Feeding Biology, Distribution, and Ecology of Two Species of Benthic Polychaetes: Paraonis fulgens and Paraonis pygoenigmatica (Polychaeta: Paraonidae)

5 Pages·1992·2.7 MB·English

by  Gary R Gaston

Gu^ResearchRepoHs,VoL8,No.4,395-399,1992 ManuscriptReceivedJuly16,1992;acceptedAugust10,1992
FEEDING BIOLOGY,DISTRIBUTION,AND ECOLOGY
OFTWO SPECIES OFBENTHIC POLYCHAETES: PARAONISFULGENS
ANDPARAONISPYGOENIGMATICA (POLYCHAETA: PARAONIDAE)
GARYR.GASTONSJERRYA.MCLELLAND*,AND
RICHARDW.HEARD'
JDepartmentofBiology,UniversityofMississippi,University,Mississippi 38677
^GulfCoastResearchLaboratory,P.O.Box7000,OceanSprings.Mississippi 39S64
AB^RACT ParaonisfulgentandParaonispygoenigmaticainhabitsandyUltoralandsubliltoralsedimentsofthenorthern
GulfofMexicoandU.S.EastCoast,butseldomoverlapindistribution. Thepurposeofthisstudywastocomparethefeeding
ecologyanddistributionofthesespecies.WeanalyzeddistributionsandgutcontentsofGulfofMexicospecimensandfound
thatP.fulgentinhabitedsubstrateswithslightlymoresiltandclaythanthoseinhabitedbyP.pygoenigmatica. Although
ParaonisfulgensingestedmorediatomsthanP.pygoenigmatica,thisdistinctionlikelyresultedfromhabitatdifferences,not
selectivefeeding. PreviousstudiessuggestedthatP.fulgensfedselectivelyondiatomsonly.
Introduction andAssessmentProgram(EMAPO;andoffAlabama,Texas,
andtheMiddleAtlanticBightbytheauthor(Gaston1985,
ThegenusParaonisCenuti, 1909,containsjusttwo 1987).
species,Paraonisfulgens and Paraonispygoenigmatica. Percentage of ingested food was estimated under
Paraonisfulgensisdistributedworldwideinshallowestu- compoundmicroscopyaspercentagerepresentedbydia-
arine and marinehabitats (Strclzov 1973). However,P. toms(estimatedvolume)versuspercentagerepresentedby
pygoenigmaticaoccursonlyincoastalwatersofthe U,S. detritus. Noneofthegutsexaminedwereentirelyempty.
Atlantic(Jones1968)andnorthernGulfofMexico(Gaston StatisticalanalysesinvolvedaT-testforsignificantdiffer-
1984). Both species inhabitsandy substrates; P.fulgens ences(a=0.05)betweenspecies(whentheBartlettTest
generallyinhabitslittoralandsublittoralsedimentsandP. indicated homogeneity ofvariables) using arcsine-trans-
pygoenigmaticalivesinslightlydeeperwater. Apparently, formedpercentagedata(percentageoffoodrepresentedby
onlyP.fulgensoccursindensepopulations(Gaston1984). diatoms).
Ro^
(1971)andRiskandTunnicliffe(1978)reportedthat
P.fulgensfed solely ondiatoms,but littleelse isknown ResultsandDiscussion
aboutthefeedingecologyofthesespecies.
Thepurposeofthisstudywastocomparethefeeding BothP.fulgensandP,pygoenigma!teainhabitedsandy
ecology and distributionofthesetwospeciesinnorthern substrateswithsimilarsedunenicharacteristics(Table 1).
GulfofMexicohabitats. Weinvestigatedingestedfoodsto Paraonisfulgenswasmostabundantinsandyintertidaland
determineifdifferencesmfoodaccountedfortheirdistinct shallowsubtidalhabitatswith96-99%sand(i.c.,lessthan
distributions. 4%siltandclay)asindicatedinTable2. Paraonispygoe-
nigmatica inhabited slightly deeper-waterhabitats with
2-3%sillandclay(Tables 1and2).
MaterialsandMethods Paraonisfulgenswasoneofthemostabundantmac-
robemhic organisms collected in the shallow waters off
Mostofthespecimensexamined forthisstudywere PerdidoKey,FloridaandHornandShipIslands, Missis-
collected by Gulf Coast Research Laboratory (GCRL) sippi. TheirnumberspeakedatbothShipIslandandHorn
personnel offBiloxi, Mississippi, Ship and Horn Island, Islandduring August 1990 atover lO.OOO/m^ (Table I).
Mississippi andPerdido Key,Florida (Rakocinski et al. Colonizationofthesedimentsbysettlingjuvenilesappar-
1991,McLellandandHeard1991). Additionalspecimens entlyoccurredduringsummer. Paraonispygoenigmatica
werecollectedaspanofaBureau ofLand Management wasseldomasabundantas (Table1). Itoccurred
M
(now ineralsManagementService)GulfofMexicoOuter fromsubtidaltooutercontinentalshelfwaters,andseldom
ContinentalShelfbaselinestudyconductedduring 1975- wascollectedatthesamesitesasP.fulgens(Table1). In
1981 (Uebelackerand Johnson 1984); along theFlorida Perdido Key, P.fulgens inhabited sandy sediments be-
Gulf Coast by Mote Marine Laboratory personnel; off tweenthebeachandsandbarjustoffshore(0-5.5m)and
PadreIsland,Texas(RabalaisandFlint 1983);inPelican P. pygoenigmatica occurred beyond the sand bar (5.5 -
Bay,AlabamaduringtheEPAEnvironmentalMonitoring 5.8m)asshowninTable2.
395
396 Gaston
TABLE
1
SelecteddistributionrecordsandpopulationdensitiesofParaonisfulgensandParaonispygoenigmaticainthe
GulfofMexico andsouthernFloridaAtlantic Coast Depths in meters.
Site Depth(s) Sediments Denaty/m^ Source
Paraonisfulgens
Horn Island, MS <1.0-30.0 >97% sand 1500-10,000 GCRL*
ShipIsland, MS 15.0-30.0 >96% sand 2000-12,000 GCRL*
BiloxiBay, MS 0.1-0.2 sand <500 Matulewski**
Pelican Bay,AL 2.4 sand <10 Gaston **
Mobile Bay,AL 2.4-3.6 sand 20-800 Gaston **
Mobile Bay,AL 4.0-6.5 sand <500 Johnson 1980
Perdido Key, FL 1.0-5.5 sand ** 500-8000 GCRL*
FL Continenlal Shelf 19.0-20.0 finesand <10 Gaston 1984
MarcoIsland,FL 0.5-1.0 sand <50 Milligan **
Padre Island,TX 0.1-2.0 finesand mean=200 Rabalaisetal. 1983
Paraonispygoenigmatica
Ft.Lauderdale,FL 10.0 sand Milligan **
PerdidoKey, FL 1.0-5.5 sand *** <50 GCRL*
offTampa,FL 20.0-24.0 finesand 10-60 Gaston 1984
* DatafromtwoGulfCoastResearchLaboratorystudies(McLellaitdandHeard, 1991;Rakocinskietal. 1991).
** UnpubDsheddata: K.Maiulewski(UniversityofSouthernMississippi),G.Gaston(UniversityofMississippi),
M. MilliganandA. McAllister(MoteMarine Laboratory),EMAP-NC 1991 GulfofMexico estuary survey.
*** SeeTable 2 formore sediment data
Paraonisfulgensisasubsurfacedetritivore. Itfeedsin only dialoms. Althoughdiatomswereingestedbymany
tight spirals beneath the sediment surface, and moves specimens that we examined (Table 3), diatoms were
upwardordownwardasitcompletesafeedingspiral(Risk apparentlyingestedpassivelywithotherdetritus. Mostof
andTunnicliffe1978). PreviousresearchindicatedthatP. ourspecimenswerefilledwithdetritus,whichincludeda
fulgensselectivelyingestedbenthicdiatoms(Roder1971, fewdmoflagellateanddiatomtests. Itdidnotappearthat
RiskandTunnicliffe 1978),whereasotherparaonidsfeed diatomsand/ordinoflagellates wereselectivelyingested;
ondriftdebrisordetritusand areprobablynon-selective mostingesteddiatomsweresmall,unlike thoseobserved
(FauchaldandJumais 1979,Gaston 1983). Roder(1971) byRoder(1971), and therewere severaldiatomspecies
noteddialspecimensheexaminedcontainednodetritus, represented.Furthermore diatomsseldomcomposedeven
,
FeedingEcologyofParaonissit. 397
TABLE!
HabitatandsedimentcharacteristicsofsiteswhereParaonisfulgens(F/)andParaonispygoenigmaSkaiP.p,)
werecoDectedatPerdidoKey»Florida. Abundances; C=Common(>1000m'^); R=Rare(<20m‘^). From
RakocinskietaL (unpublished data).
Abundance % Sand
Station P/./P.P. Depth (m) (md. dia) % Sili/clay
1. Littoral * C - 1.0 98.8 (0.29) 1.2
2. Littoral C - 2.0 99.6(0.25) 0.4
3.Longshorebar c - 1.0 98.9 (0.21) 1.1
4. Sublittoral ** c - 2.1 99.6(0.20) 0.4
5. Sublittoral c - 3.7 98.6(0.20) 1.4
6. Sublittoral c - 4.3 98.7 (0.28) 1.3
7. Sublittoral C R 5.5 99.5 (0.30) 0.5
R
8. Sublittoral - 5.5 99.7 (032) 0.3
9. Sublittoral - R 5.5 97.4 (0.28) 2.6
10.Sublittoral - R 5.5 96.7 (0.25) 3.3
11. Sublittoral - R 5.8 97.7 (0.24) 2.3
Littoral=betweenbeach andlongshorebar.
** Sublitioral =outside the longshore bar.
half ofthe matter ingested (Table 3), andmany lacked {P,fulgensandDispioundnaia\andatanaid{Kalliapseudes
chlOTOphyU. indicating that they were probably empty sp.) (Rakocinski et al. 1991). A similar trophic group
frustuleswheningested. dominated theircommunities offMobile Bay, Alabama
Likemanyparaonids.P.pygoenigmaiicaisasubsur- andPerdidoKey,Florida,includinghaustoriidamphipods,
facedetridvore(FauchaldandJumars1979,Gaston1983). theisopod{B.diminutum),and(hesamepolychaetes(Gaston
ItislesscommonlycollectedthanP.fulgens,asevidenced 1986, R2kkocinsldetal„manuscript). These dominants
bythefewnumbersofspecimensonTable3. Whetheror werecollectedin habitatsofboth speciesofParaonisal
notitfeedsinspiralsisunknown. Gutcontentsofspeci- Perdido Key, even though P.fulgens and P.pygoenig-
menscollectedinPerdidoKeyandintheMiddleAtlantic maticaseldomwerecollectedtogether (Table2),
Bightwerefilledwithdetritus,butincludedfewerdiatoms ThesedimentswhereP,fulgens wasmostabundant
thanwereingestedbyP.fulgens(P<0.01.Table3), weremoredynamicthanthoseinhabitedbyP.pygoenig-
These two species ofParaonisaremembers ofthe matica. Perhapsmorediatomswereburiedinthedynamic
sandylittoralandsublittoralcommunitiesoftheAtlantic sedimentsandbecamedetritus forgrazingP.fulgens, as
andGulfofMexico. TheircommunitieswerenumericaUy suggestedbyRiskandTunnicliffe(1978). Unfortunately,
dominatedbycrustaceansinthenorthernGulf;offWest the environmental and gut-contents data provided Little
Ship Island, Mississippi the dominant taxawereanam- additionalinformationonthedistinctionofthehabitatsof
phipod(Lepidactylussp.),anisopod{Exosphaeromadimi- thesetwospecies. Apparently,P.fulgensfeedsondetritus
nu/um),acumacean{Spilocumawatlingi\twopolychaetes that includes diatoms, but P,pygoenigmatica does noL
398 Gaston
TABLE3
Gut-contentsdataoftwospeciesofParaonis from three locationsinthe GulfofMexico. Percentagevalues
arepercentvolume, estimatedtothe nearest5%. Specimenscollected in differentsamples arepresentedas
separate data.
Site Numberexamined % Diatoms % Detritus
P.futgens
Horn Island, MS 6 10 90
Horn Island,MS 2 25 75
Horn Island, MS 1 50 50
PerdidoKey, FL 2 <5 95
Perdido Key,FL 4 10 90
Perdido Key, FL 7 25 75
Perdido Key,FL 4 50 50
Pelican Bay,AL 1 <5 95
Totals/Means 27 21.1 78.9
P.pygoenigmatica
Perdido Key, FL 10 <5 >95
offTampa.FL 2 0 100
Totals^eans 12 1.6 98.4
Thus,eventhoughthese two species are closelyrelated, Acknowledgments
We
theirfeedingbiologyisdistinct proposethatdissimilar
habitats,and theabundanceofdiatoms inthosehabitats, WethankK.Matulewsld(GCRL)forhelpwithspeci-
accountfortheirdistinctive feedingbiology. P.futgens mencollectionsandC.Rakocinski(GCRL)forhelpwith
foragesfordetritus(whichmaybediatom-ladendetritus) data pioccssing. A. McAllister and E. Fenstermacher
in dynamic sediments of littoral and subliiioral zones, reviewedthemanuscriptandhelpedwithspecimendissec-
whileP.pygoenigmaticaisassociatedwithlessdiatoma- tions.WethankM.Milligan(MoteMarineLaboratory)for
ceousdetritusinlowerenergyhabitatsbeyondtheswash providingspecimens.
zone.
FeedingEcologyofParaonisspp. 399
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