Taxonomy of Oncaeidae (Copepoda, Poecilostomatoidea) from the Red Sea. 2. Seven species of Oncaea s.str

60 Pages·2001·26.7 MB·

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Bull. nat. Hist. Mus. bond. (Zool.)67(I):25-84 Issued28June2001
Taxonomy of Oncaeidae (Copepoda,
Poecilostomatoida) from the Red Sea.
II. Seven species of Oncaea s.str.
RUTH BOTTGER-SCHNACK
InstitutfiirMeereskitndeander UniversitatKiel, DitsternbrookerWeg 20, D-24105 Kiel, Germany. E-mail
address: [email protected]
SYNOPSIS. SevenspeciesofOncaeidae(oneofwhichisnewtoscience)aredescribedfromtheRedSea.includingadescription
ofthehithertounknownmaleoiOncaeacleveiFriichtl.TheyallbelongtoOncaeasensustrictoasdefinedinaphylogeneticstudy
ofoncaeidspecies by Bottger-Schnackand Huys in 1998. Thegenus is defined by acombination ofcharacters includingthe
absenceofaconicalprocessonthedistalmarginoftheendopodofswimmingleg4.ornamentationofthelabrumandmandibular
bladeandsexualdimorphism inantennarysetaeandinendopodsofswimminglegs. Oncaeas.str.includestwosubgroups,the
wm/jta-subgroupandthec/evei-subgroup,femalesofwhichcanbeseparatedbytheabsenceorpresenceofadorso-posterior
projectionontheP2-bearingsomite.SpeciesofthevenustasubgroupintheRedSeaincludeO.venustaPhilippi.O.mediterranea
(Claus). O. mediaGiesbrecht. O. scottodicarloiHeron& Bradford-Grieveand O. waldemariBersano& Boxshall;theclevei-
subgroupconsistsofO.cleveiFriichtlandO.paracleveisp.nov.OncaeapraeclaraHumesisajuniorsubjectivesynonymofO.
venusta. O. philippinensis (Kazatchenko & Avdeev) as well as Oncaea sp. 1 and sp. 2 sensu Ferrari are regarded as species
inquirendae in Oncaea s.str.Thetypespeciesofthegenus. O. venusta. hastwoform variants, formatypicaandformavenella
Farran.whichcanbedistinguishedbydifferencesinsizeand inafew minormorphological characters.Theirspatio-temporal
distributiondiffersconsiderablyintheRedSea.whichmayindicatereproductiveisolation.Theworld-widerecordsofO.venusta
formsarereviewedanddiscussed.
CONTENTS
Introduction 25
Material and Methods 27
Genericdiagnosis 28
Descriptionofspecies 30
Oncaea venusta Philippi formatypicaFarran 31
O. venusta Philippi formavenella Farran 37
O. mediterranea(Claus) 53
O. mediaGiesbrecht 54
O. cleveiFriichtl 58
O. scottodicarloiHeron& Bradford-Grieve 65
O. waldemariBersano& Boxshall 70
O.paracleveisp. nov 78
Acknowledgements 82
References 82
INTRODUCTION et al.. 1985; Cowles et al, 1987; Bottger-Schnack, 1987) and
subsequentresearchtopicshavefocussedontheircommunitystruc-
ture and biology [see Bottger-Schnack (1999) for a review ofthe
Small copepod species ofthe family Oncaeidae are widely distrib- literature],therebyprovidingnewinsightsintothelargelyunknown
uted in marine pelagic areas, extending from the epipelagic zone ecological importance ofthis copepodgroup.
(e.g. Boxshall, 1977a; Dessier & Donguy, 1985; Cowles et al., Apart from ecological issues, the taxonomy ofoncaeid species
1987) to the deep-sea (Wishner, 1979; Humes, 1988) and from has been the subject ofincreasingly detailed studies over the past
tropical (Tsalkina, 1970; Deevey & Brooks, 1977) topolarregions two decades (e.g. Boxshall, 1977b; Heron, 1977; Malt, 1982a, b,
(Hopkins, 1985;Richter, 1994;Metz, 1995).Duetotheirsmallsize, 1983a,b,c,d;Heronetal., 1984;Krsinic&Malt, 1985;Boxshall&
oncaeidcopepodsareoftenneglectedorunderrepresentedinmarine Bottger, 1987; Krsinic, 1988; Bottger-Schnack & Boxshall, 1990;
plankton investigations, whichare usually conductedwithconven- Heron &Bradford-Grieve, 1995; Bottger-Schnack&Huys, 1997a,
tional netsof0.3 or0.5 mm mesh sizes. In recentyears, increasing b, in press; Itoh [in: Chihara & Murano (1997)]). Despite these
attention has been paid to the study of smaller mesozooplankton efforts, however, the taxonomy of many oncaeid species is still
organismssampledwithfinemeshnetsof0.1 mmmeshsizeorless. inadequate and particularly those species that are smaller than 0.5
In particular, small oncaeid copepods were sampled in high abun- mm have not been described in sufficient detail. Moreover, many
dancebythesenets(e.g.Bottger, 1982;Paffenhofer, 1983;Schnack oncaeid species are morphologically very similar, and thus can be
©TheNaturalHistoryMuseum.2001
26 R.BOTTGER-SCHNACK
distinguishedonlybyafewcharacters, including microstructureof area, including a thorough review ofthe taxonomic history ofthis
the mouthparts and on the exoskeleton, which require a level of allegedlycosmopolitanspecies(Bottger-Schnack&Huys. 1997).In
detail not generally adopted in most taxonomic descriptions. Such arecenttaxonomicstudy, 11 speciesofOncaeidaeweredescribedor
integumental microstructures have been used to differentiate bet- redescribedfromtheRedSea,whichbelongtotheconifera/similis-
weencloselyrelatedspeciesofcyclopoid(Uedaetal, 1996;Rocha, group as defined in the phylogenetic study of Bottger-Schnack &
1998) and oncaeid (Bottger-Schnack, 1999; Bottger-Schnack & Huys(1998).Anewgenus,Triconia,wasproposedtoaccommodate
Huys, in press) copepods. alloncaeidspeciesbelongingtothisgroup(Bottger-Schnack, 1999).
The phylogenetic relationships of the Oncaeidae are not well AspartofanongoingtaxonomicstudyofRedSeaOncaeidae,the
understood. The diphyletic status of the family has recently been presentpaperdescribessevenspecies,whichbelongtothevenusta-
recognized by Huys & Bottger-Schnack (1996/97), who proposed group as defined by Bottger-Schnack & Huys (1998). In their
the new family Lubbockiidae to accommodate Lubbockia Claus, cladogram of oncaeid species it is equivalent to species group 2.
1862 and related genera, retaining only Oncaea Philippi, 1843, Thiscore-groupincludesOncaea venustaPhilippi,thetypespecies
Conaea Giesbrecht, 1891 and Epicalymma Heron, 1977 in the ofthegenus,andisconsideredhereasOncaeasensustricto.Oncaea
Oncaeidae. The large type genus Oncaea sensu lato, which cur- s.str.isdefinedbyacombinationofcharactersincludingtheabsence
rently contains over 70 validly described species (Heron & ofaconicalprojectiononthedistalmarginofP4endopod,ornamen-
Bradford-Grieve, 1995), has been recognized as a paraphyletic tationofthelabrumandofthedorsalbladeofthe mandible, sexual
assemblage(Huys&Bottger-Schnack, 1996/97).Adetailedphyloge- dimorphism in the antenna and in the endopods ofthe swimming
netic analysis of the three oncaeid genera at the species level is legs. Oncaea s. str. is considered as the sister-group of Triconia
currentlyinprogressandwillresultintherecognitionofnumerous Bottger-Schnack, 1999, andtheestablishmentoftherevisedgenus
new genera. Some preliminary results of the phylogenetic study isbrieflysubstantiatedinthepresentpaper.Adetaileddiscussionof
werebrieflypresentedby Bottger-Schnack& Huys (1998). phylogenetic relationships of Oncaea s.str. within the Oncaeidae
The Red Sea is an extreme environment, with constant and will be published separately (Huys & Bottger-Schnack, in prep.).
unusually high deep-seatemperatures (21.7°C) andsalinities (40.5 Oncaea s.str. currently includes 8 species, 6ofwhichhadprevi-
PSU)(Edwards, 1987).Duetotheseuniqueenvironmentalconditi- ouslybeenreportedfromtheRedSea(Bottger-Schnack, 1994)and
ons an impoverished zooplankton fauna is found in the Red Sea, are redescribed in the present account. For O. mediterranea,
which is characterized by the absence of true deep sea species redescribed recently by Bottger-Schnack & Huys (1997b), some
(Weikert, 1982, 1987). This phenomenon was also reported for short corrective notes will be given. A new species similar to O.
oncaeid copepods (Bottger-Schnack, 1994, 1999) and their esti- clevei Friichtl will be described. The taxonomic status ofO. curta
matedspeciesnumberintheRedSea(about26)appearstobelowin Sars, forwhich nomaterial was available, will bediscussedon the
comparisontotheadjacentArabianSea,wherethevastmajorityof basisofliteraturedata.
theabout70recordedoncaeidspeciesandformsismadeupbydeep- The type species of Oncaea s.str.. O. venusta, was recently
livingrepresentatives(Bottger-Schnack, 1994). Thesurface waters redescribedindetailbyHeron&Bradford-Grieve(1995),basedon
in the Red Sea show a considerable increase in salinity from the specimenscollected in the GulfofNaples, nearthe type locality in
southernentrancetothecentral-northernareas(Morcos, 1970).Due the Mediterranean Sea. Theiraccountdoesnotcontaininformation
tothelessfavourableenvironmentalconditionsinthenorth,species about the two size variants ofthe species, forma typica and forma
numbers ofplanktonic taxagenerally decrease from south to north venella (Farran, 1929), which are generally known to occur in
(e.g.Halim, 1969;Kimor, 1973;AlmeidaPrado-Por, 1983;Bottger- tropical and temperate areas (Malt, 1983b), but are poorly docu-
Schnack, 1995). For oncaeid copepods, however, a corresponding mentedmorphologically. Apartfromadistinctsizedifference,only
regional decrease in species number from south to north is less few minordifferences in body morphologyhave beenreported for
pronounced (Bottger-Schnack, 1995). This unexpected result was the two forms so far (Farran, 1929; Sewell, 1947; Ferrari, 1975;
assumedto be at leastpartly attributable tothe taxonomic difficul- Boxshall, 1977a). In the Red Sea, both size variants ofO. venusta
tiesencounteredintheidentificationofoncaeids,sincetheproportion occur. They differ considerably in spatio-temporal distribution
ofunidentifiedformvariantsrecordedinthesouthwasmuchhigher (Bottger-Schnack, 1990b, 1995), which may indicate reproductive
thaninthenorth. Inasubsequenttaxonomicstudyfivenewspecies isolation. Both forms ofO. venusta will be redescribed in detail in
of oncaeids were described, four of which occurred mainly or the presentaccount, includingobservations with scanningelectron
exclusively in the southern area (Bottger-Schnack, 1999), thereby microscope(SEM).Particularattentionispaidtomicrostructuresin
indicating some latitudinal difference in species numbers for this the mouthparts and on the exoskeleton. which might provide new
copepod group. and helpful information for the separation ofthe two forms. The
The ecology of oncaeid copepods in the Red Sea has been relationshipofthetwoRedSeaforms withthe speciesoccurringin
investigatedintensivelyduringthepastyearswithintheframework theMediterraneanSeaisdefineduponre-examinationofspecimens
ofmultidisciplinary environmental research programmes (Thiel et from Heron &Bradford-Grieve's material. The presentknowledge
ah, 1986;Weikert, 1988).Thespeciesdiversity,verticaldistribution ontheworld-widedistributionofthetwovenustaformsisreviewed.
and diurnal vertical migration, as well as some biological parame- The two size variants of O. media as defined by Sewell (1947)
ters, such as variation in body length and breeding activity or have recently been recognized as distinct species by Heron &
feeding ofoncaeid copepods were studied on the basis ofroutine Bradford-Grieve (1995). They assigned forma majorto O. media
samplingwithfinenetsof0.1 mmor0.05mmmeshsizeintheupper Giesbrecht (except for his Plate 47, Fig. 11), and described forma
500m or 1000mofthewatercolumnduringdifferentseasons and minorasanewspecies,O.scottodicarloi.Bothspeciesoccurinthe
invarious regions [see Bottger-Schnack (1999) forareview ofthe RedSeaand arebriefly redescribed inthe present paper, including
literature].ThetaxonomyofRedSeaOncaeidaeislesswellknown, someimportantmorphologicaldetailsnotnotedbytheseauthors.O.
however. Boxshall & Bottger (1987) and Bottger-Schnack & waldemari,whichisverysimilartoO. mediaandO. scottodicarloi,
Boxshall(1990)describedfournewoncaeidspeciesfromthecentral had recently been described from Brazilian waters by Bersano &
RedSea,andprovidedaredescriptionofOncaeaatlanticaShmeleva. Boxshall (1994). Due to some descriptive errors, however, the
More recently, O. mediterranea (Claus) was redescribed from this authors did not notice the close relationship ofO. waldemari with
SEVEN SPECIES OFREDSEA ONCAEA 27
species of Oncaea s.str. and erroneously placed it in a group equippedwith netsof0.1 mmmesh, werealsoexamined. Astation
containing O. petila Heron, O. ovalis Shmeleva and others. In the listandsamplingdataaregiveninTableI.Theplanktonwasinitially
present account, O. waldemari is completely redescribed based on fixed in a 4% formaldehyde-seawater solution buffered with
Red Sea specimens (figures) and the type material from Brazilian hexamethylene tetramine and transferred after ca 2 years into a
waters, with additional comparisons on specimens from different preservation fluidof5% propyleneglycol, 0.5% propylene pheno-
localities in the Atlantic and Pacific Ocean. xetol, and 94.5% filtered seawater (Steedman, 1976). Specimens
were dissected in lactic acid, mountedon slides in lactophenol and
sealedwithtransparentnail-varnish. Allfigureshavebeenprepared
MATERIAL AND METHODS using a camera lucida on a Leitz Dialux differential interference
contrast microscope.
Oncaeidswerecollected using a multipleopening-closingnetwith Totalbodylengthandtheratioofprosometourosome(excluding
amesh sizeof0.05 mm duringcruise 5/5 ofR/VMeteor(Weikert, caudal rami)werecalculatedasthesumofthe middorsal lengthsof
1988)invariouslocationsoftheRedSea(Fig. 1).Samplescollected individualsomitesmeasuredinlateral view.Inthecaseoftelescop-
duringcruise 29 ofR/V Valdivia with the same sampling gear, but ing somites these lengths are measuredfrom the anteriortothe
Table 1 Samplingdataofmultipleopening-closingnetinthe RedSeaandadjacentareas(D=Day.N=Night).
Stn. No. Date Time Totalwaterdepth(m) Meshsize(mm) Geographicposition(°N,°E)
RedSea+GulfofAden
R/VValdivia Cruise29
130 28.10.1980 D 1960 0.1 21°25.5\38°01.9'
664 21.2.1981 D 2000 0.1 21°22.r,38°05.1'
R/VMeteorCruise5/5
631a 11.7.1987 N 1400 0.05 11 55.5',43°37.9'
663 20.7.1987 D 1200 0.05 22°58.4',37°19.4'
703 3.8.1987 D 970 0.05 15 34.8',41 54.9'
708 5.8.1987 D 190 0.05 13°40.0'.42°37.4'
NorthernArabianSea
R/VMeteorCruise32/3
247 14.5.1995 D 3000 0.05 ca 19°.ca65°
EasternMediterraneanSea
R/VMeteorCruise5/1
35 20. 1.1987 N 3400 0.05 34°25.3'.26°14.8'
30° $?: 30'
20'
20°
10'
10° [•
N
N
30°
Fig1.9187;L•oc=atMieotneoorf-sCtrautiiosnes5i/n3at,heApRreidlS1e9a87a;nTda=djMaectenetora-rCerasu.ise5=/5V,tfJ/u<7lny'//Aflu-gCurusitse12998,7;Octo=beMret1e9o80r,-CFreubirsuear3y2/31,98M1a;y 1=99M5e.teor-Cruise5/1,January
28 R. BOTTGER-SCHNACK
posteriormargin.Thisapproachdiffersfromthattraditionallyused dimorphismin lateral armatureofenp-2, withsetaIIImuchstouter
in oncaeid taxonomy, where the telescoping of somites is not andsetaIVspiniformandcurvedinmale,bothelementsshorterthan
consideredin length measurements. Traditional lengthdataofRed in female; often also expressed in coxobasal seta, being short and
SeaoncaeidsasgivenbyBottger-Schnacketal. (1989)areonlyup naked in male.
to 70% of the sizes presented in this paper, due to the excessive Labrum distinctly bilobate, forming paired semi-circular
telescopingofsomitesinthesortingmedium.Inordertomakesizes posteroventral lobes. Lobeswithoutmarginalteethbutwithrowof
ofthe species in this paper comparable to those ofprevious taxo- minutedenticlesaroundouterventralmargin,withrowoflongfine
nomic descriptions (e.g. Heron & Bradford-Grieve, 1995; Bersano setules latero-distally (except for c/eve/-subgroup) and dentiform
&Boxshall, 1994),lengthdataofeachspecieswereobtainedbythe processes converginganddecreasing in size medially. Lobes sepa-
traditional method as well (i.e. measured dorsally from the tip of ratedbysemicircularvertexcoveredanteriorlybyoverlappingrows
prosometothe distal endofcaudal ramus) and are given in square ofsmallhyalinepetaloidflaps,flankedbyslit-likeporeslocatedon
brackets. proximal part ofeach lobe; posteriorface with median sclerotized
Descriptiveterminologyforbodyandappendagesfollowsthatof teethandusually withpairedpatchesoflongfinesetules(absentin
Huys andBoxshall (1991). Abbreviationsusedinthetextare: ae= media). Anterior face with paired spinular patches or denticulate
aesthetasc; CR = caudal rami; enp = endopod; exp = exopod; rows(exceptforvenusta);pairedintegumentalpocketsusuallywell
exp(enp)-l(-2,-3)=todenotetheproximal(middle,distal)segment developed, free margin of pockets serrated or ornamented with
ofaramus;P1-P4=swimminglegs 1^1.SpeciesofOncaeidaehave denticle row.
a number of pores and other integumental structures (e.g. pits, Mandiblewith2blades, 2setae and 1 spine. Dorsalbladewith3
scales) on body surfaces, but only those discernible with a light dentiform processes along distal margin and up to 2 additional
microscope werefiguredormentioned. processes along dorsal margin.
O. venustawasexaminedwithaPhilipsXL30scanningelectron Maxillule weakly bilobate; praecoxal arthrite with innermost
miscroscope. Specimens were prepared by dehydration through elementproximallydisplacedandoutermostelementspiniformand
graded ethanol, critical point dried, mounted on stubs and sputter- bearingtransverserow ofspinules.
coatedwithpalladium. Maxilla. Allobasis shorterthan syncoxa.
Type and other material is deposited in the collections of The Maxilliped (female). Large, moderately ovoid. Basis without
Natural History Museum, London (BMNH), Smithsonian Institu- ornamentation on posterior surface; anterior surface with spinular
tion (USNM) and the Zoologisches Institut und Museum der row and spinular fringe along palmar margin half the distance
UniversitatHamburg(ZMH).Paratypesorothermaterialretainedin between distal seta and endopod; both palmar elements long,
personal collection, R. Bottger-Schnackdesignated (RBS). spiniformand spinulose, similarin length. Enp-1 completely sepa-
rated. Enp-2 with long, minutely pectinate claw,rudimentaryouter
setule andfused unipinnate innerspine.
GENERIC DIAGNOSIS Maxilliped(male). Palmar margin forming shallow longitudinal
cleftbordered by anteriordenticulate fringe and posteriormultiple
rows of coarse, blunt spinules; not developed into distal flap.
OrderPOECILOSTOMATOIDAThorell, 1859 Anterior surface of basis with patch of transverse spinular rows.
Family ONCAEIDAEGiesbrecht, 1892 Palmar setae short, smooth. Endopodal claw curved, naked, with
hyaline apex.
PI exopod. Outer and terminal spines with subapical tubular
Oncaea sensu stricto
extensions.
Diagnosis. Bodycyclopiform, prosome stoutorbroad-oval. P2- PI endopod. Enp-3 distal spine stout, withbroad serratehyaline
bearingsomitewith(c/eve/-subgroup)orwithout(vem/sta-subgroup) flange; base of distal inner seta concealed beneath long anterior
dorsoposterior projection in female. Cephalosome without lateral spinousoutgrowthofsegment;lengthofoutgrowth(often)sexually
lobate extensions. Genital double-somite female slightly flask- dimorphic, relatively longerinthe male.
shaped,notparticularlyswollendorsally.Firstandsecondpostgenital P2-P4 exopods. Outer spines stout, with broad, serrate hyaline
somitesshorterthananalone. Analsomitewithwideanalopening; flanges; lateral spines not markedly increasing in size distally.
operculumwith small spinules. P2-P4endopods3-segmented. Enp-3 twiceaslongasenp-1 and
Exoskeleton wellorheavilychitinized, usuallyornamentedwith -2 combinedorlonger; with large conical processes onP2-P3,not
numerouspores, ridges andscales. on P4. Enp-3 distal spine short in P2-P3, longerin P4; distal outer
Sexual dimorphism in antennule segmentation and armature, spinesmallinP2-P3,alwayslongerthanconicalprocessinfemale.
antennary setae, maxilliped, genital segmentation and ornamenta- Sexual dimorphism usually expressed in length of conical proc-
tion,endopods ofP1-P3 (sometimes alsoinP4),P5 andP6, andin esses,being longerinthe male, andin spine length ofenp-3, being
caudal ramus. reducedin the male.
Antennule6-segmentedinfemalewitharmatureformulal-[3],2- Swimming leg armatureformula:
[8],3- [5],4-[3+ae],5-[2+ae],6-[6(1 +ae)];4-segmentedinmale
withformula l-[3],2-[8],3-[4],4-[ll +(1 +ae)+2ae]. Distalmost
Leg Coxa Basis Exopod Endopod
setaoffemale segment3 absent in male. Aesthetascs slender.
Antenna. Enp-1 withtriangularprojectiononoutermarginform- PI 0-0 1-1 I-0;I-1;III,I,4 0-1:0-1:1,5
ingconcavitydistally;innermarginwith 1-2denticularrows.Enp-2 P2 0-0 1-0 1-0:1-1;III.I,5 0-1:0-2:1,11,3
shorterthan enp-1; posterior surface with double row ofspinules; P3 0-0 1-0 I-0;I-1;II,I,5 0-1:0-2:1,11.2
lateral armature consisting of 3 well developed, bare or minutely P4 0-0 1-0 I-0;I-1;II,I,5 0-1:0-2:1,11.1
pinnatesetae(I,IIandIV)and 1 pinnatespine(III)infemale;distal
armature consisting of 4 pinnate setae, 1 long bare or minutely P5small; representedbyouterbasal setaandsmallexopodwith
pinnateseta,and2baresetae;posteriorsetawelldeveloped.Sexual 2 spiniform setae; exopod delimited at base in females, fused to
SEVEN SPECIESOFREDSEA ONCAEA 29
somite in males; sometimesadditional sexualdimorphism in shape oflongsetulesonthe latero-distalmarginofthe lobesbeingabsent
and length of exopodal setae. Genital apertures of female large; in thec/ev<?/-subgroup.
located near midregion ofdorsal surface ofgenital double-somite Oncaeacurta Sars, 1916 (p. 228, Plate IV, as Oncceacarta) was
butusuallyinproximalhalf;eachoperculumwithsmallspineand2 originally described from the western Mediterranean, near the
minute spinules orspinous processes. Moroccoancoast.Thespecieshasalsobeenwidelyrecordedatlow
MaleP6membranousflapsproducedposterolateral^intospinous latitudes in the Atlantic and Pacific [as compiled by Malt (1983a)
process; without armature. and Razouls (1996)]. Recently, Heron & Bradford-Grieve (1995,
Caudalramusabout3-4timesaslongaswideorshorter,without p.41)recordedthe speciesfromtheGulfofNaples,butatthe same
conspicuous dorsal expansion surrounding base ofseta VII. Seta I timenotedintheirsamplesseveralasyetundescribedspeciesclose
absent; setae II and III unipinnate; setae IV and V not resilient, toO.media,O.scottodicarloiandO.curtaindicatingthatacomplex
relativelyrigidandbipinnate;setaVIIplumoseanddistinctlyshorter of species close to O. curta exists within Oncaea s.str. Thus, a
than V; seta VI spiniform and sparsely pinnate. None of setae numberofdifferent species mighthavebeen recorded in the litera-
displaced. Sexual dimorphismexpressed in lengthto widthratioof tureunderthewrongnamecurta(e.g. Boxshall 1977b, seeremarks
CR,beingsmallerinmale,andinproportionallengthsofcaudalsetae. below)andthegeographicalrecordsofO. curtaappeartobedoubt-
ful. Duetothe identificationproblems,the specieshaderroneously
TYPESPECIES. Oncaea venusta Philippi, 1843 (by monotypy)
been placed into the £>oviwfl/?/-group in the preliminary cladogram
Other species of Bottger-Schnack & Huys (1998). The species could not be re-
O. mediterranea (Claus, 1863) examinedduringthepresentstudy,sincenomaterialwasavailable.
O. media Giesbrecht, 1891 Therefore. Sars' description was taken as a basis to compare the
O. curta Sars, 1916 [not O. curta sensu Boxshall, 1977b] morphology of O. curta with the closely related O. media, O.
*0. cleveiFrifchtl, 1923 scottodicarloi and O. waldemari (see under O. scottodicarloi. Re-
[ O.praeclara Humes, 1988] syn. ofO. venusta marks). A thorough revision of O. curta is needed to clarify the
O. waldemari Bersano & Boxshall, 1994 taxonomicconfusion surrounding this species.
O. scottodicarloiHeron & Bradford-Grieve, 1995 OncaeacurtasensuBoxshall(1977b: p.141-143,Table 1-2.Fig.
*0. paraclevei sp. nov. 21a-k) does not belong to Oncaea s. str. Malt (1983a) has already
pointedoutthe similarity ofthe species with O. illgiHeron, which
Species inquirendae
belongstothebowmani-gmupasdefined in thephylogenetic study
OOnnccaaeeaa sspp.. 21 FFeerrrraarrii,, 11997755 ofBottger-Schnack& Huys(1998;theirspeciesgroup5).Common
O. philippinensis (Kazatchenko & Avdeev, 1977) characteristicsofthisgroupare veryelongateconical processeson
thedistalendopodmarginsinP2-P3andaveryrobustmaxillipedal
[Speciesmarkedwithanasterisk(*)belongtotheclem'-subgroup.
basis, armed with 2 relatively short setae. Boxshall (1977b)
remaining species belong to renusta-subgroup.]
synonymized O. curta with O. oralis Shmeleva, O. longiseta
Remarks ShmelevaandO. latimanaGordeyeva.aswellaswithOncaeasp. 1
WithintheOncaeidaeOncaeas.str.belongstoalineagecomprising and 2 ofFerrari (1975), but his opinion was not followed by Malt
the conifera/similis-gwup (Triconia Bottger-Schnack, 1999), the (1983a) norin the present account.
notopus-group and the brocha-group (including O. brocha Heron Oncaeasp. 1 andsp. 2describedbyFerrari (1975;Oncaeasp. 1:
and O. olsoni Heron). These four groups correspond with species p. 228,Figs. 6E, F,7A-D; Oncaeasp.2: p.228.Figs.6G, H,7E-H)
groups 2, 3+4, 6 and 7 recognized by Bottger-Schnack & Huys are placed in Oncaea s.str. on the basis of the swimming leg
(1998) andtogetherareconsidered toformamonophyletic lineage armature, the lack ofa conical process on the distal margin of P4
on accountofthe structure ofthe labrum (medianconcavity with4 endopod, and the size and position ofthe maxillipedal setae. Malt
posterior dentiform processes) and the male maxilliped (palmar (1983a) tentatively assigned Oncaea sp. 1 to 0. media Giesbrecht
margin with multiple overlapping rows ofblunt spinules). Oncaea formaminorand Oncaeasp. 2toboth O. curtaSarsandO. venusta
s.str.isconsideredhereasthesistergroupofTriconiaonthebasisof Giesbrecht f. venella, reflectingthe author's undecisivenessonthis
the presenceofintegumental pockets on the anteriorsurfaceofthe matter.Sincetheoriginaldescriptionofbothspecieslackssufficient
labrum and the formation of the dorsoposterior projection on the detail necessary for unequivocal identification, they are regarded
second pedigerous somite. The fact that the latter character is not here asspecies inquirendae in Oncaea s.str.
expressed in all membersofboth generais interpreted as the result Myspictosum philippinensis Kazatchenko & Avdeev, 1977 (p.
of secondary loss which happended convergently in each genus. 44-47,Fig.9a-i, lOa-g)hasbeensynonymizedwithOncaeas.l.by
Oncaeas.str. differsfrom Triconia inthe sexual dimorphismofthe Malt(1982a;erroneouslyspelledMyctospictosumbyMalt)andher
antenna(setaIIandIVmodifiedinthemale),thepresenceofpaired opinion was followedby Huys & Bottger-Schnack (1996/97). The
slit-likeporesontheanteriorsurfaceofthelabrumandtheabsence single maleofO.philippinensiswasfoundonthegillsofthedeep-
ofaconical process on the distal endopod segment ofP4. A more seafishMyctophumspinosumcollectedinthe PhilippineTrenchat
detailed discussion of the phylogenetic relationships of Oncaea 7255m,whichisthedeepestrecordofanoncaeidspeciessofar.The
s.str.withintheOncaeidaeisbeyondthescopeofthispaperandwill unusually deep record has been regarded as accidental rather than
be published separately (Huys & Bottger-Schnack, in prep.). real (Huys & Bottger-Schnack, 1996/97). O. philippinensis might
Therevisedgenusincludestwosubgroupsofspecies,thevenusta- well belong to Oncaea s.str., based on the modified seta IV on the
subgroupandthe c/evei-subgroup. Females ofthe cleve/-subgroup antenna, which is hook-like as in most other species ofthe genus.
arecharacterizedbyadorso-posteriorprojectionontheP2-bearing However,the legarmature in Kazatchenko& Avdeev'sdescription
somite,whichislackinginthevenusta-subgroup.Thedorsalprojec- is incomplete in P2 (endopod missing) andvery unusual in PI,the
tion on the prosome ('hump') is a sexually dimorphic character, endopodshowing4innersetaeand3outeranddistalspines,witha
which is absent in males. Thus males ofboth subgroups are very conical process at the distal margin. This combination ofarmature
hard to distinguish. A further morphological character separating elementsisnotfoundinanyoncaeidspeciesknownthusfarandthe
the2subgroupsisfoundintheornamentationofthelabrum,therow speciesis regarded here asspeciesinquirenda in Oncaea s.str.
30 R.BOTTGER-SCHNACK
OncaeapraeclaraHumesisregardedasasynonymofO.vemista, 13.0'W; collected 5 December 1979; DSRVAlvin dive no.
ongroundsthatwillbediscussedbelowunderO. venusta,Remarks. 998;depth 2450m; 1 specimen inalcohol labelled Oncaea
praeclara, Humes, 1988, 1 6 (USNM 234 112): this vial
contains Oncaea venusta (1 6, possibly f. typica).
DESCRIPTION OF SPECIES (d) NorthPacificOcean, GalapagosRift,00°47'N,086°08'W;
collected24January 1979;DSRVAlvindiveno.883;depth
2493m;4specimensinalcohollabelledOncaeapraeclara,
Oncaea venusta Philippi, 1843 3 66, 1 9(USMN234114): this vialcontainsamixture of
Oncaea venustaPhilippi (1843): 62-63, Tafel III, Fig. 2a-d. O. venusta (1 ovigerous 9, 1 6), Oncaea sp. (1 6,possibly
venustaf. venella). Triconia sp. (1 6).
Oncaa venusta Giesbrecht, 1892 (e) North Pacific Ocean, Galapagos Rift, 00° 48.25'N, 086°
Oncaa venusta Farran, 1929 13.48'W; collected 30 November 1979: DSRVAlvin dive
Oncaeapraeclara Humes, 1988
no. 983; (material donated to R. Bottger-Schnack by A.
Reliabledescriptions. Giesbrecht(1892): 590-604, 755, 756, Humes); 11 specimensinalcohollabelledOncaeapraeclara,
774, 789, Plate 2, Fig. 5, Plate 3, Fig. 7, Plate 47, Fig. Humes 1988,4 99,166: thisvialcontainsamixtureofO.
2,5,13,19,39,44,48,50,54,58 [as Oncaa venusta]; Farran (1929): venusta (2 99, 3 66), O. media (2 99), O. clevei (1 6),
284-285,Fig.33[asOncceavenusta];Wilson(1932):353-354,Fig. Oncaeidae indet. (2 66), Corycaeidae indet. (1 juvenile);
213a-d; Mori (1937,reprinted 1964): 119-120,Plate66Figs. 1-9; (RBS).
Dakin & Colefax (1940): 116, Fig. 205Aa-f; Sewell (1947): 263- (f) East Pacific Rise, 12° 48.52'N, 56°48'W; collected 22
X26X4;VOFlisgos.n1[1M-S1]3((139)4;9T)a:na1k0a1(-1190640,):Pl7at1e-7X2X;ICoVrrFailgsE.s1t-r8ad(a9(),19P7l0a)t:e Ndeopvtehm2b6e3r0 m198(7m,ateHryidarlodnoanuatteCdrutiosRe., HNuayust,ilNeHdMi.veby22A1.;
216-217; Chen et al. (1974): 40-41, Plate 6 Figs. 1-5; Ferrari Humes); 9 specimens in alcohol labelled O. praeclara,
(1975): 225-228, Figs. 5I-K, 6A-D; Boxshall (1977b): 124-128 Humes,5 99,5 66: thisvialcontains5 99(1 9ovigerous)
Figs. lla-k(9), 12a-d(6);Ho(1984):41^44,Figs. 12-14;Humes and4 66ofO. venusta(all specimensemptyexoskeletons
(1988): 475-485, Figs. la,b,d [notFig. lc, e], 2a-i, 3a-g (9), 4a-g with no internal tissue).
(6) [as Oncaeapraeclara]; Huys & Boxshall (1991): 286.289,445 (5) Sargasso Sea, near Bermuda, 31° 37.94'N, 64° 09.45'W; col-
Figs. 2.10.8.B, 2.10.10.A, 2.10.21.B, 2.10.21.D, 2.10.24.A; Heron lected9July 1998 with 1 m net,mesh size0.15 mm;depth210
& Bradford-Grieve (1995): 33,36,Figs. 14e-l, 15a-j, 27b, 28; Itoh m;leg.D.Steinberg: several 99(ovigerousandnon-ovigerous),
[in:Chihara&Murano 1997]:981-982,Plate223Figs.371(left)a- 3 66 in alcohol, for molecularanalysis (A. Bucklin, Durham,
b (f. venella), 371(right) a-e (f. typica). New Hampshire); 2 99, 2 CV 99inalcohol (RBS).
DOUBTFULDESCRIPTIONS. Razouls(1974): 236-237,Figs. 1A-H Philippi's (1843)descriptionofO. venustawasthefirstaccountof
(9),2A-C(<?);Humes(1988):onlyFig. lc,e(asOncaeapraeclara). an oncaeid species. It was based on a single male specimen col-
TYPELOCALITY. WesternMediterranean Sea, nearPalermo. lected in the western Mediterranean, nearPalermo. Unfortunately,
the specimen was lost by accident before the author could com-
Materialexamined.
plete the description. Giesbrecht (1892) redescribed O. venusta in
Red Sea: seebelow underO. venusta f. typicaand f. venella more detail from the GulfofNaples and recently. Heron & Brad-
Otherareas: ford-Grieve (1995) provided an excellent redescription of the
(1) GulfofNaples, Italy; collected 1 February 1967; depth 0-100 species basedon material from the GulfofNaples as well as from
m; leg. B. ScottodiCarlo; identifiedby G.A. Heron: 19, 16in otherlocalities in the Atlantic andPacific Ocean. Both authors do
alcohol (RBS). not mention the existence of different size variants among O.
(2) Pacific Ocean, off Tanega Islands; R/V Toyoshio-maru; col- venusta, although the range of size variation was quite large in
lected5November 1994withORI-planktonnet,meshsize0.33 Giesbrecht's specimens from the Pacific. In 1929, Farran
mm; oblique haul, depth 1600 m; leg. S. Ohtsuka: several 99 describedtwodistinctsizemorphsofO. venusta,formatypicaand
and <Jc?(RBS). forma venella, from various Atlantic and Pacific locations, which
(3) Sea of Japan, Tassha Bay, Sado Island; collected 1978 from were separated mainly by their size and some minor morphologi-
colonies ofSolandria secunda (Inaba), a hydroid; depth 10m; cal characters. The two forms were distinguished in some ofthe
leg. andidentifiedbyJ.-s. Ho; 4 99in alcohol (RBS). subsequent taxonomic descriptions (e.g. Tanaka, 1960; Ferrari,
(4) (a) North Pacific Ocean, Galapagos Rift, 00° 48.0'N, 086° 1975; Boxshall, 1977b) and a third, 'robust' form was added by
13.0'W; collected7 December 1979; DSRVAlvin dive no. Boxshall (1977b). IntheRedSea,bothformvariantsofO. venusta
990;depth2451 m; 1 specimeninalcohol,labelledOncaea sensu Farran occur. They differconsiderably in temporal and spa-
praeclara, Humes, 1988, holotype 9(National Museumof tial distribution (Bottger-Schnack, 1990b, 1995), thus indicating
Natural History, Smithsonian Institution, Washington, DC, the existence of reproductively isolated populations. A detailed
reg.no.USNM234 109):thisvialcontainsOncaeavenusta morphological examination ofboth size variants was undertaken
(1 9);partsofthespecimenbrokeoffduringre-examination duringthepresent study, including microstructures onthe append-
and are mounted on slides in lactophenol [right antennule ages and on the exoskeleton (pores, scales), partly by using SEM
(segment 4-6), left antenna (endopod segments 1 and 2), analyses. The results pointed out several morphological diffe-
right maxilliped (claw)]. rences between the two forms not noted in the literature before,
(b) NorthPacificOcean,GalapagosRift;furthersamplingdata but these were notregarded as sufficientto warrantrecognitionof
notspecified; 1 specimeninalcohollabelled: Acc.no.3766 the two forms as separate species. In order to provide the
47; O. praeclara, 13 August 1987 (USNM 234 111): this morphological basis required forfuture taxonomic analyses on O.
vial contains Oncaea venusta (1 9). venusta, both forms are redescribed. A further approach to
(c) North Pacific Ocean, Galapagos Rift, 00° 48.0'N, 086° differentiate the two forms using alternative methods, e.g. mole-
cular analysis, is currently in progress.
SEVEN SPECIESOFREDSEA ONCAEA 31
Oncaea venusta Philippi, 1843 forma typica Farran, 1929 Antennule 6-segmented (Fig. 2E), relative lengths (%) of seg-
ments measured along posterior non-setiferous margin 8.4 27.6
OncaeavenustaFarran(1929):284[asOncceavenustaformatypica] 39.3 : 10.7 : 4.7 : 9.3. Armature formula: l-[3], 2-[8], 3-:[5], 4-:
Onc&a venusta formatypica Farran, 1929 [3+ae], 5-[2+ae], 6-[6+(l+ae)]. Small element on segment 4
ornamented withrowofscalesalongentire length, tipwithtubular
TYPELOCALITY. Notspecified,variouslocationsinthetemperate extension (SEM observation, not figured). Small element on seg-
andtropical Atlantic, as well as southofNewZealand.
ment 6 (arrowed in Fig. 2E) with tubular extensions (Fig. 8C),
Materialexamined. indicating sensory function.
Central Red Sea, 21° 22.09'N, 38° 05.09'E: Stn. 664; R/VValdivia Antenna 3-segmented, distinctly reflexed (Fig. 3A). Coxobasis
leg29:collected21February 1981 withMSN0.1 mmnet(Haul218/ withrowoflong,finespinulesorsetulesnearoutermarginandwith
5); depth0-50m; total waterdepthca2000 m. few additional denticles on proximal and distal part of outer
(a) 5 99, 5 66 inalcohol (BMNH 1998.2777-2786). (exopodal) margin, curvedrow ofdenticles on posteriorface; with
(b) 5 99, 5 66 in alcohol (ZMH K-39586). bipinnate setaat innerdistal corner. Endopod segments unequal in
(c) 2 99dissectedonslides, 1 9inalcohol;3 66dissectedonslides, length; proximal endopod segment subtriangular forming outer
1 6 in alcohol; 1 9, 1 6 in mating position in alcohol (RBS). lobateoutgrowthbearingpatchofbranchedtubularextensions(Fig.
8D, E). with row ofdenticles along posterior inner margin. Distal
Description. Note illustrations are basedon (c).
endopod segment distinctly shorter than proximal endopod seg-
Adultfemale (Figs. 2-5, 8A-E, 9A-F). ment,withnarrowcylindricalbasearticulating;withtwopatchesof
Body length (measured in lateral aspect; from anterior margin of branched tubular extensions along outer margin (Fig. 8D); lateral
rostralareatoposteriormarginofcaudalrami,calculatedassumof armaturewith4elements,numberedusing RomannumeralsinFig.
individual somites): 1615 um [traditional method 1130 urn, range: 3A: 1 unipinnate spiniform seta (III) and 3 curved setae (I, II, IV),
1000-1230 um, based on 14 specimens (Bottger-Schnack et ai. setae I and II sparsely pinnate, seta I shortest: distal armature
1989)]. consisting of 7 elements: 1 long curved unipinnate seta (E), 4
Exoskeletonheavilychitinized,coveredwithnumerousgranules, slightly curved unipinnate setaeofgraduated length (A-D), setaD
forminglongraisedstructures(lines),especiallyalonglateralpartof beingshortest,and2slendernakedsetae(FandG),similarinlength
cephalic shield (Fig. 8A). Prosome 2.1 times length of urosome, and shorter than seta D; none of armature elements spiniform or
excluding caudal rami, 1.7 times urosome length including caudal geniculate.
rami. P2-bearing somite without dorso-posterior projection in lat- Labrum (Fig. 3B,C) distinctly bilobed. Each lobe with row of
eral aspect (Fig. 2B). P3-bearing somite with conspicuous raised minute denticles around outer ventral margin, row of long fine
pore protruding laterally (Fig. 2A). Other integumental pores on setules latero-distally and dentiform processes converging and de-
prosome as indicated in Fig. 2A, B. Pleural areas of P4-bearing creasing in size medially. Lobes separated by median concavity
somite with roundedposterolateral corners. covered anteriorly by overlapping rows ofbroad hyaline petaloid
Proportional lengths (%) of urosomites 12.2 : 57.7 : 8.5 : 9.1 : flaps,flankedbypairedslit-likeporesonproximalpartofeachlobe
12.5.Proportional lengths(%)ofurosomitesandcaudal rami 10.0: (Fig. 9A, B; position ofpore arrowed in Fig. 3B). Anteriorsurface
47.0:6.9:7.3 : 10.2: 18.6. with well developed integumental pockets (Fig. 9C) either side of
Genital double-somite 1.5 times as long as maximum width median swelling, free margin ofpockets serrate (Fig. 9D); median
(measured in dorsal aspect) and 1.9 times as long as postgenital swelling with large secretory pore posteriorly. Posterior part of
somitescombined(Fig.2C);largestwidthmeasuredatanteriortwo- medial incision ornamented with four rounded integumental
thirds, lateral margins ofgenital double-somite rounded, posterior thickenings (Fig. 3C). Posterior surface with paired patch ofvery
parttaperinggradually.Pairedgenitalapertureslocatedatabout2/5 longfinesetulesand2largesecretoryporeslocatedonproximalpart
the distance from anterior margin ofgenital double-somite; arma- ofeach lobe.
ture represented by 1 spine and 2 minute spinous processes (Fig. Paragnaths (Fig. 5, 9C) with small lateral extensions, anterior
8B), only 1 ofwhichdiscernible underlight microscope (Fig. 2G). margin densely covered with several rows oflong setules, median
Double-curvedsclerotizationbetween,butslightlyanteriorto,geni- bulge unornamented.
talapertures,porepatternondorsal surface asindicated in Fig. 2C. Mandible (Fig. 3D) with few minute setules on surface ofcoxa;
Anal somite 1.6 times wider than long; about halfthe length of gnathobase with 5 elements, indicatedbycapital letters inFig. 3D:
caudal rami (Fig. 2C). Secretory pore discernible on either side of 1 at subdistal ventral -corner, 2 along distal margin and 2 along
anal opening and additional one near posterior margin. Anterior subdistal dorsal margin; ventral element (A) shorter than ventral
marginofanalopening(vestigialanalopening)withtransverserow blade, with long, fine setules along dorsal side; ventral blade (B)
ofminute denticles. Posterior margin ofsomite finely serrate ven- strong and spiniform, with row ofsetules on posteriorside; dorsal
trallyandlaterally(Fig.2D).Ventralfacewithpairedsecretorypore blade(C) strongandbroad, with3dentiformprocessesalongdistal
nearposteriormargin (Fig. 2C,cf. also Fig. 6E). margin; dorsal elements setiform, the shorter (D) hyaline, flat and
Caudalramus(Fig.2F)about3.5timesaslongaswide.Armature densely setose, the longer(E) multipinnate.
consisting of 6 elements: antero- and posterolateral setae (II+III) Maxillule(Fig. 3E) indistinctlybilobed, withnumerous spinules
long,spiniformandunipinnatealongmedialmargin;outerterminal onanteriorandposteriorsurfaces. Innerlobesubcylindrical,with3
seta (IV) long and plumose; inner terminal seta (V) longest and elements: outermost one spiniform, swollen at base, fringed with
plumose; terminal accessory seta (VI) more than 2/3 the length of coarsespinules,otherssetiformandbipinnate;innermostonelocated
outerterminal seta and 1.4 times longer than caudal ramus; dorsal along concave innermargin at some distance fromotherelements.
seta(VII)aboutsamelengthasposterolateralseta(III)andlessthan Outer lobe with 4 elements; outermost element spiniform, curved
halfthelengthofterminalaccessoryseta,plumoseandbi-articulate andbipinnatealong innerproximal margin, unipinnate alongdistal
atbase. Innermargin ofsomite with fringe oflong setules. Dorsal margin, longer than the following; other elements bipinnate or
anteriorsurface (Fig. 2F) with secretory pore nearinsertion ofseta naked, elementnext tothe innermost shortest.
II. Dorsal surfacecoveredwith numerous small scales (Fig. 2F). Maxilla(Fig.3F)2-segmented,comprisingsyncoxaandallobasis.
32 R. BOTTGER-SCHNACK
Fig.2 Oncaeavenustaf.typica,female(RedSea)(A)Habitus,dorsal(lateralraisedporeenlarged);(B)same,lateral(appendagesomitted);(C)urosome.
dorsal;(D)urosome,lateral;(E)antennule,smallsensoryelementarrowed;(F)caudalramus,dorsal,setaearenumberedusingRomannumerals:(G)P6.
SEVEN SPECIESOFREDSEA ONCAEA 33
A
Fig.3 Oncaeavenustaf. typica,female(RedSea)(A)Antenna,posterior,lateralelementsarenumberedusingRomannumerals,distalelementsindicated
bycapitalletters;(B)labrum,anterior,slit-likeporesarrowed;(C)same,posterior;(D)mandible,showingindividualelements,identifiedusingcapital
letters;(E)maxillule;(F)maxilla;(G)maxilliped.
34 R.BOTTGER-SCHNACK
Fig.4 Oncaeavenustaf.typica,female(RedSea)(A)PI,anterior[a,thirdendopodsegment,showingaberrantspinenumber];(B)P2,anterior;(C)P3,
anterior;(D)P4.anterior.