Studies of the eggs of Macrobiotus cf. pseudohufelandi (Tardigrada) from wheat fields in South Australia PDF
Preview Studies of the eggs of Macrobiotus cf. pseudohufelandi (Tardigrada) from wheat fields in South Australia
! IrmiMHW'tt.softhe Kmul S<>, n'lv •>{S, AlUtt\ EWH, I21t2). 51-5^ STUDIES OF THE ECIC.S OF MACROBIOTUS CF. PSEUDOHLIFEIANOI (TARDIORADA) FROM WHEAT FIELDS IN SOUTH AUSTRALIA by Ai an P. Bird* & Stlart G. McCuure Summary IMJMillnnnl.lAf.iel:ds&tnMcSuCuiihiuA\us.tSrtal.ia.i IfVWtf)fKStA'u,d,ieWs.olVi4htcttetg^1s2r1»<f-M'av5mtt-i3i7o-Ut?o0eMfa.yp.wi[hiWn.lmfrhmilitlfrrtltgrotfal ftwri The tardigrade. M>.nrohinlti\ el. pu'iiilt'httfclan-h, and its i*gg> were utoltdccj hoin -.oil Ihhh u wht'it! held fl! Avon hi South Australia during the whiterol' I99fr. The siulaccol LfaO &tigs WU* examined untlci Ihc scanning rhvimn iiiiciosiope and was bllWll L(l be highly ornamented ;iir<J icliculLite with nilniciOlls "inverted gohlel shaped'' pnijcelionv 'Ihi* iteiM*llc margins til' Ihc heads tit these pni|cctums consist ul clusters of uuniMikc j?lobules. Statistical analysis of Ihc si/e ItTihc projections revealed (wo significantly different IVpeU rtf BgJW in Tin- samples Examples ol onminentedeggs were tuimd in discarded exuvia. .1 condition wIikh is noi in accoid wiih .1tceenllv proposedhypothesi;-;on lantiyradeeg% evolution.Observationshh IVcdtnij behaviour, population density ande$G hiving habile ate presented. Kl \ WukOs: XUurnhiahis el pM-thlnhttjrhiihli microscopy nudit-radc-- fc£gS. inorpiiology. PVWlUllMIl- Sull Introduction lierlolam ct ui { ll)s>6> have shiLed lha( ornamented ci'i's arc iienerallv laid live in sod 01 water and 1.injigpulrs. ol*0 known .is water hears or mcv- smooth shelled ffgg* are laid in die moulted euliele piglets (Kinchin ISM4I. b&tOug U' a discrete phylum (euiviumi. fhe-e wmkers include the tannly M 11I cosmopolitan distribution Irom diverse h;il>iiat- Macrobioiidae. lo which c\\ (twuifohnfikttnii tucludnig murine. fresh wuitfl and semi-terresliinl bdoipK, in those lainilies dial lay tree, ornamented environment;-.. The uudigrades responsible foi the eggs. Berttdam ct ill. lllH.>6i have pin hwwaid an ;;•:*. lies*.I(hyd Ifl 11*I"- paper Wele identified a> hyp(>ihc--is in which ihe\' cvplain ihe evolution «>l \hta<>liit>(ns ef, p\i'H(l(>iitf{ef(tti(lt lharos l%o In S. tardigrade eggs. Claxton (Rifti Im%j ami are semi-lcncstrnif having In Uiis p<iper we examioe Ihe slruelure of Ihe et»e heen isolated from sand\ loam soil ill a wheat field at shell "I AY, cf, f>\ctt<t<>ltnf,kfinli and measure the Avon. South Australia. processes prolitiding Irom the stirlace ol ihe ugg The tardigrade egg ^tioH i--, a useful taxonomie shell.We alsodiscuss itsijgg layine hahits in relation eaiidc lo species identification, particularly ingenera ISS Ihc hvpoihcsis ol Bertokuu el til. ( L*>%) and kmii- such as HifiH tvbwtus where the shell is ornamented. menL o\) reedtne behaviour and population density, \Uh tahUnti.s cf. i>H-Uilninifi-(aiuii, which are only ubuuj 500 pin long by 150 pm wide when fully Materials nud Methods 'iimvti, l.iv comparatively large circular etigs which have highly ornamcnled relieululcd shell surfaces The lardigratles were colleelcd on 18 July |V96 with numeroitf "inverted ^nhlel-shaped" prujcctions from sandy loam soil and Irom Ihe same loculily at iHnd !'>%,». Avon. South Australia (latitude 34 14' S. lonyilude It has been sliown by Bertolani it Kebecchi 1 1^)3) 135S" 1^ B). as those collected prev'iously, using the thai dill'cieiiecs in ct^ shell morphology in sampling lechnii|tie described by Bird (W>oj. The Mfi< rohii/fus fmjt'linnh', previously thouuht to be due soil samples were collected in mid-winicr so that the |0 vaiiabihlv wifhin this species, fall inlo seven ilis- sues were wel *md the tai'digrades were feeding, lincl lypcs thai aiv tvlalcil lo clilfcjvnl animal mor reproducing and depositing eggs. photypes. Usin^ egg shell morphohigv. along with The lardigrudes and oihei tneiolauna, consisting olhci characlcrs.theseworXei-s havedescribeda num predominantly ofnematodes, were isolated from this Ivrofnew species from theA7. htifcfatldi croup, fees soil overa period ofthree days using a misting appa- (hat belong lo ihis uroup havw pitied or reiictilaicd ratus (Yeates & Bird l004>. Tardigrndes and nema shelf- with pi'otnidinv proccssi-s shaped like invened todes were counted and tardigrade eggs were picked goblets, chalices, thread spools 01 'Voolin^ UnveiV, oul usingu denial No. 3 ncnrc broach and examined. alive, in distilled water under a covershp. with the ; 11'liivloit) KWhlMileham S.AtiM. 3U62 light microscope Kggs to be examined under die ( SIU()LandiiikIW:iU-i, PMB 2t*ktiOsnmti.lS. AaM 5(l/vl. scanning electron microscope (SEW) were fixed in S"> A. F. BIRD & S. G. McCLURE **• *- r>. w« \ j • 2 1 RfiGS OPMACROMOTUS CR PSEUDOHUl^tANDt 5* &% gluteraldehyde in Sorensen's phosphate bufferai Although the pattern of die reticulations remains the pH 7.2 unci at -V C and kepi m this fixative for sev- same with the apc-nures on the reticulate surface of eral tlays. They were Ihen washed three times in dis- the egg shell being about 0.25 pm hi diameter (Fig. tilled waterand sonicated in an F.lma T420 sonieator hi, the shape of the protruding processes falls into Hi afrequency of35 kHz for 10 sec oruntil shown by tvvu distinct groups. Type I is shorter than Type H. ls microscopic observation to be free ofdebus. narrow at ihebase and has awidedistal head (Pig. 4). The eggs were frce/e-dried by placing them Conversely, Type II is taller, wider at the base and between membrane fillers which were frozen rapidly has a narrower distal head than Type I tfeg. 5). For by placing them in a slurry of freon cooled by liquid 10 processes of each type, the differences in ihe nitmgL-n. These fillers wilh the eggs were quickly means are statistically significant with V5% confi- transferred to a Irce/e drier and free/e-dricd at - 70: dence (Table 1 C. The dried eggs were picked up with double-sided When the proeesses weie examined mnWr the tape winch was ailaehed lo an ShM stub and coaled highermagnificationof the SPM (Fig. 0). Ihedentate wilh 30 mil ofgold. This material was examined and coe-shaped margins ofthe head were shown 10 con photographed in a Cambridge S 250 Mk 3 SPM sisi of clusters of globules with a structiue resem- operated at 20 kV using l7P4 Plus IIford roll film. bling madreporarian corals in appearance and were approximately 0.5 urn indiameter.The inudreporarian Results globules and reiieulated shell surfaces are similar in both the shell types described above. Nimther\ amiJtt't/ii)i> At die lime ofcollection the ratio oflardigrades Hi Discussion nematodes in 50 g of soil was 84:297. Heeding on nematodes was also observed during the course of Bertolnni vt ai i \99fr) have proposed An hypothe- this invesligalion and the nematodes held by the sis lo explain (he evolution of tardigrade eggs. taidigiades usually did flOl move although once- a According lo these workers, the eggs oflardigrades nematode broke \W<: and moved away. In one haveevolved asa a\sull oftwoevents, ihe fusl being instance, a tardigrade was observed to be arching its the acquisition of ornamentation and ihe second Ihe back in the manner of a scorpion, during feeding use of the shed exuviinn as the site for egg laying. activity wilh Ihe subsequent loss ol ornamentation.Thus, the ornamentedcge's ofthe Macrobiotidac are thought to /:,ee favin.K ami c,v/,'> Iv laid Uvc, Our obsctvalions that Ihe ornamented Uggs that wereabout 90-100fim in diameter in the eggs of M. ci\ iK\('H(i(>hii(flitniIi can citherbe laid in living unfixed state(fags |. l\ umi about 00-70jam in exnvia (Figs 1 . 2) iw free iPig.3)do not appearto be the fixed and dehydraied slale (fig. *)\ were laid in accordwith thishypothesis.Theexu\ia containing eilhci wiffiiti ryuvia («;as| eiiliclcM ifies L 2) or free ornariK-nied eggs were transparent and devoid of iPigi 3), figures 2, 3, 4. 5 clearly show thai these body eoiiteuh and did Hot appear to |v temalrs ilia' rges have a morphology of Ihe AY. luticlatnli group had tiled before completing <j^, laying. A possible wilh reticulated shells and characteristically explanalion forthe laying of(Ik egys in Iheexuviiun uptuincd-clialice-shaped proLiuding piocesses. by lite M. cT. i>s<'iuh>httfiLtti<li from the soil ai Avon. I Mil I P MiUMiwrnenh t)f tin- /in- t\{>v\ nf ftmiVXW* ITeftittlliiy, fl'rtH itn <y,y sinIf vttfmi* W VlacToblDUlf- I/, |isctulotiuietandi ( Typtt No. Height (uni) Basal width tUml OMal Width lUm) Mean + .SD Khih Mf:ni + SD Ranee Mead ± Sli K.in^i fl) 5_M ll.i S.440 4..S 2 3.*J 4X ,0-3.7 lo 0.4 0,4 s7 7-i 5,3 Qi 4,0 5 u I t I 2 -I i |0.'*-|>2.2r> .47 nw I IIS I6.n- s\) - Slumlord Potation, i = Sludenf* Pifi. I. Pi!U of<\tm>fltbut1us d ffsahlf>fntji.hmt_/i in east luncle (esuviuiiO. Arrows imlieaic position ul\.ist |eg> w\t\claws. Briulu field uplics. Scafe bar = HJO |un, lay, 2 S.miespecimen,u hiyhu m.mnilkMiii'nMiowinr 4kII punocutiii*IV)coveredIn cast cimkIc K'l. Brigid fieldopiie* Scale HW= -0 uiTti \. F. BIRD & S. G. McCLlIRE t*GGS OP MACM)ii?On;sc\- rsnuixvwrrfANDi $ is that thismay be an adaptation lo the hot, diy SUJU- huiJt in the Avon soil or there may be two different mers experienced there. species, neitherofwhich completely resembles those Our siudies on the lardigrades and nematodes in described so tar forthe hiijehuuh group tBet'lolani & soils from wheal fields al Avon in midwinter when Reheechi ($93: Biserov I996J- The reliculaled sur- the soils were wel and the populations o( the meio face of the shell and the structure of the globules on faunacouldbe expected to beat their peak, show thai the heads of ihe projections are similar in the two latdigrsdas make up a substantial component, forms ^y\' eggs described above but the diameter of although they are notas numerousasnematodes.The the apertures on the reticulated surface ol the egg ralioofK4 tardigradesto 2l)7 nematodes per50gsoil shell is much less than that shown in die eggs of found m theseexperimentsvariesat othersites where other members of the liufclaiirfi group described by the tardigrade numbers per 50 ti soil may be less and Bertolani & Rebeechi <IW>. Kinchin iW4i and nematode numbers greater (Bird l(»o). However, it Biserov ( 19%). To our knouledge, the glohules on is clear that the tardigrade presence al Avon is wide- the heads of Ihe projections have not been described spread, before and might prove, togetherwith the reticulated The lardigrades isolated Iron) soil at Avon feed on surface, to be useful laxonomic criteria if die hni^- nematodes and can survive hoi dry summers in an Id",h group »s further divided on the basis nf egg auhydrobiotie state (Bird 19% I heeding on nema- ornamentation. todes was also observed during the course oj this Clearly further siudies arc required on Ihe taxon- investigation and the nematodes fidd by the tardi- omy o! these lardigrades and on then"distribution in grades did not usually appear10 be moving,although the semi-arid agricultural areas ot South Australia ihey were coiled and therefore probably not dead, and oilier sinnlai nitons i\\ ihe Australian comment. .suggesting to us that they might have been paraly/ed by some type of injected narcotic. Since ihete is no inloiiiuilion on tardigrade diversity and geographical Acknowledgments diMribulion in South Australia, further studies are warranted- particularly on their leedmg habils, as Ihe sept61 author is grateful for a grant from the they may have a role in the bioeontrol ofthe parasitic Australian Biological Resources Study which pio- netnaiodts which have been shown to occur in the vided facilities that made this research possible MMi wheal lields ul Uon (Yeaies #: Bird IW>. rtJ CSIRO t.aud and WaterAdelaide \~n( aieommodu Tin* line ^iructure of lite egg $I1£|] Hi the fl&nuS lion and equipment, Dr W. R. Vlillei. Ueparimeni ol M(U'tttbinm.\ isofgreat uiMmounc imporlanee. From Biology Southwestern College Winfield Kansas oui observations on the uiirastriietiire of the egg USA and Dr W.I,. Nicholas. Department o\' Botany shells o\ (he Avon lardigrades. it would seem that and /oology AMI Canberra ACT are thanked loi thete may be two populations of M. el. ftstthfohuft' constructive criticism ofthe manuscript References Uruiol \\l. K, <V- Kililt'in. I . (IW.M A tvsUinn ol' Ihe HimNov.V Y. iIWfi) laiihgrndes ol ihi- ttiimyr peniitMilu Matminoltn hii(ri,ni<h croup (laixllgrada. with descriptions yj two new ^pteies. An>l 7 t.ht Stn Mnerobioiidaei. wilh some olwivalionson ih<*ia\oiiom- \\h 2\> 2H7. m tlmi;ii.lcr. ft eUtal'itunidev A-o/, <nri(>hi 22. 127 M Kincuim, I i P»w4i Ihe Uiology ol TaoligraUVV tV Ci moon. S. k. i \ty&\ Phylogcncltc sic iPorlluntl Pre: .. London), ttailniLiwii.Kc lt»i*ft,i_-piv<W-shlellis.variation in lardigrauYs. /<**!, J Yi.ot.s. I. \V tV Brno. -V I. ( PW-lt Sonic obNeivalton.s on Kiki),A- F ( 1*996)Studiesonlliesoil-jnluihilini: tardigrade. ilie inflaenee of agricultural practices on Ihe nematode Mtirrohi.KtiK cf. p\<-nil>>htifi-ttttuti, from Souih AuMraliu. faunae ol some Smilli Australian \oi!>. funtJtim A/tpt. Intits. ft .W. ZAitit 120. U7-I54. MmaHfl- n. IWUs, I'iji V Scanning elcelmn niicro«irjph ol whole L-L'gs ul Miu-rohhHits el. iwtuh>imf<'litntli showing lire inverted jJohM- shapeil pniju'eiioiisofTvpesttTI ) and if \'\'2\, Scale bar= 20pin. l-'in a. Seaniiiiii* eleelion inierogiaph of pari ot' the fcgg shell surface ofaType I e^y >Iiowiml' pro|fcrnnis wnh haiTowei Ivisesanil Uu^erdentate ecm-shaped heads Mom iho'-c olTvpe II. Not-.- similarly ivlieul;it«-Mj silrfticcsol vu)i shells. Sc;itc lxn - 3 mil % A. K BIRD & S- G McCLURE EGGS OFMACROBIOTUS GF. PSEUDOHUFELAND1 57 Fig. 5, Scanningelectronmicrograph ofpartoftheegg shell surfaceofaType II egg showingprojections with widerbases and smallercog-shapedheadsthanthoseofTypeI, Note similarly reticulatedegg shell surfaces. Scalebar= 5 jam. Fig. 6. Scanning electron micrograph of the head of one of the Type II projections at higher magnification showing the madrcporarianglobules(arrows). Notethesizeoftheapertures onthereticulated surfaceoftheeggshell on thetopright hand sideofthephotomicrograph. Scalebar= 1 um.
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