三种蚤生殖系统的细微结构:雌性外生殖器的发育

本文研究了缓慢细蚤 Leptopsylla segnis(Schōnherr),不等单蚤 Monopsyllus anisus(Rothschild)和猫栉首蚤指名亚种Ctenocephalides felis felis(Bouché)雌性外生殖器的结构,观察了从幼虫、前蛹、蛹至成虫各发育时期的雌性外生殖器的内部结构变化.对一直悬而未决的雌蚤中输卵管等的起源问题,进行了详细的观察和探讨.认为从晚期3龄幼虫开始出现的雌性外生殖器芽,在前蛹期成为四个部分:1.第7腹板后缘腹壁内陷形成的一对外胚层囊;2.紧接外胚层囊后并延伸至第8腹板的外胚层增厚;3.在第8腹板后部,外胚层增厚两侧的产卵器芽;4.第8腹板后缘腹壁内陷形成的受精囊芽.并认为,这三种蚤的中输卵管由一对外胚层囊和其后的外胚层增厚前端的一小部分内陷形成,阴道由外胚层增厚的大部分和第8、9腹板腹壁内陷形成,受精囊由受精囊芽内陷形成.     

Calcium localisation by X-ray microanalysis and fluorescence microscopy in larvae of zooxanthellate and azooxanthellate corals

X-ray microanalysis and fluorescence microscopy (Calcium Orangetrade mark) was used to determine the distribution of intracellular calcium (I(Ca)), in the form of total and ionic calcium respectively, in planulae and settled larvae of a zooxanthellate coral. The distribution of total calcium only was determined in larvae of an azooxanthellate coral. In azooxanthellate planulae and settled larvae, total I(Ca) concentration in the oral ectoderm was high and similar to that in seawater (SW). Calcium concentration did not vary (P > 0.05) between planulae and settled larvae. However, settled larvae accumulated large amounts of calcium in gastrodermal lipid-containing cells. In contrast, zooxanthellate planulae possessed significantly (P < 0.01) lower concentrations of total I(Ca) within ectodermal cells in comparison to settled larvae. In addition, in settled zooxanthellate larvae total calcium concentration in the mesogloea and coelenteron was significantly (P < 0.05) higher than in the oral ectodermal and gastrodermal cells, respectively. Total I(Ca) concentrations in the oral ectoderm of settled larvae were also significantly (P < 0.01) lower than that of the calicoblastic ectoderm. In zooxanthellate settled larvae, ionic I(Ca) levels in the aboral epithelium surrounding rapidly growing septa were high. These levels increased significantly (P < 0.05) within the tissue surrounding growing septa after incubation in high-calcium SW.     

Homoeotic Gene ETc Controls the Cell Number of Embryonic Ectodermal Layers of Bombyx mori

The formation of segments of Bombyx larvae involves differentiation of legged and legless segments during embryogenesis. Observations by light microscopy of serial sections of developing embryos of Bombyx showed that the cell number of the ectodermal layers increased more rapidly in segments where legs were being extruded than in those where no appendages were formed. In the embryos of a homoeotic mutant for the E -pseudoallelic locus (about 0.0–VI), E^Tc/E^Tc , in which all the abdominal segments were legless, the cell number of the ectodermal layers did not increase as in normal embryos. These findings suggest that the E^Tc gene controls the cell number of the ectodermal layers in relation to the differentiation of abdominal segments.     

Identification of morphogenetic capability limitations via a single starfish embryo/larva reconstruction method

Reconstruction of a starfish embryo provides unique morphogenesis during the developmental process that is not observed in normal development. Here, we established a novel method for reconstruction from single embryos/larvae. By using this method, we investigated the morphogenetic capabilities in critical steps during the reconstruction process as showed by the reconstructed embryos generated from embryos/larvae at the six developmental stages, or from segregated ectodermal and/or endomesodermal cells. Additionally, the novel method addressed several problems found in prior methods related to reproducibly generating reconstructed embryos. In the reconstructions from the various stage embryos/larvae, the morphogenetic capabilities were substantively reduced in the reconstructed embryos generated from 3‐day bipinnaria (3dBp). The combination experiments using ectodermal or endomesodermal cells segregated from 2dBp or 3dBp showed a reduction of the morphogenetic capabilities in both cells types in 3dBp. The reconstructed embryos generated from ectodermal or endomesodermal cells segregated from 2dBp possessed partial morphological features, such as formation of the epithelium or blastopore, but all failed to develop into bipinnariae. These results indicate two limitations of the morphogenetic capabilities during the reconstruction process. Firstly, the morphogenetic capabilities to reconstruct an embryo are considerably reduced between 2dBp and 3dBp. Secondly, cells specified as ectoderm or endomesoderm possess limited morphogenetic capabilities to reconstruct bipinnaria. Furthermore, our results demonstrate that the interaction between these specified cell types is required for reconstruction.     

A Novel Substance Localizing on the Apical Surface of the Ectodermal and the Esophageal Epithelia of Sea Urchin Embryos

A new substance (ES-1) which localizes on the ectodermal and espophageal epithelia of sea urchin embryos was identified by a monoclonal antibody, McA ES-1. McA ES-1 recognized a 175 KDa protein of fertilized and 200 KDa in proteins of unfertilized egg-cortices. By indirect fluorescent antibody staining, ES-1 was found on the plasma membrane of fertilized eggs and in the cortical region of unfertilized eggs. ES-1 was not contained in the cortical granules and remained fixed in the cortex after centrifugation of unfertilized eggs for 30 min at 20,000 g. The polarized localization of ES-1 on the apical surface of ectodermal epithelial cells continued to the metamorphosis. It disappeared from mesenchyme cells and other migrating cells of the gastrula, while ES-1 was reexpressed in the presumptive esophagus to be connected with ectodermal epithelium. This may suggest a functional significance of ES-1 in establishment of cell polarity in the epithelium of larvae. In metamorphosing larvae and adults, the apical localization of ES-1 could no longer be found, and it was found in coelomocytes. From these findings, it is concluded that ES-1 was a novel surface substance of embryos and is probably phagocytosed at metamorphosis.     

Effects of cryopreservation on the ultrastructural anatomy of 3-segment Nereis virens larvae (Polychaeta)

Abstract. A transmission electron microscope study of fresh and cryopreserved Nereis virens larvae at the three chaetiger stage is described with special emphasis on examining the structure of the photoreceptors and surface ciliation of the head, the midgut epithelium, and muscle cells. Complex ectodermal structures such as the developing rhabdomeric adult eyes were unaffected by the cryopreservation procedure. Some loss of surface cilia on the prostomium was observed but is not life-threatening though it may restrict ciliary swimming in the recovered larvae. Loss of pigment from the prostomium is caused by osmotic stress. Structural damage was observed in the digestive tissues of the larvae cryopreserved before or after the optimum stage of development. This damage is potentially more serious and may account for the relatively short time period during development where cryopreservation can be successfully applied.     

Muscle lineage cytoplasm can change the developmental expression in epidermal lineage cells of ascidian embryos

Cytoplasm from muscle lineage blastomeres of an ascidian embryo can cause cells of a nonmuscle lineage to produce larval tail muscle acetylcholinesterase. Muscle cytoplasm was partitioned microsurgically into epidermal lineage blastomeres at the eight-cell stage. Posterior half-embryos (the two B3 cells) of Ascidia nigra were obtained first by separating the anterior and posterior blastomere pairs at the four-cell stage. At third cleavage, the two B3 cells divide into an ectodermal cell pair that gives rise solely to epidermal tissues, and a mesodermal-endodermal blastomere pair from which the tail muscle cells are derived. When the ectodermal and mesendodermal blastomere pairs were isolated from one another by microsurgery and reared as partial embryos, only cells originating from the mesendodermal blastomeres produced a histochemical acetylcholinesterase reaction. Immediately after cleavage of the isolated B3 cells into ectodermal and mesendodermal cell pairs, the cleavage furrows could be made to disappear by pressing firmly on the mesendodermal cells with a microneedle. Repeated up and down pressure with the microneedle at a new position across the mesendodermal cells caused furrows to reestablish in the new position, thereby incorporating mesodermal cytoplasm and increasing the size of the ectodermal cells. The cytoplasmically altered ectodermal blastomere pairs, which became detached from the mesendodermal cells by this microsurgical procedure, continued to divide and were reared to “larval” stages. One-third of these epidermal partial larvae produced patches of cells containing acetylcholinesterase. These results lend further support to the theory that choice of particular differentiation pathways (embryonic determination) in ascidian embryos is mediated by segregation of specific egg cytoplasmic determinants.     

Axial patterning of the pentaradial adult echinoderm body plan

Adult echinoderms possess a highly diverged, pentaradial body plan. Developmental mechanisms underlying this body plan are completely unknown, but are critical in understanding how echinoderm pentamery evolved from bilateral ancestors. These mechanisms are difficult to study in indirect-developing species; in this study, we use the direct-developing sea urchin Heliocidaris erythrogramma, whose accelerated adult development can be perturbed by NiCl₂. We introduce a new nomenclature for the adult echinoderm axes to facilitate discussion of the radially symmetric body plan and the events required to pattern it. In sea urchins, the adult oral–aboral axis is often conflated with the long axes of the five rays; we identify these as distinct body axes, the proximodistal (PD). In addition, we define a circular axis, the circumoral (CO), along which the division into five sectors occurs. In NiCl₂-treated larvae, aspects of normal PD pattern were retained, but CO pattern was abolished. Milder treatments resulted in relatively normal juveniles ranging from biradial to decaradial. NiCl₂ treatment had no effect either on mesodermal morphology or on the ectodermal gene expression response to an inductive mesodermal signal. This suggests that the mesoderm does not mediate the disruption of CO patterning by NiCl₂. In contrast, mesodermal signaling may explain the presence of PD pattern in treated larvae. However, variations in appendage pattern suggest that ectodermal signals are also required. We conclude that CO patterning in both germ layers is dependent on ectodermal events and PD patterning is controlled by mutual ectoderm–mesoderm signaling.     

Effects of extra‐embryonic provisioning on larval morphology and histogenesis in Boccardia proboscidea (Annelida,Spionidae)

Morphology is strongly correlated with trophic mode in marine invertebrate larvae. We asked if larval morphogenesis is influenced by adelphophagy, a trophic mode in which larvae are provisioned with additional yolk in the form of extra‐embryonic nurse eggs, instead of the more common increase in egg size. We used histology and scanning electron microscopy to analyze morphogenesis in Boccardia proboscidea, a polychaete that produces both small planktotrophic larvae and large adelphophagic larvae in a single egg capsule. Results indicate that both morphs are similar for histogenesis of ectodermal derivatives, and differ for the gut mucosa and coelom which show delayed differentiation in the adelphophagic morph. Heterochrony in gut and coelom development suggests that differentiation of these organ systems is decoupled from overall development, and that a trade‐off exists between maturation of these tissues and rapid growth. We also looked for potential barriers to adelphophagy in planktotrophic larvae that have nurse eggs available to them. These planktotrophic larvae appeared morphologically equipped for adelphophagy: the gut was differentiated at an early stage, and larvae had structures involved in nurse‐egg ingestion in the adelphophagic morph (e.g., oral cilia and ventral ciliated patches). Planktotrophic larvae were additionally capable of ingesting particles (Di‐I) while in the egg capsule. Lack of adelphophagy in planktotrophic larvae remains enigmatic but these results indicate that morphology alone does not account for the arrested development shown by these larvae. J. Morphol. 2013. © 2012 Wiley Periodicals, Inc.     

ULTRASTRUCTURAL CHANGES IN EMBRYONIC ECTODERMAL CELLS OF THE NEURULATING RAT EMBRYO

Embryonic ectodermal cells of rat embryos were examined by light and electron microscopy during the early stage of neurulation. Before the onset of neurulation (day 9–6 hr embryos), the cells underwent certain characteristic ultrastructural changes; that is, apical cytoplasmic protrusions and free spherules appeared, numerous vacuoles were formed in the cytoplasm, mitochondria showed ballooning, and the endoplasmic reticulum became dilated. The amniotic cells derived from the embryonic ectoderm exhibited the same ultrastructural changes, but those from the extraembryonic mesoderm did not. Embryonic mesodermal cells and neuroectodermal cells also did not show these changes. In the middle stage of neurulation (day 9–12 hr embryos), the embryonic ectodermal cells and the amniotic cells derived from the embryonic ectoderm assumed a flat squamous shape. None of the ultrastructural changes observed in day 9–6 hr embryos were noted in these cells. The functional significance of the production of apical cytoplasmic protrusions and free spherules in the embryonic ectodermal cells and amniotic cells is discussed in relation to similar phenomena reported to occur in other cell types.     

THE CERIANTHAR1AN NERVOUS SYSTEM

Evidence supporting the presence of nerve cells in the columnand tentacles of Pacliycerianthiis is described. G. F. Gwilliamhas shown that electrical stimuli can be transmitted to theectodermal muscle by the intact epithelium and subepithelialnetwork of the ectoderm of the column. In these preparationsthe ectodermal muscle, mesogloea, and endoderm were cut. Incontrast, preparations in which the ectodermal muscle has beenleft intact and the epithelium and subepithelial network cutdo not show such transmission. The author and Gwilliam have independently used different silverstain methods to demonstrate large cells, piobably nerve cells,with cell bodies in the base of the epithelium and with fibersrunning into the subepithelial network. The author has foundsimilar bipolar cells in the tentacles and column by using macerationtechniques. These cells are compared with other cell types foundin the tentacles.     

The role of GLWamides in metamorphosis of Hydractinia echinata

 The metamorphosis of many marine invertebrate larvae is induced by environmental signals. Upon reception of the cues, internal signals have to be set in motion to convey information to all cells of the larvae. For hydrozoan larvae it was hypothesised that ectodermal neurosensory cells at the anterior part are those cells receptive of the inducer. Recently, it was shown that novel peptides with a common GLWamide terminus are found in Cnidaria. These peptides are located in a specific subset of the anterior sensory cells. It was hypothesised that the neuropeptides represent an internal signal coordinating the metamorphic process. In the current study we present further evidence for this hypothesis. Induction of metamorphosis is very specific for the GLWamide terminus and amidation is essential. The potency to metamorphose is strongly correlated with the presence of GLWamide-immunoreactive cell bodies. Our data fit our hypothesis about a very important role of GLWamides in the initiation of the morphogenetic processes very well. Received: 16 February 1998 / Accepted: 11 April 1998     

The significance of moulting in Ecdysozoan evolution

SUMMARY Three major bilaterian clades first appear in the Early Cambrian fossil record: Deuterostomia, Lophotrochozoa, and Ecdysozoa. The taxa placed in Ecdysozoa are characterized by a moulting habit, unknown in the other major clades. The origin and consequences of moulting are of fundamental importance to the history of the ecdysozoan clade, chiefly because moulting precludes motile ectodermal cilia. Moulting may have originated as an adaptation to permit the enlargement, during growth, of secreted cuticular spines, flanges, and other structures used as ancillary locomotory devices. A combination of phylogenetic and fossil evidence suggests that the early members of these clades were small vermiform paracoelomates that likely lacked indirect-developing planktotrophic larvae. Thus, the evolution of planktotrophic larvae may have been independently achieved at least three times within Bilateria. The nonmoulting clades evolved larvae that swim and feed via ciliated tufts and bands, presumably intercalating these forms within their early developmental systems. Within Ecdysozoa, feeding larvae lacked ciliary feeding tracts and evolved by modification of early instars, employing limbs or setae to generate feeding currents. The setting aside during larval life of cells that give rise to adult features is probably an adaptation associated with metamorphosis.     

三峡库区丰都江段鱼类早期资源现状

2014 年47 月鱼类主要繁殖季节于三峡库区(重庆丰都县)进行鱼类早期资源调查, 以了解三峡库区鱼类早期资源现状, 四大家鱼在库区是否仍有产卵场等问题。调查共采集到鱼类50 种, 分属5 目9 科。采集时, 卵汛出现在6 月后流速较高的时段, 其中贝氏的数量最多, 占86.24%。仔鱼出现的高峰期为6 月上旬至7 月中旬, 太湖新银鱼的数量最多, 占58.36%, 其次为子陵吻虎鱼, 占27.04%。在仔鱼中, 种类组成呈明显的月份差异, 4 月鲤、鲫占数量优势;5 月太湖新银鱼、子陵吻 虎鱼占数量优势;6 月后鲌亚科、鳅科、鳜等种类开始出现, 种类明显增多。通过估算, 调查期间流经丰都断面的鱼卵总量为4.37108 粒, 四大家鱼鱼卵为0.21107 粒;仔鱼总量为111.98108 尾, 四大家鱼仔鱼为0.21108 尾。通过产卵场的推算, 丰都断面采集的四大家鱼来自涪陵城区江段和三峡库区上游的重庆巴南区至朱沱镇江段的产卵场。通过对卵苗漂流密度的昼夜规律分析, 6 月之前夜间仔鱼密度显著高于白天, 而6 月后仔鱼昼夜漂流密度无显著差异。本研究表明, 从三峡库尾进入三峡水库的鱼类早期资源丰富, 大部分鱼类繁殖发生在6 月以后水温较高、入库流量大、库区流速较高的时段, 库尾部分江段在流速较高时期, 仍存在四大家鱼的产卵场。       

Neurotoxin localization to ectodermal gland cells uncovers an alternative mechanism of venom delivery in sea anemones

Jellyfish, hydras, corals and sea anemones (phylum Cnidaria) are known for their venomous stinging cells, nematocytes, used for prey and defence. Here we show, however, that the potent Type I neurotoxin of the sea anemone Nematostella vectensis, Nv1, is confined to ectodermal gland cells rather than nematocytes. We demonstrate massive Nv1 secretion upon encounter with a crustacean prey. Concomitant discharge of nematocysts probably pierces the prey, expediting toxin penetration. Toxin efficiency in sea water is further demonstrated by the rapid paralysis of fish or crustacean larvae upon application of recombinant Nv1 into their medium. Analysis of other anemone species reveals that in Anthopleura elegantissima, Type I neurotoxins also appear in gland cells, whereas in the common species Anemonia viridis, Type I toxins are localized to both nematocytes and ectodermal gland cells. The nematocyte-based and gland cell-based envenomation mechanisms may reflect substantial differences in the ecology and feeding habits of sea anemone species. Overall, the immunolocalization of neurotoxins to gland cells changes the common view in the literature that sea anemone neurotoxins are produced and delivered only by stinging nematocytes, and raises the possibility that this toxin-secretion mechanism is an ancestral evolutionary state of the venom delivery machinery in sea anemones.     

Inhibition of settlement and metamorphosis of the ascidian Herdmania curvata by non-geniculate coralline algae

The surfaces of non-geniculate coralline algae (NCA) are known to induce the settlement and metamorphosis of disparate marine taxa. In this study we investigate the responsiveness of larvae of Herdmania curvata (Ascidiacea: Stolidobranchia) to three species of NCA (Neogoniolithon brassica-florida, Hydrolithon onkodes, and Lithothamnium prolifer) that cohabit the slope and crest of Heron Reef, Great Barrier Reef. H. curvata larvae were first exposed to these NCA at or within 2 h of hatching, which is 1 to 2 h prior to attaining competence, and then cultured continuously with the NCA for 12 to 14 h. Rates of settlement and metamorphosis of H. curvata cultured in laboratory chambers in the presence of the different NCA were significantly lower than spontaneous rates in seawater. The limited settlement in treatments containing NCA were confined entirely to the chamber periphery, and settlement never occurred on the surface of the NCA. The inhibitory effect was dose-dependent and was stronger in N. brassica-florida and H. onkodes than in L. prolifer. Larvae that did not settle in treatments with NCA had rounded anterior trunks and, in extreme cases, kinked tails with rounded and dissociated tail muscle cells. In some individuals, we observed the anterior chemosensory papillae being sloughed off the larval body. Morphological analysis of trunk ectodermal and mesenchymal nuclei of larvae cultured in the presence of the NCA revealed that general necrotic cell death was occurring. Importantly, H. curvata larvae that were exposed to NCA could not subsequently be induced to metamorphose in KCl-elevated seawater, whereas larvae not exposed to NCA metamorphosed at high rates in KCl-elevated seawater.     

Development of Serotonergic Neurons in Embryos of the Sea Urchin, Strongylocentrotus purpuratus

The development of the serotonergic component of the nervous system of larvae of S. purpuratus is traced using indirect immunofluorescence with a polyclonal antibody against the neurotransmitter serotonin. Initially one or two neuroblasts can be detected in the thickened epithelium of the animal plate of late gastrulae (56 hr). The number of immunoreactive cells increases to about eight during formation of the pluteus (85–90 hr). Immunoreactive axons appear simultaneously from all neuroblasts present in the 79 hr prism stage larva and form the apical ganglion. It is proposed that this component of the larval nervous system is derived from a small number of ectodermal cells associated with the apical tuft.     

Ultrastructure of the digestive system and the fate of midgut during embryonic development in Porcellio scaber (Crustacea: Isopoda)

Microscopic anatomy of the digestive system in embryos and larvae of the terrestrial isopod crustacean Porcellio scaber was investigated by light bright field, fluorescence and electron microscopy. During marsupial ontogenetic development the event-dependent staging was used to discriminate the various embryonic stages. At the late embryo stage the differentiation of the ectodermal part of the gut into the complex filtering foregut and the hindgut with absorptive and transporting functions is accomplished. The gut of the marsupial manca larva is fully developed and similar to that of the adult. In early embryos the endodermal midgut gland primordia are filled with yolk and lipid globules. In late embryos the epithelium of paired midgut gland tubes is composed of two cell types; one of them exhibits orange autofluorescence. The endodermal cells located between the foregut and the midgut glands of late embryos form the prospective midgut. The cells have electron dense cytoplasm, abundant glycogen fields, endoplasmic reticulum, dictyosomes and numerous vesicles. In the adults the endodermal cells of the midgut remain only in the midgut gland ducts which connect the midgut glands and the foregut. Details of the cellular ultrastructure and morphogenesis of the ectodermal and endodermal parts of the digestive system during embryonic development of Porcellio scaber provide data for further phylogenetic and comparative studies in peracaridan crustaceans and other arthropods.     

Cyto-differentiation of the neuroblasts from the neural ectodermal cells in grasshopper,Chortophaga viridifasciata (De Geer) (Orthoptera: Acrididae) embryos

The first sign of neurogenesis in the embryo of grasshopper, Chortophaga viridifasciata (Orthoptera: Acrididae), is signaled by a partition of the ectodermal cells into non-neural ectodermal cells and neural eetodermal cells. The neuroblasts are differentiated from neural ectodermal cells. In the present study, we examined the pattern of mitotic activity in the developing embryo by tracing the incorporation of BrdU in S phase nuclei. The results indicate that the ectodermal cells in 6-day old embryos do not show any signs of differentiation. In 7-day old embryos, in which ectodermal cells become partitioned into 2 types, almost no neural ectodermal cells are incorporated with BrdU, whereas a constant incorporation is revealed in non-neural ectodermal cells. Among the mitotically quiescent neural ectodermal cells, which are arrested at the GI stage of the cell cycle, in 8-day old embryos, the neuroblasts are the first to resume their mitotic activity, while the other cells are then released from the mitotic quiescence. It seems that the mitotic quiescence may be an essential process to acquire a neural fate.