scholarly journals Pattern Formation in a Pentameral Animal: Induction of Early Adult Rudiment Development in Sea Urchins

2002 ◽  
Vol 247 (2) ◽  
pp. 335-350 ◽  
Author(s):  
Sharon B. Minsuk ◽  
Rudolf A. Raff
Keyword(s):  
Pattern Formation ◽  
Sea Urchins ◽  
Adult Rudiment

Example: Early Pattern Formation in Amphibia

1988 ◽  
Author(s):  
Keith Stewart Thomson
Keyword(s):  
Pattern Formation ◽  
Early Development ◽  
Sea Urchins ◽  
Vitelline Membrane ◽  
Causal Processes ◽  
Phases Of Development ◽  
Primary Induction ◽  
The Subject ◽  
Axis Of Symmetry ◽  
Early Phases

The Amphibia has been one of the most important animal groups for the study of developmental biology, and a huge descriptive and experimental literature has accumulated over the years. While sea urchins, molluscs, and nematodes, and more recently, Drosophila, have each become an important vehicle for the study of different aspects of development, the Amphibia and chordates in general have been especially important as the vehicle for the study of inductive regulative mechanisms. The early development of all chordates is marked by two revolutions in the control of early pattern formation: dorsalization at the blastula stage and gastrulation—primary induction caused by the “organizer” —which was studied in great detail in Amphibia by Spemann and his coworkers and continues to be the subject of intense scrutiny. The early phases of development in Amphibia exemplify rather well some of the problems in discovering the causal processes in development, whether in the egg, at fertilization, in the blastula, or in gastrulation itself. The short discussion of early development in Amphibia that follows is meant to exemplify rather than catalogue these questions. The oocyte in amphibians is radially symmetrical. A first axis of symmetry is established between a more heavily pigmented animal hemisphere and a less pigmented vegetal hemisphere. Before fertilization the egg is covered with a transparent vitelline membrane. When fertilization occurs, the vitelline membrane lifts from the surface of the egg and the egg is then free to rotate inside it so that the animal hemisphere lies uppermost and the vegetal hemisphere is lowermost. This rotation is apparently a response to gravity, which means that the vegetal hemisphere is heavier, almost certainly a result of the concentration of more and larger yolk granules in the vegetal hemisphere. Therefore, if the egg rotates to a new orientation with the yolk down and the animal hemisphere up, it must be the case that at this point the yolk and other egg contents are not free to be redistributed within the egg but are secured in place. The animal vegetal axis now marks the future anteroposterior axis of the embryo.

Formation of the Adult Rudiment of Sea Urchins Is Influenced by Thyroid Hormones

1994 ◽  
Vol 161 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Yukihiro Chino ◽  
Minoru Saito ◽  
Kyo Yamasu ◽  
Takashi Suyemitsu ◽  
Katsutoshi Ishihara
Keyword(s):  
Thyroid Hormones ◽  
Sea Urchins ◽  
Adult Rudiment

scholarly journals First evidence of autofluorescence of a cell mass in developing temnopleurid sea urchins

Zoosymposia ◽  
2019 ◽  
Vol 15 (1) ◽  
pp. 98-105
Author(s):  
CHISATO KITAZAWA ◽  
AKIRA YAMANAKA
Keyword(s):  
Ultraviolet Irradiation ◽  
Sea Urchins ◽  
Cell Mass ◽  
Light Irradiation ◽  
Pigment Cells ◽  
Amniotic Cavity ◽  
A Cell ◽  
Adult Rudiment ◽  
Formalin Fixed ◽  
Hemicentrotus Pulcherrimus

The pigment cells of some sea urchin embryos emanate autofluorescence in response to light irradiation. However, it is unclear if this feature is maintained throughout larval development. In the present study we observed embryos and larvae of the temnopleurid sea urchins Temnopleurus hardwickii, T. reevesii, T. toreumaticus and Mespilia globulus exposed to light irradiation, and compared our findings with those of a strongylocentroid, Hemicentrotus pulcherrimus. After exposure to ultraviolet irradiation for a few minutes, there was a strong signal from the temnopleurid sea urchins. The signal was detected from a cell mass that is part of the adult (juvenile) rudiment, formed during development of the prism to the two-armed larval stage and not from pigment cells. This signal was observed in both live and formalin-fixed specimens. Fluorescence was also detected from the digestive organs, coelomic pouches, the ciliary band on the oral hood, from some yellowish-green cells and ectodermal cells, although there were some differences among species. In live H. pulcherrimus larvae, the amniotic cavity that is part of the adult rudiment emanated autofluorescence in response to ultraviolet irradiation. These results indicate that the autofluorescence observed in the cell mass of temnopleurid sea urchins is caused by a different mechanism than previously described. This feature may be a useful marker to trace development of the cell mass.

Evolutionary convergence in Otx expression in the pentameral adult rudiment in direct-developing sea urchins

2003 ◽  
Vol 213 (2) ◽  
pp. 73-82 ◽  
Author(s):  
M. G. Nielsen ◽  
E. Popodi ◽  
S. Minsuk ◽  
R. A. Raff
Keyword(s):  
Sea Urchins ◽  
Adult Rudiment ◽  
Evolutionary Convergence

Left-right positioning of the adult rudiment in sea urchin larvae is directed by the right side

Development ◽  
2001 ◽  
Vol 128 (24) ◽  
pp. 4935-4948 ◽  
Author(s):  
Mizuki Aihara ◽  
Shonan Amemiya
Keyword(s):  
Cell Fate ◽  
Sea Urchin ◽  
Normal Development ◽  
Sea Urchins ◽  
Inhibitory Effect ◽  
Dependent Manner ◽  
Larval Stages ◽  
Adult Rudiment ◽  
The Right ◽  
Pluteus Stage

Indirect-developing sea urchins eventually form an adult rudiment on the left side through differential left-right development in the late larval stages. Components of the adult rudiment, such as the hydropore canal, the hydrocoel and the primary vestibule, all develop on the left side alone, and are the initial morphological traits that exhibit left-right differences. Although it has previously been shown that partial embryos dissected in cleavage stages correctly determine the normal left-right placement of the adult rudiment, the timing and the mechanism that determine left-right polarity during normal development remain unknown. In order to determine these, we have carried out a series of regional operations in two indirect-developing sea urchin species. We excised all or a part of tissue on the left or right side of the embryos during the early gastrula stage and the two-armed pluteus stage, and examined the left-right position of the adult rudiment, and of its components. Excisions of tissues on the left side of the embryos, regardless of stage, resulted in formation of a left adult rudiment, as in normal development. By contrast, excisions on the right side of the embryos resulted in three different types of impairment in the left-right placement of the adult rudiment in a stage-dependent manner. Generally, when the adult rudiment was definitively formed only on the right side of the larvae, no trace of basic development of the components of the adult rudiment was found on the left side, indicating that a right adult rudiment results from reversal of the initial left-right polarity but not from a later inhibitory effect on the development of an adult rudiment. Thus, we suggest that determination of the left-right placement of the adult rudiment depends on a process, which is directed by the right side, of polarity establishment during the gastrula and the prism stages; however, but commitment of the cell fate to initiate formation of the adult rudiment occurs later than the two-armed pluteus stage.

Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

1983 ◽  
Vol 41 ◽  
pp. 194-195
Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor
Keyword(s):  
High Resolution ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Structural Features ◽  
Sea Stars ◽  
High Resolution Tem ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

Fate of sperm membrane in fertilized ova

1993 ◽  
Vol 51 ◽  
pp. 40-41
Author(s):  
Frank J. Longo
Keyword(s):  
Electron Microscopy ◽  
Electrical Activity ◽  
Sea Urchins ◽  
Morphological Changes ◽  
Integrated System ◽  
Electrophysiological Recording ◽  
Experimental Conditions ◽  
The Status ◽  
Sperm Membrane ◽  
Temporal And Spatial

Measurement of the egg's electrical activity, the fertilization potential or the activation current (in voltage clamped eggs), provides a means of detecting the earliest perceivable response of the egg to the fertilizing sperm. By using the electrical physiological record as a “real time” indicator of the instant of electrical continuity between the gametes, eggs can be inseminated with sperm at lower, more physiological densities, thereby assuring that only one sperm interacts with the egg. Integrating techniques of intracellular electrophysiological recording, video-imaging, and electron microscopy, we are able to identify the fertilizing sperm precisely and correlate the status of gamete organelles with the first indication (fertilization potential/activation current) of the egg's response to the attached sperm. Hence, this integrated system provides improved temporal and spatial resolution of morphological changes at the site of gamete interaction, under a variety of experimental conditions. Using these integrated techniques, we have investigated when sperm-egg plasma membrane fusion occurs in sea urchins with respect to the onset of the egg's change in electrical activity.

Pattern formation in the splay Freedericks transition of a nematic side-group polysiloxane

1993 ◽  
Vol 3 (6) ◽  
pp. 865-889 ◽  
Author(s):  
Norbert Schwenk ◽  
Hans Wolfgang Spiess
Keyword(s):  
Pattern Formation ◽  
Side Group

Pattern Formation in a Twisted Nematic Liquid Crystal Cell under an External Magnetic Field

1996 ◽  
Vol 6 (2) ◽  
pp. 235-253 ◽  
Author(s):  
Luca Carlotti ◽  
Sandro Faetti ◽  
Maurizio Nobili
Keyword(s):  
Magnetic Field ◽  
Liquid Crystal ◽  
External Magnetic Field ◽  
Pattern Formation ◽  
Nematic Liquid Crystal ◽  
Liquid Crystal Cell ◽  
Crystal Cell ◽  
Twisted Nematic ◽  
Twisted Nematic Liquid Crystal
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