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

  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},
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

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

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

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

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)

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)

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

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)

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



Allozymic and cytological evidence for hemiclonal, all‐paternal, and mosaic offspring of the hybridogenetic stick insect Bacillus rossius‐grandii grandii

Bacillus and other unisexuals provide evidence of numerous reproductive interactions between hybrids and their bisexual relatives: the occurrence of such interactions may play an important role in the persistence, diversification and evolution of un bisexuals.

The chromosome complement of the hybrid Bacillus whitei complex (Insecta phasmatodea). I : The paleo- and neo-standard karyotypes

C-positive satellites and corresponding Ag-NOR, are found on a wide array of chromosomes, mostly reflecting those of both parental species, but also on new locations, but rather useful in short-term comparisons.

Cytology of Parthenogenesis in Bacillus whitei and Bacillus lynceorum (Insecta Phasmatodea)

These cytological findings fully support the genetic features ascertained for the two hybrids and provide evidence of their different and very likely independent meiotic adaptations to parthenogenetic reproduction.

Reproductive features of homospecific hybridogenetically‐derived stick insects suggest how unisexuals can evolve

These reproductive modes suggest a likely evolutionary dynamic for newly originated hybridogens: to achieve stability, an interruption of reproductive interactions with the maternal ancestor seems necessary in stick insects, and the microevolutionary pathway suggested by the ecological scenario also supports the possibility that a shift of hemiclonal stick insect strains to clonality has occurred.

The Chromosome Complement of the Hybrid Bacillus whitei Complex (Insecta Phasmatodea)

This study analyzes cytotypes of the hybrid Bacillus whitei complex and suggests their derivation from the standard “paleo” -karyotype mainly through Robertsonian fissions of the largest chromosomes and a few heterozygous translocations.

Genome exclusion in gametogenesis by an interspecific Rana hybrid: Evidence from electrophoresis of individual oocytes

Examination of electrophoretic markers for four loci from 860 individual oocytes revealed no evidence of either heterozygosity or recombination in the oocytes, consistent with a premeiotic exclusion of the lessonae genome, but do not require it.

Diversity in the Reproductive Modes of Females of the Rutilus alburnoides Complex (Teleostei, Cyprinidae): A Way to Avoid the Genetic Constraints of Uniparentalism

Recruitment by the types of diploid and triploid females discussed here introduces high genotypic diversity into hybrid populations, and allows purging of deleterious genes and incorporation of beneficial mutations in the same genome, characteristics believed to be major advantages of sexual reproduction.

Mate recognition and gamete cytology features allow hybrid species production and evolution in Bacillus stick insects

Morphological, karyological and genetic analyses clearly show that, owing to their persistence and incomplete reproductive isolation from ancestors, several all‐female complexes are much more diversified than generally assumed and that they may also have an evolutionary role.


  • F. TintiV. Scali
  • Biology
    Evolution; international journal of organic evolution
  • 1996
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.


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.