As the
little sister of two mischievous brothers, I’ve been subject to my fair share
of practical jokes. So when many years ago, one of them suggested that we go
night snorkelling, I thought “Ha! I’m not falling for it this time, what a
ridiculous idea, we won’t see anything”. Then I was given an underwater torch
and proved completely wrong. The reef
never sleeps; the familiar faces of the day are swapped for weird and wonderful
creatures of the night. Jump in about half an hour before sunset and you’ll see
the changeover, the fish take on a new lease of life, rushing around like
maniacs, chasing each other and catching their dinner before bedtime.
Twilight
feeders have an advantage; their light-loving prey cannot see properly in the
fading sunshine, and their own nocturnal predators have not yet woken from
their slumber. There is a word for this - Crepuscular- it sounds like some sort
of disfiguring disease, but no, it’s used to describe an animal active mostly
at twilight. (Predictably it’s derived
from Latin, which was absolutely my worst subject at school. Latin is annoyingly
used extensively in Biology so my advice to mini Marine Biologists is to stay
awake during Latin classes - they’re not lying, it’s useful!)
Groupers are
often crepuscular feeders; if you stand on the jetty near our Park Hyatt
Maldives Hadahaa sign you will often see the big daddies terrorising schools of
innocent baitfish peacefully resting in the shallow waters. Sharks have excellent night vision too and are
particularly fun to encounter in the dark; like thieves in the night their eyes
glow with menace. They have a reflective layer behind the retina called the
“tapetum lucidum”, consisting of lots of tiny little plates covered in the
splendidly shiny substance “guanine”. This multitasking molecule is not only
found in sharks’ eyes, but it’s responsible for shiny things the world over,
from the sheen of the shiniest fish to cosmetics. Even more incredible, it’s a
vital component of DNA; does this mean that DNA is sparkly? Sadly I think not.
Nocturnal
fish are usually carnivores, particularly if they feed on zooplankton. After
dark, the bigger more delicious plankton rises from the deep, you can see it
twitching and wriggling around in the beam of the torch. Herbivores such as
parrot and surgeon fish are almost always diurnal, probably because finding
food is easy but they need to be able to see what is edible and what is not. At
night parrotfish really do bed down for the evening; they hide by wriggling
into cracks in the coral and thanks to their lack of eyelids they fall into
what looks like a “zombified” trance. Some
species of parrotfish sit inside a gooey bubble of mucus which is thought to
prevent their scent from traveling through the water and also wards off the
attack of blood sucking isopod parasites.
Ugly
squelchy things seem to prefer the cover of darkness too. Yesterday we saw the
Maldivian sponge snail, and last week we came across a pair of mating sea-hares
– giant slugs which can reach up to 30cm in length. Many armed monsters such as imperial urchins
and delicate feather stars emerge from hiding and little shrimps chirp away,
their eyes glistening from the crevices. Part of the fun of night diving or
snorkelling is that it allows you to focus your attention to only the small
patch of reef illuminated by your light; so invariably you notice the detail of
things. Bioluminescent plankton produce the
most magnificent magic trick of all; if you were to turn off your torch and
flap your arms around in the dark silky water, little flashes of light no
larger than pin pricks start appearing all around you - a truly beautiful
reminder of the wonder of nature and how much life and excitement there is to
find in the ocean.
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| Twilight diving on the Hadahaa house reef |
