Digestive enzyme activities in carnivores and herbivores: comparisons among four closely related prickleback fishes (Teleostei: Stichaeidae) from a California rocky intertidal habitat

Three digestive enzymes in four species of closely related prickleback fishes (family Stichaeidae: Cebidichthys violaceus, Xiphister mucosus , Xiphister atropurpureus and Anoplarchus purpurescens ) were analysed to assess whether diet or phylogeny played a larger role in influencing digestive enzyme activity. Cebidichthys violaceus and X. mucosus are primarily herbivorous, whereas X. atropurpureus and A. purpurescens are mainly carnivorous. The two Xiphister species are sister taxa, and A. purpurescens is in a clade adjacent to that of the three other species. Pepsin and trypsin specific activities did not differ significantly among the four species, but α‐amylase activity was significantly higher in the two Xiphister species, followed by C. violaceus , and then A. purpurescens . The wide disparity between the two carnivores, the striking similarity between the two sister taxa, and the significant difference between the two herbivores indicate that activity of α‐amylase follows a pattern influenced more by phylogeny than by diet in these fishes.     

Morphological changes during metamorphosis in cod (Gadus morhua L.), with particular reference to the development of the stomach and pyloric caeca

Metamorphosis in cod, Gadus morhua L., was investigated with respect to morphological changes in the alimentary tract (mouth, stomach and pyloric caeca) and external characters (finfold and fin development). Morphometric measurements and histological investigations were made on both larvae and juveniles and all fish lengths are given as standard length. Median unpaired fins started to develop when the fish were 9–10 mm in length. The larval median finfold was resorbed when fish reached a size of 11–15 mm. The vertebrae were formed in fish of 11–20 mm. The supraterminal mouth, seen in larvae <12 mm, changed gradually to a sub-terminal position in juveniles larger than 65 mm. The development of the stomach and pyloric caeca started at 15 mm and the juvenile form was seen in fish of 40 mm. The ability to store and grind food particles in the stomach developed gradually as fish increased in size from 20 to 40 mm. Compared to many other teleost species, cod juveniles are relatively large when the stomach and pyloric caeca become fully developed. These findings may have important implications for both start-feeding of cod larvae and the weaning of juveniles on to artificial diets.     

Phenotypic flexibility of digestive system in Atlantic cod (Gadus morhua)

This study examined the restoration of the digestive capacity of Atlantic cod (Gadus morhua Linnaeus) following a long period of food deprivation. Fifty cod (48 cm, 1 kg) were food-deprived for 68 days and then fed in excess with capelin (Mallotus villosus Müller) on alternate days. Ten fish were sampled after 0, 2, 6, 14 and 28 days and the mass of the pyloric caeca, intestine and carcass determined. Two metabolic enzymes (cytochrome c oxidase and citrate synthase) were assayed in white muscle, pyloric caeca and intestine, and trypsin activity was measured in the pyloric caeca. A delay of 14 days was required before body mass started to increase markedly, whereas most of the increase in mass of both the pyloric caeca and intestine relative to fish length occurred earlier in the experiment. By day 14, the activities of trypsin and citrate synthase in the pyloric caeca as well as citrate synthase in the intestine had reached maxima. The growth of the digestive tissues and restoration of their metabolic capacities thus occur early upon refeeding and are likely required for recovery growth to take place. The phenotypic flexibility of the cod digestive system is therefore remarkable: increases in trypsin activity and size of pyloric caeca resulted in a combined 29-fold increase in digestive capacity of the fish during the refeeding period. Our study suggests that Atlantic cod are able to cope with marked fluctuations in food availability in their environment by making a rapid adjustment of their digestive capacity as soon as food availability increases.     

饥饿和再投喂对虎斑乌贼幼体存活、生长和消化酶活力的影响

本文探究了饥饿胁迫与饥饿后再投喂对虎斑乌贼幼体存活率、生长、行为、肝体比、摄食率以及消化酶活力的影响.在室内控制条件下开展了幼体(初始体质量为4.95±0.48 g)的饥饿(0、1、2、3、4、5、6 d)和再投喂(15 d)试验.结果表明: 不同饥饿时间对虎斑乌贼的幼体存活率、体质量降低率、肝体比和消化酶活力影响显著.随着饥饿胁迫时间的增加,其存活率、肝体比呈下降趋势,其中饥饿3 d后,存活率开始明显下降,体质量降低率明显增大,幼体出现喷墨、互相残杀等异常行为;4种消化酶活力呈先下降后上升的趋势,淀粉酶活力以饥饿4 d组最低 (0.07±0.02 U·mg^-1·prot^-1);脂肪酶活力以饥饿2 d组最低(18.47±2.07 U·g^-1·prot^-1),饥饿6 d组最高(57.60±3.98 U·g^-1·prot^-1),胃蛋白酶活力和胰蛋白酶活力以饥饿5 d组(1.98±0.59 U·mg^-1·prot^-1)和饥饿4 d(186.68±20.72 U·mg^-1·prot^-1) 最低.饥饿处理结束后,经15 d再投喂,各试验组存活率、特定生长率、肝体比和摄食率差异显著,幼体的存活率、特定生长率、肝体比和摄食率均与饥饿处理时间呈负相关;饥饿1和2 d组与对照组的存活率、特定生长率和肝肝体比无显著差异,而饥饿3～6 d组显著低于对照组;饥饿1～2 d组的摄食率明显高于对照组,而饥饿6 d组的摄食率明显小于对照组;各组淀粉酶与脂肪酶活力无显著差异,胃蛋白酶与胰蛋白酶活力差异显著,均以对照组最高(胃蛋白酶活力7.06±0.64 U·mg^-1·prot^-1,胰蛋白酶活力914.67±26.54 U·mg^-1·prot^-1),饥饿6 d组最低(胃蛋白酶活力3.21±0.57 U·mg^-1·prot^-1,胰蛋白酶活力660.04±37.92 U·mg^-1·prot^-1).说明虎斑乌贼的幼体饥饿不可逆点(PNR)为第6天,且不能补偿生长.     

Mechanisms of digestion in the marine herbivore, the luderick, Girella tricuspidata (Quoy and Gaimard)

The effect of feeding frequency on the mechanisms of digestion in the mucosa and contents of the gastrointestinal tract of the luderick, Girella tricuspidata (Quoy and Gaimard), was determined. Use was made of the variation in utilization frequency of Enteromorpha intestinalis by C. tricuspidata fed according to two different regimes to determine the importance of these digestive mechanisms in algal digestion.
The contents of the oesophagus and stomach of fish fed ad libitum were consistently acidic whilst those from fish deprived of food were highly variable and more alkaline. The contents of the pyloric caeca. intestine and rectum were slightly alkaline in both groups.
The number of microorganisms found in the digestive tract increased with a reduction in food availability. There was no significant cellulase activity in any of the animals tested.
Amylase and lipase were found in the pyloric caeca, intestine and rectum, but were not present in the oesophagus or stomach. Lipase activities were highly variable. Although some protease was found in the posterior portion of the gut, the majority of the activity occurred in the oesophagus and stomach.
Generally, amylase, lipase, and protease activities were unaffected by a change in the feeding regime of the fish from being fed ud libitum to being fed for a period of 24 h every 5 days. It is concluded that a reduced activity of enzymes that hydrolyse algal cell contents is not the reason for the lower utilization efficiency of food-deprived fish.
It is clear that the only difference in digestive mechanisms between fish fed ad libitum and fish fed infrequently is the variation in pH of the foregut. It is considered likely that the increased acidity of the foregut of animals fed ad Iibilum facilitates hydrolysis of the algal cell walls and allows greater utilization of algae by these fish.     

红螯螯虾胚胎发育期主要消化酶和同工酶的活性变化

采用生物化学方法测定了红螯螯虾(Cherax quadricarinatus)胚胎发育各期主要消化酶(胃蛋白酶、胰蛋白酶、淀粉酶、纤维素酶和脂肪酶)的比活力及主要同工酶(乳酸脱氢酶、苹果酸脱氢酶、葡萄糖-6-磷酸脱氢酶和酯酶)的活力。结果显示,5种消化酶各自表现出不同的变化模式,胃蛋白酶和胰蛋白酶的比活力早期均逐渐上升,到发育后期胃蛋白酶出现快速下降,而胰蛋白酶却仍保持较高水平;淀粉酶比活力呈“V”字型变化趋势,晚期活性较高;纤维素酶和脂肪酶的比活力则均较低。4种同工酶酶谱随胚胎的发育渐趋复杂,酶活性也随之增强。结果表明,消化酶和同工酶活力的高低均受其基因的调控,并随胚胎发育适时表达,为胚胎组织、器官和系统的形成以及未来仔虾的开口摄食提供物质保证。     

Biochemical characterization,cloning and molecular modeling of a digestive lipase from red seabream (Pagrus major): Structural explanation of the interaction deficiency with colipase and lipidic interface

Red seabream digestive lipase (RsDL) was purified from fresh pyloric caeca. Pure RsDL has an apparent molecular mass of 50 kDa. The RsDL is more active on short‐chain triacylglycerols (TC₄), and enzymatic activity decreases when medium (TC₈) or long‐chain (olive oil) triacylglycerols were used as substrates. The specific activities of RsDL are very weak as compared to those obtained with classical pancreatic lipases. No colipase was detected in the red seabream pyloric caeca. Furthermore, the RsDL was not activated by a mammal colipase. Similar results were reported for annular seabream lipase. In order to explain structurally the discrepancies between sparidae and mammal lipases, genes encoding mature RsDL and five other lipases from sparidae fish species were cloned and sequenced. Phylogenetic studies indicated the closest homology of sparidae lipases to bird pancreatic ones. Structural models were built for annular seabream and RsDL under their closed and open forms using mammal pancreatic lipases as templates. Several differences were noticed when analyzing the amino acids corresponding to those involved in HPL binding to colipase. This is likely to prevent interaction between the fish lipase and the mammalian colipase and may explain the fact that mammalian colipase is not effective in activating sparidae lipases. In addition, several hydrophobic residues, playing a key role in anchoring pancreatic lipase onto the lipid interface, are replaced by polar residues in fish lipases. This might explain the reason why the latter enzymes display weak activity levels when compared to mammalian pancreatic lipases.     

Gut morphology and function in Atherinops affinis (Teleostei: Atherinopsidae), a stomachless omnivore feeding on macroalgae

The marine silverside Atherinops affinis has a short, simple gut and no obvious stomach or physical mechanisms for breaking down algal cells even though its diet in many estuarine habitats is primarily green macroalgae. Silverside from the Upper Newport Bay estuary in southern California had: (1) assimilation efficiencies from a green algal diet of 54% (total organic material), 74% (carbon), 84% (nitrogen), 89% (protein) and 81% (energy), values typical for marine herbivorous fishes; (2) an alkaline gut and no pepsin activity, thus confirming that the fish lacks a stomach; (3) relatively high amylase activity and low trypsin and lipase activities, a digestive enzyme profile expected in a fish consuming a high-carbohydrate, low-protein and low-lipid diet. The fish appears to be capable of functional herbivory and can be classified tentatively as a type III herbivore based on its possible use of pharyngeal jaws for lysis of algal cells.     

Profile of Digestive Enzymes Activity During Early Development of Featherback <Emphasis Type="Italic">Chitala chitala</Emphasis> (Hamilton, 1822)

The ontogenetic development of the key digestive enzymes of featherback Chitala chitala was assayed during the early development. Amylase, lipase, trypsin and chymotrypsin activities were detected on 1 days after hatch (DAH), (during endotrophic stage) but pepsin activity was detected on 12 DAH (exotrophic phase) correlated with the improvement of gastric secretion at the beginning of flexion stage. The gradual shift of alkaline protease activity (trypsin and chymotrypsin) to more efficient acidic digestion indicated a change in the digestive physiology as a result of metamorphosis acquiring the juvenile characteristic during the postflexion or extrophic phase. The initial high level of amylase (i.e. from 1 DAH to 9 DAH) during endotrophic and endoexotrophic feeding stage could be better explained as a result of programmed gene expression. But a constant decrease in activity after the 12 DAH i.e. on the onset of flexion and exotrophic stage of featherback fish in the present study may be possibly due to the developmental changes in the gut morphology and increased protein level in the tissue. These fluctuations of the enzymatic activities in featherback larvae reflect the ability of the fish to adapt with the diet during ontogenetic shift. This information can lead to the possibility of developing an age specific formulated feed for intensive farming of this new candidate species.     

Evidence and properties of digestive proteases in young mugilidae during the first year of life]

Proteolytic activity was observed in extracts from the digestive tract of Mugil auratus and Mugil capito; its maximum occurs at about pH 2 and 9. Activity in the acid range is mainly found in stomach extracts and the enzyme may be considered as similar to pepsin and cathepsins. In the alkaline range, the main activity is recorded in the region of the pyloric caeca. Activities of the trypsin, chymotrypsin, A and B carboxypeptidases and elastase type are found. The effects of pH and temperature on some activities are studied: optimal pH are about 2.6 and 3,4 with pepsin-like activity, between 8,1 and 8,5 with trypsin-like activity and between 7,8 and 8,5 with chymotrypsin-like activity; incubation optimal temperature (pH 2,2) is found between 35 degrees and 40 degrees.     

Gut size in GH‐transgenic coho salmon is enhanced by both the GHtransgene and increased food intake

Growth hormone transgenic coho salmon Oncorhynchus kisutch fed at the same ration level as non‐transgenic controls (Tc) had the same growth rate as non‐transgenic controls (Nt). In contrast, growth hormone transgenic coho salmon (Tf) fed ad libitum ate about twice as much and had much higher growth rates than the other two groups. The most obvious result was the significantly larger caeca in the Tf group relative to both Nt or pair‐fed Tc. The Tf fish had more caeca that were longer. The results suggested that the effect was indirect and the enlarged caeca required both the GHtransgene and hyperphagia to cause enlarged caecal capacity. A small part of the results, however, also suggested that there was a direct effect of the GHtransgene on some gut tissues, particularly the intestine.     

Size‐dependent microhabitat use and intraspecific competition in Cottus gobio

An electrofishing survey of daytime shelter microhabitat use of bullhead Cottus gobio in a southern English chalk stream revealed positive selection for moderate water velocity, vegetation cover and coarse substrata. Water depth, other forms of cover, shade and substratum embeddedness had no significant influence on the distribution of fish. Microhabitat use was size‐dependent, with patches occupied by adult fish containing coarser substrata and less blanket weed ( Cladophora algae) than those occupied by smaller juvenile conspecifics. Differences in substratum use between size‐classes were less pronounced in parts of the stream shaded by the tree canopy. In laboratory tanks stocked at low fish density, both juveniles and adults favoured use of cobbles over pebbles. The response of fish to increased conspecific density was size‐dependent; juveniles reduced use of the coarse substratum whereas adults maintained their predominance in this habitat. An apparently greater shift by juveniles when in the presence of adults was significant at α = 0·10 only, as was an apparent reduction in interactions between size‐classes under low light intensity. The displacement of small juvenile fish from the preferred cobble substratum is consistent with the hypothesis that intraspecific competition contributes to the size‐related microhabitat shift observed in the field. Although there was a tendency for the strength of competition to be reduced at low light levels, the mechanism by which tree canopy cover affects microhabitat use remains uncertain.     

Various lipases for producing products enriched with polyenic acids in fish fat hydrolysis]

The enzymic hydrolysis of fish with lipases from various sources was studied. The lipase from the fungus Rhizopus microsporus preferentially removes saturated fatty acids, while lipase from the pyloric caeca of salmon unsaturated fatty acids upon hydrolysis of fish fats. The enzymes can be used to obtain fatty products enriched with eicosanopentaenoic acid, mono- and diacylglycerols by enzymic hydrolysis of the ivasi fat.     

卤虫投喂下长吻(鱼危)仔稚鱼消化酶发育和口宽变化的研究

采用酶学和形态学测定方法, 研究在投喂卤虫条件下长吻(鱼危)仔鱼4种主要消化酶: 胃蛋白酶、胰蛋白酶、脂肪酶和淀粉酶的活性变化以及长吻(鱼危)仔鱼口宽、全长变化。实验共进行13d, 实验结果表明: (1)长吻(鱼危)仔鱼全长、口宽的发育与其日龄表现出明显的线性正相关(R_TL²=0.974, R_MW²=0.964)。口宽与全长比值(MW/TL)在仔鱼开口后急剧下降, 并自7日龄开始维持在0.07—0.08, 口宽和全长处于同步发育期并表现出明显的相关性(R²=0.948), 说明7日龄(/h, days post hatching)后口宽和全长处于同步发育期, 标志仔鱼转食的开始。(2)长吻(鱼危)仔鱼初次开口时即可检测出四种消化酶的活性。5—7/h时胰蛋白酶显著高于初孵仔鱼, 与此时仔鱼开始开口摄食的行为相一致。胃蛋白酶、脂肪酶活性在仔鱼孵化后第7天即开口的第3天, 淀粉酶活性在孵化后第6天, 显著高于初次孵化出来的仔鱼。8—13/h时, 胃蛋白酶、胰蛋白酶、脂肪酶和淀粉酶活性均在较高水平平稳的波动, 标志着消化道发育逐渐健全。     

Carbohydrases in the digestive tract of the African bony-tongue Heterotis niloticus (Pisces: Osteoglossidae)

The presence of amylase and maltase in the stomach, intestine and pyloric caeca of Heterotis niloticus is demonstrated. Amylase activity was highest in the fore-gut, followed by the pyloric caeca, while the lowest activity was in the hind-gut. Optimum pH for intestinal amylase was 8.45. Sucrase, lactase and cellulase were not detected.     

Estimation of protein digestibility—IV. Digestive proteinases from the pyloric caeca of coho salmon (Oncorhynchus kisutch) fed diets containing soybean meal

The goal of this study was to better understand why dietary soybean products are poorly utilized by salmonids. The influence of dietary intake on coho salmon fingerling weight gain and specific properties of pyloric caeca enzymes was investigated. Fingerlings were fed diets containing heated or unheated soybean meal (SBM) or Promoveal™, as 15–25% herring meal replacer, for 8–12 weeks. Fish fed to apparent satiation with diets containing heated SBM replacer gained more weight than those fed unheated SBM at the same level. Fish increased in body weight at the same rate when fed restricted rations containing either 15% SBM replacer that was variously heated up to 20 min, 15% Promoveal™ replacer or the herring meal basal diet. After the experimental diets were fed, digestive proteinases were isolated from the pyloric caeca. Yield of pyloric caeca enzymes (PCE), recovery of trypsin in PCE, soybean trypsin inhibitor (SBTI) sensitivity of PCE trypsin, specific activity of PCE trypsin and in vitro casein digestibility by PCE were determined for each dietary group. Weight gain vs in vitro casein digestibility by PCE was linear for animals fed unheated SBM to apparent satiation (r² = 0.71, P < 0.1) but not for animals fed either heated SBM to apparent satiation or variously heated SBM as 15% replacer at restricted levels. Trypsin from fish fed diets with heated or unheated SBM, but not Promoveal™ replacer, was less sensitive to SBTI than fish fed no SBM. For fish fed diets with variously heated SBM as 15% replacer, the SBTI activity of the SBM and SBTI inhibition of PCE trypsin were inversely related (r² = 0.88, P < 0.05). The yield of PCE was higher for fish fed 25% of heated SBM replacer than it was for diet groups fed less SBM. The yield of PCE trypsin was higher from animals fed 25% heated SBM replacer than those fed diets with a lower percentage of heated SBM replacer. Feeding coho fingerlings rations with SBM replacer appears to promote physiological compensation of PCE. Heat stable and/or heat-activated factor(s) and SBTI appear to cause the compensation of salmon digestive proteinases from coho salmon fed diets with SBM.     

Ultrastructural and biochemical aspects of digestion in the imagoes of the flyRhynchosciara americana

The midgut of adultRhynchosciara americana Wiedemann (Diptera: Sciaridae) displays, in contrast to the midguts of other adult Diptera, two caeca connected to a ventriculus. All midgut cells exhibit long apical microvilli, and narrow and ramified basal channels with openings to the underlying space. These morphological features are thought to be involved in the absorption of nutrients from food. Enzymatic assays inR. americana adults revealed that amylase occurs in salivary glands and midgut, whereas aminopeptidase, α-glucosidases and trypsin occur only in the midgut, mainly in the ventriculus. There is a soluble (Mr 105000) and a membrane-bound aminopeptidase (solubilized form, Mr 110000). Soluble α-glucosidase inactivates easily and could not be characterized, whereas membrane-bound α-glucosidases were resolved after solubilization into three molecular species (Mr 186000, 105000 and 84000) with different substrate specificities. The activities of trypsin (pH optimum 9.0), which was inhibited completely by soybean trypsin inhibitor, and of amylase (pH optimum 5.5), were not sufficiently high to be further characterized. The data support the assertion thatR. americana adults are able, to a limited extent, to digest and absorb starch and proteins, in addition to nectar sugars. The results, supported by published data, suggest that there is an inverse correlation between the digestive enzyme activities and midgut absorptive surface in insects which has nectar as a major food.     

The effects of various diets on chitinase and ß-glucosidase activities and the condition of cod, Gadus morhua (L.)

Groups of cod, Gadus morhua (L.), were fed exclusively on fish, crustaceans, or crustacean shells for a period of 3 weeks. Chitinase and ß-glucosidase activities were measured in enzyme extracts of stomach contents, stomach tissue, pyloric caeca, intestinal contents, and intestine tissue, and compared to the enzyme activities of control fish starved over the same period. Fulton's condition factor K , liver lipid content and liver water content were determined to estimate the effects of the diets on the condition of cod.
general, the highest chitinase activities were measured in samples of cod that had been fed on whole crustaceans. In this feeding group, there was also a remarkable increase of activity by a factor of four to eight in the pyloric caeca, compared to the group fed on fish and the control group, respectively.
Measurements of ß-glucosidase activity revealed no similar dependence on food quality, ß-glucosidase occurrence seemed to be mainly restricted to the pyloric caeca and the intestine of cod.     

pH值对中国龙虾消化酶活力的影响

采用酶学分析方法研究了pH对中国龙虾胃蛋白酶、类胰蛋白酶、淀粉酶、纤维素酶和脂肪酶活力的影响。结果表明,在设定的pH范围内,中国龙虾各消化酶的活力均随着pH的升高呈现先升后降的变化趋势。其中,胃、肠、肝胰腺内胃蛋白酶最适pH均为2.2,类胰蛋白酶最适pH分别为8.8-9.2、8.4、8.8,淀粉酶最适pH分别为7.0、7.0、7.4,纤维素酶最适pH分别为4.2、4.2-4.6、5.4,脂肪酶最适pH分别为7.2-7.6、7.2、6.8-7.2。同时测得中国龙虾胃、肠、肝胰腺内的生理pH分别为5.33、6.93、6.60。中国龙虾的消化酶活力存在器官特异性。在最适pH下,胃蛋白酶活力顺序为胃>肠>肝胰腺,类胰蛋白酶、纤维素酶、脂肪酶的活力顺序均为肝胰腺>肠>胃,淀粉酶的活力顺序为肠>肝胰腺>胃。