Living creature information
We are exhibiting baby Japanese giant spider crab, the world's largest crab species.
April 21, 2026
We have begun exhibiting five baby Japanese giant spider crab crabs (megalopa larvae) that were born at Kaiyukan on Tuesday, March 3rd.
[Megalopa larva of the Japanese giant spider crab(approximately 3 mm)]
On Tuesday, March 3, 2026, aquarium keeper discovered that baby Japanese giant spider crab had been born in the tank . Approximately 500 of them were moved to a reserve tank, where they were fed with Artemia and sakura shrimp while their growth was monitored.
Immediately after birth, baby crabs are called "zoea larvae" and look very different from adults. Through repeated molting, they grow into "megalopa larvae" and then into "juvenile crabs" that resemble adults.
The baby crabs on display are megalopa larvae, which are extremely small, measuring only about 1 mm in body size and approximately 3 mm even with their legs extended. They are expected to grow into juvenile crabs (approximately 1 cm with legs extended) in the near future.
At the Kaiyukan, we have successfully raised crabs to the "juvenile" stage twice in the past, in 2023 and 2025, and in 2025 we exhibited them for visitors to see.
This time, we hope you will take a look at the precious sight of the Japanese giant spider crab crab, the world's largest crab, which can only be seen at this time of year, and feel the mystery of life as you observe the differences in size and appearance between the young and adult forms.
Additionally, the growth of the Japanese giant spider crab crab larvae is also featured on the blog "Behind the Scenes at Kaiyukan" .
| Period | April 21, 2026 onwards (end date undecided) |
|---|---|
| place | Kaiyukan aquarium keeper counter on the 4th floor of the Kaiyukan Entrance Building |
| kinds | Five megalopa larvae (approximately 3 mm) of the Japanese giant spider crab. |
*Exhibition may be canceled at short notice depending on the condition of the animals.
Japanese giant spider crab
English name: Japanese giant spider crab
Scientific name: Macrocheira kaempferi
The male is the world's largest crab, with its claws spread to over 3m .
It is also the world's largest species among arthropods, a larger taxonomic group, and is mainly found in the waters off the coast of Japan, but has also been caught in Taiwan and other places.
They usually live in deep waters and are known to migrate to shallow waters in the spring to spawn.
Check out this creature's blog too!
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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! They have grown from the first zoea stage, which I introduced last time, to the second zoea stage in about 10 days.
Invertebrates
2026.04.02
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The Japanese giant spider crab have hatched!
The other day, we introduced a female Japanese Japanese giant spider crab carrying eggs. (→ "The Devotion of a Crab with Eggs") The aquarium keeper observed the exhibit area every day, eagerly awaiting the birth of the babies. And in early this month...the babies were born safely.
Invertebrates
2026.03.12
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The devotion of the roe crab
The other day, new Japanese giant spider crab arrived in the "Japan Deep" tank . The new female crabs are "carrying crabs" who are carrying eggs. After spawning, the females keep the eggs inside their abdomens (also called loincloths) and keep them safe until they hatch.
Invertebrates
2026.01.17
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I took it off
In the morning, when I looked at the "Special Exhibition "Gyugyu-tto Cute" dome tank, I found some shells that had fallen off! Hmm, a massacre? Not at all. The Blood red fire shrimp had molted. Actually, there were two Blood red fire shrimp here, and two
Invertebrates
2025.10.02
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The baby Japanese giant spider crab are growing well!
The Japanese giant spider crab larvae I introduced the other day have transformed from "Zoea 1" to "Zoea 2" soon after being raised. It looks like the back is more raised than Zoea 1. Zoea 1 Zoea 2 After that, I continued to feed and change the water every day.
Invertebrates
2025.04.22
Latest News
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2026.04.27
news
The exhibit of the Tufted puffin will end on May 10, 2026.
Due to the renovation of the "Aleutian Islands" tank, the exhibit of the Tufted puffin will end on Sunday, May 10, 2026. Kaiyukan collaborated with Aqua World Ibaraki Oarai Aquarium to promote joint research on the ecology and breeding of Tufted puffin, and began exhibiting them on June 29, 2018, after receiving a transfer of Tufted puffin from the aquarium. Since then, a total of three puffins have been successfully bred, and one of them has even been successfully raised artificially, so we believe that we have achieved a certain degree of success in achieving our initial objectives. The Tufted puffin will be kept in the back area for health management before being moved to Aqua World Ibaraki Oarai Aquarium. Further details regarding the renovation of the "Aleutian Islands" tank will be announced as soon as they are decided.
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2026.04.21
Living creature information
We are exhibiting baby Japanese giant spider crab, the world's largest crab species.
On Tuesday, March 3rd, we began exhibiting baby Japanese giant spider crab crabs (megalopa larvae, 5 individuals) that were born at the Kaiyukan . [ Japanese giant spider crab crab megalopa larvae (approx. 3 mm)] On Tuesday, March 3rd, 2026, aquarium keeper discovered baby Japanese giant spider crab crabs born in the tank . Approximately 500 of them were moved to a reserve tank, where they were fed with Artemia and sakura shrimp while their growth was monitored. Immediately after birth, the babies are called "zoea larvae" and look very different from adults. Through repeated molting, they grow into "megalopa larvae" and then into "juvenile crabs" that resemble adults. The babies on display are "megalopa larvae," and are very small, with a body size of only about 1 mm and a leg span of about 3 mm. They are expected to grow into juvenile crabs (approx. 1 cm with legs spanned) in the near future. At Kaiyukan, we have successfully raised giant spider crabs to the juvenile stage twice in the past, in 2023 and 2025, and in 2025 we exhibited them for visitors to see. This time, we would like you to come and see the precious sight of the world's largest crab, the Japanese giant spider crab, which can only be seen at this stage, and feel the mystery of life from the difference in size and shape between the juvenile and adult crabs. The growth of the Japanese giant spider crab crab larvae is also introduced on the blog "Behind the Scenes at Kaiyukan ". Period April 21, 2026 onwards (end date undecided) Location aquarium keeper counter, 4th floor of Japanese giant spider crab Kaiyukan entrance building Species 5 giant spider crab megalopa larvae (approximately 3 mm) *The exhibit may be suddenly canceled depending on the condition of the creatures. Japanese giant spider crab crab English name: Japanese giant spider crab Scientific name: Macrocheira kaempferi Males can extend their claws to more than 3 meters, making them the world's largest crab. It is the world's largest species of arthropod, a larger taxonomic group, and is mainly distributed in the waters around Japan, but has also been caught in Taiwan and other areas. It is known to normally live in deep-sea areas and migrate to shallow waters in the spring to spawn.
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2026.04.16
news
[April 24th onwards] Prohibition of bringing carry-on cases and large luggage Aquarium the Kaiyukan .
Regarding the prohibition of carry-on cases and large luggage Aquarium the Kaiyukan : The rules for bringing in items have changed as of April 24th. For details, please click here. Carry-on cases and carts Pet carts Items with a total of three sides exceeding 120cm (any single side exceeding 70cm) *Please leave them at your hotel or in a coin locker before coming to the aquarium. *For details on coin lockers at Kaiyukan and Tempozan Harbor Village, please click here.