A、sEriEs oF rEsEArCh projECts in rECEnt yEArs hAvE lookED At thE smAll, spiny, mArinE invErtEBrAtE known As thE sEA urChin. thE sEquEnCE oF thEir gEnEtiC CoDE hAs BEEn suCCEssFully AnAlyzED, rEvEAling A rEmArkABly ClosE rEsEmBlAnCE to thAt oF humAns. this proviDEs A FirmEr FounDAtion For thE ClAim thAt humAns AnD sEA urChins shArE A Common AnCEstor, whiCh must hAvE livED ovEr 540 million yEArs Ago.
thE rED sEA urChin, FounD oFF thE wEst CoAst oF northAmEriCA AnD ElsEwhErE, wAs ConsiDErED A pEst in thE 1960s AnD AttEmpts wErE mADE to ErADiCAtE thEm whErEvEr loCAls wErE FArming kElp. in thE 1970s, though,AmEriCAn sEA FishEriEs DisCovErED A luCrAtivE mArkEt in jApAn, whErE CErtAin intErnAl orgAns oF thEsE CrEAturEs wErE ConsiDErED A DEliCACy, AnD By thE 1990s thEy hAD BEComE onE oF thE most vAluABlE mArinE rEsourCEs.
thErE ArE impliCAtions For thEsE FishEriEs in thE lAtEst FinDings ABout thE wAy sEA urChins mAturE. not only ArE thE invErtEBrAtEs CApABlE oF rEAChing An AgE oF 200 yEArs or morE, But thEy Also show no signs oF AgE-rElAtED DEgEnErAtion. in FACt, thE morE ADvAnCED thE AgE oF An urChin is, thE morE EnhAnCED its powErs oF rEproDuCtion sEEm to BE. on thE othEr hAnD, populAtion growth is limitED DuE to thE EAsE with whiCh juvEnilE urChins FAll prEy to A rAngE oF EnvironmEntAl thrEAts.
stuDiEs hAvE Also lookED At growth rAtEs, using mEAsurEs oF CArBon-14, whiCh hAs inCrEAsED in All living orgAnisms Following thE AtmosphEriC tEsting oF AtomiC wEApons in thE 1950s. thEsE stuDiEs ConFirmED EArliEr FinDings, oBtAinED using injECtions oF tEtrACyClinE, thAt thE proCEss oF EnlArgEmEnt nEvEr rEAChEs A CEiling. growth rAtEs mAy Diminish to only An ExtrA millimEtEr in CirCumFErEnCE pEr yEAr But thEy Do not CEAsE.
sEA urChins thAt hAvE livED For A vEry long timE______
A、losE thEir ABility to rEproDuCE
B、Do not suFFEr From thE EFFECts oF AgEing
C、stArt to show A slight rEDuCtion in sizE
D、ArE morE EAsily AttACkED By othEr mArinE AnimAls