Gynandromorphs and intersexes: potential to understand the mechanism of sex determination in arthropods

Abstract

Arthropods are sexually dimorphic. An arthropod individual usually diff erentiates into a male or a female. With very low frequencies, however, individuals with both male and female morphological characters have repeatedly been found in natural and laboratory populations of arthropods. Gynandromorphs (i.e., sexual mosaics) are genetically chimeric individuals consisting of male and female tissues. On the other hand, intersexes are genetically uniform (i.e., complete male, complete female or intermediate in every tissue) but all or some parts of their tissues have either a sexual phenotype opposite to their genetic sex or an intermediate sexual phenotype. Possible developmental processes (e.g., double fertilization of a binucleate egg, loss of a sex chromosome or upregulation/downregulation of sex-determining genes) and causal factors (e.g., mutations, genetic incompatibilities, temperatures or endosymbionts) for the generation of gynandromorphs and intersexes are reviewed and discussed.

A scientific note on an anomalous diploid individual of Euglossa melanotricha (Apidae, Euglossini) with both female and male phenotypes

“…Thus, our results indicate that the gynander of E. melanotricha shows morphological and genetic (i.e., diploidy) characteristics predominantly of the female sex. On the other hand, when considering the genetic uniformity of phenotypically different tissues (male and female) of this individual, the gynandromorph of E. melanotricha seems to fit better in the category of intersex bee, in accordance with the definition presented by Narita et al (2010).…”

Register of a gynandromorph of Euglossa pleosticta Dressler (Hymenoptera, Apidae)

“…Intersex individuals are genetically uniform, but gene expression is compromised, since the specimen exhibits phenotypic characteristics of the opposite sex (Ramos & Ruz 2013). Some of the known causes for these deviant genotypes involve hormonal abnormalities, chromosomal aberrations, differences in expression of sex determination genes and parasites such as Strepsiptera (Michez et al 2009;Narita et al 2010). Based solely on morphological analysis, it is difficult to attribute the case of a particular specimen to gynandromorphy or intersexuality, so we prefer to adopt the term gynandromorph in a broader sense herein.…”

Cytogenetic basis of thelytoky in Apis mellifera capensis

“…In some honey bee strains, it is common for an embryo to develop from a zygote (the union of an egg and sperm) and from a secondary sperm cell. Adults arising from such eggs are gynandromorphs with some diploid (female) tissue and some haploid (male) tissue (Rothenbuhler et al 1952;Tucker 1958;Narita et al 2010). …”