Genetic Welfare Problems of Companion Animals

Ranchu Goldfish

Excessive Facial Tissue

Outline: Ranchu goldfish develop abnormal tissue growth on their heads as they mature, which breeders refer to as a ‘hood’. This can be several millimetres deep over much of the head such that it protrudes around the eyes, mouth and gills. It can restrict vision very greatly (presumably with effects on feeding and social interactions), may compromise gill movements and the tissue is predisposed to infection.

Summary of Information

(for more information click on the links below)

1. Brief description

Some breeds of goldfish have been bred to develop excessive tissue – called a ‘hood’ - on the head. This may interfere to some extent with vision, breathing and swimming. In addition, such breeds commonly lack a dorsal fin, which also impairs their ability to swim (see also ‘Absent dorsal fin in lionchus).

2. Intensity of welfare impact

Genetic modification of fish by selective breeding can cause major welfare problems (Kolle & Hoffmann 1997). In this case, the welfare effects of the abnormal tissue on the heads of lionchu goldfish depend on its quantity and its proximity to the eyes or gills. The welfare effects are hard to evaluate.

3. Duration of welfare impact

The fish are normal at hatching but develop the abnormal ‘hood’ tissue during maturation, over the course of their first year.

4. Number of animals affected

All fish of this breed are affected to some extent, as the hood is a breed characteristic.

5. Diagnosis

The excessive tissue is obvious.

6. Genetics

The genetic basis of this abnormality has not been investigated.

7. How do you know if an animal is a carrier or likely to become affected?

All fish of this breed are affected to some extent. It is not possible to predict which individuals will become severely affected.

8. Methods and prospects for elimination of the problem

This tissue abnormality could be eliminated by not breeding from fish that show this trait. From the welfare viewpoint, it appears that it would be preferable to select for normal skin.

For further details about this condition, please click on the following:
(these link to items down this page)

• Clinical and pathological effects
• Intensity of welfare impact
• Duration of welfare impact
• Number of animals affected
• Diagnosis
• Genetics
• How do you know if an animal is a carrier or likely to become affected?
• Methods and prospects for elimination of the problem
• Acknowledgements
• References

1. Clinical and pathological effects

Goldfish (Carassius auratus auratus) are a domesticated form of the a common carp of China, the Chinese Crucian carp “Gibelio” (Carassius auratus gibelio) (Komiyama et al 2009). Lionhead goldfish were bred in China and Japan prior to the 17th century to have excessive tissue on the head. The ranchu was derived from the lionhead breed. Both are referred to by breeders as being of a ‘hooded’ type, in which there is an abnormal growth of skin around the head – the ‘hood’. We are not aware of any information on the nature of the abnormal tissue of which the hood is comprised.  It is presumably an abnormality of the skin or perhaps of tissue under the skin. In some fish (examples can be seen on youtube) it is several millimetres thick and covers much or all of the top and sides of the head. Because it protrudes around the eyes, the fish's field of view is extremely restricted in some cases. For example, there may be no downward, upward, or forward vision at all. Vision is severely compromised in these cases and it is highly unlikely that these fish could survive in the wild.

Likewise, in some cases the hood is of a size that restricts gill movements (http://www.aquaticcommunity.com/goldfish/lionhead.php).

The excess flesh that grows on the heads of these fish is prone to infection (http://www.allabout-aquariumfish.com/2008/04/goldfish-varieties-ranchu.html). 

This breed also lacks a dorsal fin, which impairs its ability to swim (see also ‘Absent dorsal fin in ranchus).

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2. Intensity of welfare impact

Genetic modification of fish by selective breeding can cause major welfare problems (Kolle & Hoffmann 1997). In this case, the welfare effects of the abnormal tissue on the heads of lionchu goldfish depend on its quantity and its proximity to the eyes or gills. The welfare effects are hard to evaluate. When the tissue of the hood impairs vision, feeding, social interactions and navigation in the environment may be interfered with. If the growths obstruct the gills, this may compromise the respiratory capacity. How these abnormalities affect quality of life is hard to judge. If the abnormal tissue is traumatised or becomes infected this is likely to cause pain.

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3. Duration of welfare impact

The fish are normal at hatching but develop the abnormal ‘hood’ tissue during maturation, over the course of their first year.

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4. Number of animals affected

All fish of this breed are affected to some extent, as the hood is a breed characteristic.

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5. Diagnosis

The excessive tissue is obvious.

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6. Genetics

The genetic basis of this abnormality has not been investigated.

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7. How do you know if an animal is a carrier or likely to become affected?

It is not possible to predict whether an individual will be severely affected or not.

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8. Methods and prospects for elimination of the problem

This abnormality could be eliminated by not breeding from fish that show this trait. From the welfare viewpoint, it appears that it would be preferable to select for normal skin.

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9. Acknowledgements

UFAW is grateful to Rosie Godfrey BVetMed MRCVS and David Godfrey BVetMed FRCVS for their work in compiling this section.

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10. References

Kolle P and Hoffmann R (1997) Qualzuchten bei Fischen [Excessive breeding in ornamental fish]. Deutsche Tierarztliche Wochenschrif 104: 74-75

Komiyama T, Kobayashi H, Tateno Y, Inoko H, Gojobori T and Ikeo K (2009) An evolutionary origin and selection process of goldfish. Gene 430: 5-11

The following websites giving unreferreed advice about care of goldfish were accessed on 14th September 2011

http://www.allabout-aquariumfish.com/2008/04/goldfish-varieties-ranchu.html

http://www.aquaticcommunity.com/goldfish/lionhead.php

© UFAW 2012

Credit for main photo above:

http://depositphotos.com/25372707/stock-photo-ranchu-lion-head-goldfish-in-fish-tank.html ©Depositphotos.com/Kampee_p