Macrogyrodactylus simentiensis

If miniscule aquarium pianos existed, Macrogyrodactylus simentiensis played underwater concerts. Members of the genus Macrogyrodactylus are among the largest parasitic skin flukes in the world and are found on African fish species. Macrogyrodactylus simentiensis parasitizes the prehistoric dragon fish – Polypterus senegalus. Due to its impressive size, which reaches 1 to 2 mm, Macrogyrodactylus simentiensis can be seen with the naked eye.


Common symptoms observed in fish infected with brooklynella hostilis are:

  • The fish are stressed, get scared when people approach the aquarium or hide and don’t move
  • A transparent thick layer of mucus is visible on the fish
  • Fish scratch against the bottom or decoration in the aquarium
  • In later stages of infection, whitish patches of varying sizes appear on the skin and spots of mucus detach
  • Cloudy eyes
  • On close examination (or with a magnifying glass) worms can be seen, resembling fine hairs 1 to 2 mm long


Treat the aquarium against this parasite immediately if you observe these symptoms on Polypterus senegalus or other Polypterus species. To combat Macrogyrodactylus simentiensis, we recommend eSHa gdex, which is suitable for all aquariums and safe for invertebrates, plants and biofiltration.

What is Macrogyrodactylus simentiensis and how to get rid of it

Macrogyrodactylus simentiensis is one of the five known species of the genus Macrogyrodactylus. Macrogyrodactylus simentiensis is host specific, which means that it has not been found parasitizing other fish besides Polypterus senegalus, not even other polypterus species. However, Macrogyrodactylus simentiensis is not the only Macrogyrodactylus species found on Polypterus senegalus. In total 3 species are found: Macrogyrodactylus simentiensis, Macrogyrodactylus polypterid and Macrogyrodactylus sp.

These Macrogyrodactylus species differ from each other in the structure of the attachment disc and the size of the hooks. The attachment disc of Macrogyrodactylus simentiensis has 2 large Hammuli (central hooks), 14 small hooks in the lower part of the disc, and 2 small hooks in the upper part of the disc, called marginal hook sickles. Macrogyrodactylus simentiensis moves easily along the fish body, like a caterpillar, and can be found on any part of the fish body.

Macrogyrodactylus simentiensis, like other skin flukes, are hermaphroditic and viviparous. With the help of a microscope, you can see the larva develop in the body of the mother. What makes this type of reproduction unique is that up to three subsequent generations can be seen developing in a single worm. If we assume that the parent is the first-generation, then a second-generation larva develops inside it, in which a third-generation larva develops and in which finally a fourth-generation larva develops. In other words, these worms are like a Matryoshka nesting doll with several generations of worms hiding inside.

Fortunately these flukes give birth to live offspring instead of laying eggs, which makes it easier to cope with them than egg-laying flukes. In general one course of eSHa gdex is enough to rid your dragonfish of these parasites and make them healthy again.

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