Karyotype analysis and sex determination in Australian Brush-turkeys (Alectura lathami)

Abstract

Sexual differentiation across taxa may be due to genetic sex determination (GSD) and/or temperature sex determination (TSD). In many mammals, males are heterogametic (XY); whereas females are homogametic (XX). In most birds, the opposite is the case with females being heterogametic (ZW) and males the homogametic sex (ZZ). Many reptile species lack sex chromosomes, and instead, sexual differentiation is influenced by temperature with specific temperatures promoting males or females varying across species possessing this form of sexual differentiation, although TSD has recently been shown to override GSD in Australian central beaded dragons (Pogona vitticeps). There has been speculation that Australian Brush-turkeys (Alectura lathami) exhibit TSD alone and/or in combination with GSD. Thus, we sought to determine if this species possesses sex chromosomes. Blood was collected from one sexually mature female and two sexually mature males residing at Sylvan Heights Bird Park (SHBP) and shipped for karyotype analysis. Karyotype analysis revealed that contrary to speculation, Australian Brush-turkeys possess the classic avian ZW/ZZ sex chromosomes. It remains a possibility that a biased primary sex ratio of Australian Brush-turkeys might be influenced by maternal condition prior to ovulation that result in her laying predominantly Z- or W-bearing eggs and/or sex-biased mortality due to higher sensitivity of one sex in environmental conditions. A better understanding of how maternal and extrinsic factors might differentially modulate ovulation of Z- or W-bearing eggs and hatching of developing chicks possessing ZW or ZZ sex chromosomes could be essential in conservation strategies used to save endangered members of Megapodiidae.

Exploration of an XX/XY Sex Determination System and Development of PCR-Based Sex-specific Markers in Procambarus clarkii Based on Next-Generation Sequencing Data

“…Generally, the genetic system of sex determination for a species could be uncovered through descent identification or karyotype analysis ( Malecha et al, 1992 ; Ortega et al, 2017 ). Presently, high-throughput sequencing has been used as a rapid and efficient way to uncover the sex determination system of an organism ( Pan et al, 2015 ; Ou et al, 2017 ; Shi X. et al, 2018 ; Gao et al, 2019 ; Yang et al, 2020 ).…”

Tavuk, Bıldırcın ve Hibritlerinin Kromozom Karyotipleri ve Bantlanma Modeli Analizi

“…Chickens have a large number of microchromosomes; therefore, it is inconvenient to count and describe the chromosomal morphology. Some studies have demonstrated that the incomplete karyotypes of the first 10 chromosomes in birds can represent a species-specific karyotype [3] .…”

Sex Determination in Homo sapiens as a Multi-Step Process: Potential for Development of Variants and Sex Differences in Disease Risk

“…In contrast, this temperaturedependent loss of males does not occur in birds [discussed in [47]] but other temperature-dependent effects may be operative [48]. Interestingly in many bird species, females are heterogametic (ZW) while males are homogametic (ZZ) [discussed in [49]].…”