Development Of Digestive System Research Articles

The relationship between nutrition and intestinal health in newborn lambs

Abstract As with all animals, the period in their lives when lambs are most vulnerable is the period before and immediately after birth. Because this period (the suckling period) is the period of clinging to life in an environment open to microorganism contamination after the sterile uterine environment. It is very important that this difficulty can be reduced with good care and feeding practices that must be applied during this period and that the puppy lamb can have a healthy and highly productive life during this risky period and in the future. Regulation and enhancement of the intestinal microbiome is a crucial aspect for optimizing the health and performance of farm animals. This is mainly because diet and management practices greatly affect the intestinal microbiota, resulting in changes in nutrient utilization and the immune system. The intestinal health of newborn lambs is affected by feeding manipulations, as in other ruminants. In this review, the suckling period and digestive system development in newborn lambs are mentioned. Additionally, this review discusses some practices to manipulate intestinal development and microbial colonization in order to improve the production and health of newborn lambs at an early age when they are most susceptible to enteric diseases.

Effects of Inulin Use in Broiler Chick Rations on Performance and Digestive System Development

Bu araştırmada, etlik civciv rasyonlarında inülin kullanımının performans ve sindirim sistemi gelişimi üzerine etkilerini ortaya koymak amaçlanmıştır. Çalışmada, performans ve sindirim sistemi gelişimi incelemeleri için iki ayrı deneme yürütülmüştür. Araştırmada günlük yaşta karışık cinsiyetteki civcivlere % 0.25, 0.50 ve 1.00 inülin içeren başlatma yemi hazırlanarak verilmiştir. Araştırmada kullanılan yemler toz formda hayvanlara sunulmuştur. 
 
 Performans denemesinde, 400 adet günlük yaşta karışık cinsiyette Ross 308 etlik civciv, 4 tekerrürlü 4 deneme grubuna 3 rasyon inulin düzeyi olmak üzere faktöriyel düzende tesadüf parselleri deneme düzeninde rastgele olarak dağıtılmıştır. Sindirim sistemi incelemeleri için performans testine benzer olarak 160 adet civciv gruplara dağıtılmıştır. Canlı ağırlık, canlı ağırlık artışı, yem tüketimi ve yemden yararlanma sayısı araştırmanın başlatılmasını takiben 10, 21 ve 42 günlük yaşta ve 10. günde kontrollü öldürme yapılarak da civcivlerin sindirim sistemi bölümleri incelenmiştir. 
 
 Etlik civciv yemlerine inülin ilavesi etlik piliçlerin performansını olumsuz etkilerken, sindirim sistemi gelişimi üzerinde olumsuz etki yaratmamıştır. İnülin ilavesi, canlı ağırlık artışı ve yemden yararlanma oranını önemli derecede düşürmüştür. 
 
 Sonuç olarak, bu araştırmadaki tüm bulgularımız incelendiğinde yemlere % 0.25 düzeyinde inülin kullanılmasının performans değerlerini olumsuz etkilemeden değerlendirilebileceğini göstermiştir.

Fibroblast growth factor 10

Fibroblast growth factor 10 (FGF10) is a major morphoregulatory factor that plays essential signaling roles during vertebrate multiorgan development and homeostasis. FGF10 is predominantly expressed in mesenchymal cells and signals though FGFR2b in adjacent epithelia to regulate branching morphogenesis, stem cell fate, tissue differentiation and proliferation, in addition to autocrine roles. Genetic loss of function analyses have revealed critical requirements for FGF10 signaling during limb, lung, digestive system, ectodermal, nervous system, craniofacial and cardiac development. Heterozygous FGF10 mutations have been identified in human genetic syndromes associated with craniofacial anomalies, including lacrimal and salivary gland aplasia. Elevated Fgf10 expression is associated with poor prognosis in a range of cancers. In addition to developmental and disease roles, FGF10 regulates homeostasis and repair of diverse adult tissues and has been identified as a target for regenerative medicine.

Changes in the histology and digestive enzyme activity during digestive system development of silver pomfret (Pampus argenteus)

Silver pomfret (Pampus argenteus) is an economically important marine fish species in the Indian and Western Pacific oceans, it has great aquaculture potential. Research on the ontogeny of the digestive system is critical in improving the larval rearing protocols and weaning process. In this study, an approach that integrates histology and biochemistry was used to illustrate the digestive system ontogeny of silver pomfret from hatching to 50 days post-hatching (dph). At 1 dph, the digestive system was differentiated into the esophageal sac, esophagus, anterior and posterior intestine, liver, pancreas, and gall bladder, and except for pepsin, digestive enzymes were detected. At 4 dph (4.0 ± 0.2 mm in total length, TL), the mouth opened to allow for exogenous feeding, which coincided with the development of papillae and mucous cells in the esophageal sac, indicating their preliminary function of grinding food. At 7 dph (4.5 ± 0.2 mm, TL), the larvae entered an exclusively exogenous feeding stage and numerous supranuclear vacuoles appeared in the posterior intestine. From 1 to 10 dph, alkaline phosphatase increased sharply, suggesting the rapid development of enterocytes and intestine. At 10 dph (4.8 ± 0.6 mm, TL), gastric glands appeared in the stomach, and from 14 to 20 dph (5.2 ± 0.3 to 6.1 ± 0.4 mm, TL), they multiplied greatly. At this time, the other digestive organs, including the esophageal sac, pyloric caeca, intestine, and accessory glands were well developed and tended to mature in structure. From 15 to 20 dph, the activity of pepsin, trypsin, lipase, and α-amylase rapidly increased, suggesting that the digestive system might have become functionally integrated. After reaching enzyme activity peaks, alkaline phosphatase, lipase, and α-amylase decreased significantly while pepsin and trypsin initially decreased and then increased to a second peak at 50 dph (25.0 ± 4.6 mm, TL). Except for the esophageal sac, the ontogeny of the digestive system in silver pomfret larvae appears to be generally similar to that of other marine fish species; it might be feasible to begin weaning this species from 15 to 20 dph, which would reduce the amount of live food as required by current protocols. This study provides a preliminary insight into the digestive system ontogeny of silver pomfret and establishes an initial step towards the rearing and weaning process optimization of this novel species.

Preterm pigs for preterm birth research: reasonably feasible.

Preterm birth will disrupt the pattern and course of organ development, which may result in morbidity and mortality of newborn infants. Large animal models are crucial resources for developing novel, credible, and effective treatments for preterm infants. This review summarizes the classification, definition, and prevalence of preterm birth, and analyzes the relationship between the predicted animal days and one human year in the most widely used animal models (mice, rats, rabbits, sheep, and pigs) for preterm birth studies. After that, the physiological characteristics of preterm pig models at different gestational ages are described in more detail, including birth weight, body temperature, brain development, cardiovascular system development, respiratory, digestive, and immune system development, kidney development, and blood constituents. Studies on postnatal development and adaptation of preterm pig models of different gestational ages will help to determine the physiological basis for survival and development of very preterm, middle preterm, and late preterm newborns, and will also aid in the study and accurate optimization of feeding conditions, diet- or drug-related interventions for preterm neonates. Finally, this review summarizes several accepted pediatric applications of preterm pig models in nutritional fortification, necrotizing enterocolitis, neonatal encephalopathy and hypothermia intervention, mechanical ventilation, and oxygen therapy for preterm infants.

Effects of Different Co-Feeding Protocols on the Early Weaning of Flathead Grey Mullet (Mugil cephalus) Larvae.

The sustainable expansion of aquaculture relies on a sufficient supply of eggs and larvae, which are the first step of life cycle management. However, marine fish larval rearing generally depends on live feed production, which needs additional facilities and labor. The flathead grey mullet (Mugil cephalus), a promising species for aquaculture diversification, has a precocious digestive system development, supporting the feasibility of early weaning strategies. For these reasons, this study evaluated survival, growth, proximate and fatty acid composition, and gene expression of Mugil cephalus larvae reared under three different weaning protocols. Three co-feeding treatments, two with different Artemia sp. concentrations (A100 and A50, 2 and 1 Artemia sp. mL-1 day-1, respectively) and one with only rotifers administered as live feed along the feeding trial (A0), were assessed from 22 to 36 days post-hatching (dph). The A0 treatment performed better in survival (64.79 ± 7.40%) than the A100 protocol (32.46 ± 12.82%). In contrast, the larvae of the A100 treatment presented significantly higher final length (15.51 ± 0.86 mm) than those of the A0 treatment (12.19 ± 1.45 mm) and higher final weight (41.28 ± 1.48 mg) than those of the A50 and A0 treatments (31.23 ± 3.65 mg and 24.03 ± 7.99 mg, respectively). On the other hand, the expression of digestive enzyme- and somatotropic factor-related genes did not show differences between treatments. The present results support the convenience of treatment A0 in maximizing survival, as rotifers should be maintained until 30-32 dph (until a total larval length of at least 10 mm). However, to improve growth and minimize size dispersion, Artemia sp. addition is recommended from day 26 to day 29 post-hatching (total larval length of 8 to 9 mm).

Productive performance, breast growth and digestive system development in European quail subjected to post-hatch fasting for different periods.

This study assessed the effect of different periods of post-hatch fasting on animal performance and breast and digestive system growth in European quail. Quail chicks were distributed in a completely randomized design, with four fasting periods (0, 24, 36, and 48 hs) and four replications of 40 birds per treatment. In 1 to 14-day-old chicks, weight gain decreased with increasing fasting time. Compensatory gain was observed from 15 days of age onward. Fasted quail had a lower length and relative weight of the digestive system than fed animals for up to 14 days. Histologically, the duodenal villus height was significantly lower in 3-day-old quail fasted for 36 hs than in those fasted for 48 hs, but this effect was not observed at 7 days. Scanning electron microscopy showed no differences in the small intestinal mucosa between fasted and fed birds at 3 days of age. Post-hatch fasting reduced the relative weight of the breast in quail aged 1 to 14 days but did not affect type IIa and IIb fiber diameter at 35 days. On the basis of these results, it is recommended that European quail raised for meat should not be fasted for more than 48 hs post-hatch.

Upper gastrointestinal duplication complicated by perforation in a child

Gastrointestinal duplications are rare congenital malformations occurring in embryonic period of development of digestive system. These abnormalities are usually found in infancy or early childhood. Clinical presentation is extremely diverse depending on dimensions, localization and type of duplication. The authors present duplication of antral and pyloric parts of the stomach, the 1st segment of the duodenum and pancreatic tail. Mother with a 6-month-old child turned to the hospital. According to the mother, the child was sick for about 3 days when episodes of periodic anxiety first appeared. Upon admission, abdominal neoplasm was suspected after ultrasound. On the second day after admission, anxiety increased. There was impairment of appetite, and the child rejected food. Abdominal asymmetry in umbilical area was observed. Considering clinical data on intestinal obstruction, emergency transverse right-sided laparotomy was performed. A tubular structure was found resembling intestinal tube was found between the stomach and transverse colon. Surgeon found duplication of antral and pyloric parts of the stomach, the 1st segment of the duodenum and its perforation. During further revision, additional pancreatic tail was diagnosed. En-bloc resection of gastrointestinal duplications was carried out. Postoperative period was uneventful. Enteral feeding was initiated after 5 days, and the patient was transferred to surgical unit. The child was discharged after 12 postoperative days.

Should patients on levothyroxine therapy be screened for pancreatic cancer?

Pancreatic ductal adenocarcinoma is an aggressive disease with increasing incidence. Thyroid hormones play different roles in development and physiological processes of the entire digestive system, including pancreas. Therefore, many have hypothesized that thyroid hormone supplementation for hypothyroidism disorders might increase the risk of malignancy. We conducted retrospective observational mono-centre study. The aim was to examine the prevalence of thyroid disorders among patients with pancreatic cancer. Moreover, we investigated the impact of thyroid hormone supplementation in pancreatic cancer patients' outcome and the correlation with various clinicopathologic parameters. A total of 92 consecutive pancreatic cancer patients were retrospectively reviewed: 18.5% patients had a history of hypothyroidism and all received a replacement hormone therapy with levothyroxine, in particular 20% in metastatic group and 11% in radically resected PDAC patients' group. Nor in radically resected neither in metastatic group, we did not observe any statistically significant difference in outcome between the group with or without thyroid disorders. On multivariate analyses, cox proportional hazards model analysis showed that only the presence of perineural invasion was associated with a significantly higher hazard ratio for overall survival in metastatic PDAC patients (HR=2.7; 95%CI=1.029-6.925; p=0.009). We observed higher prevalence of thyroid disorders in PDAC patients. Further studies are warranted to explore the impact of levothyroxine therapy on outcome in PDAC patients.

Effects of broiler breeder age on immune system development of progeny

The objective of this study was to determine the effects that breeder age has on digestive and immune system development; the transfer of immunoglobulins to egg yolk, yolk sac, and neonate chicks; and the immune response of chicks up to 35 days old. Three ages (32, 42, and 52 weeks) of Hubbard breeders were studied with ages as treatments. A total of 425 eggs were weighed for each of the three treatments and incubated. After hatching, a total of [...]

Comparative Effects of Allulose, Fructose, and Glucose on the Small Intestine.

Despite numerous studies on the health benefits of the rare sugar allulose, its effects on intestinal mucosal morphology and function are unclear. We therefore first determined its acute effects on the small intestinal transcriptome using DNA microarray analysis following intestinal allulose, fructose and glucose perfusion in rats. Expression levels of about 8-fold more genes were altered by allulose compared to fructose and glucose perfusion, suggesting a much greater impact on the intestinal transcriptome. Subsequent pathway analysis indicated that nutrient transport, metabolism, and digestive system development were markedly upregulated, suggesting allulose may acutely stimulate these functions. We then evaluated whether allulose can restore rat small intestinal structure and function when ingested orally following total parenteral nutrition (TPN). We also monitored allulose effects on blood levels of glucagon-like peptides (GLP) 1 and 2 in TPN rats and normal mice. Expression levels of fatty acid binding and gut barrier proteins were reduced by TPN but rescued by allulose ingestion, and paralleled GLP-2 secretion potentially acting as the mechanism mediating the rescue effect. Thus, allulose can potentially enhance disrupted gut mucosal barriers as it can more extensively modulate the intestinal transcriptome relative to glucose and fructose considered risk factors of metabolic disease.

CircJag1 promotes apoptosis of ethylene thiourea-exposed anorectal malformations through sponging miR-137-3p by regulating Sox9 and suppressing Wnt/β-catenin pathway during the hindgut development of rat embryos.

Anorectal malformations (ARMs) are common birth defects involving congenital structural anomalies of the gastrointestinal tract. As an important component of non-coding RNAs, circular RNAs (circRNAs) widely participate in the digestive system development; however, the specific molecular mechanism of their involvement in ARM occurrence remains obscure. Herein, we generated rat models of ARMs induced by ethylene thiourea. A novel circRNA (circJag1) was screened and identified by RNA-Seq, which is remarkably upregulated in hindgut tissues of ARM rat embryos. In vivo experiments, colocation analysis via fluorescence in situ hybridization, and immunofluorescence further demonstrated that the disordered circJag1/miR-137-3p/Sox9 expression caused a spatiotemporal imbalance in the urorectal septum (URS) of ARMs. In vitro, functional assays confirmed that circJag1 upregulation resulted in the degradation of nuclear β-catenin, C-myc, and Cyclin D1 in rat intestinal epithelial cells, as well as the promotion of apoptosis and suppression of cell proliferation. Mechanistically, dual-luciferase reporter assay and RNA immunoprecipitation assay indicated that circJag1 acted as a miR-137-3p sponge, thereby inhibiting its repressive effect on its target Sox9. Further experiments showed that a loss of Sox9 abolished the circJag1-mediated increase in apoptosis. In conclusion, aberrantly high circJag1 expression promotes epithelial apoptosis by suppressing the canonical Wnt/β-catenin pathway via the miR-137-3p/Sox9 axis, which leads to fusion failure of the URS and cloacal membrane, and eventually contributed to ARMs. Our achievements might boost the comprehension of ARM pathogenesis and could provide a novel candidate target for the development of therapies for ARMs to complement surgical treatment.

DHA-enrichment of live and compound feeds influences the incidence of cannibalism, digestive function, and growth in the neotropical catfish Pseudoplatystoma punctifer (Castelnau, 1855) during early life stages

Pseudoplatystoma punctifer is a highly appreciated fish species native to the Amazon basin, whose commercial farming has been hampered by low survival during early life stages due to the high incidence of cannibalism and the low acceptability of compound diets at weaning. Dietary DHA is known to promote digestive system development and maturation and growth, whereas its deficiency induces stress. The aim of this study was to evaluate the effect of dietary DHA supplementation on the incidence of cannibalism, digestive physiology, and growth performance during the early life stages of P. punctifer to improve current feeding protocols. Four dietary treatments were generated using a commercial enrichment product with high DHA content. Fish larvae were fed non-enriched or enriched Artemia from 4 to 15 days post fertilization (dpf) and fed a non-enriched or enriched compound diet from 15 to 26 dpf, coinciding with the start of the juvenile stage. Growth, survival, incidence of cannibalism, proximate and fatty acid composition, histology of the intestine and liver, and quantitative gene expression of the main digestive enzymes (amy, try, ctr, pga, pla2, and lpl) were analyzed in the different dietary groups at the end of each feeding period. Results showed that dietary DHA supplementation influenced P. punctifer in a developmental stage-dependent manner. In particular, DHA-enriched Artemia provided during the larval stage contributed to reduce the incidence of cannibalism and improved survival at the early juvenile stage, while enriching the compound diet improved growth. The expression level of genes involved in protein and carbohydrate digestion (ctr, amy) was higher in groups fed enriched Artemia despite that both enriched and non-enriched Artemia displayed similar proximate composition, suggesting that different dietary fatty acid profiles may modulate the expression of these digestive enzyme precursors. The group transitioning from enriched Artemia to non-enriched compound diet showed a higher expression of most genes at the early juvenile stage. At the histological level, the group fed non-enriched Artemia and compound diet showed a significant accumulation of lipids in the intestine relative to the liver, contrary to the rest of the groups that showed similar amounts of lipids in both tissues, indicating a more balanced lipid metabolism. The group fed both DHA-enriched Artemia and compound diet provided the best results in terms of growth, survival, incidence of cannibalism, and digestive physiology. In conclusion, this study showed that the nutritional history during the larval period affected fish nutrition and behavior during the early juvenile stage.

The Dynamics of Chromatin Accessibility Prompted by Butyrate-Induced Chromatin Modification in Bovine Cells

Butyrate is produced by microbe fermentation in the rumen, and its supplementation results in rumen development. Butyrate-induced experiments are valuable in studying nutrient metabolism, cell growth, and functional genomics. This study aimed to characterize accessible chromatin regions and the dynamics of genomic accessibility prompted by butyrate-induced histone modifications in bovine cells. An average of 117,569 accessible chromatin regions were identified for all samples, and 21,347 differentially accessible regions (DARs) for butyrate. Most of the DARs were in distal intergenic regions, introns, and promoters. Gene ontology enrichment resulted in important terms related to the digestive system, regulation of epithelial cells, and cell adhesion. Ingenuity Pathway Analysis (IPA) identified critical networks (e.g., digestive system development, cell morphology and assembly, and cell cycle); canonical pathways (e.g., TGFβ, Integrin-linked kinase, and epithelial adherens junction); and upstream regulators (e.g., TGFβ1, FOS, JUNB, ATF3, and KLFs). Co-expression analysis further showcased the TGFβ and Integrin-linked kinase (ILK)-signaling pathways, which play roles in rumen development through cellular adhesions. This study is the first to provide a genome-wide characterization of differential, open chromatin regions for bovine cells by butyrate-induced treatment. These results provide valuable information for future studies of the butyrate functions in cattle gastrointestinal tract development.

The early story of growth hormone-releasing factor in rats, swine, and cattle

Following the discovery of the growth hormone-releasing factor from a human pancreatic tumor by the group of Guillemin at the Salk Institute in California, research on this factor has exploded. This review article is focused on the results obtained early after this discovery and summarizes the biological effects of this releasing factor on the rat digestive system development and above all on pig, steer, and gilt growth as well as on milk production in lactating sows and cows.

Digestive system ontogeny and the effects of weaning time on larval survival, growth and pigmentation development of orchid dottyback Pseudochromis fridmani

Although live prey remain essential for most marine finfish larviculture, the larvae or young juveniles are ultimately weaned onto formulated feeds at foodfish and ornamental fish hatcheries. Understanding the development of larval digestive capabilities is crucial for optimizing weaning success. The present study used the digestive system ontogeny to interpret the effects of different weaning times on larval rearing of orchid dottyback Pseudochromis fridmani, a marine ornamental fish species. The study documented the ontogenetic digestive system development of P. fridmani larvae from hatching to 40 days post-hatching (DPH). The histological analysis showed that as a demersal spawning species, the newly hatched P. fridmani larvae possessed advanced gut development which allowed the onset of exogenous feeding soon after hatching. Most major larval gut morphological changes were completed by 13 DPH; however, the stomach and gastric glands were first observed between 32 and 36 DPH. At this stage, P. fridmani larvae were expected to acquire substantially improved digestive capabilities, and were likely capable of digesting formulated feed. In the subsequent experiment, P. fridmani larvae were weaned onto formulated feed from 20, 23, 26, 29, or 32 DPH over a three-day period of co-feeding with enriched Artemia; the control group were exclusively fed enriched Artemia until the end of experiment. The timing of weaning significantly affected the larval growth and pigmentation development rather than survival (mean: 44–64%). P. fridmani larvae weaned later tended to grow larger, and the control group grew significantly larger in length than all weaning treatments (p < 0.05). Interestingly, at the end of the experiment (40 DPH), none of larvae from the control obtained adult-type pigmentation despite their larger size. In contrast, the introduction of formulated feed appeared to stimulate pigmentation development in P. fridmani individuals with a clear trend of higher pigmentation completion by 40 DPH (mean: 62–97%) with earlier weaning. Overall, this study demonstrated that P. fridmani larvae could be weaned onto formulated feed from as early as 20 DPH, before the stomach and gastric glands were fully developed; indeed, the timing of adult-type pigmentation change in P. fridmani was also advanced by the introduction of the weaning diet.

Морфофункціональна характеристика окремих органів травної системи людини

Today, the growing trend of the prevalence of diseases of the digestive system is a very important issue not only in Ukraine but also around the world. This problem applies not only to practical areas of health care, but also to theoretical medicine. The study of the anatomical structure and functional state of the digestive system is the theoretical basis for the extrapolation of various pathological conditions in laboratory animals. Analysis of scientific sources showed a lack of comprehensive morphological studies of the human digestive system. The purpose of the paper was to study the features of some organs of the human digestive system in the morphological aspect by bibliographic analysis of literature. Materials and methods. This bibliographic analysis is based on published peer-reviewed articles, books, textbooks, monographs, abstracts of dissertations. For the purposes of this systematic review, literature search (concerning the study of the structure of the human digestive system) was carried out on the Internet, domestic literature sources, scientific and electronic libraries of Poltava State Medical University by the following keywords: "digestive system", "morphology", "gastrointestinal tract", "colon", "cаecum", "embryonic development of the digestive system". Results and discussion. Digestive system (Latin «systema digestorium») is a system of organs of various structures and functions formed in phylogeny, the importance of which lies in the perception, mechanical and chemical (enzymatic) processing and absorption of nutrients needed to compensate for energy and material costs in the body. Conclusion. Significant progress has been made in understanding the development of the human digestive system over the past two decades. The human digestive system is formed in phylogeny community of similar in structure and function of organs, the importance of which is the digestion of food, mechanical and enzymatic breakdown, absorption of breakdown products into the internal environment of the body and their transport to the liver. The structure of the gastric mucosa is well thought out for secretion and protection against low pH of gastric contents, which is regulated by hydrochloric acid. The pancreas, like the gland of external secretion, produces many digestive enzymes in an inactive form. Activation usually occurs in the lumen of the small intestine. The liver receives most of the nutrients absorbed through the portal vein and then uses them to synthesize many larger molecules

Facultative planktotrophy in larvae of the purple mussel Perumytilus purpuratus

ABSTRACT The developmental pattern in the mid-intertidal mussel Perumytilus purpuratus was investigated through laboratory cultures. Larval development, growth, survival rate, and time to reach the post-larval stage were determined using triplicated feeding/non-feeding treatments in artificial seawater at 18.2 ± 0.5°C. Development of the larval digestive system was examined histologically. We found that P. purpuratus have ova (121.1 ± 2.7 μm diameter) with a jelly coating, the digestive system develops in the trochophore, the veliger shell has a large prodissoconch-1 and a small prodissoconch-2, the larval period lasted between 10 and 14 days, and larvae could reach metamorphosis without the presence of particulate food. Unlike most of the mytilid species with pelagic larvae, a facultative planktotrophic development is evident in this species. This developmental pattern could be favourable in unstable and changing environments such as rocky shores.

Onset of nutrient consumption during early life stage digestive system development of two tuna species (Thunnus orientalis and Thunnus albacares)

To specify the timing of exogenous nutrient consumption in the larvae of two commercially important tuna species, the Pacific bluefin tuna (PBF) Thunnus orientalis and the yellowfin tuna (YFT) Thunnus albacares, the gene expressions of peptide transporter 1 (PEPT1) were examined. The mRNA expressions of PEPT1 first occurred at 2 days post hatching (dph) in PBF larvae and 3 dph for the YFT, and PEPT1 was found to only be expressed in the intestinal tract. The histological changes of the digestive tract of the YFT larvae were observed and compared to PBF larvae from a previous study. The intestines were developed at the hatching day for both species. It was found that the developmental timing of internal organs differed between the species, with the YFT showing an approximately one-day delay. The major organs such as liver, pancreas and gall bladder that excrete digestive enzymes appeared at 1 dph for PBF and 2 dph for YFT. The development of external morphological features was similar to organ development timings, with mouth-opening and first feeding starting at 2 dph for PBF, and 3 dph for YFT. Growth during the first month is rapid and variable for both species, ranging from 1.06 to 1.56 mm/d. Our findings provide new information about the early onset of feeding and larval development for the two species which would contribute to future aquaculture.

The Characteristic of Critical Genes in Neuroendocrine System and Their Regulation on Food Habit Transition and Metamorphosis of Veined Rapa Whelk Rapana venosa (Valenciennes, 1846)

Metamorphosis is a critical developmental event in mollusks, and neuroendocrine system plays an essential role in this process. Rapana venosa is an economically important shellfish in China, but the artificial technology of R. venosa aquaculture is limited by metamorphosis. As a carnivorous gastropod, food habit transition makes the mechanism of R. venosa metamorphosis more complex. To investigate the changes in the neuroendocrine system and to reveal its role in regulating the food habit transition and metamorphosis of R. venosa, we cloned the cDNA sequences encoding 5-hydroxytryptamine receptor (Rv-5HTR), nitric oxide synthetase (Rv-NOS) and cholecystokinin receptor (Rv-CCKR), and investigated their expression by quantitative real-time PCR analysis, and explore the spatio-temporal changes of 5-HT protein expression using Immunohistochemical (IHC) analysis. The expression of the three geens was significantly increased in the early intramembrane veliger stage, which indicates that the three genes are related to the development of digestive system. Additionally, expression of the three genes was decreased after metamorphosis, while Rv-NOS and Rv-CCKR were increasingly expressed in competent larvae, which may help the larvae find suitable environments and promote digestive system development for metamorphosis, and the result of 5-HT IHC analysis also reflects the development of neuroendocrine system. Furthermore, results show that CCK can effect the expression of digestive enzyme, NOS and 5-HT receptor. Finally, based on the present results, we hypothesized that CCK and CCK receptor may be critical regulatory factors of food habit transition and metamorphosis. These results might provide information on the development of neuroendocrine system of R. venosa, and new insight into the regulation of the food habit transition and metamorphosis of gastropods.