MFR PAPER 1340

Comments on Trends in Researchon Parasitic Diseasesof Shellfish and Fish

Victor Sprague is with the Center forEnvironmental and EstuarineStudies, Chesapeake BiologicalLaboratory, University of Maryland,Solomons, MD 20688. This paper isContribution No. 797, Center for En­vironmental and Estuarine Studies ofthe University of Maryland, Sol­omons, MD 20688.

VICTOR SPRAGUE

This subject is arbitrarily limited inscope to the protozoa and in time to thepast decade. It deals very briefly withrecent developments in the biology andsystematics of some protozoan groupsthat are significant as pathogens. Moredetailed reviews have recently beenpublished by Couch (1978), Hazardand Oldacre (1976), Sindermann(1970), Sprague (1970a, b, 1971,(977), and Sprague and Couch (197 I).The symposium edited by Snieszko( (970) contains numerous articles per­tinent to "fish health," the two bySprague being specifically cited aboveas being particularly relevant to thispresentation.

RECENT ADVANCES

Amoebae

In Crabs

Only one amoeba is believed to be aserious mortality factor in shellfish.This parasite, Paramoeba perniciosaSprague, Beckett, and Sawyer, 1969,was first reported and briefly describedin 1966 by Sprague and Beckett whofound it in the hemolymph of dead andmoribund crabs, CaLlinectes sapidus,in Chincoteague Bay, Maryland andVirginia. These authors did not recog­nize the parasite as an amoeba at thattime, but in a later note (Sprague andBeckett, 1968) assigned it to genusParamoeba Schaudinn, 1896.

The parasite occurs in thehemolymph of heavily infected crabs.Sometimes the body fluid of the hostbecame mil ky white due to the presence

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of enormous numbers of the parasites.As the number of parasites increases,the hemocytes decrease in number.Heavy infections may be accompaniedby lysis of the skeletal muscles.

Paramoeha perniciosa has been lim­ited to the higher salinity waters. It hasbeen found most frequently in"peeler" crabs suffering heavy mor­talities in holding tanks, but has beenfound also in "hard" crabs collected inenzootic areas. Lunz (1968) found itassociated with crab mortalities alongthe coast of South Carolina and Geor­gia. Sawyer (1968) gave preliminarydata on the epizootiology and host­parasite relations. Newman and Ward( 1973) reported a modest epizootic inChincoteague Bay. Sawyer (1968)found the parasite in the blood onlyduring mortalities, which occurredmainly in the spring. He postulated acryptic tissue phase in the parasite's lifecycle during other parts of the year.Very recently, Johnson (1977) discov­ered the' 'cryptic phase" in the connec­tive tissues. She found that the parasiteis present in these tissues at all seasonsof the year and invades the circulatingblood in the vessels only when the dis­ease is terminal. Johnson also trans­mitted the infection by inoculation,with fatal results to the inoculatedcrabs.

The evidence that this amoeba is avery significant mortality factor in Cal­linectes sapidus is overwhelming, iflargely circumstantial. The parasite hasnot been grown in pure culture, and itsnormal mode of transmission is un­known.

In Fish

Only very recently, amoebae havebecome generally recognized as impor­tant mortality factors in fish. Someamoebae pathogenic to man also occurin fish.

Disease conditions of epizooticproportions in rainbow trout on com­mercial trout farms of Italy and otherEuropean countries have been attrib­uted by Ghittino et al. (1977) to anamoeba. Epizootics associated with thesame amoeba were reported by Fergu­son and McC Adair (1977) in Scotlandand Ireland. It seems clear from thesereports that an amoeba (apparently notyet identified) is a very important factorin widespread mortalities of trout inEuropean fish farms.

Taylor ( 1977) isolated amoebae fromII species of fish in the southeasternstates. Among those isolated wasAcanthamoeba polyphaga whichTaylor regarded as the cause of a largekill, involving mainly blue tilapia, inFlorida. This study has special interestbecause A. polyphaga is pathogenic toman.

Sawyer et at. (1974) describedThecamoeba hoffmani from the gills offingerling rainbow trout, coho salmon,and chinook salmon. They concludedthat the species is essentially a free­living form, although it seems to be acontributory factor in mortalities.

Microsporidia

In Bivalve Mollusks

Microsporidium sp. has been found,but not yet reported, by Brian Jones' inthe visceral mass of Ostrea lutaria inNew Zealand. This is the third species'known in bivalve mollusks. Thesespecies are not significant pathogens.

'Jones, B., Zoology Department. Victoria Uni­versity, Wellington, N.Z.

Marine Fisheries Review

Figure 1.-Amesol1 pulvis (Perez, 1905), spores, in muscle of green crab.

In Crabs

Microsporidia are common patho­gens of crabs and shrimp, mainly in theskeletal muscle. About a dozen speciesare now known in crabs, four of them inthe muscles of the blue crab, Cal­/inectes sapidus Rathbun. Three of thelatter are rare, but one. Nosemamichaelis Sprague, 1970a, is common,widely distributed, and lethal to itshost; the impact on the host populationhas not been assessed. Nosemamichaelis, being readily obtainable ingreat quantity, has become a useful ob­ject for studies on cytology of the para­site (Sprague et aJ. 1968; Weidner,1970, 1976; Weidner and Trager,1973) and on intracellular parasitism(Trager, 1974). This species was re­cently made the type of a new genus,now beingAmeson michaelis (Sprague,1970) Sprague, 1977. One of the fourspecies known in Callinectes,The/ohania sp. Johnson, /972, is unde­scribed. The first two species of micro­sporidia reported in crabs, The/ohaniamaenadis Perez, 1904, and Nosema pu/­vis Perez, 1905, both in the green crabCarcinus maenas (L.), were recentlyrediscovered, the first by Sprague andVivares independently and the secondby Vivares. Vivares (1975) has alreadypublished on the former, while Vivaresand Sprague (in press) have redescribed

October /978

the latter, now Ameson pu/vis (Perez,1905) Sprague, 1977 (Fig. I).

In Shrimp

Nosema ne/soni recently becameAmeson ne/soni (Sprague, 1950)Sprague, 1977. This species, originallyfound in the muscles of Penaeus az­tents Ives, has now been identified insix species of penaeid shrimp.Thelohania macrocystis, in muscles ofPalaemonetes varians, recently be­came Chapmanium macrocystis (Gur­ley, 1893) Hazard and Oldacre, 1976.Thelohania penaei, in ovary Penaeussetiferus (L.), recently became Agma­soma penaei (Sprague, 1950) Hazardand Oldacre, 1976.

Quite recently, a relatively largenumber of new species have been dis­covered in shrimp. A new genus andnew species, Inodosporus spragueiOverstreet and Weidner, 1974, wasfound in Pa/ael11onetes pugio Holthiusand P. kadiakensis. P/eistophora lin­toni Street and Sprague, 1974 was de­scribed in Pa/aemonetes pugio. Severalundescribed species were found in pan­daJid shrimp sent to me from BritishColumbia by T. H. Butler. One ofthese, The/ohania sp. Vernick,Sprague. and Krause, 1977, in Pan­da/us jore/ani Rathbun, has been de­scribed by Johnston, Vernick, and

Sprague (in press) as a new species(Fig. 2). Pleistophora penaei Con­stransitch. 1970 was found in commer­cial shrimp. Pleistophora crangoniBreed and Olson, 1977 was found infour species of Crangon. Some unde­scribed species have been listed bySprague ( 1977).

In Fish

Microsporidia are very common infish; over 100 species of fish are nowknown to be parasitized. Some micro­sporidia are also known to be seriousmortality factors in fish. Delisle, 1972found massive mortalities of smelt, as­sociated with this parasite, in certainCanadian lakes. G/ugea stephani(l-Iagenmuller, 1899) has been foundby different investigators to be an im­portant mortality factor in youngflatfish of different species. Spragueand Vernick (1968) found thatIchthyosporidium giganteul11 (Thelo­han, 1895), long treated as haplospo­ridium, is a microsporidium. This (ora very similar species) is not uncom­mon in .. spot," Leiostol11us xanthurusLacepede, in tributaries of the Chesa­peake Bay. It produces a very largeabdominal swelling, usually in youngfish, that probably kills the host.

Haplosporidia

There has been much interest in hap­losporidia during the past decade,mai nly because they are very destruc­ti ve pathogens of oysters. This has ledto the discovery of a few new species,much better understanding of thegroup, and new ideas on classification.

In Biva/ve Mollusks

Perkins (1968, 1969) and Rosenfieldet aJ. (1969) have contributed much toour understanding of haplosporidia bymaking the first electron microscopestudies on some typical forms-thosefamiliar species in Crassostrea vir­ginica (Gmel in).

Minchinia arl110ricana van Banning,1977, was found in the European flatoyster, Ostrea edulis. This is the onlyknown haplosporidian that has tails onits spores like those seen in the typespecies M. chitonis (Lankester, 1885).Sprague (1970c) suggested that pres­ence or absence of these tails be used as

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Figure 2.-The/ohania sp. Vernick et al., 1976, various sporulation stages,in muscle of the shrimp Panda/us jordani. Bouin, section, Heidenhain;1,300 x.

the basis for distinguishing MinchiniaLabbe, 1896 from HaplosporidiumCaullery and Mesnil, 1899.

Two species of a previously unfamil­iar kind have been found in associationwith oyster mortalities. They areMarteilia refringens Grizel et al., 1974(type species), in the European flat oys­ter Ostrea edulis L., and M. sydneyiPerkins and Wolf, 1976, in the Austra­lian oyster, Crassostrea commercialis.Perkins (1976a) suggested that they arerelated to the haplosporidia, mainly be­cause they have "haplosporosomes."

/n Decapods

"Minchinia sp." Marchand, 1974,was found in the mud crab, Rhithro­panopeus harrisii, in France. Plas­modia of a haplosporidian were foundby Newman et al. (1976) in Callinectessapidus from Virginia and NorthCarolina.

Myxosporidia

New species are frequently added tothe long list of myxosporidian speciesin fish. Most are not noted forpathogenicity, but one highly patho­genic form, Myxosoma eerebralis(Hofer, 1903), has been the object ofmany recent studies. An interestingspecies recently described is Unieap­sula pflug/elderi Schubert, Sprague,and Reinboth, 1975. It has spores withtwo rudimentary polar capsules, as wellas the fully formed one that is charac­teristic of the genus. Another species,interesting because it infects an impor­tant sport fish, is Henneguya sp.Meyers, Sawyer, and MacLean, 1977,in the heart of the bluefish, Pomatomussaltatrix (L.).

Protista Incertae Sedis

An unidentified parasite with vagueresemblance to the Coccidia was re­cently found by Peter Wolf (1977) inova of the blacklipped oyster, Cras­sostrea echinata, from Australia.Another unidentified protist was foundin the digestive epithelium of the pearloyster, Pinctada maxima, in Australia(Wolf and Sprague, 1978).

A parasite in spleen and liver of rain­bow trout, causing epizootic disease inEngland, was recently sent to me by

28

John Finlay 2 for identification. I noted aresemblance to intracellular stages ofHexamita but, being unable to makepositi ve identification, sent the sl ides toGlenn Hoffman. At first, Hoffman 3

suspected the parasite might be identi­cal with the amoebae reported by Ghit­tino et al. (1977), but after further con­sideration, he doubted that it is anamoeba. The identity of the parasiteremains undetermined.

CLASSIFICAnON

Some minor changes in classifica­tion, particularly the transfer of somemicrosporidian species to new genera,have already been mentioned. One ofthe most spectacular of the minor de­velopments in recent years was thefinding by Perkins (1976b) that theflagellated zoospore of Dermocys­tidium marinum Mackin, Owen, andCollier, 1950 has an apical complex.This led Perkins to conclude that theparasite, long regarded as a fungus, isrelated to the Coccidia.

'Finlay, J., Fish Diseases Laboratory, Ministryof Agriculture, Fisheries and Food, The Nothe,Weymouth, Dorset. England DT4 8UB.3 Hoffman, G. A., Fish Farming Experimental Sta·tion. U.S. Fish and Wildlife Service, SIUllgart,AR 72160. Pers. commun.

Drastic changes are taking place inthe classification of the highercategories of protozoa, since recent ad­vances in knowledge indicate that theold phylum Protozoa is an artificial as­semblage of several phyla. A . 'Com­mittee on Classification and Nomencla­ture" of the Society of Protozoologists,headed by N. D. Levine, is making arevision. Microsporidia, haplo­sporidia, myxosporidia, and someother groups will probably becomedistinct phyla, as ciliates have alreadydone. Classification of microsporidiaprobably will be based on that ofSprague (1977). Classification of hap­losporidia will probably include amajor new taxon to include Marteilia.Myxosporidia are now considered bymany protozoologists to be metazoawith coelenterate affinities, but theywill probably remain for awhile in thesystem of the protista.

This is a convenient occasion to takespecific action upon my previous(Sprague, 1970c) suggestion and trans­fer from genus Minchinia Labbe, 1896to Hap/osporidium Caullery and Mes­nil, 1899 species which, like the typespecies H. sea/opli Caullery and Mes­nil, 1899, have spores without tails.Accord ingly, Minchinia louisianaSprague, 1963b becomes Haplo-

Marine Fisheries Review

sporidium louisiana (Sprague. 1963b)comb. n. and M. nelsoni Haskin.Stauber. and Mackin 1966 becomes H.nelsoni (Haskin et al.. 1966) comb. n.Other species which Sprague (1963a:265-266) transferred (for reasons laterfound to be invalid) from Haplo­sporidium to Minchinia are now re­turned to Haplosporidium.

LITERATURE CITED

Breed, G. 1'1., and R. E. Olson. 1977. Biology ofthe microsporidan parasite Pleislophora eran­goni n. sp. in three species of crangonid sandshrimps. J. lnvertebr. PathoI. 30:387-405.

Constransitch, M. J. 1970. Description, pathol­ogy, and incidence of Pleislophora penaei n.sp. (Microsporidia: Nosematidae), a parasiteof commercial shrimp. M.S. Thesis, North­western State Univ., Natchitoches, La.• 35 p.

Couch, J. A. 1978. Diseases, parasites, and toxicresponses of commercial penaeid shrimps ofthe Gulf of Mexico and South Atlantic coasts ofNorth America. Fish. Bull., U.S. 76: 1-44.

Delisle, C. E. 1972. Variations mensuelles deGlugea herlll'igi (Sporozoa: Microsporida)chez differents tissus et organes de I'eperlanadulte dulcicole et consequences de celie infec­tion sur une mortalite massive annuelle de cepoisson. Can. J. Zool. 50:1589-1600.

Ferguson, H. w. ,and B. McC Adair. 1977. Pro­tozoa associated with proliferative kidney dis­ease in rainbow trout (Salmo gairdneri). Vet.Rec. /00:/58-159.

Ghittino, P., S. Andruello, and E. Vigliani.1977. L'amebiasi della trota iridea d'al­levamento. Riv. Ital. Piscic. Ittiopat. 12:74­89.

Grizel. H., M. Comps, J. R. Bonami, F. Cousse­rans, J. L. Duthoit. and M. A.le Pennec. 1974.Recherche sur I'agent de la maladie de laglande digestive de Ostrea edulis Linne. Sci.Peche 240:7-30.

Haskin, H. H.. L. A. Stauber, and J. A. Mackin.1966. Minchinia nelsoni n. sp. (Haplosporida,Haplosporidiidae): causative agent of the Del­aware Bay oyster epizootic. Science (Wash.,D.C.) 153:1414-1416.

Hazard. E.I., and S. W. Oldacre. 1976. Revisionof Microsporida (Protozoa) close toThelohania. with descriptions of one new fam­ily, eight new genera, and thirteen newspecies. U.S. Dep. Agric., Agric. Res. Serv.,Tech. Bull. 15.\0. 104 p.

Johnson, C. A., III. 1972. A preliminary reporton diseases of North Carolina coastal crabswith emphasis on the blue crab, Cal/inectessapidus. ASB (Assoc. Southeast. BioI.) Bull.19:77.

Johnson, P. T. 1977. Paramoebiasis in the bluecrab. Cal/ineues sapidus. J. Invertebr. Pathol.29:308-320.

Johnston, L. B., S. H. Vernick, and V. Sprague.In press. Light and electron microscope studyof a new species of Thelohania (Microsporida)in the shrimp Pandalus jordani. J. Invertebr.PathoI.

Lunz, G. R. 1968. In Hearings before the Sub­committee on Fisheries and Wildlife Conserva-

October /978

tion of the Committee on Merchant Marine andFisheries-House of Represenlatives. Com­mer. Fish. Res. Legisl. H. R. 18008. Ser. No.90-29, p. 99-104. U.S. Gov. Print. Ofr ..Wash .. D.C.

Marchand. J. 1974. Presence de Minchiniu sp.(Haplosporida - Haplosporidiidae) chez Iexanthide Rhilhrop(//lOpeu.\· harrisii (Gould)fridenlalUS (Maitland) dan Ie canal de Caen ala mer. Rev. Trav. Insl. Peches Marit.38:209-213.

Meyers. T. R.• T. K. Sawyer. and S. A. Mac­Lean. 1977. Hennegu)'u sp. (Cnidospora:Myxosporida) parasitic in the heart of thebluefish. PomalOmus salTatrix. J. Parasitol.63:890-896.

Newman. M. W., C. A. Johnson. III. and G. B.Pauley. 1976. A Minchinia-like haplosporidanparasitizing blue crabs. Callinecfes sapidus. J.lnvertebr. Pathol. 27:311-315.

____, and G. E. Ward. Jr. 1973. Anepizootic of blue crabs, Callineues sapidus,caused by Paramoeba perniciosa. J. Invertebr.PathoI. 22:329-334.

Overstreet, R. 1'1., and E. Weidner. 1974. Dif­ferentiation of microsporidian spore-tails inInodosporus spraguei gen. et sp. n. Z.Parasitenkd. 44: 169-186.

Perkins. F. O. 1968. Fine structure of the oysterpathogen Minchinia nelsoni (Haplosporida,Haplosporidiidae). J. Invertebr. Pathol.10:287-307.

1969. Electron microscope studiesof sporulation in the oyster pathogen, Min­chinia COSIO/is (Sporozoa: Haplosporida). J.Parasitol. 55:897-920.

1976a. Ultrastructure of sporulationin the European flat oyster pathogen, Marteiliarefringens-taxonomic implications. 1. Pro­tozool. 23:64-74.

1976b. Zoospores of the oysterpathogen. Dermocysridium marinum. I. Finestructure of the conoid and other sporozoan­like organelles. J. Parasitol. 62:959-974.

____, and P. H. Wolf. 1976. Fine struc­ture of Marleilia sydneyi sp. n.-haplospori­dan pathogen of Australian oysters. J.Parasitol. 62:528-538.

Rosenfield. A.• L. Buchanan, and G. B. Chap­man. 1969. Comparison of the fine structure ofspores of three species of Minchinia (Hap­losporida, Haplosporidiidae). J. Parasitol.55:921-941.

Sawyer. T. K. 1968. Preliminary study on theepizootiology and host-parasite relationship ofParamoeba sp. in the blue crab, Callineclessopielus. Proc. Natl. Shellfish. Assoc. 59:60­64.

____,J. G. Hnath, andJ. F. Conrad. 1974.Thecamoeba hoJJmaIIi sp. n. (Amoebida:Thecamoebidae) from gills of fingerling sal­monid fish. J. Parnsitol. 60:677-682.

Schubert, G .. V. Sprague. and R. Reinboth.1975. Observations on a new species of Ulli­capsula (Myxosporida) in the fish Maenasmaris (L.) by conventional and electronmi­croscopy. I.. Parasitenkd. 46:245-252.

Sindermann. C. J. 1970. Principal diseases ofmarine fish and shellfish. Academic Press,Lond., .169 p.

Snieszko. S. F. (editor). 1970. A symposium ondiseases of fishes and shellfishes. Am. Fish.Soc. Spec. Publ. 5.526 p.

Sprague. V. 196.1a. Rcvision of genus Huplo­sporidium and rc:storation of genus Millchi"ia(Haplosporidia. Haplosporidiidae). 1. Proto­zool. 10:263-266

____. 196.1b. Millchilli" louisialla n. sp.(Haplosporidia. Haplosporidiidac). a parasiteof Pallopeus herbslii. J. Protozool. 10:267­274.

____. /970a. Some protozoan parasitesand hyperparasites in marine decapod Crus­tacea. In S. F. Snkszko (editOr). A symposiumon diseases of fishes and shellfishes. p. 416­4.10. Am. Fish. Soc. Spec. Publ. 5.

1970b. Some protozoan parasitcsand hyperparasites in marine bivalve molluscs.In S. F. Snieszko (editor). A symp<lsiulll ondiseases of fishes and shell Ii shes. p. 511-526.Am. Fish. Soc. Spec. Publ. 5.

1970c. Recent problems oftaxonomy and morphol<lgy of Haplosporidia.(Abstr. 602) J. Parasitol. 56(4, Sec. II. Part1):327-328.

____. 197 I. Diseases of oysters. Annu.Rev. Microbiol. 25:21 1-230.

1977. Systematics of the Micro­sporidia. III L. A. Bulla. Jr. and T. C. Cheng(editors), Comparative pathobiology. Vol. 2.510 p.

____. and R. L. Becken. 1966. A diseaseof blue crabs (Callillecles sapidus) in Mary­land and Virginia. J. Invertebr. Pat hoI.8:287-289.

____.and .1968. ThenalUreofthe etiological agent of' 'gray crab" disease. J.Invertebr. PathoI. II :503.

____, and T. K. Sawyer.1969. A new species of Paramoeba(Amoebida, Paramoebidae) parasitic in thecrab Callinectes supid/ls. J. Invertebr. PathoI.14:167-174.

- , and J. Couch. 1971. An annotatedlist of protozoan parasites. hyperparasites. andcommensals of decapod Crustacea. J. Pro­tozool. 18:526-537.

____, and S. H. Vernick. 1968. Observa­tions on the spores of Pleistophora gigallfea(Thelohan. 1895) Swellengrebel. 1911. a mi­crosporidan parasite of th-e fish Crenilabrusmelops. J. Protozool. 15:662-665.

____, , and B. J. Lloyd. Jr.1968. The fine structure of Nosema sp.Sprague, 1965 (Microsporida. Nosematidae)with particular reference to stages insporogony. J. Invertebr. PathoI. 12: 105· I 17.

Street, D. A., and V. Sprague. 1974. A newspecies of Pleislophora (Microsporida: Pleis­tophoridae) parasitic in the shrimp Palaemo­lIeles pugio. J. Invertebr. Pathol. 23: 153-156.

Taylor, P. W. 1977. Isolation and experimentalinfection of free-living amebae in freshwaterfishes. J. ParasilOl. 63:232-237.

Trager, W. 1974. Some aspects of intracellularparasitism. Science (Wash., D.C.) 183:269­273.

Van Banning, P. 1977. Minehinia annoricanasp. nov. (Haplosporida), a parasite of theEuropean flat oyster. OSlrea "dulis. J. Inver­lebr. Pathol. 30: 199-206.

Vernick, S. H., V. Sprague, and D. Krause.1977. Some ultrastructural and functional as­pects of the Gnlgi apparatus of Thelollllnia sp.(Microsporida) in the shrimp PW/llalllsjordaniRathbun. J. Protozool. 24:':>4-99.

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MFR Paper 1340 From Marine Fisheries Review. Vol. 40, No. 10. October1978. Copies of this paper, in limited numbers, are available from 0822, UserServices Branch. Environmental Science Information Center, NOAA, Rockville.MO 20852 Copies of Marine Fisheries Review are available from the Superin­tendent of Documents, U.S. Government Printing Office, Washington, DC20402 for $1. 10 each.

Susceptibility Studies of VariousSalmonids to Whirling Disease:Histological Staining and SporeConcentration Procedures

Vivares, C. P. 1975. Elude comparative faile enmicroscopies photonique et electronique de troisespeces de microspiridies appartenant au genreThelohallia Henneguy. 1892, parasites de crus­taces decapodes marins. Ann. Sci. Nal. Zool.BioI. Anim. Ser. 12,17:141-178.

____, and V. Sprague. In press. The finestructure of Amesoll pu/vis (Perez. 1905) (Mi­crospora, Microsporida) and its implication re­garding classification and chromosome cycle.J. Invenebr. PathoI.

Weidner, E. 1970. Ultrastructural study of mi­crosporidian developmenl. J. Nosema sp.Sprague. 1965 in Callillectessl1pidus Rathbun.Z. lellforsch. Mikrosk. Anal. 104:33-54.

MFR PAPER 1341

JOSEPH O'GRODNICK

Since 1968, research on the trans­mission, life history, and control ofwhirling disease in trout has been con­ducted by the Pennsylvania Fish Com­mission. Whirling disease is caused bya myxosporidian parasite, Myxosomacerebralis, which invades and destroyscartilage of susceptible salmonidspecies. The parasite was introducedinto the United States from Europe andhas been established as a persistenthatchery disease in several areas.

Affected fish exhibit rapid, tail chas­ing behavior from the disintegration ofthe cartilaginous support skeleton of theorgans of equilibrium. Also, severecrippling may result from destruction of

Joseph O'Grodnick is with the Ben­ner Spring Fish Research Station,Pennsylvania Fish Commission, Bel­lefonte, PA 16823.

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1976. Interaction of microsporidiawilh host cells. Proc. 1st Inl. Colloq. Inver­tebr. Pathol. and IXth Annu. Meel. Soc. Inver·lebr. Palhol., p. 82-84.

____, and W. Trager. 1973. Adenosinetriphosphate in the extracellular sun'ival of anintracellular parasite (Nosema michaelis, Mi·crosporidial. J. Cell BioI. 57:586-591.

the spinal skeleton if fish are exposed asfry. "Blacktail," which is caused bypressure on the nerves that control thecaudal pigment cells, may be seen insome fish.

In this research, two methods wereused to monitor the development of thewhirling disease parasite in varioussalmonid species: I) examination ofhistological sections, and 2) quantita­tive estimates of spores determined bythe use of the plankton centrifuge pro­cedure (Fig. I). (This method involveshomogenization of head skeletons,screening out tissue shreds, andconcentrating with a continuous plank­ton centrifuge.

The life cycle of Myxosoma cere­bralis was monitored in rainbow trout(highly susceptible species) and browntrout (highly resistant species) by theexamination of histological sections.Tissues were prepared from infected

Wolf, P. H. 1977. An unidentified protistan para­site in the ova of th~ bla~klipp~d oyster. Cras­wstr('u e('hil/uw. fmm n()rth~rn Australia. J.In\'ert~br. Pat hoI. 29:244-246.

_____. and V. Sprague. 1978. An uniden·tilicd protistan parasite of th~ p~arl oyster,Pillcwda maxima. in tropical Australia. J. In­vertebr. PathoI. 31 :262-263.

Figure I.-The plankton centrifuge. Thecentrifuge removes water through the cen­trifugal force created by the revolvingdrum. The excess water is carried awaythrough a rubber tube situated below thedrum. Solid particles are deposited on thewall of the revolving drum.

fi sh at gi ven intervals, averaging 3 daysfrom initial exposure to the develop­ment of spores at 120 days. The follow­ing staining methods were used in thestudy: I) Hematoxylin and Eosin, 2)Mallory Heidenhain (Casson­Modification), 3) Wright's stain, and 4)Ziehl-Neelson (acid fast staining forspores) .

Marine Fisheries Review