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单词 planula larva
释义

> as lemmas

planula larva
A free-swimming coelenterate larva with a flattened, ciliated body usually lacking internal cavities. Also planula larva.
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the world > animals > invertebrates > subkingdom Metazoa > grade Diploblastica > phylum Coelenterata > [noun] > member of > embryo
planula1835
planulan1886
the world > animals > invertebrates > subkingdom Metazoa > grade Diploblastica > phylum Coelenterata > [noun] > class Hydrozoa > member of > embryo
planula1835
actinula1871
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1835 J. G. Dalyell in Rep. Brit. Assoc. 1834 602 Ordinarily the Planulæ are white or yellow, opake, smooth and flattened.
1848 J. G. Dalyell Rare & Remarkable Animals Scotl. II. 287 The earliest sensible alteration in the ovum of the hydraoid and of some other zoophytes, is its elongation into an entire animal, rudely resembling the general outline of a tadpole, which we have designated a planula.
1865 E. C. Agassiz & A. Agassiz Seaside Stud. Nat. Hist. 41 Could we follow the history of any egg laid by one of these Discophoræ in the autumn..we should see that, like any other planula, the young hatched from the egg is at first spherical, but presently becomes pear-shaped, and attaches itself to the ground.
1887 Encycl. Brit. XXII. 425/2 The history of the second or planula type [of development] has been thoroughly worked out by Schulze in a little incrusting Tetractinellid sponge (Plakina monolopha, Schulze).
a1933 J. A. Thomson Biol. for Everyman (1934) I. v. 90 When this planula larva has fatigued itself, it settles down on a rock or seaweed, loses its cilia, buds out tentacles, and becomes a tiny polyp—the beginning of a zoöphyte colony.
1960 D. C. Braungart & R. Buddeke Introd. Animal Biol. (ed. 5) vii. 96 The fertilized egg is retained and by repeated cell divisions gives rise to an embryo that continues its development till it has reached the stage known as the planula, when it breaks away from the parent medusa.
1991 R. S. K. Barnes & K. H. Mann Fund. Aquatic Ecol. (ed. 2) viii. 162/2 The planula larvae of cnidarians (like the larvae of sponges) are not really larvae at all, but are free-living embryos—hollow (in some sponges) or solid blastulas.
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