Myosin and actin are necessary for polar lobe formation and resorption in Ilyanassa obsoleta embryos

1998 ◽  
Vol 208 (4) ◽  
pp. 229-233 ◽  
Author(s):  
A. Hejnol ◽  
Hans-Dieter Pfannenstiel
Keyword(s):  
Ilyanassa Obsoleta ◽  
Polar Lobe

Membrane potential of fertilized eggs of Ilyanassa obsoleta during polar lobe formation and cytokinesis

1977 ◽  
Vol 57 (1) ◽  
pp. 215-220 ◽  
Author(s):  
Gary W. Conrad ◽  
Ann E. Kammer ◽  
George F. Athey
Keyword(s):  
Membrane Potential ◽  
Ilyanassa Obsoleta ◽  
Polar Lobe

Polar lobe formation and cytokinesis in fertilized eggs of Ilyanassa obsoleta

1980 ◽  
Vol 74 (1) ◽  
pp. 152-172 ◽  
Author(s):  
Gary W. Conrad ◽  
Susan E. Davis
Keyword(s):  
Ilyanassa Obsoleta ◽  
Polar Lobe

A comparison of certain isozyme patterns in lobeless and normal embryos of the snail, Ilyanassa obsoleta

Development ◽  
1971 ◽  
Vol 26 (3) ◽  
pp. 339-349
Author(s):  
Sallie B. Freeman
Keyword(s):  
Alkaline Phosphatase ◽  
Enzyme Activity ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Polyacrylamide Gel ◽  
Ilyanassa Obsoleta ◽  
Alkaline Phosphatases ◽  
Polar Lobe ◽  
Specific Nature ◽  
Isozyme Patterns

A study was made of the emergence of certain enzymes during the embryogenesis of Ilyanassa. Lobeless and normal embryos were compared in order to determine the effect of polar lobe removal on subsequent molecular developments. Polyacrylamide gel electrophoresis in capillary tubes, a technique requiring only small numbers of embryos, was used to obtain the isozyme patterns of alkaline phosphatases and of esterases. It was found that lobe removal interfered with the emergence of normal isozyme patterns of alkaline phosphatase and esterase during development. Certain bands of enzyme activity were severely reduced or absent while others appeared to be normal. The results provide further evidence that the influence of the polar lobe on development is of a specific nature.

Fate maps of the first quartet micromeres in the gastropod Ilyanassa obsoleta

Development ◽  
1991 ◽  
Vol 113 (2) ◽  
pp. 495-501 ◽  
Author(s):  
J. Render
Keyword(s):  
Cell Fate ◽  
Lucifer Yellow ◽  
Cell Lineage ◽  
Ilyanassa Obsoleta ◽  
Cell Fate Specification ◽  
Polar Lobe ◽  
Gastropod Mollusc ◽  
Cell Ablation ◽  
Critical Interpretation ◽  
Complete Cell

Cell fate specification in the gastropod mollusc Ilyanassa obsoleta involves both cell autonomous and inductive mechanisms, which depend on determinants localized first in the polar lobe and then in the D quadrant of the embryo. A complete cell lineage is lacking for this embryo and is essential for a critical interpretation of previous experimental results and an analysis of the mechanisms at the molecular level. Lineages of the first quartet micromeres were followed using Lucifer Yellow dextran as a tracer. The tracer was injected into individual first quartet micromeres using iontophoresis and patterns of fluorescence were analyzed in the larva after 8 days of development. Fluorescence was limited to head structures, including eyes, tentacles and velum. Structures on the left side were derived from 1a and 1d micromeres; 1a gave rise to the left eye, including the lens. Right side structures were derived from the 1c micromere and 1b contributed to the apical plate between the eyes and symmetrically to both sides of the velum. First quartet lineage data are compared with results from previous cell ablation experiments and with lineage data from other species.

Specification of first quartet micromeres in Ilyanassa involves inherited factors and position with respect to the inducing D macromere

Development ◽  
1998 ◽  
Vol 125 (20) ◽  
pp. 4033-4044 ◽  
Author(s):  
H.C. Sweet
Keyword(s):  
Normal Development ◽  
Eye Development ◽  
Ilyanassa Obsoleta ◽  
Cleavage Stage ◽  
Polar Lobe ◽  
Cell Stage ◽  
Cleavage Stage Embryo ◽  
Inductive Interaction ◽  
Stage Embryo ◽  
Transplantation Experiments

In the embryos of the gastropod Ilyanassa obsoleta, the development of several ectodermal structures requires an inductive interaction between the micromeres and the D macromere. The first quartet micromeres (1a, 1b, 1c and 1d) contribute to the head of the larva and descendants of 1a and 1c normally develop the eyes. The eyes do not develop if 1a and 1c are removed at the eight-cell stage. However, regulative eye development may occur if the precursors of 1a and 1c are removed at the two- or four-cell stage. One purpose of this study was to demonstrate which cells of the cleavage-stage embryo have the potential to develop an eye. The results of blastomere deletion experiments suggest that only the first quartet micromeres have this ability. In addition, the 1b micromere was found to be equivalent to 1a and 1c, but 1d was found to have a poorer eye-forming ability. A second purpose of this study was to examine how eye development is normally restricted to the 1a and 1c micromeres. Cell transplantation experiments demonstrate that the proximity of a first quartet micromere relative to the inducing D macromere is important for determining whether or not it will go on to develop an eye. The 1b micromere may not develop an eye during normal development because it is too far from the D macromere. However, the eye-forming ability of the 1d micromere is not influenced by its close position to the D macromere, but is restricted by its polar lobe lineage.

Polar Lobe formation in eggs of Ilyanassa obsoleta (Mollusca)

1989 ◽  
Vol 27 ◽  
pp. 101
Author(s):  
M.R. Dohmen ◽  
J.E. Speksnijder ◽  
D. Zivkovic
Keyword(s):  
Ilyanassa Obsoleta ◽  
Polar Lobe

Experimental studies on morphogenetic factors localized in the first and the second polar lobe of Dentalium eggs

Development ◽  
1970 ◽  
Vol 23 (1) ◽  
pp. 237-243
Author(s):  
W. L. M. Geilenkirchen ◽  
N. H. Verdonk ◽  
L. P. M. Timmermans
Keyword(s):  
Mytilus Edulis ◽  
Experimental Studies ◽  
Ilyanassa Obsoleta ◽  
Polar Lobe ◽  
Apical Tuft ◽  
The Third ◽  
Vegetal Pole ◽  
Morphogenetic Factors

During the development of several annelids and molluscs, a lobe of protoplasm is observed to protrude from the vegetal pole of the egg during the first cleavages. Removal of this polar lobe causes characteristic defects in the developing larvae as has been observed in the scaphopod, Dentalium (Wilson, 1904; Verdonk, 1968), the annelid Sabellaria (Hatt, 1932; Novikoff, 1938), the gastropod Ilyanassa obsoleta (Crampton, 1896; Clement, 1952) and the lamellibranch, Mytilus edulis (Rattenbury & Berg, 1954). In Dentalium a polar lobe is formed at the first, the second and the third cleavage. The lobes contain part of the cytoplasm, which later is confined to the D blastomere. After removal of the first polar lobe, embryos develop in which the post-trochal region and the apical tuft are absent. After removal of the second polar lobe the post-trochal region of the embryos is greatly reduced, but they develop an apical tuft (Wilson, 1904).

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