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VIMS Articles Virginia Institute of Marine Science

1997

Evidence That Qpx (Quahog Parasite Unknown) Is Not Present In Hatchery-Produced Hard Seed

Susan E. Ford

Roxanna Smolowitz

Lisa M. Ragone Calvo Virginia Institute of Marine Science

RD Barber

John N. Kraueter

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Recommended Citation Ford, Susan E.; Smolowitz, Roxanna; Ragone Calvo, Lisa M.; Barber, RD; and Kraueter, John N., "Evidence That Qpx (Quahog Parasite Unknown) Is Not Present In Hatchery-Produced Hard Clam Seed" (1997). VIMS Articles. 531. https://scholarworks.wm.edu/vimsarticles/531

This Article is brought to you for free and open access by the Virginia Institute of Marine Science at W&M ScholarWorks. It has been accepted for inclusion in VIMS Articles by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. Jo11r11al of Researrh. Vol. 16. o. 2. 519-52 1, 1997.

EVIDENCE THAT QPX (QUAHOG PARASITE UNKNOWN) IS NOT PRESENT IN HATCHERY-PRODUCED HARD CLAM SEED

SUSAN E. FORD,' ROX ANNA SlVIOLOWITZ,2 LISA 1\1. RAGONE CA LV0,3 ROBERT D. BARB ER,1 AND JOHN N. KRAlJETER1 1 Haskin Shellfish Research Laborarory lnsri1ure .for Marine and Coastal Sciences and Ne11· Jersey Agricultural Experi111e11r Sra1io11 R111gers University Por1 Norris, Ne111 Jersey 08345 2Labora101)' for Aquatic Anilnal Medicine and Pathology U11il'ersiry o,f Pennsyh·ania Marine Biological Laborarory \¥oods Hole. Massachuseus 02543 3School of· Marine Science Virginia lnstirute of Marine Science College o,f Willian1 and J\.1ary Gloucester Point, Virginia 23062

A.BSTRA.CT A protistan parasite known as QPX (Quahog Parasite Unknown) has been recently associated with disease and monaJity of adult hard . mercenaria. from to Virginia. There is concern thar the organism may be transponed in hatchery-reared seed. Tissue sections of 2,203 seed clams (< 1-20 mm ) from 13 different hatcherie, in six states. collected from 1995 to I 997 and examined by parhologists in three laboratories. fai led to show QPX or QPX-like organisms. Further. QPX was not detected in a total of 756 hatchery-produced clams exam111ed during their first year of field growout. From this , we conclude that hatchery­ produced seed clams are an unlikely source of QPX organisms.

KEY WORDS: hard clam eed. /vferce11aria merce11aria. QPX. quahog. disease. parasice, hatchery

TNTR0 DUCTI 0N thulid. Labyri111huloides ha/iotidis (Bov1er 1987a). Subsequent in­ vestigations (Bo\ver 1987b) sho\ved that L. halio1idis could be A protistan parasite has been recently associated with disease cransrnirted directly from to abalone by a flagellated zoo­ and mortality of wild and cu lni.red hard clams, Mercenaria 111er­ spore stage of the parasite. ce11aria (Linnaeus. J 758). fron1 Canada to Virginia (Whyte et al. Hard clam culturists along the East Coast of the Un ited States 1994. Ragone Calvo et al. 1997, Smolowitz and Leavitt 1997. rely entirely on seed clan1s produced in hatcheries. \vhich often Smolowitz et a l. in press). The pa rasite was first described in clams ship seed to gro\vers in distant regioos of the coast. The findi ng of from the St. Lawrence River, Canada, in the late 1950s and early QPX-like organisn, s in cultured adult clams. combined with the l 960s (Drinnan and Henderson 1963). It was subsequently found possibility that they can be transmitted directly bet,veen clan,s, as in j uveni le and ad ult clams in a hatchery on Prince Ed~1ard Island. is the case with L. halioridis. has led to concen1 that the parasite Canada, and at that time was given the acrony1n " QPX" for might have been introduced via hatchery-produced seed and might Quahog Parasite Unknown (Whyte et al. 1994). Morphologically be further spread in the sa n,e way. similar organis ms have since been found in clan1s from Massa­ Consequently. over the past 2 y, sa1nples of seed clams fron, chusetts. . and Virginia. hatcheries in seven states (Maine, Massachusetls. New York. Ne\v The proper classification of the QPX organism(s) is currently Jersey. Virginia, North Carolina. and South Carolina) have been under investigation, and there ,nay be more than one species in ­ exainined histologicall y for evidence of QPX. or QPX-like organ­ volved. Whyte et al. (1994) pointed out similarities of the Cana­ isms, by our three laboratories. Ln an effort to provide up-lo-date dian QPX to n1en1bers of the Thraustochytriales and Labyrinthu­ infonnation to seed producers, gro,vers, and resource 1nanagers, lales, which depending on the classification schen1e, belong to the we present our combined findi ngs in this report. phylum Labyrinthomorpha (Pokorny 1985) or to the phylum Laby­ rinthul on1 ycota (Porter l 990). Although 1nembers of these groups are com1non saprophytic organisms in marine and estuarine envi­ l\llATERIALS AI\'D l\f ETHODS ronn1ents (Porter 1990), they have also been reported to cause disease in molluscs, especial ly those held in captivity (Polglase Clam seed ranging in size from I to 25 1n1n (mostly < 15 111111 ) 1980. McLean and Porter 1982. Jones and o· Dor 1983. Bo\ver shell lengtl1 and generally no more tha n a fe~, months old \Vere 1987a). brought di rectly to participating laboratories or shipped 10 then, ln one reported d.i ease outbreak. n1orta]jties of up to IOOo/o overnight. The smallest clan, s ( 1- 5 mn1) \Vere placed directly into occurred in nursery-held juvenile , Haliotis ka1111scha1- fixative (J 0% fonnalin in seawater or Davidson's fixative); the kana (Jonas. 1845), that were heavLly parasitized by a Labyrin- hinges \Vere popped on clarns from about 5 to 15 n,m. and clan1s

519 520 FORD ET AL .

TABLE 1. List of hatchery-produced hard clam, l\1. 1nerce11aria, seed samples exanlined his tologically for QPX.

Co1Jectio11 Hatchery Hatchery Shell Nwnber Diagnos tic Date Location Code Length (nllll) Examined Laboratory

5/11/95 MA A 5-8 50 LAAMP 11 /9-27/95 J'vfA B 4-12 158 LAAMP 6/6/96 MA A 5-6 150 LAAJ\IIP 6/ [3/96 NJ C 11 - 16 23 LAAJ\IIP 6/21/96 ME~ MA* D 3-5 150 LAAMP 6/21/96 MA E ,;;2 75 LAAMP 7/24/96 NJ C 5-8 150 LAAMP 7/24/96 MA B 1-2 25 LAAMP 8/2/96 NJ ~ t-.1A * F 4-10 150 LAAMP 8/28/96 NJ F 10-14 I L6 LAAMP 9/13/96 NIA A 15-20 50 LAAMl' 10/16/96 N[A B 1-3 50 LAANfP 7/11/97 MA A 3-5 50 LAAMP 8/28/97 MA A 12-16 52 LAAMl' 8/28/97 NJ F 14-16 54 LAAMP 8/15/95 NJ G 4-10 80 HSRL L0/19/95 NY H 6-L2 80 HSRL 10/22/95 NJ G 6-12 240 HSRL 5/l/96 MA I 2 100 HSRL l/28/97 NY J 5-14 50 HSRL 9/25/97 NC K 7-9 50 HSRL 9/25/97 VA~ NJ* L 7-9 50 HSRL 10/6/97 NJ C 10-13 50 HSRL 2/20/97 VA M

Samples came directly from the hatchery/nursery. except for three samples(*) tl1at were held briefly m nurseries in different states before san1pling. Each hatchery was assigned a letter code (A-M) to differentiate among them. LAAMP, Laboratory for Aquatic Medic ine and Pathology; HSRL, Haskin Shellfish Research Laboratory: VTh1S. Virginia lnstitute of t\1arine Science. None of the clams was diagnosed with QPX. were placed in to fixati ve. In both cases. the shells 1,vere allo1ved to manner bet1veen May 1995 and October 1997 (Table l ). Only two decalcify in the fixative. Larger clams 1,vere shucked, and the n1eats srunples had been held in fi ltered ( L- 50 µ,111 pore size) water before were fixed. Clams 1-12 mm we re embedded whole in paraffin; examination: the rest had been held in upv,1ellers or raceways sup­ larger individuals were sectioned first. Ti ss ue sections were plied with unfi ltered sea,vater. An additional 756 hatchery­ rnounted on slides, stained, and exan1ined microscopicall y. A total produced clams in their first year of field growout 1vere examined of2,203 seed clains directly from hatcheries 1vere examined in this in the sa1ne tnanner (Table 2).

TABLE 2.

Lis t of hatchery-produced hard clam, ll1. 111erce11aria, seed san1ples examin ed for QPX during first year of field growout.

Collection Hatchery Growoul Growout Shell Nun1ber Diagn ostic Date Location Location Period (mo) Length {mm) Examined Laboratory

6/6&27/96 MA MA 7 6-12 136 LAAMP 4/24/96 NY NY 6 10- L2 100 HSRL 4/12/96 NJ NJ 6 6-8 120 HSRL 5/27/97 NJ NJ 8 20-25 50 HSRL 5/ 15/96 VA FL <6 4-10 60 VrMS 10/24/96 ME SC <6 8-15 60 VlNIS I 1/20/96 VA VA 9 5- L5 60 VJMS 5/13/97 VA SC 3 <5 60 VIMS 5/22/97 VA VA 6 7-8 25 VIMS 5/22/97 VA VA 5 9-13 25 VCMS I0/ 1/97 SC FL <6 12-16 60 VCMS Total 756

LAAJ'vlP. Laboratory for Aquatic Animal Medicine and Pathology: HSRL, Haskin Shellfish Research Laboratory; VL.\IIS. Virginia !J1stitute of Marine Science. QPX was not detected in any of the c lruns. ABSENCE OF QPX IN HARD CLAM SEED 521

RESULTS AND DISCUSS ION 1nonitored tbe acquisition of QPX infections in clams after lhey 1\fo QPX- like organi sn1 ,vas found in any of the 2,203 clams had been placed on infected leases and reported that none was originating directly from hatcheries. We cannot djscount the pos­ detected until clams had been in the field for at lea t I y. sibility that infection frequency \Vas so low that ,ve did not detect We believe that the n1ost reasonable interpretacion of the avail ­ parasitized individuals in our sa1nples or that our diagnostic n1elh­ abl e data is that hard clams beco n1e parasitized \Vilh QPX-like ods missed some very light infections; however. the large number organisn1s during field gro\vout , not in hatcheries. Whether these of clan1s that we examined rnakes this highly unlikely. Further, the organisms are facu ltative or opportunistic pathogens that in vade scope of ou r investigation-encon1passing 13 hatcheries in six clan1s already stressed by poor gro\vin g conditions is cu1Tently states. seed clan1s of varying size and age. collecti ons over 2 y, and under in vestigation. Mean,vhi le, we hope that this report provides examination by pathologists in three different laboratories-also reassurance to gro,vers. hatchery operators, and resource managers lends support to the contention that hatcheries are not the source of that hatchery seed is an unlikely source of QPX-like parasites in QPX. Ln the late 1980s and early 1990s. six to eight san1 ple of 50 hard cla111s. seed clrun s each, fro n1 hatcheries in M.assachusetts ru1d New Jer­ AC KNO\.VL EDGMENTS sey, were examined histologicall y without detection of any nticro­ organism resemb ling QPX (R. Hillman. Bauelle Sciences, We thruik th e man y hard clam seed producers who provided pers. comm. 1997). seed clams for diagnosis and Juanita Wa lker and Rita Crockett. The evidence that seed clams canting directly fro m ha tcheries who performed histology at Virginia Insti tute of Marine Science do not contain QPX-li ke organisn1s is further supported by histo­ (V IMS). The 1vork reported in this publication ,vas supported in logical examination of hatchery-produced clarns diagnosed within part by the Northeastern Regional Aquaculnire Center ac lhe Uni ­ a year of placement in field growout locations (Table 2). No QPX­ versity of Massachuseus Dan111 outh, through Grants No. #92- like organisms we re fou nd in any of the 756 clams originati ng 38500-7142 and 96-38500-3032 (to R. Smolowitz) and 93-38500- fro,n hatcheries in six states and examined after periods ranging 839 l (to J.N. Kraeuter), frorn the Cooperative State Re earch. frorn 3 to 9 ,no in the field. fn fact. all findings of QPX-li ke Education. ru,d Extension Service of th e Departm en t organisn1s in hru·d clams under cul ture in the Un.ited States have of Agriculture. Tltis is Publication No. 97-21 of lhe Institute of been in adults, typically l.5-2 y or older (Ragone Calvo et al. tvlarine and Coastal Sciences at Rutgers and VIMS concribu ti on 1997. Smolowitz et al. in press). S111olowiLZ and Leavitt (1997) No. 2099.

LITERATURE CITED Bower, S. M. 1987a. Labyrinthuloides haliotidis n. sp. (Protozoa: Laby­ Polglase. J. L. 1980. A preLiminary repon on the Thraustochytrid(s) and rinthomorpha}. a pathogenic parasite of s1nall j uveni le abalone in a Labyrinthulid(s) associated with a pathological condition in the lesser British Columbia [email protected] facility. Can. J. 'Zoo/. 65: 1996-2007. Eiedone cirrhosa. Bot. i\1ar. 23:699- 706. Bower. S. M. l987b. Palhogemcity and host specificity of Labyri111h11- Porter. D. 1990. Phylum Labyrinthomycota. Ch. 22. pp. 388-398 In: L. loides l1alio1idis (Protozoa: Labyrinthomorpha). a parasite of juvenile Margulis, J. 0 . Corli ss, M. t-.1elkonian. and D. J. Chapman (eds.). abalone. Can. J. Zoo/. 65:2008- 2012. Handbook of Protoctista. Jones and Bartlen. Boston. Drinnan, R. E. & E. B. Henderson. I963. 1962 Monalities and a Possible Ragone Calvo, L. M .. J. G. Walker & E. M. Burreson. 1997. Occurrence of Disease Organism in Neguac Quahaugs. An11uaJ ReporL Biological QPX. Quahog Parasire Unknown. iH Virginia hard clams, Mercenaria Stauon. St. Andrews. New Brunswick, Canada. 111erce11aria. J. Shellfish Res. 16:334. Jones, G. & R. K. o·oor. 1983. Ultrastructural ob~ervations on a Thraus­ tocbytrid fungus parasi1ic in the gills of (/!lex illecebrosus Smolowitz. R. & D. Leavitt. 1997. Quahog Parasite Unknown (QPX): an Lesueur). J. Parasitol. 69:903-9 I I. emerg 111g di sease of hard clan1s. J. Shellfish Res. I6:335-336 . McLean, N. & D. Porter. 1982. The yellow spot disease of Tri1011ia di­ Smolowi1L, R., D. Leavitt & F. Perkins. 1998. Observations of a protistan omedea Bergh. I 894 (: : NudibrancbiaJ: Encapsu­ disease similar to QPX in 1Werce11aria mercenaria (hard clams) from lation of the Trauscochytreaceous paras ite by host amoebocytes. J. the coast of Massachuseus. J. f11 vertebr. Pathol. 7 I ( I ):9- 25. Parasiioi. 68:243- 252. Whyte. S. K.. R. J. Cawthorn & S. E. McGladdery. 1994. QPX (Quahaug Pokorny, K. S. 1985. Phylum Labyrinlhomorpha. pp. 318- 321 f11 : J. J. Lee, Parasite X) a pathogen of northern quahaug Mercenaria mercenaria S. H. Hutncr. and E. C. Bovee (eds.). illustrated Guide to tbe Protozoa. from the Gulf of SL. Lawrence. Canada. Dis. Aquar. Org. 19:129- Society of Protozoolog isis. Lawrence. KS. 136