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🐈 | Nishikigoi in the pond 2020


Nishikigoi in the pond 2020

If you write the contents roughly
Since parasites such as butterflies and anchor worms occur,
I take medicine on a regular basis.

The Yamakoshi district of Nagaoka City, along with Ojiya City, is the birthplace of Nishikigoi, and it seems that there are many exports to overseas at present.Nishiki in the garden pond ... → Continue reading

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Anchor worm

Anchor worm Lernaea cyprinacea What is L.CopepodsBelongs toArthropodAnd of freshwater fishParasiteOne of.Parasitic on a wide range of fish,碇Live by inserting the shaped head into the body surface of the fish.


Anchor wormcrustaceanAlthough it is a small animal belonging to copepods, it is difficult to find the characteristics of this species in the adult appearance at first glance.Adult females are found parasitizing fish, but their appearance is that there is an anchor at the tip of a long stick.This is an elongated chest, the head itself remains at the tip, and the appendages remain while the other body segments are slightly fused.However, since the body, which was about 1 mm in the previous stage, grows to about 1 cm, each part is very small and difficult to admit.The origin of the name is that the left and right protrusions are formed at the tip of the body, and the appearance of the protrusions being further divided into two at the tip is similar to an anchor, which was named by Matsuda and Kumada in 1928.[1]..The front edge of the body containing such a structure is inserted into the skin of the fish and parasitized.The larvae have a shape that is typical of copepods, and the males mature in that form.

The parasitized fish is engorged with other parts of the fish.microorganismBeing susceptible to infection.Small fish often lose their appetite and die.It often breeds and causes damage to fish farms.


Adult females are rod-shaped with a length of 8 mm and a width of 0.3 mm, and are colorless to pale yellowish green.[2]..From the tip, there is a pair of rod-shaped protrusions on the ventral surface, and from the back, there are protrusions that are larger and the tip is split into two, each extending laterally, and this part looks like an anchor.Most of the rodschestSo, this can be divided into a slightly thin neck in the front and a slightly thick body in the back.A pair of spindle-shaped at the rear endEgg sacThere is.The anterior part of the body 1/3 to 1/4 is inserted into the host body and lives parasitically, and the above-mentioned protrusions on the anterior part of the body function as a sticker.On the rear part of the body that has left the hostdiatom,AomidoroFilamentous algae, likeVorticellaEtc. are often attached, especially in the fall[3].

The macroscopic structure is as described above, and although we cannot see the structure that seems to be an arthropod, let alone copepods, in realityAppendageEtc. are all equipped.This is a femaletransformationThe size of the front is about 1 mm, from which the chest extends to the above size, and then the somites also fuse with each other.In other words, the structure of the appendages is 1 mm in size.headFits small under the protruding front end, which is a sticker, and consists of four nodes.AntennaeThe second antennae, which consist of three nodes, are all filamentous and have needle-like hairs.The head has a smaller spherical maxilla, first and second jaw legs, andCompound eyeAlso remains.There are 4 pairs of thoracic limbs, all of which are bifurcated with 2 primary segments and 3 internal and external limbs with stinging hair.The first pair is immediately after the head protrusion, the second pair is slightly posterior, just behind the part that looks like the head, the third pair is the rear end of the neck, and the fourth pair is near the center of the torso. Remains apart.At the rear end is a two-barreled tail fork.

Life history

The breeding season is May-September, with a suitable temperature of 5-9 ° C.[4]..The posterior egg sac of an adult female contains 150-250 eggs, which hatch in 1-2 days.By the way, it is said that one female lays eggs more than 1 times in her lifetime, and the total number of eggs laid exceeds 10.[5]..The hatched one is 0.14-0.16 mm in lengthNaupliusIs.It becomes the first copepodide larva in 2-4 days after undergoing Methanoplius as the second stage.This is a copepod-like larva with a head-thoracic segment, three thoracic segments, and one abdominal segment, with a pair of long tail spines at the posterior end.The anterior two segments of the thoracic segment have bifurcated appendages.After that, until the 0.7th Copepodide larva, the thoracic segment and appendages are gradually added in almost the same shape.Males and females can be distinguished when the 0.9th Copepodide larva is larvae, and when the XNUMXth Copepodide larva is sexually matured and mated.The size at this time is XNUMX-XNUMX mm in length.After that, the male dies as it is, and the female metamorphoses into an adult figure.

By the wayLife historyIs almost the same as that of the same kind of free life, the only major difference is that the female adult undergoes metamorphosis.[6].

First Copepodide Free life until larval, but after that it requires a host.Larvae from this period crawl around the host's body surface, insert their mouths into their mucous membranes, and suck blood to obtain nutrition.Occasionally they swim away from the body surface and change hosts.The adult female inserts its head into the host body and sticks to it, and does not move.

Overwintering is due to adults, and when the temperature drops, the adults overwinter as they are on the body of the fish.[7]..The lifespan of an individual is about 2 months for females and 3-4 weeks for males, but overwintering individuals reach about 6 months.[8].


The range of hosts is wide,Goldfish,Crucian carp,Koi,Loach,Motsugo,MedakaBesides many freshwater fish,Newt,TadpoleThere are also known examples of parasitism in.In Japan, 18 species from 34 families have been confirmed to be infested with this species (however, including exotic species and captive ones).[9].


Of the worldfreshwaterWidely distributed in the region.It is widely distributed nationwide in Japan, but for some reason there is no record from the Tohoku region.[10].


This species is widely known around the world and was described by Linne.[11]..However, Japanese products were judged to be different species in 1925. L. elegans It has been described as a new species under the name of.This was later synonymous with the same thing.

As for this genus, the following one species and one closely related species are recorded in Japan.

  • Lernaea Anchor worm
    • L. cyprinaea Anchor worm
    • L. parsasiluri Catfish Anchor worm
  • Lamproglena Anchor worm
    • L. chinensis Anchor worm

The Lernaeidae family, including this species, was once included as a parasitic one, but is now placed in the above-mentioned eyes.Most of those belonging to this eye are free-living zooplankton.


Goldfish, carp, eelFish farmMay cause great damage due to mass parasitism[12]..In particular, there is great damage at eel and goldfish farms in Aichi and Shizuoka.[13].

Parasitism by this species is called Anchor worm disease and is one of the oldest known fish diseases.Around the parasitic siteInflammationOrmucusCauses hypersecretion of.Furthermore, in the wound, on the skin and the muscles below itNecrosisCaused by bacteria, fungi, protozoans, etc.Secondary infectionIs also said to cause[14].. It starts breeding at 15 ℃ or higher, repeats 4-5 generations a year, and has strong fertility.

In the case of goldfish, the behavior of rubbing the body against the wall or floor is seen, and the appetite is reduced.May die if the number of parasites increases[15].


Although there are control agents for fisheries, they have no effect on adults and only kill larvae on the body surface of fish or free life, so it is necessary to spray them several times at intervals of about 3 weeks.[16].

To get rid of adults individuallytweezersPull it out with, and then apply the wound medicine.At this time, it is necessary not to leave the tip, and if it breaks in the middleregenerationTo do.Also, in aquarium breeding, regular water changes have the effect of suppressing the breeding of this species.[17].


  1. ^ Suzuki (1965), p.67
  2. ^ The following is described by Okada et al. (1965), p.501.
  3. ^ Suzuki (1965), p.70
  4. ^ This section, Suzuki (1965), p.68-70
  5. ^ Supervised by Hatai and Ogawa (2006), p.124
  6. ^ Otsuka (2006) p.198
  7. ^ Supervised by Hatai and Ogawa (2006), p.124
  8. ^ Nagasawa (2001), p.114
  9. ^ Nagasawa et al. (2007), p.24-25
  10. ^ Nagase et al. (2007), p.26
  11. ^ Nagasawa et al. (2007), including:
  12. ^ Supervised by Ueno (1973) p.435
  13. ^ Izumi (2004) p.83
  14. ^ Supervised by Hatai and Ogawa (2006), p.124
  15. ^ Supervised by Ohno (2005), p.144
  16. ^ Supervised by Hatai and Ogawa (2006), p.124
  17. ^ Supervised by Ohno (2005), p.144


  • Yo Okada et al., "New Japan Animal Picture Book [Middle]", (1967), Kitatakakan of Picture Book
  • Hiroshi Suzuki, "On the Lernaea elegans Leigh-Sharpe, a species of copepod parasitizing the medaka Oryzias latipes (Temminck et Schlegel)", (1), "Study of Crustaceans": The Carcinological Society of Japan.
  • Kazuya Nagasawa et al., "New Host of Anchor Worm in Japan and Catalog of Japanese Anchor Copepods (1915-2007)", (2007): Department of Biosphere, Vol.46. Pp.21-33
  • Isao Otsuka, "Strategy for Copepods and Horizontal Evolution", (2006), Japan Broadcast Publishing Association
  • Kazuya Nagasawa, "Organisms Parasitizing Seafood", (2003), Narishando Bookstore
  • Supervised by Kijio Hatai and Kazuo Ogawa, "New Fish Disease Picture Book", (2006), Midori Shobo
  • Katsuo Izumi, "Fun How to Keep Goody", (2004), Tokyo Bookstore
  • Supervised by Narumi Ohno, "How to Keep and Choose Goldfish", (2005), Seitosha
  • Supervised by Masuzou Ueno, "Japanese Freshwater Biology", (1973), Kitatakakan


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