My favorite jellyfish, chosen by the jellyfish expert!

Hello everyone! Today we're introducing the branching jellyfish. This jellyfish is tiny, with a bell length of about 1mm for juveniles and about 3mm for adults, and even when fully grown, the bell height only reaches about 5mm (※Currently not on display) ▼Adult▼Juvenile The defining characteristic of this jellyfish, as its name suggests, is its tentacles that branch out from the base. At the base of the tentacles are eyespots that can sense light, and they have a tendency to gather around light. Are the polyps (a form of cnidarian, such as jellyfish) also branched? ▼Polyps This jellyfish also has amazing regenerative abilities; as long as the oral stalk (the central part of the bell, with a mouth at the tip) remains, it seems to regenerate beautifully. Also, for some reason, branching jellyfish suddenly appear in various tank. "Where did they come from??"The aquarium keeper are scratching their heads. If you see a tiny transparent jellyfish in another tank , it's usually a branching jellyfish. Jellyfish are often treated as a bit of a nuisance, but the person in charge really loves watching them swim around. They usually stay still at the bottom or cling to something, but they swam around when stimulated during a water change, so please take a look. They're so cute...// We really want everyone to see them, but unfortunately, we don't currently have a tank big enough to display one this size in the "Jellyfish" (T_T). So! We sometimes let visitors see them for a limited time and irregularly at the " aquarium keeper Counter" on the 4th floor of the entrance building. We would be so happy if you could come and see these adorable jellyfish, which are so interesting and the person in charge loves them!

Invertebrates

2026.04.13

The birthday of the Largha seal

The breeding season for Largha seal is from March to May, with births occurring from February to April. February and March were also birthday seasons for the seals at Kaiyukan. So, we presented them with ice cakes to celebrate! Nana, a female born on February 4th, is now 24 years old. Nana is a seal born at Kaiyukan. Be sure to watch out for her adorable tongue-out gesture while she's being fed! It's only for a moment, though! Lapis, a female born on March 1st, is now 14 years old. Lapis is also a seal born at Kaiyukan. She is currently molting (her fur is replaced once a year), so her old and new fur is mixed together. In a week or two, you should be able to see her looking shiny and new! Mio, a female born on March 10th, is now 13 years old. Mio was born at Kamo Aquarium and came to Kaiyukan in 2015. Despite her pretty face, she is actually the heaviest seal at Kaiyukan. Wow, she weighs over 100kg! She's relatively black all over compared to the other seals, so she might be easy to spot. Onpu, a female born on March 19th, is now 4 years old. Onpu was born at Oga Aquarium and came to Kaiyukan in 2024. She's the youngest at Kaiyukan. She recently finished molting and now has the beautiful gray spotted pattern you'd expect from a Largha seal! We're glad her fur grew back so nicely. The seals we'll introduce from here on are individuals rescued from the wild, so their birthdays and exact ages are unknown. Shigenobu, a male estimated to be 13 years old, is currently in breeding season! He's trying his best to impress the females, but it hasn't been very successful for him. After feeding, he always enjoys the aftertaste (nicknamed "umami time," a name the aquarium keeper came up with). A glimpse of Shigenobu's delicious time → The seals can't believe the feeding is over. "Sho," a female estimated to be 22 years old, loves the corners of the tank and gets stuck in all sorts of places, so sometimes it's worrying when we can't see her at all. "Dia," a female estimated to be 22 years old, gave us a wink!! Dia is a mother of one. She is the biggest eater among the seals at Kaiyukan, and immediately makes a groaning sound to get attention when she wants food. Even after feeding is over and she returns to the water, she stares intently from the surface (lol). These are photos from when we presented her with an ice cake. Eat lots and stay healthy! *As enrichment, we give them ice in different shapes than usual at various events.

mammalian

2026.04.11

Six?

Hello! Today, I'd like to introduce a slightly unusual Moon jelly that I found. Moon jelly are characterized by four ring-like patterns in the center of their bodies. These patterns are called "gonads," and are the parts that produce eggs and sperm. Normally, you can see four of these patterns, but the other day, I found one with six! Isn't it cute? ▼Top: Individual with four gonads Bottom: Individual with six gonads It's fun to observe them when you realize that even within the same species, each one has different characteristics. Apparently, there are also individuals with three or five gonads! The individual in the photo is on display in the jellyfish area, so please try to find it! You might be lucky if you find it.

Invertebrates

2026.04.09

Shigenobu's Love Story

Hello everyone. At Kaiyukan , the breeding season for the one male and six female Largha seal living in the Monterey Bay tank began in late February. The Largha seal at Kaiyukan live in the exhibit tank. This time, we'll bring you a record of the male Shigenobu's valiant efforts to impress the females! His first target is Nana. The breeding season for Largha seal is from February to April, and mating often takes place underwater, with the male clinging to the female and biting her neck or back. While Shigenobu was trying his best, Nana had an indescribable expression on her face. Perhaps she was thinking, "I'm in the middle of getting him in!" Next is Sho. While he was being fed on land, Shigenobu made a groaning sound at the surface to get her attention! He tried to come up when feeding was finished. The aquarium keeper were a little taken aback by Shigenobu's desperation, but in the end he couldn't come up and waited sadly. Finally, there's Lapis. As I was doing the final closing work, I heard "Woof!" Huh? A dog? I looked towards the land area and saw Lapis completely rejecting Shigenobu. The source of the dog-like barking was Lapis. Lapis's bark is distinctive, and although I've never heard it myself, I've heard that she sometimes makes a human-like "Kyaaa!!" sound. If I manage to capture it on video, I'll share it with you all♪ Everyone, please come visit Kaiyukan! -->

mammalian

2026.04.07

The growth of the Tufted puffin chick "Iwabokke"

It's hard to believe, but about six months have passed since Iwabokke hatched! The tiny chick has grown quite large. So, let's take a look at how it looked when it first hatched and how it looks now. ▼When it first hatched ▼Currently Its weight was 53g when it first hatched, but it has now grown to 700g! That's almost the same weight as an adult female. Compared to adults, it doesn't have ornamental feathers (tufts) yet, so you should be able to tell it apart just by looking at it. *Ornamental feathers (tufts) are the decorative feathers that grow on the back of the head. ▼The individuals with ornamental feathers (tufts) have grown larger, but they are still growing! We're excited to see what they will look like in the future.

birds

2026.04.05

A glowing jellyfish!?

Hello everyone! This image shows a Kabuto Kurage (Japanese Name) taken during the opening preparations for the "Jellyfish" exhibit. If you look closely, you can see it glowing with beautiful colors. However, this jellyfish does not have the ability to emit light. So why does it appear to glow? We have prepared a video that shows it up close, so please take a look. The Kabuto Kurage (Japanese Name) has eight ridges of bundles of fine hairs (comb hairs) called comb plates. The light reflects off these countless comb hairs, making it appear to glow. Conversely, it does not appear to glow in the absence of light. To put it simply, it is the same principle as the moon. It makes sense that jellyfish are called the moon of the sea (lol). By the way, they can move by moving these comb plates. Some things are difficult to convey in the video, so please come and see this fantastical Kabuto Kurage (Japanese Name) at the Kaiyukan !

Invertebrates

2026.04.03

Japanese giant spider crab larvae have grown into megalopas!

The baby Japanese giant spider crab that I've been introducing on my blog recently are growing well. → Devotion of a crab with eggs → Japanese giant spider crab have hatched! About 10 days after the zoea stage 1 that I introduced last time, they grew to the zoea stage 2. After continuing to change the water and feed them every day, about 10 days after confirming the zoea stage 2 (about 20 days after hatching), we finally confirmed their metamorphosis into megalopa larvae! The megalopa larva is a developmental stage where they are much closer to the shape of a crab. When we actually observed them, we could see them firmly gripping the sand with their legs, and they are starting to look more like crabs than when they were zoea larvae. This year, we have revised our rearing equipment, and we have succeeded in raising many megalopa larvae. From here on, they will molt again and grow into juvenile crabs. We will continue to carefully observe and raise them so that they can safely reach the juvenile crab stage!

Invertebrates

2026.04.02

Iburi Newsletter Vol. 110: "Newts are better than flowers"

These days, Kochi Prefecture is completely enveloped in the warmth of spring, with some days seeing temperatures exceeding 20℃, making it comfortable to wear short sleeves during the day. Speaking of flowers that represent spring, there are rapeseed flowers, and a beautiful field of rapeseed flowers stretches out near the Iburi Center. As someone with hay fever, my nose started to itch just looking at it from inside the car, so I took one photo and left. My main objective today was to see this creature that makes you feel the arrival of spring! This creature hiding in the branch is a Japanese fire-bellied newt. As its name suggests, the Japanese fire-bellied newt has a red underside and is known to have the same toxin, "tetrodotoxin," in its skin as pufferfish. It is a valuable creature designated as a "species of concern" that should be conserved on Kochi Prefecture's Red List. The reason why the Japanese fire-bellied newt makes you feel the arrival of spring is that when spring arrives, which is the breeding season, the base of the tail of the male Japanese fire-bellied newt swells up. The individual we observed this time also had a swollen base to its tail, indicating that it was a male in its breeding season. When we spoke to a local resident, they said, "Back in the day, when we opened the taps on the irrigation canals to fill the rice paddies with water in the spring, they would come out in droves." Apparently, there are fewer rice paddies now compared to the past, and they are seen less often. I felt a little sad that I couldn't be surrounded by a swarm of Japanese fire-bellied newts, but seeing them healthy and ready for their breeding season, I decided to do what I could to help creatures like them! So, I picked up some trash before heading home.

Marine Biological Research Institute "Iburi Center"

2026.04.01

Onpu from the aquarium keeper perspective

Hello! This time, we'll bring you lots of footage of Largha seal seal from the aquarium keeper perspective! Onpu has almost finished molting and now has a beautiful spotted coat, so take a look! First, here she is waving goodbye. Next, she is resting her chin on something. We don't know if it's a habit, but Onpu seems to close her eyes a lot. And here she is, recently she's gotten good at sitting up! What did you think of these glimpses of Onpu that only the aquarium keeper aquarium keeper to see? Onpu is always full of charm! And lastly, we'll also show you a glimpse of Mio that only the zookeepers get to see! * The aquarium keeper manage the health of the animals by checking parts that they normally cannot see or touch through daily training, and they also come up with various ways to keep the animals from getting bored with training.

mammalian

2026.03.31

Changes in how Tufted puffin puffins eat

The Tufted puffin is a seabird that primarily feeds on small fish. In the wild, they are known to carry multiple fish in their beaks at once, and during the breeding season, parent birds have been observed carrying fish side-by-side for their chicks waiting in the nest. This behavior is thought to be possible because they can firmly hold fish with small projections (spine-like structures) on the inside of their beaks. Until now, the Tufted puffin Kaiyukan has fed the tufted puffins whole smelt and sand eels. However, recently, they have been trying various methods of feeding them, such as cutting the smelt in half or into five pieces. The Tufted puffin at the Kaiyukan have generally been seen swallowing fish whole, one at a time. However, since changing how the smelt are given, there has been a slight change in their eating habits. Here it is. This individual, with multiple pieces in its beak, is "Chirippu," a tufted Tufted puffin that lives at the Kaiyukan . Chirippu is an individual that has previously experienced breeding. While Chirippu usually eats one piece at a time, on this day she showed us the sight of her mouth full of fish fillets. Seeing her hold multiple pieces of fish like this was a moment that made us feel that this is the natural behavior of a Tufted puffin. Seeing new behaviors like this just by slightly changing how we feed them is one of the fun things about keeping them as pets. We would like to continue observing the various behaviors of Tufted puffin and the other tufted puffins.

birds

2026.03.25

Barrier reef chromis have reproduced.

We are pleased to announce an update on the Barrier reef chromis that spawned in the "Great Barrier Reef" tank at the Kaiyukan , following up on our previous post about the breeding behavior of damselfish. Since the Barrier reef chromis in our tank continued to spawn, we attempted to raise them in the back area. Initially, we struggled to raise them successfully, but after much trial and error, we have now succeeded in raising them for five months from hatching! According to Kaiyukan research, this is the world's first successful breeding of this species. To allow everyone to see these juvenile fish, which can only be seen at this time of year, they are on display for a limited time at the aquarium keeper counter near the entrance to the special exhibition on the 4th floor of the Kaiyukan entrance building! ▼Juvenile Barrier reef chromis on display Furthermore, the aquarium keeper involved in raising these fish are also giving explanations about the species and their care for one hour each day. We hope you will take this opportunity to see the juvenile fish. ▼Explanation Please be sure to stop by the aquarium keeper counter when you visit the aquarium.

Fish

2026.03.23

How do jellyfish eat?

Can you imagine how jellyfish eat? You can probably imagine how fish or mammals like dolphins eat. However, many people probably can't quite picture how jellyfish eat. One reason it might be difficult to imagine is that there are many different types of jellyfish, some with long tentacles, some with short tentacles, and some even without tentacles at all. But today, we'll introduce how the Pacific Sea Nettle, characterized by its long tentacles, eats. Its food consists of small, shrimp-like creatures called "isazaami" mixed with clam juice, which is fed from above the tank using a dropper. Here's another angle! The tentacles catch the food and it slides smoothly towards the bell. The food is then carried to the mouth on the underside of the bell. When I first saw it, I was amazed at how smoothly the food was transported. You can make discoveries like this and get a lot of stimulation when you're involved in keeping jellyfish. I hope you can all experience some of this stimulation.

Invertebrates

2026.03.18