Photo by Rantje Allen
Photo by William Tan
Photo by Rantje Allen
Photo by William Tan
Photo by Rantje Allen

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Tag Archives: dive gorontalo

Thysanozoon nigropapillosum Swims & Dazzles

Posted on April 10, 2025 by Miguel's Diving • 0 Comments

Thysanozoon nigropapillosum is a dazzling flatworm. Yellow- or gold-tipped papillae cover its black body. Its body margin has bold white edges.

Many Confusing Names

Thysanozoon nigropapillosum lacks a standard English name. Some call it the Yellowspotted, Yellow-spotted, Yellow Spot, or Yellow-speckled Flatworm. Others refer to the spots as gold. Some online sources call it the Galaxy Flatworm since its body looks like a maze of stars.

Appearances of Thysanozoon nigropapillosum in Gorontalo

Before opening diving in Gorontalo, Miguel’s Diving surveyed potential dive spots. In May 2000, we recorded our first sighting of Thysanozoon nigropapillosum off the coast of Bone Pantai Regency. Since then, we have rarely encountered this beautiful flatworm—perhaps only once every five years!

In 2025, one of our guests captured Thysanozoon nigropapillosum on video, creating an intriguing clip. Flatworms can swim short distances by waving their flat bodies. The video shot by Rainer de Reuter captures this undulating motion perfectly!

Notice the two white-tipped protrusions at the front of the flatworm. These are pseudotentacles. They sense light and motion, helping the flatworm navigate.

Favorite Food

Thysanozoon nigropapillosum feeds on certain species of tunicates. One of its favorites is Didemnum molle, which is very common in Gorontalo. The flatworm engulfs the tunicate’s thin body with its mouth. However, it does not digest the hard calcium spicules that give the tunicate structure. Instead, these are expelled as pellets.

Savage Mating

All flatworms are hermaphrodites, meaning they have both male and female reproductive organs. Thysanozoon nigropapillosum also has two penises. During mating, each flatworm attempts to inseminate the other. First, special structures called rhabdites grip the partner’s edge, providing a strong hold even while swimming. Then, the two try to stab each other with a penis—or both! The maze of yellow papillae makes aiming difficult, and missed attempts often result in dermal impregnation.

Where to Find this Dazzling Flatworm

Found throughout Indo-Pacific waters, this dazzling flatworm can grow up to 8 centimeters long. Divers can spot it at depths ranging from one to twenty meters.

For your chance to see unusual marine life in Gorontalo, please make your dive reservations directly with Miguel’s Diving.

Risso’s Dolphins Sunbathe and Play

Posted on March 11, 2025 by Miguel's Diving • 0 Comments

Risso’s Dolphins thrive in the deep waters off Gorontalo’s southern shores. One day, we spotted a large, active pod. Using a drone, we watched as they sunbathed, played, and possibly mated.

Ghostly Apparitions

Risso’s Dolphins (Grampus griseus) are a distinctive species of dolphin. They are born gray but become whiter with age. The older one is, the whiter it appears. When passing under the dive boat or swimming nearby, they look like ghostly apparitions.

Their bodies also show visible scarring. Most scars come from fights with other Risso’s Dolphins, while other scars come from bites of deep-sea squid, their main diet. These features make them easy to identify.

Unlike other dolphins, Risso’s have rounded heads and no beak. They also have a crease running from the blowhole down to the upper lip. This unique feature is only visible up close or from a drone’s view.

Drone Video of Risso’s Dolphins

One day, our dive boat was heading to the second dive site when our captain spotted a pod of Risso’s Dolphins. They were sunbathing on the ocean’s surface, which is typical behavior in Gorontalo. Their distinctive white bodies confirmed their identity.

As we watched from a safe distance, one of our Indonesian guests launched his drone. Dr. Reyhan Aditya captured dramatic footage of this large pod. Some dolphins rested on the surface, while others played. One sequence even suggests mating behavior.

Risso’s Dolphins typically grow to three to four meters long and weigh between 300 and 500 kilograms. Clearly, most dolphins in this pod were adults. At other times, we have seen baby Risso’s among them. Usually, we see pods of about ten individuals, but this pod was much larger.

Worldwide Sightings

Risso’s Dolphins live in temperate and tropical oceans worldwide. They prefer deep offshore waters. Sometimes, they swim closer to land or oceanic islands when the continental shelf is narrow. This is true of Gorontalo’s southern coastline. Here, the continental wall of Sulawesi lies just a few meters from shore, plunging to four kilometers deep. This unique geography makes Gorontalo a great place for pelagic encounters.

Antoine Risso, a French naturalist, first described this species in 1812. Later, the dolphin was named in his honor.

For your chance to see unusual marine life in Gorontalo, please make your dive reservations directly with Miguel’s Diving.

Striped Barracuda Warily Eye Divers

Posted on December 5, 2024 by Miguel's Diving • 0 Comments

Striped Barracuda schools on Gorontalo’s shallow reef flats. Smaller and more cautious than its larger relatives, this species dazzles with its streamlined body.

How to Identify Striped Barracuda

In contrast to other barracuda species, the Striped Barracuda is smaller, reaching about 55 cm in length. Also, its body features two thin, dark horizontal stripes running along its silvery body. These stripes are its defining feature and help divers distinguish it from barracudas that look similar.

Sometimes, it is called the Obtuse Barracuda, which translates its Latin name of Sphyraena obtusata.

Other Barracudas found in Gorontalo

Occasionally, divers in Gorontalo will see a Great Barracuda (Sphyraena barracuda). As the largest barracuda species, it can grow over a meter in length. Often, it swims alone. Its imposing size and solitary nature make it easy to differentiate from the smaller, schooling Striped Barracuda.

Also found in Gorontalo is the Yellowtail Barracuda (Sphyraena flavicauda). As its name suggests, its yellowish tail is the most prominent feature. Its body has faint spots instead of the distinct stripes seen on the Striped Barracuda.

The Black Barracuda (Sphyraena qenie) is slightly larger than the Striped Barracuda and is known for its dark fins and body markings. While the Striped Barracuda has clean, horizontal stripes, the Black Barracuda’s markings can appear as a combination of dark smudges and irregular lines, giving it a more shadowy appearance. These features, along with its tendency to inhabit deeper waters, help divers tell the two species apart.

Habitat and Behavior

striped barracuda school — *Sphyraena obtusata* school in Gorontalo

This barracuda species is found in warm, shallow waters throughout the Indo-Pacific region. They prefer areas with coral reefs, mangroves, and seagrass beds, where food is abundant.

During the day, they form schools for protection, creating a shimmering spectacle as light reflects off their bodies. At night, they disperse to hunt small prey like fish and crustaceans.

Tips for your Encounter with Barracuda

The schooling behavior of the Striped Barracuda is a visual treat for divers. Seeing these sleek fish glide in unison over Gorontalo’s colorful reefs is unforgettable.

barracuda wary of divers — Barracudas are wary of divers

However, their cautious nature makes observing them tricky. We suggest divers move slowly, so as not to startle them. Also, try to approach from different angles. The barracuda school will maintain distance from divers if it feels threatened.

An encounter with a school of Striped Barracuda offers divers an opportunity to appreciate the beauty and diversity of the underwater world. So, plan your dive with Miguel’s Diving to explore Gorontalo’s vibrant marine life up close.

Phyllidia elegans decorates reefs

Posted on November 14, 2024 by Miguel's Diving • 0 Comments

Phyllidia elegans is a dorid nudibranch found occasionally on Gorontalo’s coral reefs. Oftentimes, divers see it among rubble. We call it the Elegant wart slug.

The Showy Peaks of Phyllidia elegans

This elegant wart slug has distinctive whitish to pinkish protrusions. These are called tubercles. They look like snowy mountain peaks. A few tops of those tubercles are yellow. This is a distinguishing characteristic of Phyllidia elegans.

Irregular black lines look like rivers running in the valleys between peaks. Some blackish spots can appear along the slug’s edges. Also, for this elegant wart slug, yellow rhinophores are distinctive.

Although divers rarely look at the underside of the slug’s foot, Phyllidia elegans has a median longitudinal black line on its sole. Uniquely, this slug also has black lines on the sides of its foot.

Rare photographs of the Elegant wart slug

The archived website of Sea Slug Forum has several unique photographs of Phyllidia elegans. One shows the gills, which are underneath this critter, between its foot and mantle. Another photo shows the Elegant wart slug laying eggs. The moderator notes this may be the first photo of the egg mass. Moreover, one of the photos is from Gorontalo, taken and submitted by one of our diving guests.

Unknown Life Cycle

Scientists know little about the life cycle of Phyllidia elegans. It is a simultaneous hermaphrodite. That means a single individual is both male and female at the same time. When two of these wart slugs come together for mating, each with stab its penis at the other. The first one to penetrate the other’s skin will be the male for that coupling.

Most phyllidiid nudibranchs, like the Elegant wart slug, feed on sponges of the Phakellia genus. These are usually red-orange in color.

Phyllidia elegans lives in the Western Pacific and Indian oceans, as well as in the Red Sea. Its maximum length is about five centimeters. Divers are more likely to spot it in shallow waters where hard coral growth is poor. For your chance to see this elegant marine critter in Gorontalo, please make your dive reservations directly with Miguel’s Diving.

Razorfish keep their noses down

Posted on September 20, 2024 by Miguel's Diving • 0 Comments

Razorfish and shrimpfish swim in synchronized groups. Typically, they keep their noses down. They are a graceful sight for divers to enjoy.

Distinctive behavior & appearance

These fishes look like flattened razors. Their bodies are light in color with a dark body line. This line reaches from their long noses all the way to the back. Also, the line passes over the eye.

Most distinctive is their swimming pattern. Divers can see them in occasional pairs. Most often, however, they will gather in large schools, forming a shimmering curtain. Usually, they keep a cautious distance from scuba divers. When they decide to move, all the fish in a school will point their noses in the same direction and swim quickly away. Then, they will settle back to their head-down position.

Found through the Indo-Pacific and Indian oceans, they typically live at depth between two and fifteen meters. They tend to prefer areas with some potential for silting. They eat mysid shrimps.

The Razorfish common in Gorontalo

Centriscidae is a small family of fishes that tend to swim with their heads pointed downwards. They all look practically the same. There are two genera: Aeoliscus and Centriscus.

Centriscus scutatus is the species common in Gorontalo. Its common name is Grooved razorfish. This is because the fish has an interorbital groove. That is a narrow depression that runs between its eyes and along the skull. Only scientists in a laboratory can observe this.

Most helpful is for divers to observe the fish’s tail. Actually, what looks like the tip of the tail is the fish’s first dorsal spine. It lies flat along the top of the body and projects beyond the actual tip of its tail. To divers, the fish appears to have a long, thin, and rigid tail.

Confusing similarities

The fish most likely to be confused with the Grooved razorfish is Aeoliscus strigatus. Divers usually call this the Coral shrimpfish. Other common names include Jointed razorfish, Striped shrimp fish, and variations of those words. Careful observers look for the only visible distinctive of this species. This fish has a hinge on the end of its dorsal spine, which swings to the side as the fish moves. It functions like a rudder.

The largest of the shrimpfishes is Centriscus cristatus. It lacks the hinge and its stripe is yellowish with several perpendicular dashes above the stripe. We have not observed this fish in Gorontalo.

The fourth shrimpfish is Aeoliscus puntulatus. In addition to the hinged tail, it sports fine black spots above and around the mid-lateral stripe. We have not observed this species in Gorontalo.

The popular generic name shrimpfish comes from all the bony plates that compose the bodies of these razor-shaped fishes.

For your chance to see these beautiful fish in Gorontalo, make your dive reservations directly with Miguel’s Diving.

Funnelweed pass unnoticed

Posted on May 1, 2024 by Miguel's Diving • 0 Comments

Funnelweed, though found worldwide, lives in limited locations in Gorontalo. Divers certainly pass by without noticing. But scientists are researching it.

Delicate scalloped algae

Although funnelweed is a member of the brown algae family, its color here in Gorontalo is not brown. It grows in some sandy patches or substrate among other algae. Its color is pale cream. Sometimes, it has tinges of light green.

It grows in beautiful, radiating ribbons. Opaque bands alternate with more transparent ones. Often, this algae forms scallops that curve inwards. On the outer edges and surface sprout almost transparent filaments.

Divers, who take the time to notice funnelweed, quickly appreciate its unique beauty. However, they should not brush against it with unprotected skin. Something about these algae here leaves itchy stings.

Funnelweed around the World

In Gorontalo, this beautiful plant only grows in a few small areas. A few sandy patches are full of these algae. In a couple of other sites, it grows among other algae.

However, it is found worldwide. This includes the Caribbean and Atlantic oceans, as well as the Indian and Pacific ones. The detailed list of locations is quite long. The scientific name for funnelweed is Padina gymnospora. Since it lives in so many oceans, scientist the world over are researching its potential value.

Scientific Research on Padina gymnospora

One group has extracted sulfated polysaccharides from it. Their research indicates anti-inflammatory properties. They used mice in their studies prior to potential use on humans.

Other researchers discovered anti-amyloidogenic agents in funnelweed. This extract in an important component in drugs that combat Alzheimer’s disease.

Field research on Padina gymnospora has found significant absorbent properties in the algae. A synthesized compound from it is over 80% effective in absorbing industrial dyes. Removing these dyes from industrial waste is a priority to build a cleaner world. Using this extract is clean and green solution in reusing industrial wastewater.

Padina gymnospora produces an aragonite calcium carbonate compound as well as phlorotannins. These are found on the algae surfaces. These compounds play an important role in defending the algae from worms and snails.

That chemical protection has no effect on Green turtles, which are herbivores. Padina gymnospora is actually edible. Naturally, it contains no heavy metals or toxins. Although no one really uses funnelweed for human food, it has potential for as a natural fertilizer.

In Gorontalo, only staff of Miguel’s Diving will know where to find these beautiful algae. To see for yourself, please make your dive reservations directly with us.

Duncanopsammia peltata forms pagodas in Gorontalo

Posted on February 6, 2024 by Miguel's Diving • 0 Comments

Duncanopsammia peltata or pagoda coral form immense colonies in Gorontalo’s healthy waters.

Stunning Pagoda Coral Colonies

One of Gorontalo’s ancient and stunning coral formations is pagoda coral. Giant plates form spirals, hence the common name denoting pagodas. The colonies featured in this video measure over four meters across. The video is courtesy of @jhonheriano of Pertamina Dive Club.

Other colonies of this distinctive coral form single plates. Additional plates may take several centuries to form. In other coral reefs of the Indo-Pacific region, this coral forms pillars. That morphology has yet to appear in Gorontalo.

Descriptions of Duncanopsammia peltata

The scientific name for pagoda coral is Duncanopsammia peltata. When we consulted coral experts, they asked for a detailed photograph of the polyps. These are distinctive in determining the species. Usually, corallites measure between three and five millimeters in diameters. However, those of the giant colony featured here measure almost one centimeter!

As with other corals, polyps are only found on the upper surfaces of the colony. They need sunlight and easy access to plankton brought by passing ocean currents. Sometimes, the corallites are embedded flush with the coral plate. However, other times they protrude above the plate like little bumps. Typically, the polyps are extended during daylight hours, ready to sunbathe and catch plankton. Their many arms can measure up to one centimeter in length.

Tiny single-cell organisms called zooxanthellae live inside Duncanopsammia peltata. They turn sunlight into food that they share with their host coral.

Colonies of Duncanopsammia peltata live in coral reefs throughout the Indo-Pacific region. They thrive just below the surface, down to a depth of about forty meters. The color is grey to light brown.

Ask us to show you Gorontalo’s pagoda corals when you make your dive reservations directly with Miguel’s Diving.

Dead nudibranch startles divers

Posted on December 11, 2023 by Miguel's Diving • 0 Comments

Dead nudibranch is rarely seen. But one of our sharp-eyed dive masters spotted one along an unnamed section of coral reef.

A Black, Fleshy Mass

Miguel’s Diving staff are always looking for marine life to show to our diving guests. They are skilled in spotting small critters, as well as pelagics that swim past divers who are focused on the amazing coral here.

Recently, a dive master noticed something out of place in a small patch of white sand. The object looked black and fleshy, like the mantle of a clam. However, he knew that no clam lived there in the sand.

With a piece of broken coral, he probed the strange thing. It was clearly dead and lifeless. Upon closer inspection, it was clearly the dead body of a large nudibranch. Round holes remained where the rhinophores had been during life. Towards the back, the area where the gills should have been were completely torn. We have placed circles around the missing dorsal parts in the photograph.

Turning the dead nudibranch over on its back, he saw that the entire area of internal organs was entirely ravished. Only the fleshy body of the dead nudibranch remained.

An Expert Comments on the Dead Nudibranch

Everyone at Miguel’s Diving was curious to learn about this unusual sighting. None of us had ever seen a dead nudibranch before. We wanted to learn how this marine critter could have died. So, we contacted an expert. She is Prof. Dr. Heike Wägele of the Leibniz Institut zur Analyse des Biodiversitätswandels Zoologisches Forschungsmuseum. She kindly responded to our email.

belly — Ventral side showing missing interior parts

She speculated that the nudibranch could have experienced an injury to its back. As a result, fish began to nibble at it. Another alternative could be damage from a parasite. “Copepods usually sit close to the gill and perhaps this has also weakened the animal,” wrote Dr. Wägele. Sometimes, the nudibranch ages and dies naturally.

We also asked her why only parts of the dead nudibranch were eaten and not its body. She responded, “Usually these animals have toxic compounds accumulated in the body, mainly actually in the large body. But the organs are usually less toxic.” Also, the bodies of nudibranchs are full of spicules. Spicules are hard and spiny. They help support the body structure of marine animals that lack bones. Also

Once Alive

Given the extreme decay of the specimen, there is no way to know what species of nudibranch we found dead. However, its shape and size are similar to Ardeadoris egretta. Divers occasionally see this beautiful white nudibranch along coral reefs in Gorontalo.

For your chance to see a living nudibranch, please make your dive reservations directly with Miguel’s Diving.

Flower urchin trembles with danger

Posted on September 13, 2023 by Miguel's Diving • 0 Comments

Flower urchin looks like a lovely ball of trembling flowers. However, those flowers contain highly toxic venom. This sea urchin’s maximum diameter is about 15 centimeters. It lives in areas of sand and rubble along coral reefs. It also inhabits areas of sea grass.

Beauty to Avoid

Although commonly known as the Flower urchin, the scientific name of this echinoderm is Toxopneustes pileolus. The genus name Toxopneustes means “poison breath.” And “skullcap” is the meaning of pileolus , the species name. These names underscore the creature’s deadly possibilities.

Its toxins can cause a number of symptoms. These include breathing problems, muscular paralysis, and numbness. Such effects can render the victim disoriented. The combination can result in accidental drowning. Initial contact gives the victim an extremely painful shock. Then numbness and spasms start to travel through the body from the point of contact. Happily, accidental contact with this sea urchin is extremely rare.

Deceptive Flowers

Various projections cover a Flower urchin’s exposed surface. The most noticeable are the flower-like pedicellariae. These colorful appendages are actually jaws. Each jaw has three prongs. Moreover, the flower-like jaws have sensors that detect contact or proximity movement to the sea urchin. Any touch will trigger the jaws to contract. Then the jaws inject venom. To make matters worse, once the jaws are triggered, they can easily break free from the sea urchin. That means they stay embedded and will continually inject venom for several hours.

The flowers of this sea urchin can appear a pinkish or yellowish white. There will be a single lavender dot in the middle. These false flowers typically cover the short spines of the urchin.

On the underside of the Flower urchin are double rows of tubular feet. These emerge along the ten segments of the urchin’s shell. In the center is the creature’s mouth, which contains five plates. These plates function as teeth that crunch food. Sea urchins forage along the bottom on algae, bryozoans and detritus. With the mouth facing the substrate, the anus faces the water column and any curious passing diver.

Flower Urchin Piled with Debris

To observe a Flower urchin, divers must keep a safe distance. Careful observation of the surface of this creature shows thin, translucent, and waving appendages that are longer that the trembling flowers of the urchin. These appendages are tubular feet that end in three claws. These are used to clear the urchin’s surface of debris.

However, the urchin also uses these tubular feet to move debris from the substrate onto its top and sides. Scientists call this covering or heaping behavior. The tubular feet keep debris in place. The function or purpose of this behavior remains a mystery. Because divers think that a small heap of debris is simply rubble, most flower urchins remain unnoticed.

In the rare instances when we see a Flower urchin, our dive masters will warn guests first and then carefully show the beautiful creature. Afterwards, the dive master will use his stick to move debris on top of the urchin. This helps the urchin but also prevents accidental contact by anyone else passing by.

To dive with such caring dive masters, please make your trip reservations directly with Miguel’s Diving.

Leopard sea cucumber self-mutilates

Posted on March 20, 2023 by Miguel's Diving • 0 Comments

Leopard sea cucumber is a beautiful creature of the ocean floor. However, divers should avoid touching its sensitive body.

Spotted Beauty

The Leopard sea cucumber lives in the eastern Indian and the western Pacific oceans. In the areas we dive in Gorontalo, it can only be found dependably at a single dive site. This sea cucumber lives in sandy areas, flanked by coral reef. Researchers say that it lives from three to almost forty meters deep. We usually find it between 15 and 18 meters here.

Although research claims it can grow to 60 centimeters, those in Gorontalo measure only half of that length. Divers can easily identify the Leopard cucumber. Its spotted pattern is distinctive and unmistakable. The tubular body is grey but sprinkled with random rows spots. These spots are orange and edged in brown.

Avoid Touching

Leopard sea cucumber is highly sensitive. It considers touching, grabbing, or lifting to be a threat. When threatened, it will eject white strings. These elongate in sea water. They also become sticky. Scientists consider this behavior to be defensive.

These white strings are called Cuverian tubes after the French zoologist who first studied them. They are naturally attached to the sea cucumber’s interior respiratory system. When the Leopard cucumber feels threatened, it will contract its body muscles. This contraction is so great that it tears the cucumber’s interior. The contraction forces Cuverian tubes out of its anus. In this way, it self-mutilates.

The Leopard sea cucumber can regrow its tubes. However, this takes several weeks. So, divers should avoid touching this sea cucumber. The tubes contain toxins, which can cause skin irritation in humans. Interestingly enough, researchers are using toxins from the Leopard sea cucumber in cancer research.

Leopard Sea Cucumber in Ecology

This sea cucumber has several rows of tubular feet on its underside. It moves slowly across the sandy bottom. While doing so, it ingests sand and anything the sand contains. In this way, all sea cucumbers clean the ocean floor of detritus and other waste materials.

Moreover, its own waste is beneficial to coral growth. After internal digestion, it excretes calcium carbonate and ammonia along with clean sand.

Home for a Fish

Pearl fish live inside of some Leopard sea cucumbers. The fish’s scientific name is Carapus mourlani. It enters and exits the cucumber via the anus, usually tail first. A scientific study in Indonesia of Bohadschia argus, the official name for the Leopard sea cucumber, found fifteen pearl fish living inside a single cucumber!

Sometimes an Emperor shrimp will be living on the sea cucumber’s surface.

For your chance to see this beautiful creature in Gorontalo, please make your dive reservations directly with Miguel’s Diving.