Lapho inkathi yeSilurian ihamba eMhlabeni (kusuka eminyakeni engama-440 kuya kwengama-420 edlule), izidalwa eziningi ezingaphansi kwamanzi zavela kakhulu. Amagilethi abo aguqukile kakhulu: kusuka kumasongo ajwayelekile, aphenduka ama-arcs amabili, aboshwe ngengxenye ye-articular. Lokhu kwashintsha kancane inqubo yokukhiqiza umoya-mpilo. Lapho-ke imithambo yomlomo yaqala ukuguquka. I-arch engenhla yahlangana nogebhezi, kwathi engezansi kwasala iselula yaphenduka umhlathi ophansi. Ngakho izidalwa zathola umlomo ogcwele. Ukuguqulwa okunjalo kuye kwenzeka kwezinhlanzi eziningi zasendulo, kufaka phakathi okhokho abade be-sterlet.
Lokhu kwaguqula izinhlobo zezilwane zaba izilwane ezidla izambane likapondo. Uma ngaphambili izidalwa ezingaphansi kwamanzi zaziphoqwa ukuba zizondle nge-plankton kanye ne-algae encane, ngoba abakwazanga ukuhlafuna ukudla okukhudlwana, ngemisipha eyakhiwe kahle babekwazi ukuklebhula nokugaya izingcezu ezinkulu. Ngenxa yalokhu, ukudla kwezidalwa okunjalo kukhule kakhulu futhi kwagcwaliswa futhi ngezinhlanzi ezincane.
Kumele kuqondwe ukuthi okhokho bokuqala, ababephila eminyakeni eyizigidi ezingama-400 edlule, babehlukile ngaphandle kunesimanje. Ngeshwa, ososayensi abakwazi ukubona ukuthi babukeka kanjani. Kungenzeka ukuthi izinhlanzi zangalesosikhathi zazizinkulu futhi zazingahluka ngesakhiwo somzimba nangebala. Abantu bokuqala, abangaphandle okufanayo nesiqu sanamuhla, baqala ukuvela cishe eminyakeni eyizigidi eziyi-120 edlule.
Ngokuhamba kwesikhathi, lolu hlobo selufakazele ukuthi lungolunye lwezinhlanzi zegobolondo ezihlala njalo. Wasinda ngokuzethemba kunoma iyiphi inhlekelele yomhlaba, wakwazi ukuzivumelanisa nezimo zokushintsha kwesimo sezulu, futhi futhi uhlala ehambisana nezinye izinhlobo zokuphila.
Ukubukeka nezimpawu
I-Sterlet ingeyenhlanzi eyinqolobane. Akanayo i-vertebrae emzimbeni wakhe, futhi imisebenzi yawo iyathathelwa indawo amapuleti ahlala isikhathi eside asezinhlangothini. Isisekelo sesinqe siyisimo esibonakalayo, sibukeka ngamehlo engqondo enqunu kuma-spikes asatshalaliswa ngokulinganayo ngemuva. Ugebhezi lwamathambo kanye nesikhumba sabantu abadala kuqukethe i-cartilage.
Umlomo udonswa phambili kufana nomlomo wedada. Akunamazinyo emihlathini, kepha sibonga i-larynx enzima nomgodi omkhulu womlomo, ngisho nezicucu ezinkulu zigaywe kahle. Engxenyeni engezansi yomzimba kukhona isigaxa sokubhukuda esinokuxhumana nohlelo lokugaya ukudla. Phansi kwekhanda, ngaphansi kwesembozo esikhethekile, kukhona gill. Zinokuvula okuncane okuvumela umoya ukuba udlule.
I-sterlet inomzimba omude, ogobekile ezinhlangothini. Ikhanda selulelwe phambili futhi linezindebe eziphansi ezivikelwe. Ngaphansi kwekhanda kukhona izinzwa ezincane, okukhona kuzo ezinye izinhlobo zama-sturgeon.
Inhlanzi ihlukaniswe izigaba ezimbili ngokwesimo sekhanda: ngesizalo esibukhali kanye nesikhuhluthi. Abokuqala bazalwa ezimweni zemvelo. Abantu abane-snout flat bangavela futhi emizimbeni yamanzi, kepha abakwazi ukukhiqiza inzalo. Kuyathakazelisa ukuthi iningi labantu eliqhamuka ngesikhathi sokuzalela kokufakelwa libuye libe nesifuthufuthu.
Umzimba wenhlanzi ungwevu ngombala futhi unesisu esikhanyayo; umzimba umbozwe ngezikali ezifanayo nokubekeka ku-enamel yezinyo. Ekhanda kukhona amapuleti amathambo asebenza njengesivikelo. I-dorsal fin ayitholakali enkabeni yomhlane, kepha idluliselwe emsileni. Lesi sakamuva sinengxenye engenhla ende nephansi elifushane.
Ubukhulu obujwayelekile be-sterlet busuka kumamitha ayi-0,5, kepha ikakhulukazi abantu abakhulu bangakhula baye kumamitha ayi-1,4. Abesilisa nabesifazane bombala ofanayo, usayizi, nangaphandle akuhlukile.
I-Habitat - sitholakala kuphi isitembu?
ISterlet ihlala emifuleni ngokufinyelela olwandle noma emachibini. Zivame kakhulu kumaYenisei, eNyakatho Dvina nase-Ob. Baphinde batholakala emifuleni eminingi egelezela oLwandle Olumnyama, Azov naseCaspian. Ngaphezu kwalokho, i-sterlet ingene kwezinye izidumbu zamanzi sibonga umuntu owethule ukuze akhuphule inani labo. Njengamanje, iningi labantu lihlala kulezi zindawo ezilandelayo:
- isikole esikhulu sezinhlanzi sihlala maphakathi ne-Irtysh,
- I-Kuban ithathwa njengendawo yokuhlala eseningizimu impela yesitembu, inani elincane lalezi zinhlobo lihlala lapho, kodwa inani lazo liyanda kancane kancane,
- Eminyakeni yamuva nje, umfula i-Kama uhlanzwa kakhulu ngenxa yokuqothulwa kwamahlathi, yingakho izinhlanzi zasendaweni ziqale ukwanda ngentshiseko,
- izinto azihambi kahle ku-sterlet kwa-Sura: ngenxa yezimo ezingezinhle kakhulu, amanani abo ancipha kancane kancane,
- ku-Don and Urals lolu hlobo lwezinhlanzi lungumbala ongatholakali, ngokunokwenzeka, abanye abantu babhukuda lapha, kepha abaphili ngokuphelele,
- ukwandisa isibalo sabantu, ngobuciko baletha i-sterlet e-Amur, Oka, Neman nasePechora,
- izinhlanzi zivame kakhulu eYenisei, izikole eziningana ezinkulu zihlala lapho,
- Ob lolu hlobo luqala ukukhula, ngezikhathi ezithile lubamba iso lomuntu,
- I-sterlet yalethwa ngokukhethekile eDvina, kodwa isikhathi eside ayikwazanga ukuvela ngenxa yezimo zezulu ezibandayo.
Izinhlanzi zithanda ukuhlaliswa ezindaweni zokuhlala ezinomhlabathi noma ngaphansi kwesihlabathi, futhi zidinga namanzi ahlanzekile kakhulu. Abesilisa bachitha isikhathi sabo esiningi ekujuleni okuphakathi. Abesifazane bathanda ukucwila phansi.
Ngabe idlani i-sterlet?
Intsha idla i-plankton kanye nezinto ezincane zasemanzini. Ahamba ezansi futhi aqoqe ngomlomo konke angakudla. I-antennae etholakala emhlathini ongenhla futhi isebenza njengezinzwa zokuthola ukudla okwenzelwe ukuwasiza kulokhu.
Njengoba ukhula, ukudla kwezinhlanzi kushintsha kancane futhi kuya ngobulili. Njengoba abesilisa bebhukuda ekujuleni okuphakathi, badla izinhlanzi ezincane. Abesifazane, bachitha isikhathi sabo esiningi ezansi, badla izinambuzane zasolwandle, izibungu, ama-crustaceans amancane, namaqanda ezinye izinhlanzi.
Naphezu kweqiniso lokuthi i-sterlet ibhekwa njengezisulu, ikhetha ukukhetha inyamazane encane. Uhamba ayokuzingela ebusuku noma ebumnyameni.
Ngabe i-sterlet ihlala isikhathi esingakanani?
Isikhathi sokuphila se-sterlet isikhathi eside kakhulu uma siqhathaniswa nezinye izakhamuzi zasolwandle. Ngokwesilinganiso, ngaphansi kwezimo ezinhle, izinhlanzi zingaphila zize zifike eminyakeni engama-30. Ososayensi bakholelwa nokuthi abanye abantu bayakwazi ukufinyelela iminyaka engama-80. I-Sterlet ikhula futhi ikhula isikhathi eside. Umzimba wakhe ekugcineni wakheka iminyaka engama-5-7.
Izici zobuntu nendlela yokuphila
ISterlet isiphithiphithi esihlala ezindlini ezinamanzi ahlanzekile. Kwesinye isikhathi abantu bangaya olwandle, kepha ngaso sonke isikhathi babuye ngokushesha. Ngenkathi efudumele, inhlanzi ibhukuda emanzini angajulile, kodwa lapho kuqala isimo sezulu esibandayo isuka ogwini iye ekujuleni okuningana futhi ibheka imigodi nemifudlana ebusika. Izivakashi ezingamenywanga ngeke zimthole lapho, nezinhlanzi ziphephile.
Ebusika, i-sterlet ayisebenzi. Uchitha sonke isikhathi endaweni yokuphumula ayitholile, akahambi ngokuzingela. Umzimba wakhe uwela esimweni sokumiswa kopopayi, ngenxa yokuthi akadingi ukuthola ukudla njalo. Lapho kuqala intwasahlobo, lapho iqhwa phezu komfula lincibilika, abantu baqala ukuhamba kakhulu futhi bakhuphuke bayobheka phezulu.
Isakhiwo senhlalo
ISterlet ihlala emaphaketheni amakhulu, futhi isibalo sabantu ngabanye singaba ngamakhulu amaningana. Izinhlanzi ziqoqa ukudla ndawonye futhi zizame ukunakekela abancane. Mhlawumbe kungenxa yesakhiwo sezenhlalo esithuthukisiwe ukuthi le nhlobo ingagcinanga nje ngokunyamalala ebusweni bomhlaba, kodwa futhi yandisa nesibalo sabantu.
Lapho kufika isikhathi sasebusika, izinhlanzi zihlangene zibheke indawo lapho ungalindela khona ukubanda. Ngemuva kokuthola i-crevice efanelekile noma ikhefu elikhulu, i-sterlet iwela phansi kakhulu. Kwesinye isikhathi abantu abaningi kakhulu bangahlangana esigodini ngasikhathi sinye kangangokuba bangakwazi ngisho nokuhambisa amaphini ngokukhululeka. Lapho-ke izinhlanzi zicindezelwa ngokuqinile komunye nomunye, ziwela opopayi abasamisiwe futhi zingashukumi.