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

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Yearly Archives: 2023

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.

Arothron caeruleopunctatus pufferfish hiding in plain sight

Posted on February 21, 2023 by Miguel's Diving • 0 Comments

Arothron caeruleopunctatus is a large pufferfish that hid in plain sight until a Japanese researcher named it in 1994.

Not the Other Blue-spotted Puffer

Scientific names are always best to identify marine life. Although the name of the large puffer Arothron caeruleopunctatus means “blue-spotted,” another small pufferfish is often called the Blue-spotted puffer. That fish is a small toby named Canthigaster solandri. It has various blue spots and a colorful body. An internet search for a blue spotted puffer will produce photos for C. solandri, not A. caeruleopunctatus.

Arothron caeruleopunctatus can measure to 80 centimeters in length. That makes this species one of the largest pufferfishes worldwide. Divers giving it a casual glance would find it uninteresting. Its body is primarily dull with hues of gray and dark blue. Ventrally, it is often white. Dorsally, it can have a yellow, irregular blotch. The fish’s scientific name comes from the numerous blue to white spots found on its body. These are round to rice shaped. Also, concentric lines circle the fish’s eyes.

Unnoticed until 1994

Divers assumed that this oval-shaped fish was one of the other large puffers that live in Indo-Pacific waters. However, in 1994, Dr. Keiichi Matsuura published his finding of this pufferfish that had been hiding is plain sight. Dr. Matsuura is curator emeritus at the zoology department of the Museum of Nature and Science in Tsukuba, Japan.

In addition to Arothron caeruleopunctatus, he has discovered and named other pufferfishes. These include Arothron multilineatus (2016) from Ryukyu Islands, Japan, and Chelonodontops alvheimi (2018) from Myanmar. Also, he named a new Fugu puffer, Takifugu flavipterus (2017) from Japan, Korea, China, Taiwan, and Far East Russia. Another pufferfish he named is Canthigaster aziz (2020) from the northern Red Sea off Saudi Arabia.

Arothron caeruleopunctatus in Gorontalo

Divers can see this Blue-spotted puffer occasionally along Gorontalo’s coral reefs and deep walls. Like other large pufferfishes, it is quite shy around divers. Careful approach can reward a patient diver with a clear view of the blue-spotted pattern of this fish. It lives from two meters to below safe diving limits.

A close look reveals that its skin lacks scales. Also, its dorsal and anal fins are small. These are located towards the back of its body and are symmetrical. Moreover, it lacks a pelvic fin. Its short snout has two pairs of nostrils. It feeds on invertebrates that live on the substrate. To feed, it uses its four strong teeth. This pufferfish is active during the day.

For your chance to see Arothron caeruleopunctatus in Gorontalo, please make your dive reservations directly with Miguel’s Diving.

Thylacodes grandis captures plankton in its net

Posted on January 30, 2023 by Miguel's Diving • 0 Comments

Thylacodes grandis, or the Grand Worm Sail, uses mucous like a net to capture plankton. Its beautiful batik-patterned head is unmistakable.

Grand Worm Snails in the Reef

Worm snails are a family of marine molluscs. They live in long tubes rather than the usual coiled chambers of other snails. Worm snail tubes are irregular. Grand worm snails in Gorontalo measure about seven to ten centimeters in height. A worm snail will grow its tube from a hard substrate on the reef. Sometimes, a Grand worm snail will live separated from other marine life. More often, it will grow up among various corals with only its head above. Since these worm snails are long lived, hard corals can grow on the tubes.

Grand worm snails live in all Gorontalo’s coral dive sites. However, divers can easily overlook them. Most distinctive about this species is its lack of a cap. Also known as an operculum, the cap shuts the tube from the top, thus protecting the worm snail inside. Because it lacks this cap, the Grand worm snail’s head is exposed for divers to see. It has a distinctive maze of white to golden lines over a dark background. This background can be black to deep maroon. It resembles batik. Also apparent are the creature’s fleshy horns. When a diver approaches, the Grand worm snail will duck its head down into its tube.

Fishing with Mucous

Worm snails gather food by producing mucous steams. Their gills create a slight current. This current sends plankton, that floats in the water column, into its sticky mucous. A careful diver can watch as the Grand worm snail rotates its head and draws its mucous net into its mouth.

An easy way to search for worm snails in Gorontalo is simply to look for the mucous strands floating above the reef. The most common worm snail here is Dendropoma maxima. It grows from inside massive coral heads, often in groups. Since this species has a dark cap, divers can easily distinguish it from Thylacodes grandis. Grand worm snails in Gorontalo typically live below fifteen meters.

Thylacodes grandis and other names

Some older resources give the scientific name as Serpulorbis grandis. This is not an accepted name. Vermetus grandis is another unaccepted name associated with the Grand worm snail. Taxonomic work done in 2005 and 2006 has yet to be harmonized. However, there are over forty confirmed species in the Thylocodes genus. These include two new species, one in 2017 and another in 2018. The most beautiful and photogenic worm snail in Gorontalo is indeed Thylacodes grandis.

To see a Grand worm snail in action, please make your dive reservations directly with Miguel’s Diving.