Development of digestive enzyme activity in spotted rose snapper,Lutjanus guttatus (Steindachner, 1869) larvae

We describe digestive enzyme activity during the larval development of spotted rose snapper, Lutjanus guttatus. Trypsin, chymotrypsin, leucine aminopeptidase, pepsin, amylase, lipase, and acid and alkaline phosphatase activities were evaluated using spectrophotometric techniques from hatching through 30 days. The spotted rose snapper larvae present the same pattern of digestive enzyme activity previously reported for other species in which pancreatic (i.e., trypsin, chymotrypsin, amylase, and lipase) and intestinal (i.e., acid and alkaline phosphatases and leucine aminopeptidase) enzymatic activities are present from hatching allowing the larvae to digest and absorb nutrients in the yolk-sac and live prey by the time of first feeding. The digestive and absorption capacity of the spotted rose snapper increases during the larval development. A significant increase in individual activity of all enzymes occurs at 20 DAH, and around 25 DAH, the juvenile-type of digestion is observed with the appearance of pepsin secreted by the stomach, suggesting that maturation of the digestive function occurs around 20–25 DAH. Our results are in agreement with a previous suggestion that early weaning may be possible from 20 DAH. However, the patterns of enzymatic activities reported in our study should be considered during the formulation of an artificial diet for early weaning of the spotted rose snapper.     

Dietary modulation of digestive enzymes by the administration of feed additives to rainbow trout,Oncorhynchus mykiss Walbaum

The aim of this study was to assess the metabolic and digestive enzyme activities in rainbow trout, Oncorhynchus mykiss Walbaum fed dietary supplements. The biometric indices and the following enzymes activities were measured: acid protease and pepsin from the stomach homogenates, alkaline phosphatase (AP) from the small intestine and the brush border membrane, total proteolytic enzymes and trypsin from the small intestine and liver/pancreas. Dietary garlic induced a higher pepsin activity in the stomach than lipopolysaccharide (LPS) and ginger. Conversely, dietary ginger and LPS showed a significant difference (P > 0.05) in acid protease activity compared to the controls. There was not any significant difference observed between treated groups and the controls for hepato‐pancreas proteolytic enzyme activity, except for trypsin. AP activity increased significantly with dietary garlic, ginger and LPS compared to the controls.     

Changes in digestive enzyme activities during larval development of leopard grouper (Mycteroperca rosacea)

The leopard grouper is an endemic species of the Mexican Pacific with an important commercial fishery and good aquaculture potential. In order to assess the digestive capacity of this species during the larval period and aid in the formulation of adequate weaning diets, this study aimed to characterize the ontogeny of digestive enzymes during development of the digestive system. Digestive enzymes trypsin, chymotrypsin, acid protease, leucine–alanine peptidase, alkaline phosphatase, aminopeptidase N, lipase, amylase and maltase were quantified in larvae fed live prey and weaned onto a formulated microdiet at 31 days after hatching (DAH) and compared with fasting larvae. Enzyme activity for trypsin, lipase and amylase were detected before the opening of the mouth and the onset of exogenous feeding, indicating a precocious development of the digestive system that has been described in many fish species. The intracellular enzyme activity of leucine–alanine peptidase was high during the first days of development, with a tendency to decrease as larvae developed, reaching undetectable levels at the end of the experimental period. In contrast, activities of enzymes located in the intestinal brush border (i.e., aminopeptidase and alkaline phosphatase) were low at the start of exogenous feeding but progressively increased with larval development, indicating the gradual maturation of the digestive system. Based on our results, we conclude that leopard grouper larvae possess a functional digestive system at hatching and before the onset of exogenous feeding. The significant increase in the activity of trypsin, lipase, amylase and acid protease between 30 and 40 DAH suggests that larvae of this species can be successfully weaned onto microdiets during this period.     

Ontogenic development of enzymatic activity and digestive system in Jullien's golden carp (Probarbus jullieni Sauvage, 1880)

Ontogenic development of the main enzymes and histological structure of digestive organs were studied in Jullien's golden carp (Probarbus jullieni) from hatching until 50 days after hatching (DAH). The larval fish were produced by artificial insemination and fed only Moina sp. till end of experiment. Body weight (mg) and total length (cm) of Jullien's golden carp increased exponentially and linearly. The results indicate the fish weight grew fast with increasing rate, while length increased at a constant rate over the studied period. Up‐regulation of acid protease was observed in newly hatched larvae and the specific activity gradually decreased with time. Trypsin specific activity was relatively stable within the first 35 DAH, while fluctuations in chymotrypsin were observed. Among these three proteolytic enzymes, acid proteases exihibited relatively high specific activity in newly hatched larvae, suggesting a role in yolk protein degradation. Alkaline proteases became more prominent with age and correlated with an abrupt decrease in acid proteases. Increased lipase‐specific activity appeared within 3 DAH and then gradually decreased with time, indicating the capacity to digest yolk lipid reserve. Amylase and cellulase‐specific activities changed in a similar manner, and the sensitivity to time was higher in amylase than in cellulase. The digestive organs and accessory organs developed around 3–5 DAH. However, intestinal histology was almost fully developed around 18 DAH. These findings should be useful for deciding the preferred timing for weaning, as well as on developing artificial diets referenced to the physiological changes of digestive enzymes.     

泥鳅仔稚鱼发育期间消化酶及碱性磷酸酶比活力的变化

研究了泥鳅(Misgurnus anguillicaudatus)从孵化至30 DAH(日龄,Days after hatching)几种消化酶及碱性磷酸酶比活力的变化情况。胃蛋白酶直至30 DAH仍未检出活性。而胰蛋白酶表现出较高的比活力,其比活力在初次摄食之后显著上升,6 DAH达到最大值之后开始显著降低(P<0.05)。脂肪酶与淀粉酶的变化模式相似,在内源性营养向外源性营养转变及仔鱼向稚鱼转变这两个时间段出现两个高峰值。碱性磷酸酶比活力在2-6 DAH显著上升(P<0.05),之后开始下降并趋于平稳。研究表明,泥鳅在仔稚鱼阶段只具有结构性的胃而缺乏分泌细胞的分化。2-6 DAH是泥鳅仔鱼肠道功能迅速发育的阶段,也是向成鱼消化模式转变的一个重要过程。脂肪酶和淀粉酶比活力的持续性表明了泥鳅仔鱼对糖类和脂肪有较好的利用能力。     

Post-prandial protease activity in the digestive tract of African catfish Clarias gariepinus larvae fed decapsulated cysts of Artemia

The alkaline proteolytic activity in the gut of African catfish larvae was studied during short time ranges from 30 min to 4 h after ingestion of decapsulated Artemia cysts. The variation in total protease and trypsin activities during the day was monitored during starvation, after one single meal ingestion, and during continuous feeding. In starved larvae the enzymatic activity was low and did not change in time. No significant endogenous secretion of digestive enzymes was detected. The level of alkaline proteolytic activity found in starved larvae was further considered as the basal level. In larvae fed only one meal during the day, the enzyme activity significantly increased from 3 h post-feeding up to a maximum level found 12 h after feeding. In the larvae receiving a meal every 4 h, the effect of feeding on the proteolytic activity was significantly different from the one in fish fed only once a day. The total protease activity in this dietary treatment changed according to the time of feeding and fluctuated around a constant level, which was intermediate between the maximum and the basal level. No rhythmic cycle of enzyme production in the fish was observed when the proteolytic activity was studied during a cycle of 24 h. When specific trypsin activity was measured, a similar pattern was found as with the total protease. The contribution of digestive enzymes from Artemia to the total digestion of food by the catfish larvae was calculated to be less than 1% of the total amount of the proteolytic activity measured in the larval gut.     

Ontogenetic development of digestive enzymes in yellowtail kingfish Seriola lalandi larvae

The development of digestive enzymes was examined in laboratory-reared yellowtail kingfish larvae from hatching to 36 days after hatching (DAH). The specific activities of amylase, lipase, and alkaline phosphatase showed three distinct phases: a sharp increase in enzyme activity from hatching to the onset of exogenous feeding on 3 DAH, followed by a fluctuation and a general decline toward 18 DAH, and then a period of low activity from 18 to 36 DAH. The total activities of these three enzymes showed a gradual increase from hatching to 18 DAH, followed by a sharp increase toward 36 DAH. In contrast to other enzymes, the specific and total activities of trypsin reached the maximum on 15 DAH and 24 DAH, respectively, and then both activities declined to low levels toward 36 DAH. The dynamics of digestive enzymes corresponded to the anatomical development of the digestive system. The enzyme activities tend to be stable after the formation of gastric glands in the stomach on 15 DAH. The composition of digestive enzymes indicates that yellowtail kingfish is able to digest protein, lipid and carbohydrates at an early stage. However, due to the low level of amylase specific activity after 18 DAH, the carbohydrate component should remain at a low level in formulated diets for fish larvae.     

Proteolytic Activity in California Halibut Larvae (Paralichthys californicus)

The digestive tract of many marine fish larvae undergoes numerous morphological and functional changes during ontogeny that can substantially influence larval survival under culture conditions. Increasing our knowledge of the digestive capacity and nutritional requirements of the larvae of new candidate species for aquaculture will aid in the development of optimal feeding protocols and greatly improve production under hatchery conditions. In this study, we assess the proteolytic capacity of California halibut (Paralichthys californicus) larvae using biochemical and histological analyses. Newly hatched larvae were reared in a semiclosed recirculating system and fed with highly unsaturated fatty acid (HUFA)–enriched rotifers from hatching until 19 d posthatch (dph) and HUFA‐enriched Artemia nauplii thereafter. Total and specific activity of trypsin and leucine‐aminopeptidase (LAP) and acid and alkaline protease activities were assessed throughout development using spectrophotometric techniques. Trypsin‐like activity and LAP and alkaline protease activities were detected shortly after hatching and before the opening of the mouth. Acid protease activity was not detected until 36–40 dph, concomitant with the development of the gastric glands. The specific activity of trypsin and LAP showed two distinct peaks at 8 and 20 dph. The second peak coincided with the shift from rotifers to Artemia. Hence, newly hatched California halibut larvae possess alkaline proteolytic activity before first feeding. Based on the digestive capacity evaluated in this study and the timing of the development of the functional stomach, we propose that California halibut can be adequately weaned to formulated microdiets around 36 dph.     

Developmental changes in digestive enzyme activity in American shad, <Emphasis Type="Italic">Alosa sapidissima</Emphasis>, during early ontogeny

In order to assess the digestive physiological capacity of the American shad Alosa sapidissima and to establish feeding protocols that match larval nutritional requirements, we investigated the ontogenesis of digestive enzymes (trypsin, amylase, lipase, pepsin, alkaline phosphatase, and leucine aminopeptidase) in larvae, from hatching to 45 days after hatching (DAH). We found that all of the target enzymes were present at hatching, except pepsin, which indicated an initial ability to digest nutrients and precocious digestive system development. Trypsin rapidly increased to a maximum at 14 DAH. Amylase sharply increased until 10 DAH and exhibited a second increase at 33 DAH, which coincided with the introduction of microdiet at 30 DAH, thereby suggesting that the increase was associated with the microdiet carbohydrate content. Lipase increased until 14 DAH, decreased until 27 DAH, and then increased until 45 DAH. Pepsin was first detected at 27 DAH and then sharply increased until 45 DAH, which suggested the formation of a functional stomach. Both alkaline phosphatase and leucine aminopeptidase markedly increased until 18 DAH, which indicated intestinal maturation. According to our results, we conclude that American shad larvae possess the functional digestive system before mouth opening, and the significant increases in lipase, amylase, pepsin, and intestinal enzyme activities between 27 and 33 DAH suggest that larvae can be successfully weaned onto microdiets around this age.     

Ontogeny of the digestive tract and enzymes in rock bream Oplegnathus fasciatus (Temminck et Schlegel 1844) larvae

Histological development of the digestive tract and specific activities of three digestive enzymes (trypsin, alkaline phosphatase, and pepsin) were studied in rock bream Oplegnathus fasciatus from hatching to 50 days after hatching (DAH). At hatching, the digestive tract appeared as an undifferentiated straight tube and differentiated into the buccopharynx, esophagus, stomach, intestine, and rectum at mouth opening by 3 DAH. The taste bud and mandibular teeth were present in the buccopharyx at 8 DAH. The goblet cells appeared in the esophagus at 8 DAH and in the buccopharyx at 9 DAH. The stomach anlage was formed at 2 DAH and developed into cardia, fundus, and pylorus at 14 DAH. The gastric glands were visible at 16 DAH, and the pepsin was firstly detected on 22 DAH. At 2 DAH, the intestinal valve appeared and divided the intestine into anterior intestine (AI) and posterior intestine (PI). The rectum was differentiated from the PI at 3 DAH. The supranuclear vacuoles were visible in the rectum by 6 DAH, and the lipid inclusions were present in the AI at 8 DAH. The alkaline phosphatase was detected at 1 DAH, and the increase in its activity indicated the maturation of the intestine after 40 DAH. The hepatocytes and pancreatic cells were differentiated from the blast cells at 2 DAH, and the acidophilic zymogen granules in the exocrine pancreas were observed simultaneously. The trypsin was detected by 1 DAH and increased to the maximum at 19 DAH, followed by a decrease as the stomach became functional.     

Functional changes in digestive enzyme activities of meagre (Argyrosomus regius; Asso, 1801) during early ontogeny

The ontogenesis of main pancreatic and intestinal enzymes was investigated in the recent promising Mediterranean candidate species of meagre, Argyrosomus regius, during larval development until 40 days after hatching (DAH). The green-water technique was carried out for larval rearing. Whole-body homogenates were used for enzymatic analysis in larvae younger than 15 DAH; after this date, older larvae were dissected into two segments as pancreatic and intestinal segment. Trypsin was detected as early as hatching and sharply increased concurrently with age and exogenous feeding 15 DAH, but constant decline was observed until the end of experiment. Amylase was determined at 2 DAH and sharply increased 10 DAH. Then, slight decreases were found between 10 and 15 DAH, and then slow alterations were continued until the end of the experiment. Lipase was firstly measured on day 3; then, sudden decline was observed between 20 and 25 DAH. After this date, slow fluctuations were maintained until the end of the experiment. Pepsin was firstly assayed 15 DAH related to gastric gland secretion and sharply increased 30 DAH. Then, it slowly varied until end of the experiment. Enzymes of brush border membranes, alkaline phosphatase and aminopeptidase N showed similar pattern on specific activities during the first 10 days. Thereafter, while specific activity of alkaline phosphatase slightly decreased 15 and fluctuated until 20 DAH, aminopeptidase N activity slowly increased 20 DAH. Then, activity of alkaline phosphatase and aminopeptidase N constantly increased 30 DAH, indicating maturation of the intestinal digestive process, and also, these activities continued to slowly increase until the end of the experiment. The specific activity of cytosolic peptidase, leucine–alanine peptidase, smoothly increased on day 8, then fluctuated until 15 DAH. After this date, in contrast to enzymes of brush border membranes, it sharply decreased 25 DAH and continued to gradually decline until the end of the experiment. These converse expressions were indicative of a maturation of enterocytes and the transition of an adult mode of digestion.     

Comparative digestive enzyme ontogeny in two marine larval fishes: Pacific threadfin (Polydactylus sexfilis) and bluefin trevally (Caranx melampygus)

The specific activity of digestive enzymes; aspartic and serine protease, collagenase, lipase, acid and alkaline amylase, acid and alkaline phosphatase, and chitinase was assayed throughout early development in two species of marine fishes: the Pacific threadfin (Polydactylus sexfilis) and bluefin trevally (Caranx melampygus). Specific enzyme activities were determined on whole larval extracts sampled at selected stages of development, from day 0 to day 30 post-hatching. Similar developmental patterns of enzyme specific activity were observed in the two species, although differences in timing, amplitude and effects of first feeding were noted. Amylase activity increased prior to first feeding, peaking at the middle of the larval period, and becoming nearly undetectable by the time of larval-to-juvenile metamorphosis. Serine protease, collagenase, lipase and alkaline (and acid for threadfin) phosphatase activities increased gradually, followed by sharp increases to a plateau during the second half of larval development. Aspartic protease and chitinase activities, in addition to acid phosphatase (for trevally), were low to undetectable in the first half of development, increasing through metamorphosis. In the trevally only, this group of enzymes exhibited high activity levels at the time of hatching, followed by a precipitous drop. Species-dependent differences in enzyme specific activity at first feeding may have been a result of differences in yolk utilization. These results, taken in the context of earlier reports, lead us to conclude that carbohydrate utilization may play a significant role in the earlier phases of development among some marine larvae, followed by a shift to protein and lipid utilization.     

Digestive enzyme activity of the red porgy (Pagrus pagrus, L.) during larval development under culture conditions

The ontogenic development of the main digestive enzymes (proteases, amylase and lipase) in the red porgy, Pagrus pagrus, larvae was assayed during the larval development. The green water technique was carried out for larval rearing and whole‐body homogenates were used for enzymatic assays in triplicate. Significant alterations in specific activities of all digestive enzymes measured during the period of this study were mostly related to metamorphosis and weaning. Trypsin‐ and chymotrypsin‐specific activities were first detected on day 3, together with opening of the mouth, and slightly increased until 25 days after hatching (DAH). After this period, the specific activities of these enzymes slightly decreased. Pepsin was first detected on day 28, concurrent with stomach formation, and a sharp increase was observed until 30 DAH. A slight decrease was measured from this date until the end of the experiment. Both amylase and lipase were measured for the first time on days 2 and 4 respectively, and the specific activities of these enzymes showed similar patterns during the first week of the study. Then, slight variations were observed until 30 DAH and while lipase‐specific activity declined, an increase in the specific activity of amylase was found until the end of the experiment. It is concluded that the variations observed in the specific activity of digestive enzymes were related to either metamorphosis, such as the formation of the stomach (28 DAH), or to changes in food composition. The profile of the developmental pattern of the main digestive enzymes detected in P. pagrus is similar to that described for other Sparid species.     

Partial characterization of the digestive enzymes of Pacific bluefin tuna <Emphasis Type="Italic">Thunnus orientalis</Emphasis> under culture conditions

The digestive enzyme activities of Pacific bluefin tuna Thunnus orientalis were evaluated for specific activity and characterized for pH and temperature optima in crude extracts of stomach, caecal mass, and proximal, middle and distal intestine. A higher level of alkaline proteolytic activity was detected in the caecal mass than in the proximal intestine. Total alkaline proteases, trypsin, chymotrypsin and leucine aminopeptidase (LAP) were tested. The temperature and pH analyses showed that proteolytic activity as well as lipase were maximal in the alkaline range, with a maximum at pH 9.0 and at temperatures between 35 and 60°C, except for the pepsin, which showed maximum activity at the same temperatures but in the acid range (pH 3.0). The α-amylase activity showed a broader range in activity, both for pH and temperature, with higher activity over the alkaline pH values and higher temperature. The lipase activity seems to be nondependent on bile salts under our assay conditions, resulting in a significant activity reduction in the presence of bile salts. This knowledge will allow the development of a gastrointestinal model (everted intestine) where food or feed will be hydrolysed with the fish’s own enzymes, a project that is being undertaken in our laboratory as a contribution to the development of novel diets for tuna fish.     

Digestive enzyme activity during larval development of the Senegal sole (Solea senegalensis)

The activities of the main digestive enzymes (proteases, amylase, lipase) as well as those of acid and alkaline phosphatases were assessed during the larval development of the Senegal sole, Solea senegalensis. Important variations in specific activities of all the enzymes were observed during the period of study and were mostly related to the beginning or the end of metamorphosis. Both acid and alkaline protease activities were identified at early stages of development. Acid proteases accounted for only 10% of total protease activity in a 9 days-old larva, but exceeded 75% in a 33 days-old individual. Maximum lipase activity was related to the development of exocrine pancreas (days 6 to 10) and to metamorphosis. It is suggested this can be related to the metabolism of lipid reserves taking place during this morphological change. Activity of alkaline phosphatase decreased from day 5 to day 20 but therafter revealed a sharp increase, possibly linked to the development of enterocytes. The pattern of development of the main digestive enzymes found in S. senegalensis is similar to that described in other flatfish species.     

Heat treatment affects protein quality and protease activity in decapsulated cysts of Artemia when used as starter food for larvae of African catfish Clarias gariepinus (Burchell)

Decapsulated cysts of Artemia subjected to different heat treatments (40, 60, 80 and 96 °C) were fed to African catfish Clarias gariepinus larvae. Heated cysts, untreated cysts and live Artemia nauplii as control constituted the experimental diets. Protein denaturation and solubility, total alkaline protease and specific trypsin activities in the cyst diets were evaluated. The growth of catfish larvae and the proteolytic activity of larval samples during development were also determined. Heat treatment of cysts increased protein denaturation and decreased protein solubility. The protease activity in the cyst diets decreased with higher heating temperatures. The growth of catfish larvae differed according to the diet; higher fish growth was achieved with nauplii and cysts heated at 40 °C. The digestive enzyme activity in larval samples remained similar in all dietary treatments during larval development. The quality of food protein and the way this protein is processed might be more important for successful larval growth than exogenous enzyme supply.     

不同发育时期月鳢消化酶活性的变化

对月鳢稚鱼、幼鱼和成鱼的主要消化酶活性及分布进行了研究,结果如下：①随着鱼体发育和生长,月鳢消化系统各器官组织的各种消化酶活性不断地增强,尤其是蛋白酶和脂肪酶活性的发育更为明显。②月鳢幼鱼蛋白酶活性以肠组织最大,肝胰脏次之,胃组织最小,且肠组织和肝胰脏中该酶活性显著高于胃组织;胰蛋白酶活性以肝胰脏最大,胃组织和肠组织均表现较小;淀粉酶活性和脂肪酶活性均以胃组织最大,且显著大于肠组织和肝胰脏。③月鳢成鱼蛋白酶活性以中肠粘膜组织和后肠粘膜组织最高,前肠粘膜和肝胰脏次之,胃粘膜最低;胰蛋白酶活性以中肠粘膜组织和前肠粘膜最高,胃粘膜组织次之,肝胰脏小于胃粘膜,后肠粘膜组织的胰蛋白酶活性最小;淀粉酶活性以后肠粘膜组织和中肠粘膜组织最大,肝胰脏次之,胃粘膜组织和前肠粘膜组织最小;脂肪酶活性以胃粘膜组织最大,其他器官组织该酶活性均表现较小。     

Growth and ontogenetic development of digestive functionality in black Amur bream (Megalobrama terminalis)

The function of digestive physiology during ontogenetic development is essential to ensure high survival and growth rates. In order to evaluate the digestive physiological capacity of the black Amur bream (Megalobrama terminalis), changes of morphology and digestive enzyme activity (trypsin, lipase, amylase, pepsin, leucine aminopeptidase and alkaline phosphatase) in larvae were examined from hatching to 40 days after hatching (DAH). Results indicated that fluctuation patterns differed between the total and specific activities of the digestive enzymes. The total activities of these six enzymes gradually increased throughout the fish growth. The specific activity of trypsin peaked at 5 DAH and then decreased dramatically, while it increased remarkably again from 8 to 10 DAH and remained stable level after 20 DAH. Pepsin activity was first examined in M. terminalis at 15 DAH and gradually elevated towards the end of the experiment. The specific activity of lipase displayed obvious peaks at 5 and 20 DAH. For the amylase, its specific activity reached plateau at 4 DAH, underwent sharp decrease, and remained stable after 20 DAH. In addition, we found that the specific activity of alkaline phosphatase raised significantly from hatching to 5 DAH, and tended to keep slight fluctuation after 15 DAH. From the above, we concluded that the specific activities of digestive enzymes in the larvae varied constantly from 3 to 20 DAH and turned relatively stable after 20 DAH. The present study provides effective information that is useful to improve the seedling cultivation and the technology for healthy breeding.     

Digestive enzyme activities of turbot (Scophthalmus maximus L.) during early developmental stages under culture condition

Digestive enzyme activities were analysed in turbot (Scophthalmus maximus) from hatching until 60?days after hatching (DAH). Trypsin sharply increased to the climax at 17 DAH and decreased until 31 DAH followed by a stable level thereafter. Amylase was determined at 4 DAH, reached the maximum value at 19 DAH and declined sharply to 39 DAH and remained at a low level thereafter, suggesting the carbohydrate component should remain at a low level in formulated diets. Pepsin was detected at 9 DAH and increased to 34 DAH and then remained at a stable level. The above results revealed pancreatic enzymes are no longer main enzymes for food digestion after the formation of functional stomach. Leucine-alanine peptidase (Leu-ala) and alkaline phosphatase (AP) and leucine aminopeptidase N (LAP) were found in newly hatched larvae. Both AP and LAP activities markedly increased to 23 DAH, decreased abruptly to 50 DAH and increased gradually to 60 DAH. Leu-ala reached the plateau from 23 to 39 DAH, followed by a decline to 46 DAH and an increase until 60 DAH. The brush border membrane (BBM)-bound enzyme activities increased from 30% at 31 DAH to 81% at 38 DAH of the total activities, indicating the maturation of intestinal tract.     

Ontogeny and distribution of alkaline and acid phosphatases in the digestive system of California halibut larvae (Paralichthys californicus)

Studies aimed to assess the digestive physiology of marine fish larvae under culture conditions are important to further understand the functional characteristics and digestive capacities of the developing larvae. Most studies to date concentrate on intestinal lumen digestion and little attention to the absorption process. Thus, the objectives of this study were to histochemically detect and quantify some of the enzymes responsible for absorption and intracellular digestion of nutrients in the anterior and posterior intestine of California halibut larvae. Alkaline and acid phosphatases were detected from the first days post-hatch (dph). Alkaline phosphatase maintained a high level of activity during the first 20 dph in both intestinal regions. Thereafter, a clear intestinal regionalization of the activity was observed with the highest levels occurring in the anterior intestine. Acid phosphatase activity gradually increased in both intestinal regions during development, and a regionalization of the activity was not observed until late in development, once the ocular migration began. Highest levels were observed in the anterior intestine at the end of metamorphosis concomitant with the stomach development. The results from this study show some morphological and physiological changes are occurring during larval development and a clear regionalization of the absorption process as the larvae develops. These ontological changes must be considered in the elaboration of diets according to the digestive capacity of the larvae.