sp. on survival, growth and digestive enzyme activities of Florida pompano, red drum and common snook. Larvae were fed either live feed ...enriched with Algamac 3050 (Control), Algamac 3050 and probiotics (PB), or the previous diet combined with a daily addition of probiotics to the tank water (PB+). Survival was not affected by the treatments for any of the species. At the end of the pompano and snook trial, standard lengths of larvae from the PB and PB+ treatments were significantly greater than for the control larvae. Microbiological analyses were performed at the end of the pompano trial, and numbers of presumptive Vibrio were not a concern in the system. For both pompano and snook, trypsin‐specific activity was higher in PB and PB+ larvae compared with the control larvae. Similarly, alkaline phosphatase activity was higher for the pompano larvae fed the PB and PB+ treatments and for the snook larvae fed the PB+ treatment compared with the control larvae. This experiment suggests that a mix of Bacillus sp. can promote growth through an early maturation of the digestive system during the early larval stages of pompano and snook.
Haemal lordosis, a frequent skeletal deformity in teleost fish, has long been correlated with increased mechanical loads induced by swimming activity. In the present study, we examine whether ...juvenile zebrafish can recover from haemal lordosis and explore the musculoskeletal mechanisms involved. Juveniles were subjected to a swimming challenge test (SCT) that induced severe haemal lordosis in 49% of the animals and then immediately transferred them to 0.0 total body lengths (TL) per second of water velocity for a week. The recovery from lordosis was examined by means of whole mount staining, histology and gene expression analysis. Results demonstrate that 80% of the lordotic zebrafish are capable of internal and external recovery within a week after the SCT. Recovered individuals presented normal shape of the vertebral centra, maintaining though distorted internal tissue organization. Through the transcriptomic analysis of the affected haemal regions, several processes related to chromosome organization, DNA replication, circadian clock and transcription regulation were enriched within genes significantly regulated behind this musculoskeletal recovery procedure. Genes especially involved in adipogenesis, bone remodeling and muscular regeneration were regulated. A remodeling tissue-repair hypothesis behind haemal lordosis recovery is raised. Limitations and future possibilities for zebrafish as a model organism to clarify mechanically driven musculoskeletal changes are discussed.
•European eel larvae were produced via assisted reproduction in captivity.•Thyroid hormone pathway (thrαA-B, thrβA-B and dio1-3) related genes identified.•European eel thyroid hormone receptor ...sequences were cloned and characterized.•Temperature, larval age and/or their interaction affected gene expression.•Vertebrate thyroid hormone receptor sequences were phylogenetically analyzed.
Thyroid hormones (THs) are key regulators of growth, development, and metabolism in vertebrates and influence early life development of fish. TH is produced in the thyroid gland (or thyroid follicles) mainly as T4 (thyroxine), which is metabolized to T3 (3,5,3′-triiodothyronine) and T2 (3,5-diiodothyronine) by deiodinase (DIO) enzymes in peripheral tissues. The action of these hormones is mostly exerted by binding to a specific nuclear thyroid hormone receptor (THR). In this study, we i) cloned and characterized thr sequences, ii) investigated the expression pattern of the different subtypes of thrs and dios, and iii) studied how temperature affects the expression of those genes in artificially produced early life history stages of European eel (Anguilla anguilla), reared in different thermal regimes (16, 18, 20 and 22 °C) from hatch until first-feeding. We identified 2 subtypes of thr (thrα and thrβ) with 2 isoforms each (thrαA, thrαB, thrβA, thrβB) and 3 subtypes of deiodinases (dio1, dio2, dio3). All thr genes identified showed high similarity to the closely related Japanese eel (Anguilla japonica). We found that all genes investigated in this study were affected by larval age (in real time or at specific developmental stages), temperature, and/or their interaction. More specifically, the warmer the temperature the earlier the expression response of a specific target gene. In real time, the expression profiles appeared very similar and only shifted with temperature. In developmental time, gene expression of all genes differed across selected developmental stages, such as at hatch, during teeth formation or at first-feeding. Thus, we demonstrate that thrs and dios show sensitivity to temperature and are involved in and during early life development of European eel.
Dicentrarchus labrax were fed from 10 to 40 days posthatching with six microdiets differing in the inclusion level (60 g kg‐¹ and 120 g kg‐¹) and type of protein hydrolysate (PH; yeast, YPH; pig ...blood, PBPH; pig red blood cells, PRBCPH). A microdiet containing 120 g kg‐¹ fish PH (FPH) was used as a control. PH differed in their amino acid (AA) profile and molecular weight distribution and therefore the tested microdiets too. The estimated content in FAA and di‐ and tripeptides in the FPH microdiet was 2 g kg‐¹ and 44 g kg‐¹, respectively. FAA estimated levels in YPH and PBPH microdiets were 26 g kg‐¹ and 53 g kg‐¹, whereas levels of di‐ and tripeptides were 30 g kg‐¹ and 60 g kg‐¹, respectively. The estimated levels of FAA in PRBCPH microdiets were 8 g kg‐¹ and 17 g kg‐¹, whereas estimated levels of di‐ and tripeptides were 11 g kg‐¹ and 22 g kg‐¹, respectively. Results revealed that FPH may be replaced by alternative PH from yeast and pig blood products, as fish fed those diets performed, in terms of growth, survival, digestive function and incidence of skeletal deformities, as well as those fed the FPH microdiet. Using YPH, PBPH and PRBCPH, the inclusion level of PH in microdiets might be reduced to a half with respect to current practices using FPH.
Marine fish larvae undergo major morphological and cellular changes during the first month of life. The ontogeny of the gastrointestinal tract combines these two aspects of the larval development and ...is very interesting in that the timing of functional changes appears genetically hard-wired. The goal of this paper is to give an overview of the gastrointestinal development process in marine fish larvae, with particular attention to three species: sea bass; red drum; and sole, since the description of gut maturation in fish larvae was initiated during the last decade with these species. During the early stages, marine fish larvae exhibit particular digestive features. Concerning the exocrine pancreas, amylase expression decreases with age from the third week post-hatching in sea bass and red drum (approximately 400 degree days), whereas expression of other enzymes (trypsin, lipase, phospholipase A2…) increases until the end of the larva period. Moreover, secretory function of the exocrine pancreas progressively develops and becomes efficient after the third week of life. Concerning the intestine, enzymes of the enterocyte cytosol (in particular peptidase) have higher activity in young larvae than in older. Approximately in the fourth week of post-hatching development in sea bass, red drum and sole larvae, the cytosolic activities dramatically decline concurrently with a sharp increase in membranous enzyme activities of the brush border, such as alkaline phosphatase, aminopeptidase N, maltase... This process characterises the normal maturation of enterocytes in developing fish larvae and also in other vertebrates’ species. The establishment of an efficient brush border membrane digestion represents the adult mode of digestion of enterocytes. This paper also describes the role of diet on the development of the gastrointestinal tract. Indeed, the maturational process of digestive enzyme can be enhanced, stopped, or delayed depending on the composition of the diet.
The purpose of this study was to check if it is possible to influence sea bass juvenile metabolism by a conditioning of larvae from day 6 post hatching to day 45 to a low or a high HUFA compound diet ...(LH, 0.8% EPA
+
DHA and HH, 2.2% EPA
+
DHA) when reared at 16 or 22 °C. Following a 3-month intermediate period (at 19 °C using a commercial diet), the adaptability of the 4 initial larval groups to a HUFA experimental deprived diet (0.5% EPA
+
DHA) were tested at 19 °C in a 60 day-experiment (d-151–211). The four experimental duplicated conditions were ex-LH16 and ex-HH16 for the 2 groups previously reared at 16 °C (initial weight, 7.3
±
0.5 g) and ex-LH22 and ex-HH22 for the 2 groups previously reared at 22 °C (initial weight, 11.1
±
0.5 g). Survival was maximal and there was a 1.6–2 fold increase in mass during the experiment. Growth was similar in the 4 experimental groups: NS difference in growth curve slopes (
P
=
0.7). At the end of the experiment (d-211), whole body fat levels were in the same range in all groups (13–15% WW). The fatty acid (FA) composition in polar lipids (PL) and total lipids (TL) were significantly affected by initial weight related to larvae conditioning, which can be mainly attributed to a dilution effect (impact of initial FA content on final FA content versus relative mass increase during the course of the experiment). Conversely to this trend, DHA content in PL was higher in the ex-LH groups than in the ex-HH groups whatever thermal conditioning of larvae was. This indicated that ex-LH groups had a better capacity to adapt to a deficient HUFA diet than ex-HH fish. The relative expression of the delta-6 desaturase (Δ6D) was significantly higher in ex-LH than in ex-HH groups (
P
<
0.001) between d-151 and d-181, which suggested that Δ6D transcription in ex-LH groups was positively modulated by the HUFA-deprived diet. This stimulation of the first step of the desaturation/elongation pathway could allow synthesizing FA needed to compensate low dietary HUFA supply. This study shows for the first time that it seems possible to influence juvenile fish metabolism by a nutritional conditioning during the larval stage.
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