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Genetic Welfare Problems of Companion Animals
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Celestial Eye Goldfish
Celestial Eye Goldfish
(Choten gan)
Condition: abnormal eye position, blindness and absence of dorsal fin
Related terms: retinal degeneration, Stargazer goldfish
Outline: The eye position of Celestial eye goldfish develops abnormally during the six months from hatching such that the eyes rotate through 90 degrees to end up facing upwards (facing the heavens – hence the fish's name). In association with this, there is degeneration of the retinas – the light sensitive parts of the eyes – resulting in progressive blindness. All fish of this breed are affected but there is some variation in the severity between individuals. It is hard to judge the welfare effects of these conditions but it seems reasonable to suppose that disrupted vision is not consistent with good welfare.
Summary of Information
(for more information click on the links below)
1. Brief description
Celestial eye goldfish are characterised by two anatomical abnormalities that cause significant disability to the fish. The first is that the abnormal orientation/position of their eyes, which are rotated through 90 degrees, so that their vision is directed upwards. Associated with this malposition of the eyes is degeneration of the retina – the layer of the eyes that is sensitive to light and converts it into neurological activity (Matsumura et al 1981, 1982, Sakaue et al 1987). The second feature is lack of a dorsal fin (a fin on the middle of the back). It is the first abnormality that is the primary cause of our concern for welfare in this fish.
2. Intensity of welfare impact
It is difficult to assess the welfare effects of the abnormal eye orientation and lack of dorsal fin but it seems reasonable to propose that these handicaps affect the animals' welfare, as they become blind and have impaired movement, which make activities such as feeding and swimming difficult for these fish (Matsumura et al 1981, 1982, Sakaue et al 1987, Kolle & Hoffmann 1997, http://petcaretips.net/Celestial-eye-goldfish.html).
3. Duration of welfare impact
Celestial eye goldfish do not have the abnormal eye orientation at birth but develop it over the first six months from hatching (Matsumura et al 1981, 1982, Sakaue et al 1987). The absence of a dorsal fin causes severe welfare problems associated with impaired movement from birth. .
4. Number of animals affected
All Celestial eye goldfish are affected.
5. Diagnosis
The abnormal eye position and lack of dorsal fin are clearly apparent.
6. Genetics
The genetic defects that cause the abnormal eye position may be linked to the progressive retinal degeneration and blindness that is seen in this breed, as they occur concurrently; but the genes involved are not known. The genes that cause the absence of the dorsal fin are also unknown but it is likely that they are similar to those that underlie the lack of fin in the bubble-eye goldfish. The absence of the fin and the presence of the eye defects are probably independent of one another, the fin having been lost historically prior to the eye defect arising (Koh 1963, Komiyama et al 2009).
7. How do you know if an animal is a carrier or likely to become affected?
All Celestial eyed goldfish are affected but there is variation among them in the degree of mal-position of the eyes.
8. Methods and prospects for elimination of the problem
For welfare reasons, it seems reasonable to propose that the breed of Celestial-eye goldfish should not be perpetuated. Prospective goldfish owners should avoid purchase of these fish.
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 common carp originating in Eurasia: the Chinese Crucian carp “Gibelio” (Carassius auratus gibelio) (Komiyama et al 2009). Celestial eye goldfish are of a type that seems to have existed for around a hundred years (Koh 1963) but which has grown in popularity in the last 80 years.
They are characterised by two anatomical abnormalities that cause significant disability but which have been maintained by artificial selection and captive care. These features would not exist in wild populations as individuals with such disabilities would fail to survive and would not pass on these genes to subsequent generations. The abnormalities are outlined below.
1. Abnormal eye orientation. In these fish, the eyes do not face sideways as in normal fish, but are rotated through approximately 90 degrees such that their vision is directed upwards. This feature is what gives this breed of fish their name: they are said to be looking up at the stars. The fish, therefore, have abnormal vision with no, or limited, vision in the direction in which they normally swim. Furthermore, associated with this abnormal orientation of the eye is a progressive degeneration of the retina – the light-sensitive tissue of the eyes that converts light to nerve impulses to enable vision. Although the retina is normal in these fish when they hatch, as the orientation of the eyes alters during growth, they progressively lose their eyesight (Matsumura et al 1981, 1982, Sakaue et al 1987).
2. Absence of a dorsal fin (the fin that is normally on the middle of the back). Normal goldfish have a dorsal fin as do other animals adapted to a swimming lifestyle eg whales and dolphins It functions to provide stability in the water and to prevent rolling. Goldfish without dorsal fins have been shown to have slower swimming speeds, slower acceleration, and have to expend greater energy in swimming as affected fish have to cope with rolling and yawing - twisting when trying to go in a straight line (Blake et al 2009).
There are no treatments for these abnormalities. Instead, their impact has to be managed by adapting the fish’s environment (http://petcaretips.net/Celestial-eye-goldfish.html). They have to be housed in environments with slow currents and in which there are no fish that can see and swim normally, as these healthy fish out-compete the Celestials in feeding, resulting in the Celestials being deprived of food and their starvation. Their aquariums also have to be kept free of plants and features that might trap or damage these delicate fish, and the consequence is that they are kept in unstimulating, un-enriched environments.
2. Intensity of welfare impact
Genetic modification by selective breeding of fish can cause major welfare problems (Kolle & Hoffmann 1997). It is difficult to assess the welfare effects of the abnormal eye orientation and lack of dorsal fin but it seems reasonable to propose that these handicaps affect the animals' welfare, as they disrupt vision and impair their movement, which make activities such as feeding and swimming difficult for these fish (Matsumura et al 1981, 1982, Sakaue et al 1987, Kolle & Hoffmann 1997, http://petcaretips.net/Celestial-eye-goldfish.html).
3. Duration of welfare impact
Celestial eye goldfish do not have the abnormal eye orientation at birth but this, and the loss of retinal function, develop over the first six months from hatching (Matsumura et al 1981, 1982, Sakaue et al 1987). The absence of a dorsal fin causes severe welfare problems associated with impaired movement from birth.
4. Number of animals affected
All Celestial eye goldfish are affected. We are unaware of data on the number of these fish kept in the UK or around the world.
5. Diagnosis
The abnormal position of the eyes is readily apparent.
6. Genetics
The same genetic defects that cause the abnormal eye orientation may be linked to the progressive retinal degeneration and blindness that is seen in this breed, as they occur concurrently, but the genes involved have not been determined. The genes that cause the dorsal fin absence are also unknown. It is likely that they are similar to those that cause this condition in the bubble-eye goldfish. The absence of the fin and the eye defects are probably genetically independent of one another, as the absence of the fin occurred historically prior to the eye defect arising (Koh 1963, Komiyama et al 2009).
7. How do you know if an animal is a carrier or likely to become affected?
All Celestial eyed goldfish are affected but there is variation among them in the degree of mal-position of the eyes.
8. Methods and prospects for elimination of the problem
For welfare reasons, it seems reasonable to suggest that the breed of Celestial-eye goldfish should not be perpetuated. Prospective goldfish owners should avoid purchase of these fish.
9. Acknowledgements
UFAW is grateful to Rosie Godfrey BVetMed MRCVS and David Godfrey BVetMed FRCVS for their work in compiling this section.
10. References
Blake RW, Li J and Chan KHS (2009) Swimming in four goldfish Carassius auratus morphotypes: understanding functional design and performance employing artificially selected forms. Journal of Fish Biology 75: 591–617
Koh T-P (1963) Morphological change and evolution of carps under cultivation. Journal of National Taiwan Normal University 8: 193-204
Kolle P and Hoffmann R (1997) Qualzuchten bei Fischen [Excessive breeding in ornamental fish]. Deutsche Tierarztliche Wochenschrift 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
Matsumura M, Ohkuma M and Honda Y (1981) Electron microscopic studies on Celestial goldfish retina - a possible new type of retinal degeneration in experimental animals Experimental Eye Research 32: 649-656
Matsumura M, Ohkuma M and Honda Y (1982) Retinal Degeneration in Celestial Goldfish
Developmental Study. Ophthalmic Research 14: 344-353
Sakaue H, Negi A, Matsumura M, Ohkuma M and Honda Y (1987) Electrophysiological studies of spontaneous retinal degeneration in Celestial goldfish (chotengan). Japanese Journal of Ophthalmology 31: 109-13
http://petcaretips.net/Celestial-eye-goldfish.html accessed 29.8.101
© UFAW 2011
Credit for main photo above:
http://commons.wikimedia.org/wiki/File%3ACelestial_eye_goldfish.jpg
By JasonMarini (Own work) [Public domain], via Wikimedia Commons
