A NEW SPECIES OF AUSTRALOMEDUSA (CNIDARIA HYDRO ANTHOMEDUSAE) FROM A SALINE LAKE IN SOUTH-WESTERN WESTERN AUSTRALIA

2004·1.6 MB·English

by  Wolfgang Zeidler

RecordsoftheWesternAustralianMuseum22:109-113(2004).
A new species ofAustralomedusa (Cnidaria: Hydrozoa: Anthomedusae)
from a saline lake in south-western Western Australia
WolfgangZeidler’and Lisa-annGershwin^
’SouthAustralianMuseum,NorthTerrace,Adelaide,SouthAustralia,5000,Australia
^SchoolofMarineBiologyandAquaculture,JamesCookUniversityofNorthQueensland,
Townsville,Queensland.4811,Australia
Abstract-Australomedusa thromboUtessp.nov. isdescribed fromLakeClifton,
YalgorupNationalPark. Itisasmallmedusawithabellheight(BH)ofabout
1.5 mm. It differs from its only other congener, A. baylii, primarily in the
shapeand locationofthegonads,andinhavingonly3-5tentaclespercluster
(verses 5-9). Furthermore, in preserved specimens, the tentacle length is
relatively longer, about 75% BH, though this character tends to be highly
variableinmostmedusaspecies.
INTRODUCTION Salinity was measured using an ICI 302
Very little is known of the non-marine medusan conductivitymeter.
fauna of Australia. Despite extensive surveys of Sexesweredeterminedasfollows: gravidfemales
non-marine aquatichabitatsbyvariousresearchers, were identifiedby thepresenceofsphericaleggs or
medusae are rarely encountered. We suspect that lumpygonads.Maturemaleswereidentifiedonthe
this ispartly duetothedelicatenature ofmedusae, basisoffullgonads,whichweresmoothratherthan
which often do not survive collecting techniques lumpy. All specimens that could not be positively
used for other taxa, but we also suspect that non- identified as mature males or gravid females were
marinemedusaearegenuinelyraremAustralia. considered immature, though this category could
Only two genera have thus far been recorded conceivably include spawned specimens and
from Australian waters, the freshwater probably also includes a disproportionate number
cosmopolitangenus,Craspedacusta,andthesaltlake ofmales.
genus, Australomedusa. Craspedacusta tends to The holotype male, allotype female and some
inhabit artificial lakes and ponds and has been paratypes have been deposited in the Western
recorded from all states except Tasmania and the Australian Museum, Perth (WAM). Additional
Northern Territory. Australomedusa has only been paratypes have been deposited in the South
recorded three times, firstly from south-eastern AustralianMuseum,Adelaide(SAM).
South Australia, just south of Robe (Russell 1970), All of the material of A. baylii listed by Russell
secondly from the central coast of Victoria, near (1970, 1971), including the types, deposited in the
Inverloch (Russell 1971, Bayly 1973) and thirdly Natural History Museum, London, was examined
fromatrueestuarinesystem(theWerribee)westof byoneofus(L.G.)forcomparativepurposes.
Melbourne, Victoria (Neale and Bayly 1974). Only
onespecies,A. baylii,iscurrentlyrecognized. SYSTEMATICS
Inthis paperwedescribe anew species,collected
from Lake Clifton, a moderately saline lake in
FamilyAustralomedusidaeRussell,1970
Yalgorup National Park, south-western Western
Australia. Remarks
When Russell (1970) described Australomedusa
MATERIALSANDMETHODS baylii he characterized the family thus, "in view of
the multitentacularcharacter ofthe marginal bulbs
Specimens were collected using a hand held 500 the erection of a new family, the
pm mesh plankton net from among, and over, Australomedusidae, would be justified with the
thrombolites in about Im of water in Lake Clifton, diagnostic characters of the type genus
Yalgorup National Park, Western Australia. They Australomedusa." However, in his paper describing
were relaxed with MgCl and preserved in 10% for the females of A. baylii (Russell 1971) he
maldehyde/propyleneglycolsolution. reintroduced the family name as new only adding
110 W.Zeidler,L.Gershwin
"the occurrence of only two types of nematocyst edged,narrow. Ringcanalsamewidthas theradial
indicatesthatthemedusashouldbeplacedinanew canals. Each quadrantofbellmargintypically with
family, Australomedusidae, fam. nov.". Clearly the a single rudimentary interradial bulb or wart.
correct citation for the family is Russell 1970; not Velum very wide. Statocysts not observed
1971 as presumed by subsequent authors (e.g. (lacking?). Color: In life, the body is transparent
Dumont1994;BouillonandBoero2000). with a faintly greenish hue to the subumbrella;
tentacles are faintly reddish in the outer half; the
ocelliarebrightred.
GenusAustralornedusaRussell,1970
Descriptionofallotype(female)
Australomedusathrombolitessp.nov. Like holotype, except that the gonads on the
Figure 1 interradial walls of the manubrium appear lumpy
MaterialExamined with eggs. The lateral gonads do not appear to
containeggs. All tentaclebulbs withclusteroffour
Holotype tentacles.
Male (WAM Z13498), Lake Clifton, Yalgorup
WA
National Park, south-western [32°44.714'S, Variationfromholotypeandallotype
115°39.230'E], collected at the thrombolite Tentacle number: Variation in the number of
observationwalkway,near'CapeBouvard'winery, fentacles on each marginal bulb is summarized for
byW. ZeidlerandL.Gershwin, 10December2000. adult specimens in Table 1. Larger specimens tend
to have more tentacles per cluster, but this is not
Allotype constant; some smaller specimens have four-five,
Female (WAM Z13499), same collection data as while some larger specimens only have three, and
holotype. the number per cluster can vary in the same
specimen, although it is most often four. Only one
Paratypes specimen had three tentacles on all four clusters
11 males, 63 females, 31 juveniles, or specimens and only three specimens had five tentacles on all
of undeterminable sex (SAM H1330); 10 males, 74 four clusters. Similarly, the 62 juvenile specimens
females, 31 juveniles, or specimens of examined had 3-5 tentacles per cluster, seemingly
undeterminablesex(WAMZ13500);samecollection unrelated to size, although details of tentacle
dataasholotype. distribution for individual specimens were not
recorded.
Diagnosis Tentacle length: This varied from about 0.6x to
Australomedusawith3-5 tentaclespergroup;with 0.8xBH.
laterally flattened "gonads" in both sexes,
approximately 1/3, or less, the distance from the
stomachtothemargin. Table1 Number of tentacles on marginal bulbs for
adultspecimensofAustralomedusa thrombolites
Descriptionofholotype(male) sp.nov.examined.
Body spherical to globular, with a scattering of Numberof Numberoftentaclesoneach
minutenematocystwartsonthewholeexumbrellar females marginalbulb
surface. Stomach small, quadrate, tapering rapidly
to short, narrow, cylindrical manubrium with 113 4 4 4 4
simple mouth with four lips; attached directly to 3 3 4 4 4
subumbrellar surface. Main gonads on interradial 4 3 3 4 4
sides ofmanubrial wall; smoothly bulging. Lateral 1 3 3 3 4
gonads small, roundish, flattened out laterally and 61 53 43 43 43
barely protruding down into subumbrellar space; 2 5 5 4 4
located on proximal 1/4 or 1/3 of radial canals. 5 5 5 5 4
Tentaclebulbs four, perradial. Tentacles inclusters 3 5 5 5 5
ofthree(onlyonebulb)orfour;narrowandlacking
nematocysts proximally, thickened somewhat and Numberof
males
densely covered with nematocysts throughout
13 4 4 4 4
distal 2/3 to 3/4; typically held outward in a fan- 4 3 4 4 4
like fashion; about 3/4 bell height (BH) in length 1 3 3 4 4
when preserved. Ocelli, one per tentacle cluster, 1 3 3 3 4
located at thevery distalcenterofthe adaxial side. 2 5 4 4 4
Radial canals, four, perradial, straight, smooth- 1 5 5 4 4
NewspeciesofAustralomedusafromWesternAustralia 111
Figure1 Australomedusathrombolitessp.nov.A.Holotypemale,lateralandaboralview.B.Tentacularbulbofholotype.
C.Allotypefemale,lateralandaboralview.
Tentacle thickness; Some specimenshave slightly determined as females and the 22 specimens
thickened tentacles, particularly those without determined asmales,35 females (26%) and 9males
lateralgonads. (41%)werewithoutlateralgonads.
Nematocysts: The proportion of tentacle covered Locationoflateralgonads; Never locatedbeyond
by nematocysts is highly variable, ranging from proximal1/3ofradialcanalbutaresometimesvery
aboutthe distal 2/3 to aboutthe distal 7/8butcan closetotheapexinsomespecimens.
be almost totally covered in specimens with Interradial marginal warts; Most specimens have
thickenedtentacles. only one wart per interradius. Some have two, or
Presence of lateral gonads; Of the 138 specimens occasionally three,butneverin all oftheinterradii.
112 W.Zeidler,L.Gershwin
Only one specimen had four, but only in one combinesfeatures ofbothsexesofA. baylii.Second,
interradius. the SouthAustralian andVictorianpopulations are
geographically isolated from one another in inland
Typelocality saltlakesapproximately450kmapart,withsuitable
Lake Clifton, Yalgorup National Park, south- habitats in between, from which they are
western WA [32°44.714'S, 115°39.23'E]. Salinity at apparently absent. While studies of the more
timeofcollection=31.5ppt. common freshwater genus Craspedaciista have
demonstratedincredibledispersivecapability,there
are nonetheless several unique forms (see
Distribution Jankowski 2001), as may be the case for
Onlyknownfromthetypelocality.
Australomedusa.
On arecent field trip (7Feb 2002) we visited the
Etymology
type locality ofA. baylii (lake 12 of Bayly 1970) in
The specific name "thromholites" (pronounced ordertocollectfreshmaterial, withoutsuccess. The
"throm-bo-LITE-eez") is in reference to the small lake known locally as "Lake Wylie"
dominant life form in the lake, the Lake Clifton [37°16'48.2"S, 139°49'59.1"E] is located on the
Thromholites. KarinyapropertyjusteastofLakeEliza,nexttothe
Big Dip Conservation Park, about 17 kms south of
Remarks Robe. At the time of our study, the temperature
This species is similar to A. baylii Russell, 1970, was 22.5°C, the salinity 25.5 ppt, and a green algal
butdiffersinseveralkeycharacters. Eirst,whilethe bloom was apparent. We also sampled two other
femalesofA. thromboliteshaveeggsclusteredonthe lakes near the Karinya Homestead, an unnamed
manubrium as do the females of A. baylii, the lake [37°16'53.9''S, 139°50'E] across the track from
former possesses lateral gonads in both sexes, Lake Wylie, and one locally known as Lake Pudd
whereas theyare lackingin thefemales ofA. baylii. [37°17'20.3"S, 139°50'13.5"E], about 1 kmsouth-east
Second,thelateral"gonads"areofadifferentshape of Lake Wylie. No medusae were found in either
and location, being flattened laterally against the nearby lake, although both harbored diverse
subumbrella, and located about 1/3 the distance crustaceanandmolluscanfaunas.Thewaterofboth
away from the stomach inA. thrombolites, whereas lakes was clear, the temperature ofboth lakes was
in A. baylii they start out adjacent to the stomach 22.5°C, and the salinity was 32.0 ppt and 29.5 ppt,
and move to the distalhalfofthe radialcanal, and respectively.
theyarepouched downwardinto the subumbrellar Thus,intheabsenceoffreshmaterial,particularly
cavity. Third, thetentaclenumberineachclusteris ofboth sexes fromthe same locality, we areunable
only four (occasionally 3-5) in A. thrombolites, but toresolvewhetherornottheknownpopulationsof
typically six-seven (occasionally 5-9) in A. baylii. A.bayliirepresentthesamespecies.
Tentacle number is independent of body size in
both species, and is often unequal on the same
specimen. Tentacle length in preserved specimens ACKNOWLEGEMENTS
is about 75% BH for A. thrombolites, compared to We thank Environment Australia (ABRS grant
about 50% BH or less for A. baylii. Russell (1971) No. 20045) for funding the fieldwork and for
mentions the occurrence of two types of
providing funds for the second author to travel to
mniecmraotboacsiycstesuryftoerleAs.. Wbaeylilia,ckdedestmhoenfeacmielistiesantdo ADuesptraarltiam.enWte aolfso tChoannskerthveatWieosnternanAdustrLalainadn
examine the nematocysts of A. thrombolites in the Management for giving us permission to collect
field and obtained poor results with preserved specimens from localities under their jurisdiction.
material. Thus, comparison of this character will MsS. Halsey,NaturalHistoryMuseum,London,is
depend on the future examination of living
thanked for her hospitality and for providing the
material. second author access to the collections. This
research was completed while the senior author
was an Honorary Researcher with the South
DISCUSSION
AustralianMuseumandaVisitingResearchFellow
Twofactors,whichhavebecomeevidentfromthe in the Department of Environmental Biology,
comparison of A. thrombolites with A. baylii, raise UniversityofAdelaide.
the question of whether the South Australian and
Victorian populations of A. baylii are indeed the
samespecies. First, the twopopulationsofA. baylii REFERENCES
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NewspeciesofAustralomedusafromWesternAustralia 113
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