The wild sex lives of marine creatures Luka Seamus Wright
A June full moon is glowing upon this reef
in the middle of the Pacific Ocean.
Beneath the surface, 17,000 camouflage
groupers dart about in the cloudy water.
What you’re witnessing is, in fact,
an underwater orgy—
turned feeding frenzy.
The water is hazy because groupers are
ejecting sperm and eggs in dense clouds.
This spawning behavior happens
during full and new moons,
when strong tidal currents carry
the fertilized eggs
away from corals and other
voracious predators on the reef.
An orgy might seem like a rather
flamboyant way to breed,
but sex in the sea is a surprisingly
inventive affair.
In fact, most of those voracious corals
use male and female sex organs
at the same time.
Corals also have mass spawning episodes,
but they release buoyant bundles
of eggs and sperm all at once.
This happens around half-moons,
when weaker tides calm
the water’s surface,
creating the perfect conditions
for their sex cells to couple up.
During these events, there can be hundreds
of coral eggs
and more than a billion sperm floating
in every liter of surface seawater,
where they create a sticky slick.
But corals are far from the only animals
in the sea that can express two sexes.
Nearby, a humphead wrasse is undergoing
a remarkable transformation.
These fish breed in groups where one male
fertilizes several females.
And, likely because there aren’t many
dominant males around,
the largest female is becoming one.
Unlike corals, humphead wrasse
can switch sexes,
but they only exhibit one sex at a time.
The wrasse changes colors,
loses her eyeline, and grows dramatically.
Soon, the metamorphosis is complete,
and he can fertilize the females’ eggs,
ensuring that procreation persists.
Interestingly, this bluestreak cleaner
wrasse
that’s grooming the humphead
was also once a female.
But unlike the humphead, he can change sex
again should he become single.
About 7,000 kilometers away,
in the shallows of eastern Australia,
this male mourning cuttlefish boasts
a much sneakier mating strategy.
A female cuttlefish has garnered
his attention,
but she’s also attracted another male.
Competing directly with this rival
would be a demanding ordeal,
so the cuttlefish opts for trickery
instead.
Positioning himself between the female
and his rival,
on one side, he displays
a mottled skin pattern
resembling that of a female
to appease the competitor.
On the other, he flashes a shimmering
courtship display at the female
and covertly passes her parcels of sperm.
This duplicitous strategy allows the male
to reproduce without putting up a fight.
These sexual escapades are just a sampling
of what goes on beneath the waves.
The striking diversity of sex in the sea
is partially enabled by water’s
unique physical properties.
Its stable temperature and high density
help preserve and disperse
reproductive cells.
Unless land organisms return
to the water to reproduce
or have specially adapted sex cells,
their options are limited.
For many terrestrial animals,
reproduction is usually only possible
internally,
with organs that resemble
the moist ocean environment.
This restriction may cause us to see
only one facet of sex,
but a brief tour of marine life shows
us just how diverse sex really is.
It does not always involve
strictly female and male individuals
with differently sized sex cells
that fuse internally.
Many algae, for example, have sex cells
that are indistinguishable in size.
Some animals are both male and female,
while others change sex.
A large proportion of organisms don’t need
to touch each other to reproduce.
And thousands of animals, from bluestreak
cleaner wrasse to Humboldt squid,
participate in same-sex sexual behavior.
So, peeking beneath the ocean’s covers
doesn’t just provide a spectacle.
It also gives us a more complete
appreciation of sex
in all its fascinating forms.