NORMAL POSTMORTEM CHANGES 

 IN THE BROWN SHRIMP, PENAEUS AZTECUS^ 



Donald V. Lightner- 



ABSTRACT 



A study was carried out to determine the normal rates and patterns of gross and histologic 

 postmortem changes in the brown shrimp (Penaeus aztecus Ives). Experimental shrimp 

 were held at 10°, 20°. or 30°C in water-saturated air or in seawater at a salinity of 30<yoo. 

 Observations were made at 0, 2, 4, 8, 12, 24, 48, and 72 h postmortem. 



The first change observed grossly was the onset of a rigorlike stiffening of the abdominal 

 musculature. This stiffening was noted at 2 h postmortem at 30°C, but disappeared by 12 h 

 postmortem. The condition appeared later and persisted longer at the lower temperatures. 



Histologically, the tubule epithelium of the hepatopancreas was the first tissue to show 

 autolytic change. The autolysis in the remaining tissues examined occurred in the following 

 order: foregut and midgut epithelium, heart, neurons and nerve fibers, antennal gland 

 epithelium, gill epithelium, epidermis, muscle, and lastly connective and cuticular tissue 

 elements. In all tissues the rate of autolysis was temperature-dependent. 



Shrimp from the Gulf of Mexico represent one 

 of the most valuable fishery products of the 

 United States. Their popularity as a food item 

 and for use as sportfishing bait in some coastal 

 areas has resulted in recent studies aimed at 

 developing methods of artificially culturing 

 these animals. Despite the enormous value of 

 shrimp as a seafood, little is known about their 

 histology and the rates and patterns of post- 

 mortem change. 



Postmortem biochemical changes in the 

 muscle of brown shrimp (Penaeus aztecus Ives) 

 were reported by Flick and Lovell (1972). They 

 reported that the compounds ATP, ADP, AMP, 

 IMP, and glycogen decreased with time post- 

 mortem, while inosine, hypoxanthene, and lac- 

 tic acid increased. The latter compounds were 

 suggested as being partly responsible for flavor 

 deterioration of ice-stored shrimp. Tissue pH 

 values increased from 7.4 to 8.2 after 10 days 

 in ice-stored shrimp (0°C), and, according to 

 these authors, even with advanced bacterial 

 spoilage, increases in pH are usually observed 

 in fish and shellfish. Shrimp tails remained 

 tender and soft during the entire storage period 

 of 10 days (at 0°C) and did not exhibit any of 



' Contribution No. 369, Gulf Coastal Fisheries Center, 

 Galveston Laboratory, National Marine Fisheries Service, 

 NOAA, Galveston, TX 77550. 



- Gulf Coastal Fisheries Center, Galveston Laboratory, 

 National Marine Fisheries Service, NOAA, Galveston, 

 TX 77550. 



Manuscript accepted July 1973. 

 FISHERY BULLETIN: VOL. 72, NO. 1. 



the characteristics commonly associated with 

 rigor mortis (Flick and Lovell, 1972). 



In the only histologic study of postmortem 

 change in an invertebrate animal. Sparks and 

 Pauley (1964) reported the normal postmortem 

 changes in the oyster, Crassostrea gigas. The 

 digestive tubules of the oyster underwent the 

 most rapid autolytic change in dead oysters 

 held at 14°-16°C, while the Leydig tissue, gut, 

 stomach, mantle, gill and palps autolyzed some- 

 what less rapidly. The gonads were the most 

 resistant of all oyster tissue to autolysis with 

 ova and sperm appearing relatively normal even 

 after all other tissues had undergone extensive 

 autolysis. 



There are certainly a number of factors which 

 influence the rate of autolysis in a dead animal. 

 Some of these factors include water tempera- 

 ture, dissolved oxygen concentration, pH, bac- 

 terial flora of the water and of the animal, and 

 the physiological condition of the animal at 

 the time of death. It has been demonstrated in 

 man and other animals that postmortem chang- 

 es occur in a regular and irreversible pattern 

 and at a relatively constant rate from one indi- 

 vidual to another when factors causing varia- 

 tion in the rate and pattern are considered 

 (Sparks and Pauley, 1964). Differentiation of 

 histological changes due to disease from those 

 due to postmortem autolysis or poor fixation 

 is possible once the normal rates and patterns 



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