Fish-Killing Nudibranch

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Phyllidia varicosa - Lamarck, 1801
Fish-Killing Nudibranch

This colorful nudibranch can poison an entire reef tank. Scott W. Michael

[edit] Overview

This visually striking species is one of the most lethal animals commonly encountered in reef tanks because it manufactures a chemical that is very poisonous to fishes.

The color pattern consists of a light blue, white, or black background with starkly contrasting lines, circles or ovals of black, white, or yellow. It lacks the dorsal tuft of gills around the anus.

It is one of the larger nudibranchs (up to 4.5 inches - 11.5 cm), as well as one that this widespread and common in the wild. It therefore makes its way into the aquarium trade, where it is often sold and bought in ignorance.

In nature, if a fish bites a Phyllidia, the slug will probably be spat out with little consequence to either party: a little of this chemical in the slime coat deters predation. In a reef aquarium, when the nudibranch dies of starvation (because there is never sufficient live sponge prey), the poison will affect the entire tank.

Family: Phyllidiidae

Other common name(s):

  • Scrambled Egg Nudibranch
  • Varicose Nudibranch
  • Varicose Sea Slug

Native range:

Habitat: It is found crawling in open areas on smooth, hard-substrate surfaces, on patch reefs and reef slopes.

Maximum length: 11.5 cm (5 in)

Minimum aquarium size: 38 L (10 gal)

Water: Marine 24 °C (297 K, 75 °F) - 28 °C (301 K, 82 °F)

General swimming level: Bottom.

[edit] Feeding

Predator on sponges. Phyllidid nudibranchs secrete digestive enzymes onto the sponge and then ingest the tissue as it starts to breakdown.

[edit] Aquarium Compatibility

Not suitable for reef aquariums, where it will starve and may poison the whole system.

[edit] Special Care

DO NOT buy these animals, unless you intend to provide them with a special system and provide them with appropriate food and care.

[edit] Notes

This event has caused numerous fish kills.

The bottom line: phyllidiids should not be kept.

Reference: A PocketExpert Guide to Marine Invertebrates
Image credit: SWM
Text credit: RLS
Facts about Fish-Killing NudibranchRDF feed
Common name Fish-Killing Nudibranch  +, Scrambled Egg Nudibranch  +, Varicose Nudibranch  +, and Varicose Sea Slug  +
Family Phyllidiidae  +
Genus Phyllidia  +
Image credit SWM  +
Maximum length 5 in  +
Minimum aquarium size 10 gal  +
Native range Indo-Pacific  +, Red Sea  +, East Africa  +, South Africa  +, Papua New Guinea  +, Australia  +, Southern Japan  +, and Society Islands  +
Reference A PocketExpert Guide to Marine Invertebrates  +
Specific name varicosa  +
Swimming level Bottom.  +
Text credit RLS  +
Water max temp 301 K (28 °C, 82 °F)  +
Water min temp 297 K (24 °C, 75 °F)  +
Water type Marine  +