What's Below the Surface?

Part-time mermaid Full-time marine biology nut

[whatsbelowthesurface]

Amphiprion ocellaris (Ocellaris clownfish) Pelong SE, Brunei, 4m

Here's a familiar face. A. ocellaris is better known as the ocellaris clownfish, and is the species that Nemo is modelled after!

Like other clownfish, A. ocellaris live in groups within a host anemone, using the anemone's stinging tentacles for protection. They're immune to the stings, thanks to a protective mucus coating on their skin.

Clownfish are utterly fascinating. They're protandrous hermaphrodites, which means they begin life as males, but can change to females later on in life. The largest clownfish in the group is the female, and the second largest is the dominant male. The rest of the clownfish in the group are essentially juveniles, and remain very much smaller than the breeding pair. If the female dies, the dominant male becomes the female, and one of the juvenile clownfish goes through a period of sustained growth to take his place as the dominant male!

Classification Animalia - Chordata - Actinopterygii - Perciformes - Pomacentridae - Amphiprion - A. ocellaris

[whatsbelowthesurface]

Elysia ornata (Ornate leaf slug) Pelong SE, Brunei, 4m

Not a nudi! E. ornata is closely related to nudibranchs, but actually belongs to a clade known as Sacoglossa, the ‘sap sucking’ sea slugs.

Sacoglossans are called sap suckers because they eat the cell contents of seaweed and algae. The cool part is that they can then incorporate the plant chloroplasts into their bodies and use them to photosynthesise! They use the products of photosynthesis to supplement their diets.

Classification Animalia - Mollusca - Gastropoda - Sacoglossa - Plakobranchidae - Elysia - E. ornata

[whatsbelowthesurface]

Bryaninops amplus (White-line sea whip goby) on sea whip Oil Rig Wreck E, Brunei, 15m

This is one of my favourite photos! I got lucky with this one; I was gently brushing a sea whip (gorgonian) aside when a dart of silver caught my eye.

These gobies are tiny; this little one can't have been more than 3cm long. B. amplus is closely associated with gorgonians, and this one was good at scooting around to the far side of its sea whip when I ventured too near!

Classification Animalia - Chordata - Actinopterygii - Perciformes - Gobiidae - Bryaninops - B. amplus

[whatsbelowthesurface]

Heteractis malu (White sand anemone) with a guest Pelong SE, Brunei, 4m

H. malu is also known as the white sand anemone or delicate sea anemone. It's not super common here, which is why I tried to get right up close for a macro shot. It didn't turn out so well but I did catch an anemone shrimp hiding amongst the tentacles! You can just see the red markings on its tail fan, and antennae (with blue bands) sticking out a little further to the right.

Classification Animalia - Cnidaria - Anthozoa (Hexacorallia) - Actiniaria - Stichodactylidae - Heteractis - H. malu

[best-of-memes]

[whatsbelowthesurface]

Frogfish coming through!

[sizvideos]

Video

[whatsbelowthesurface]

Inquisitive, yep, because this little one has quite an appetite! Small invertebrates like snails make up a solid chunk of a puffer’s diet.

[sizvideos]

Man adds dye to sea sponge - Video

[whatsbelowthesurface]

One of my favourite gif sets. Sponges pump water continuously, filtering food particles out of the water in the process.

[whatsbelowthesurface]

Neopetrolisthes maculatus (Spotted porcelain crab) Adik Reef, Tunku Abdul Rahman National Park, Kota Kinabalu, 15m

The spotted porcelain crab is also known as the anemone porcelain crab because it makes itself at home amongst the stinging tentacles of sea anemones (like its relative T. amboinensis, the sexy anemone shrimp). They are very small, about 3.5cm (less than 1.5in) across.

Porcelain crabs are quite delicate, as their name suggests, and will readily shed limbs to evade predators. The limbs grow back again over several moults (like all crustaceans, porcelain crabs moult as they grow, shedding their tight old exoskeletons to make room for the new exoskeleton waiting underneath).

N. maculatus has large claws (chelae) which it uses to fend off usurpers looking to move in on its turf. They're filter feeders, using long bristle-like structures (called setae) on their mouthparts to comb plankton and other tasty treats out of the water column.

Classification Animalia - Arthropoda - Malacostraca - Decapoda - Porcellanidae - Neopetrolisthes - N. maculatus

Image credit: Our fantastic dive guide Pablo from Divedownbelow

[whatsbelowthesurface]

Yep, this looks like a good place to stop! A visitor, South China Sea

This barn swallow (Hirundo rustica) took us all by surprise as it fluttered into our dive boat for a rest during our surface interval. This species migrates south for winter, arriving here after flying over the South China Sea by day.

We were quite a way out to sea, about a 30 minute boat ride from land. This swallow was completely exhausted and probably wouldn't have made it the rest of the way if it hadn't spotted our boat.

[whatsbelowthesurface]

Linckia laevigata (Blue Linckia, or blue star) Littledale Shoal, Brunei, 15m

L. laevigata are pretty common residents at many of the dive sites here. I love how they add a gorgeous splash of colour on the reef. These beautiful blue sea stars (starfish) can grow quite large, up to about 30cm (12in) in diameter.

L. laevigata is considered detritivorous, using its tube feet to scoot around the reef eating algae, detritus and other benthic goodies it comes across. Like other sea stars it can shed an arm to evade predators, regenerating the lost limb over time.

This species is extremely common in the aquarium trade, but it appears that most animals in the trade are wild-caught, not captive bred. L. laevigata are not well-suited to aquariums as they are extremely sensitive and water parameters need to be kept absolutely perfect. They can live up to 10 years in the wild, but suffer in captivity where their life spans are very much shorter. Please don't buy in to the wild-caught animal trade!

Classification Animalia - Echinodermata - Asteroidea - Valvatida - Ophidiasteridae - Linckia - L. laevigata

[whatsbelowthesurface]

Phyllidiella pustulosa Pelong NE, Brunei, 6m

My absolute favourite animals to spot underwater are nudibranchs (pronounced noo-dee-brahnks), or sea slugs! P. pustulosa are super common in this part of the world, and if I’m going to see a nudibranch on a dive, chances are it’s going to be one of these.

P. pustulosa lost out in the naming stakes, with its scientific name literally meaning pustulous, or pimply. Pretty easy to see why - members of this species are covered in tubercles (wart-like projections) that look like pimples.

This specimen’s head-end is on the right. You can see the two horn-like black tentacles (called rhinophores) sticking out the top of its head. Rhinophores are scent and taste receptors, and the nudibranch uses these to gather information about its surroundings.

When P. pustulosa feels threatened, it contracts its body into a ball-like shape and retracts its rhinophores.

Classification Animalia - Mollusca - Gastropoda - Phyllidiidae - Phyllidiella - P. pustulosa

[whatsbelowthesurface]

Low tide at Pelong SE

Finning back to the dive boat after another awesome dive.

[whatsbelowthesurface]

Octopus Pulau Mamutik, Tunku Abdul Rahman National Park, Kota Kinabalu, 15m

Octopuses are amazing. They’re incredibly intelligent and are known for their ability to squeeze through even the smallest of holes. An octopus is all muscle and tissue - the only hard part of its body is its beak, which it uses to tear apart its prey.

They’re also masters of camouflage. Octopuses have colour-changing skin cells called chromatophores that help them blend into their environment, making them super hard to spot! They can also use muscles in the skin to change their texture so they look even more like that rock or pile of coral rubble they’re trying to hide amongst.

This octopus was a brown/yellow colour as I approached.  As I came closer it obviously decided its chosen camouflage wasn’t working, and began to turn pale as it retreated into a gap between some rocks and coral. 5 seconds later, it was a mottled sandy colour and doing its very best grumpy rock impression.

Classification

Animalia - Mollusca - Cephalopoda - Octopoda

[whatsbelowthesurface]

Epinephelus merra (Honeycomb grouper) Littledale Shoal, Brunei, 12m

E. merra, or the honeycomb grouper, gets its common name from its beautiful brown and yellow patterning. I was actually surprised at how good-natured this particular grouper was, letting me get pretty close before taking off. 

Like other groupers, E. merra is carnivorous, feeding on smaller fish and crustaceans. It's one of the smaller fish in its genus, growing to about 32cm (13in) in length.

One of the most interesting things about groupers as a whole is that most species are able to change their sex. E. merra is no exception. Members of this species are born female, and as they age they shift sex to become male. Animals that share this characteristic are known as protogynous hermaphrodites.

Classification Animalia - Chordata - Actinopterygii - Perciformes - Serranidae - Epinephelus - E. merra

[whatsbelowthesurface]

Thor amboinensis (Sexy anemone shrimp), and a friend! Pulau Mamutik, Tunku Abdul Rahman National Park, Kota Kinabalu, 12m

Shrimp, like T. amboinensis, can be really hard to spot because they're so tiny! This species gets up to about 13mm (0.5in) in size. Once you know where to look though, they're hard to miss - check out those beautiful colours!

T. amboinensis gets its common name, the sexy anemone shrimp, from the way it sits with its tail curled up over its back, and when it walks its abdomen sways from side to side. (If you're not a fan of anthropomorphising animals, it's also known as the squat shrimp.)

T. amboinensis have commensal relationships with other invertebrates, usually sea anemones. A commensal relationship between two organisms is when one benefits without affecting the other - in this case, the shrimp lives deep within the anemone's stinging tentacles for protection, and the anemone is neither harmed nor helped by the shrimp's presence.

Course, a big old anemone is more than enough room for a tiny little T. amboinensis, so it's not surprising that this one's being photobombed by a second shrimp, at the top left! The second shrimp is a different species, Ancylomenes venustus, or the graceful anemone shrimp.

Classification Animalia - Arthropoda - Malacostraca - Decapoda - Hippolytidae - Thor - T. amboinensis

Credit: This gorgeous photo wasn't taken by me; our fantastic dive guide Pablo from Dive Downbelow snapped it on my camera.

[whatsbelowthesurface]

Blue skies behind, dark clouds ahead Storm front moving in, South China Sea

Usually on the dive boat we're far more interested in what's below the surface than what's above it. But not this time!

This spectacular cloud formation is called a shelf cloud. It's formed by fast-moving cool (sinking) air from a large storm front meeting with warm (rising) air from below and condensing it, creating these large, rolling wedges of cloud. Shelf clouds are often associated with heavy rain and strong winds - not ideal when you're half an hour from land!

We thought we might have time for a dive before this storm reached us, but we were wrong. It was moving so fast that the whitecaps started getting whipped up around us within 10 minutes of us arriving at our site! So we raced them back to shore.

[whatsbelowthesurface]

Polycarpa aurata (Ox heart ascidian) Two Fathom Rock, Brunei, 10m

This funny looking animal is an ascidian, or sea squirt. P. aurata gets its common name from its heart-like shape (that's the anatomical heart, not the love heart). They're also referred to as ink-spot sea squirts, for their blotchy appearance. 

Sea squirts are filter feeders, but they don't have specialised tentacles to help them capture their prey (unlike other filter feeders I've covered before). Instead, they suck in water and spit it back out again through their siphons - the two tube-like structures you can see on this one, on the right and in the middle. The buccal (or inhalant) siphon takes in water while the atrial (or exhalant) siphon expels it. Small particles of food in the water are trapped by a network of sticky mucus threads as the water passes through the sea squirt.

The movement of water through each animal is constant, and sea squirts like P. aurata can filter through hundreds of litres of water per day!

Classification Animalia - Chordata - Ascidiacea - Stolidobranchia - Styelidae - Polycarpa - P. aurata