Uhlobo lweChord: isakhiwo kunye nophuhliso lwe-lancelet

Ukuphuhliswa kwe-lancelet kunye nesimo sayo esifaneleko sahlala sisimfihlakalo ixesha elide. Ngoku izazinzulu ziyazi kakuhle ukuba lo mmeli weChordovye udidi oluphuhlisiweyo.

Uhlobo oluqhelekileyo lohlobo lweChord

Iintlanzi, i-amphibians, izilwanyana ezinwabuzelayo, iintaka, izilwanyana - zonke ezi zilwanyana zimeli zohlobo lweChordovye. Yintoni edibanisa izinto ezinjalo ezahlukeneyo? Kuvela ukuba bonke banesicwangciso sobume esifanayo.

Kwisiseko somzimba wabo i- axial squke, ebizwa ngokuba yi-chord. I-lancelet igcina kuyo ubomi. I-tube ye-nervous ilapha ngaphezu kweqhosha. Kwimeko ye-metamorphosis, kubaninzi abamele uhlobo oluvela kulo, intambo yomgogodla kunye nengqondo. Ngaphantsi kwe-squaxial axial is intestine, ebonakala ngathi ityhubhu. Emqaleni wezinto ezikhethiweyo kukho i-gill slits. Kwizilwanyana ezihlala emanzini, le nto iyaqhubeka, ngelixa iindawo zasemhlabeni zibonakalisa kuphela ukuphuhliswa kwe-embryonic.

Imbali yokufumanisa i-lancelet

Kutheni ukuphuhliswa kwe-lancelet ixesha elide kuninzi kunye neengxaki? Inyaniso kukuba ixesha elide libhekwa njenge-mollusk. I-lancet (ifoto engezansi ibonisa isakhiwo sayo sangaphandle) iyakhumbuza ngokwenene ezi zilwanyana. Unomzimba onothileyo kwaye uphila kwindawo yendalo yamanzi - kwiindawo eziselwandle nolwandle. Kodwa iimpawu ezibonakalayo zentlangano yangaphakathi zenze ukuba bakwazi ukwahlukanisa kwiyunithi ehlukileyo.

Ukongezelela, ngenxa yemisebenzi kaPeter Pallas noAlesandria Kovalevsky kwaqulunqwa ukuba ezi zilwanyana ziyizintlu zamathambo. Iingcali zenzululwazi zibiza ezi zinto ziphilayo. Kukholelwa ukuba i-lancelet ayizange iguquke, ekubeni ihambelane ngokufanelekileyo neendawo zokuphila ngaphandle kokuncintisana.

Izixhobo zesakhiwo sangaphandle

Ngenxa yesimo somzimba, eli silwanyana linalo igama elingavamile - i-lancelet. Isithomboniso sibonisa ukuba le mzimba ifana nesixhobo sokugqirha esidala, esibukhali kumacala omabini. Kubizwa ngokuba yi-lancet. Ukufana kufanekisela ngokucacileyo iimpawu zesakhiwo sangaphandle.

Umzimba we-lancelet ufinyelela kwi-8 cm ubude ubude. Ucinywe ukusuka kumacala kwaye ubhekise kwiziphelo. Ngakolunye uhlangothi, ubude obude bomzimba bubumba iimfesane - i-dorsal and caudal. Ekupheleni komzimba, i-lancelet ingcwatywa entlabathi. Ekubeni kukho i-pre-funnel, ijikelezwe yimizila.

Skeleton kunye nemisundu

Uphuhliso lwe-lancelet lubonakaliswe ngokulondolozwa kweqhosha kulo lonke ubomi bakhe. Ngefom ye-strand, ityula lonke umzimba ukusuka phambili ukuya ekupheleni. Kwimacala omabini e-chord afumaneke kwiimisipha. Esi sakhiwo sendlela yokuhlawula ivumela ukuba i-lancet ihambe ngokuzenzekelayo. Ukwahlukana kwezihlunu kuholele ekuguquleni komzimba, kwaye ngoncedo lweqhosha lilungiswe.

Isakhiwo sangaphakathi

Iziko ze-lancelet zakha zonke iinkqubo zobomi. I-digestive imelwa ngumlomo, i-pharynx kunye nomathumbu we-tubular ene-hepatic outgrowth, ekhonza njengengqungquthela. Ngokwehlobo lokutya, i-lancelet yi-heterotrophic filterers. Le nkqubo inxulumene nokuphefumla, okwenziwa ngamagidi kunye nomhlaba wonke womzimba.

Amalungu amancinci nawo avulekileyo kwinqanaba le-okolocal. Bamelelwa ngama-tubini amaninzi-nephridia. I-system yegazi ye- lancelet ayivumelekanga. Iqukethe izitya zomzimba nezisu.

Izitho zozalana ze-lancelet zibizwa ngokuba yi-gonads. Ezi zi-glands ezibiniweyo, inani lalo lifikelela kuma-25. Ngoko ke, bahlakulela ii-ovaries okanye ii-testes. Ezi zilwanyana azinazo zokuzala. Ngoko ke, iiseli zingena kwi-perigastric cavity xa iindonga zegonads okanye zomzimba ziphuka.

Ukuvelisa nokuphuhliswa

Izitho zozalana zamathambo zibonelela ngokuchumisa ngaphandle. AmaGetetes akhululwa emanzini, apho adibanisa khona. Abafazi bayaphuma emva kokushona kwelanga kuzo zonke iinyanga, ngaphandle kwebusika. Iiseli zabo zesini ziqulethe i-yolk encinane kwaye zibonakaliswe ngamancinci amancinci - malunga ne-100 microns.

Ngaphambi kokuba kuqaliswe ukuqhubela phambili, iziqulatho zeeqanda ze-lancelet zahlula kwiintlobo ezintathu zentsholongwane: i- ecto-, i-meso-, ne-endoderm. Kwixesha leenkomfa ezalandelayo, ngalinye liyifom kwinkqubo ehambelanayo yezitho.

Ukuphuhliswa kwe-lancelet kunika ingcamango yeempawu zale nkqubo kwiingqinamba. Iqulethwe ngenani leenkqubo ezilandelelanayo: ukuchumisa, ukuchotshoza, isisu kunye ne-neurulation, organogenesis. Iindidi ze-lancelet, kunye nokuphuhliswa kwazo phambili, zihlobene ngokuthe ngqo kumanzi. I-larva ivela kwiqanda elichumisiweyo ngaphakathi kweentsuku ezi-4-5. Inokulingana ukuya kuma-5 mm kwaye ikhululeka ngokukhululekile kwikholamu yamanzi ngenxa ye-cilia eninzi. Isigaba sokurhaxa sihlala malunga neenyanga ezi-3. Ebusuku, ikhuphukela phezulu emanzini, kwaye ngomhla ekuthiwa kuwo.

I-Amphi-oxides yinto ebizwa ngokuthi i-giant lancet izibungu, eziyinto ebonakalayo yezilwanyana. Ekuqaleni bathatyathwa ngabantu abadala. Kodwa ekuhambeni kwezifundo ezininzi kwaqulunqwa ukuba bahlala kuphela emanzini kwiplankton. Ii-Amphi-oxides, ezinokufikelela kwi-11 mm, zigcine zonke iimpawu zesakhiwo se-larval. Umzimba wabo uhlanganiswe ne-cilia, iintambo zomlomo, i-cirbranchial cavity kunye neengqungquthela zesondo aziqulunqwa.

Ngoko ke, i-lancelets ziyizixhobo zokuhlaselwa kolwandle. Baye kwi-subtype ye-Cranial, iClassi. I-Lancets zibonakaliswa ngukuphila ngendlela yokuhlala, kuba zizilwanyana ezinobungozi kunye nochumiso lwangaphandle kunye noluhlobo olungacacileyo lwentlalo.