Poisonous fish - Dokugyo (English spelling)

Japanese: 毒魚 - どくぎょ（英語表記）toxic fish

This refers to fish that have poisonous substances in parts of their body that can kill or cause severe physiological disorders in other animals. Poisonous fish include those that have poison glands in their spines and sting other animals, those that have poisonous parts of their body that can cause poisoning if eaten by humans, and those that secrete poison from their body surface into the water and paralyze other animals.

[Akira Ochiai and Kunio Amano]

Poison

Fish that secrete venom from venom glands around the spines of their fins, causing severe pain or death to other animals, are called venom glands. The venom glands are connected to the spines, but are not connected by tubes and do not open on the surface of the body. When the spines pierce another animal, the epidermis of the venom gland breaks and the venom that leaks out flows in through the wound. Having venom glands in the spines dramatically increases the defensive effect against predators. Some types of spines have serrated edges, which widen the wound to make it easier to insert the venom, or make it difficult for the venom to escape from the body of another animal. The poison is an unstable protein that causes pain, nausea, diarrhea, difficulty breathing, and a drop in blood pressure. The long, sharp tail spines on the back line of the tail of stingrays, eagle rays, and black stingrays, and the spines on the dorsal and pectoral fins of catfish such as the red porgy and the striped catfish contain venom. Scorpionfish have poison glands in the spines of their dorsal, anal, and pelvic fins. The venom of the stonefish, devil scorpionfish, scorpionfish, and lionfish in particular can be deadly to humans.

The weaver fish Trachinus vipera , which resembles a stonefish and lives in shallow waters off the western coast of the North Atlantic and the Mediterranean coast, is a well-known venomous fish and is feared by local shrimp fishermen. This fish has venom glands in several spines on its dorsal fin and two spines on its gill cover. Rabbitfish also have about 20 spines in total on their dorsal and anal fins and four spines on their pelvic fins, all of which have venom glands.

[Akira Ochiai and Kunio Amano]

Food poisoning

(1) _Pufferfish poison This is the most toxic of all _fish poisons, and many people die from food poisoning due to this poison. The structural formula of pufferfish poison is _C11H17N3O8 , and it has only one carbon ring, a guanidine group, _six hydroxyl groups, and a hemilactal group, and is named tetrodotoxin. In 1972 (Showa 47), Toshio Goto (1929-1990) and Yoshito Kishi (1937-) of Nagoya University synthesized a substance identical to the natural substance. This crystal does not dissolve in water or organic solvents, but does dissolve in acidic water, and is stable against heat, not decomposing even at 300℃. Poisoning appears 20 minutes to 3 hours after eating, and after sensory paralysis, speech disorder, headache, abdominal pain, nausea, low blood pressure, difficulty breathing, and loss of consciousness, death can occur within a few hours.

This poison is not only found in pufferfish, but also in the Tsumugi goby and the amphibian California newt. It is found in all species of pufferfish, except for the mackerel puffer, in the Tetraodontidae family, but not in the boxfish or boxelder fish families. In Japan, the tiger puffer, crow puffer, spotted puffer, and other commonly eaten pufferfish are poisonous, as well as the red puffer, common puffer, grass puffer, and striped puffer. The poison is particularly prevalent in the ovaries and liver, followed by the skin and intestines, but the amount in the blood and muscles is small and not a problem. The toxicity of pufferfish changes depending on the season, and is strongest during the spawning season from winter to spring. There is also a large difference in the toxicity of individual pufferfish of the same species, and those found south of the Amami Islands are highly poisonous. The dokusaba puffer, which is very similar to the non-poisonous white mackerel puffer, also has highly poisonous muscles, and the black mackerel puffer has highly poisonous ovaries and liver, so it is extremely dangerous to eat them by mistake.

(2) Ciguatera poisoning Eating fish containing a poison called ciguatera can cause diarrhea, nausea, abnormal temperature sensations, joint pain, and headaches, and can eventually lead to coma and death. The word ciguatera comes from the fact that the cigua, a type of snail found in the Caribbean, causes poisoning symptoms in the nervous and digestive systems. Snappers, moray eels, barracudas, groupers, horse mackerels, stingrays, and parrotfish that live mainly on coral reefs and rocky areas in tropical and subtropical regions may be ciguatera toxins. The toxicity is higher in the internal organs than in the muscles. Ciguatera toxicity varies from region to region and year to year even within the same species, and there is also significant variation between individuals and parts of the body. This makes preventive measures extremely difficult. One of the reasons for this is thought to be the accumulation of toxins through the food chain. In other words, it is thought that the poison is transferred to herbivorous fish such as the southern brushtail moth that eat the toxic algae, and then to carnivorous fish that eat these fish.

A different type of food poisoning that causes hallucinations, different from ciguatera, is known to occur in several species of tropical fish, including mullet and goatfish. Large fish, such as sharks, conger eels, and tuna, also accumulate large amounts of vitamin A in their livers, which can cause headaches, peeling skin, and rashes.

[Akira Ochiai and Kunio Amano]

Skin poison

Boxfish, Japanese auklets, striped puffers, swampfish, Japanese spotted groupers, Japanese spotted groupers, Japanese longfin reef fish, Japanese slugs, and Japanese common gobies release toxins from the secretory glands of the mucus cells in their skin, killing fish that live with them in a short time. The skin toxins are grammistins and grammistin-like toxins, and those in boxfish and Japanese auklets are called pahutoxins. The toxins have a bitter taste and are both toxic and hemolytic.

[Akira Ochiai and Kunio Amano]

"Poisons of Fish and Shellfish" by Yoshiro Hashimoto (1977, University of Tokyo Press)

[Reference] | Fish and shellfish poisoning | Fish | Ciguatera | Pufferfish poisoning

Stingray (ecology)
It has a flat body and often buries itself in the sand. The poisonous stinger on its tail contains a neurotoxin. © Underwater Fort Enterprise, Isamu Soyama ">

Stingray (ecology)

Striped catfish (ecology)
They have poison glands in the spines of their dorsal and pectoral fins. During the day, young fish swim in spherical schools. © Underwater Fort Enterprise, Isamu Soyama ">

Striped catfish (ecology)

Stonefish (ecology)
The body color is mostly pale red, but there is considerable variation among individuals. The spines on the dorsal, anal, and pelvic fins are highly poisonous. © Underwater Fort Enterprise, Isamu Soyama ">

Stonefish (ecology)

Devil stinger (ecology)
The head is very uneven, and the mouth is large and facing upwards. The body color varies depending on where it lives. The dorsal fin is highly poisonous, but the lean white meat is said to be delicious. © Underwater Fort Enterprise, Isamu Soyama ">

Devil stinger (ecology)

Lionfish (ecology)
It has spines containing poison glands on its dorsal, anal, and pelvic fins. © Underwater Fort Enterprise, Isamu Soyama ">

Lionfish (ecology)

Rabbitfish (ecology)
It swims around reefs and eats seaweed and small animals. Its English name is rabbitfish because of its rounded snout, teeth, and face that resembles a rabbit. It has many local names such as Ai, Ae, and Paris. Its spines are highly poisonous. © Underwater Fort Enterprise, Isamu Soyama ">

Rabbitfish (ecology)

Boxfish (ecology)
The body is yellowish brown, with pale blue spots on each scale of the shell. It secretes a mucus poison from its skin. © Underwater Fort Enterprises, Isamu Soyama ">

Boxfish (ecology)

Kusafugu (ecology)
The dorsal side of the body is grayish blue-green with numerous white dots scattered on it, and the ventral side is white. The ovaries, liver, and intestines are highly toxic, the skin is highly toxic, and the meat and testes are weakly toxic. © Underwater Fort Enterprise, Isamu Soyama ">

Kusafugu (ecology)

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

体の一部に有毒物をもち、ほかの動物を殺傷したり、著しい生理障害をおこさせたりする魚類をいう。毒魚には、棘(とげ)に毒腺(どくせん)をもっていて、ほかの動物を刺すもの、体の一部に毒性があって、それを人が食べて中毒をおこすもの、体表から水中へ毒を分泌してほかの動物を麻痺(まひ)させるものなどがある。

［落合　明・尼岡邦夫］

刺毒

ひれの棘などの周りにある毒腺から毒液を出して、ほかの動物に激痛を与えたり、死なせたりする魚類を刺毒魚とよぶ。毒腺は棘に接しているが、管でつながっていないし、体表にも開口していない。棘がほかの動物に刺さると毒腺の表皮が破れて流出した毒が傷口から流入するようになっている。棘に毒腺をもつことにより、捕食者からの防御効果を飛躍的に増大させることができる。棘は種類によっては鋸歯(きょし)状を呈し、傷口を広げて毒液を入れやすいようになっていたり、ほかの動物の体から抜けがたいようになっていたりする。毒物は不安定なタンパク質であり、痛みのほか、吐き気、下痢、呼吸困難、血圧低下をおこす。アカエイ、トビエイ、ツバクロエイなどの尾部背中線上にある長く鋭い尾棘(びきょく)、アカザ、ゴンズイなどナマズ類の背びれと胸びれの棘には刺毒がある。カサゴ類には背びれや臀(しり)びれ、腹びれの棘に毒腺がある。とくにダルマオコゼ、オニオコゼ、ヒメオコゼ、ミノカサゴでは猛毒で人を死亡させることがある。

　北大西洋西岸や地中海沿岸の浅所にいるミシマオコゼに似たウィーバーフィッシュTrachinus viperaは有名な刺毒魚で、地元のエビ網漁の漁師に恐れられている。この魚は、背びれの数本の棘と鰓蓋(さいがい)の2本の棘に毒腺がある。アイゴ類も背びれと臀びれをあわせて20本前後、腹びれに4本の棘があり、いずれも毒腺がある。

［落合　明・尼岡邦夫］

食中毒

(1)フグ毒　魚毒のなかではもっとも毒性が強く、これの食中毒による死亡者は多い。フグ毒の構造式はC₁₁H₁₇N₃O₈で、炭素環が一つしかなく、グアニジン基と6個のヒドロキシ基、ヘミラクタール基をもつのが特徴で、テトロドトキシンと命名されている。1972年（昭和47）に名古屋大学の後藤俊夫（1929―1990）・岸義人(よしと)（1937―　）らによって天然と同じものが合成された。この結晶は水や有機溶媒に溶けないが、酸性の水に溶け、熱に対して安定していて300℃でも分解しない。中毒症は食後20分から3時間で現れ、知覚麻痺、言語障害、頭痛、腹痛、吐き気、血圧低下、呼吸困難、意識消失ののち数時間で死ぬことがある。

　この毒はフグ類だけでなく、ツムギハゼや両生類のカリフォルニアイモリなどにもある。フグ類ではフグ科Tetraodontidaeのサバフグを除くすべての種類にあって、ハコフグ科やウチワフグ科にはない。日本のものでは、トラフグ、カラス、マフグ、ショウサイフグ、ナシフグなどよく食用にするもののほか、ヒガンフグ、コモンフグ、クサフグ、シマフグなども有毒である。とくに卵巣と肝臓に毒が多く、ついで皮と腸にあるが、血液や筋肉には量的に少なく問題にならない。フグ毒は季節により毒性が変わり、冬から春にわたる産卵期にもっとも強い。また、同種でも個体差が大きいうえ、奄美(あまみ)諸島以南にいるものは毒性が強い。無毒のシロサバフグによく似ているドクサバフグには筋肉にも猛毒があり、クロサバフグには卵巣と肝臓に猛毒があるので、誤って食べるときわめて危険である。

(2)シガテラ毒　シガテラとよばれる毒をもった魚類を食べることによって、下痢、吐き気、温度の異常感覚、関節痛、頭痛を催し、最後に昏睡(こんすい)して死ぬことがある。シガテラという語は、カリブ海に産する巻き貝の1種シガciguaが、神経や消化系に中毒症状をおこすことに由来している。おもに熱帯、亜熱帯のサンゴ礁や岩場にいるフエダイ類、ウツボ類、カマス類、ハタ類、アジ類、ニザダイ類、ブダイ類などがシガテラ毒をもつ可能性がある。筋肉より内臓で毒性が高い。シガテラ毒性は同種でも地域により、また年によって異なるほか、個体差や部位差が著しいのが特徴である。このため予防対策が非常に困難である。その理由の一つとして、食物連鎖を通じての毒物の蓄積が考えられる。つまり、有毒な藻類を食べたサザナミハギなどの草食魚に毒物が移り、ついでこれを食べた肉食魚に移行すると考えられている。

　シガテラとは異なった幻覚をおこす食中毒が、熱帯のボラやヒメジ類など数種で知られている。また、サメ類、イシナギ、マグロ類など大形魚の肝臓にはビタミンAが多く蓄積されるので、これによって頭痛、皮膚の剥(は)がれ、発疹(ほっしん)などがおこることがある。

［落合　明・尼岡邦夫］

皮膚毒

ハコフグ、ウミスズメ、ヨコシマフグ、ヌノサラシ、アゴハタ、ハシナガウバウオ、ミナミウシノシタ、コバンハゼなどは、皮膚の粘液細胞の分泌腺から毒を放出し、同居する魚を短時間で殺してしまう。皮膚毒はグラミスチン、グラミスチン類似性毒で、ハコフグやウミスズメのものはパフトキシンpahutoxinとよばれている。毒には苦味があり、毒性と溶血性とがある。

［落合　明・尼岡邦夫］

『橋本芳郎著『魚貝類の毒』（1977・東京大学出版会）』

アカエイ（生態）

ゴンズイ（生態）

ダルマオコゼ（生態）

オニオコゼ（生態）

ミノカサゴ（生態）

アイゴ（生態）

ハコフグ（生態）

クサフグ（生態）

出典　小学館　日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について　情報 | 凡例

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