Back in 1975, a neurobiologist named Victor Benno Meyer-Rochow was spending time out in Indonesia. And while the scientist was in the attractive Southeast Asian nation, he whiled away some time by diving close to the Banda Islands – a band of ten tiny landmasses that all rest in the Banda Sea. A leopard sea cucumber caught Meyer-Rochow’s eye during that jaunt, too, and so he decided to bring the creature up to the surface. But, as it turned out, this would be no ordinary sea cucumber. In fact, when the diver discovered what was lurking within the marine animal, his stomach turned over.
There are countless landmarks around the world that attract plenty of attention from international visitors. From the Eiffel Tower to the Taj Mahal, these iconic locations still have the power to draw tourists to their respective countries every year. For some people, though, the ocean floor is a much more appealing place to explore.
After all, the ocean is often a place of tranquillity – far removed from the hustle and bustle on land. But while just going out on a boat and enjoying the sea breeze is enough for many, there are others who prefer to take a closer look at what’s beneath the surface.
Meyer-Rochow decided to explore the depths, in any case, during his dive in Southeast Asia over 40 years ago. And, as we previously mentioned, the neurobiologist found an eye-catching sea cucumber during the excursion that he ultimately decided to bring up to his boat. Perhaps nothing could have prepared him, though, for what happened later that day.
As we all know, the ocean houses some truly remarkable creatures. But while predators such as sharks and killer whales often spring to mind when discussing the denizens of the deep, there are definitely other intriguing animals below the waves. Take, for example, echinoderms – varieties of which you may have spotted while out swimming in the sea or washed up on the beach.
Echinoderms are marine lifeforms that all fall under the phylum Echinodermata. And some of these creatures are instantly recognizable; sea urchins, crinoids, brittle stars and starfish are all echinoderms, for instance. In fact, it’s believed that the phylum Echinodermata covers around 7,000 separate species in the sea.
There’s also one more echinoderm that you may recognize if you were to see it: the sea cucumber. Yes, as its name suggests, the marine animal bears a distinct resemblance to the green salad vegetable. And much like the phylum Echinodermata as a whole, sea cucumbers exhibit a huge amount of variation.
Incredibly, there are said to be over 1,700 different kinds of sea cucumber out in the ocean – all ranging in size and appearance. These creatures spend most of their time on the seabed – both in shallow waters and in the depths – although they are also known to conceal themselves under the ocean floor on occasion.
Given how sea cucumbers look, however, you may be wondering how they breathe and eat. Well, the animals inhale and exhale through, of all things, the anus. The water that a sea cucumber takes in as a result of this process subsequently travels up into what is known as the “respiratory tree” – thus keeping the creature alive.
With regards to food, meanwhile, the National Geographic website has explained more. A post on the site reads, “Sea cucumbers feed on tiny particles like algae, minute aquatic animals or waste materials. They gather [the food] in with eight to 30 tube feet that look like tentacles surrounding their mouths.”
The National Geographic description continues, “The animals break down these particles into even smaller pieces which become fodder for bacteria – and thus [they] recycle them back into the ocean ecosystem. Earthworms perform a similar function in terrestrial ecosystems.”
But how do sea cucumbers reproduce? Well, as National Geographic reveals, the echinoderms have a choice in how they go about breeding. The process can occur in a couple of ways, in fact – although one of these methods is usually more prevalent than the other.
The National Geographic post explains, “Sea cucumbers can breed sexually or asexually. Sexual reproduction is more typical, but the process is not very intimate. The animals release both eggs and sperm into the water, and fertilization occurs when they meet. There must be many individuals in a sea cucumber population for this reproductive method to be successful.”
And while the sea cucumber is naturally targeted by various predators, it does have a rather helpful defense mechanism. You see, in an attempt to deter any hungry fish, the animal can release its “Cuvierian tubules,” which can be found at the base of the respiratory tree.
If a predator gets too close, then, the tubules will stick to their body and take them – at least temporarily – out of action. Surprisingly, though, that’s not the only thing that a sea cucumber can do when faced with immediate danger. And the alternative option can be quite a sight, as the animal takes full advantage of its regenerative capabilities.
Speaking to Wired in 2014, marine biologist Christopher Mah provided some insight into this particular defense. And according to Mah, a sea cucumber can get out of a difficult situation by employing a particularly unorthodox – and stomach-churning – move.
“Probably the best thing that sea cucumbers are known for is evisceration, which [means] tossing their guts out at predators when they are harassed by them,” Mah explained to Wired. “So you have a crab or a fish or something, and what they’ll do is literally eviscerate [their own intestines].”
To really hammer the point home, Mah then provided a vivid description of the sea cucumbers’ actions. He added, “[They] just take a good chunk of their intestine that will spool out of their body and get shot out at the predator, or whatever, as a distraction.”
As for where you can find sea cucumbers? Well, they aren’t restricted to certain parts of the globe. Indeed, species of the aquatic creature can be found around the planet – although they are usually located on the ocean floor, of course. That said, many sea cucumbers do specifically settle around Asia, as Meyer-Rochow found out back in 1975.
A native of New Zealand, Meyer-Rochow left his homeland to pursue studies in Germany. The future neurobiologist took a real interest in marine sciences during that period, although he ultimately graduated as a biology student. Then, following his stint at the University of Hamburg, he left academia altogether for a spell.
You see, Meyer-Rochow was offered the chance to work at North German Radio – better known as NDR. And during his time at the broadcaster, he not only worked on two educational movies, but he also helped put together a short series about the Netsilik Inuit.
To back up his work on the Inuit, Meyer-Rochow produced a lengthy written feature regarding the indigenous peoples’ way of life. This piece was ultimately printed in a 1972 edition of German medical publication Selecta. Following his time at NDR, however, Meyer-Rochow headed back to Oceania to pursue a PhD at the Australian National University.
And during this period – which coincided with his trip to Indonesia – the researcher was particularly interested in what he has since termed “crustaceans of the deep sea.” It’s perhaps no surprise, then, that an example of Bohadschia argus – more commonly referred to as the leopard sea cucumber – came to Meyer-Rochow’s attention during his dive.
After all, compared to some other species, the leopard sea cucumber is an eye-catching creature. Sporting bright yellow markings on its back, it shares a similar aesthetic to the big cat for which it’s named – although any comparisons end there. And given the animal’s noticeable appearance, Meyer-Rochow couldn’t help but spot it below the surface.
From there, Meyer-Rochow brought the leopard sea cucumber back up to his boat, where he measured the creature. The researcher found, moreover, that this particular specimen came in at just over a foot long and at around 5 and a half inches in width. Then, once that appraisal had been completed, the Kiwi placed the sea cucumber in a cold space.
However, not even Meyer-Rochow could’ve predicted what happened next. You see, when the leopard sea cucumber was in the cooler room, a very thin-looking fish left its anal passage. That wasn’t the only one to emerge, either; in total, 14 more creatures exited the echinoderm over a ten-hour period.
In the end, only one other fish remained inside the leopard sea cucumber – although the number that had already vacated the creature had left Meyer-Rochow stunned. These aquatic lifeforms were pearlfish, and the previously mentioned behavior isn’t all that unusual for them, as National Geographic has explained on its website.
The publication reveals, “There are many species of pearlfish. Some live independently, but several make their homes in the bodies of shellfish, starfish and other marine animals. Indeed, they got their name after one individual was found inside an oyster – dead and embedded within mother of pearl.”
And, naturally, pearlfish can occasionally be found within sea cucumbers. “Sea cucumbers are [the pearlfish’s] most infamous hosts,” National Geographic adds. “Having found [an example] by following its smell, a pearlfish will dive into the anus headfirst. If the sea cucumber objects and closes down its anus… well, it still has to breathe.”
A biologist named Eric Parmentier broke things down even further by describing the pearlfish’s approach to infiltrating the sea cucumber. And according to Parmentier, the fish uses one of two methods to pull this off. The first of these is the one that was mentioned by National Geographic: namely, the creature uses its head to navigate the anal passage.
If that doesn’t work, though, the second option comes into effect. Instead of going head first, the pearlfish then tries to enter the sea cucumber by backing into it. Then, once the tail is in, the fish slowly makes its way up the anus.
Parmentier told Wired, “The reason for this second strategy is that the host has detected the presence of the fish. And, in response, [it] closes its anus. But the host has to breathe, so it has to dilate the anus to realize the water flow. The fish blocks the aperture, and the host has to enlarge this opening more and more.”
As for why the pearlfish looks to infiltrate the sea cucumber? Well, there are a few explanations. For one, the echinoderm’s anal passage can prove to be a safe place to take shelter. In other instances, though, the fish may take on a parasitic role by feeding off the sea cucumber’s reproductive organs.
Yet none of this quite explains what happened with the leopard sea cucumber back in 1975. In that case, it appeared that the pearlfish may have come together inside the animal to reproduce themselves. And with all this in mind, you may be asking yourself why the sea cucumber’s defensive strategies didn’t come into play.
As it turns out, though, pearlfish are able to shield themselves from a sea cucumber’s saponins – a form of poisonous chemical – via a type of mucus that they produce. In that way, the toxins don’t have the desired effect, and this makes the sea cucumber an enticing home. The parasitic fish doesn’t set off the evisceration mechanism, either – and this has proved quite the conundrum for marine biologists.
But there may actually be another way for certain species of sea cucumbers to ward off any interlopers. You see, some of the echinoderms have a number of spinal-like features around the outside of their anal passages. And as these can potentially act like a shield, the creatures may therefore be protected from the likes of pearlfish and crustaceans.
Mah suggests otherwise, though. “The part that hasn’t really been substantiated is the fact that you have some sea cucumbers that have these kind of spines around the anus called anal teeth,” he told Wired. “And it isn’t clear if these anal teeth really are active defensive mechanisms that keep things like fish and crabs out.”
Instead, Mah suggested that these anal teeth may simply be for show. But while this mystery remains, the story about Meyer-Rochow’s find has clearly stood the test of time. In the years since the neurobiologist made his bizarre discovery, you see, the tale has found its way on to social media and a number of online outlets.
The Now Science News Facebook page shared the story in 2019, for instance, with all of the details recounted in a lengthy message. A video was also posted alongside the words that showed the pearlfish in action. And since that post was created in July of that year, it’s gone on to make a notable impact on the social media website.
The video has earned in excess of 58,000 views on Facebook in that time, for instance, with the post itself also registering more than 180 likes and close to 250 shares. And, unsurprisingly, many commenters have relayed their shock at the aquatic invasion – proving that Meyer-Rochow’s sea cucumber and its unusual contents still have the power to disturb more than four decades on.