Jamie Kubiak, a chemistry teacher in New York City, hosts a crowdsourced database of teaching resources for a diverse range of content areas.
STEM Village Webinar
Join Sam Long for a 30-minute webinar on Gender-Inclusive Biology on Monday, April 6th. The time is 4 pm BST or 9 am Mountain time. Thank you to STEM Village for hosting. DM @TheStemVillage for the meeting password.
interACT Letter of Concern for Chromosome/Barr Body Staining Lab
Some schools do a lab exercise where students stain their own cells and determine their sex chromosomes (X and Y). This is a letter from the Executive Director of interACT that can be used to advocate for not doing this exercise due to the potential harm it can cause for intersex individuals.
Doctor's Rec: WPATH Standards of Care for “Transsexual, Transgender, and Gender Nonconforming People”
The overall goal of the SOC is to provide clinical guidance for health professionals to assist transsexual, transgender, and gender nonconforming people with safe and effective pathways to achieving lasting personal comfort with their gendered selves, in order to maximize their overall health, psychological well-being, and self-fulfillment. This assistance may include primary care, gynecologic and urologic care, reproductive options, voice and communication therapy, mental health services (e.g., assessment, counseling, psychotherapy), and hormonal and surgical treatments.
While this is primarily a document for health professionals, the SOC may also be used by individuals, their families, and social institutions to understand how they can assist with promoting optimal health for members of this diverse population.
Kaiser Permanente Transgender Care follows the WPATH standards of care and the 2009 Endocrine Society Guidelines, as well as a companion document for voice and communication change. Click through to access this file in 18 different languages.
Research documents school staff tend to blame victim of anti-LGBT harassment, incl. removing from school, when perpetrators face minor consequences. (Bochenek & Brown 2001)
Many people experiencing discrimination have encountered “victim-blaming” where the solution to the hate crime is to remove the identity being persecuted. Suppose a woman might have been told her attire “invited” sexual assault or even rape. Suppose a gay teen is told to stop “flaunting” their lifestyle choice, often by teachers and administrators in positions of trust and protection, when they report violence and daily harassment in the classroom. Suppose a recent immigrant is told that once they “learn English”, classmates will stop stealing his things and urinating on his book bag.
Only when teachers and administrators take risks to establish honest conversations that proactively support inclusion and affirm the expressive diversity of all people on campus (including students who feel the need to bully and abuse others) can we create genuinely safe spaces.
In addition to highlighting the inaction of teachers and other school staff, Daniel’s story illustrates the tendency among some school staff to ‘blame the victim’ in cases of anti-LGBT harassment, as other researchers have noted.
In Hatred in the Hallways, authors Michael Bochenek and A. Widney Brown cite situations in which LGBT students were removed from classrooms and even schools as a '“solution” to their having been harassed (while the perpetrators faced minor consequences), as well as one in which an assistant principal reportedly said of a student who had been harassed, “If he didn’t walk around telling people that he’s gay, there wouldn’t be any problems.”
Reference
Michael Bochenek and A. Widney Brown, Hatred in the Hallways: Violence and Discrimination against Lesbian, Gay, Bisexual, and Transgender Students in US Schools (New York: Human Rights Watch, 2001), 83.
Michael Sadowski, ed., Adolescents at School: Perspectives on Youth, Identity, and Education (Cambridge: Harvard Education Press, 2015), 125.
Diverse Reproductive Strategies Gallery Walk
In this lesson, students do a reading about R- and K-selection and then a gallery walk of four more unique reproductive strategies in animals. Students use the notes taken during the gallery walk to write a paragraph response comparing two different strategies.
The examples chosen include sequential hermaphroditism in clownfish and unisexual populations of all-female salamanders. However, they are limited in that all the example species are described to have binary sex. This lesson could be supplemented with examples of species where there are more than two sexes - see Scientific Evidence for examples.
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!
For a longer and more inquiry-based lesson, the gallery walk information could be shortened to remove the explanation for why each species has a unique reproductive strategy. Students could be tasked with hypothesizing the relationship between reproductive strategy and social structure or environment of the animal.
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)
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)
Honeybee eggs start out male by default!
Most of the time, unfertilized bee eggs develop into males and fertilized bee eggs develop into females.
In their haplodiploidy sex determination system, males have 1/2 the chromosomes that females do, so the males are haploid and females are diploid.
Double-diploid bees are automatically cannibalized by the nurse bees.
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)
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.
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.
Why does Homosexuality Evolve?
This video by Soliloquy outlines several hypotheses for why same-sex sexual behavior has persisted rather than becoming extinct in human and nonhuman species. Although not all of these hypotheses are supported by data, the video demonstrates how a behavior that appears deleterious to an individual can actually be neutral or beneficial when considering the complex social interactions within a population.
4 Ways Biology Can Make Your Teaching More Inclusive
When I switched to science teaching, I worried we weren’t preparing students for the diverse professional work environments I had left. Peers from different backgrounds often struggle to work together, and some curriculum can limit, not expand, the student conversation.
A student says…
“You need a mom and dad to make a baby.”
“Same-sex pairings or transgender behavior is unnatural because they don’t produce babies.”
“My textbook says a characteristic ‘goal’ of life is to mate and have biological children.”
“But I was taught that everyone is XX or XY. Is that wrong?”
What do we say?
Even in San Francisco, more experienced teachers asked me, a nonbinary immigrant biology teacher, whether science had any unbiased resources for talking to students in a gender-inclusive way. I’m passionate about creating a classroom where students can stay curious about new experiences and identities, but I still want to keep science at the center.
To get you started, I’m sharing four ways teachers at any level or subject can respond to common gender-related questions using the evidence-based model of actual scientific research. Click through to read the article on WeAreTeachers, which includes the infographic below. Feel free to print and/or share!
–RXS
Glossary resources, sports access, and new podcast appearances [Dec/Jan]
Hello, educators! Happy 2020! Here is our newsletter for December 2019/January 2020.
LGBTQ glossaries in non-English languages are a much-needed resource in many communities. Check out these resources with LGBTQ vocabulary in Spanish w/English translations, and text and audio in Burmese, Cantonese, Vietnamese, Mandarin, and Korean. If you have other resources in languages other than English that can support LGBTQ inclusion work, please email us so we can add them to our resource base!
Queering the animal kingdom: Kudos to River Suh for taking the beloved (but admittedly long and dense) book Evolution's Rainbow and producing useful tools that educators can use in the classroom! This spreadsheet details examples taken from the book of different non-normative sex, gonadal, and sexual selection-related behavior and streamlines them to be easily accessible.
Sports and athletics access for transgender students: Sports and athletics are often a fraught space for transgender and gender non-conforming students, but they don't have to be. Transathlete has gathered data on athletics policies in all 50 states and promotes this standard, gender-inclusive policy for use in schools across the country. The Transgender Law and Policy Institute has their own succinct set of recommendations for children's participation in athletics, while On the Team provides a more in-depth look at creating equal opportunity for transgender athletes.
Recent media related to gender-inclusive biology:
Upcoming conference appearances:
Time to Thrive Conference, Washington, DC, February 14-16
STAO Conference, Toronto, ON, March 26-27th
NSTA National Conference, Boston, MA, April 2-5th
Have a great start to your new year!
Lewis, Sam, and River
Temperature of egg determines gonads that form in turtles. (Gender Showcase, 9-12)
Discussion questions:
How do changing temperatures affect a sea turtle egg’s development?
How will average global temperature changes affect a sea turtle egg’s development?
References
M. Ewert, D. Jackson, and C. Nelson, 1994, Patterns of temperature-dependent sex determination in turtles, J. Exp. Zool. 270:3-15.
Roughgarden p. 203.
The temperature of the nest determines the gonads that form in crocodile eggs. (Gender Showcase, 9-12)
DISCUSSION QUESTIONS:
How do changing temperatures affect a crocodile egg’s development?
How will average global temperature changes affect a crocodile egg’s development?
Predict an increase, decrease, or stable population change if average temperatures increase or decrease.
Book excerpt: Among reptiles, specifically turtles, crocodiles, and some lizards, gonadal identity is determined by the temperature at which eggs develop, not by chromosomes. The eggs are usually laid in the ground and covered with sand or moist dirt from which they absorb water, swelling in size as they age. Reptile embryos start developing within their egg, and after a while primordial germ cells form. When reptile primordial germ cells move to the genital ridges of their parents, both the germ cells and the parental embryo presumably experience the same environmental temperature. Both germ cells and parent therefore receive the same message about which sex to develop as, and their agendas automatically agree.
Scientists reported the first case of intersexuality in an African dwarf crocodile (Osteolaemus tetrapspis), a 10 year-old male-presenting crocodile with gonads that were ovotestes.
We used to think crocodiles couldn’t be intersex, because we had never found any before. Our understand was that crocodiles needed two separate types of cells that never occur together.
This discovery shows we have so many more questions to ask about sex determination!
Image caption: A dwarf crocodile. (C) Jim Frazee
Because the model we use to explain sex determination in crocodiles cannot help explain this evidence, we must keep asking questions and build better models for looking at our evidence.
Langer: Half of the 22 extant species of crocodilians have been examined for occurrence of temperature dependent sex determination (TSD). In TSD reptiles, masculinizing temperatures yield 100% or a majority of males, whereas feminizing temperatures yield 100% or a majority of females. In the transition range of temperature (TRT), a mix of males, females and sometimes intersexes are obtained. However, the molecular mechanisms behind TSD and an explanation for the occurrence of intersexuality remain elusive.
References
C. Johnston, M. Barnett, and P. Sharpe, 1995, The molecular biology of temperature-dependent sex determination, Phil. Trans. R. Soc. Lond., ser. B, 350: 297-304.
J.W. Lang and H. Andrews, 1994, Temperature-dependent sex determination in crocodilians, J. Exp. Zool. 270-28-44.
S. Langer, K. Ternes, D. Widmer, & Frank Mutschmann. The first case of intersexuality in an African dwarf crocodile (Osteolaemus tetraspis). Zoo Biol. 33:459–462, 2014. DOI:10.1002/zoo.21149
C. Smith and J. Joss, 1993, Gonadal sex differentiation in Alligator mississippiensis, a species with temperature-dependent sex determination, Cell Tissue Res. 273:149-62.
Wibbles, Bull, and Crews, 1994, Temperature-dependent sex determination. Journal of Experimental Zoology 270(1):71 - 78. DOI: 10.1002/jez.1402700108
Spawning males of the bluegill sunfish have 3 body types/genders of distinct size and color. (Gender Showcase, 9-12)
One sunfish species, the bluegill sunfish (Lepomis macrochirus), has been studied in detail at Lake Opinicon, Ontario, Canada, and at Lake Cazenovia, in upstate New York.
Spawning males consist of three distinct size/color classes, and together with females, fall into four morphological categories, corresponding to four distinct genders:
I think the author, Roughgarden, is using gender to mean that there’s no sexually reproductive distinguishing function, and the difference is strictly morphological and behavioral. This also makes me wonder if the testes are lighter in the small male bluegill sunfish, given that they occupy most of the body cavity but still only comprise 5% of the total body weight of the fish. I am assuming she assigns male and female based on gamete production (egg/sperm) and/or primary regulatory hormone status (progesterone/estrogen/testosterone).
Image credit: ScienceSource
The yearly spawning episode lasts only one day. In preparation, large males aggressively stake out territories next to one another in aggregations of a hundred or more, called leks, along the bottom of the lake at a depth of 1 meter. Large males are called on to defend their space against neighbors about once every 3 minutes. Large males make nests for eggs in their territories by scooping out a depression in the mud with their tails. Females aggregate at the locales with many males and do not visit isolated or peripheral nests. Females prefer nests belonging to large aggregations because the presence of many males affords more protection from egg predators.
The large males are not Mr. Nice Guys. Their acts of aggression include biting, opercular spreading, lateral displays, tail beating, and chasing. Although primarily directed at intruding males, aggression sometimes is directed at a female in the territory—domestic violence, sunfish style. The male apparently tries to control the speed and timing at which a female lays eggs. Females simply leave if harassed too much in this way.
The females arrive in a school, and one by one they enter the territories of the large males. When a female arrives, a large male begins to swim in tight circles, with the female following. Every few seconds as the pair turns, the female rotates on her side, presses her genital pore against that of the large male, and releases eggs that the large male fertilizes. The egg release is visible as a horizontal dipping motion.
A female may spawn in many nests. A large male accumulates up to thirty thousand eggs from various females during the one-day spawning episode. A female lays about twelve eggs at a time with her dipping motion, so this total egg accumulation involves some female laying in the nest about once every 30 seconds. The scene is fast. Still, large males somehow find the time to enter the nests of neighbors, and about 9% of the fertilizations in a nest are by a neighboring large male.
The more numerous small males quickly fertilize eggs in nests that aren’t their own.
The females only choose nests based on how many fish are around it for protection.
Meanwhile, the small males are active. They stay at the borders between territories of large males and in the periphery, often close to rocks or in vegetation. Eggs remain viable in lake water for about an hour and sperm for only a minute. When the female releases eggs, the small males dart in quickly to release sperm over the eggs and carry out their own fertilizations. The large males try to repel the small males from their territories, but the small males are more numerous than the large males—about 7 to 1 in shallow-water colonies. Chasing all these small males, as well as neighboring large males and the occasional predator, takes a large male away from fertilizing eggs being laid in his territory. In these circumstances, the females spawn readily with small males while the large male is busy with all his chasing.
There are more small males in shallow-water colonies than deep ones because there is more vegetation for cover. It is important to hide because predators—large mouth bass, small-mouth bass, and pike—lurk in the lake. Thus the ratio of small to large males depends on the surrounding environmental context. All in all, the small males seem to be the gender counterpart of silent bullfrogs, silent singing fish, jack and parr salmon, and antlerless male deer.
Medium males: the romantic wingman.
Medium males court with large males, then join them in the nest to mate with a female bluegill sunfish. Both drive away other fish and both mate with the same female.
The medium males—the third male gender—are really surprising. No one knows where the medium males live most of the time, but they may school with the females. A medium male approaches the territory of a large male from above in the water and descends without aggression or hesitation into the large male’s territory. The two males then begin a courtship turning that continues for as long as ten minutes. In the end, the medium male joins the large male, sharing the territory that the large male originally made and defends.
Although the medium male sometimes joins the large male before a female has arrived, more often the medium male joins after a female is already present. The large male makes little if any attempt to drive away the medium male, in contrast to the way the large male drives away small males that dart into the territory.When a female and two males are present, the three of them jointly carry out the courtship turning and mating. Typically, the medium male, who is smaller than the female, is sandwiched between the large male and the female while the [courtship] turning [ritual] takes place. As the female releases eggs, both males fertilize them.
When two females mate with a large male, there is no courtship ritual like between the medium male and the large-male.
The females mate with the large male and then leave without a three-way interaction.
Occasionally, two females may be within a large male’s territory at the same time. Although the large male mates with both females, the three do not participate in any common ritual similar to the three-way interaction of the female with a large and medium male.
After the day’s excitement is over, each large male remains in his territory for 8 to 10 days to guard the eggs. The large male repels nest predators. During this period he never leaves the nest to forage and loses body weight.
% Spawning Groups
In all, 85% of spawning males are either small or medium, with the remaining 15% large males. Although in the minority, large males take part in most of the matings.
Among the large males, the reproductive skew is high and only some of the large males apparently survive the mutual aggression that is necessary to acquire a successful territory. The small and medium males obtain about 14% of the spawnings. Overall, 85% of the territories in which spawning occurs consist of 1 male within 1 female, 11% of 2 or more males and 1 female—usually a large male accompanied by a medium male—and 4% of 1 male and 2 females.
Developmentally, the small and medium males are one genotype, and the large males another. Individuals of the small male genotype transition from the small male gender into the medium male gender as they age, whereas individuals of the large male genotype are not reproductively active until they have attained the size and age fo the large male gender.
Third male as mating facilitator?
Instead of deceit theory or ungendered signaling, Roughgarden proposes a third interpretation:
Once the medium male is sandwiched between the large male and the female during their combined courtship turns, the medium male may protect the female from spawning harassment [from the aggressive large males] through his position between her and the large male.
Also, the medium male may have developed a relationship with the females while schooling with them, and thus able to vouch that the large male is safe.
I suggest that the feminine male is a “marriage broker” who helps initiate mating, and perhaps a “relationship counselor” who facilitates the mating process once the female has entered the larger male’s territory. This service is purchased by the large male from the small male with the currency of access to reproductive opportunity.
Sharing fertilization represents an incentive to stay, not theft...Nothing prevents animals from cooperating in bringing about a mating, as well as in caring for young after a mating...In view of the roles played by the three male genders, let’s agree to call the large male a ‘controller,’ the small male an ‘end-runner,’ and the medium male a ‘cooperator.’
References
For Lake Opinicon studies, see:
M.R. Gross, 1982, Sneakers, satellites and parentals: Polymorphic mating strategies in North American sunfishes, Z. Tierpsychol. 60:1-26.
M. R. Gross, 1991, Evolution of alternative reproductive strategies: Frequency-dependent sexual selection in male bluegill sunfish, Phil. Trans. R. Soc. Lond., ser. B, 332:59-66.
For Lake Cazenovia studies, see:
W.J. Dominey, 1980, Female mimicry in bluegill sunfish—a genetic polymorphism? Nature 284:546–48.
W.J. Dominey, 1981, Maintenance of female mimicry as a reproductive strategy in bluegill sunfish (Lepomis macrochirus), Environ. Biol. Fishes 6:59-64.
Gross, 1991, Evolution of alternative reproductive strategies.
Dominey, 1981, Maintenance of female mimicry as a reproductive strategy in bluegill sunfish.
Roughgarden, J. (2013) Evolution’s Rainbow: Diversity, Gender, and Sexuality in Nature and People. University of California Press, Berkeley. p. 78-81.
Sex Estimation Based On Multiple Pelvic Indicators More Accurate, Based On 49 19th c. Canadian adults — Bass Lab & Field Manual
The most accurate single indicator was sacrum shape (94.1%). On the other hand, three combinations of pelvic criteria produced higher levels of accuracy than the trait list as a whole: obturator foramen shape and presence of the ventral arc (98%); obturator foramen shape and presence of the ventral arc (98%); obturator foramen shape and true pelvis shape (98%); pubic shape and acetabulum shape and size (95%).
The William Bass Field Manual mentions other studies of European populations, but reproduces in full several tables by Rogers and Saunders based on 49 “adult skeletons from a 19th-century cemetery located on the grounds of the St Thomas Anglican Church in Belleville, Canada.”
Embedded below are tables for:
Table 3-24. Accuracy Levels for Each Individual Pelvic Trait (after Rogers & Saunders (1994:1051, Table 5) (Bass 2005: 216)
Table 3-25. Probability of Estimating Sex Correctly for Combinations of Two Traits (after Rogers & Saunders (1994:1051, Table 3) (Bass 2005: 216)
Curious about what the broad labels for male and female anatomical regions are for those anthropologists using the Bass Manual?
Source
Bass, William. 2005. Human Osteology: A Laboratory and Field Manual, 5th ed. Special Publication No. 2 of the Missouri Archaeological Society. Columbia, MO. http://coas.missouri.edu/mas
Bullfrogs (Rana catesbeiana) have two male genders that both mate with females. (Gender Showcase, 9-12)
Bullfrogs (Rana catesbeiana) have two male genders that both mate with females.
Bullfrogs have two male genders that both mate with females:
(1) large males who call at night, giving bullfrogs their name, and
(2) small males who are silent.
Both are reproductively competent, and females mate with both. Silent males turn into calling males as they grow older. Male frogs in older species and males in many vertebrate groups aslo have to decide when to begin breeding—whether to wait until established enough to flaunt wealth and power, or to begin sooner with fewer resources but lots of charm.
Silent males turn into calling males as they grow older.
Both still mate with females regardless of silence.
Perhaps silent males should not be considered a different gender from calling males, but rather an early developmental stage of the same gender. Compare this case with others, though, and you may agree that it makes more sense to view males who mature from a silent stage into a calling stage as changing genders.
R.D. Howard, 1978,. The evolution of mating strategies in bullfrogs, Rana catesbeiana, Evolution 32: 859-71.
R.D. Howard, 1981, Sexual dimorphism in bullfrogs, Ecology 62:303-10.
R.D. Howard, 1984, Alternative mating behaviors in young male bullfrogs, Amer. Zool. 24:397-406.
Roughgarden, J. (2013) Evolution’s Rainbow: Diversity, Gender, and Sexuality in Nature and People. University of California Press, Berkeley. p. 76.
Time to Thrive - Presentation Materials
We are so excited to give a presentation at Time to Thrive 2020 in Washington, D.C. You can access our slide deck, with linked resources, below.
Lab Out Loud: Strategies for Gender Inclusivity in Teaching Biology
The hosts of Lab Out Loud Podcast were very interested to hear from Sam and Lewis about our science-specific strategies for gender inclusion. Thanks, Brian and Dale, for having us on the show!
Without sharing food or grooming relationships among all genders, 80% of vampire bats would die from a missed meal instead of 25%. (Gender Showcase, 9-12)
The vampire bat (Demodus rotundus) is a small bat, no bigger than a plum, that “removes a small patch of flesh [from its prey] with its razor-sharp incisors and laps up the blood flowing from the wound. A vampire’s saliva has anticoagulant to keep the blood from clotting. After one bat has drunk its fell, another continues at the same spot.”
Hunting for food is hard and up to one-third of bats miss a meal on any given night.
Bats die after 60 hours without food, after freezing from dropping 25% of its weight.
Life as a vampire is hard. Bats are warm-blooded and, without feathers or fur, lose lots of heat. Their requirements for energy are huge. A vampire bat consumes 50 to 100 percent of its weight in each meal. Yet up to one-third of the bats may not obtain a meal on any given night.
Going without a meal is dangerous. A vampire dies after sixty hours without food because by then its weight has dropped 25 percent, and it can no longer maintain its critical body temperature. To survive, vampire bats have developed an elaborate buddy system for sharing meals. The sharing takes place between mother and pup, as well as between adults.
Photo credit: Alex Hyde/NPL (https://www.nature.com/articles/d41586-019-03005-5)
One study of vampires on a ranch in Costa Rica focused on a population divided into three groups of a dozen females. The members of a group often stay together for a long time, twelve years in some cases, and get to know one another very well. The group of a dozen adult bats is a family unit from a vampire’s standpoint.
Most of the group consists of females, each of whom usually cares for one pup. A female pup stays in the group as she matures, whereas a male pup leaves. The females in a group span several generations. Group membership is not entirely static, however. A new female joins the group every two years, so at any time the females in the group belong to several lineages, called matrilines.
The bats live in the hollows of trees. Imagine a hollow tree with an opening at its base and a long vertical chamber reaching up into the tree trunk. The females congregate at the top of the chamber. About three males hang out, so to speak, in the tree hollow.
One male assumes a position near the top of the chamber, nearest to the females, and defends this location against aggressive encounters from other males. This dominant male fathers about half of the group’s young. Subordinate males take up stations near the base of the tree by the entrance. Other males are out of luck, roosting alone or in small male-only groups rarely visited by females.
Photo credit (C) Gerry Carter
The food is transferred by one bat regurgitating into the mouth of another. Most (70 percent) of the food transfers are from a mother to her pup. This food-sharing supplements the mother’s lactation [milk production]. The other 30 percent involves adult females feeding young other than their own, adult females feeding other adult females, and on rare occasions, adult males feeding offspring.
Increased cooperation in bats includes same-sex grooming and food sharing.
Some adult females have a “special friendship” with females who are not their kin (males also have same-sex relations; see Roughgarden 141). This bond is brought about in part by social grooming. The bats expend 5 percent of each day grooming and licking one another. Some of this grooming is between special friends, and the remaining among kin. A hungry bat grooms one who has recently fed to invite a donation of food. To solicit food, a hungry bat licks a donor on her wing and then licks her lips. The donor may then offer food.
The mutual assistance is significant. If they didn’t help each other, the annual mortality of vampires would be about 80 percent, based on the chance of missing a meal two nights ina row. Instead, the annual mortality rate is around 25 percent because food-sharing tides bats through their bad nights.
References
G. Wilkonson, 1990, Food sharing in vampire bats, Scientific American (February), 76-82.
Roughgarden uses “cooperation” here in the wider sense to include both helping and not hurting. See R. Trivers, 1984, Social Evolution, Benjamin-Cummings.
Roughgarden, J. (2013) Evolution’s Rainbow: Diversity, Gender, and Sexuality in Nature and People. University of California Press, Berkeley. p. 61-2.
All male red-sided garter snakes wear female perfume and participate in same-sex copulation every year. (Gender Showcase, 9-12)
Species: Thamnophis sirtalis parietalis
All male garter snakes wear female perfume and participate in same-sex copulation every year.
In 1985 some male garter snakes were found with female perfumes in their skin. Of two hundred mating balls, about 15 percent consisted of a male, presumably with female perfumes in his skin, surrounded by courting males...In choice experiments [tests where they were given a choice between female and feminine male], the males preferred a female to a feminine male, showing that males could tell the difference—they were not deceived.
In 2000 it was found that all male garter snakes have female perfumes when they emerge from the den in the spring and that all males court these perfumed males in addition to females.
Four Flawed Deceit-Based Hypotheses:
Investigators floated four deceit-based theories to explain why all males have female perfumes on emergence: (1) a perfumed male may confuse the other males while carrying out its own mating; (2) the perfumed male may avoid wasting energy in courting before he has fully awakened from hibernation; (3) a perfumed male may induce the other males to waste time and energy courting him while he gets ready to start his own courting; and (4) a perfumed male may distract other males from females so he has more to himself when he does get going.
The simplest Occam’s Razor hypothesis:
The female perfumes might protect from attack or mounting when he is emerging, to lessen hostility and improve cooperation.
Photo credit: Flickr user @vabbley
Originally, scientists dismissed this explanation without even considering it, because they thought the theory required that organisms could only be habitually aggressive and antagonistic. Garter snakes tend to be friendly, especially with 20,000 in one giant group sex mating ball!
Citations
R. Mason and D. Crews, 1985, Female mimicry in garter snakes, Nature 316:59-60
R. Shine, D. O’Connor, and R. Mason, 2000, Female mimicry in garter snakes: Behavioural tactics of “she-males” and the males that court them, Can. J. Zool. 78-391-96. [Ed. note: Do not use “she-male” to describe transgender people. This is historically used as a harmful pejorative word to demean and exclude.]
R. Shine, P. Harlow, M. Lemaster, I. Moore, and R. Mason, 2000, The transvestite serpent: Why do garter snakes court (some) other males? Anim. Behav. 59:349-59. [Ed. note: This sensationalist title should not detract from the data recorded or this paper’s role documenting now-revised theories.]See also http://www.naturenorth.com/spring/creatre/garter/Fgarter.html
Roughgarden, J. (2013) Evolution’s Rainbow: Diversity, Gender, and Sexuality in Nature and People. University of California Press, Berkeley. p. 97-8.