The sex lives of aquatic animals

Today I’m going to be looking at water and sex as it pertains to non-human creatures but later this month I’ll be looking at how water interacts with men and women.

Gendered language

Before we even dip our toes into this topic, we must acknowledge that how we talk about water is not gender neutral.  We find some rivers that are considered female, and some that are male.  There are no rules in the English language to stipulate this, although there often is in other languages. But how we talk about our bodies of water does matter, the language we use has a ‘profound influence on how we see the world’.

Fish

Fish are way ahead of us when it comes to thinking about sex and gender.  Whereas the majority of humans seem set that there can only be two genders and they cannot be changed, fish are rather flexible in their attitude.  They can undergo one or more sex change in their life and they can even have both sexual organs at once.  Sex changes tend to occur if a population becomes too biased to one sex or to improve genetic fitness.  One example of this is the clown fish which generally forms a monogamous relationship.  If the female dies, as in Finding Nemo, instead of hanging around feeling sorry for himself, the male will change into a female.  They will then pair up with a single male.  But that would have made for a more controversial film…

Other examples of sex changing fish include the Kobudai, made famous in Blue Planet II, which slowly but surely morphed into a male.  For the blue headed wrasse, it is the loss of the dominant male which triggers a sex change, usually in the largest female of the group.  This involves dramatic changes in behaviour, anatomy and colouration.  What I really like about this fish is that whilst most juveniles are female, there are a few sneaky males which look like females and then go ahead and mate without the dominant male noticing!

Interestingly, the population size of a fish and the direction they change sex seem to be linked.  There are more than 400 species of sex changing fish, some change from male to female and some from female to male (as well as those which can also change back).  Species who change from female to male have smaller population sizes than those which change from male to female.

As well as aquatic life which can change sex, we also have those creatures which forgo the need to change and make life easy and interesting by having both sets of genitals.  For example, there is a type of sea slug which has both penis and vagina. After it’s had simultaneously fertilising sex (basically some sort of epic 69 position) the penis falls off.  And then, as if that wasn’t enough drama, it grows another one!

Pollution

No one wants to have sex in polluted water… but for the fish and other aquatic creatures that have to, the consequences can be dire.

For this topic, we need to understand what endocrine disruptors are and where they come from:

What? Endocrine disruptors are chemicals that can interfere with endocrine (or hormone) systems.

Where? Endocrine disruptors can be found in plastics, cosmetics, medications, pesticides and even in food as a contaminant.  More than 800 man-made chemicals have been found to interfere with hormones.

We started to get a sense of the impact endocrine disruptors were having back in 1985 when a study on male alligators in a lake affected by chemical pollutants were found to have testosterone levels three times lower than those of males in a similar but uncontaminated lake.  The levels were so low they were close to those of females and females in turn had twice the amount of oestrogen.  Further, the males had poorly developed testes and smaller phalli and females also exhibited abnormal sexual organs. This was over 30 years ago.

“Chemicals are disturbing normal hormone-controlled development, affecting gender, sex, and reproduction.  And we are now seeing, low doses are disruption enough.  Fish appear particularly at risk of hormone disruption.”
– Janisse Ray, 2007

In areas where they are exposed to endocrine disruptors, fish have been found with lower levels of hormones, found to take take longer to mature, develop smaller sexual organs and produce fewer eggs, some of which don’t grow.  An example from Florida is that of the mosquitofish where effected females developed a male sex organ and attempted to mate with female fish.  Fish have also been found in the UK with both genitalia (unnaturally) occurring.  More often than not, these were found downstream of sewage treatment works and other industry.  But more recent studies show that the medications we consume are entering the water cycle in amounts which, whilst not of concern to human health, are altering the health and behaviour of animals in our rivers.

The impact of the endocrine disruptors is greater as the chemicals accumulate in animals up the food chain, for example gulls have been affected and a beluga whale has been found with two ovaries, two testes, male genitalia and partial female genitalia.  Female black bears have also been found exhibiting some degree of male sex organs.  A report (I lost the link) from 2003 stated that over 200 animal species were known, or suspected, to have reproductive disorders which might be attributed to these chemicals.

The impact on hormones on population sizes is exacerbated by the effects of climate change.  Changing temperatures affects the sex of species such as baby turtles and crocodiles and could lead to exclusively female clutches which in turn could be the end of the species altogether, especially if males are affected by endocrine disruptors and are unable to fertilise females.

Not that it should be the only reason we act, but these chemicals can also affect humans.  Human exposure can come from ingesting food, dust and water which is contaminated but also through inhalation and through the skin.  They can be transferred from pregnant woman to fetus and from parent to child through breast milk.

Further reading:

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