Juvenile Intestine Research Articles

Histo-architectural and histochemical changes in the liver and intestine of Labeo rohita: integrative effect of water temperature and dietary protein level

This study aimed to study the histo-architectural and histochemical changes in the liver and intestine of Labeo rohita fingerlings due to the integrative effect of short-term exposure to higher temperature and dietary protein levels. Six hundred Labeo rohita fingerlings (average weight 6.78 ± 0.05 g) were distributed into 24 tanks, with 25 fingerlings in each tank. The tanks were divided into eight experimental groups, with three replicates for each tank. Half of the experimental groups were maintained at an ambient water temperature of 260C, while the other half were kept at 320C for one week and then shifted back to 260C for four weeks. The fingerlings were fed with either of four diets, each containing different protein levels of 20%, 30%, 40% or 45% protein. At the end of the experiment, the hepatosomatic index (HSI) and visceral index (VI) of the juveniles were increased with the increase in dietary protein level, however significantly lower HSI was recorded at 320C compared to 260C. Juveniles exposed to elevated temperature (320C) for one week registered significantly higher (p < 0.05) liver glycogen content compared to 260C. Amylase, protease, and alkaline phosphatase activity in the intestine of juveniles were significantly (p < 0.05) higher at elevated temperature (320C) and decreased after 4 weeks of decrease in temperature from elevated temperature (320C) to ambient temperature (260C). The 45% CP fed group at 260C showed mildly desquamated mucosa in the liver whereas mucosa was found absent at 320C. Marked loss of mucosa was found in the intestine of L. rohita fed with 45% dietary protein after five weeks either at 260C or 320C. Overall it concludes that the dietary protein level and water temperature interactions are more effective in maintaining the histo-architectural structure of the liver and intestine, which responds to increased digestive enzyme activity.

Characterization of microbiota and histology of cultured sea cucumber Isostichopus badionotus juveniles during an outbreak of skin ulceration syndrome.

Due to the dramatic reduction of sea cucumber Isostichopus badionotus populations in the Yucatan Peninsula by overfishing and poaching, aquaculture has been encouraged as an alternative to commercial catching and restoring wild populations. However, the scarcity of broodstock, the emergence of a new disease in the auricularia larvae stage, and the development of skin ulceration syndrome (SUS) in the culture have limited aquaculture development. This study presents the changes in the intestine and skin microbiota observed in early and advanced stages of SUS disease in cultured juvenile I. badionotus obtained during an outbreak in experimental culture through 16S rRNA gene sequencing and histological evidence. Our results showed inflammation in the intestines of juveniles at both stages of SUS. However, more severe tissue damage and the presence of bacterial clusters were detected only in the advanced stages of SUS. Differences in the composition and structure of the intestinal and skin bacterial community from early and advanced stages of SUS were detected, with more evident changes in the intestinal microbial communities. These findings suggest that SUS was not induced by a single pathogenic bacterium. Nevertheless, a decrease in the abundance of Vibrio and an increase in Halarcobacter (syn. Arcobacter) was observed, suggesting that these two bacterial groups could be keystone genera involved in SUS disease.

Comparative study on bacterial flora of the intestine in Persian sturgeon (Acipenser persicus) fingerlings reared in fiberglass tanks and earthen ponds

Stability of bacterial flora in fish intestine is very important, because the intestine is an important organ for outbreak of microbial infections and other fish diseases especially when the fish have not been vaccinated. The aim of this study was to determine the bacterial flora of intestine in sturgeon juvenile in earthen ponds. The results can be applied to prevent the diseases occurrence and health management. In this study, 90 individuals of Persian sturgeon ranged 3-5g in weight collected randomly by trawling in 3 earthen ponds as well as 15 individuals ranged 10-20g in weight by small net in 3 fiberglass tanks. After recording morphometric characteristics, the intestine fish and rearing water were cultured on TSA medium. Gram staining and complementary tests were conducted. In order to identify the bacterial species, various biochemical experiments and diagnostic kits of API 20E (special for gram - negative bacteria) were employed. According to morphometric measurements, in earthen ponds the mean weight and length of juveniles were 5.59 ± 3.18 and 11.4 ± 2.9, respectively. The results showed that in these ponds the mean facultative aerobic and anaerobic bacterial counts in the juvenile intestine were 5.59 ± 0.92 (log CFU.g-1) compared to 6.67 ± 0.34 (log CFU.ml-1) in rearing water. Furthermore, the following bacteria were found in the intestine of Persian sturgeon: Aeromonas sp., A. sobria, A. hydrophyla, Entrobacteriaceae and Corynebacterium, while the bacteria recovered from the rearing water were Aeromonas sp. and A. sobria. According to morphometric measurements, in the fiberglass tanks, the mean weight and length of juveniles were 12.13 ± 2.51 (g) and 15.11 ± 1.13 (cm), respectively. The results showed that in these tanks, the mean facultative aerobic and anaerobic bacterial counts in the fish intestine were 4.77 ± 0.04 (Log CFU.g-1) compared to 4.81 ± 1 (Log CFU/ml) in rearing water. Furthermore, the following bacteria were identified in the intestine of Persian sturgeon: Aeromonas sp., Micrococcus, Staphylococcus. The bacteria in the rearing water were A. sobria, Acinetobacter, Moraxella, Micrococcus and Staphylococcus.

Cloning and characterization of the first serine carboxypeptidase from a plant parasitic nematode, Radopholus similis

Radopholus similis is an important parasitic nematode of plants. Serine carboxypeptidases (SCPs) are peptidases that hydrolyse peptides and proteins and play critical roles in the development, invasion, and pathogenesis of certain parasitic nematodes and other animal pathogens. In this study, we obtained the full-length sequence of the SCP gene from R. similis (Rs-scp-1), which is 1665 bp long and includes a 1461-bp open reading frames encoding 486 amino acids with an 18-aa signal peptide. This gene is a double-copy gene in R. similis. Rs-scp-1 was expressed in the procorpus, esophageal glands and intestines of females and in the esophageal glands and intestines of juveniles. Rs-scp-1 expression levels were highest in females, followed by juveniles and males, and lowest in eggs. Rs-scp-1 expression levels were significantly suppressed after R. similis was soaked in Rs-scp-1 dsRNA for 12 h. Nematodes were then inoculated into Anthurium andraeanum after RNAi treatment. Compared with water treatment, R. similis treated with RNAi were reduced in number and pathogenicity. In summary, we obtained the first SCP gene from a plant parasitic nematode and confirmed its role in the parasitic process.

A complete chitinolytic system in the atherinopsid pike silverside Chirostoma estor: gene expression and activities.

The expression and digestive activity of pike silverside Chirostoma estor endogenous chitinases were analysed in samples from four life stages: whole eggs; larvae; juvenile intestine and hepatopancreas and adult intestine and hepatopancreas. A chitinase cDNA was cloned and partially sequenced (GenBank accession number: FJ785521). It was highly homologous to non-acidic chitinase sequences from other fish species, suggesting that it is a chitotriosidase. Quantitative PCR showed that this chitinase was expressed throughout the life span of C. estor, with maximum expression in the hepatopancreas of juveniles. Chitotriosidase and chitobiosidase activities were found at all life stages, along with a very high level of N-acetyl glucosaminidase (NAGase). The chitotriosidase activity could be encoded by the cloned complementary (c)DNA, although additional chitinase genes may be present. The chitotriosidase activity appeared to be transcriptionally regulated only at the juvenile stage. The expression and activity of chitinases tended to increase from the early to juvenile stages, suggesting that these variables are stimulated by chitin-rich live food. Nevertheless, the feeding of juvenile and adult fish with both live food and a balanced commercial diet seemed to provoke significant reductions in pancreatic NAGase secretion and/or synthesis in the gut. Moreover, all chitinase activities were lower in adults, probably reflecting a higher intake and use of the balanced diet. The observation of chitotriosidase and chitobiosidase activities together with a very high NAGase activity suggest the presence of a complete and compensatory chitinolytic chitinase system that enables this stomachless short-gut fish species to use chitin as an energy substrate. These novel findings suggest that dietary inclusions of chitin-rich ingredients or by-products might reduce the farming costs of C. estor without impairing performance.

A Nematode Calreticulin, Rs-CRT, Is a Key Effector in Reproduction and Pathogenicity of Radopholus similis.

Radopholus similis is a migratory plant-parasitic nematode that causes severe damage to many agricultural and horticultural crops. Calreticulin (CRT) is a Ca2+-binding multifunctional protein that plays key roles in the parasitism, immune evasion, reproduction and pathogenesis of many animal parasites and plant nematodes. Therefore, CRT is a promising target for controlling R. similis. In this study, we obtained the full-length sequence of the CRT gene from R. similis (Rs-crt), which is 1,527-bp long and includes a 1,206-bp ORF that encodes 401 amino acids. Rs-CRT and Mi-CRT from Meloidogyne incognita showed the highest similarity and were grouped on the same branch of the phylogenetic tree. Rs-crt is a multi-copy gene that is expressed in the oesophageal glands and gonads of females, the gonads of males, the intestines of juveniles and the eggs of R. similis. The highest Rs-crt expression was detected in females, followed by juveniles, eggs and males. The reproductive capability and pathogenicity of R. similis were significantly reduced after treatment with Rs-crt dsRNA for 36 h. Using plant-mediated RNAi, we confirmed that Rs-crt expression was significantly inhibited in the nematodes, and resistance to R. similis was significantly improved in transgenic tomato plants. Plant-mediated RNAi-induced silencing of Rs-crt could be effectively transmitted to the F2 generation of R. similis; however, the silencing effect of Rs-crt induced by in vitro RNAi was no longer detectable in F1 and F2 nematodes. Thus, Rs-crt is essential for the reproduction and pathogenicity of R. similis.

‘Candidatus Paenicardinium endonii’, an endosymbiont of the plant-parasitic nematode Heterodera glycines (Nemata: Tylenchida), affiliated to the phylum Bacteroidetes

Bacteria-like endosymbionts of females of the plant-parasitic nematodes Globodera rostochiensis and Heterodera goettingiana and juveniles of Heterodera glycines were first observed during transmission electron microscopy (TEM) studies conducted in the 1970s. These organisms were characterized as being rod-shaped, ranging in size from 0.3 to 0.5 microm in diameter and 1.8 to 3 microm in length and containing structures labelled as striated inclusion bodies or tubular structures. A population of H. glycines was obtained from the soybean field where infected nematodes were first discovered in order to conduct TEM studies of females and males and to determine the phylogenetic position of the H. glycines endosymbiont among bacteria by studying the 16S rRNA and gyrB gene sequences. The bacterium was observed in the pseudocoelom and intestine of juveniles, females and males, in hypodermal chords of juveniles and males, in ovary walls and in oocytes and spermatozoa. The bacterium was polymorphic, measuring 0.4-0.8 x 2.5-4.5 microm, and many specimens contained an array of microfilament-like structures similar to those observed in "Candidatus Cardinium hertigii", the endosymbiont of Encarsia spp. wasps. Phylogenetic analysis of the 16S rRNA and gyrB genes of the H. glycines-infecting bacterium revealed 93 % and 81 % sequence identity, respectively, to the homologous genes in "Candidatus C. hertigii". Thus, the name "Candidatus Paenicardinium endonii" is proposed for the bacterial endosymbiont of the plant-parasitic nematode H. glycines.

Nutrient digestibility and intestinal enzyme activity of Clarias batrachus (Linn.) juveniles fed on dried fish and chicken viscera incorporated diets

A feeding trial was conducted for 56 days to study the effect of replacement of fish meal by dried fish and chicken viscera, and a combination of oil cakes, in the diet of Clarias batrachus juveniles. The nutritional values of these by-products were studied through a digestibility experiment. No significant difference in nutrient digestibility was observed in different diets. Even 19.59% lipid in the diet of catfish did not affect the nutrient digestibility. Both amylolytic and proteolytic enzymes in the intestine of juveniles were studied. A decreased protease activity due to replacement of animal protein by plant protein and a decreased ( P < 0.01) aspartate aminotransferase (ASAT) activity could be observed after inclusion of 22% of dried fish viscera in the diet of the catfish. Though body lipid content increased in fish fed a high level of lipid, fat-free body composition did not vary among the fish fed on different diets.