Namalycastis abiuma (Müller in Grube) 1871, an Aberrant Nereidid Polychaete of a Georgia Salt Marsh Area and its Faunal Associations

12 Pages·1994·8.1 MB·English

by  Erik Rasmussen

GulfResearchReports,Vol.9.No.1,17-28,1994 ManuscriptleceivedDecember16,1991;acceptedOctober18.1993
NAMALYCASTISABIUMA (MULLER IN GRUBE) 1871,
AN ABERRANTNEREIDID POLYCHAETE OFA
GEORGIASALT MARSH AREAAND ITS FAUNALASSOCIATIONS
ERIKRASMUSSEN
ZoologicalMuseum,UniversityofCopenhagen.UniversUetsparken15.
DK-2100Copenhagen,Denmark
ABSTRACT ThemoiphologyoftheaberrantncreididNamalycastisabiuma,NamanereidinaeUdescribedonthe
basisofmaterialcollected1971-72and1976inthebrackishwaterdrainageditchsystemofSapeloIsland,Georgia,
USA, Thesyslcmaticsofthespeciesisbrieflyreviewed. Thehabitatandecologicalconditionsunderwhichthe
specieslivesinthesebrackishditchesaredescribed.
M
Atvarioustimes, abiumalivesoutofwaterunderthebarkoftrunksandbranchesoffallentrees. Decaying
woodisingested. Itissuggestedthatfuturestudiesshouldconcentrateonthereproductivebiologyofthewidely-
spread,mainlytropicalpopulationsofwhatmayprovetobenotone,butseveralspeciesofNamalycastis. Alist
oftheinvertebratefaunaassociatedwithN.abiumaisincludedwithnotesontheseassociates.
iNTRODUCnCW
attempthasbeenmade tocharacterizeecological condi-
tionsunderwhichthespeciesoccurred,itsmodeoflife,and
Namalycastisabiuma(Namanereinae,Nereidae)was itsfaunalassociates.
describedbyMullerinGrube,1871asParanereisabiuma.
Elevencloscly-relaiedspeciessubsequentlywcjncdescribed
under thegeneric nameLycasiis. Thesespeciesoccurin Materials andMethods
ftesh water lo brackish or almost fully marine habitats
(Wesenberg-Lund, 1958). Allspecieswerereferredtoby
the new genericnameNamalycastisby Hartman(1959), SiteDescription
withthecommentthatall“arebelievedtorefereithertoa
singlespeciesresemblingthetype,ortocloselyrelated,and Thestudyareaencompassedshallowdrainageditches
genericallyidenticalforms*'(p.163).Hartman'sdiagnosis, onSapeloIslandconnectedtotheseaonlyduringperiods
based on material from Florida, has been generally ac- ofextremehighwater, Ascriesofditches,dwindlinginto
cepted(Foster,1972;Gardiner,1976;GardinerandWilson, poolsatlowwaterwithdifferentsalinityconditions,were
M
1977; Heard, 1975, 1982). Heard (1982) ^onymized chosenforsampling. Populationsof abiumawerefound
Lycastopsis Rioja,1946,L.ponr/caJakubova, atonly two of10stationssurveyed: Station 1,the main
1930,amiL.hummelinckiAugener, 1933,allfromNorth stationregularlyexaminedduring1971-72,andStation10,
Carolina,Georgia,FloridaandLouisianawithN,abiuma, asupplementarystationvisitedonlyafew timesin 1976
N.abiumawasreportedfromAustraliabyRussell(1962) (Figure1). Station I(Figure2),situatedonemilenorthof
andN. cf.abiumaby HutchingsandGlasby(1985), Al- theSettlement,wasaroadsideditchabout4mwideand
thoughitmayseemdifficultloacceptthatHartmanrightly varyingindepthfromafewcmduringdryperiodstomore
synonymized 11speciesofAbiuma^consideringthediver- than0.5matspringtides. Thebottomlayerwassoft,fine,
sityoftheirhabitats,itmustbenotedthatonlyalimited blackishmudwithsomesmellofhydrogensulphide.Fallen
numberofsystematiccharacteristicsareavailable,e.g.,a tree trunks and decaying branchesfrom thesiuiounding
pharynxwithoutparagnaihsorpapillae,reducedpaiapodia, pine forest were piled up in part of the ditch system.
elc. Therefore,untilamorethoroughrevisionofthemany Rickards(1968)gaveashortdescriptionofthisstudyarea.
formsisavailable,itseemsreasonabletoacceptHartman's ExceptforasmallpatchofRuppiamaritimaL.,present
inclusionofthemasmembersofAbiuma. onlyin1976,theditcheshadnosubmergedvascularplants.
Inthispaper,thesystematicsofN.ab/amnwerebriefly Thesurfaceofthemudwascoveredwithadensebrownish
reviewedandsomemorphologicaldetailsweredescribed layerofdiatomsduringperiodswithcleardirectsunshine.
based on material from brackish water in Georgia. An Tufts of perennial glasswon (Salicornia virginiana L.)
17
18 Rasmussen
Figure1. SapeloIsland,Georgia,withtidalcreeks,ditchesandpools. Numbersindicatesamplingstations.
werefoundonthebankoftheditchnearthesaltgrasscover {SpartinaalternijloraLois.)occurredinsomeplacesalong
{Disdchlisspicata(L.)Greene).Lowbushesofmarshelder thebankedgesandoftenextendedacrosstheditchtoform
(Ivafrutescens L.) fonnedatransitional border nearthe thresholds that often impeded the upstream flow ofsea
forestintheDisdchlismarshclearings. Saltmaishgrass water.
AberkantNereididPolychaeteofGh)rgiaSaltMarsh 19
Figure2. PholographshowingpartofStation1,aroadsideditchwithSpartinagrassalongthebanks(totheright,oppositethe
ro^). Behind theDistUhtisgrasscoverbushesofmarshelder {Ivafrutescens)are bordering the pine tree forest in the
background(April23,1971).
Station 10 was a ditch located between steepbluffs Incontrast. 1976wasanextraordinarilydryyear. At
whichranparallelto(heroadbetweentheKingSavannah StationIfromMarch13toApril16.totalprecipitationwas
clearingandtheBellMaishneartheHighPointroad. Itwas ca.27mm (seasonal noim 182 imn). Theditchbecame
surroundedbydenseforest. Thesteepbanksoftheditch almost dry in April, and the remaining stagnant pools
reached2mabovethebottom. Thebottomsedimentwas becamehypersalineatca.807oo. ButonApril 12.asingle
virtually clean sand with plant remnants and scattered intrusionofseawateralaspringtideraisedthewaterlevel
Spartina. Thebanksweretoppedwithadensegrowthof to40cmandloweredthesalinitytothatofnormalseawater.
marshelder. The ditchwas nearly dry duringsampling Itappearsthatfructuatioasinsalinityoverarangeofca.2Ww
periods. Directaccesstoseawatergavethisdiicharegular areausualoccurrenceinspringandearlysummer. TheSfryoo
tidalcycle. eventrcpre.sentsanextremedialthefaunaoftheditches
must endure occasionally, possibly by retreating to the
Salinity underbark refuge outofwater. This may presentother
stresses,suchashightemperatureandtheriskofdesicca-
SalinitywasmeasuredwithaT/Cre&actometer(Ameri- tion.
can Optical Orp.). Salinity at Station 1 varied greatly
accordingtotheirregularrainfallpattern. Duringmostof Temperature
1971-72,thesalinityvariedfromca.lO%otoca.307(»»but
droughtcombined withhighairtemperature and intense Temperatures were measured from April to August
sunlightraisedthesalinityto56 inJune1971. However, 1971 withamercurythermometer. FromlateSeptember
heavyrainsinJuneandJulyreducedthatsalinitytoAVoo 1971 toearlyFebruary 1972,watertemperaturewasmea-
withinafewdays. suredeachweekwithapermanentlysubmersedmaximum-
20 Rasmussen
minimummercuiythennomeierthatshowedthetempera- (Figure3).Whatmaybemoreimportantisthefactthatthe
turerangeduringihcpastseveiidays.FromMarch14-27» narrowertemperaturerangeinthemud(15®Cto26.5°at
the temperature range was measured continuously 1cmdeptli;20°to30°Cat15cm)mightenablesomemobile
with a Gram MiniatureTemperatureRecorder with animalstosurviveunderextremeenvircHunenvalconditions
siK channels registering the air temperature, water byburrowingintothemud. However,suchanescapemay
surfacetemperatureinthemiddleoftheditch,water subjectthemtoanoxicconditions.andM wasnever
surfacetemperaturenearthebank,temperaturenear actuallyfoundinthemudinthisstudy.
thebottom,temperature 1 cminthemudbottomand
temperature 15cmdeepinthemudwithawaterlevel
rangingfrom0.5toabout40cm(Figure3). Rainfall Namalycastisabwma
recordsfor1971-72wereoblainedfromthemeteoro-
logical stationofthe University ofGeorgia Marine DescriptiveNotes
Institute. During the 1976sampling, precipitationwas
checked by a rain gauge placed on the ground close to Mature specimens measure about 50 to 100 mm in
Station 1. Water level was measured daily against a length, with up to 170 setigers. Body with two, not
measuringrodplacedintheditch(Figure2). distinctlyseparablesections. Anteriorthirdtohalfrather
ThetemperaturerangeatStation1wasverylarge,both slenderandcylindricalwithrelativelyfewsegments,restof
seasonallyanddaily,influencedbychangesinairlempera- body becoming flattened posteriorly, with segments in-
tuieandsolarradiation. Afteraperiodofrhythmicfluctua- creasinglyshorter.Livingammalstranslucenkunpigmented.
tions in Apriland May 1971 varying between22‘’C and Colordeterminedbycontentsofredblood,increasing in
32'^C,thehonestperiodinthe1971-72studycameinJune intensityposteriorly. Dorsalsurfacesomewhatglossyin
andlastedthroughSeptember,withapeakofnearly37'’C reflected light. Epidennis of each segment witli fine
inJune. Amorepreciseestimateofthetemperauirerange transversewrinkles(Figure4). Prostomium trapezoidal,
wasachievedwiththeintroductionofregularmaximum- anteriorlyincised,withshortmediangroove. Twosmall
minimunvtemperaturerecordingoftheditchsystemwater conical antennaeand twoconspicuous,broadpalps with
fromSeptember26throughtherestoftheresearchperiod. distinctpalposiylcs; the palpsarcrhythmicallyextended
AminimumofO^CwasrecordedinJanuary 1972, when the worm crawls. Posterior part of prostomium
FromMarch14-27, 1976,thewamtemrlevelofthepool broaderwithtwopairsofeyes,blackinreflectedlight,the
inStation1variedbetween10and27 andthetempera- outer eye on each side larger (Figure 4). Fourpairsof
turerangedbetween12®Candnearly3PC,neverattain- tentacular cirri, the hindmost pair longest. First segment
ingthelowleveloftheairduetothestrongsolarradiation achaetous.Pharynxstronglybuilt,withoutparagnaihsorpf^-
SAPELO ISLAND DITCH SYSTEM NO. 1 TEMP RANGE MARCH 14.-27.1976
^C 5 10 15 20 25 30 35
I I I I •
AIR
SURFACE
"j
NEAR BANK I WATER
NEAR BOTTOM
J
CM
^ 1 IN ^ BOTTOM
15 CM IN J
I
Figure3. TemperaturerangeinairandditchatStation1,SapeloIsland,Georgia,March14-27,1976.Measuredcontinuously
duringthisperiodwithasix-channeltemperaturerecorder. Allmeasurements,except"nearbank",madeoverandIn the
centralanddeepestpartofthediteb. The“bank"channelwasatthesurfacenearthewateredge. Depthduringrecordingfrom
10to27cm,fallingto9cm.
AberrantNereididPolychaeieofGeorgiaSaltMarsh 21
Figure4.A^orfui/))<;as/uofriomu(MuUermGrube,1871).AdultspecimenfromStationl,Sapelolsland,Georgia,November1971,
showinganteriorandposteriorendsofIbebody. DrawnIVomlifewithIbeaidofacameralucida.
lafi.withtwodarkbiowiLStrongchidnousjaws(Figures).Jaws dark brownoralmostblack, Notopodianormally reduced,
ooncave,almosispoon-shaped,inlivinganimalsvisiblethrough withoutsetaeexceptforanoccasional,slenderheterogomph
thefirst2-3setigers;medianedgeofeachjawwitharowofteeth. spiniger. Dorsalcirrianteriorly slenderandsmall,conically
Thelenninaltooth,somewhatseparatedfromtherowofteeth, sh2y)ed;postcriody long, flattened leaflike in structure with
slightlylargerthantherest EachjawwithFinegrowthrings. constrictedterminaltipsandavery'richsupplyoffinec^illary
Parapodiasub>biramoiiswithnoto*andneuiopodialaciculae. vessels. Ventralcirrismallthroughout.

AberrantNereididPolychaeteofGeorgiaSaltMarsh 23
Matureindividuals wilh 11 to21 neuroselaein each ofrotten pine trunks andbranchesin orabove the ditch
fascicle;neurosctaeoftwotypes: hctciogomphfalcigers, water. Heard(1982)alsonotedthepresenceofN.abiuma
numbering maximally 9 per fascicle, and heterogomph inMississippi livingundernearly semi-terrestrial condi-
spinigers with up to 12per fascicle (Figure 5). Highest tions.
numberofeachsctaltypeperfasciclefoundinthefirstthird Except during the period from November 1971 to
ofthebody,declininginnumberposteriorly. Anybundle March1972.N.abiumawasnotobservedanywhereinthe
ofsetaewiihdominanccofspinigers.Heterogomphfalcigers ditches,noteventhemudbottom. AHspecimensrecorded
withbladesfinelydenticulated,sometimesatbaseonJyand hadgutsfilledwithwoodpieces(Figures7-8)andtheinside
ofvaryinglengths(Figure5B-C). Heterogomphspinigers ofthesurroundingbarkhaddistinctmarksmadebythejaws
withlong,finelydenticulatebladetaperingintohairliketip. oftheworms.N.abiumalivesfreelyunderthebaikandhas
Bothfalcigersandspinigerswilhdensestructureoftrans- nopermanenttubes;thewormscrawledawayquicklywhen
verselamellaeincoteofshafi,mostdistinctin falcigers. barkwasremovedfromthebranches. Insomecases,they
Thedorsal,longitudinalvesselhasaslightlymeandcr- couldlivesemi-terrestriallyinthewoodpiecessinceparts
ingcourseinthefirstfewsegments,withmeandersincreas- ofthebranchesprotrudedfreelyintheatmosphere. The
ing in amplitude considerably toward the posterior end wormprovedtobeaveryfastswimmerwhenreleasedfrom
(Figure4)(normallystraightinncieidids(Lindroth,1938; thewood. Itseemslikelythat thewonnsunderthebark
Nicoll,1954).Ihecapillarysupplyisextracmhiiaiilyiichinche wereforaging,perhapspriortoreproduction. AHworms
dorsalpartoftheposteriorsegmentsandiniheleaflike,flattoied taken in November were large, mature individuals with
dorsalcirri.Freshdissectionandsectioningofadultworms smaUeggsintheirsegments. Thespringspecimenswere
from SapeloIsland has shownthat each segment in the smallerandwithoutsexualproducts.
worm body haspulsating“gillhearts”composed oftwo Earlieraccounts(Heard, 1982)haveestablishedthat
contractilechambers(Figure Fcuertxrm(1931)hasde- N.abiumaisabletosurviveunderveryextremeenviron-
scribedsuchheartsinNamalycastisranaaensisiotherwise, mental conditions. At very low oxygen tensions, the
theyarcrarelyreportedinnereididwonns(Nicoll, 1954). posteriorendoftheworm,wilhitsfoliaceouscirririchin
capillaryvessels,isseenextendedfromholesinthebark
BiologicalObservations and waving freely in the surrounding water (aquarium
observations.SapeloIsland). Thiswasalsoobservedby
N,abiumawasrecordedfromearlyNovember1971to Feuerbom (1931, p. 650) for Lycastis (Namalycastis)
January 1972 and February-March 1976, with greatest ranauensisandpersonallylotbJereissuccineafromSapelo
abundanceinfallandwinter. Itwasfoundunderthebark Island(seebelow).
Figure6. (MullerInGrube,1971).Schematicdiagramofthevascularsystemshowingthemainsegmental
vessels.CIV,drcum-intesllnalvessel;DC,dorsalcirrus;DLV,dorsallongitudinalvessel;G,gut;GH,gillheart;VLV*ventral
longitudinalvessel; VNC,ventralnervecord.
24 Rasmussen
Figure?.Namalycastisabiiuna,SapeloIsland,Georgia,November1971,Station1.Middlesectionofadult,preservedspecimen
withwoodandbarkpiecesinthegut
Littleisknownabout thereproductionand develop- foundthespeciestobehermaphroditicwithrelativelysmall
mentofN.abiuma. Onlysmalleggcellswereobservedin eggs» 125-135 p in diameterand laid in acommonjelly
thecoelominthematerialfroinSapeloIsland(November mass. Afteraboutfourdaysthelarvae,about300plong,
1971),anddevelopmentaldetailswerenotobtained. The hatched into what Feuerborndescribed and figuredas a
onlymoreextensivebreedinginformationforamemberof ciliatedneciochaetestage withthreesetigersand clearly
theNamalycastisgroupisgivenbyFeuerbom(1931,Figure biramousparapodia. Thesubsequentfateofthelarvaewas
10)ioxLycastis{Namalycasns)ranauensisfromJava. He notdescribed. Becauseofitsfreshwaterhabitat,itseems
AberrantNereididPolychaeteofGeorgiaSaltMarsh 25
I—.
I i I
3mm
Figures,Namalycastisabiuma, SapeloIsland,Georgia,November1971. Fecalpelletsfromadultspecimenwithremnantsof
barkandwoodparticles.
veryunlikelythatN.abiuwahasarrcc-swimmingpelagicstage. POLYCHAETA
Only Heard (1982), who kept individualsofN. abiurm in ANereis(Neanthes)succinea(FreyandLeuckari, 1847).
aquaria,mentionedlargeeggswithdirectdevclopmeniasthe Verycommonatallexaminedplaces,bothin1971-72
mostlikelyformofpropagationofthespecies,butgaveno and1976, Oftenlargespecimens;maximumlengthof
furthermformaiioa Otherwise,therearevirtuallynodetailsof living animal 170 mm. It burrows underbaik and
filepropagationofotherNamafyatstisspecies. seemstofeedondecayingwood. Theanimalswere
surroundedbybrownishexcrementmasses,undoubt-
FaunalAssodations edlyoriginatingfromdevouredwoodremnants. Indi-
vidualsfromMarch24,1976werealmostsexuallyripe
Thesurveybelowcomprisesbenfliicspecieslivingassoci- and in the heteronereid stage. Under low oxygen
atedwithNamalycastisabiumaonorunderthebarkofdeadand tensionscombinedwithhighwatertemperatures,the
windfallcnbranchesmostlyofpinetrees,predominantly the posieriorendoftheworm,withitsmanyligulesrichin
loblollypine,PimislaedaL„lyinginthebrackishwaiterof capillaryvessels,wasseene^ttendedaiRlwavingfreely
S^qieloIslandditches. in the water (laboratory observations). In case of
extremelowoxygenconditions,thespeciesmayleave
Aindicatespresenceunderbarkandinwood thewateraiMilivepartlyamphibiousunderthebarkof
Aindicatespresenceonsurfaceofbranches branchesexposedtotheair.
26 Rasmussen
AStettoninereismartiniWescnbcrg-Lund, 1958 ^ACassidinideaovalts(Say, 1818)=C. lunifrons
Thistinyaberrantnereidspecies isanotherremark- (Richardson, 1900)
ablememberofthedecayingwoodbiotopeofthetidal Inquantityunderbark. FrombothStation 1 andthe
ditchesofSapelo IslandL It was found bothduring BellMarshditchsystem,whereafewindividualswere
1971-72 and in March-April 1976, frequently in observed crawlingcmbranches. Femaleswitheggs,
groupsofuptosixindividuaLsatatimeandalwaysin March28, 1976.
grooves under the bark. AU specimens weretaken ASphaeromaterebransBate, 1866=S,destructor
only in the spring in different parts ofthe ditches. Richardson, 1897
Livingindividualsmeasured7-12mm.Oneripemale Inquantityunderbarkandinshipworm-boredbranches
specimen was collected on April 16, 1976. The inallditchesexamined.
morphologyandsystematiccharactersoftheexam- ^AGammerusdaiberiBousfleld, 1969
inedspecimensagreewiththedescription givenby Adultspecimensnumerousonandundertheparkof
Petdbone, 1971. pine branches, al.so in wood bored by shipworms,
TTicspeciesoccursmainlyintropical-subtropical salinity87oq. Femaleswitheggs,March28, 1976.
America.Sincefirstdescribedin1958byWesenberg- ThisAmericanendemicspeciesisrathernewlyde-
LundfromSt.MartinintheWestIndies,ithasbeen scribedbyBousfleld(1969).IthasarestricteddLstribution
recordedfrom theeasternandnorthwesternparts of inestuarinesystemsfromtheDelawareandChesapeake
theGulfofMexicoand from NorthCarolina. It is BayrcgKXissouthtoSouihCarolinaAocordingtoBousfield,
known from open waterand tidalponds with great themostdensepopulationsarcatsalinitiesofl-57i»andin
fluctuations in salinity (St. Marlin) and penetrates mid-watertonearbottomdepths. Itmaybefoundat
intoenvironmentscharacterizedby widelyfluctuat- 15®Aw salinity, then largely pelagic: and devek^ent
ingconditions: warmmineralsprings(Florida),salt withinoneyear. OvigenousfemalesoccurfromMarchto
marshes (Texas and Mississippi)^ Spariina marsh October. ItsoccmienceonSapeloIslandseemstobethe
(North Carolina), and on silt and muddy substrate mostsouthernonrecoid.
with litUeornooxygen(Hartman, 1958; Petlibone, AAMelitanitidaSmith, 1873
1971; Williams et al., 1976; Gardiner and Wilson, Adultspecimens(bothsexes)commonunderpinetree
1977;Heard, 1982). barkatStation1,November1971andJanuary 1972.In
^Poiydora fign/Webster, 1879 March 1976onandinrottenranches.
Uneesmallerspecimensinmudtubesunderpinetiecbaik. A Uhlorchestiauhleri(Shoemaker, 1936)
AHobsoniaflorida(Hartman, 1951) Often in numbers, crawling on submerged parts of
Asingle,ca. 12mmlongspecimeninmudtubeunder branchesclosetothewatersurface.
bark,BeUMarshditchsystem(Station10),March28, APanopeusherbsiiH.Milne-Edwards,1834
1976,salinity8.Thesystematiccharactersagreewith Twoyoungfemales,carapacewidth12and 13mm,in
thedescriptionbyBanse, 1979. emptyshipwomitubes.
AEuryiiumlimosum(Say, 1818)
CRUSTACEA Twomales,carapacewidth5.5mm,underbark,Sta-
ABalanuseburneusGould, 1841 tion 1,January20, 1972.
Fairly common, especially on the undersides ofthe ASesartnareticulatum(Say, 1817)
branches; maximum basic diameter25 mm. Newly Onefemale,carapacewidth7mm,underbark,Station
settled individuals present on March28, 1976in the 1,January20, 1^2.
BellMarshditchsystem. ASesarmacinereum(Bose, 1801or 1802)
ABalanusimprovisusDarwin, 1854 Common under bark,carapace width 2.5 to 16nim,
Common,predominantlyontheshelteredsidesofthe Station1,1971-72and 1976,
branches. On November 11, 1979,numeroussmall,
newly-seiilcdspecimenspresent,lessthan1mmacross. INSECTA
On April 23, 1976, pelagic larvae in abundance at AChironomkllarvae,blood-redspecies,afew*mmudtubes
Station 1. underbark.
AHargeriarapax(Harger, 1879)=Leptocheliarapax AOdonata,unidentifiedspecies,asinglelarvaunderbark;
Harger, 1879 November11, 1971 at20“/®salinity.
mm
1 female with eggs, 3.5 long, under bark, Bell
Marshdiichsystem,March28, 1976. MOLLUSCA
ACyaihurapolitaStimpson,1855 AAMelampusbidenlamSay, 1822
Singlespecimenunderbark.BellMarshditchsystem, A few small specimens under bark in water; also
March28, 1976. observedcrawlingonsubmergedpartsofthebranches.