COUCH: DISEASES AND PARASITES OF PENAEID SHRIMPS 



Protargol silver protein. It is the first flagellate 

 reported to be associated with shrimp mortalities. 

 The flagellate occurred in the hemocoel, abdomen, 

 and all appendages of protozoel and mysid stages 

 of brown shrimp during April 1974 (Figure 27). 

 The flagellate was found in 649f of larvae 

 examined from the mortality; living, moribund, 

 and dead larvae were infected (Tables 1, 2). 



The flagellates were variable in form ranging 

 from 7.8 to 11.7 ^im with an average diameter of 

 9.4 yLtm. A compact nucleus (2 or 3 /um) containing 

 a large endosome was situated medianly. The 

 cytoplasm ranged from clear to opaque and often 

 contained various inclusions. In life, the flagellate 

 was slightly pyriform with a terminal, single 

 flagellum (Figure 29). Specimens stained with 

 protargol clearly demonstrated a flagellar base, 

 parabasal body, or blepharoplast (karyomastig- 

 ont) (Figures 26, 29). A possible cyst stage (7-9 /u.m) 



was observed in advanced or heavy infections in 

 the hemocoel (Figures 28, 29f). Dividing stages, 

 observed occasionally, contained nuclei undergo- 

 ing division without loss of nuclear membranes 

 (Figures 29e). 



The role, if any, that Leptomonas sp. plays in the 

 mortality of shrimp larvae is unknown. Other 

 than mechanical damage, there appears to be lit- 

 tle evidence of a pathogenic mechanism for the 

 flagellate. It is possible that the flagellate is a 

 secondary invader of a weakened host, possibly 

 from encysted forms which may exist in the 

 hindgut of the host. 



Platyhelminthes 



Flatworms have been described as parasites of 

 all commercial species of penaeid shrimps in the 

 United States. These include digenetic trematodes 





Figure 29. — a. Leptomonas sp. drawn from life with flagellum. b, c, d. Forms of the flagellate (possibly amastigote 

 stages) as they appear in Protargol-stained body (hemolymph) of brown shrimp, e. Cell division in flagellate showing 

 karyokinesis and longitudinal cytoplasmic fission, f. Possible cyst stage Lep/omonas from hemocoel of larval shrimp. 

 Note Protargol-positive kinetoplast near nucleus (arrow points to kinetoplast). (All figures x2,900.) 



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