Prodromus of Hawaiian Water Bears Sixth-15-22

8/7/2019 Prodromus of Hawaiian Water Bears Sixth-15-22

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INTRODUCTIONThe b io t a of the Hawaiian i s l ands a t t r a c t sb io l og i s t s because of its d ive r s i t y . We have a l l cameto expec t new and exc i t ing th ings here ; new spec ie sbeing among the more engaging d i scove r i e s . We r epo r t

here a f i r s t gl impse of a fasc ina t ing phylum t h a t hasun t i l now passed gene ra l l y unnot iced in Hawaiianbio logy . The phylum i s Tard ig rada , comprised of smal l(50 to 1200 micron) c rea tu re s usua l ly ca l l ed waterbears because of t he i r appearance and de l i b e r a t e"pawing" form of locomot ion. They a re pa r t of themeiofauna ( l i t e r a l l y "sm all an im als") loose ly def inedas any mul t i ce l l u l a r organism below about 2 mm in bodyl ength .

I t i s genera l ly unknown among the s c i e n t i f i ccommunity in the Hawaiian i s la n d s , th a t t a rd igradespec i a l i s t s have examined Hawaiian specimens andi d en t i f i ed them. However, the most re ce nt c ata lo g ofworld t a rd ig rades (Ramazzot t i & Maucci l 1983) l i s t sonly f ive spec ie s from the Hawaiian a rch ipe lago:Bryocherus i n t e rmed ius f . hawai ica (Thul in , 1929) fromO'ahu, Echin iscus (?)perarmatus (Murray, 1907) fromO'ahu, E. sp inulosus (Doyere, 1840) from Hawai ' i , v i r idus (Murray, 1910) from Hawai ' i , and Macrobiotusc rass Idens (Murray, 1907) from O'ahu. All to ld , fewerthan 500 spec ie s of t a rd ig rades have been desc r ibed inthe world fauna.

The taxonomic pos i t i on of water bea rs has longbeen argued ( e . g . , Morgan & King, 1976) . They showsome fea tures of anne l idan -a r th ropodan metamerism, bu ta l so show aspec t s of embryological development andf i na l coelom s t r u c tu r e s more t yp i c a l of nematodes orbryozoans . Tardigrades a re f r e e - l i v i ng , and aqua t i c ,bu t usua l ly requ ire only the th in f i lm of waterassoc ia ted with mosses and o the r cryptogams, thehabi ta t f rom which the maj o r i ty 0 f the wor ld ' s spec ie shave been r epo r t ed . Marine forms can a lso be found incap i l l a ry water between gra ins of sand. Water bearsare genera l ly p lan t fe ede rs , p ie rc in g moss l e a f l e tce l l s and sucking the con ten t s by pharyngeal pumping.Some spec ie s prey on o the r smal l metazoans , l ikewisep i e rc ing and sucking the f l u id s of t he i r vic t ims .

MATERIALS AND METHODSTard ig rades were co l l ec t ed in the course of a

genera l survey of a rachn ids and assoc i a t ed ar thropodsof the Cen tra l C ra ter Di s t r i c t of Haleakala Nat iona lPark during Ju ly of 1985. Dry mosses and l i chens wereco l l ec t ed in p l a s t i c bags . Wet mosses w ere placed in

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70% e thanol . S lu r r i e s of moss, de t r i t u s and so i l froms tanding pools were f i l t e r ed through a 44 micronscreen , and the captured mate r i a l was placed in 70%e thanol . All samples were sen t to the BohartEntomology Museum a t the Unive rs i ty of Cal i fo rn ia a tDavis , where the t a rd igrades were i s o l a t ed and preparedusing methods desc r ibed in Horning, Schus te r andGrigar ick (1978). Representa t ive specimens were s l i demounted and photographed fo r t h i s presen ta t ion .Deta i led taxonomic work wi l l en t a i l prepa r ing specimensfo r Scanning Elec tron Microscopy (SEM) a t theUnivers i ty of Cal i fo rn ia .

RESULTSThir ty one spec ies of Tardigrada in 10 genera and

fou r f ami l i es were i d en t i f i ed to genus (Table 1 ).Among the specimens was a cosmopol i tan spec ies ,Milnesium tard igradum Doyere , a preda to r . Because of adea r t h of taxonomic spec i a l i s t s , and a poorunders tand ing of the sys tema t ic s and biogeography ofTard ig rada , it i s no t y et p oss ib le to determine whichof the Haleakala water bea r spec ie s a re new to sc i ence ,and which a re Hawai ian endemics . For example, some ofthe spec ie s co l l ec t ed resemble t hose known only fromsuch l o c a l i t i e s as Fin land , Tennessee , Cal i fo rn ia andSouth America.

The four f ami l i es of t a rd ig rades encountered inthe Maui sample a re E ch in isc id ae , M ilnes iidae ,Macrobiot idae and Hips ib i idae . The Echin isc idae a reeas i l y recognized by the p resence of do r s a l p l a t e s , TI1eMilnes idae a re be s t recognized by the presence of twocepha l ic c i r r i (whip- l ike sensory organs ) . Both theMacrobiot idae and H ip sib iid ae la ck cephal i c c i r r i , anda re d is t in gu ished by the pa t t e rns of t h e i r claws;Macrobiot idae with a 1-2-2-1 pa t t e rn , and Hips ib i idaeshowing a 2-1-2-1 pa t t e rn of c laws per foo t .

The number of spec ie s discovered by our b r i e fsurvey i s l a rge when compared to the fauna l d ive r s i t yof other l o ca l i t i e s . For example, Puerto Rico has 8spec i e s , the Galapagos i s l ands show 15 spec ies , theDominican Republ ic shows 16 spec ies , and New Zealand( inc luding both North and South I s land) shows 55spec ie s . The s t a t e of Cal i fo rn ia , which has rece ivedspec ia l a t t en t i on from t a rd igrade s p e c i a l i s t s , showsmore than 40 spec i e s . Pennack (1978) repor ted only 70spec ie s from the United Sta tes as a whole.

Type specim ens have been depos i ted a t the Bohar tEntomological Museum, Department of Entomology,Univers i ty of Cal i fo rn ia a t Davis .

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TAMLE 1: Pre l iminary Li s t of Tardigrada in the Cent ra lCra ter Dis t r i c t of Haleakala Nat ional Park, Maui,Hawaiian I s lands .FAMILY GENUS NUMBER OF SPECIES

Milnes i idae MilnesiumMacrobiot idae DactylobiotusMinibio tusMacrobiotusHypsib i idae DorYEhoribiusCalohYEsibiusDiaphasconHYEsibiusEchinisc idae Ec.hiniscus

( ar ct omy s g roup )(o the r groups)

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11152111

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DISCUSSION\There a re seve ra l reasons to be l ieve tha t theHaleakala sample i s not a complete represen ta t ion ofthe Hawaiian t a rd igrade fauna. Only suba lp ine anda lp ine hab i t a t s were sampled, with in an a rea of l e s s

than 50 square miles . No samples from we tte r n ativ eecosystems have been co l l ec ted . For the taxonomicgroups na t ive to the Hawaiian i s l ands , i s l and endemismi s the ru l e (Zimmerman 1948, Car lqu i s t , 1972) .Archipelago-wide d i s t r i bu t i ons a re the except ion . I fth a t p a t te rn appl ies to t a rd igrades , then the number ofwater bea rs found in the Hawaiian i s l ands may exceed100 spec ies . That would mean tha t Hawaiian spec ieswould represen t more than 20% of the presen t ly knownworld t a rd ig rade fauna . Even i f no f u r t h e r samplingwere conducted , the Maui sample represen ts the h ighes tknown d ive r s i t y of ta rd ig rades per un i t a rea on thep lane t . Why th i s should be the case i s an openques t ion .

I t is no t su rp r i s ing t h a t the Hawaiian wate r bea rshave escaped not ice fo r so long. Being microscopic ,they a re no t detec ted immediately in the f i e ld , bu tonly a f t e r ex t r ac t ion and prepara t ion in a l abora torys e t t i ng . However, l i ke o the r cryp t i c Hawaiian spec i e s ,such as cave sp ide r s , and f l i gh t l e s s , noc turna lc r i cke t s of boulde r beaches , the endemic Hawaiian waterbears of Haleakala a re the dominant spec ies of t he i rspec ia l i zed hab i t a t : pe r iod ica l ly wet , subalpinecryptogams.Anhydrobios is :

When the moss hab i t a t s of water bea rs undergodry ing , many spec ies of t a rd ig rades have the unusualab i l i t y to assume an i nac t i ve , r e s i s t a n t s t a t e ca l l edanhydrobios i s , l i t e r a l ly " l i f e wi thou t wate r" . Thisreduced, near ly dehydra ted s t a t e , may pe r s i s t fo rmonths or yea r s . In anhydrobios i s , wate r bea rs haver es i s t ed exper imenta l condi t ions inc lud ing s t rong br ineso lu t ions , and extremely low t empera tures (190 degreesC below zero) ( see review in Pennack, 1978) . One canhard ly th ink of a b io log i c a l s t a t e more conducive tosurv iv ing a long voyage over the sea , fo r example, inthe world ' s j e t s t reams.Vagi l i t y , Limit ing Habi ta t s and Endemism:

The g r e a t po t en t i a l vag i l i t y of water bea rs i sr e f l ec t ed in pa r t by the cosmopol i tan d i s t r i bu t i on ofthe "weedy" spec ies , Milnesium andMacrobiotus hufe l and i i . it does not fol low

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t h a t po t en t i a l vag i l i t y i s rea l i zed , and th e re a re manyspec ie s of t a rd igrades with l imi ted geograph ica ld i s t r i bu t i ons . We know nea r ly noth ing about thebio logy of Iillwaiian wate r bea r s , espec ia l ly w ith regardto t he i r ab i l i t y to compete with o the r organisms int he i r hab i t a t s . The pre l imina ry da t a from HaleakalaNat ional Park shows t ha t the d ive r s i t y oft a rd ig rade spec ie s were from hab i t a t s t h a t weredess i ca t ed much of the t ime: Rhacomitrium moss inunweathered ' a ' a above 'O i l i Pu 'u . I t i s veryi n t e r e s t i ng to add t h a t in Br i t a i n , Rhacomitrium mossesa re very t a rd igrade habi ta t -U10rgan and King,1976). This sugges ts t h a t Hawaiian t a rd ig rades mayhave been forced to sh i f t adapt ive ly to what waso the rwise an i napprop r i a t e hos t .

Permanent ly wet hab i t a t s (as the spr ing behindKapalaoa Cabin, or a t Waikane Spr ing in Kaupo Gap)genera l ly yie lded a subse t o f th e same spec ie s found inthe dry hab i t a t s , and were never among the r i c h e s ts i t e s . Water was evident ly not a l im i t ing f ac to r .In s t ead , th e lack of water might l im i t those organismsincapable of an hy dro bio sis , leav in g the water bearswith f re e re ign as the dominant spec i e s , sha r ing thehab i t a t with some very hardy nematodes, p ro t i s t s andbac t e r i a (which a lso a re capab le o f anhydrobios i s ) .

The impl ica t ion i s t h a t wet t e r hab i t a t s may notprove to be the r i ch es t fo r Hawaiian t a rd ig rades .Ins tead , hab i t a t s which a re water - l imi t ing to amajo ri ty of organ isms, may be the be s t niches fo rHawaiian spec i e s . In pa r t i cu l a r , we suspec t t h a t supra -a lp i n e , a lp ine and sub-a lp ine hab i t a t s of Mauna Kea,Mauna Loa, Huala la i and Haleakala wi l l each show t h e i rs e r i e s of endemic spec i e s . Analogous systems a t lowera l t i t ude s , fo r example , r ecen t lava flows dom in ate d byStereocaulon vu l can i , may prove to be r i ch water bea rhab i t a t s . Thus, the s e a - l eve l to summit a l t i t ud i n a lcoverage of both Haleakala and Hawai ' i VolcanoesNat ional Park prov ides an exce l l en t s e t t i ng fo rcont inued s tud ie s of t a rd igrades . In add i t ion , wesugges t t ha t b io log ica l ly water - l imi ted hab i t a t s suchas high-ac id Rhacomitrium bogs might a lso y ie ld af a sc ina t ing col l ec t ion- - of bea r s , probably with aunique assemblage of spec ie s not found in d r i e rs i t e s .

The s ign i f i cance of th e new t a rd igrade fauna l i e sin what they can teach LIS about seve ra l aspec t s ofevolu t ion in the Hawaiian s e t t i ng . They o f f e r a s tudyof h ab ita t s p ec ia liz at io n, of d ive r s i f i c a t i on whenre leased from compet i t ion o r preda t ion , and of the ro l eof vag i l i t y in d i s t r i bu t i on between and with in i s l and s .

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CONCLUSIONSThe f inding of 31 spec ies of T ard ig ra da in onesho r t so journ i s a promising ind ica t ion of the spec iesremaining on o th er is la nd s and o the r hab i t a t s . Bear in

mind t ha t the 31 spec ies rep resen t 6% of the knownworld fauna. The Cen tra l C ra te r Dis t r i c t of H aleakalaNat iona l Park a lready s tand s as the r i che s t s ing lel oca l i t y fo r Tardigrada on the p lane t . I t s uniques t a tus underscores the b io log ica l re source represen tedby the Nat ional Parks , and lends credence to theecosystem approach fo r spec ie s management ( fo r desp i t eour ignorance of the spec ies un t i l t h i s s tudy , theNat iona l Parks have served to p ro t ec t t he ir h a b ita ts ).The publ ic appeal t ha t water bea rs evoke may enhanceeduca t i on / i n te rp re ta t i on e f fo r t s in the parks . To showthe Mars- l ike environment of a lava f i e ld , coupled withthe almost ex t r a - t e r r e s t r i a l appearance of a water bea rmay be an e f f ec t i ve i n t roduc t i on to a world u ns een bythe casua l observer , bu t pro tec ted and preserved by theexi s t ence of a Nat ional Park .

ACKNm;rLEDGEMENTSThe authors wish to thank C. \.J. Smi th fo r encouragingthe research t ha t led to d iscovery of the t a rd ig rades ,and fo r the i den t i f i c a t i on of hos t cryptogams. TIlispaper was improved' by the comments and cr i t i c i sm ofWayne C. Gagne and Franci s G. Howar th .

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Prodromus of Hawaiian Water Bears Sixth-15-22