作者SMOW (凌宇劲鹰)
看板NTUOCBio92
标题无脊椎共笔4.15
时间Wed Oct 22 16:58:46 2003
海洋无脊椎动物 4.15
Xenoturbellids( fig 4.70a )
1 Hermaphrodite, flatwormilike animals that occur on soft marine
sediments in northwestern Europe.
2 许多特点类似扁虫,但是有些细微的构造和後口动物相似
3 曾被认为是paedomophic deuterstome larva,最近根据胚胎发生学认为
他的关系和bivalve molluscs较接近,且是经过dedifferentiation的
metamorphosed trochophore larva.
Buddenbrockids( fig 4.70b )
1 没有肠和神经系统,有点类似旋转虫( rhombozoan )或直游虫( orthonectidans )
2 possesses longitudinal tracts of muscle fibers and outer
layer of cells are no ciliated
3 运动方式像线虫
Lobatocerebrids
1 hermaphrodite interstitial worm
2 occur on soft marine sediments in North Atlantic and Red Sea
3 表面上非常像free living扁虫,但是在体壁的构造、肠和雄性的生殖
系统都较类似环节动物
4 Two contrasting views:
(i) It is a paedomorphic larva of some larger, possibly polychaete annelid, worm.
(ii) It is an early acoelomate offshoot of the line that ultimately gave rise to the schizocoelomate worms.
Orthonectidans直游虫
1 Bilaterally symmetrical,in the sexual phase at least.
2 Parasite unattached within the tissue of marine turbellarian,
annelids, nemertines, mollusks and echinoderms
3 Helical symmetry
4 Two phase,sexual and asexual. The sexes is separate in sexual
phase and dimorphic.
5 身体结构是一层轮状排列的体细胞围绕住一团配子,体细胞下层有环肌和纵肌
6 精子由雄性个体释出进入雌体,在慈体内授精後会形成ciliated larva(实际上是一层具有纤毛的细胞包围着一层germinal cells)在雌体内发育
7 The germinal cells are considered to be mesodermal in origin.
8 当larva释出侵入寄主後,会除去具有纤毛的细胞而留下germinal cells
继续增殖形成multinucleate plasmodium,这些plasmodium可以形无性分
裂形成另外的plasmodium
9 A single plasmodium producing either those of a single sex or
both males and females, and these sexual phases then leave the
host and complete the life history.
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