The influence of coconut oil on the growth, immune, and antioxidative responses and the intestinal digestive enzymes and histomorphometry features of Nile tilapia (Oreochromis niloticus)

The trials of finding non-conventional and alternative aquafeed ingredients are increasing. In this sense, this study evaluated the influence of coconut oil on the growth, feed utilization, immune, and antioxidative responses of Nile tilapia. Five test diets were formulated by mixing coconut oil with the other ingredients at 0, 1, 2, 3, and 4% of the total ration and presented for tilapia for 60 successive days. The final weight, SGR, weight gain (WG), and feed intake were superior in fish delivered 2% of coconut oil (P < 0.05). Concurrently, fish that received 2% coconut oil had lower FCR and higher PER than fish of the control and 4% groups (P < 0.05). Higher lipase activity was observed in fish of 2% and 3% levels than the remaining groups (P < 0.05). Besides, the amylase and protease activities of fish in 1%, 2%, and 3% groups were higher than the 0% level (P < 0.05). The total blood cholesterol, RBCs, and PCV showed higher values in Nile tilapia fed 2% and 3% coconut oil (P < 0.05). The lysozyme and phagocytic activities were higher in fish fed 2% and 3% levels than the control (P < 0.05), while the phagocytic index in 2% and 3% levels was higher than 0% and 4% levels. Furthermore, SOD and CAT were higher in fish fed 1%, 2%, and 3% than fish fed 0% and 4% levels while GSH was higher in fish of 1%, 2%, and 3% than fish fed 0% level (P < 0.05). However, the MDA level was markedly lower in fish fed 25, 3%, and 4% coconut oil than the 0% level (P < 0.05). The intestine's histological structure in all groups appeared normal, forming of intestinal villi projecting from the intestinal wall. Also, the structure of the hepatopancreas had a normal architecture in all groups. To sum up, the inclusion of coconut oil at 2 to 3% is recommended as a replacer for fish oil in Nile tilapia diets.

Effect of dietary supplementation with apple cider vinegar and propionic acid on hemolymph chemistry, intestinal microbiota and histological structure of hepatopancreas in white shrimp, Litopenaeus vannamei

This experiment was conducted to evaluate the effects of dietary supplementation of Apple cider vinegar (ACV) and propionic acid (PA) on biochemical parameters of hemolymph, intestinal microbiota and histology of hepatopancreas in white shrimp (Litopenaeus vannamei). Five experimental diets were evaluated in this study including diets supplemented with 1.0, 2.0 and 4.0% of ACV, 0.5% propionic acid, and a control diet with no supplements. Shrimps (initial weight of 10.2 ± 0.04 g) in triplicate groups with the density of 25 shrimps per tank were fed the diets for 60 days. At the end of the feeding trial, shrimps fed with ACV and PA supplemented diets had significantly higher total protein level than those fed the control diet (P < 0.05). The number of Vibrio spp., R-cells (lipid storage cells) of hepatopancreas and cholesterol level in shrimps fed the diets containing ACV and PA were lower compared to the control group (P < 0.05). However, there was no remarkable variations in glucose concentration, B-cell number and tubule diameter among the experimental diets (P > 0.05). In addition, shrimps fed the ACV diets had significantly lower total heterotrophic marine bacteria compared to the control or PA groups, and the lowest bacterial number was observed in shrimp fed 4% ACV supplemented diet (P < 0.05). Supplementation of 2 and 4% ACV as well as 0.5% PA in the diet led to a significantly higher calcium concentration than the control treatment (P < 0.05). The lowest triglyceride concentration was observed in the shrimps fed diets containing 2.0 and 4.0% ACV, which resulted in 15 and 20% reduction, respectively (P < 0.05). Overall, the findings indicates that ACV and PA possess antimicrobial activity and demonstrate beneficial effects on health status, so they can be potentially used as feed additive in the feeding of L. vannamei.

Morphology and ultrastructure of the midgut gland ("hepatopancreas") during ontogeny in the common spider crab Maja brachydactyla Balss, 1922 (Brachyura, Majidae)

We studied the anatomy and cytology of the midgut gland (MGl) of the common spider crab Maja brachydactyla Balss, 1922 at several life stages (zoea, megalopa, first juvenile, and adult) using dissection, histology, electron microscopy, computed tomography, and micro-computed tomography (micro-CT). In newly hatched larvae, 14 blind-end tubules form the MGl. The length of the tubules increases during the larval development. In the late megalopa, the number of tubules also increases. In adults, 35,000 to 60,000 blind-ending tubules comprise the MGl. In all life stages, a square-net network of muscle fibers surround the tubules. We describe five cell types in the MGl in all larval stages, which have a similar location, histology, and ultrastructure in larvae and adults: embryonary (E-) cells, resorptive (R-) cells, fibrillar (F-) cells, blister-like (B-) cells, and midget (M-) cells. Major difference between larval and adult cells is the larger size of the adult cells. Microapocrine secretion occurs from the microvilli of the B-cells. No ultrastructural changes were observed during larval development, which suggests that the function of each cell type might be similar in all life stages. The role of each epithelial cell type in larvae and adults is discussed.

Effect of starvation and refeeding on the hepatopancreas of whiteleg shrimp Penaeus vannamei (Boone) using computer-assisted image analysis

Under normal farming conditions, shrimp can experience starvation periods attributable to disease outbreaks or adverse environmental conditions. Starvation leads to significant morphological changes in the hepatopancreas (HP), being the main organ for absorption and storage of nutrients. In the literature, limited research has described the effect on the HP of periods of starvation followed by refeeding and none in whiteleg shrimp (Penaeus vannamei) using computer-assisted image analysis (CAIA). This study describes the effect of starvation and starvation followed by refeeding on the HP of whiteleg shrimp using CAIA. Visiopharm^® software was used to quantify the following morphological parameters, measured as ratio to the total tissue area (TLA): total lumen area (TLA:TTA), haemocytic infiltration area in the intertubular spaces (HIA:TTA), B-cell vacuole area (VBA:TTA), lipid droplet area within R cells (LDA:TTA) and F-cell area (FCA:TTA). Significant changes were measured for HIA:TTA and LDA:TTA during starvation (increase in HIA:TTA associated with decrease in LDA:TTA) and starvation followed by refeeding (decrease in HIA:TTA associated with increase in LDA:TTA). In the future, HIA:TTA and LDA:TTA have the potential to be used in a pre-emptive manner to monitor the health of the HP, facilitate early diagnosis of diseases and study the pathophysiology of the organ.

Compensatory Growth in Juveniles of Freshwater Redclaw Crayfish Cherax quadricarinatus Reared at Three Different Temperatures: Hyperphagia and Food Efficiency as Primary Mechanisms

Feeding restriction, as a trigger for compensatory growth, might be considered an alternative viable strategy for minimizing waste as well as production costs. The study assessed whether juvenile redclaw crayfish Cherax quadricarinatus (initial weight 0.99 ± 0.03 g) was able to compensate for feeding restriction at different temperatures (23 ± 1, 27 ± 1 and 31 ± 1 ° C). Hyperphagia, food utilization efficiency, energetic reserves, and hepatopancreas structure were analyzed. Three temperatures and two feeding regimes (DF-daily fed throughout the experiment and CF- 4 days food deprivation followed by 4 days of feeding, intermittently) were tested. The restriction period was from day 1 to 45, and the recovery period was from day 45 to 90. The previously restricted crayfish held at 23, 27, and 31 ± 1 ° C displayed complete body weight catch-up through compensatory growth following the restriction period with depressed growth. The mechanisms that might explain this response were higher feed intake (hyperphagia), and increased food utilization efficiency. Hepatopancreatic lipids were used as a metabolic fuel and hepatosomatic index was reduced in the previously restricted crayfish, but recovery at the same level of unrestricted crayfish occurred after the shift to daily feeding. The highest temperature affected adversely growth, feed intake, food efficiency, and metabolism of crayfish, whereas the lowest temperature and feeding restriction induced a more efficient growth of the crayfish.

Bioaccumulation of cadmium and lead and its effects on hepatopancreas morphology in three terrestrial isopod crustacean species

This study was designed to compare cadmium (Cd) and lead (Pb) bioaccumulation in three species of oniscidean isopods - Armadillidium granulatum Brandt, Armadillidium vulgare (Latreille) and Porcellio laevis Latreille which were exposed for three weeks to a contaminated diet, and to determine the morphological and ultrastructural changes in hepatopancreas. Metal accumulation, determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), was linearly associated with the exposed concentration and was a function of the metal and the species tested. All three species accumulated lower levels of Pb than Cd. A. vulgare accumulated the largest concentration of Pb, especially at the higher doses, whereas P. laevis showed the greatest Cd accumulation, and the highest Cd concentration was lethal for all exposed species. The highest concentrations of Pb and Cd induced significant changes both in the general morphology of tubules and in the ultrastructural organization of epithelial cells in hepatopancreas. Some Pb/Cd induced alterations include: brush border disorganization; reduction of the basal labyrinth formed by the plasma membrane; condensation of some cytoplasm areas and of chromatin; rough endoplasmic reticulum and mitochondrial alterations; increase of secondary lysosomes and of type B granules in S cells. Some of the ultrastructural changes observed overlap with those induced by prolonged starvation, whereas others can be useful biomarkers of heavy metal toxicity. This study has confirmed that in terrestrial isopods, the accumulation of the different metals occurs in a species-specific manner; therefore ecological monitoring and assessment studies should consider each species individually. The research has confirmed that in the terrestrial isopods the accumulation of the different metals occurs in a species-specific way; therefore each species should first be evaluated in view of its employ in biomonitoring programs.

Morphologic study of the liver of lambari (Astyanax altiparanae) with emphasis on the distribution of cytokeratin

Studies on the morphology of the liver of teleosts reflect some controversy in the interpretation of the data, but also provide confirmation of variations in the structure of the organ in several species. Thus, we intend to understand the specific structural organization of the liver of Astyanax altiparanae. Specimens were collected in the city of Andirá, Paraná, Brazil. The livers were processed according to histological routine for inclusion in Paraplast, and the sections were stained with HE and Mallory's trichrome or followed the protocol for fluorescence immunohistochemistry, anti-cytokeratin. The liver of A. altiparanae was covered by a capsule of connective tissue, without delimiting lobes. The hepatocytes had an arrangement in cords around sinusoids. Melanomacrophage centers were observed. The vascular components and intrahepatic pancreatic acini were distributed between hepatocytes. Presence of cytokeratin was detected in tissues that lined the liver and endothelial cells of sinusoids. The comparison of the liver of A. altiparanae to other characids corroborates with the fact that there is variation in the morphology of the liver even between closely related species. Moreover, it appears that in this species, endothelial cells of sinusoids can synthesize the cytokeratin filaments required for the regulation of blood flow in capillaries in adults.

Effect of copper on morphology, weight, and chromosomal aberrations in the spiny lobster, Panulirus homarus (Linnaeus, 1758)

Spiny lobster Panulirus homarus which had been exposed to cupric ion at 9.55 and 19.1 μg/l for 28 days was examined for sub-lethal effects including morphology, wet weight, and induced genotoxic effect on the chromosome. Following cupric exposure, the color of lobster P. homarus changed from yellowish-brown to greenish black in the hepatopancreas, changed from normal creamy white to yellowish white in the muscle, and changed to greenish black in the gill. A significant change in the percentage of wet weight of muscle (28.70 ± 0.41-23.47 ± 0.45), hepatopancreas (4.03 ± 0.12-2.63 ± 0.17), and gills (3.63 ± 0.45-3.87 ± 0.12) were observed in the copper-treated lobsters. The diploid number of chromosomes of P. homarus was over 200 metaphases from ten lobsters, as 2n = 58, and consisted of 16 acrocentric, seven metacentric, and six sub-metacentric chromosomes. The lobsters exposed to cupric ion at 9.55 and 19.1 μg/l showed different types of chromosomal aberrations such as centromeric gaps, chromatid breaks, centromeric fusion, stickiness, ring chromosomes, and acrocentric association region. The frequency of aberrations increased with duration of exposure. In conclusion, it was suggested that cupric ion interacts with the spindle formation and consequently distorts the normal karyomorphology, indicating cytogenetic effect on lobster.

Evaluation of halofenozide against prey mosquito larvae Culex pipiens and the predator fish Gambusia affinis: impact on growth and enzymatic activities

Culex pipiens (Diptera: Culicidae) is the most widely distributed mosquito species in Algeria and many other countries in the world. Mosquitoes are generally controlled by conventional insecticides but these may pose strong secondary effects on the environment. In this context, the insect growth regulators (IGRs) have shown promise in controlling pest insects. Halofenozide (23% EC) is a novel IGRs belonging to the class of non-steroidal ecdysone agonists, and it was found toxic for larvae of C. pipiens. In addition biological methods constitute an alternative to chemical control. Several fish species have been tested against mosquitoes, and Gambusia affinis was found very efficient. In the present study we evaluated the impact of this new potent insecticide (halofenozide) on growth and metric indexes in the larvivorous fish G. affinis under laboratory conditions. In addition, the effects were evaluated on the enzymatic activities of acetyl cholinesterase (AChE) and glutathione S-transferase (GST). The insecticide was added in water at two concentrations (12.6 and 28.6 microg/L) corresponding to the LC50 and LC90 obtained against fourth instar larvae of C. pipiens, and adult females of G. affinis were exposed to halofenozide for 30 days. At different exposure times we measured the length and weight of fishes, the index of condition (K), the gonado-somatic ratio (GSR) and the hepato-somatic ratio (HSR). The results showed that halofenozide had no significant (p>0.05) effects on growth, metric indexes and AChE activities. However, treatment caused a significant induction (p<0.05) in GST activities at days 15 and 30 with the highest dose. Our results indicate that this ecdysteroid agonist presented only minor secondary effects on the non-target fish species, and so it has potential for controlling of mosquitoes in an integrated manner.

Lysosomal responses and metallothionein induction in the blue mussel Mytilus edulis from the south-west coast of Iceland

It has recently been emphasized that high levels of inorganic and organic micropollutants (particularly organometals, POPs and PAHs) may be present in coastal waters at high latitudes, stressing the need to evaluate the effects of contaminants on marine organisms from sub-arctic zones. With this aim, specimens of the blue mussel Mytilus edulis were sampled in polluted and reference areas along the south-west coast of Iceland in July 2004. Samples were collected from the intertidal zone at three sites in Reykjavik harbour which are differently exposed to contaminants, and at three reference coastal sites, two located along the Reykjanes Peninsula and the third one on the northern part of Hvalfjordur fiord. Lipofuscin content, neutral lipid accumulation and lysosomal enlargement were evaluated in digestive cells from cryostat sections of the mussel hepatopancreas, and quantified by automated image analysis. Metallothionein induction was also determined in the same tissue. Results indicate that mussels from the inner part of Reykjavik harbour, which is the most sheltered and most influenced by extensive shipping traffic, were the worst affected, with the highest values in neutral lipids, lipofuscin and lysosomal swelling. At the other two harbour sites, mussels exhibited lower values, similar to those observed in organisms collected in Hvalfjordur fiord and in bay of Osar. Mussels from Kuagerdi had the lowest values.

Fgf10 regulates hepatopancreatic ductal system patterning and differentiation

During organogenesis, the foregut endoderm gives rise to the many different cell types that comprise the hepatopancreatic system, including hepatic, pancreatic and gallbladder cells, as well as the epithelial cells of the hepatopancreatic ductal system that connects these organs together and with the intestine. However, the mechanisms responsible for demarcating ducts versus organs are poorly understood. Here, we show that Fgf10 signaling from the adjacent mesenchyme is responsible for refining the boundaries between the hepatopancreatic duct and organs. In zebrafish fgf10 mutants, the hepatopancreatic ductal epithelium is severely dysmorphic, and cells of the hepatopancreatic ductal system and adjacent intestine misdifferentiate toward hepatic and pancreatic fates. Furthermore, Fgf10 also functions to prevent the differentiation of the proximal pancreas and liver into hepatic and pancreatic cells, respectively. These data shed light onto how the multipotent cells of the foregut endoderm, and subsequently those of the hepatopancreatic duct, are directed toward different organ fates.