Cholangioma in a Wild-Caught Sheepshead Minnow (Cyprinodon variegatus) from the Northern Gulf of Mexico

3 Pages·1996·2.3 MB·English

by  Lee A Courtney

GulfResearchReports.Vol.9, No.3, 211-213,1996 ManuscriptreceivedJune30.1995; acceptedAugust14,1995
CHOLANGIOMA IN AWILD-CAUGHT SHEEPSHEAD MINNOW
(CYPRINODON VARIEGATUS) FROM THE NORTHERN GULF OF MEXICO
LeeA.Courtney
U.S. Environmental Protection Agency, National Health and Environmental Effects
ResearchLaboratory,GulfEcologyDivision,CenterforMarineandEstuarineDisease
Research,JSabineIslandDrive,GulfBreeze,Florida32561-5299,USA
ABSTRACTAsinglecaseofacholangiomaoccurredintheliverofawild-caughtsheepsheadminnow(Cyprinodon
variegatus). Thisisthefirstbiliaryneoplasmandsecondcaseofahepaticneoplasmreportedfromawild-caught
specimen!ofthis species. Thefmdings furtherdemonstratethesusceptibility ofthesheep.shead minnow to
neoplasmdevelopmentandaddsupporttoitsselectionasasubjectforfieldmonitoringofcarcinogenicexposure.
Introduction MaterialsandMethods
The use of fish species as sentinels ofcarcinogen Approximately30sheepsheadminnows(Cyprinodon
exposureintheaquaticenvironmeniisasignificanttoolfor variegatus) were collected in a lagoon off Santa Rosa
identifying compromised ecosystems. Many important Soundon thenorth shore ofSantaRosaIsland, Florida,
attributesoffishsentinelsmaketheiruseinexperimental approximately 2 kilometers east of the Navarre Beach
carcinogenicitytestingandfieldmonitotingbothefficacious bridge.Specimenswerecollectedbyseinenet,culventrally
andadvantageous(DaweandCouch1984),Oneimportant toopenthevisceralmassandimmersedinBouin’ssolution
consideration,particularlyregardingfieldmonitoringfor in the field. They were fixed for 48 hours, washed in
environmental carcinogens, istherelatively low rateof runningwaterforsixhoursandstoredin70%ethanolat
spontaneousneoplasmdevelopmentinfishes.Furthermore, roomtemperature.Liver,intestineandkidneytissueswere
a high correlation has been demonstrated between dissectedfirom 10ofthepreservedspecimens,dehydrated
environmentalcontaminationandmostreportedepizootics inagradedethanolseries,clearedinxyleneandembedded
ofhepatic neoplasms in fishes (Harshbarger and Clark inparaffin. ScctianswerecutonaTotaiymicrotomeatSpm,
1990: Baumaim 1992). These factors emphasize the mountedonpoIy-L-lysinecoatedslidesandairdried.Initial
importanceofhepaticneoplasmsinnon-treatedfishesand, sectionswereprocessedforimmunohistochemicallabeling
particularly,inwildpopulations. withfourdifferentP-glycoprotcinantibodies[monoclonals
The sheepshead minnow, Cyprinodon variegatus C219, C494 and JSB-1; polyclonal mdrfAb-l)] and
Lac6p5de,hasdemonstrateditssusceptibilitytochemically- counterstained with Mayer's hematoxylin (Hemmer et al.
induced hepatic neoplasm development in various 1995), Additional sections were stained with Harris*
caicinogenstudies(e.g.,CouchandCouitncy1987;Hawkins hematoxylinandeosin.
etal. 1991). Itisasmallestuarineteleostwithalimited
homerangeinhabitingcoastalwatersfromNewEngland ResultsandDiscussion
tonorthernSouthAmerica. Todate,theonlyreportsof
spontaneous neoplasm development in sheepshead During evaluation of samples for P-glycoprotein
minnowsinvolvethyroidadenomasinaquarium-held antibodyreactions, aneoplastic lesion wasfound inthe
specimens(Nigrelli1952;LightnerandMeineke1979) liverofonespecimen,anadultfemale(4.5gmwetweight;
andasinglecaseofhepatocellularadenomainawild- 50 mm SL). The lesion was a well-circumscribed
caught specimen (Oliveira et al. 1994). This paper cholangioma approximately 750 x 960 pm in greatest
describesacholangiomafoundinawild-caughtshecpshead dimension. Itoccupied-2.5%oftheliverareaintheplane
minnow from an ongoing study on P-glycoprotein ofsectionexaminedajidwassituatedattheperipheryofthe
expressionintissuesofteleostfishesandthepossiblerole liver (Figure 1). The lesion had regular, well-defined
of xenobiotics in the disruption of its function as a borderswithnoinvasionintosurroundingparenchyma. It
iransepithelial efflux pump (Hemmer and Courtney, consistedofnumerouswell-formedbileductspossessing
personalconununication). nonnal-appearingcuboidalepithelium withinaminimal
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Figure 1.Lowpowermagnificationshowingwell-circumscribedcholangiomalocatedatperipheryofliverofasheepshead
minnow{Cyprinodon variegatus). (H&C;76x).
Figure2. High powermagnincatiouofthecholangiomashowingwell-definedbileductsconsistingofnormal-appearing
cuboidalepithelium,rangingfromcirculartomultilocularinprofileandsurroundedbyaminimalconnectivetissuematrix.
(H&E;257x>.
212
CholangiomainaWild-CaughtSheepsheadMinnow(Cyprinodonvariegatus)
matrixofconnectivetissue(Figure2). Bileductprofiles rangeinmonitoringforenvironmeniaJcarcinogens. This
ranged from small circular configunflions to relatively study showed that a few hundred meters can make a
large muliilocular structures. No mitotic figures were significant difference in the histology of fishes located
noterl. NopositivereactionwithanyoftheP-glycoproiein aroundapoint-sourcecontamination.
antibodies tested was observed. The architecture and Most other sheepshead minnows used at the Gulf
cellularprofileofthislesionresembledthatofcholangiomas Breeze EPA laboratory were collected at sites several
described from field collections (e.g„ Daweetal. 1964; kilometerswestofthelocationwherethesespecimenswere
Myersetal.1987;BuntonandBaksi1988)andofchemically- sampled. Thesignificanceoffindingonehepaticneoplasm
induced cholangiomas reported from various small fish at this site in a sample of only 10 fish histologically
species(e.g..Hawkinsetal.1988;GrizzleandThiyagarajah1988). examined isunclear. As in the reportofOliveira et al.
Thepresentcaseisimportantinthatitrepresentsonly (1994),thepresentcasedoesnoiconsiiiuteanepizootic,and
thesecondcaseofahepaticneoplasmfromawild-caught thecollectionsiteisconsidered uncontaminated,withno
sheepsheadminnow. Furthermore,thisisthefirstreport significant commercial or residential development in its
of a biliary neoplasm from this species that was not generalvicinityandnootherapparentsourcesofxenobiotic
experimentally-inducedorfromanyotherwild-caughtfish contamination. Nevertheless, this report further
speciesintheGulfofMexico. Numerousspecimensfrom demonstratesthesusceptibilityofthesheepsheadminnow
wild and laboratory-reared populations of sheepshead toneoplasticdevelopmentandsupportsits selectionas a
minnowsfromthenorthernGulfofMexicohavebeenused subjectforfieldmonitoringofcarcinogenicexposure.
intoxicityandcarcinogenicitystudieswithnoneoplastic
lesionsreportedfromanyuntreatedexperimentalspecimens Acknowledgment
(seeCouch and Courmey 1987) and only one neoplasm
observed from a wild specimen (Oliveira et al. 1994). I wish to thankDr. JohnFournie for examining the
Theseobservationssupportaverylowrateofspontaneous slidesandconfirmingthediagnosis. ThisisContribution
neoplasm development in the sheepshead minnow, an 932oftheU.S.EnvironmentalProtectionAgencyNational
important consideration in the evaluation of results of Health and Enviromnenial Effects Research Laboratory,
carcinogenicitytestsandinfieldmonitoring.Furthermore, GulfEcologyDivision,GulfBreeze,Florida(formerlythe
Vogelbeinelal. (1990)demonstratedthesignificanceof U.S. EPA Environmental Research Laboratory, Gulf
utilizing small fish species that have a restricted home Breeze).
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