A new species in the asterinid genus Patiriella (Echinodermata, Asteroidea) from Dhofar, southern Oman: a temperate taxon in a tropical locality

8 Pages·1997·4 MB·

by  Andrew C Campbell

Bull. not. Hist. Mus. Lond. (Zool.)63(2): 129-136 Issued28November 1997
A new species in the asterinid genus Patiriella
(Echinodermata, Asteroidea) from Dhofar,
southern Oman: a temperate taxon in a
tropical locality
ANDREW CAMPBELL ^<
C.
SchoolofBiologicalSciences, Queen MaryandWeslfieldCollege, UniversityofLondon, Mile EndRoad,
London El 4NS, UK.
FRANCIS W.E. ROWE
GoldbrookBoarding KennelsandCattery, Nuttery Vale, Cross Street, Hoxne, Suffolk, IP2J 5BB, U.K.
CONTENTS
Synopsis 129
Introduction 129
SystematicDescription 129
Patiriella 129
ZoogeographicConsiderations 135
Acknowledgements 136
References 136
SYNOPSIS. Thestatusofthehithertotemperate-waterasterinidgenusPatiriellaisbrieflydiscussed,includinginitsdiagnosis
detailsofactinalplateandventral/lateralplatearrangement.Anewspecies,P.paradoxa,isdescribedfromshallowwateronthe
DhofarcoastofOman.ThedistributionofPatiriellaonthe Dhofarcoastisdiscussed inrelationtothepeculiaroceanographic
conditionsandvicariantevents intheregion.
INTRODUCTION SYSTEMATIC DESCRIPTION
Although one of us (ACC) made extensive collections along the PATIRIELLA Verrill
coastsoftheSultanateofOmanbetween 1983 and 1990(Campbell
Patiriella Verrill, 1913: 483; 1914: 263; Fisher, 1919: 410; H.L.
andMorrison, 1988andMarshandCampbell, 1991),theechinoderm
Clark, 1946: 134; Dartnall, 1971: 39; A.M. Clark and Courtman-
fauna of southern Arabia remains incompletely known. However,
Stock, 1976: 80; A.M. Clark, 1983: 365; A.M. Clark and Downey,
thoseechinodermswhichhavebeenrecordedaretropicalspeciesor
1992: 192.
endemic species with tropical affinities (Clark and Rowe, 1971;
Price, 1982; Campbell and Morrison, 1988; Marsh and Campbell, TYPE SPECIES. Asterina (Asteriscus) regularisVerrill, 1870
1991). The discovery (by FWER) of three specimens of a new (1867); by original designation.
species of the predominently temperate-water, asterinid starfish Diagnosis
genusPatiriellaVerril(1913)amongtheOmani shallowwater(less AfterA.M. ClarkinA.M. Clark and Downey (1992), amended.
than 10m) collections from two sites in Dhofar therefore poses a AgenusofAsterinidaewithfivetoabouteleven shortrays (Rup
paradox. to c. 60mm); pentagonal to stellate in outline; aborally arched;
Here we briefly discuss the status of the genus Patiriella and primary abactinal plates in two 'fields', a slightly irregular radial
describe fully the new species. This work attempts to explain the (usually the midradial and first dorsal-lateral series on either side)
presenceofanotherwisetemperate-waterechinodermgenusinthis 'field'andaregularlateral'field'oneitherside;mid-radialabactinal
tropical location, giventhepeculiarlocal oceanicconditions which plates with proximal edge trilobed or simply crescentic; the proxi-
includeupwelling(seesummarybyCampbellandMorrison, 1988), mal concave sides ofabactinal plates subtend spaces with usually
andpast vicariantevents. one to several papular pores, separated by one to several small
The type specimens have been deposited in the Natural History secondary plates; abactinal armament comprising relatively few
Museum, London U.K. (<40 per plate) very coarse, almost granuliform, multipillared
iTheNaturalHistoryMuseum, 1997
130 A.C.CAMPBELLANDF.W.E. ROWE
spinelets; actinalplatesdistinctlyalignedinobliqueseriesbetween Dartnall, 1969b; Patiriellaparadoxa sp. nov.
the second or third, and subsequent adambulacral plates and the Other species Patiriella nigra H.L. Clark, 1938 and Patiriella
inferomarginal plates and delimiting a membranous, proximal, tri- obscura Dartnall, 1971 are considered to be conspecific with P.
angularareawhichisusuallyfilledby severalplates;ventral-lateral oliveri (Benham) and P. pseudoexigua Dartnall respectively by
angleofrayssupportedinternallybyabactinalplateswhichmeetthe Rowe(inRoweandGates, 1995);PatiriellatangribensisDomantay
actinalplatesbyvirtueoftheobliquealignmentofboth;towardsthe andAcosta, 1970,isinadequatelydescribedandcannotconfidently
ray base as the ventral-lateral angle becomes less acute with ray beassignedtothis genus.
depth, totally internalised plates, spanning between the abactinal
and actinal plates, can be found; actinal armament coarse, short Remarks
spines, mostly single, not more than two per plate; furrow spines The genus Patiriella Verrill, 1913, has had a rather chequered
usually two (sometimes one) per plate; subambulacral spines one history. Ithasbeenconsideredavalidtaxonbymostrecentauthors
(rarely two); suboral spines onetofourornone; nopedicellariae. (e.g.Fisher, 1919;H.L.Clark, 1928; 1938; 1946;Livingstone, 1933;
Species included: Patiriella brevispina H.L. Clark, 1938; Madsen, 1956; Dartnall, 1971; A.M. Clark and Rowe, 1971; A.M.
AsteriascalcarLamarck, \%\6\AsteriscuscalcarataPerrier, 1869; Clark and Courtman-Stock, 1976; A.M. Clark, 1983; A.M. Clark
Asteriscus chilensis Lutken, 1859; Asterina dyscrita H.L. Clark, andDowney, 1992)orasynonymofAsterinaNardo, 1834(e.g.H.L.
1923; Asterias exigua Lamarck, 1816; Asterinafimbriata Perrier, Clark, 1916; 1923; Hayashi, 1940; 1977; Mortensen, 1933 (as a
1875;Asterina gunni Gray, 1840; Patiriella inornata Livingstone, subgenus ofAsterina)). The history andcurrent status ofPatiriella
1933; Asterina oliveri Benham, 1911; Patiriella parvivipara has been most recently discussed by A.M. Clark (1983; 1992 (in
KeoughandDartnall, 1978;PatiriellapseudoexiguaDartnall, 1971 Clark and Downey)) who commented (1992:178) that 'The very
(with subspecies pacifica (Hayashi, 1977, as Asterina); Asterina coarseandabbreviated, almostgranuliform,armamentoftheupper
(Asteriscus) regularis Verrill, 1870 (1867); Patiriella vivipara side may warrant asupra-specific distinctionfromA. gibbosa ofP.
a
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Fig.1 a,ScanningelectronmicrographoftheactinialsurfaceofAsterinagibbosafromPlymouthU.K. Scalebar=5mm .G=gonopore;b,Scanning
electronmicrographoftheactinialsurfaceofAsterina''cepheusfromWadiHaart,Sadh. Dhofar,SouthernOman.Scalebar=5mm
A NEW SPECIES OFPATIR1ELLA 131
regularis together with P. gunni (Gray) and P. calcar (Lamarck) HOLOTYPE. BMNH (dry) BMNH 1997.1016
from Australia, also P. exigua (Lamarck) which extends from the
Indo-WestPacific intotheS.E.Atlantic'. Shethoughtreassessment TypeLOCALITY. 0.5 km southeast ofWadi Haart and about4km
oftherankofPatiriellawasbestleftto 'oneofseveralAustralasian northeastofSadhvillage,SultanateofOman(17°04'N,55°06E),
specialiststodetermine . . .',retainingthespeciesexiguaasamem- intertidal, just below level ofthe conspicuous barnacle Tetraclita
berofthegenusPatiriella.AnewreviewofthefamilyAsterinidae, squamosa rufotincta, collected together with 'Asterina' cepheus
includingareappraisalofthestatusofPatiriellaisbeingundertaken (Muller&Troschel, 1842),A.C.Campbell4May 1987(210050201)
by F.W.E.R. elsewhere. However, whilst in the present paper we (fig-2).
acknowledgethataverycloserelationshipexistsbetweenthegenera
Asterina,PatiriellaandPatiria(Gray, 1840)(Patiriaisconsidereda Material. In addition to the holotype, two paratypes (dry).
BMNH
synonymofAsterinaby Hayashi (1940) andA.M. Clark (1983 (in Paratype 1 1997.1017,collectedatthesamelocalitywiththe
BMNH
Clarkand Downey, 1992)); we accept theirseparate generic status, holotype.Paratype2 1997.1018,Raaha,2.5kmwestofWadi
until the matter is more clearly resolved, such a resolution being Ayn,SultanateofOman(16°58'N,54°50'E),c. 8mdepth,onrocks
outside the scope of this paper '. In taking this stance, we have amongst corals, coll. A.C. Campbell, 5 Dec, 1986 (210050202)
amended A.M. Clark's in Clark and Downey, 1992) diagnosis of (fig.2).
Patiriellatoinclude adescriptionofthe alignmentofactinal plates
(included by Verrill (1913) in his diagnosis of the genus) and the EtYMOLOGY. The species name (Lat. paradoxum) refers to the
internal alignment of actinal/abactinal plates at the ventral/lateral unexpected occurrence ofthis predominently temperate-water ge-
angle (described by Verrill (1913) as a feature of the family nus along an otherwise tropical coastline.
Asterinidae).As ataxonomiccharacter, actinal plate alignmenthas
been largely ignored. The exception was Fisher(1917; 1919) who Description of holotype. (Figs 3 a & b; 4 a & b). Specimen
thought this a useful character when distinguishing his new genus stellate in outline, R=l7.8mm, r=9.0mm, R/r=1.98; br=10.3mm
Paranepanthia(type-speciesNepanthiaplatydisca Fisher, 1913)in (across base ofray between first superomarginal on each side), R/
which the plates are aligned obliquely across the actinal surface, br=l.73. Orally flat, aborally arched. Rays more or less elongate
fromAsterina in which he sawthe actinal plates formingchevrons triangular, tapering from a relatively wide base to a rounded tip.
acrosseachinterradialarea,theplatesbeingalignedonlyparallelto Centre ofdisc delimitedby acompleteringofprominent, spinelet-
thefurrowsalongeachray. Fisher(1919) was,however,comparing bearingplates,outsideofwhichasecond,moreorlesscompletering
Paranepanthiaplatydiscawiththespecies'Asterina'cepheus(Miiller ofless prominent platesevident.Theprominent, ovatemadreporite
& Troschel), and VT. coronata (von Martens) and not the type occurs in interradius CD.
species A.gibbosa. In accepting Asterina in this sense, Fisher was Beyondthecentral disc, the imbricatingprimaryabactinalplates
clearlynotfamiliarwiththefactthatinthetype-species,A.gibbosa, form two 'fields' along the rays. Radial 'field' comprising an
the actinal plates, as in Patiriella and Paranepanthia, are clearly irregular, zig-zag series ofmid-radial (carinal) plates and the first
alignedobliquelybetweenfurrowandmarginFig 1a&b(thereisno dorsal-lateral row on each side. Shape ofthis 'field'elongate-leaf-
question, however, that Paranepanthia is a valid genus (F.W.E.R.). shaped along the ray, tapering proximally and distally and widest
A.M. Clark (1971, in A.M. Clark and Rowe) noted Fisher's work at about '/2R. Denuded plates deeply notched, mostly quadrilobed
whenidentifyingtwospecimensofanundeterminedspeciesofwhat (X-shaped), but, at least between '/2-%R, some mid-radial plates
she considered a Paranepanthia from Zanzibar. She considered tri-lobed (Y-shaped), the plates together forming a relatively deli-
(1971:71) the importance of actinal plate arrangement, as a func- cate reticulum. Papular areas, between the plates, are relatively
tional and taxonomic character, required investigation. However, large, up to 0.8mm diameter, each subtending 3-6 papulae
A.M.Clark(1983)didnotexpandfurtheronthismatterinhermore between which 1 or 2 minute, spinelet-bearing secondary plates
recent revision ofthe familyAsterinidae. Although arecent survey usually occur. Primary plates with crystal bodies, except on their
of the family by one of us (F.W.E.R.) does show actinal plate proximal, crescentic ridge which carries 5-7 granuliform spinelets
arrangement to be a useful character in distinguishing some ofthe in a single series; spinelets range from c. 0.30mm long x 0.12mm
genera,actinalplatearrangementundoubtedly hasafunctional role wide (straight sided) to about0.37mm long x 0.14mm wide (these
which is probably micro-habitat related. We include description of larger spinelets becoming club-shaped (0.18mm wide) towards
the internal structure of the ventral/lateral angle in our diagnosis their tip). Lateral 'field' comprising about 10 regularly arranged
following A.M. Clark (1983) who concluded that differences in rowsofplates atthebaseoftherays,closelyimbricatewith adeep
arrangement of these internal plates were important in indicating proximal notch subtending 1-3 papulae occurring in the proximal
taxonomic affinities, aconclusion supported herein, though on the halfofthe first 5 rows ofplates, the papulae not extending to the
basis also, thatit may relatetoray shape within the family. superomarginal line. Lateral 'field' plates with crystal bodies and
from 2-7 spinelets.
Patiriellaparadoxa sp. nov. Ventral-lateral margin sharply delimited, however neither
DIAGNOSIS. Stellate speciesofPatiriella with fiverays; abactinal inferomarginals nor superomarginals significantly larger than im-
plates of aboral, radial 'field' tri-quadrilobed, forming a delicate mediately adjacent actinal or abactinal plates respectively. Infero-
reticulum; papular areas each with three to six papulae and one to marginal plates aligned in the same plane as the actinal surface,
two secondary plates; no suboral spines; proximal actinal plates slightlyprotrudelaterallyandbearagroupof2-3minutespinelets.
each with a single spine. Superomarginal plates aligned vertically, correspond with the
inferomarginals below them andbear 1-2 spinelets.
1 SpeciesattributedtoAsterinas.s.fromoutsidetheAtlanticregionareNOTconge- About 10rowsofactinalplatescounted;thefirsttwoextendingto
neric with the type-species.A. gibbosa (Pennant), and require reallocation to other the tip ofthe ray; plates are alignedboth parallel to the furrowbut
existingornewasterinidgeneraaccordingtoRowe (in Rowe andGates, 1995); the also distinctly obliquely across the actinal surface between the
suggestedrecognitionofAsterinidesVerrill(1913)(type-speciesA.folium(Lutken))as
avalidsubgenusofAsterina,byA.M.Clark(1983; 1992(inClarkandDowney))is adambulacral plates and inferomarginal plates. Oblique alignment
supported,butatgenericlevel,byRowe(inRoweandGates, 1995). accentuated both by the actinal spination and narrow, shallow
132 A.C.CAMPBELLANDF.W.E.ROWE
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A NEW SPECIES OFPATIRIELLA 133
|llll|lllljllll|llll|llll|llll|lilljilil
a
b
Fig.3 a,PhotographofPatiriellaparadoxa,Holotype. fromWadiHaart.Sadh.Dhofar,SouthernOman.Abactinial view.Scaleinmm;b.Photographof
Patiriellaparadoxa,Holotype,fromWadi Haart,Sadh, Dhofar,SouthernOman.Actinialview.Scaleinmm.
furrows occurring between the oblique lines of plates. First com- R/r=2.4;br=9.4mm,R/br=c.2.Generallyverysimilarinappearance
pleteoblique lineofplatesarisesoppositethe secondadambulacral to the holotype, differing only in minor detail. Two furrow spines
plate ineach furrow,creating atriangulararea bounded by the first occurring only on the 1st—4th adambulacral plates, thereafter the
adambulacral plates, distal edge ofthe oral plates and first oblique plates with asingle furrow spine. Small patchofnon-calcifiedskin
seriesineachactinalintermediatearea.Thisproximalareaoccupied occursadjacenttothedistaledgeoftheoralplatesineachinterradius,
by2(interradiiBC,DEandEA),3(interradiusAB)or4(interradius thisproximalactinaltrianglebeingfilledby 1 (interradiiCD,DE)or
CD) plates. A small circular patch of non-calcified skin (up to 2 (interradii EA,AB, BC) plates.
tp0la.ap6teermsimnigndiisnaptmieenretrleaedrti)i(AoucBpc,utrCorDi0n.ga6nad4dmjEamAc.elnAotcntgtionxatlh0ep.lda3its0etsmalmeaecadthgbebeaasoref)athsoeinnogtrlhael,e PR/arr=a1t.9y;pebr=2l. 1.2BmMmN,HR/1br9=917..71.01T8hehadsryRs=p1e9c.im0emnm,is rco=n1t0o.rt0e0dm.mI,t
proximal80%oftheactinalsurface,theremainingdistalplateswith differs from the holotype and paratype 1 in the following features.
Rays are slightly broader at their bases relative to their lengths.
2 small spinelets.
Aborally,centreofdiscnotdelimitedbyaprominentringorringsof
There are 28-29 pairs of adambulacral plates to each furrow.
These aretwice as wide as long. First 12-14plates bear2 tapering plates. Radial 'field' ofabactinal plates is compact, plates closely
imbricating with only the ridge evident and bearing 5-7 spinelets.
furrowspines,proximalmostmoreslenderandshorterthandistalmost
Papularareascontain 1-4papulaeandoccasionallyasinglesecond-
spine(onadambulacral 3: distalmostspine measures 1.0mm long x
0.35mmwide,atbasetapering0.20mmwideneartip;proximalmost aryplate.Actinalspinulationcoarser,otherwisetheplatearrangement
spine measures 0.78mm long x 0.23mm wide at base, tapering to closely similartotheothertype specimens.Actinal proximal trian-
0.14mmwideneartip).Proximalmostspinebecomesrapidlysmaller gSloemfeill3ed6bpyai1rsoro2fpaldataemsb,ulnaocpraatlchpelsatoefsnaoln-ocnaglceiafcihedfsukrirnowe;videeancth.
and peg-like towards the 12th—14th plate, beyond which the
adambulacral plates each bear a single furrow spine. A single, bearing a single furrow and single subambulacral spine, with the
stouter, subambulacral spine (on adambulacral 3: 0.87mm long x exception ofthe first plate with a second, smallerproximal furrow
spine.Furrowandsubambulacral spinesflattenedalongtheirlength
0.29mmwide,moreorlesscylindrical)occursoneachadambulacral
plate.The oral plateseach with4oral (furrow) spinesofwhich the withasquared-offtip. Severalfurrowspinesspacedalonglengthof
apiGcoanlompoostreiss lnonogtesotc.cNurorisnugbooranltshpeineosr.al surface and cannot be tohfebfoutrhrotwh,ewhiotlhotbiyfpiedatinp.dOpraarlatpylpatees1.anTdhesppianreastayrpees2imiislaurnitofotrhmolsye
lightgrey incolour.
distinguished aborally.
HABITAT. The holotype and paratype 1 were collected on 4.5.87,
COLOUR. Driedholotypeisauniform,pale 'museum'buffcolour. 0.5km. southeastofWadiHaartandabout4km.northeastofSadh
Colourinlife is notrecorded. village. These were collected, together with 'Asterina' cepheus
intertidallyonagentlyshelvingexposedrockyshorewithtidepools
Paratype 1. BMNH 1997.1017 has R=19.0mm, r=7.9mm. justbelowtheleveloftheconspicousbarnacleTetraclitasquamosa
134 A.C.CAMPBELLANDF.W.E.ROWE
Fig.4 a,ScanningelectronmicrographoftheabactinialsurfaceofPatihellaparadoxafromWadiHaart,Sadh,Dhofar,SouthernOman. Scalebar: 5mm;
b,ScanningelectronmicrographoftheactinialsurfaceofPatiriellaparadoxafromWadiHaart,Sadh,Dhofar.SouthernOman.Scalebar: 5mm.
rufotincta.Duringthemonsoonperiod,July-September,themiddle ofDhofar, southern Oman.
shoreisrichlycloakedwiththegreenalgaUlvasp.andbrownalgae Remarks. Basedonarrangementandshapeofskeletalplatesand
developonthelowershore.ThesegrowthsareburntoffbyDecem-
theirarmament,paradoxaiswithoutdoubtcongenericwithPatiriella
ber, and then the intertidal remains almost alga free until the next
south west monsoon. It is worth noting that perennial beds ofthe regularis,thetype speciesofPatiriella. Itdiffersfromthatspecies,
kelpEcklonia radiatahavebeenrecordedoffSadhhead(Barrattet aswiththemajorityofitscongenersintheformoftheradial 'field'
ofabactinalplates,thehighnumberofpapulaeperpapularareaand
aElc.k,lo1n9i8a6)maaypparcotxuiamllayteolcycu5rmkumc.htcolotsheerassouftrhagwmeesnttsowfertheisfosuitned. absence ofsuboral spines. The absence ofsuboral spines is shared
washed upon thebeach. with four species from the southern Australian coast. Ofthese P.
Paratype 2 was collected on 5.12.86 at Raaha 2.5 km. west of pannvipara is a small, precociously viviparous, pentagonal, cush-
WadiAynat8mdepthonrocksamongstcorals.Thissitefacedsouth ion-shaped star; P. brevispina and gunni have six, non-projecting
rays,andaremoreorlesscushion-shapedandhexagonalinoutline.
southeastandcomprisedasandycoveborderedtotheeastbyaridge
ofmetamorphic rockslopingdownto sandat 10m. Therockridge Additionally,these speciesdifferfromP.paradoxaintheincreased
frequencyoftwospinesoneachoftheproximalactinalintermediate
was well covered with many scleractinian colonies, especially
plates, and gunni possesses two subambulacral spines per
Agcarrdoepno'rabespc.amDuericnogmptlheeteslouythovweersgtrmoownnsowiotnhpetrhieodbrthoiwsn'caolrgaal adambulacral plate. P. paradoxa may appear to be most closely
related to P. calcar, differing most obviously in having a more
Sgarrogwatshssohpasidsbzraonkaerndiunpi.aAntdtdhiespteirmseedo.fNthoeEccokllleocntiiaonratdhieaSt.azwaanasrsdeienni delicateabactinalplating andarmamentandhaving5 insteadof7-
growing inthe immediate vicinity. 11 shortrays. Clearlythe geographical isolation ofparadoxa from
its congeners has resulted in the evolution of a combination of
Distribution. Known only from the type localities on the coast characters whichisolates itwithin thegenus.
A NEW SPECIES OFPATIRIELLA 135
ZOOGEOGRAPHICAL CONSIDERATIONS. thoughnotestablisheditselfonSt.Helenawaswashedashorethere.
A.M. Clark (1992, in A.M. Clark and Downey) considered this a
reasonablesuppositionsinceexiguaisnotrecordedfromAscension
ThegenusPatiriella,asacceptedherein,isdistributedpredominently Island,tothenorthofSt.Helenawherethecurrentisfromtheeast.
intemperateseas.Nofewerthan 1 ofthe 15speciesincludedoccur The occurrence of Ecklonia radiata, otherwise known only from
in Australian waters (Rowe & Gates, 1995). Six of the species around the coasts of South Africa, Australia and New Zealand,
(brevispina, calcar, gunni, inornata, parvivipara and vivipara) are whichhasbeenrecruitedtothe southeasterncoastofArabiaviathe
endemictoSouthernAustralia.TwospeciesrangeacrosstheTasman deepAntarticcurrentfromthe south(Sheppard, 1992, inSheppard,
SeabetweensoutheasternAustraliaandNewZealand(regularis)or PriceandRoberts)mighthaveprovideda'raft'forPatiriellatoreach
Lord Howe Island and Kermadec Islands (oliveri). One species the Dhofar coast, originating either from South Africa or the
(pseudoexigua) is essentially tropical, ranging from northeastern Patiriella-species-rich southern coast of Australia. However, such
AustralianorthtoJapan.ThesomewhatubiquitousP. exiguaranges 'rafting' or 'accidental' introductions tend only to extend species
fromsouthernAustralia,westwardacrossthesouthernIndianOcean range, as it has done with Ecklonia. To seek a solution here for
to St. Helena Island offsouthwestern South Africa in the southern Patiriella requires invocation ofthe subsequent evolution of the
Atlantic. Ofthe otherspecies, dyschta isendemic to South Africa; species P. paradoxa and extinction of its ancestor on the coast of
calcarata is endemic to Juan Fernandez Islands; chilensis occurs Dhofar. Once again, the genetic and geographic isolation of P.
betweenChileandPeruand,fimbriate/ isdistributedfrom southern paradoxa would not appear to support such an arguement of its
Chile tothe Falkland-Magellan areaand southernArgentina(A.M. origin on the Dhofar coast, even from its geographically nearest
Clark, 1993). With the exception offimbriate/ which has a known congeners (see above).
depth range from intertidal to c. 300m, species of Patiriella are The lack of fossil history of the family Asterinidae does not
essentially intertidal, occurring at most to about 30m depth (A.M. preclude ancient history. It may be more productive, therefore to
Clark, 1993). seek a linkage between the distribution of Patiriella (particularly
The occurrence ofa species ofPatiriella isolated on the Dhofar considering its very close relationship with Asterina s.s., from the
coast of Oman, in the tropical, northwestern Indian Ocean, is Atlantic,andPatiria,fromtheNorthPacific)andvicarienteventsin
difficulttoexplain;whetherastheresultofdistributive,accidentalor theIndianOcean.Theoceanographicandgeologicalconfigurations
vicariant events. oftheareaappearstohavebeenrelatively stableforatleastthe last
To seekexplanation by adistributive means requires knowledge 15-10 my (Powell etal., 1981;Adams 1981).
ofreproductive strategieswithin the genus. Unfortunately, we have Coincident with this time the complete opening ofDrake's Pas-
been unable to determine reproductive strategy in P. paradoxa sage (25-15 mya) established the circum-Antarctic current and a
through examination of the gonads, since the three specimens sharp drop occurred in surface and bottom sea-water temperatures
collected todatewere preservedanddried. Since gonoporesdo not (vanAndel, 1981). Itcanbeconcurredthatthepresent-dayareasof
occurontheoralsurface(seep. 133),anditisclearlynotviviparous, upwelling, including those within the Indian Ocean were also
then we assume aboral gonopores occur in P.paradoxa and the establishedatthattime.This isofinterestfortworeasons. Firstly,a
strategy involves either planktotrophic or lecithotrophic larvae. major area ofupwelling is known offthe coast ofDhofar (fig. 2).
However, life historiesofat least seven speciesofPatiriellaoccur- This produces turbulent, nutrient-rich surface waters and almost
ring in Australia, including P. regularis which also occurs in New temperate conditions (minimum recorded water temperature of
Zealand have been determined (Byrne, 1991: 1992; Byrne and 15.9°CnearSadh;Savidge,etal., 1986)whichprevailinthecoastal
Barker, 1991).Ofthese,regularisexhibitsanindirect/planktotrophic region of Dhofar for at least 4 months of the year (June-mid
developmental pattern with feeding bipinnaria and brachiolaria September) (seeCurrieetal., 1973;Campbell and Morrison, 1988;
larvae; gunni, calcar, pseudoexigua exhibit a direct/lecithotrophic Millerand Morris, 1988 fordetails) and this is coincident with the
developmental pattern with planktonic non-feeding brachiolaria knowndistributionofP.paradoxa.Secondly,thegeneraltemperate-
larvae; exigua exhibits direct/lecithotrophic developmental pattern water distribution of species of Patiriella (as included herein),
with a benthic non-feeding brachiolaria larva; vivipara and Asterina s.s. (including only species gibbosa, phylactica, stellifera
parvivipara exhibit a direct/viviparous pattern of development as andpossiblypancera;accordingtoFWER,unpublished)andPatiria
intra-ovarian brooders, without larvae. The occurrence on the the (including speciesminiata, pectinifera andpossiblyminor,accord-
DhofarcoastofOmanofPatiriellaoriginatingvialarvaldistribution ing to FWER, unpublished), which appear (with the exceptions of
fromeithersouthernAfricaortheAustralasian region,even though Patiriella pseudoexigua and Asterina stellifera along the tropical
thenearestcongenersareP.dyscrita(S.Africa)andP.pseudoexigua westcoast ofAfrica, part ofits range) not to extend into locations
(recorded as P. exigua by Koehler, 1910), from the northeastern much,ifatall,abovethe20°Cisotherm(distributiondatatakenfrom
Indian Ocean, is difficult to envisage. The present-day water cur- A.M. Clark, 1993). The implication ofthe present-day distribution
rentsoftheIndianOceanmusthavebeenestablishedforatleastthe pattern ofthese three genera is that theirancestorwas more wide-
last 15-10my,followingseparationoftheIndianOcean(seeAdams, spread in cooler parts ofthe Tethyan system (possibly during the
1981;vanAndel, 1981).TheisolationofP.paradoxa,ontheDhofar later part ofthe Oligocene epoch (c. 40-25 mya) (see van Andel,
coastsuggestsagenetic isolation which is notreceivinginputfrom 1981)) and before its closure, following which eventthe structural
otherparts ofthe generic range. differencesrecognisedin separating thethreegenerawould appear
Anexplanationoftheoriginofthetemperate-watergenusPatiriella to have evolved in the fairly discrete geographical isolation which
onthetropicalOmanicoastinassociationwithasecondaryagentis. occurred between them. Although the distribution of its congener
however, not at first sight, unreasonable to propose. For instance, pseudoexigua across the tropics from northeastern Australia to
Dartnall (1969a) considered the New Zealand species P. regularis southern Japan is somewhat confounding, the isolated, endemic
hadbeenintroducedintoTasmanianwatersamongstoysterspat.The occurrenceofP. paradoxaon the southernArabian coast might be
distributionofP. exiguafromsouthernAfricantoSt. HelenaIsland, explainedintermsofitsbeingarelic.Thisisallthemorelikelydue
in the south Atlantic, has been attributed, by Mortensen (1933) to totheinfluenceoflocalseasonalupwelling,providingmoretemper-
probable transport on the holdfasts of the kelp Ecklonia, which ateconditions,suitableforthegenus,atleastforpartoftheyear,the
136 A.C.CAMPBELLANDF.W.E. ROWE
speciesclearlyhavingevolvedto surviveyear-roundconditions on Zeitzschel,B(Ed.)TheBiologyoftheIndianOcean.Springer-Verlag,pp37-52.
thecoastinthistropicalpartoftheworld.Upwellingalongthewest Dartnall.A.J.1969a.NewZealandseastarsinTasmania.PapersandProceedingsofthe
coast of Africa may well account for the extension of Asterina DarRtonyalall.SAo.cJi.et1y96o9fb.TaAsmvainviiap,ar1ou0s3:s5p3e-c5i5e.sofPatiriella(Asteroidea:Asterinidae)from
stelliferaintomoretropicalregionsinthewesternAtlanticpartofits Tasmania.ProceedingsoftheLinneanSocietyofNewSouth Wales.93: 294—296.
distribution. It will be ofinterest now to investigate whether other Dartnall.A.J.1971.AustralianseastarsofthegenusPatiriella(Asteroidea:Asterinidae).
shallowtemperate-waterechinoderms(otherthanthegloballyubiq- ProceedingsoftheLinneanSocietyofNewSouth Wales,96:39^19.
uitousophiuroid,Amphipholissquamata)(seePrice, 1982)orother Domantay, J.S.& Acosta, T.E. 1970. The littoral echinoderm fauna of Ilocos Sur
betweenCandonandVigan.ActaManilla(A)5(10):49—103.
invertebratetaxa(seeBarrattetal, 1984)mightbefoundtooccurin Fisher, W.K. 1913. New Starfishes from the Philippine Islands, Celebes and the
theDhofarregion,whichmightsupportthisthesis,particularlysince Moluccas.Proceedingsofthe UnitedStatesNationalMuseum46:201-224.
no other temperate-water distributed taxa appear to have been Fisher.W.K. 1917. Anewgenus andsubgenusofEast-Indian sea-stars. Annalsand
recordedfromthe area. MagazineofNaturalHistory, 20:172-173.
Fisher,W.K. 1919.StarfishesofthePhillipineseasandadjacentwaters.Bulletinofthe
UnitedStatesNationalMuseum(100)3:1-547.
Gray.J.E. 1840.AsynopsisofthegeneraandspeciesoftheclassHypostoma(Asterias
Acknowledgements. A.C.Cgratefully acknowledgesthediving,field Linnaeus).AnnalsandMagazineofNaturalHistory, 6:275-290.
andlaboratorysupportgivenbyBrianCarnell,PaulFletcher,MikeMorrison, Hayashi, R. 1940. Contributions to the classification ofthe sea-stars of Japan. I.
RobertWhitcombe,andtheBiologyDepartmentofSultanQaboosUniver- Spinulosa. Journal ofthe Faculty ofScience ofHokkaido Imperial Univiversity,
Zoology7:107-204.
sity.ThefieldworkwasfinancedwithagrantfromSultanQaboosUniversity, Hayashi, R. 1977. A new sea star of Asterina from Japan, Asterinapseudoexigua
Muscat,SultanateofOman. pacifican.ssp.ProceedingsoftheJapaneseSocietyforSystematicZoology, 13:88-
We also wish to thank two unnamed referees for their valuable and 91.
constructivecriticismsofthemanuscript.Anyremainingerrorsarethesole Keough.M.J.&Dartnall.A.J. 1978.Anewspeciesofviviparousasterinidasteroidfrom
responsibilityoftheauthors. Eyre Peninsula, South Australia. Records ofthe South Australian Museum,
17(28):407^116.
Koehler. R. 1910. Shallow-water Asteroidea. Echinoderms of the Indian Museum.
Calcutta.
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