Freshwater bryozoans in La Gamba (Costa Rica: Piedras Blancas National Park): a general introduction

2008·19.9 MB·English

by  Wöss, Emmy R

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Freshwater bryozoans in La Gamba (Costa Rica:
Piedras Blancas National Park): a general introduction
Briozoos de agua dulce en La Gamba (Costa Rica: Parque
Nacional Piedras Blancas): una introducción
Emmy R. WÖSS
Abstract:Despitetheircommonoccurrenceandpotentialecologicalandeconomicimpacts,freshwaterbryozoanshavereceived
verylittleattentioninscienctificresearch.These“mossanimals”comprisearelativelysmallgroup,with88species,andarewide-
lydistributedinponds,lakes,streamsandrivers.Theymostlybelongtotheclassofphylactolaemates,whichoccurexclusivelyin
freshwater,whileafewspeciescanbeassignedtoapredominantlymarineclass,thegymnolaemates.Freshwaterbryozoansare
sedentary,filter-feeding,colonialanimalswithcomplexlifecycles.Theyexhibitavarietyofasexualmeansofpropagation,which
isuniqueamongfreshwaterinvertebrates.Inadditiontofragmentationandfission,reproductionanddispersaltakesplaceviarest-
ingstagessuchasstatoblasts,inthecaseofphylactolaemates,andhibernaculaeinthecaseofgymnolaemates.Freshwatermoss
animalsarepresentonallcontinentsexceptAntarctica,butmostbryozoologicalresearchhasbeenconductedintemperatezones.
Thefreshwatertropicsarelargelyunexplored,particularlytheNeotropics.Thispilotstudyonbryozoanoccurrenceandspecies
diversitytakesplaceinLaGamba(CostaRica:PiedrasBlancasNationalPark)andrepresents,togetherwithasurveyonphylac-
tolaematebryozoansoftheGuanacasteConservationArea,thefirstinvestigationofthisanimalgroupinCentralAmerica.
Keywords:freshwaterbryozoans,generalcharacteristics,zoogeography,Plumatellidae,LaGamba,CostaRica.
Resumen:Apesardesufrecuenciaydesupotencialecológicoeimpactoeconómico,losbriozoosdeaguadulcehanrecibidomuy
pocaatenciónenlainvestigacióncientífica.Losanimalesmusgoincluyenaungruporelativamentepequeñode88especiesyse
encuentranampliamentedistribuídosenestanques,lagunas,arroyosyríos.LamayoríapertenecealaClasePhylactolaemata,que
seencuentraexclusivamenteenaguadulceysólounaspocasespeciespuedenserasignadasalaClaseGymnolaematapredomi-
nantementemarina.Losbriozoosdeaguadulcesonsedentarios,filtradores,animalescolonialesconcomplejosciclosdevida.Ellos
exhibenunavariedaddeformasdepropagaciónasexualquesonúnicasentrelosinvertebradosdeaguadulce.Ademasdelafrag-
mentaciónyfisión,lareproducciónydispersiónocurreatravésdeestadosderesistencia,comolosestatoblastosenelcasode
PhylactolaemataehibernáculosenelcasodeGymnolaemata.Losanimalesmusgodeaguadulceseencuentranpresentesento-
dosloscontinentes,exceptoenlaAntártica,sinembargolamayoríadelasinvestigacionesbriozoológicassehanllevadoacabo
enzonastempladas.Elaguadulcedelostrópicossonáreasnoexploradas,enparticularlosneotrópicos.Esteestudiopilotosobre
lapresenciadebriozoosydiversidaddeespeciessellevoacaboenLaGamba(CostaRica:ParqueNacionalPiedrasBlancas)y
representajuntoconunainvestigacióndelosbriozoosPhylactolaematadeláreadeConservaciónGuanacaste,laprimerainves-
tigaciónsobreestegrupodeanimalesenAméricaCentral.
Palabrasclave:briozoosdeaguadulce,característicasgenerales,zoogeografía,Plumatellidae,LaGamba,CostaRica.
Introduction can dominate epibenthic and litoral communities in
biomass(RADDUM&JOHNSON1983).
Freshwaterbryozoansormossanimalscanbecom-
monlyfoundinabroadrangeoflenticandloticbodies Intotal,theinvertebratephylumBryozoacompris-
ofwater,buttheyarelessfamiliar,oftenoverlookedand esmorethan8.000extant,mostlymarinespecies(RY-
neglected in most limnological studies and faunal sur- LAND 2005), a number that is far exceeded by 16.000
veys.Inmanyregionsoftheworldtheyareoneofthe fossil taxa. As the great majority of marine bryozoan
most poorly known faunal groups (RICCIARDI & colonies possess calcareous skeletons they are easily Stapfia88,
REISWIG1993).Theyare,however,amongthemostim- preserved and are among the commonest macrofossils zugleichKatalogeder
oberösterreichischen
portantsuspension-feedinganimals,alongwithsponges from the Lower Ordovician onward. In contrast, the Landesmuseen
NeueSerie80(2008):
andmussels(WOOD2006).Freshwaterbryozoanseven colonies of soft-bodied freshwater bryozoans have left 485-494
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Fig.1:Firstdepiction nofossilrecord,butthechitinousrestingstagesmanu-
ofabryozoan factured for overwintering and dispersal are very occa-
(RONDELET1558):
sionallyfoundinthefossilrecordasfarbackasthePer-
“girofladedemer”,
representinga mian(TAYLOR2005).
reteporidtaxa.
The first descriptions of bryozoans can be dated
backtotheyear1558whereRONDELETpresentedinhis
“L’Histoire entière des poisons” a figure of marine bry-
ozoan,presumablyareteporidtaxa,callingit“giroflade
demer”(Fig.1).WhileRondeletcorrectlyclassifiedthe
organisms as animals, until the mid 18th century many
authors interpreted bryozoan colonies, like corals and
hydroids,asplants.Tentaclesofaprotrudedpolypidsof
Alcyonariaweredescribedaseightpetalsofaflowerand
encrusting sheets of calcareous bryozoan colonies were
assigned to be a “stony plant”. Generally this remains
Fig.2:Firstfreshwater
bryozoantobedescribed: reflectedbothinthenameofthephylum,whichtrans-
Lophopuscrystallinus(PALLAS lates as “moss animals” and in the term “zoophyte”
1786)or“bellfloweranimal”
whichwasusedbyLINNAEUS(1758)toembracedboth
(fromALLMAN1856).
bryozoansandhydroids(RYLAND2005).Thefirstfresh-
waterbryozoantobedescribedwasLophopuscrystallinus
byPALLASin1768,butitisbelievedthatTrembley’sde-
pictionofa“polypàpanache”(Fig.2)alsodisplaysthat
species.Thename“bellfloweranimal”referstoitsfan-
shaped colonial structure. The transparent sac-like
coloniespossessthelargestzooidsofallbryozoanspecies
reachingabout5mminsize(Fig.3).
The modern classification of bryozoans began in
1837whentheclassesPhylactolaemataandGymnolae-
matawereestablished,followedlateronbyathirdclass,
theStenolaemata.
The Phylactolaemata exclusively occur in freshwa-
ter while a few species of the predominantly marine
group Gymnolaemata can be found in brackish water
and freshwater environments as well. VINOGRADOV
(2004)establishedthelatestrevisionoffreshwaterbry-
ozoansystematicswhichisstillintheprocessofgener-
alacceptance.
Morphological and
ecological characteristics
Bryozoans are sedentary, colonial animals, with
colony sizes ranging from less than one millimetre in
height, as in the marine genus Monobryozoan which
consists of little more than a single feeding zooid
(RYLAND 2005), to giant colony growth forms of up to
2.5mlengthand0.5indiametersuchasinthefreshwa-
terspeciesPectinatellamagnifica(Fig.4).
In the bryozoan phylum, the texture of colonies
variesfromstronglycalcifiedtogelatinous.Coloniesof
freshwater bryozoan taxa are classified into the plu-
Fig.3:Lophopuscrystallinus:sac-likecolonywithprotrudingzooids. matellidandthelophopodidtype(Fig.5a,b).Theplu-
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matellid type is assigned to colonies with chitinised
tubes which are relatively stiff and durable. It allows
colonies to ramify over the substrate with sometimes
erect branches or in a bushy shape. Large massive
growthformsreachcoveragesmetreslongonsubmerged
trunks and rocks or make colonies the size of a human
head,weighingmorethan1kg(WÖSS2005a).Colonies
ofthelophopodidtypearegelatinous,softandtranspar-
ent.Theyremaineithersmall,resemblingeggmassesof
molluscs,ortheycanalsoaggregatetohugegelatinous
bodies.
Allplumatellidsarestrictlysessile.However,within
thelophopodidtypeacertainmotilitycanbeobserved
insomespeciese.g.incoloniesofsmall,lobular(Lopho-
puscrystallinus)orvermiformshape(Cristatellamucedo).
Eachcolonyconsistsofgeneticallyidenticalmodu-
lar units, known as zooids. In contrasts to marine Fig.4:Pectinatellamagnifica:colonygrowthinmassivegelatinousform.
species, zooids of freshwater bryozoans are monomor-
phic and each is provided with its own independent terinvertebrates.Duetotheinstabilityofmostfreshwa-
feeding, digestive, muscular, nervous and reproductive terenvironments,theoccurrenceofcoloniesislimited
system.Theinternallivingpartsofthezooidconstitute toacertainperiodoftheyear,e.g.coloniesdonotover-
the moveable polypid while the surrounding walls and
winter in temperate zones or they suffer from desicca-
theirassociatedtissues,thecystid,functionsasaprotec-
tioninzoneswithdryseasonsorhighwaterlevelfluc-
tivehousing.
tuations. Asexual propagation units are developed and
Theanteriorpartofthepolypidisthemostconspic- constitute an obligatory component in freshwater bry-
uous part of a bryozoan; a tentacular crown or lopho- ozoanlifecycles.Thisisnecessary,asthesexualpropag-
phore,whichinthecaseofthephylactolaematesispre- ule, the larva, is highly vulnerable and can only exist
dominantly horseshoe-shaped, carries up to 120 tenta- and be dispersed during a short period (WÖSS 2002).
cles. Bryozoans are active filter-feeders. The tentacles Asexual reproduction can take place by fragmentation
createacurrentofwaterthatbringssuspendedparticles, andfissionofcoloniesand,mostimportantly,bythefor-
includinglivinganddeadorganicmaterialaswellasin- mation of resting stages. These dormant bodies consist
organic silt, towards the mouth. Freshwater bryozoans
of chitinised shells protecting the germinal mass and
contribute significantly to the recycling of nutrients in
yolkcells.Inthecaseofthephylactolaemates,theyare
smalllentichabitats(JOB1976,SØRENSENetal.1986). categorisedasstatoblastswhilegymnolaematesformhi-
Reproductionanddispersalishighlycomplexandis bernaculae. One group of statoblasts, the floatoblasts
basedonavarietyofpropagulesuniqueamongfreshwa- (Fig. 6a), drift on the water surface with the help of a
a b
Fig5:Classificationofcoloniesinfreshwaterbryozoans.(a)plumatellidtype(FredericellasultanaintermingledwithPaludicella
articulata),(b)lophopodidtype(Cristatellamucedo).
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Species diversity and
zoogeographical distribution
Freshwater bryozoans occur in a broad range of
freshwaterhabitats,suchasponds,lakes,riversandes-
tuaries.Coloniesareattachedtosubmergedsurfacesor
theundersideoffloatingobjectssuchasaquaticplants,
wood and rocks or a wide range of other materials
broughtinartificially,suchasplastic,glass,rubbertyres
oraluminium.
Despitethesmallnumberofdescribedspecies(88),
freshwaterbryozoansarefoundonallcontinentsexcept
Antarctica. They have been described in a range from
75°NinlakesclosetoSpitzbergento55°SinTierradel
Fuego.Atotalof43speciesareconfinedtoonezoogeo-
a graphical region and 22 of these 43 species are known
onlyfromaveryrestrictedarea,suchasoneortwosites
(MASSARD&GEIMER2008).Theproportionofendem-
icspeciesisspecifiedwith45%(WOOD2002).
The taxonomy of Phylactolaemate bryozoans has
advancedconsiderablythroughtheexaminationofsta-
toblastsbyscanningelectronmicroscopy.Sincethefirst
discussion on zoogeography of freshwater bryozoans by
BUSHNELL(1968,1973),thenumberofspecieshasmore
thandoubled.Inthetaxonomicallymostdifficultgroup
–Plumatellidaewhichcomprisesabout78%ofthephy-
lactolaemates–speciesdiscriminationisrepeatedlyun-
derrevision.SEMinvestigationsinthegenusPlumatel-
la, for example, has resulted in an increase of 25% in
species number over the last two decades. Consequen-
tially,thecosmopolitanstatusofPlumatellarepens,Plu-
matella emarginata and Fredricella sultana has had to be
reconsideredasformerrecordsofthesespeciesmaycor-
respondnowtoother,newly-describedspecies.Atpres-
b
ent,onlyPlumatellacasmianaisthoughttobecosmopol-
Fig.6:StatoblastsofPlumatellidae(Phylactolaemata).(a)floatoblasts,(b) itan,althoughitisnotyetreportedfromSouthAmeri-
sessoblasts. caandAustralia(MASSARD&GEIMER2008).
gas-filledannulusthatfacilitatesdispersalandcolonisa- While progress is made in surveying bryozoans in
tionofnewsubstrates.Theycanbedisseminatedbymi- temperate regions, mainly in Europe and Northern
gratorywaterfowloverlongdistances,asdataonpopu- America,therearestilllargegapsintheirinventoriesin
lation genetics from northern European bryozoans re- Africa, South America, Central America, Africa and
veal(FREELANDetal.2000). some parts of Asia. The patterns of disjunct distribu-
tions of many species are highly doubtful due to the
Thesecondgroupconsistsofsessoblastsandpipto-
scarcity of available data. Some of these distribution
blasts, which both lack – as do the hibernaculae – the
patternscanpossiblybeinterpretedbydispersalviami-
capabilitytofloat.Hibernaculaeandsessoblastsareusu-
gratingwaterfowl,suchasthenarrow,intercontinental
allyfixedtothesubstrate,withaspecialattachmentap-
rangeofseveralspecies.Inothercases,thedispersalpat-
paratuslocatedononesideoftheshellinthecaseofthe terns might suggest human activities as a major con-
sessoblasts(Fig.6b).Thus,theserestingstagespromote tributingfactor(WOOD2002).
thelocalpersistenceofthebryozoan(KARLSON1994).
The freshwater tropics are largely unexplored, and
particularly in the Neotropics, only a few surveys on
bryozoans in larger geographical areas have ever been
conducted: in Brazil (WIEBACH 1967, 1970a, b, 1974,
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BONETTO & CORDIVIOLA 1965, MARCUS 1941, 1942),
Argentina (CAZZANIGA 1989) and Costa Rica (ROUSH
1998). The number of Central American freshwater
bryozoan species is currently reckoned at six Phylacto-
laemata and four Gymnolaemata (WOOD http://bryo
technologies.com/pages/world%20list.com),withoutin-
cludingtheCostaRicanresults.Despitethepaucityof
dataonspecies,theconclusionismadethatfreshwater
bryozoanshaverelativelysmallgeographicdistributions
intropicalregions(WOOD2002).
Central America: Panama Canal,
Guanacaste Conservation Area and
La Gamba
PanamaCanal
Inthe1990sAsajirellagelatinosa(Fig.7),alophopo-
did species known previously only from eastern Asia,
was recorded twice in the area of the Panama Canal Fig.7:Asajirellagelatinosa:floatoblast(spinoblast).
system (WOOD & OKAMURA 1999). In April 1992,
colonieswerecollectedonleavesandstemsofHydrilla
browni is already known from Guatemala and also oc-
verticillatainthebroadreachesofthelowerRíoChagres
curs in North and South America (ROUSH 1998).
asitentersLakeGatun.TheLakeisthe230km2heart
Species occurrence was exclusively restricted to eight
of the Panama Canal system, created in the 1890s
shallow,seasonalstreamsandpondswithPOCof570-
by damming the Río Chagres. In a subsequent collec-
4.300mgcm-3.Fourspeciesoccurredinseasonalstreams
tion in February 1998, large colonies were found up-
(RioCuajiniquil,QuebradaelDuende,QuebradaCosta
streamofthefirstsiteonstumpsandreedsintheshal-
Rica) originating in dry tropical forest and desiccating
low water of the Lago Alajuela impoundment
fivetosixmonthsoftheyear.Sixspecieswerefoundin
(9°14.74’N, 79°35.62’W). Sporadically abundant but
seasonallentichabitats,suchasinartificialponds(dry
never common, A. gelatinosa has been reported from
forestaswellasrainforest),innaturalseasonalmarshes
Japan, Korea, Taiwan, Burma, India, Ceylon and In-
(dry forest) and in a small natural depression (primary
donesia.Humantransportofstatoblastsisalikelycause
moist/dry transistion forest). The permanent streams
of the disjunct distribution of this species as it might
originatedincloudandrainforestsandcontainedlarge
havebeenintroducedbyshippingtrafficwiththecom-
volumesoffastflowingwaterandwerecharacterisedby
pletionofthePanamacanalinearly1900.
POV<560mgcm-3.Theyallcontainednobryozoans.
The nine species found in the seasonal streams and
GuanacasteConservationArea
pondsshowedverylittleoverlapindistributionandall
SurveysoffreshwaterbryozoansinCostaRicastart-
butthreespecieswererestrictedtoasinglesite.
edin1996/1997intheGuanacasteConservationArea
innorth-westernCostaRica(ROUSH1998).TheCon- LaGamba
servation Area occupies 110.000 hectares in the Gua-
Sitesandmethods
nacasteprovinceandisdesignedtoprotecttheendan-
gered dry tropical forest biome. In this area, seventeen Thispilotstudyonbryozoansstudywascarriedout
aquatic habitats representing tropical dry forest, cloud from 28 January 2007 to 1 February 2007 in the sur-
forest and Atlantic rainforest were investigated in the roundingareaoftheResearchStationLaGamba(UTM
course of three field trips. In total, nine phylactolae- 962502 N and 257756 E). As the Golfo Dulce region
mates could be recorded: Fredericella browni (ROGICK belongs to the most humid areas in Costa Rica, sam-
1945, Fredericellidae) and eight species of the family pling in the dry season (December-April) guaranteed
Plumatellidae,sevenofthegenusPlumatellaandoneof easier access to the water. In total, eight sites were in-
Hyalinella. Based mainly on statoblast morphology, the vestigated in search for bryozoans colonies or stato-
eight Plumatellidae were all diagnosed as new species. blasts. Aquatic plants, submerged wood and smaller
Thedetaileddescriptionofthenewspecieswillappear rockswerepulledoutwiththehelpofaraketoanalyse
inaseparatepublicationshortly(Wood,pers.com.).F. the aufwuchs for possible colony growth or sessoblasts
489
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a b
c d
Fig.8:LaGamba,siteswithfreshwaterbryozoanoccurrence.(a)“caimanpond”,(b)“oldstationpond”,(c)“forestpond”,(d)“tilapia
pond”.
fixed to the substrate. Surface water was filtered and river bed of the Río Quebrada la Gamba had partially
drifting detritus was sampled with a net in search for fallen dry with several basins nearly isolated. Water
floatoblasts. Environmental parameters such as water temperature ranged from 27.8°C to 30°C, pH was 6.4-
temperature, pH and conductivity were measured with 7.4 and conductivity was 70-137 μS. Evidence for bry-
EutechInstrumentspockettesters. ozoanpresencewasprovidedinthefollowingfoursites,
allofthemstagnantwaterbodies.
Resultsanddiscussion
Site1:“caimanpond”,situatedontheroadbetween
Fiveofthe8bodiesofwater(Table1)canbechar-
Research Station La Gamba and Esquinas Rainforest
acterisedasstagnant(“ponds”),thetwostreamsandthe
Lodge(Fig.8a).
river showed slow to intermediate current. The wide
Colonies:submergedbranch(ø2.5cm)withsever-
al young colonies. Colonies growing in “runners”
Table1:BryozoansurveyinLaGamba(28.1.-1.2.2007):studysitesand
(WÖSS 1996), cystid texture hyaline to weakly chi-
bryozoanoccurrence.
tinised.Allzooidsattachedtothesubstrate,onecolony
number withabout30extrudedzooids,tentacles45-56anddel-
of
icate.Floatoblastswereinformationandripenedinthe
date site bryozoans species
largestcolonytobesuccessfullyrearedforaweakinthe
28.1.,30.1. 1pond “caimanpond” colonies,statoblasts 4
laboratory. Statoblasts: high number of floatoblasts
29.1. 2pond “oldstationpond” colonies,statoblasts 3
1.2. 3pond “forestpond” colonies,statoblasts 1 driftingclosetotheshore.Floatoblastsoffourdifferent
1.2. 4pond “tilapiapond” colony 1 Plumatella species: two types of floatoblasts of broad
28.1.,30.1. 5pond “swimmingpond” —- ovalshape(similaritieswithEuropeanP.repens, P.ru-
29.1. 6stream riverbedtrail —- gosa),twotypesfloatoblastsoflongovalshape(similar-
1.2. 7stream “foreststream” —- ities with European P. emarginata, Asian P. bombayen-
31.1. 8river RíoQuebradalaGamba —- sis).
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Site 2: “old station pond”, situated within the area
of the former research station and present guest house
(Fig.8b).
Colonies:floatingbranch(ø1cm)withseveralvery
smallcolonies.Colonygrowthdenseandfullyadherent
tothesubstrate,cystidtransparent.Tentacleslong,del-
icateandmostly50innumber;colonytubeswithsmall
elongate floatoblasts (a few similarities with European
P.casmiana).
Statoblasts: floatoblasts sticking on a floating
branch (ø 1.8 cm) and drifting on the water surface:
three different Plumatella species (floatoblasts broad
oval,Fig.9,longovalandsmallelongate)
Site3:“forestpond”,easternpartofthefloodplain
area of the Rio Quebrada la bolsa: a depression within
theforest,north-eastofSeñorMundo’sfinca(Fig.8c)
Colonies:severalcoloniesonfewthickbranches(ø
4 cm). Colonies fully adherent to the substrate, cystid
Fig.9:Plumatellasp.(“oldstationpond”):floatoblast,thetwovalves
chitinisedwithlongoval,maturefloatoblastsinside. separatedaftertreatmentwithKOH.
Site4:“tilapiapond”,easternpartofthefloodplain
area of the Rio Quebrada la bolsa: a depression at the
tofivespecieswillbedocumentedbyfloatoblasts.Ses-
edgeoftheforest,southofSeñorMundo’sfinca(Fig.8d)
soblasts were very rare; WOOD (2000) mentions that
Colonies: one very small colony on a plant stem, sessoblasts are unknown in a number of plumatellid
withstatoblastsinformation,presumablysessoblasts. phylactolaemates and refers to 70% of all neotropical
species.Bycontrast,sessoblastsdooccurin91%ofplu-
The fifth stagnant water body, the “swimming
matellidholarcticspeciesandinallofthosefromAus-
pond”, is situated within the garden of the present re-
search station. The rich aquatic vegetation would pro- tralia. However, material from the tropics is extremely
vide enough substrate for littoral aufwuchs communi- Fig.10:Prolific
ties,butbryozoansareabsent.Thismaybeexplainedby growthofplumatellid
coloniesonartificial
the young age of the pond; it was created in 2002, in
substrates.
contrasttothe“caimanpond”whichhasbeeninexis-
tencesince1994(Weissenhofer,pers.com.).
It can be assumed that water bodies in the flood
plain area of the Rio Quebrada la bolsa are intercon-
nected during the rainy season. This may especially be
the case for the “forest pond” and the “forest stream”
and would affect the dispersal of resting stages and
colonyfragments.Furthermore,dispersalofstatoblasts–
often assigned to waterfowl – could also be accom-
plishedbycaimans.Thereptileswerehidinginemersed
vegetation or accumulations of detritus in all of the
stagnant water bodies except the “tilapia pond”. They
were even temporarily found in the “swimming pond”,
althoughtheywererepeatedlymovedfromthere.
Insummary,despitethepreliminarycharacterofthe
survey, the result is promising: freshwater bryozoans
seem to frequently colonise the ponds in immediate
vicinity of the research station La Gamba. Species di-
versitypersiteturnedouttobeevenhigherthanitwas
inGuanacasteintwoofthefoursites.InLaGamba,up
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they were absent in lotic water bodies is not unknown
fromstudiesinthetemperatezone,althoughfreshwater
bryozoansdooccurinstreamsandrivers.Ingeneral,the
structureofthehabitat,suchastheavailabilityofsuit-
able substrates which was greater in the ponds, play a
crucialroleforbryozoanpresenceandabsence.
It might turn out that all of the sampled species of
LaGambacouldnotbeclassifiedinexistingspecieslists
of Central America or from elsewhere. However, they
mightbealreadyrepresentedinthefindingsoftheGua-
nacaste area which are now in process. Therefore the
detailed description of the La Gamba material will be
synchronisedbycomparingSEMpicturesofstatoblasts
orbyexchangingmaterial.Besides,furthersamplingin
the La Gamba area would be advantageous to acquire
complete information (colonies and all kind of resting
stages)inthecaseofdescribingholotypesandtogetan
a insightintothelifehistoriesoffreshwaterbryozoansin
the tropics (colony versus statoblast occurrence in the
courseoftheyear).
Human related issues
“Inthewholeanimalkingdomtherearefewgroups
less frequently associated with the activities of men
than the Polyzoa” (ANNANDALE 1922, still using the
term Polyzoa for the phylum Bryozoa). The following
examples will outline the potential of bryozoans: caus-
ing damage as well as offering beneficial qualities – all
fromananthropocentricpointofview.
Biofouling
Mossanimalsareprobablythemostcommonamong
thefoulingorganisms.Beforethewidespreaduseofsand
b filtration, freshwater bryozoans were a frequent nui-
sanceinwatersupplysystemsoflargecitieslikeLondon
Fig.11:BryozoanfoulinginafishfarminDemmin,Germany:(a)coloniesof
and Hamburg where KRAEPELIN (1885) called them
Plumatellafungosa,(b)deadcolonytubeswithremainingfloatoblasts.
“Leitungsmoos”(pipelinemoss).Nowadays,economical
lossisnoteworthyastheyarestillresponsibleforblock-
sparse and further sampling might dispute the hy- ingconduitsorcloggingfiltersinwaterreservoirs,mu-
pothesysthatsessoblastsevolvedasoverwinteringstruc- nicipal water supplies, waste water treatment systems
turesmainlyintemperateregions. andirrigationsystems(SMITH2005,WOOD2005).The
rapidandwidespreadgrowthofattachedcolonies(Fig.
As in Guanacaste, no gelatinous species of the
10) reduces water exchange and fish growth in fish
lophopodidtypeweredetectedinLaGamba.Allfind-
ingscanbeassignedtothePlumatellidae,aresultthat farms(JONASSON1963,pers.obs.)andcausesoperating
resembles the study of ROUSH (1998). Additionally, problems in thermal and nuclear power stations
ROUSH emphasized that “bryozoans in the GCA prefer (APROSI1988).Forinstance,theChinonpowerstation
seasonalhabitatswithslowtonocurrentandhighPOC ontheRiverLoirehadtobeshutdownduetoprolific
content”whichalsoagreeswiththepresentresultsfrom bryozoansettlementinthecoolingcircuitswhichwere
La Gamba. Although nutrient content was not meas- supplied by river water. In addition, biofouling by bry-
ured during collecting in the ponds, a food chain from ozoans is persistent, since statoblasts and hibernaculae
phytoplanktontofishseemedtoprovideanoptimalen- are very resistant to physical and chemical treatment
vironmentforthepresenceofbryozoans.Thefactthat andcanactasseedbanks(Fig.11a,b).
492
© Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at
Prokiferatekidneydisease population of Bugula declined dramatically. Further-
more,investigationsrevealedthatabacterialsymbiont
A number of freshwater bryozoans are already
of Bugula, Endobugula sertula, was responsible for pro-
known to be the hosts of the myxozoan parasite Tetra-
ducingbryostatinandE.bugulacouldnotbecultivated.
capsuloidesbryosalmonae,thecausativeagentofthepro-
AsBugulasamplesfromothersitesdidnotcontainthe
liferate kidney disease (PKD, ANDERSON et.al. 1999).
identicalpharmaceuticalactivesubstance,thesituation
Proliferate kidney disease is a serious infection of wild
turned out to be critical until at the end of the 1990s,
andfarmedsalmonids,affectingmainlythekidneyand
bryostatin2,asyntheticformofbryostatin1,couldbe
spleenofthefishhosts.Theinfectioncausesthefishes’
produced. Currently, 15 variants of bryostatin are
immunecellstomultiplyoutofcontrol,destroyingthe
knownandprogressinmolecularbiologyfacilitateseco-
infectedorgansandresultinginanaemia,bloating,dis-
nomically efficient production of the anti-cancer drug
colouration and death. In intensive farming situations,
(WÖSS2005b).
entire stocks can be wiped out. Due to the great eco-
nomic losses to aquaculture industries, PKD has been
identified as one of the most economically important Acknowledgements
diseases affecting cultured salmonid fisheries (TOPS &
I want to thank the Sistema Nacional de Areas de
OKAMURA2005).
ConservacióndelMinisteriodelAmbienteyEnergiaof
AlthoughPKDwasrecognisedasaserioussalmonid CostaRicatopermitmyworkonbryozoansincourseof
fish disease in the early 20th century, the etiological the project “Biodiversida, ecología y desarrollo
agent remained unidentified until in the 1980s when sostenibledelaregiondelParqueNacionalPiedrasBlan-
evidence was provided that the parasite organism be- cas” (Resolución 001-2008-SINAC). The EU-SYN-
longs to a group known as Myxozoa. As the parasite THESYSgrantGB-TAF2074supportedmystayatthe
does not develop into its final form in fish, it was not NationalHistoryMuseuminLondontogaininsightin-
possibletoidentifyitfurtheruntil1999,whenidentical tonon-Europeanbryozoanmaterial.FurthermoreIwant
genetic material of this parasite was demonstrated in tothankProf.ManfredWalzlandMag.ThomasSchwa-
bryozoans as well as in rainbow trout, thus identifying haoftheDepartmentofTheoreticalBiologyattheUni-
bryozoansasthemysteryhostsharbouringtheinfective versityofViennaforsupportinmacro-photography.
stagesofthismyxozoan.TheparasitewasnamedTetra-
capsula bryosalmonae (later renamed to Tetracapsuloides References
bryosalmonae),reflectingthenamesofthebryozoanand
salmon hosts. The discovery has far-reaching implica- ALLMANG.T.(1856):Amonographofthefresh-waterPolyzoain-
cludingalltheknownspecies,bothBritishandforeign.—
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ANDERSONL.,CANNINGE.U.&B.OKAMURA(1999):Moleculardata
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