Observation of two Amitotic way in the Epidermal Cells of
the Plant Pelargonium Zonale `Kleiner Liebling` 1
Li Mingyin
School of Life Science and Engineering, Mianyang Normal University, Mianyang, Sichuan,
China (621000)
Institute of Garden Science, Humboldt University of Berlin, Germany (14195)
E-mail: ,
Abstract
Amitosis, different from mitosis, is a rare form of the proliferation of the cells. Most amitosis were observed in animal cells; only few of them were reported in plant cells. The cytological investigation in this study demonstrated first time in Pelargonium zonale two different amitotic nuclear division ways ：cleavage and constriction，in which no appearance of the visible chromosomes and no spindles were observed. After amitotic nuclear division the cytokinesis was also observed, in which the cytoplasm divided directly into two or more parts accompany with formation of two or more daughter cells. This study showed the genetic material may sometimes be unequally distributed between the daughter cells in amitosis, and the amitosis could lead to bi-, tri- and multinucleated cells. It was suggested that amitosis could be a way of the division of the endoreduplicated cells.
Keywords: Pelargonium; epidermal cell; amitosis; endoreduplication; nucleus cleavage; nucleus constriction.
1. Introduction
Amitosis (a-mitosis) was suggested by Rieger, et al. (1991) as a direct nuclear division other than mitosis and it was defined that the nucleus by amitosis divided directly without the visible chromosomes and spindles. The most amitotic division was observed in certain types of animal cells (Chen and Wan 1986; Bhattathiri 2001；Isakova and Shilova 2003; Isakova1 and Mead 2004). There were only a few reports of amitoses in plant special tissue (Miller 1980; Marciniak 1991; Appezzato-da-Glória and Machado 2004) as well as in treated tissue (Torre and Martin 1975), or in tissue culture of tobacco (Altamura et al. 1991; Valente et al., 1998). Therefore，amitotic division occurs rarely and was poorly studied in plant. In this present study, many cells with intranuclear structure characteristics of amitosis were observed in the epidermal cells of the muted clone 5/74/2 by Pelargonium zonale, in which chromosomes, spindles as well as nucleolus division had not observed. Basen on morphologic changes of the cell nucleus division, it was suggested that two amitotic models existed.
2. Materials and Methods
The investigated plant was cloned 5/74/2, which is one of the mutants of the haploid plant `Kleiner Liebling` of Pelargonium zonale from Humboldt University of Berlin. It had different ploidy levels in epidermis of the leaf tissue. The material treatment und methods for investigation were made on the basis of Li Mingyin (2007).
2.1 Preparation of the sample
The shoots tips were fixed in carnoy II for 24 hours and then soaked in ethylenglycolmonoethylether, 96% ethanol, propane and butane sequentially each for 24 hours. After that the shoot tip samples were polymerized in an embedding solution, containing 100 ml Technovit 7100 (Germany) and 1 g dibenzoylperoxid for 24 hours. Then they were carefully 1 The investigation was carried out in Humboldt university of Berlin; the manuscript is finished in Mianyang Normal University
placed in embedding capsules with mixture solution (10 ml above embedding solution and 1 ml dimetylsulfoxid) and to solidifying for 24 hours. The embedded shoot tips were sectioned to 8 -10 µm with a rotation microtom.
2.2 Staining of the samples
The slices of the plant tissue were stained in diluted (1:1 with distilled water) toluidinblue solution (60 ml of 1% toluidinblue water solution was mixed with 30 ml of 2.5% natriumcarbonat solution and 10 ml of 70% alcohol) for ca. 30 -60 second and then washed with running water (Böck 1989). After drying, the well stained tissue slices on the slide were covered with a cover slip using DPX solution (Fluka) and stored in the dark for investigation.
3. Results
3.1 Definition and character of amitosis
In this study, it had been observed in histological serial sections that the cells arranged irregularly in the epidermal layer，a nucleus directly divided into two or more parts, without appearance of the visible chromosomes and without appearance of the visible spindles (Fig. 1A-E ). The most figures of the nuclear division ordered in groups of shape were considered as a between (middle) stage of the nuclear division. On the basis of the morphological characteristics, the nucleus division without visible chromosomes and spindles could be constructed into two different processes of the nuclear division with cleavage and constriction.
3.2 Process of the nuclear cleavage
The nuclear cleavage division process was ordered as in figure 1. A-B. In the cells the nucleus broke asymmetrically into different parts with different sizes and shapes, which was an ability to distinguish between an apparently cleaving nucleus and the possibility that the previous division was faulty and nuclei were fusing again. The division without visible chromosomes and spindles started through the breaking of nucleus from one side and formed a cleavage furrow (Figure 1A). The cleavage furrow expanded to an other side and finally the originated nucleus cleaved into two parts. Before ending of the division, the new-formed nuclei could begin to divide a second cycles. The nucleus was seemingly divided in a random way. As result the two daughter nuclei do not always fit into the binary series of nuclear material. Moreover the division could produce more nuclei with different sizes in cell (Fig, 1B ) and lead to irregular bi-, tri- and multinucleated cells.
3.3 Process of the nuclear constriction
The nuclear constriction process is constructed according to the nuclear division figure 1. C-E . In the Figure 1C the nucleus envelope is constricted in the middle of the nucleus of the cell. Then the constriction furrow expanded towards the centre of the nucleus. In the end, it could produce two equal size daughter nuclei of the cell (Fig. 1D ).
Both processes of the nuclear division had different division figure and different result from each other. However, they had a common characteristic in that the nucleus divided directly into two or more daughter nuclei without the appearance of visible chromosomes and without the appearance of visible spindles as well as without disappearance of the nucleus envelope. These are key differences with mitosis, and are identifiable with the direct nuclear division, amitosis. Therefore, both nuclear division in nuclear cleavage and constriction belong to the amitosis. In other word, the amitosis exist in different ways.
4. Discussion
It is well-known that cells in animal have no cell wall, an individual live cell of animal tissue was usually used to investigate of a cell development with the correlation of a time line (Sluder et al. 1997）. However, the histological images are available today for the investigation of the cell development in the plant tissue because of the cell wall.
According to the morphologic change of the amitotic nucleus division, Chen and Wan (1986) suggested that amitosis consist of four stages: (1) The nucleolus divide into two parts, (2) the two nucleoli moving toward the two sides of the stretching nucleus, (3) the nuclear membrane constriction, (4) the two daughter nuclei are formed. Valente (1998) proposed to divide the nuclear amitosis process into four stages with condensation of the DNA, absence of nucleoli, nucleus elongation and constriction, and constriction producing two daughter nuclei. In this investigation, the amitotic division had no clear stages to distinguish from each other.
It was impossible to ensure precisely the identical division of chromosome numbers or the ploidy levels of the daughter nuclei in the amitotic nuclear division because of the absence of the separation of the sister chro-mosomes by amitotic division. Therefore, the amitosis lead easily to form chromosome variations, and to produce the mixoploidy tissue.
Whether the cell division would follow after the nuclear amitotic division has been disputed for long time. In this work, the cytokinesis after the amitotic nuclear division was observed, in which, the cytoplasm directly divided into two parts accompanying the daughter nuclei and formed two daughter cells: the large part of the nucleus had more cytoplasm than the small part of the nucleus (Fig, 1E ). It showed that the cell division could arise after the amitotic nuclear division, but the cytokinesis did not always follow amitotic nuclear division as normal cell cycle phase of growth and differentiation (Miller 1980).
Amitosis was observed in most cases by pathological cancer cells (Bhattathiri 2001) and mutated cells (Torre and Martin 1975). Some authors considered that the amitosis was a misinterpretation of the mitosis and it leads the cell to degenerate (Pfitzer 1980). Altamura et al. (1991) had observed that amitosis always preceded mitosis in tissue cultures of Nicotiana tabacum cv. Isakova and Shilova (2003) considered that the cells produced via different forms of amitosis ways play different roles in trophoblast differentiation. This investigation supports the opinion that amitosis was an alternative to mitosis that often accompanies the differentiation of the cells in eukaryote organism.
Isakova and Shilova（2004）observed some endopolyploidy nuclei in trophoblast cells undergo direct division, which leads to the increase in cell numbers. In this study, the amitosis was only observed in polyploid cells in epidermal layers. There was a close relationship between the amitosis and the polyploidy cells. The absence of chromosomes by amitosis process was similar in morphology to the endoreduplication, where the S-phase and G-phase were repeated excluding the M-phase (Grafi 1998). Therefore, the amitosis has possibly a close relation with the endoreduplication. The endoreduplicated cells could be depolyploidized by amitosis.
5. Acknowledgements
I thank Prof. MD. Sacristan at Free University of Berlin, Prof. F. Pohlheim and Dr. C. Lehmann at Humboldt University of Berlin in Germany for the support of this work.
Reference
[1]Altamura MM, Capitani FD, Serafini-Fracassini P Torrigiani and Falasca G （1991）. Root histogenesis from tobacco in thin cell layers.- Protoplasma 161: 31-42
[2]Appezzato-da-GlóriaI, B. and Machado SR ( 2004). Ultrastructural analysis of in vitro direct and indirect organo-genesis.- Rev. bras. Bot. 27(3): 429-437
[3]Bhattathiri VN (2001). Amitotic cell divisions and tumour growth: an alternative model for cell kinetic compartments in solid tumours -Oral Oncology 37: 288-295
[4]Böck P (1989). Romeis-mikroskopische Technik. 17. Auflage: Urban & Schwarzenberg Verlag. 348-355.
[5]Chen YQ and Wan BK ( 1986). A study on amitosis of the nucleus of the mammalian cell. I. A study under the light and transmission electron microscope- Acta anatomica.127: 69-76
[6]Grafi G (1998). Cell Cycle Regulation of DNA Replication:The Endoreduplication Perspective-Experimental Cell. Research, 244: 372–378
[7]Isakova, GK and Mead RA (2004). Occurrence of amitotic division of trophoblast cell nuclei in blastocysts of the western spotted skunk (Spilogale putorius latifrons). Hereditas, 140: 177-184
[8]Isakova, GK. and IE Shilova (2003). The Ratio between the Frequencies of Two Forms of Amitotic Division of Trophoblast Cell Nuclei in the Mink Blastocysts during the Delayed Implantation Period. Biology Bulletin. 30(4): 322–324
[9]Li Mingyin (2007) . A Method for Direct Determination of Ploidy Level of Somatic Cells in Different Layers of Cytochimeral Tissue of Pelargonium zonale, Scientia Silvae Sinicae. 07: 125-127
[10]Miller RH (1980). Amitosis and Endocytogenesis in the fruit of Malus sylvestris. Annals of Botany. 46: 567 – 575
[11]Marciniak K (1991). Cytophotometric analysis of amitosis in nuclear endosperm of Vicia faba. Folia Histochemical Cytobiology. 29(2): 67-69
[12]Pfitzer P (1980). Amitosis: a historical misinterpretation? Pathology. Research and Practice. 167: 292-300
[13]Rieger R, Michaelis A and Green MM (1991). Glossary of genetics classical and Molecular. Berlin. Springer Verlag
[14]Sluder, GE A. Thompson, F J. Miller, J. Hayes and Rieder C L (1997). The checkpoint control for anaphase onset does not monitor excess numbers of spindle poles or bipolar spindle symmetry- Journal of Cell Science 110: 421-429
[15]Torre DL and Martin GG (1975). The nucleolus in the induced amitosis. Journal of Experimental Botany. 26: 713-721
[16]Valente P. Tao W and Verbelen JP (1998). Auxins and cytokinins control DNA endoreduplication and deduplication in single cells of tobacco. Plant Science. 134: 207–215
天竺葵表皮细胞无丝分裂的观察
李明银
绵阳师范学院园林科学研究所，四川绵阳（621000）
摘 要：无丝分裂是一种稀有的细胞分裂形式，多见于动物细胞中，少见于植物细胞。本文在天竺葵表皮多倍体细胞研究中首次观察到劈裂和缩裂两种不同的细胞核无丝分裂方式。同时观察到伴随细胞核分裂的细胞质分裂，并形成多个子细胞。研究显示：无丝分裂可导致形成遗传物质非均匀的多核细胞。研究认为无丝分裂可能是细胞核内复制的一种分裂形式。
关键词：天竺葵，表皮细胞，无丝分裂、核内复制，核劈裂，核缩裂
A B C
D E
Fig. 1: Direct nuclear division without visible chromosomes in epidermal cells of Pelargonium zonale clone 5/74/2. A Nucleus cleaved into two parts with different size; One of the part began to divide in second cycle, before the end of first division; B. A cell contained three different nuclei; C. Reniforme nucleus showed a constricted furrow; D. Two nuclei were formed; E. The cell constriction after the nuclear constriction.
Observation of two Amitotic way in the Epidermal Cells of
the Plant Pelargonium Zonale `Kleiner Liebling` 1
Li Mingyin
School of Life Science and Engineering, Mianyang Normal University, Mianyang, Sichuan,
China (621000)
Institute of Garden Science, Humboldt University of Berlin, Germany (14195)
E-mail: ,
Abstract
Amitosis, different from mitosis, is a rare form of the proliferation of the cells. Most amitosis were observed in animal cells; only few of them were reported in plant cells. The cytological investigation in this study demonstrated first time in Pelargonium zonale two different amitotic nuclear division ways ：cleavage and constriction，in which no appearance of the visible chromosomes and no spindles were observed. After amitotic nuclear division the cytokinesis was also observed, in which the cytoplasm divided directly into two or more parts accompany with formation of two or more daughter cells. This study showed the genetic material may sometimes be unequally distributed between the daughter cells in amitosis, and the amitosis could lead to bi-, tri- and multinucleated cells. It was suggested that amitosis could be a way of the division of the endoreduplicated cells.
Keywords: Pelargonium; epidermal cell; amitosis; endoreduplication; nucleus cleavage; nucleus constriction.
1. Introduction
Amitosis (a-mitosis) was suggested by Rieger, et al. (1991) as a direct nuclear division other than mitosis and it was defined that the nucleus by amitosis divided directly without the visible chromosomes and spindles. The most amitotic division was observed in certain types of animal cells (Chen and Wan 1986; Bhattathiri 2001；Isakova and Shilova 2003; Isakova1 and Mead 2004). There were only a few reports of amitoses in plant special tissue (Miller 1980; Marciniak 1991; Appezzato-da-Glória and Machado 2004) as well as in treated tissue (Torre and Martin 1975), or in tissue culture of tobacco (Altamura et al. 1991; Valente et al., 1998). Therefore，amitotic division occurs rarely and was poorly studied in plant. In this present study, many cells with intranuclear structure characteristics of amitosis were observed in the epidermal cells of the muted clone 5/74/2 by Pelargonium zonale, in which chromosomes, spindles as well as nucleolus division had not observed. Basen on morphologic changes of the cell nucleus division, it was suggested that two amitotic models existed.
2. Materials and Methods
The investigated plant was cloned 5/74/2, which is one of the mutants of the haploid plant `Kleiner Liebling` of Pelargonium zonale from Humboldt University of Berlin. It had different ploidy levels in epidermis of the leaf tissue. The material treatment und methods for investigation were made on the basis of Li Mingyin (2007).
2.1 Preparation of the sample
The shoots tips were fixed in carnoy II for 24 hours and then soaked in ethylenglycolmonoethylether, 96% ethanol, propane and butane sequentially each for 24 hours. After that the shoot tip samples were polymerized in an embedding solution, containing 100 ml Technovit 7100 (Germany) and 1 g dibenzoylperoxid for 24 hours. Then they were carefully 1 The investigation was carried out in Humboldt university of Berlin; the manuscript is finished in Mianyang Normal University
placed in embedding capsules with mixture solution (10 ml above embedding solution and 1 ml dimetylsulfoxid) and to solidifying for 24 hours. The embedded shoot tips were sectioned to 8 -10 µm with a rotation microtom.
2.2 Staining of the samples
The slices of the plant tissue were stained in diluted (1:1 with distilled water) toluidinblue solution (60 ml of 1% toluidinblue water solution was mixed with 30 ml of 2.5% natriumcarbonat solution and 10 ml of 70% alcohol) for ca. 30 -60 second and then washed with running water (Böck 1989). After drying, the well stained tissue slices on the slide were covered with a cover slip using DPX solution (Fluka) and stored in the dark for investigation.
3. Results
3.1 Definition and character of amitosis
In this study, it had been observed in histological serial sections that the cells arranged irregularly in the epidermal layer，a nucleus directly divided into two or more parts, without appearance of the visible chromosomes and without appearance of the visible spindles (Fig. 1A-E ). The most figures of the nuclear division ordered in groups of shape were considered as a between (middle) stage of the nuclear division. On the basis of the morphological characteristics, the nucleus division without visible chromosomes and spindles could be constructed into two different processes of the nuclear division with cleavage and constriction.
3.2 Process of the nuclear cleavage
The nuclear cleavage division process was ordered as in figure 1. A-B. In the cells the nucleus broke asymmetrically into different parts with different sizes and shapes, which was an ability to distinguish between an apparently cleaving nucleus and the possibility that the previous division was faulty and nuclei were fusing again. The division without visible chromosomes and spindles started through the breaking of nucleus from one side and formed a cleavage furrow (Figure 1A). The cleavage furrow expanded to an other side and finally the originated nucleus cleaved into two parts. Before ending of the division, the new-formed nuclei could begin to divide a second cycles. The nucleus was seemingly divided in a random way. As result the two daughter nuclei do not always fit into the binary series of nuclear material. Moreover the division could produce more nuclei with different sizes in cell (Fig, 1B ) and lead to irregular bi-, tri- and multinucleated cells.
3.3 Process of the nuclear constriction
The nuclear constriction process is constructed according to the nuclear division figure 1. C-E . In the Figure 1C the nucleus envelope is constricted in the middle of the nucleus of the cell. Then the constriction furrow expanded towards the centre of the nucleus. In the end, it could produce two equal size daughter nuclei of the cell (Fig. 1D ).
Both processes of the nuclear division had different division figure and different result from each other. However, they had a common characteristic in that the nucleus divided directly into two or more daughter nuclei without the appearance of visible chromosomes and without the appearance of visible spindles as well as without disappearance of the nucleus envelope. These are key differences with mitosis, and are identifiable with the direct nuclear division, amitosis. Therefore, both nuclear division in nuclear cleavage and constriction belong to the amitosis. In other word, the amitosis exist in different ways.
4. Discussion
It is well-known that cells in animal have no cell wall, an individual live cell of animal tissue was usually used to investigate of a cell development with the correlation of a time line (Sluder et al. 1997）. However, the histological images are available today for the investigation of the cell development in the plant tissue because of the cell wall.
According to the morphologic change of the amitotic nucleus division, Chen and Wan (1986) suggested that amitosis consist of four stages: (1) The nucleolus divide into two parts, (2) the two nucleoli moving toward the two sides of the stretching nucleus, (3) the nuclear membrane constriction, (4) the two daughter nuclei are formed. Valente (1998) proposed to divide the nuclear amitosis process into four stages with condensation of the DNA, absence of nucleoli, nucleus elongation and constriction, and constriction producing two daughter nuclei. In this investigation, the amitotic division had no clear stages to distinguish from each other.
It was impossible to ensure precisely the identical division of chromosome numbers or the ploidy levels of the daughter nuclei in the amitotic nuclear division because of the absence of the separation of the sister chro-mosomes by amitotic division. Therefore, the amitosis lead easily to form chromosome variations, and to produce the mixoploidy tissue.
Whether the cell division would follow after the nuclear amitotic division has been disputed for long time. In this work, the cytokinesis after the amitotic nuclear division was observed, in which, the cytoplasm directly divided into two parts accompanying the daughter nuclei and formed two daughter cells: the large part of the nucleus had more cytoplasm than the small part of the nucleus (Fig, 1E ). It showed that the cell division could arise after the amitotic nuclear division, but the cytokinesis did not always follow amitotic nuclear division as normal cell cycle phase of growth and differentiation (Miller 1980).
Amitosis was observed in most cases by pathological cancer cells (Bhattathiri 2001) and mutated cells (Torre and Martin 1975). Some authors considered that the amitosis was a misinterpretation of the mitosis and it leads the cell to degenerate (Pfitzer 1980). Altamura et al. (1991) had observed that amitosis always preceded mitosis in tissue cultures of Nicotiana tabacum cv. Isakova and Shilova (2003) considered that the cells produced via different forms of amitosis ways play different roles in trophoblast differentiation. This investigation supports the opinion that amitosis was an alternative to mitosis that often accompanies the differentiation of the cells in eukaryote organism.
Isakova and Shilova（2004）observed some endopolyploidy nuclei in trophoblast cells undergo direct division, which leads to the increase in cell numbers. In this study, the amitosis was only observed in polyploid cells in epidermal layers. There was a close relationship between the amitosis and the polyploidy cells. The absence of chromosomes by amitosis process was similar in morphology to the endoreduplication, where the S-phase and G-phase were repeated excluding the M-phase (Grafi 1998). Therefore, the amitosis has possibly a close relation with the endoreduplication. The endoreduplicated cells could be depolyploidized by amitosis.
5. Acknowledgements
I thank Prof. MD. Sacristan at Free University of Berlin, Prof. F. Pohlheim and Dr. C. Lehmann at Humboldt University of Berlin in Germany for the support of this work.
Reference
[1]Altamura MM, Capitani FD, Serafini-Fracassini P Torrigiani and Falasca G （1991）. Root histogenesis from tobacco in thin cell layers.- Protoplasma 161: 31-42
[2]Appezzato-da-GlóriaI, B. and Machado SR ( 2004). Ultrastructural analysis of in vitro direct and indirect organo-genesis.- Rev. bras. Bot. 27(3): 429-437
[3]Bhattathiri VN (2001). Amitotic cell divisions and tumour growth: an alternative model for cell kinetic compartments in solid tumours -Oral Oncology 37: 288-295
[4]Böck P (1989). Romeis-mikroskopische Technik. 17. Auflage: Urban & Schwarzenberg Verlag. 348-355.
[5]Chen YQ and Wan BK ( 1986). A study on amitosis of the nucleus of the mammalian cell. I. A study under the light and transmission electron microscope- Acta anatomica.127: 69-76
[6]Grafi G (1998). Cell Cycle Regulation of DNA Replication:The Endoreduplication Perspective-Experimental Cell. Research, 244: 372–378
[7]Isakova, GK and Mead RA (2004). Occurrence of amitotic division of trophoblast cell nuclei in blastocysts of the western spotted skunk (Spilogale putorius latifrons). Hereditas, 140: 177-184
[8]Isakova, GK. and IE Shilova (2003). The Ratio between the Frequencies of Two Forms of Amitotic Division of Trophoblast Cell Nuclei in the Mink Blastocysts during the Delayed Implantation Period. Biology Bulletin. 30(4): 322–324
[9]Li Mingyin (2007) . A Method for Direct Determination of Ploidy Level of Somatic Cells in Different Layers of Cytochimeral Tissue of Pelargonium zonale, Scientia Silvae Sinicae. 07: 125-127
[10]Miller RH (1980). Amitosis and Endocytogenesis in the fruit of Malus sylvestris. Annals of Botany. 46: 567 – 575
[11]Marciniak K (1991). Cytophotometric analysis of amitosis in nuclear endosperm of Vicia faba. Folia Histochemical Cytobiology. 29(2): 67-69
[12]Pfitzer P (1980). Amitosis: a historical misinterpretation? Pathology. Research and Practice. 167: 292-300
[13]Rieger R, Michaelis A and Green MM (1991). Glossary of genetics classical and Molecular. Berlin. Springer Verlag
[14]Sluder, GE A. Thompson, F J. Miller, J. Hayes and Rieder C L (1997). The checkpoint control for anaphase onset does not monitor excess numbers of spindle poles or bipolar spindle symmetry- Journal of Cell Science 110: 421-429
[15]Torre DL and Martin GG (1975). The nucleolus in the induced amitosis. Journal of Experimental Botany. 26: 713-721
[16]Valente P. Tao W and Verbelen JP (1998). Auxins and cytokinins control DNA endoreduplication and deduplication in single cells of tobacco. Plant Science. 134: 207–215
天竺葵表皮细胞无丝分裂的观察
李明银
绵阳师范学院园林科学研究所，四川绵阳（621000）
摘 要：无丝分裂是一种稀有的细胞分裂形式，多见于动物细胞中，少见于植物细胞。本文在天竺葵表皮多倍体细胞研究中首次观察到劈裂和缩裂两种不同的细胞核无丝分裂方式。同时观察到伴随细胞核分裂的细胞质分裂，并形成多个子细胞。研究显示：无丝分裂可导致形成遗传物质非均匀的多核细胞。研究认为无丝分裂可能是细胞核内复制的一种分裂形式。
关键词：天竺葵，表皮细胞，无丝分裂、核内复制，核劈裂，核缩裂
A B C
D E
Fig. 1: Direct nuclear division without visible chromosomes in epidermal cells of Pelargonium zonale clone 5/74/2. A Nucleus cleaved into two parts with different size; One of the part began to divide in second cycle, before the end of first division; B. A cell contained three different nuclei; C. Reniforme nucleus showed a constricted furrow; D. Two nuclei were formed; E. The cell constriction after the nuclear constriction.