FISHERY BULLETIN: VOL. 76, NO. 1 



heavy infestations. Massive amounts of this sub- 

 stance overlying gill cuticle could block normal 

 gas diffusion across gill surfaces. 



Fungi 



Our knowledge of fungal diseases of penaeid 

 shrimps is in a state similar to that of our know- 

 ledge of bacterial diseases. The only clear-cut case 

 of a fungal pathogen affecting large numbers of 

 penaeid shrimps in the United States was reported 

 by Cook (1971) and by Lightner and Fontaine 

 ( 1973). These authors described infections of white 

 shrimp larvae by a phycomycete, Lagenidium sp., 

 an estuarine fungus. The fungus infects the second 

 protozoal stage of white shrimp, and disappears by 

 the time the first mysis stage is reached. Figure 

 10a shows a heavily infected protozoea. According 

 to Lightner and Fontaine (1973), the major 

 pathogenic effect is almost complete tissue de- 

 struction and replacement by invasive fungal 

 mycelia (Figure 10a). Hyphae of the fungus are 

 branched, septate, with thin walls, and range from 

 8.0 to 1 1 /u,m in diameter. Under bright field micro- 

 scopy the hyphae were yellow-green and con- 

 tained round oil droplets (Lightner and Fontaine 

 1973). 



The lifecycle of Lagenidium sp. in penaeid 

 shrimps involves a sporulation phase. This begins 

 when a hyphal extension penetrates the cuticle of 

 the shrimp from within (Figure 10b). Following 

 formation of a vesicle in the apical region of the 

 extension, planonts (flagellated zoospores) are 

 formed in the vesicle. The whole extension be- 

 comes a discharge tube, releasing motile planonts 

 (8.7-12 /xm) which presumably infect other 

 shrimp. 



Lightner and Fontaine ( 1973) were able to infect 

 larval brown shrimp (protozoea I) with planonts 

 and hyphae on a large scale ( 2,000 larvae). Result- 

 ing mortality in the experimentally infected 

 shrimp was- 20%. Approximately 60 h were re- 

 quired for infections to become patent. The role of 

 this fungus in natural shrimp populations is not 

 known. In aquaculture the fungus could be a 

 definite limiting factor in the survival of shrimp 

 larvae. Brown shrimp larvae in commercial 

 hatcheries have been found to die of this disease 

 (Cook 1971). 



The only other report of natural fungal infection 

 in penaeid shrimps in the United States was that 

 of Johnson.*' He briefly described a Fusarium 

 species which infected the gills and antennal 

 scales of Penaeus duorarum. Less than 5% of 



shrimp studied were infected and the spread of the 

 fungal mycelium in the body of affected shrimp 

 was slow. 



Solangi and Lightner (1976) have described the 

 cellular inflammatory response ofPenaeus aztecus 

 and P. setiferus to experimental infections of 

 Fusarium sp. According to these authors, both 

 species of shrimps showed "complete resistance to 

 infection by the fungal spores when normal or 

 wounded shrimp were held in seawater containing 

 the spores or when spores were injected directly 

 into the shrimp in low concentrations." Cellular 

 "melanization" and encapsulation of the micro- 

 and macroconidia occurred in gill tissues of 

 penaeid shrimp. Only massive doses of 3.2 x 10^ 

 spores injected into brown shrimp resulted in 

 death of shrimp; this lethality was a result of 

 mechanical blockage, by spores, of the blood 

 sinuses of the shrimp's gills. Gills of affected 

 shrimp sometimes were blackened. 



Protozoa 



More than any other phylum, the Protozoa as 

 pathogens and parasites have had significant, 

 known effects on shellfish populations. Represen- 

 tatives of every class of Protozoa are found as sym- 

 bionts, commensals, parasites, or pathogens in 

 penaeid shrimps. Certain groups such as the Mi- 

 crosporida have a long history as pathogens of not 

 only penaeid shrimps, but arthropods in general. 

 Only recently, however, species of such groups as 

 the Ciliophora and the Sarcomastigophora have 

 been indicted as serious pathogens of decapod 

 Crustacea, including penaeid shrimps. 



Herein Protozoa associated with shrimps will be 

 classified according to the scheme of the Honig- 

 berg Committee in "A Revised Classification of the 

 Phylum Protozoa" (Honigberg et al. 1964). 

 Sprague and Couch (1971) published an annotated 

 list of protozoan parasites, hyperparasites, and 

 commensals of decapod Crustacea. This list in- 

 cludes most of the known species of Protozoa as- 

 sociated with penaeid shrimps. However, since its 

 publication, several undescribed species have 

 been found and will be included herein. 



Subphylum Sporozoa Leuckart 1879 

 This subphylum includes the gregarines and 



^Johnson, S. K. 1974. Fusarium sp. in laboratory-held pink 

 shrimp. Texas A&M Univ., Fish Disease Diagnostic Lab. Note 

 FDDL-51, 1 p. 



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