Achiasmatic meiosis and complex heterozygosity in female cyclopoid copepods (Copepoda, Crustacea)

Chinnappa, C. C.; Victor, Reginald

doi:10.1007/bf00292825

Cited by 23 publications

(8 citation statements)

References 10 publications

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“…meiotic segregation and sexual reproduction might nevertheless occur is suggested by an atypical form of meiosis known in some species of the genus Oenothera and in certain other plants (Cleland 1972;Holsinger and Ellstrand 1984;Golczyk 2011;Rauwolf et al 2011;Golczyk et al 2014). In these plants and perhaps in some animals (Chinnappa and Victor 1979;Gross et al 2009;Schneider et al 2009), instead of synapsing side by side, chromosomes join end to end to form rings in which paternal and maternal chromosomes alternate. At first meiotic anaphase, maternal and paternal chromosomes segregate to opposite poles without genetic exchange except in telomeric regions, thereby keeping chromosomes of the same parentage together generation after generation as independently inherited units, known as Renner complexes ( Figure 5).…”

Section: Oenothera-like Meiosismentioning

confidence: 99%

Allele Sharing and Evidence for Sexuality in a Mitochondrial Clade of Bdelloid Rotifers

et al. 2015

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Rotifers of Class Bdelloidea are common freshwater invertebrates of ancient origin whose apparent asexuality has posed a challenge to the view that sexual reproduction is essential for long-term evolutionary success in eukaryotes and to hypotheses for the advantage of sex. The possibility nevertheless exists that bdelloids reproduce sexually under unknown or inadequately investigated conditions. Although certain methods of population genetics offer definitive means for detecting infrequent or atypical sex, they have not previously been applied to bdelloid rotifers. We conducted such a test with bdelloids belonging to a mitochondrial clade of Macrotrachela quadricornifera. This revealed a striking pattern of allele sharing consistent with sexual reproduction and with meiosis of an atypical sort, in which segregation occurs without requiring homologous chromosome pairs.KEYWORDS clonal erosion; cyclic parthenogenesis; meiosis; monogonont; Oenothera B DELLOID rotifers are minute freshwater invertebrates commonly found in lakes, streams, and ponds and in ephemerally aquatic environments such as rock pools and the water films on moss and lichens where they are able to survive because of their unusual ability to withstand desiccation. Although typically only several tenths of a millimeter in size, bdelloids have ganglia; muscles; reproductive, digestive, excretory, and secretory systems; photosensitive and tactile sensory organs; and structures for crawling, feeding, and swimming. Characterized by their ciliated head and bilateral ovaries and classified in four families and hundreds of morphospecies, their ancient origin is indicated by the considerable synonymous sequence divergence between families and by the finding of bdelloid remains in 35-to 40-million year old amber (Mark Welch et al. 2009).Despite much observation of field and laboratory populations and except for one heavily qualified account of having twice seen a male among many females in a sample from a lake (Wesenberg-Lund 1930), neither males, hermaphrodites, mating, nor meiosis have ever been reported within the class (Birky 2010). The only known mode of bdelloid reproduction is via eggs produced by two mitotic divisions from primary oocytes (Hsu 1956a,b). Most recently, further evidence suggestive of asexuality has come from genomic sequencing of the bdelloid Adineta vaga, showing it to be devoid of homologous chromosome pairs and therefore excluding the possibility of standard meiosis (Flot et al. 2013). Nevertheless, the possibility remains that bdelloids reproduce sexually under unknown or inadequately investigated conditions, employing a form of meiosis known in certain plants in which segregation occurs without homologous chromosome pairs-a possibility that can be tested by methods of population genetics.For any two individuals in a population descended from a common ancestor without sexual reproduction or any other sort of genetic transfer between individuals, the phylogenetic distance between a sequence in one individual and its Librar...

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Section: Oenothera-like Meiosismentioning

confidence: 99%

Allele Sharing and Evidence for Sexuality in a Mitochondrial Clade of Bdelloid Rotifers

et al. 2015

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“…Indeed, we suggest that the thin strands of Feulgen-positive chromatin surrounding the dense heterochromatin cores represent the duplicated somatic cell genome of M. edax in preparation for meiosis. Beermann (1977) and Chinnappa and Victor (1979) have identified this stage as early pachytene in their study of achiasmatic meiosis and complex heterozygosity in Mesocyclops edax. In the majority of specimens, the PD nuclei contain more DNA in females than in males.…”

Section: Discussionmentioning

confidence: 98%

Heterochromatin endoreduplication prior to gametogenesis and chromatin diminution during early embryogenesis in Mesocyclops edax (Copepoda: Crustacea)

Rasch

Wyngaard

Connelly

2008

Journal of Morphology

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The segregation of progenitor somatic cells from those of the primordial germ cells that sequester and retain elevated levels of DNA during subsequent developmental events, poses an interesting, alternative pathway of chromosome behavior during the reproductive cycle of certain species of cyclopoid copepods and several other organisms. Separation of maternal and paternal chromosome sets during very early cleavages (gonomery) is often a feature following marked elevations of DNA levels in germ cells for some of these species. Here, we report on the accumulation of large amounts of DNA in germ line nuclei of both female and male juveniles and adults of a freshwater copepod, Mesocyclops edax (Forbes, 1890). We also report the robust uptake of 3H-thymidine by germ cells prior to gametogenesis in this species. By using cytophotometric analysis of the DNA levels in both germ line cells and somatic cells from the same specimens we demonstrate that germ cell nuclei accumulate high levels of DNA prior to the onset of gametogenesis. These elevated amounts coincide with the levels of heterochromatic DNA discarded during chromatin diminution. A new model is proposed of major cytological events accompanying the process of chromatin diminution in M. edax.

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“…In scorpions, it is possible that the complete absence of chiasmata is an important mechanism for maintaining rearranged chromosomes in the populations. In bisexual species, the lack of chiasmata is invariably restricted to only one sex, generally the heterogametic, for example, the males of some Araneae (Rodríguez Gil et al 2002), Coleoptera (Serrano 1981), Diptera (Procunier 1975), Heteroptera (Ituarte and Papeschi 2004), Orthoptera (White 1973), Parachela (Altiero and Rebecchi 2003), and Pseudoscorpiones (Šťáhlavský and Král 2004), and the females of certain Copepoda (Chinnappa and Victor 1979), Lepidoptera (Traut and Clarke 1996), and Trichoptera (Suomalainen 1966). The only registers considering female scorpion cells in meiotic division were made by Shanahan (1989a, b), who observed some metaphase I oocytes with features similar to those verified in males and suggested that the female meiosis is achiasmatic.…”

Section: Discussionmentioning

confidence: 98%

Complex meiotic configuration of the holocentric chromosomes: the intriguing case of the scorpion Tityus bahiensis

et al. 2009

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Mitotic and meiotic chromosomes of Tityus bahiensis were investigated using light (LM) and transmission electron microscopy (TEM) to determine the chromosomal characteristics and disclose the mechanisms responsible for intraspecific variability in chromosome number and for the presence of complex chromosome association during meiosis. This species is endemic to Brazilian fauna and belongs to the family Buthidae, which is considered phylogenetically basal within the order Scorpiones. In the sample examined, four sympatric and distinct diploid numbers were observed: 2n = 5, 2n = 6, 2n = 9, and 2 = 10. The origin of this remarkable chromosome variability was attributed to chromosome fissions and/or fusions, considering that the decrease in chromosome number was concomitant with the increase in chromosome size and vice versa. The LM and TEM analyses showed the presence of chromosomes without localised centromere, the lack of chiasmata and recombination nodules in male meiosis, and two nucleolar organiser regions carrier chromosomes. Furthermore, male prophase I cells revealed multivalent chromosome associations and/or unsynapsed or distinctly associated chromosome regions (gaps, less-condensed chromatin, or loop-like structure) that were continuous with synapsed chromosome segments. All these data permitted us to suggest that the chromosomal rearrangements of T. bahiensis occurred in a heterozygous state. A combination of various factors, such as correct disjunction and balanced segregation of the chromosomes involved in complex meiotic pairing, system of achiasmate meiosis, holocentric nature of the chromosomes, population structure, and species dispersion patterns, could have contributed to the high level of chromosome rearrangements present in T. bahiensis.

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Achiasmatic meiosis and complex heterozygosity in female cyclopoid copepods (Copepoda, Crustacea)

Cited by 23 publications

References 10 publications

Allele Sharing and Evidence for Sexuality in a Mitochondrial Clade of Bdelloid Rotifers

Allele Sharing and Evidence for Sexuality in a Mitochondrial Clade of Bdelloid Rotifers

Heterochromatin endoreduplication prior to gametogenesis and chromatin diminution during early embryogenesis in Mesocyclops edax (Copepoda: Crustacea)

Complex meiotic configuration of the holocentric chromosomes: the intriguing case of the scorpion Tityus bahiensis

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