You might think fish were born swimmers. Not so, however.
When they hatch, fish larvae (幼虫) struggle to get around and to 1 . Some 99 percent of all fish mortality (死亡率) 2 in the larval stage. Only when they grow, do some fish get better at 3 enemies. Adults make quick getaways using a burst-and-coast (爆发并滑行) method in which they 4 a lot of speed quickly and then 5 . Many species don’t have this 6 at birth.
Scientists have long 7 that the lack of larval 8 prevented the little ones from gaining 9 force in the burst phase. And perhaps their very small size caused the water to act more like syrup (糖浆) 10 them, preventing a good coast.
11 a new study of zebrafish larvae 12 it’s their poorly devel oped side fins (鳍) and ineffective swim bladder that hold them back. They simply can’t 13 their bodies balanced. The finding might 14 other species, researchers say.
“Force can explain 15 of the poor swimming in larvae, but not all, and the difference in coasting ability cannot be explained by 16 in body length either,” said study leader, Ulrike Muller of Wageningen University in the Netherlands. “Many fish larvae hatch without fully 17 pectoral fins and all hatch 18 a swim bladder, so 19 problems could occur for them.”
Muller is 20 her findings today at the Society for Experimental Biology’s Annual Main Meeting in Canterbury.
1. A. swimB. surviveC. eatD. sleep
2. A. risesB. showsC. occursD. happens
3. A. attackingB. catchingC. attractingD. escaping
4. A. pickB. gainC. haveD. raise
5. A. glide awayB. jump awayC. put awayD. die away
6. A. ideaB. skillC. wayD. knowledge
7. A. insistedB. believedC. suggestedD. suspected
8. A. experienceB. weightC. heightD. size
9. A. muchB. someC. moreD. enough
10. A. againstB. withC. forD. to
11. A. HoweverB. AndC. ThereforeD. But
12. A. answersB. concludes C. suggestsD. proposes
13. A. getB. haveC. makeD. keep
14. A. apply toB. contribute to C. refer toD. adjust to
15. A. certainB. anyC. someD. one
16. A. sameB. similarity C. commonD. differences
17. A. formedB. developedC. grownD. made
18. A. withB. exceptC. besidesD. without
19. A. similarB. differentC. sameD. common
20. A. referringB. presentingC. arisingD. giving
参考答案
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