中华绒螯蟹胚胎附着系统的结构和形成机制

利用透射电镜和扫描电镜技术研究了中华绒螯蟹(Eriocheir sinensis)胚胎附着系统的结构及形成机制。中华绒螯蟹受精卵附着在雌性腹肢内肢的携卵刚毛上。该附着系统由三个连续部分组成:卵膜、卵柄和被膜,后者覆盖在携卵刚毛的绒毛上。研究结果显示:中华绒螯蟹的成熟胚胎由三层明显的卵膜组成,即E1、E2和E3层,但胚胎附着系统的卵柄及被膜仅为外层(E1)。卵巢中成熟卵的卵膜仅由E1层组成,E1分为两个亚层(E1a′、E1b′)。胚胎附着系统的形成与雌蟹的行为、腹肢粘液腺分泌的粘液、卵膜的超微结构及各层的变化有关。受精卵刚从生殖孔中排出时,卵膜(E1a′、E1b′)并不能直接粘附在携卵绒毛上。产卵后不久,雌蟹腹肢粘液腺分泌粘液的量增多,E1a′、E1b′的结构发生变化,表现为边界模糊,卵膜出现很强的粘性。在产卵后约60min E1层又明显分为两个亚层(E1a、E1b),同时排卵后雌蟹腹部的携卵绒毛不断地运动,这种运动促使携卵绒毛外的被膜形成。随着E1层亚结构的变化,E2层也开始形成,当E1新的两个亚层出现时,部分区域的E1层与E2层发生分离,卵柄开始形成,并牢固地附着在携卵绒毛上。被膜、卵柄与卵膜最外层的结构相同,均由E1层构成[动物学报51(5):852-861,2005]。     

中华绒螯蟹不同生理阶段腹肢的结构变化及粘液腺的发育特征

用显微及亚显微方法研究了中华绒螯蟹雌体不同生理阶段(幼蟹、未成熟蟹、成熟蟹、抱卵蟹和流产蟹)腹肢的体壁结构变化和粘液腺发育特征。体壁的上皮细胞层常与粘液腺相连,粘液腺分泌物经导管穿过各层角膜排出。不同生理状况下中华绒螯蟹的腹肢体壁各角膜层结构的比例及致密度有明显的差异,粘液腺细胞及导管的数量不同,粘液腺与上皮细胞的连接程度也不同。粘液腺是否正常分泌、刚毛囊的开闭均与中华绒螯蟹的胚胎附着有关。比较研究发现,太湖抱卵蟹腹肢体腔内腺体比温州本地抱卵蟹腹肢内腺体发达,分泌的粘液也特别多。分析认为中华绒螯蟹腹肢组织结构、粘液腺的发育和分泌状况与胚胎流产有密切的关系。     

南草蜥胚胎生长及物质和能量动用

用3种水热条件下(3温度×1湿度)孵化南草蜥(Takydomus sexlineatusDaudiin)卵以观测孵化卵质量变化、卵大小、孵化期、胚胎发育及孵出幼体特征。孵化过程中, 每5 d测定卵质量和大小。初生幼体称重后冰冻处死, 解剖分离为躯干、剩余卵黄和腹脂肪体, 65 ℃恒温干燥后称重。不同孵化温度对孵化期的长短有明显影响, 孵化期随孵化温度升高而缩短, 24 ℃平均41.8 d、27 ℃平均35.4 d、30 ℃平均34.0 d。卵孵化到14 d肉眼可见胚胎, 此后胚胎发育变化明显加速。孵化温度显著影响孵出幼体的质量、大小。本实验的受精卵在24 ℃、27 ℃中孵出的幼体质量较大。24 ℃、27 ℃发育的胚胎对卵黄的利用最充分, 剩余卵黄少。     

文蛤受精及早期胚胎发育过程的细胞学观察

用普通光镜、荧光显微镜技术和石蜡切片技术三种方法,对文蛤卵在受精及早期胚胎发育过程中的外形和核相变化进行了详细观察。结果表明:文蛤成熟未受精卵呈圆球形,直径90.06μm±5.59μm,核相处于第一次成熟分裂中期;精子为鞭毛型,全长48.05μm±1.60μm,头部呈狭茧形,长度为3.06μm±0.17μm;精卵混合后,精子迅速附着于卵子表面,受精后5min-10min,精子进入卵内并明显膨胀,激活卵子启动两次成熟分裂;分别在受精后20min、30min,受精卵完成第一次和第二次成熟分裂,先后排出第一、第二极体;成熟分裂完成之后,精、卵核体积迅速膨胀到最大,核膜重新出现,形成弥散状的雌、雄原核;受精后35min左右,雌、雄原核在卵子中央发生染色体联合,共同排列在纺锤体的赤道板上,形成第一次有丝分裂的中期分裂相;受精后40min-45min,在纺锤丝的牵引下染色体被拉向两极,结果形成2个大小不等的卵裂球;受精后55min-60min,第二次卵裂结束,形成1大3小4个卵裂球,卵裂过程中的核相变化与第一次卵裂基本相同,只是卵裂方向是与第一次卵裂的卵裂沟呈基本垂直的纵裂;受精后80min-90min,第三次卵裂完成,仍为不等全裂,但自此次起开始进行螺旋分裂。此外,实验中也发现了少量的多精入卵、多极分离和天然三倍体等异常现象。     

鲤胚胎孵化腺细胞

鲤胚胎孵化腺为单细胞腺体,发生于外胚层,可特异地被PAS染色。最早可在眼色素期检验出孵化腺细胞(Hatching gland cell,HGC)它们主要分布在头部腹面及头部与卵黄囊连接处。开始,HGC位于表皮细胞下面,随发育迁移到胚胎表面。根据扫描和透射电镜观察,在分泌孵化酶的前后,HGC区表面细胞呈鸡冠花状和疣状两种突起。前者系HGC处于分泌孵化酶期间;后者系HGC业已完成分泌作用,由于相邻的表皮细胞活动而形成的。HGC内富有粗面内质网、线粒体、核糖体和高尔基体,并由后者合成酶原颗粒。HGC在完成分泌作用后,仍留在表皮中,以后逐渐退化,但在孵化后30h仍可见残留的HGC。     

广西弄岗家燕种群的卵胚胎心率

2014年4—7月,利用红外胚胎心率测量仪对广西弄岗地区家燕Hirundo rustica的卵胚胎心率进行了测量。该种群的家燕在孵化的第4天才开始出现卵胚胎心率,且卵胚胎心率随孵化天数呈上升趋势,并在第13天达到最高值(280.5 BPM±23.0 BPM,t=3.855,P0.002)。家燕的卵胚胎心率日均增长为16.1 BPM±3.4 BPM,但与其卵容量和卵质量均不存在相关性(卵容量1.74 cm~3±0.08 cm~3,r=0.093,P=0.827;卵质量1.51 g±0.09 g,r=0.043,P=0.920)。     

孵化温度对赤链蛇胚胎代谢和幼体行为的影响

研究了赤链蛇(Dinodon rufozonatum)在孵化过程中卵的生长、孵化期、胚胎代谢和孵出幼体行为表现的热依赖性。结果显示:孵化温度对孵化期、卵增重、孵化过程中消耗的总能量和孵出幼体的运动表现有显著影响,但不影响胚胎代谢率、孵化成功率和幼体吐信频次。孵化期随着孵化温度的升高而缩短,孵化过程中,24℃终末卵重和胚胎代谢率显著大于30℃,而27℃与其他两个温度没有差异;27℃孵出幼体游速较24℃快,30℃孵出幼体与其他两个温度孵出幼体的游速无显著差异。上述结果显示:24—30℃是赤链蛇适合的孵化温度范围,与赤链蛇所处的生境温度相近。     

丽斑麻蜥胚胎物质和能量的利用及孵出幼体的特征

在所有可能影响有鳞类爬行动物卵孵化的环境因子中,温度的影响最为显著。孵化温度不仅能影响孵化期、孵化成功率和胚胎畸形率(Overall,1994),而且还影响孵出幼体的形态特征和功能表现(Van Damme et al.,1992;Ji and Bra a,1999;Bra a and Ji,2000;计翔等,1999;潘志崇、计翔,200     

三叠纪胎生主龙型海洋爬行动物（英文）

现代爬行动物的生殖方式包括卵生、卵胎生和"胎生"三种类型。总体而言,卵生即母体在陆地上产出羊膜卵,并依靠外界环境加以孵化;卵胎生系指羊膜卵在母体内孵化,随即产出幼子,其间胚胎的营养来源和代谢废物均限于羊膜卵内;所谓"胎生",是指某些类群的卵在母体内孵化后没有立刻产出,胚胎与母体建立了某种程度的营养乃至气体交换关系,此后再以幼体的形式娩出。卵胎生和"胎生"见于有鳞类。在化石中,由于无法识别胚胎与母体的营养联系等信息,通常只以"生产方式"加以定义,即除卵生以外,所有"含胚胎的化石"都统称为"胎生",目前"胎生"已有的准确记录包括鱼龙类、鳍龙类、沧龙类和离龙类。近期报道的"怀孕恐头龙"显示原龙类可能也有此种生殖方式,但标本的保存状态显示不能排除其"同类相食"之可能。本文记述了产自云南罗平地区中三叠系内一独立保存的、完整的圆胚状化石,标本的大小、形态、姿态和埋藏环境显示这是一个处于孵化后期、因某种原因而流产的胚胎。头后骨骼显示该标本代表了一种全新类型的海生原龙类,但是由于在个体发育中很多性状特征会有较大变化,因此胚胎乃至幼体标本不宜作为正型标本而建立新属种。这也是又一个主龙型爬行动物胎生的确切证据;同时这也进一步反映了盘县-罗平动物群中原龙类的高度多样性。     

三叠纪胎生主龙型海洋爬行动物

现代爬行动物的生殖方式包括卵生、卵胎生和“胎生”三种类型.总体而言,卵生即母体在陆地上产出羊膜卵,并依靠外界环境加以孵化;卵胎生系指羊膜卵在母体内孵化,随即产出幼子,其间胚胎的营养来源和代谢废物均限于羊膜卵内;所谓“胎生”,是指某些类群的卵在母体内孵化后没有立刻产出,胚胎与母体建立了某种程度的营养乃至气体交换关系,此后再以幼体的形式娩出.卵胎生和“胎生”见于有鳞类.在化石中,由于无法识别胚胎与母体的营养联系等信息,通常只以“生产方式”加以定义,即除卵生以外,所有“含胚胎的化石”都统称为“胎生”,目前“胎生”已有的准确记录包括鱼龙类、鳍龙类、沧龙类和离龙类.近期报道的“怀孕恐头龙”显示原龙类可能也有此种生殖方式,但标本的保存状态显示不能排除其“同类相食”之可能.本文记述了产自云南罗平地区中三叠系内一独立保存的、完整的圆胚状化石,标本的大小、形态、姿态和埋藏环境显示这是一个处于孵化后期、因某种原因而流产的胚胎.头后骨骼显示该标本代表了一种全新类型的海生原龙类,但是由于在个体发育中很多性状特征会有较大变化,因此胚胎乃至幼体标本不宜作为正型标本而建立新属种.这也是又一个主龙型爬行动物胎生的确切证据;同时这也进一步反映了盘县—罗平动物群中原龙类的高度多样性.     

Structure,formation, mechanical properties,and disposal of the embryo attachment system of an estuarine crab,Sesarma haematocheir

In most decapod crustaceans, fertilized eggs extruded from the gonopore attach to ovigerous hairs within the incubation chamber of the female. The attachment is effected by an "embryo attachment system." The three continuous components of this system are the egg envelope, the funiculus, and the investment coat, which wraps around an ovigerous hair. Transmission electron microscopy (TEM) revealed that the embryo of Sesarma haematocheir is enfolded by three distinct envelopes (E1, E2, and E3), whereas the embryo attachment system is composed of only the outermost, single envelope (E1) with two sublayers (E1a and E1b). This envelope (E1) originates from the outer layer of the vitelline membrane (envelope of the ovum) with two sublayers (E1a' and E1b'). The sequence and timing of events in the formation of the embryo attachment system was determined on the basis of observations of female behavior, ultrastructure, and mechanical properties of the membranes. The egg envelope (E1a' + E1b') is not adhesive immediately after extrusion from the gonopore; but 5 min after egg-laying, it becomes adhesive-a change associated with "fusion" of the two sublayers (E1)-and attaches the eggs to the ovigerous hairs from 5 to 30 min after egg-laying. The layer E1a' always binds to an ovigerous hair at specific, electron-dense attachment sites that are distributed longitudinally on the surface of each hair. Plasticity of the egg envelope changes, and the female kneads her eggs by the movement of ovigerous setae; this movement forms the investment coat on the ovigerous hair (10-40 min after egg-laying). Thirty minutes after egg-laying, the egg envelope again divides into two sublayers (E1a and E1b), and the adhesiveness rapidly decreases. The plasticity of the envelope remains, and the funiculus is formed, accompanied by kneading of the eggs (40-90 min after egg-laying). The embryos hatch one month after incubation, and the attachment systems all slip off their ovigerous hairs by the actions of the ovigerous-hair slipping substance (OHSS). This substance appears to act specifically at the attachment sites on the hair, lysing the bond with layer E1a, and thereby disposing of the embryonic attachment system and preparing the hairs for the next clutch of embryos.     

Ovigerous-hair stripping substance (OHSS) in an estuarine crab: purification, preliminary characterization, and appearance of the activity in the developing embryos

Ovigerous-hair stripping substance (OHSS) is an active factor in crab hatch water (i.e., filtered medium into which zoea larvae have been released). This factor participates in stripping off the egg attachment structures (i.e., egg case, funiculus, and the coat investing ovigerous hairs) that remain attached to the female's ovigerous hairs after larval release. Thus this activity prepares the hairs for the next clutch of embryos. OHSS activity of an estuarine crab, Sesarma haematocheir, eluted as a single peak on molecular-sieve chromatography, but this peak still showed two protein bands at 32 kDa and 30 kDa on SDS-PAGE. The two protein bands stained with a polyclonal antiserum raised to the active fractions from molecular-sieve chromatography. Moreover, antibodies purified from this polyclonal OHSS antiserum also recognized both the 32-kDa and 30-kDa bands. OHSS immunoreactivity and biological activity were associated with the attachment structures that remained connected to the ovigerous hairs after hatching. In developing embryos, both protein bands could be stained immunochemically at least 10 days before hatching. But OHSS biological activity appeared only 3 days before hatching. The immunoreactive protein bands were not observed in the zoea, but OHSS bioreactivity was present, though greatly reduced. The 32-kDa protein, at least, is probably an active OHSS, and the 30-kDa protein band may also be OHSS-related. The OHSS appears to be produced and stored by the developing embryo. Upon hatching, most of the material may be trapped by the remnant structures, and the remainder is released into the ambient water.     

The effects of egg position, egg mass size, substrate and biofouling on embryo mortality in the squid Sepioteuthis australis

Using a combination of laboratory and field investigations, this study examined embryo mortality in the southern calamary Sepioteuthis australis as a function of egg mass size, the substrate upon which the mass is attached, the position of the embryo within the mass, and the degree of biofouling. Egg mass size ranged from 2 to 1,241 egg strands, however most masses consisted of 200–299 strands. Small egg masses (<300 strands) were generally attached to soft-sediment vegetation (Amphibolis antarctica, Heterozostera tasmanica, Caulerpa sp.), whereas larger masses (>300 strands) were either securely attached to robust macroalgae holdfasts (Ecklonia sp., Marcocystis pyrifera, Sargassum sp.) or unattached. Rates of embryo mortality were highly variable ranging from 2 to 25%. Both laboratory and field results indicated a positive relationship between egg mass size and embryo mortality. Larger, unattached egg masses contained twice as many dead embryos than those securely attached to a substrate. Mortality rates were significantly affected by the embryos’ relative position within the mass and were highest in embryos located near the attachment point of the egg strand, within the interior of the mass, and in close contact with the substrate. This was attributed to the inability of the embryos to respire adequately and eliminate metabolic wastes. Biofouling did not strongly influence embryo mortality, but colonisation occurred in areas conducive to growth, photosynthesis, and respiration indicating ‘healthy’ regions within the mass.     

Cultivation of excysted metacercariae of Echinostoma caproni to ovigerous adults in the allantois of the chick embryo.

Chemically excysted metacercariae of Echinostoma caproni inoculated into the allantois of domestic chick embryos became ovigerous in that site within 9 days postinoculation. The egg preparation technique of Saville and Irwin was markedly better than that of a modified Zwilling procedure for obtaining large numbers of postinoculation embryos with worm infections. Adults of E. caproni from the allantois were larger and became ovigerous sooner than worms grown on the chorioallantois. Only worms from the allantois produced eggs with fully developed miracidia. Miracidia were released from these eggs, but an insufficient number was available to attempt infections in Biomphalaria glabrata snails.     

Embryonic development in the Patagonian red snail Odontocymbiola magellanica (Neogastropoda: Volutidae): Morphology and biochemistry

Embryo morphology, feeding mechanism and changes in composition of the egg capsule content during development (intracapsular fluids and embryos) were studied in Odontocymbiola magellanica from newly spawned egg capsules to the pre-hatching juvenile stage. Changes in embryo morphology and behavior are presented, based on observations and micrographs of living specimens and scanning electron microscopy. The arrangement of velar cilia and athrocytes and shell gland location and development differed markedly from other studied caenogastropods. Embryo ingestion of intracapsular fluid was promoted by velar ciliary currents at least from the early veliger stage, while feeding by grazing on the inner membranous layer of the egg capsule was rarely observed until juveniles were about to hatch. The main growth of embryos occurred during the veliger stages. A significant nutritional investment in egg capsules, as compared with other South American volutids was observed. Nutrition from proteins seemed to predominate at the expense of a high molecular weight fraction (>220 kDa). Calcium concentration in the intracapsular fluid remained constant during development, but notably, the total intracapsular content (i.e., the amount contained in both fluid and embryos) increased 3-fold, which may be explained by extraction from the egg capsule magnesium-rich calcite cover, or alternatively, by uptake of calcium from the surrounding sea water. Ammonia, a major end-product of nitrogen metabolism in marine invertebrates, was present in both embryos and intracapsular fluid, from which it may easily diffuse to the surrounding sea water through the egg capsule wall. Our results on embryo morphology, development and biochemical changes provide useful comparative data for evolutionary and developmental studies in the Volutidae as well as in other caenogastropods.     

Parental food conditions affect sex-specific embryo mortality in the yellow-legged gull (Larus michahellis)

Different mortality of males and females during early post-hatching development in sexually size-dimorphic bird species is usually attributed to different nutritional requirements of the sexes, because mortality is mostly biassed toward the larger sex. We investigated whether sex-specific embryo mortality in the yellow-legged gull (Larus michahellis), a size-dimorphic seabird, depends on parental condition. To test this, we experimentally modified parental nutritional conditions by supplementary feeding of yellow-legged gulls during egg formation, to evaluate sex-biassed environmental sensitivity of gull embryos. We found that eggs were larger in supplemented clutches, but egg size did not affect embryo survival. Survival of male gull embryos was more related to parental food conditions than was survival of female embryos. Survival of male embryos in supplemented clutches was greater than in unsupplemented clutches whereas survival of female embryos was similar in both groups. Because size at hatching was similar in both sexes our results suggest that male phenotype disadvantage is not exclusively linked to the energy demands of size-dimorphic development at the embryo stage.     

Structure of the egg funiculus and deposition of embryonic envelopes in a crab

The newly laid egg of Carcinus maenas is attached to a maternal ovigerous seta by a funiculus which consists of the two superimposed vitelline envelopes 1a + 1b, highly stretched and concurrently showing important structural alterations. The funiculus is glued to the specialized seta merely owing to the strong adhesiveness of its external face comprising the outermost vitelline envelope 1a, without any added adhesive. The subjacent envelope 2, originated from the cortical reaction, is not involved in such a funiculus elaboration. In the course of the embryonic development, four new coatings are successively secreted from the ectodermal embryonic cells, underneath the (1a + 1b + 2) fertilization envelope or embryonic capsule. They will remain until hatching in this concentric order, thus giving evidence of successive embryonic moulting cycles, with apolysis but without exuviation. In addition, the successive secretory phases, regarding to the embryonic envelope elaborations, happen in presence of high concentrations of the ecdysteroid ponasterone A which might be involved consequently in such secretory processes.     

An electron-microscopic study of syncytium formation during early embryonic development of the freshwater planarian Bdellocephala brunnea

To substantiate the assumption that the egg cell and blastomeres in planarian embryos influence surrounding yolk cells to form a syncytium, embryos at 1- to 8-cell stages were examined by electron microscopy. Within special areas of the endoplasmic reticulum both in the egg cell and in the blastomeres, a large number of vacuoles of various sizes formed and then disappeared at least four times over the period from egg-laying through the 8-cell stage as if their contents were being secreted. These activities diminished markedly at the 8-cell stage. Yolk cells surrounding the egg cell and blastomeres were aggregated in close contact with one another in a small clump shortly after egg-laying, and then, late in the 4-cell stage, became fused, forming a syncytium. The correlation between release of vacuoles by the egg cell and blastomeres and the formation of a syncytium by the yolk cells indicate that the cell fusion could be induced by a factor contained in the vacuoles.     

Changes of calcium distribution in ovules ofTorenia fournieri during pollination and fertilization

Summary Calcium distribution in ovules ofTorenia fournieri was studied by electron energy loss spectroscopy and transmission electron microscopic visualization of calcium antimonate precipitates. High calcium levels were found in the ovules ofT. fournieri. Calcium is situated mainly in extracellular regions before fertilization, including the surface of embryo sac, in the mucilage, and among the cells of the egg apparatus. Intracellular calcium was found only in the nucellar cells around the embryo sac and in the epidermis of the central axis and funiculus. After pollination, a labyrinthine structure (coralloid-like cell wall formation) develops on the micropylar surfaces of the egg apparatus that contain high levels of calcium. Calcium levels increase in the degenerating synergid after the penetration of the pollen tube. Calcium-antimonate precipitates are abundant in vacuoles of the disrupted synergid and pollen tube cytoplasm.Abbreviations EELS electron energy loss spectroscopy - EDX energy-dispersive X-ray microanalysis - LS labyrinthine structure     

Live-bearing manta ray: how the embryo acquires oxygen without placenta and umbilical cord

We conducted an ultrasonographic experiment on a pregnant manta ray, Manta alfredi (Chondrichthyes, Batoidea). This study showed how the embryo of the live-bearing elasmobranchs respires in the body of the female. In the embryonic stage, the manta ray embryo takes in uterine fluid by buccal-pumping. After birth, the manta ray shifts its respiratory mode from buccal-pumping to ram-ventilation. The rapid reduction of the spiracle size in the young manta ray may reflect this shift of respiratory mode. Unlike mammals or some carcharhinid sharks that acquire oxygen through a placenta and umbilical cord, the manta ray embryo does not have a direct connection with the mother. Thus, the manta ray embryo obtains oxygen by buccal-pumping of the uterine fluid, in the same way that the embryos of egg-laying species obtain oxygen from the water in the egg case. This finding extends our understanding of the diversity of embryonic respiratory systems in live-bearing vertebrates.