New DAPI and fish findings on egg maturation processes in related hybridogenetic and parthenogenetic Bacillus hybrids (insecta, phasmatodea)

@article{Marescalchi2001NewDA,
  title={New DAPI and fish findings on egg maturation processes in related hybridogenetic and parthenogenetic Bacillus hybrids (insecta, phasmatodea)},
  author={Ombretta Marescalchi and Valerio Scali},
  journal={Molecular Reproduction and Development},
  year={2001},
  volume={60}
}
Bacillus stick insects have proved adequate for studying a wide array of reproductive modes: sexual, parthenogenetic, hybridogenetic, androgenetic. Hybridogenetic strains (B. rossius‐grandii) were thought to discard the paternal “grandii” haploset during first meiotic division and keep the “rossius” hemiclone, whereas the clonal B. whitei (=rossius/grandii) would maintain its hybrid structure by fusing back two nonsister nuclei—each derived from previously segregated heterospecific complements… 

Automictic parthenogenesis in the diploid-triploid stick insect Bacillus atticus and its flexibility leading to heterospecific diploid hybrids

TLDR
The maintenance of some recombination during prophase I and the ability to produce diploid and triploid hybrids demonstrates that these parthenogenetic strains are neither invariant nor reproductively isolated from related taxa, as also occurs in other unisexuals.

Linkage between sexual and asexual lineages: genome evolution in Bacillus stick insects

TLDR
An overall picture of genomic diversification of parthenogens is therefore beginning to emerge, and the term meta-sexual is proposed to define those animals that reproduce by non-canonical sexual modes, but make use of egg and meiotic mechanisms.

Multiple lines of evidence suggest mosaic polyploidy in the hybrid parthenogenetic stick insect lineage Acanthoxyla

TLDR
A mechanism for the evolution of the Acanthoxyla lineage is proposed and it is suggested that interpretation may be complicated by the presence of individuals that are diploid and triploid mosaics.

Parental species and hybrid descendants of Bacillus (Insecta Phasmatodea) show different patterns of highly amplified, colocalized ribosomal and telomeric sequences

TLDR
Investigating by dual-color fluorescence in situ hybridization (FISH) with 28S ribosomal and (TTAGG)n telomeric probes all species of the circum-Mediterranean genus Bacillus encompassing bisexual and parthenogenetic taxa showed a significant occurrence of chromosome breakages and rearrangements.

Centrosome dynamics and inheritance in related sexual and parthenogenetic Bacillus (Insecta Phasmatodea)

TLDR
It has been shown that in sexually reproducing species the spermatozoon does not contribute the centriole, so that the egg wholly provides the MTOC and the ensuing anastral spindle of the embryo.

Unisexuality and Molecular Drive: Bag320 Sequence Diversity in Bacillus Taxa (Insecta Phasmatodea)

TLDR
Different reproductive modes (sexual/parthenogenetic) appear to explain observed variability trends, supporting Dover's hypothesis of sexuality acting as a driving force in the fixation of sequence variants, but the present analyses also highlight current spreading of new variants in B. grandii maretimi specimens and point to a biased sequence inheritance at the time of hybrid onset in the apomictic hybrids B. lynceorum.

Parthenogenesis and developmental constraints

TLDR
The absence of a paternal contribution in an unfertilized ovum presents two developmental constraints against the evolution of parthenogenesis, which can apparently rather easily evolve, for example, from facultative to obligate parthenogenic, or from pseudoarrhenotoky to haplodiploidy.

Genome size of the northern walkingstick, Diapheromera femorata (Phasmida: Heteronemiidae)

TLDR
The haploid genome size (C value) of the northern walkingstick, Diapheromera femorata(Say), was esti- mated to be 1C = 2.55 pg using Feulgen image-analysis densitometry of haemocyte and sperm nuclei, consistent with hypoth- eses regarding an upper limit to the size of many insect genomes imposed by the process of metamorphosis.

Evolution & Development

  • 2019

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TLDR
Stick insects of the genus Bacillus provide evidence for reproductive interactions between allodiploid parthenogens and their ancestors, and demonstrate that, through androgenesis, offspring of parthenogenetic hybrid females can contribute specimens of both sexes to the fathering species when fertilized by syntopic ancestral males.

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TLDR
Although Brm‐gp hybrids are still able to reproduce by hybridogenesis, a progressive disruption of the hybridogenetic‐androgenetic system takes place in synthetic B. rossius (Brm‐rp, Brprp) and abundant thelytokous parthenogenetic offspring are obtained from females of androgenetic origin.