FISHERY BULLETIN: VOL 72. NO. 1 



the body surface), increased rapidly in numbers 

 for 2 to 4 h after death of the shrimp. They 

 were absent by 8 h postmortem. 



The cellular elements of the gills underwent 

 fairly rapid autolytic change. By 8-12 h scat- 

 tered pyknotic nuclei were present (Figure 6c). 

 By 24 h the cellular elements of the gills were 

 for the most part anucleate, with some portions 

 of the gills having only eosinophilic debris 

 within the lamellar cuticle (Figure 6d). By 

 48 h the thin cuticle of gill lamellae had begun 

 to deteriorate and hence the gill lamellae sec- 

 tioned transversely began to lose their typical 

 "dumbbell" appearance (Figure 6e). By 72 h 

 the gills were usually no longer demonstrable 

 histologically, but in one of four animals exam- 

 ined portions of the gills were still evident 

 (Figure 60- 



Nerve Tissue 



The nervous system of shrimp is composed of 

 a large ventral nerve cord and segmental gang- 

 lia from which smaller nerve branches originate 

 to innervate the tissues. At the anterior end of 

 the ventral nerve tract is the supraesophageal 

 ganglion, which anteriorly receives the large 

 optic nerve tracts. 



Neuron perikaryons in the ganglia (Figure 

 7a) underwent the most rapid autolytic change 

 of the various elements of shrimp nerve tissue. 

 After 2 to 4 h, these cells showed considerable 

 rounding, pyknotic or karyolytic nuclei, and a 

 change in cytoplasmic staining from highly 

 basophilic to a lesser basophilic to almost eosin- 

 ophilic (Figure 7b). By 8 h no trace of neuron 

 perikaryons was evident. 



The nerve tracts of the ventral nerve, its 

 branches, and the optic nerves autolyzed less 

 rapidly than did neuronal perikaryons. How- 

 ever, nerve cell processes (axons and dendrites) 

 within the nerve tract autolyzed more rapidly 

 than did the supportive neurolemmal and glial 

 cells, and were no longer demonstrable histo- 

 logically by 12 to 24 h (Figure 7c). The support- 

 ive glial cells of the nerve tracts persisted with- 

 out noticeable change to 8 to 12 h, but these 

 cells became anucleate or underwent autolysis 

 after 24 h, and their former presence was 

 represented only by debris and an occasional 

 pyknotic nucleus (Figure 7d). 



After 24 h postmortem, the basic structural 



arrangement of the nerve tract remained rec- 

 ognizable due to the persistence of neurolemmal 

 fibers (Figures 7d and 7e), which persisted to 

 72 h at the sites of the optic nerve and ventral 

 nerve tracts. 



Antennal Gland 



The antennal gland of crustaceans had been 

 demonstrated to be imi)ortant in ion regulation 

 (Robertson, 1959). The antennal or hemocoelic 

 excretory gland in shrimp is located in the 

 cephalothorax above the supraesophageal gang- 

 lion (Young, 1959). The gland is composed of a 

 collection of tubules and a bladder (Figures 8a 

 and 8b). By 4 h some sloughing of tubule epi- 

 thelium was evident (Figure 8b), but for the 

 most part the histologic appearance of the organ 

 remained normal. At 12 h, however, most of the 

 nuclei of the tubule epithelium were intensely 

 pyknotic (Figure 8c), and by 24 h the organ had 

 disappeared or had become difficult to recognize 

 (Figure 8d). No trace of the gland was found 

 after 48 h postmortem. 



Gonadal Tissue 



Since the animals used in this study were 

 immature juvenile shrimp, the gonads were 

 small, poorly differentiated and were located in 

 the cephalothorax lateral and slightly caudad to 

 the hepatopancreas. The terminal ampule of 

 male shrimp was poorly developed and in female 

 shrimp the ovarian lobe, which extends into 

 the abdomen in older shrimp, had not yet 

 develoj^ed. 



The rate of autolysis in the gonads of the 

 shrimp studied was rapid, due to their close 

 proximity to the hepatopancreas. Gonadal 

 tissue was not recognizable histologically after 

 4 to 8 h postmortem. 



DISCUSSION 



The rigorlike stiffening observed in this 

 study may represent true rigor mortis. Sparks 

 (1972) i)ostulated that rigor mortis or a similar 

 phenomenon may occur in some invertebrates 

 with well organized skeletal systems and as- 

 sociated skeletal muscles. He based his opinion 

 on the observation that many arthropods, which 

 are flaccid after somatic death, subsequently 



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