The Coral Triangle

Commensal crustaceans of Kimbe Bay

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Secretive commensal crustaceans are the norm in Kimbe Bay, Papua New Guinea

crinoid squat lobsters live exclusively on crinoid feather stars

Crinoid squat lobsters…

One of the most impressive things about snorkeling in Kimbe Bay was the relatively easy access to some of the smaller commensal critters that often elude even the sharpest eyes. While nudibranchs, sea horses, and juvenile fishes are hard to spot, they are nothing compared to the masters of camouflage like crinoid (feather star) shrimp, soft coral crabs, squat lobsters, and gorgonian spider crabs. The common theme among these critters is that their chosen habitats revolve completely around the host organism and, as such, they have evolved a physical appearance that mimics the host’s appearance. It is the evolution towards a perfect form of camouflage. The obvious advantage is that they remain well hidden, and thus protected from potential predators.

feather star shrimp in Kimbe Bay, Papua New Guinea

Feather star shrimps…

Crinoid shrimp and squat lobsters live exclusively on crinoid feather stars, gorgonian spider crabs prefer to dwell on gorgonian sea fans, and soft coral crabs are found only on the colorful dendronephthya soft corals. Sea fans, crinoid feather stars and dendronphthya soft corals are all filter feeders, settling in areas where water movement brings them their preferred food item, plankton. The tiny commensals that live upon them scavenge food from debris that collects on the host or may even feed on the host itself, but do not appear to impact their host by doing so. It is thought that even though, for example, squat lobsters may feed upon their host, they also protect their host from potential predators by discouraging a predator by pinching at them with their claws.

The attention to detail among these commensal crustaceans is remarkable. Soft coral crabs that live on dendronphtheya soft corals not only take the physical appearance by appearing white with small reddish bumps on their carapace that resemble the red polyps of the soft coral, they even have whitish streaks on their shell that mimic the white spicules embedded in the tissue of their host soft coral.

soft coral crabs live on dendronphthya soft corals

Soft coral crabs…

soft coral crabs are masters of camouflage, even mimicking the spicules of the soft coral host

The attention…

While these critters are worth the time invested in looking for them, it is hard to realize the payout when 30 minutes into the endeavor, peering into yet another nest of feathery arms of a crinoid comes up empty once again. As we found out, it seems that gorgonian sea fans, crinoid feather stars and soft corals in Kimbe Bay, Papua New Guinea, have an over abundance of these amazing crustaceans. At times, finding one was just a matter of deciding to look for one. See a soft coral, there was probably a soft coral crab living upon it. There’s a gorgonian sea fan, and a gorgonian spider crab was sure to be hiding out on it. Few, if any, other places in the Coral Triangle can boast such a claim!

Gorgonian spider crabs mimic the color and pattern of gorgonian sea fans which allows them to remain well camouflaged

Gorgonian spider crabs…

The allure of these critters is easy to understand. And while we admire their strategy and success, it is also what makes them frustratingly hard to find…except in Kimbe Bay, Papua New Guinea.

Shallow reefs of Raja Ampat

Marine Habitats of Raja Ampat

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Wayag in Raja Ampat is an example of an archipelago of limestone islands

Azure blue…

Raja Ampat is well known among the scientific community, as well as the snorkeling and diving industry, for its spectacular marine biodiversity. Numerous factors play a role in why this region harbors such a vast array of species but one is quite obvious upon exploring the islands there. One of the most important reasons for such an incredible collection of fish and invertebrates is the diversity of marine habitats found among the islands, most, if not all, of them easily accessible as shallow snorkeling sites.

mangroves grow throughout the Bird's Head Seascape

Sunbeams through…

There are a number of different coral reef varieties that exist among the many islands of Raja Ampat, most of them fringing reefs that differ in their composition depending on how exposed they are to current and sunlight. Reefs surrounding calm bays vary in regards to both invertebrate and fish communities from the reefs exposed to swift, plankton-rich currents in narrow channels. But coral reefs are just part of the marine ecosystem here. Extensive stands of seagrass meadows and mangrove forests play vital ecological roles as nurseries, providing calm, protected habitats where scores of young organisms can grow to adulthood. There are also numerous species that utilize these calm habitats for their entire life histories, not just while they are young.

algae creates an almost surreal snorkeling experience in a marine lake of Raja Ampat

A snorkeler floats…

Perhaps the most distinctive of all the marine habitats in Raja Ampat are its marine lakes. These saltwater environments, set amid high limestone islands, are not easily accessible by either human, fish, or invertebrate. Due to their inaccessibility, each marine lake contains distinctive sets of life specifically adapted to the chemistry, depth, sunlight, and amount of food available. Each lake is like a large, unique Petri dish of life.

It’s hard to imagine any area on Earth harboring more species and habitats as Raja Ampat, which means this area is of great importance to the world’s overall marine biodiversity. Come explore the area for yourself as this region continues to offer some of the most spectacular snorkeling on the planet.

Red-spotted nembrotha (nembrotha sp.)

Nudibranchs of Raja Ampat

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Tambja morosa

Gloomy tambja

Snorkeling over a shallow reef in Raja Ampat our group was on the hunt. What started out as a few sightings of a group of attractive mollusks known as nudibranchs, became an obsession to find as many as we could. Fortunately we had two things going for us: First we were snorkeling in the coral triangle, a term that describes the region that possesses the world’s highest levels of marine biodiversity and second, we were snorkeling on one of the best reefs in all of Raja Ampat where nudibranchs are particularly plentiful.

Nudibranchs are colorful snails that lost their shell in favor of chemical defenses against potential predators. They are generally small (averaging 10cm in length) and disc shaped with external gills (nudi = naked, branch = gills) located either as a bouquet of feather-like

Nembrotha kubaryana

Green-lined Nembrotha

structures at the anterior portion of the body or as two longitudinal rows that grow from each side of the body. As part of their defense many of the over one thousand species have bright color patterns that act as warning to deter a predator from attacking the tiny snail.

It is the dazzling colors of nudibranchs that excites our group to seek them out amongst the kaleidoscope of soft corals, sponges, and tunicates. With many eyes on the search, we found no less than 20 species during our snorkeling session and were quite happy with our collection of photographs! Next time we vowed to beat that record and in a place like Raja Ampat, we have no doubt that we will.


Flabellina exoptata

Much-desired Flabellina

Pteraeolidia ianthina

Blue dragon

Roboastrea luteolineata

Yellow-lined nudibranch

Goniobranchus reticulatus

Red-netted nudibranch

Aegires gardeniri

Mating banana slugs

Chromodoris kuniei

Kuni’s chromodoris

Skeleton shrimp are carnivores that dwell on hydroids and black corals

Skeleton Shrimp

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Skeleton shrimp...

Skeleton shrimp…

Skeleton shrimp are an unusual family of amphipods (Capredllidae) found in all oceans but certainly common around coral reefs where they cling to gorgonians, hydroids, and bryozoans. These tiny beasts are barely discernable, reaching 1-2 cm long but only 1-2 mm wide! They feed on just about anything they can get their little claws upon – diatoms, crustacean larvae, protozoa, worms, and detritus. Skeleton shrimp can only mate while females are molting and between their old, hard exoskeleton and forming their new one. After mating females brood their fertilized eggs until the young are ready to hatch. This is one of the downers for males, after some species mate, females have been known to kill males by injecting venom from a claw… Knowing things like this allow human males to truly appreciate their place in evolutionary history.

A group of skeleton shrimp hanging out on black coral in Raja Ampat

Skeleton shrimp…

Juvenile fish converge on the diverse reefs of Raja Ampat

Juvenile fish abound in Raja Ampat!

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Juvenile fish in a mangroveDuring CTA’s recent exploration of Raja Ampat we came across numerous reef-associated habitats where seemingly billions of juvenile fish thronged. What species were represented among the youngsters was difficult to ascertain since many of the tiny fish were semi-translucent and had not fully metamorphosed into recognizable shapes and color patterns. How fish recruit to particular reefs and other marine habitats is intriguing and plays a large role in why some areas are incredibly diverse while others are deficient in fish diversity. Fish and coralMany factors play a role in this process but among the more important are fish’s larval life span, hearing, olfaction, swimming ability, oceanic currents, and luck. Whatever the case, it was astounding to drift among so many juveniles in Raja Ampat and to know that the reefs are likely to be well stocked in this area for years to come.

A marbled stargazer perches briefly on the sand before it buries itself

Ambush Predators of Komodo Is.

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Coral reef ambush predators

A tasseled scorpionfish rests on top of soft coral


Understandably, the title implies we are going to focus on the fearsome, awesome Komodo dragon! As one of earth’s largest terrestrial ambush predator, but relatively restricted to Komodo National Park, it would be a sound conclusion, right? The rich waters around the park, however, are home to a variety of cool ambush predators that possess some of the greatest talents of camouflage in the world.

Having your meals come to you is how we’d all like to live. There are a good number of fish found throughout the Coral Triangle that have evolved to live a sedentary but productive life by adapting an ambush-style of feeding. Instead of actively hunting their prey by chasing prey individual fish species have adapted a variety of methods to camouflage themselves on reef-associated habitats. Some utilize color and pattern to blend into their backgrounds while others employ texture and flaps of skin to break up their outlines. A few species merely bury themselves in sand with just their eyes, nostrils, and mouth barely exposed. Whatever method these ambush-species employ to hide, they are all extremely patient killers, lying perfectly still for hours or even days at a time, waiting and waiting for unwary prey to swim close and meet their demise.

Stonefish are so adept at camouflage, they are often completely invisible even in plain sight


crocodile flatheads can be well camouflaged and often hard to spot

Though they are…

A broadclub cuttlefish (Sepia latimanus) lays her eggs in fire coral

Cephalopods in Komodo

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A reef octopus (Octopus cyanea) in Komodo National Park

A reef octopus…

Horseshoe Bay, found along the southernmost edge of Pulau Rinja, is far and away one of the most distinctive snorkeling areas found in the Lesser Sundas. Known primarily for its handful of world-class dive sites, the ancient caldera is also home to shallow reefs that inhabit cold, upwelling waters and harbor different marine communities compared with other parts of Komodo National Park. Mollusks are one of the most prominent taxa found here and they range from the simplest of limpets to complex and intelligent cephalopods. For snorkelers, the cephalopods are what garner much of the attention. Cute Bobtail squid, timid reef squid,

Broadclub cuttlefish, well-camouflaged Reef octopus, and nocturnal Starry Night octopus can all be spotted in just a few feet of water within the bay. For snorkelers, who often get only brief glimpses of these creatures, Horseshoe Bay provides a set of underwater habitats that seem to relax these animals and allows exceptional encounters.

A broadclub cuttlefish (Sepia latimanus) swims above a reef at Satonda Island

A broadclub…

A starry night octopus (Callistoctopus luteus) found on a night snorkel at Torpedo Alley, Komodo National Park

A starry night…

Pink beach on Padar Island, Komodo National Park

The Pinkest Beach of them All

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There are more than a few pink beaches throughout the Indo-Pacific. The famous ‘Pink Beach’ is on Komodo Island in Komodo National Park. Though it may be famous, I would argue that it is not the pinkest.

Pipe organ coral (tubipora musica)

Pipe organ coral…

Pink beaches form where there is an abundance of the soft coral known as pipe organ coral (Tubipora musica) in the shallow waters that front the particular beach. Pipe organ coral is one of the few corals that form a hard, calcareous skeleton. The name, pipe organ, comes from the long, thin calcareous tube that houses an individual polyp. As the polyps divide, each new tube created by the new polyp, attaches to the existing tubes—via horizontal canals—and ultimately this is how the colony is developed. In many ways, this is not unlike how hard corals grow and produce their skeletons and colonies.

The area in which the skeleton of the pipe organ corals differs from hard corals is in the color. Hard corals create a white skeleton whereas pipe organ coral creates a bright red one. The red may be a function of how the iron oxides are incorporated into the skeleton as it is being created.

Tiny, red pieces of pipe organ skeleton mixed in the sand, Komodo National Park

Tiny grains of sand…

The skeleton of pipe organ coral (Tubipora musica)

Pipe organ skeleton…

The skeletons of pipe organ coral are very delicate and easily break, especially when the polyp dies. Heavy wave action can fragment the colony into tiny pieces and waves, tides, and currents end up depositing much of the material onto the nearby beach. As they further erode on the sane, the tiny pieces of red skeleton mix with the white calcium carbonate to create a pinkish hue to the sand.

Pipe organ coral tends to make up a large percentage of the soft coral diversity in many of the shallow coral gardens, especially those in front of beaches, in Komodo National Park. I started this blog with a mention about the famous Pink Beach on Komodo Island. It is probably the most often visited beach in the park, but as I also wrote, I do not believe it is the pinkest. That honor goes to the pink beaches of Padar Island (the smallest of the three main islands that make up Komodo National Park). All of the photos on this page were taken there and the beaches are often so pink, that the ebb and flow of water along the shoreline is often colored red rather than blue or green. We can’t wait to get back to visit these remarkable beaches again!

Want to see these amazing beaches for yourself? Join us on one of our Komodo snorkeling trips!

Lizardfish eating a goby in Komodo National Park


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It happens. It’s unfortunate, but it happens and it is necessary. Most reef fish, many predators themselves, become the prey. Fish that specialize on other fish are called piscivores. In the last two trips, I have been lucky enough to capture the capture, and consumption of this brutal but natural event. In the first case, a line-cheek wrasse (Oxycheilinus digramma) capturing what appears to be a toby. What alerted me to this event was the wrasse, with the toby in its mouth, banging the toby against a rock. This was probably in an attempt to render the toby limp so as no longer able to struggle. What I found interesting is that tobys possess Tetradodoxin, a fairly powerful toxin that is used to defend them against an attack. The idea being that once captured, it would release the toxin that would promote the predator to immediately release the toby. The release of the toxin would also ‘teach’ the predator that future attacks on this particular species would not be wise. In this situation, however, perhaps this was the first attack by the wrasse upon this species of toby. Perhaps this was the wrasse’s learning experience. Following the wrasse for as long as I could (about 30 seconds) it appeared not to have let it go during this period. I wonder if the wrasse has some type of immunity to the toxin that allows it to be one of the few predators of the toby…

Close-up of a line-cheek wrasse with a toby in its mouth

A closer look…


In the header photo, a lizardfish has captured a goby. Lizardfishes are ambush predators, often siting motionless on the bottom waiting for a small fish to swim nearby where it will suddenly lunge with a lightning speed to capture its prey. Lizardfish are mottled in appearance that allows it to camouflage on the bottom and may bury themselves in the sand to completely hide. This rare photo has been something I have been hoping to capture for many years and finally, the right place at the right time, though the goby may not feel the same way!

Hybrid butterflyfsh, Solomon Islands

Hybrids in the Solomon Islands

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We saw several examples of hybrids in our recent trip to the Solomon Islands (see our previous blogs, Lee’s is here and Ethan’s, here). Hybridization is generally the result of two species creating offspring that are genetically distinct from the parent species. This phenomenon is probably fairly common amongst corals, given that during spawning season there are several times when gametes from one species have the chance to interact with gametes from a genetically different, but similar species. This is much less observed in fishes, but of the few species that do hybridize, the results are very obvious.

The common families of fish that tend to produce the lion’s share of the recognized hybrids are the angelfishes and the butterflyfishes. It has been suggested that their social structure, primarily that of pair-bonding, probably favors this opportunity. For example, butterflyfishes are often similarly colored and tend to occupy closely paralleled niches. In the absence of another similar species (mate), two individuals may opt for each other as the best chance for reproduction. This may be the case between the spot-banded butterflyfish (Chaetodon punctatofasciatus) and the dot-dash butterflyfish (C. pelewensis). Both are similarly patterned (the main difference is only in the orientation of the bars; spot-banded have vertical bars and dot-dash have diagonal ones). In the header photo above, the pattern of this butterflyfish from the Solomon Islands does not match either parent, rather it appears to be a mix.

White-bonnet anemonefish staying close to its host anemone in the Solomon Islands

White-bonnet anemonefish…

This may be true for another locally common hybrid as well. The white bonnet anemonefish (Amphiprion leucokranos) is thought to be a result of a pairing between the orangefin anemonefish (A. chrysopterus) and the orange anemonefish (A. sandaracinos). Once again the nature of the strong pair-bonding between male and female comes into play and is further reinforced by the need for each individual to reside with an anemone. The initial relationship was probably a bit rocky as each species sought to ‘control’ the social structure of the anemone. In the absence of another mate, however, the two species opted for reproduction with each other, the result being the white bonnet anemonefish.