Effects Of Starvation On Biochemical Composition And Digestive System Histology In Juvenile Pampus Argenteus

Fish species are usually subjected to a natural starvation due to periodic shortage of foodduring life history and have therefore. Facing starvation stress, fish are able to make aphysiological adaptive adjustment by consuminge their own organization material, however, theirdigestive systems would inevitably suffer damage. Therefore, to study the effects of starvation onbody composition and digestive system histology would be helpful to know the countermeasure ofphysiology and ecology of fish to adaopt theo starvation in physiology and ecology and, revealfish metabolic characteristics and resistance to stavation, and which would provide theoreticalguidance for aquaculture practices.Pampus argenteus is Perciformes, Stromateidae, Pampus, a cluster fish in the middle andlower of warm water layer. It is one of China’s major marine economy species which distributes ina broader range. In the past, studies of Pampus argenteus mainly consist of the classification,resource assessment, ecology and reproductive characteristics, artificial reproduction, nutrientanalysis and other aspects. However, few studies focus on the effect of starvation on morphologicaland physiological of Pampus argenteus.In our study, the average of initial weight of young Pampus argenteus was （2.61±1.05）g andthe date lasted from Jun2010to Sep2011. The differences of external morphology, internal organstructure, morphology and histology of the digestive system of young Pampus argenteus instarvation stress were are studied. What’s more, we analyzedThe the digestive enzyme activitiesand body composition changes before and after starvation are analyzed. Focusing on the uniquestructure of digestive system of young Pampus argenteus, a comprehensive and systematicanalysis of the physiological changes in their structures and biochemical composition wasanalyzed presented from macro to micro. We are aimed to reveal their metabolic andphysiological responses when they adapted to starvation stress. We hope that our study would beuseful for accumulating the basic information for in-depth studying the histochemical, digestivephysiology, immunology of Pampus argenteus digestive system. The results were summarized asfollows:（1） Researches showed that the body weight and fatness of Pampus argenteus understarvation stress decreased significantly（P<0.05）. After5and9days under starvation, their bodyweight decreased22.36%and42.25%, fatness decreased15.94%and31.08%, respectively. Excessive feeding caused a significant increase in most morphological characters. However, thechange in liver weight was not significant （P>0.05）. The body length-weight relationship undernormal and5d starvation group were: Wc=0.0307L^2.9931, WS5=0.0216L^2.9658, respectively.（2） By analyzing relationships between the body weigh, fatness of died juvenilesfromhunger and their body length, we found that fatness declining rate increased with theincreasing of body length. The fatness of lethal juvenile with the body length of2.2cm-5.2cmdecreased with the increase of body length, it was75%⁵9%of formal fish.（3） By systematically anatomizing the digestive organs of juvenile Pampus argenteus,we found that its mouth was small, its teeth was underdeveloped, and it had the esophagealsac which was the unique structure of pomfret. On the muscle wall, it had many mastoidswhich contained lots of sub-mastoid. There were horny spines embedded within the skinpuncture. Furthermore, its stomach possessed a shape of U and was not developed. There were60⁸0pyloric caecums around the stomach pylorus. In addition, Pampus argenteus had a longintestine （relative length value2.68, which is bigger than the general carnivorous fish） with four tosix curves, by which it can be divided into three portions, namely, foregut, midgut and hindgut.The liver was composed by left and right one, while the volume of the left one was three times ofthe right one.Suffering starvation stress, liver had been significant changed firstly, which volume decreasedand color became darker. Subsequently, the intestine became thin andintestine wall becamethinner with a losing of flexibility. Pyloric caecum atrophied, which was not easily separated.At the last, the size of esophageal sac decreased, the wall of esophageal sac became thinnerand mastoid was shorter.（4） The digestive system structure of Pampus argenteus was observed by the histologytechnology. We found that the muscular layer of esophageal sac was well developed, while themastoid and sub-mastoid on the muscular wall were covered by sub-mucous layer. The hornyspine was embedded within the sub-mastoid. The epithelium of stomach was composed ofsingle columnar cell, while there were many gastric glands in the lamina propria. In intestinal, itwas distributed with developed villus, the villus of foregut presented a dendritic shape, while thebranch of which in midgut reduced, and it would be finger-like in hindgut. The structure offoregut was similar to pyloric caeca. Liver was made up by hepatic lobule. Liver cells, whichcontain a large number of fat particles, were mostly with a shape of regular polygon.Suffering starvation stress, liver presented a significant change firstly. Liver cell atrophyedand tissue became to loosen. Then, the muscular layer became thinner, and the villus of foregutand midgut would be shorter, which is more obvious than hindgut. The muscle thick of caecadecreased, the muscle fibers loosed, and villous height reduced. At the last, esophageal sac changed with mastoid was thinner and shorter, the layer of mucosa and sub mucosa wasthinner, and horny spines became apparent gradually.（5） The surface of esophageal sac was observed with scanning electron microscope.Ultrastructure observation showed that esophageal sac mastoid and secondary processessurface are composed by epithelium cells, meanwhile, many tiny crests which created densefingerprint-like loops were observed on cell surfaces. After starvation, mastoid squamousepithelium cells were shrunken and damaged, and tiny crests were not obvious. Horny spineemerged on the top of secondary processes. The exfoliated cell fragments were founddistributing in the basal of horny spine. There were many mitochondria, which weresurrounded by rough endoplasmic reticulum, in the hepatocyte. Hepatocyte sinusoidscontained red blood cells and Kupffer cells. The inside of disse was occluded by manymicrovilli extended from hepatocytes. The bile cannaliculi was formed by sinking ofplasmalemma of several adjacent cells. After suffering starvation, the gap between cellsincreased, the surface of nuclear membrane became unsmooth, nucleolus disappeared, thenuclear mass scattered, the total number of cell organelles decreased, and mitochondriaswelled and exhibited many kinds of shapes.（6） The results showed that stomach and intestines of Pampus argenteus are the mainorgans to digest and absorpt protein, and the content of protease in stomach and intestines wassignificantly higher than that in lateral sac and liver. During starvation, the activity of pepsinfirstly decreased and then increased, while the activity of trypsin declined in all digestiveorgans. At the same time, the activity of amylase in the liver and lateral sac increased, however,it presented a contrary trend in stomach and intestins. Besides, the activity of lipase in theliver, the lateral sac, stomach and intestines exhibited downtrend basically with the increasingtime of starvation.（7） Pampus argenteus were treated with a starvation for continuous9dates in experiment,the results showed that the change of loss of crude protein of fish was more gently duringstarvation, and the biggest loss rate of crude protein appeared in5d⁷d which was up to5.57%.The loss rate of crude protein of which dropped to12.32%compared with that incontrol group. What’s more, the loss of fat in pre-starvation was greater than the post-starvation, and the peak of the loss rate of fat presented in3d⁵d which was up to59.98%,while the loss rate of fat of which dropped to83.99%in the ninth day. The non-nitrogen-freeextract decreased rapidly in post-starvation.（8） A comprehensive analysis of the studies of morphologic and histological of digestivesystem, digestive enzymesand body composition of Pampus argenteus, it showed that the contentof fat in larvae of Pampus argenteus was low and couldn’t provide a successive energy during the starvation period. In pre-starvation, Pampus argenteus mainly consumed the fat stored inthe liver with a supplement of using the protein. Next, in medium period of starvation, thespeed of consuming protein increased and it mainly consumed protein in muscle and digestivetissue to maintain its body activities. Lastly, in post-starvation, it began to use carbohydrates.Above all, those were the strategies of using energy to adapt to hunger and physiologicalmechanisms of starvation resistance in the larvae of Pampus argenteus.