How Does Enzyme Activity Change When Crab Larvae Grow?

In order to develop a proper diet, it is necessary to\r\nunderstand the activity of protein hydrolytic enzyme through the stages of developing\r\ncrab larvae.

Sea crabs (Scylla paramamosain) are important\r\ncultured species in our country. With the characteristics of fast growth,\r\nhigh nutritional value, crab is a food with export value and a large\r\nconsumption market, effectively from the crab farming models that have been\r\nbringing stable income to the region. At the seaside.

In order to provide farmers with good quality crab stocks\r\nand to reduce the pressure on wild-caught species, crab production is\r\nincreasingly concerned and developed. However, the survival rate in\r\nartificial seed production is still low, usually from 5-7%. With current\r\ntechnology, the larvae mortality rate in metamorphic stages is still high,\r\nculminating in the Zoae (Z1-Z3) and from Zoae-5 (Z5) to Megalopa stages, which\r\nis a big challenge for larval rearing process. In addition to disease\r\ncaused by Vibrio, the low survival rate in mud crab seed production has been\r\nattributed to inadequate seed production technology due to lack of knowledge\r\nabout larval development and digestive physiology.

Importance of feed\r\nhydrolytic enzymes in crustaceans

Crustaceans often lack enzymes necessary for hydrolysis of\r\nfood. A number of studies have shown the importance of fresh food as the\r\nfirst food for fish larvae and mollusks, using enzymes in food to improve\r\ndigestion until the digestive system becomes complete development.

In order to successfully develop crab crab breeding\r\ntechnology, knowledge of the development of digestive enzymes is essential in\r\nthe nutritional physiology and development of appropriate feed and feeding\r\nregimes necessary to meet meet the nutritional needs of crab\r\nlarvae. However, studies on digestive enzyme characteristics of Scylla\r\nparamamosain crab larvae are very limited.

This study describes the characteristics of some protein\r\nhydrolyzate enzymes (trypsin, chymotrypsin, pepsin, protease) as a basis for\r\nthe formulation of reasonable diets in larval rearing, contributing to improved\r\nsurvival rates. of sea crab larvae.

Protein hydrolytic\r\nactivity changes as crab larvae develop

Healthy larvae were collected and treated by formol 200 ppm\r\nfor 30 seconds before being placed in 3 nursery tanks, volume of 0.5m 3 ,\r\nsalinity 30 ‰, nursing density of 400 larvae / liter. 

Crab larvae were fed with Artemia 6 times daily. The\r\ntank has a bottom siphone and changes water every 3 days, each time changing\r\n25% of the water. 

Check and maintain alkaline content at 100 - 120ppm\r\nNaHCO 3 . When the larvae were completely transferred to Zoae-4,\r\nthey were collected and transferred to the 2m 3 composite tank ,\r\narranged at a density of about 50-70 larvae / liter. When the larvae moved\r\nto Megalope, proceed to place plastic mesh baskets for the larvae to cling and\r\nlimit eating. 

The activity of protease, trypsin, chymotrypsin and pepsin\r\nwas analyzed during larval development from Zoae-1 to Crab-1. The results\r\nshowed that during the larval development stage, the activity of the protein\r\nhydrolytic enzyme of sea crabs had a large variation in each stage, in which\r\nthe activity of protease and pepsin enzymes increased gradually (from 3.85 to\r\n19.1 U / mg protein and 1.69 to 8.32 U / mg protein) in all larval stages,\r\nwhile trypsin and chymotrypsin activity from Zoae-1 to Zoae-5 is very low (0.92\r\n- 0.99 and 1.15 -0.85 U / mg protein), there are major changes in the stages of\r\nZoae-5, Megalope and Crab.

In the Zoae-1 to Zoae-5 stage shows low activity of protein\r\nhydrolytic enzymes, to the Zoae-5, megalope stage, the enzyme activity is\r\nrelatively complete, to the Megalope stage and to the metamorphosis to crab,\r\nEnzymes have a big change in finishing activity according to changes in\r\nmorphology and feeding behavior of crabs.

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These results indicate changes in the activity of protein\r\nhydrolytic enzymes during the development of mud crab larvae, from which to\r\nselect suitable food sources in the nursery process to suit each development\r\nstage. , contributing to raising the survival rate in the nursery process.

Source: Tepbac