Crab
Crab
Crab
Crabs are often thought of as a luxury food ingredient. However, there are many types of crabs. We see crabs in various places such as seas, rivers, and drainage ditches, but what kind of life do crabs lead? Let's take a closer look at the ecology of crabs.
Crab Basic Infomation
Belongs to the Decapoda Anomura order, commonly known as the crab suborder
Body length from 2mm to 120 cm, weight from 5g to 20kg
Crabs are found all over the world, from the tropics to the polar regions.
Not only do they inhabit seawater, but they are also found in coastal terrestrial areas and freshwater environments such as rivers.
The sizes of crabs vary from a few millimeters to those with leg spans over 3 meters.
The cephalothorax has five pairs of legs, one of which forms the pincers.
Although walking sideways is characteristic, there are species that walk backwards.
They breathe with gills, so water is necessary for their survival.
That's why crabs are often seen near water.
Crab Q&A
What is the origin of the name 'Crab'?
The name 'Crab' originates from their red shells and the fact that they turn red when boiled. 'Kani' in Japanese can be read as 'shell red' or 'hard to escape' due to their hard shells and quick escape habits. Another theory is that the name came from 'kanu', meaning 'to combine abilities', or it evolved from 'river garden', indicating the ancient presence of river crabs. The kanji character for crab suggests an ancient pronunciation of 'kai', indicating a change in the reading over time.
Why do crabs live there?
Crabs inhabit a variety of aquatic environments including freshwater, brackish water, coastal areas, and deep seas. While few species live on land or in pure freshwater, most are found in brackish areas and ocean waters. Crabs breathe through gills, which must stay moist to function. Even land-dwelling crabs breathe through gills and must keep them moist by recycling a small amount of water they store internally. The Okinawan terrestrial crab breathes through a lung-like organ and doesn't require moisture at all.
What do crabs eat?
Crabs are omnivores. Crab larvae feed on plankton. Adult crabs may eat plants, small animals like starfish, bivalves, polychaetes, starfish, squid, hermit crabs, and even other crabs. Most crabs are scavengers, eating dead animals found on the ocean floor. Some species are also known to practice cannibalism, and snow crabs even consume their own molted shells. Generally, crabs prefer animal matter over plant matter.
Why do crabs blow bubbles?
Crabs breathe through gills. When on land, they store water inside their bodies to breathe through their gills. The bubbles you see are the result of the crab circulating stored water to extract oxygen. The bubbles indicate the crab's effort to maximize oxygen intake from the limited water it holds, and reusing the foamy discharge by recycling it back into the body. This bubbling also signals that the crab might be struggling with oxygen depletion.
Why do crabs turn red when boiled?
Crabs turn red when boiled due to the pigment astaxanthin in their shells, which is bound to protein and appears black or dark. Heating breaks down the protein, releasing astaxanthin and revealing its vibrant color. Astaxanthin is an antioxidant, which helps remove reactive oxygen species from the body and is beneficial for anti-aging.
Why do crabs walk sideways?
Crabs belong to the arthropods and have multiple legs. Their body shape and leg arrangement make sideways walking more efficient and faster, which is crucial for escaping predators quickly. While slow forward movement is possible, rapid sideways walking provides a better escape mechanism by utilizing gaps between their legs.
When do crabs use their pincers?
Crabs use their pincers primarily for eating, by catching live prey and tearing it apart. They also use pincers for defense by intimidating predators. Some species use pincers to hold venomous anemones as a defense strategy. If not used for defense, some crabs use the death-feigning strategy to evade predators. However, pincers are ineffective against bird beaks.
Do crabs shed their pincers?
In a dangerous situation, a crab may detach its pincer to escape a predator's grasp, a process known as autotomy. This joint is specially designed to break easily and seal off to prevent bleeding. The lost pincer will regenerate over time.
Is there a specific day when crabs lay eggs?
Crabs typically lay eggs on specific lunar phases like the full or new moon, coinciding with high tides, which helps in dispersing the eggs. This behavior is consistent even among land-dwelling crab species.
Can crabs swim?
While crabs are generally perceived as walking on sand, some species, like the swimming crab, can swim using their specially shaped last pair of legs. These legs act like paddles, allowing the crab to swim sideways and adjust its direction underwater.
What is the largest crab in the world?
The largest crab species is the Japanese spider crab, which can reach a leg span of up to 3.8 meters and weigh up to 19 kg. It is found in the deep waters around Japan and can be seen in aquariums and also consumed as food, although it is said to have less flavor compared to other crabs like the king crab.
What is the smallest crab?
The smallest crab is the pea crab, which measures about 0.8 cm for males and 1.2 cm for females. They live parasitically inside bivalve shells, utilizing the oxygen the host bivalve filters.
How can you tell the sex of a crab?
Male and female crabs can be distinguished by examining their abdominal flaps. Females have a broad, rounded flap, while males have a narrow, triangular flap.
Do crabs feel pain?
There is debate about whether crabs, as invertebrates, feel pain. Some studies suggest that crabs react to harmful stimuli and may even remember and avoid such situations, indicating a form of pain perception.
Which is tastier: snow crab or king crab?
Snow crabs are known for their sweet flavor and edible crab miso. They are also more affordable than king crabs. King crabs are larger, offering meaty legs with a firm texture, but they are leaner and milder in flavor. Unlike snow crabs, king crab miso is not typically consumed due to its unpalatable texture.
What is the most expensive crab in Japan?
The most luxurious crab in Japan is the branded 'Itsukiboshi' Matsuba crab, known for fetching extremely high prices at auction, recognized by the Guinness World Records. It is highly prized for its dense meat and exquisite flavor.
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Crab Type of List
- Snow Crab
- Japanese Spider Crab
- Yellow Crab
- Freshwater Crab
- Mud Crab
- Chinese Mitten Crab
- Mountain Crab
- Stone Crab
- Red Crab
- Horseshoe Crab
- Fan Crab
- Smooth-round Crab
Information
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Crab References
- ・カニのくらし 2005年4月1日新装版第1版 株式会社あかね書房
- ・Wikipedia https://ja.wikipedia.org/wiki/カニ
- ・語源由来辞典 https://gogen-yurai.jp/kani/#:~:text=カニの語源には,変化したなど諸説ある。
- ・かにカニ福井 https://kani.fukuishimbun.co.jp/news/171.html#:~:text=貝類やゴカイの仲間,も観察されています。
- ・モノシリ https://www.ipros.jp/monosiri/science/89/2#:~:text=正解は 「エラ呼吸」&text=体の中に水,体内に戻しています。
- ・カニ通販比較 https://xn--t8jb7ba1g9fu499dm0f.com/ecology-of-crab/or-eat-anything-crab/
- ・知識の宝庫！目がテン！ライブラリー https://www.ntv.co.jp/megaten/archive/library/date/02/08/0811.html
- ・魚の食べ方探求 https://seafood-reference.com/kani/kani-seitai/entry1091.html
- ・学研 キッズネット https://kids.gakken.co.jp/kagaku/kagaku110/science0167/
- ・iloveai https://ailovei.com/?p=71688
- ・朝日新聞デジタル https://www.asahi.com/articles/ASLCS4GR2LCSPUUB001.html#:~:text=鳥取市の鳥取港,も認定されている。
Crab Introduction of media used
出典：https://pixabay.com/videos/id-47896/
出典：https://pixabay.com/videos/id-92545/
出典：https://www.pexels.com/ja-jp/photo/4890161/
出典：https://pixabay.com/images/id-1532115/
出典：https://www.pexels.com/ja-jp/photo/73769/
出典：https://pixabay.com/images/id-1532115/
enemy
出典：https://pixabay.com/images/id-2808995/
出典：https://unsplash.com/ja/写真/3UnSsi2oWjs
出典：https://commons.wikimedia.org/wiki/File:Daegae-jjim_1.jpg
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