Meiotic pairing of B chromosomes, multiple sexual system, and Robertsonian fusion in the red brocket deer Mazama americana (Mammalia, Cervidae)

Abstract

ABSTRACT. Deer species of the genus Mazama show significant inter-and intraspecific chromosomal variation due to the occurrence of rearrangements and B chromosomes. Given that carriers of aneuploidies and structural rearrangements often show anomalous chromosome pairings, we here performed a synaptonemal complex analysis to study chromosome pairing behavior in a red brocket deer (Mazama americana) individual that is heterozygous for a Robertsonian translocation, is a B chromosome carrier, and has a multiple sex chromosome system (XY 1 Y 2 ). The synaptonemal complex in spermatocytes showed normal chromosome pairings for all chromosomes, including the autosomal and sex trivalents. The electromicrographs showed homology among B chromosomes since they formed bivalents, but they also appeared as univalents, indicating their anomalous behavior and non-Mendelian Meiotic pairing in a red brocket deer segregation. Thus, synaptonemal complex analysis is a useful tool to evaluate the role of B chromosomes and rearrangements during meiosis on the intraspecific chromosomal variation that is observed in the majority of Mazama species.

Dual mechanism of chromatin remodeling in the common shrew sex trivalent (XY 1Y 2)

“…It is interesting that the autosomal part of the sex trivalent is directed into the meiotic nucleus. A similar synapsis of sex chromosomes and the formation of electron-dense material around the true sex chromosome regions within the XY 1 Y 2 trivalent were identified previously in the bat Artibeus lituratus ( Solari and Pigozzi 1994 ) and the deer Mazama americana ( Aquino et al 2013 ). A similar pattern of synapsis in the sex trivalent was also detected in some species of gerbils ( Wahrman et al 1983 ; Ratomponirina et al 1986 ) and in the muntjac; however, in the last case it was difficult to identify clearly the synaptic participants in the absence of electron micrographs ( Pathak and Lin 1981 ).…”

“…Translocation between the X and an autosome results in the formation of multiple sex chromosomes (XY 1 Y 2 ; where the X is a product of a translocation between the ‘true’ X and an autosome, Y 1 is the ‘true’ Y and Y 2 is the autosome). The XY 1 Y 2 condition has been demonstrated in insects ( Jacobs 2003 ), fish ( Centofante et al 2006 ; de Oliveira et al 2008 ) and, in particular, among mammals – including marsupials: greater bilby Macrotis lagotis ( Sharp 1982 ), and placentals: Indian muntjac Muntiacus muntjak ( Artiodactyla , Fronicke and Schertan 1997), red brocket deer Mazama americana ( Artiodactyla , Aquino et al 2013 ), big fruit-eating bat Artibeus lituratus ( Chiroptera , Solari and Pigozzi 1994 ), short-tailed fruit bat Carollia perspicillata ( Chiroptera , Noronha et al 2009 ), delicate mouse Salinomys delicates ( Rodentia , Lanzone et al 2011 ), Sahel gerbil Taterillus arenarius and Senegal gerbil Taterillus pygargus ( Rodentia , Ratomponirina et al 1986 ; Volobouev and Granjon 1996 ) and others (see reviews by Fredga 1970 ; Sharman 1991 ; and Yoshida and Kitano 2012 ). An XY 1 Y 2 sex chromosome system also characterises species of shrews (small insectivores) belonging to the Sorex araneus group ( Eulipotyphla ; Hausser et al 1985 ), including the Eurasian common shrew Sorex araneus Linnaeus, 1758 which is a model system for evolutionary cytogenetics with numerous Robertsonian autosomal variants as well as the XY 1 Y 2 condition ( Searle and Wójcik 1998 ).…”

Intrapopulation Chromosomal Polymorphism in <b><i>Mazama gouazoubira</i></b> (Cetartiodactyla; Cervidae): The Emergence of a New Species?

“…However, heterozygotes for a single centric fusion generally form trivalents in meiosis, causing minimal problems in reproduction [Baker and Bickham, 1986], as observed in a meiotic study performed on M. americana [Aquino et al, 2013]. However, Cursino et al [2014] and Salviano et al [2017] verified that hybrids of different M. americana cytotypes possess a mechanism of post-zygotic reproductive isolation that involves subfertility or infertility, demonstrating reproductive isolation with the accumulation of chromosomal rearrangements.…”

Biomechanical evaluation of spring system for implant-supported prosthesis: analysis by photoelasticity and extensometry

“…The red brocket deer (Mazama americana) is one of the best examples for a large mammal of karyotypic diversification leading to true sympatric speciation (see Amato et al, 2000, andHuang et al, 2006, for a similar case in Muntiacus reevesi). Members of this species complex (Abril et al, 2010;Aquino et al, 2013;Cursino et al, 2014), currently occur in forest habitats (Bodmer, 1997;Duarte, 1996;Escobedo-Morales et al, 2016;Varela et al, 2010) throughout a wide distribution range from México to the north of Argentina (Eisemberg, 1989;Emmons, 1990). Earlier studies described up to eight different species within the red brocket deer complex (Allen, 1915) that were later included in one with a variable number (9-15) of subspecies (Cabrera, 1960;Czernay, 1987;Rossi, 2000).…”

“…The analysis of the cytogenetic evolution has recently shown the existence of two karyotypic lineages that evolved from a common ancestor by chromosomal rearrangements: Lineage A, which includes the Rondônia and Juína karyotypes; and Lineage B, which includes the Jarí, Carajás, Santarém, and Paraná karyotypes (Abril et al, 2010). Both lineages are also well differentiated at the level of mtDNA (Abril et al, 2010) and maintain reproductive isolation, with hybrids showing sterility or subfertility (Aquino et al, 2013;Cursino et al, 2014;Salviano et al, 2017). All these results clearly point to the existence of at least two separate species within the current Mazama americana specific nomination, which need to be formally described, and probably a deeper investigation could reveal further subdivisions under an ongoing process of rapid sympatric speciation based on chromosomal rearrangements (Abril et al, 2010).…”