All XX Spanish Moles have ovotestes (both ovarian & testicular tissue) and make Eggs & Testosterone, but XY moles only have testes & Make Sperm. (Gender Showcase, 9-12)

Talpa occidentalis (mole, Iberian peninsula)

All females have ovotestes (ovotestes are gonads containing both ovarian & testicular tissue) XX have ovotestes & make eggs and testosterone only, XY have testes only and make sperm only.

Image caption: A Spanish blind mole emerges from underneath a rock. Photo credit (C) Tiago Magalhães.

Most gender-gene committees, with or without the presence of SRY, pass a resolution creating only a testis in males and only an ovary in females. In some species, though, even this most elemental aspect of bodily gender has been given a different configuration.

Among Talpa occidentalis—another burrowing mammal, an old world mole from the Iberian peninsula—all females have ovotestes, gonads containing both ovarian and testicular tissue. The ovotestes occur at the site in the body where simple ovaries are found in other species. 

Talpa XX individuals have ovotestes and make eggs in the ovarian part of their ovotests. They don’t make sperm, but they do have both sperm-related and egg-related ducts. The testicular part of these ovotestes secretes testosterone. XY individuals have testes only and make sperm.

References

• R. Jiménez, M. Burgos, A. Sánchez, A. Sinclair, F. Alarcón, J. Marin, E. Ortega, and R.D. de la Guardia, 1993, Fertile females of the mole Talpa occidentalis are phynotypic intersexes with ovotestes, Development 118:1303-11.

• Roughgarden p. 202

Discovery of Intersex honeybee complicates current model stating unfertilized bee eggs become haploid males, fertilized bee eggs become diploid females. (Gender Showcase, 9-12)

The total number of chromosome sets determines whether bees become male, female, or a mix. This haplodiploidy system means all male bees are haploid and all females are diploid (see above). Male bees have half the number of chromosomes that female bees do.

Distinguish this from XO sex determination, where only the number of sex chromosomes are halved, not the autosomes. For example, males and females both receive the same number of autosomal chromosomes, but males only get O for their sex chromosome (1 chromosome) and females get XX for their sex chromosome set (2 chromosomes).

Fertilized eggs are either homozygous at the Sex Determination Locus (SDL) and differentiate into diploid males or are heterozygous and develop into females. The diploid males, however, don't survive in a bee colony as they are eaten by worker bees shortly after hatching from the egg. Fertile males are produced by the queen's unfertilized, haploid eggs that are hemizygous at SDL. (Gempe et al. 2009)

Image credit: Ian Alexander

Gempe et al. (2009) tested areas in the Apis mellifera sequence and manipulated the complementary sex determiner gene (csd in excerpt below) and the feminizer gene (fem in excerpt below). They tried different ways of suppressing and adding the influence of these genes. They discovered that female bee development requires fem activity and csd activity processes the heterozygous (female) state and not the homozygous or hemizygous (male) states.

We show that heterozygous csd is only required to induce the female pathway, while the feminizer (fem) gene maintains this decision throughout development. By RNAi induced knockdown we show that the fem gene is essential for entire female development and that the csd gene exclusively processes the heterozygous state. Fem activity is also required to maintain the female determined pathway throughout development, which we show by mosaic structures in fem-repressed intersexuals. We use expression of Fem protein in males to demonstrate that the female maintenance mechanism is controlled by a positive feedback splicing loop in which Fem proteins mediate their own synthesis by directing female fem mRNA splicing. The csd gene is only necessary to induce this positive feedback loop in early embryogenesis by directing splicing of fem mRNAs. Finally, fem also controls the splicing of Am-doublesex transcripts encoding conserved male- and female-specific transcription factors involved in sexual differentiation.

This means that fatal mutations automatically kill their haploid males, and double-diploid bees automatically get cannibalized by nurse bees when they hatch! But recently, researchers discovered an unusual intersex honeybee, shown below.

View fullsize

Figure 1 (a-k). Individual of Euglossa melanotricha with male and female phenotypic characteristics. a Side view (right), b side view (left), c front view of the head, d scutellum with a scutellar tuft (as observed in the female of this species), e view of the abdomen showing the sting, f ventral view of the sting, g dorsal view, h metatibia (left) with the presence of slit, i metatibia (right) with corbicula, j mesotibia (left) with velvety area and basal and distal cushions, k mesotibia (right side).

Researchers discovered an orchid bee that had a blend of male and female body parts and genetics, though genetic analysis allowed them to conclude this bee is mostly feminine.

Suzuki et al. (2015) report:

Findings obtained through both morphological and genetic analyses of a gynander orchid bee (Euglossa melanotricha). For the genetic analysis, microsatellite markers were used to genotype the gynander bee. The morphological analysis revealed that the individual studied had a sting, and most parts of the insect body showed female phenotype, except for the three left legs. As in other reports on gynanders of orchid bees, the specimen of E. melanotricha analyzed herein was included in the category of mixed (or mosaic). From the seven microsatellite loci amplified, five were heterozygous for both male and female tissues, indicating that the organism analyzed is compatible with a diploid organism and not with a hemizygous or haploid one. Both the morphological and genetic characteristics of the gynander of E. melanotricha analyzed reveal that this specimen shows predominantly female characteristics.

Yet, Suzuki and colleagues suggest that this female-male labeling is not as clarifying as directly studying the mechanisms would be, and urge other researchers to look further into csd gene regulation:

In parallel, when considering the genetic uniformity of phenotypically different tissues (male and female) of this individual, the gynandromorph of E. melanotricha would be, in fact, an intersex bee.

In the current literature, there are over 100 reports of anomalous bees, showing both female and male phenotypes in the same individual, usually named gynander or gynadromorph (Wcislo et al. 2004; Michez et al. 2009). In light of the above scenario [of possible sampling bias discussed in omitted text], we suggest that future studies on gynander and intersex bees should give more emphasis to the understanding of the mechanisms involved in the csd gene regulation in an attempt to better elucidate how these anomalous organisms are generated.

Interested in haplodiploidy?

This sex determination system exists in all insects, Hymenoptera (bees, ants, wasps) and Thysanoptera (thrips), rotifers, Hemiptera (cicadas, aphids, leafhoppers), and Coeoptera (bark beetles).

References

• Gempe, T., Hasselmann, M., Schiøtt, M., Hause, G., Otte, M., & Beye, M. 2009. Sex Determination in Honeybees: Two Separate Mechanisms Induce and Maintain the Female Pathway. PLoS Biol. 2009 Oct; 7(10): e1000222.  doi: 10.1371/journal.pbio.1000222. PMID: 19841734.

• Hoff, M. 2009. Male or Female? For Honeybees, a Single Gene Makes All the Difference. PLoS Biol. 2009 Oct; 7(10): e1000186. doi: 10.1371/journal.pbio.1000186. PMID: 20076733.

• “The origin of the gynandromorphs has been attributed to genetic problems, and although different hypotheses have been raised to explain genetically the origin of the gynandromorphism in bees, the mechanisms that generate these abnormal individuals have not been elucidated.” Michez, D., Rasmont, P., Terzo, M., Vereecken, N.J. (2009) “A synthesis of gynandromorphy among wild bees (Hymenoptera: Apoidea), with an annotated description of several new cases.” Ann. Soc. Entomol. Fr. 45, 365–375

• Michez, D., Rasmont, P., Terzo, M., Vereecken, N.J. (2009) A synthesis of gynandromorphy among wild bees (Hymenoptera: Apoidea), with an annotated description of several new cases. Ann. Soc. Entomol. Fr. 45, 365–375

• Suzuki, K.M., Giangarelli, D.C., Ferreira, D.G. et al. (2015) “A scientific note on an anomalous diploid individual of Euglossa melanotricha (Apidae, Euglossini) with both female and male phenotypes”. Apidologie (2015) 46: 495. https://doi.org/10.1007/s13592-014-0339-5.

• Wcislo, W.T., Gonzalez, V.H., Arneson, L. (2004) A review of deviant phenotypes in bees in relation to brood parasitism, and a gynandromorph of Megalopta genalis (Hymenoptera: Halictidae). J. Nat. Hist. 38, 1443–1457.

For more about intersexuality in bees, see this comprehensive review papeR

• Narita, S., Pereira, R.A.S., Kjellberg, F., Kageyama, D. (2010) Gynandromorphs and intersexes: potential to understand the mechanism of sex determination in arthropods. Terr. Arthropod Rev. 3, 63–96.

Sex Determination – Why So Many Ways of Doing It?

This PLOS Biology article details the diverse mechanisms by which sex is determined in different species, how they evolved, and how they may look in the future. The article opens with a treatment of three common myths of sex determination.

Editor’s note: The term "hermaphrodite" is appropriate for referring to non-human animals with sex characteristics that do not fit typical binary notions of male or female bodies. For humans, “intersex” is the appropriate term—learn more here!

Although the entire reading is not for k-12 audiences, the three myths, Figure 3, Figure 4, and Box 2 are suitable for high school.

Journal: The Biological Contributions to Gender Identity and Gender Diversity: Bringing Data to the Table

This study is a review of evidence that gender identity is influenced by innate factors including genetics. The authors hypothesize that gender identity is a multifactorial complex trait with a heritable polygenic component, and that the study of this trait is important.

Although gender identity as a polygenic trait is only a hypothesis, this example could serve to show biology students how heritability studies can be used to gain a better understanding of a complex, socially relevant trait. Most textbooks cite skin color and height as examples of polygenic traits, and gender identity might be another to add to that list.

Family Acceptance of LGBT Youth Protects Against Suicide, Depression & Substance Abuse and Predicts Better Health & Self-Esteem (Journal of School Health)

Lesbian, gay, bisexual, and transgender-related school victimization is strongly linked to young adult mental health and risk for STDs and HIV; there is no strong association with substance use or abuse.

Elevated levels of depression and suicidal ideation among males can be explained by their high rates of LGBT school victimization.

Citation: Russell ST, Ryan C, Toomey RB, Diaz RM, Sanchez J. Lesbian, gay, bisexual, and transgender adolescent school victimization: implications for young adult health and adjustment. J Sch Health. 2011; 81: 223-230. (pdf)

Same-sex attraction & behavior are more common than LGB identity (Advance Data; Annals of Internal Medicine)

Source: http://www.lgbthealtheducation.org/wp-content/uploads/LGBT-Health-Care-for-Asian-Americans.pdf

References:

1. Mosher WD, et al. (2005) Sexual behavior and selected health measures: men and women 15-44 years of age, United States, 2002. Advance Data; 2005:362.

2. Pathela P, et al. (2006) Discordance between sexual behavior and self-reported sexual identity: a population-based survey of New York City men. Ann Intern Med. 2006;145(6):416-425.

Using Chosen Names Reduces Odds of Depression and Suicide in Transgender Youths (Journal of Adolescent Health)

““It’s practical to support young people in using the name that they choose It’s respectful and developmentally appropriate.””

— Stephen T. Russell (University of Texas at Austin)

After interviewing 129 youths in 3 US cities, the researchers found that having even one context in which a chosen name could be used was associated with a 29 percent decrease in suicidal thoughts.

The research was funded by a grant from the National Institute of Mental Health and supported by the UT Population Research Center and a grant from the Eunice Kennedy Shriver National Institute of Child Health and Human Development.

Citation: Stephen T. Russell, Amanda M. Pollitt, Gu Li, & Arnold H. Grossman. (2018) Chosen Name Use Is Linked to Reduced Depressive Symptoms, Suicidal Ideation, and Suicidal Behavior Among Transgender Youth. Journal of Adolescent Health, Volume 63, Issue 4, 503 - 505. DOI: https://doi.org/10.1016/j.jadohealth.2018.02.003

Transgender youths four times as likely to engage in substance use; linked to depression & bullying

Summary: Based on 621,189 California kids in a 3-year time period, researchers found that transgender youth were 2.5 to 4 times as likely to experience suicidal ideation compared to non-transgender youth. Based on the data, authors identify depression and school bullying as major explanations for this trend, and make further recommendations.

Citation: Amaya Perez-Brumer, Jack K. Day, Stephen T. Russell, Mark L. Hatzenbuehler. (2017) Prevalence and Correlates of Suicidal Ideation Among Transgender Youth in California: Findings From a Representative, Population-Based Sample of High School Students. Journal of the American Academy of Child & Adolescent Psychiatry. Volume 56, Issue 9, 2017, Pages 739-746, ISSN 0890-8567, https://doi.org/10.1016/j.jaac.2017.06.010 (http://www.sciencedirect.com/science/article/pii/S0890856717303167)

Victimization of Transgender Youths Linked to Suicidal Thoughts, Substance Abuse (Journal of Adolescent Health)

In two peer-reviewed papers, researchers at The University of Texas at Austin have found that transgender adolescents are twice as likely to have suicidal thoughts as the general population, and they are up to four times as likely to engage in substance use. Depression and school-based victimization factored heavily into the disparities in both cases.

Read more: https://cns.utexas.edu/news/victimization-of-transgender-youths-linked-to-suicidal-thoughts-substance-abuse

School Victimization of Gender-Nonconforming LGBT Youth Linked with Depression and Quality Of Life In Adulthood (Developmental Psychology)

From the American Psychological Association (which historically pathologized LGBT+ behavior), researchers found that bullying over LGBT status alone is completely responsible for how well that 13 to 19 year-old associates with gender as an adult.

We also found that school victimization due to LGBT status between the ages of 13 and 19 fully accounts for the associations between gender nonconformity and young adult adjustment, measured as depression and life satisfaction.

The researchers also analyzed their data to make sure other kinds of bullying weren’t responsible for depression and happiness.

However, school victimization for other reasons does not mediate this association.

This effect of bullying on the gender development of queer youth affects youth of all genders equally.

On the other hand, we did not find support for our hypothesis that the strength between gender nonconformity and school LGBT victimization would be stronger for boys. The process through which early gender nonconformity affects later psychosocial adjustment is similar for boys and girls.

Homophobic bullying in particular continues on into the young adult years and negatively impacts quality of life.

We found that the negative impact of specifically homophobic school victimization continues into the young adult years and affects quality of life and capacity to enjoy life.

The researchers do recommend that school policies specifically prohibiting queer-targeted bullying will reduce these negative outcomes.

Enactment of school policies that specifically prohibit victimization due to LGBT status, gender nonconformity, and other types of bias-related harassment can help reduce negative psychosocial outcomes in LGBT and gender-nonconforming young people. Thus, although it is clear that all victimization should be prohibited in schools, these findings specifically indicate the need for antibullying policies that enumerate categories often targeted by bullies.

The authors also seem thoughtful about how they are considering their transgender participants:

We also tested the model without transgender participants. The findings (available upon request) were similar to the results based on the full sample (i.e., the indirect pathway was significant and all pathways were of similar strength and the same direction). On the basis of these results, and because our measure of LGBT school victimization was inclusive of transgender experiences, we present finding based on the full sample.

Citation: Russell B. Toomey, Caitlyn Ryan, Rafael M. Diaz, Noel A. Card, & Stephen T. Russell. (2010) Gender-Nonconforming Lesbian, Gay, Bisexual, and Transgender Youth: School Victimization and Young Adult Psychosocial Adjustment. Developmental Psychology 2010, Vol. 46, No. 6, 1580-1589. (pdf)

pdf