Wednesday, January 2, 2013

Just-So Stories about Hermaphrodite Fish















A central issue that makes life hard for intersex people is invisibility.  Most people are unaware of how common intersex individuals are, something I’ve often discussed on this blog.  But there’s a larger setting in which the fact that sex is a spectrum gets erased, and that’s in descriptions of biology and the animal kingdom as a whole.  One way this happens is when biology textbooks fail to mention the fact that instances of intersexuality are found in all animals.  Another way it happens is through what we’re taught about those species in which hermaphroditism is the norm.  It’s the latter that I want to illustrate for you today, by examining about how we talk about a fish, the bluebanded goby. 

The bluebanded goby is a small and colorful fish, bright orange-red with iridescent blue stripes.  Bluebanded gobies are hermaphrodites, with the ability to produce either eggs or sperm.  Each bluebanded goby can switch from producing eggs to sperm or vice versa in the space of about two weeks; externally, there’s very little difference between an egg-laying or sperm-producing bluebanded goby.  They have a “sexual papilla” through which they can release egg or sperm, and it is a bit pointier when in sperm-producing mode and a bit wider in its opening when in egg-laying mode.   Most bluebanded gobies spend most of their lives in egg-laying mode.  They live in mating groups, and typically only one member of each group produces sperm, with the rest laying eggs, maximizing the number of offspring the mating group can produce.  It’s a neat arrangement.  It’s also not one that you’re likely to hear about if you are visiting an aquarium or keeping fish.

The intersex nature of the bluebanded goby is erased or distorted in most descriptions of the fish, because our society is so invested in the idea that sexual dyadism is natural and universal that we can’t see evidence to the contrary right in front of our eyes.  We don’t hear about it in our educations.  Say, for example, you’re a schoolchild going for an educational trip to an aquarium, and you see the pretty gobies there.  Here’s all you’d learn at the Cabrillo Aquarium in San Pedro, California about the sex of bluebanded gobies: “Recognized by an elongated robust body and two dorsal fins, males have longer dorsal spines and a suction-like disc that is formed by the connection of its pelvic fins.”  (See here.)  You’d hear yet another example of the “natural, universal fact” that all animals are male or female, not evidence of the sexual diversity of the natural world.  Not only does the hermaphroditism of the gobies go unmentioned, the “masculinity” of bluebanded gobies in sperm-producing mode is exaggerated—they are said to have “longer dorsal spines,” a phallic and aggressive description of a nonexistent difference.  In fact, scientists determining whether a bluebanded goby is in egglaying or sperm-productive mode do not look for any difference in dorsal spine length, only at the shape of the sexual papilla.  (Generally, a sperm-producing bluebanded goby will be on the large side for the species, and hence will have largish fins—but egglaying bluebanded gobies that are large have the same size dorsal spines, and the dorsal fins on a given fish do not change size when it moves between egglaying and sperm-producing modes.)

When popular educational sites do mention sex variance in the bluebanded goby, they don’t explain the fact that all bluebanded gobies are hermphrodites, capable of producing eggs or sperm.    They instead tell a story of rare and fascinating “sex changes” in fish that are otherwise binary in sex: “Males and females are similar in coloration, however, males have a longer dorsal fin than the females do. One interesting fact about blue-banded gobies is that if there is no male present, the dominant female in a group of blue-banded gobies has the ability to change her sex to that of a male.”  (See here.)  This description frames bluebanded gobies as sexually dyadic, existing as males and females, except for the occasional female who goes through a “sex change” in desperate times.  The fact that all of the bluebanded gobies are hermaphrodites, and that each time they move from group to group they have the ability to move from egglaying to sperm-producing mode or vice versa, goes unmentioned.  Rather than undermining the ideology of a natural sexual binary, the story of the rare “sex change” actually bolsters it.  “How bizarre and rare is this deviation, a one-time move between natural binary sexes!”

Not only do educational sites teach that bluebanded gobies are almost always “normal males and females” rather than always hermaphrodites, the way they present goby “sex changes” reflects ideas about human gender roles.  The BBC Science and Nature website states that bluebanded gobies “live in small groups with a single male and multiple females.  If the male leaves or dies, the largest female changes sex.”  (Link here.)  The story is one of a large, dominant male with his harem of smaller females, and a burly female fish changing sex to “rise” to male status and take over the harem.  This is how the story is told by most scientific articles about bluebanded gobies that’s I’ve seen.  Let me quote a passage from a 2005 article in the Biological Bulletin on “sex reversal” in bluebanded gobies, so we can examine this in more detail:

“Larger size often equates with increased success in aggressive encounters and therefore social dominance, providing a proximate mechanism for the size advantage hypothesis. In protogynous sex changers, the most reproductively significant resource that dominance affords is “maleness”; thus the reproductive payoff for dominance is extremely large, and females would be highly motivated to increase their aggressive behavior in times of social instability (i.e., in the absence of a dominant male).”  (See here.)

I’ll now restate that passage in clearer English and make overt its hidden assumptions: “Sex is binary but in some rare species ‘sex reversal’ can occur.  When it does occur, it is from female to male, because everyone knows it’s better to be male.  To be male is to be dominant and aggressive, which is good.  Usually in species where ‘sex reversal’ can occur, males keep the females in their place, but if there’s no male around, the females will all want to battle because the winner will get to be the male.”  This just-so story reaffirms all sorts of human gender stereotypes—and in so doing vastly distorts the objective reality of bluebanded goby life.

The first way the scientific fable distorts reality is by calling hermaphroditic gobies “males” and “females,” imposing binary sex language on fish that are born hermaphrodites and can shift back and forth between egglaying and sperm-producing modes multiple times in the course of their lives.  The term “sex reversal” also implies two opposite sexes rather than one sex continuum.  It would be much more reflective of objective reality to speak in terms of shifts in reproductive modes among hermaphrodites than about sex reversals between females and males.

The term “protogynous” used to describe gobies in the article means “starting out female,” which not only implies that the fish are not really intersex by nature, but also frames shifts in reproductive mode as only occurring in one direction: from “female” to “male.”  In fact, bluebanded gobies shift just as easily from sperm-producing to egg-laying modes when entering a group with multiple sperm-producing fish.  (See here.)  The idea that every bluebanded goby “wants to be the male” is a projection of human ideologies onto fish behavior.  The majority of bluebanded gobies at any given time are living in egglaying mode because this conveys a reproductive advantage for the group.  One could just as easily say that it’s obvious that most gobies “want to be female” since that’s what most of them do, but that one of them has to make the sacrifice and “be male” for the good of the group.  That would also be projecting emotions and motivations onto the fish, of course.  In fact, bluebanded gobies are just hermaphrodite fish reproducing in the most efficient way possible by operating in egglaying mode more often than sperm-producing mode.  But the story we read is one of enforced, devalued feminization and aspirational maleness, because that affirms sexist human gender ideologies.

Entwined with these male-privileging gender ideologies is a story about dominance and submission.  As the story goes, high status fish are dominant; low status fish are submissive.  The most aggressive and dominant bluebanded goby “gets to be the male,” while the rest have lower status that accords with their more timid female nature.  This narrative is so familiar in patriarchal society that scientists seem not to notice it’s an ideology they’re imposing on nature in their research and writing. 

Here is what we do know about bluebanded goby reproduction, stripped of human gender ideologies.  In this hermaphroditic species, the greatest number of offspring are produced when most of the fish are laying eggs.  So they form mating groups or families, typically of 3-7, in which one of the gobies’ bodies shifts to sperm-producing mode, and the rest shift to egg-laying mode.  The fish that takes on the inseminating mode needs to be robust, because it must continuously mate with the rest of the fish.  When mating groups form or change, the members all swim about actively, zipping toward one another.  (Actually, this behavior is quite common, and regularly occurs between all of the bluebanded gobies, including the egglaying ones in established groups.)  What determines which goby in a new group will take on the sperm-producing role is the behavior of the other fish.  A goby being zipped at by a zippier fish will dodge out of the way.  This gets called “submission” by scientists, but could just as well be termed “peacekeeping,” and would most accurately be simply called “getting out of the way.”  By engaging in this dance of zipping about, a new group of gobies determines which of the fish is the most energetic and robust.  Often it’s a large fish, but that’s not always the case.  That fish shifts to sperm-producing mode (unless it is already in that mode), and the others shift to egg-laying mode (unless that is already the case).

Oh, and by the way, bluebanded gobies that are in sperm-producing mode don’t “fight harder” to stay in that mode because they “don’t want to be female.”  If a group of bluebanded gobies is assembled completely out of fish that are in sperm-producing mode, all but one of them shift to egglaying mode.  This takes the same amount of time as it does for one sperm-producer to emerge from a group that is assembled out of gobies that are all in egglaying mode, and leads to the same rate of fertility.  (See here.) 

So: by nature, bluebanded gobies are intersex fish that form efficient mating groups of multiple egglayers and one inseminator, and shift reproductive modes as they move from group to group.  This is an interesting part of the wide diversity of sexual arrangements in nature.  I believe that teaching people about this natural diversity would make the world a better place for intersex people, as it would make it less likely for us to be perceived as “unnatural” and “disordered.”  But instead of teaching children about sexual diversity, educational sites either completely deny that bluebanded gobies are hermaphrodites, or only mention it as a story of rare and odd sex changes from dyadic female to dyadic male.  And scientists, educated like the rest of us in this context, impose all sorts of ideologies about binary gender roles onto what they observe about the fish, perpetuating the problem of distortion.

Nature is so much more interesting than the stories we tell ourselves about it.  It’s time to stop obscuring the objective fact of sexual diversity.

5 comments:

  1. Goes to show that even something as "objective" as observing fish in nature gets imbued with human biases on sexual dichotomy.

    This reminds me of the book "Evolution's Rainbow" which is currently on my nightstand :)

    ReplyDelete
  2. A lot of behavioural biology research is about figuring out the balance between group reproductive success and individual reproductive success. In a reproductive set up with one member of the group being in one reproductive mode ("male" or "female", or "sperm-producing" or "egg-producing" if you prefer), and all the other members of the group being in the other reproductive mode, the single male or female has a great individual reproductive advantage. All offspring produced by the group will have at least 50% of their genetic material from this one individual, so it's highly desirable from an individual reproductive success standpoint to either be this one individual, or to be closely genetically related to this one individual. For instance, consider New Zealand kakapo birds. Their reproductive set up is highly polygynous, meaning that they have one male reproducing with a large group of females. He will be the father of all the chicks in the group, whereas a female kakapo will be the mother of only a proportion of the group's chicks. The male in this arrangement has more offspring. It has been found that to improve their own reproductive success, kakapo mothers will feed their male chicks more, ensuring a higher survival rate for these chicks, and that they will have a lot of "grand chicks" with their genetic material. While the scientists may be projecting patriarchal ideas about dominance onto these fish, when they talk about reproductive advantage being connected to maleness in this species, this is what they mean. The gobies in sperm-producing mode will ultimately have more offspring than the gobies in egg-producing mode. I do agree that it is possible that the gobies are foregoing a position of high individual reproductive success in favour of choosing group reproductive success not out of 'dominance,' but out of suitability to that role.

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  4. The language of sex in behavioural biology is seriously, seriously in need of a rethink, and you have pointed me in the right direction here. Thank you so much!

    That said: Do you see the same patriarchal thinking in descriptions of protandrous organisms? It seems like they'd have to bend the logic even harder to make it accommodate things like clownfish.

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