Discus fish (Kings of the Aquarium) are dazzling freshwater fish prized for their vibrant colors and round, flattened bodies. Native to the Amazon basin, these calm creatures are popular aquarium additions, but require specific care due to their sensitivity to water conditions .
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2. CONTENTS
1. Introduction
2. Taxonomy
3. Species of Discus
4. Distribution
5. Morphology
6. Meristic Characters
7. Fin Formula
8. Habitat & Feeding
9. Discus Breeding
10. Behavior of Discus
11. Importance
12. Interesting Facts
13. Recent Researches
14. References
3. INTRODUCTION
Discus fish (Kings of the Aquarium) are dazzling
freshwater fish prized for their vibrant colors and
round, flattened bodies. Native to the Amazon basin,
these calm creatures are popular aquarium additions,
but require specific care due to their sensitivity to
water conditions (Crampton, 2020).
5. SPECIES OF DISCUS
A genetic study of discus confirms that there are three
distinct species under the genus.
1. Blue Discus: Eastern Amazon, blue & brown body.
2. Green Discus: Western Amazon, yellow-green with
blue & black markings.
3. Red Discus (Heckel): Rio Negro, bright red-orange,
possible blue & black accents (
6. DISTRIBUTION
• Amazon River basin (South America)
• Prefer slow-moving blackwater
tributaries
• Found in areas with flooded forests
and vegetation (Crampton, 2020).
7. MORPHOLOGY
Body Shape: Laterally compressed, round body shape, giving
them "discus" appearance.
Scales: Small and Cycloid (smooth-edged).
Fins: Discus have long, flowing fins, including dorsal (top), anal
(rear), pectoral (paired side fins), and caudal (tail) fins.
Mouth: Small mouth on the underside for bottom feeding
(Admin, 2023).
8.
9. MERISTIC CHARACTERS
•Feeding: Omnivorous
•Migration: Non- migratory
•Growth rate: 1.5 to 1 inch per month (can grow upto 8
inches)
•Life Span: Average of 10 years
•Weight: 150-250g
•Natural predators: Turtles, Birds and Larger Species of
Fish
•Fin formula: D(12-14)A(5-9)P(12-14)V(5-7)C(13-16)
(Hall, 2023).
10. HABITAT AND FEEDING
• Algae growing on surfaces
• Plant matter
• Insects or debris falling into
the water
FEEDING
• Amazon River tributaries
(South America)
• Still or slow-moving [4].
HABITAT
11. DISCUS BREEDING
Discus are egg layers requiring warm water
Breeding seasons are summer and spring
Requires separate breeding tank
Parents become fiercely protective, cleaning and
fanning eggs until they hatch after 2-3 days.
Fry initially feed on a special mucus secretion
from the parents' skin for several days before
becoming free-swimming (Bearly, 2020).
12. BEHAVIOR OF DISCUS
•Discus fish stay put (non-migratory) in their territory.
•Generally peaceful, but can show aggression
(especially during dominance fights or breeding).
•Devoted parents: clean, guard eggs, and care for fry
until they can swim on their own (Admin, 2023).
13. Importance of Discus Fish:
Ornamental Aquaculture:
Discus fish are prized freshwater
aquarium fish, admired for their:
• Unique body shape (flat & round)
• Vibrant colors & patterns
• Peaceful temperament
Economic Value:
• Multi-million dollar industry
• Breeding in Asia (esp. Thailand)
• Selective breeding for colors & strains
• Discus shows, competitions & online
communities drive economic value.
Ecological Role (in the wild):
• Role in food chain (prey & predator)
• Consume algae & detritus
Scientific Importance:
• Unique parental care behavior (mucus
for fry)
• Offers insights into fish reproduction
(Hall, 2023).
14. INTERESTING FACTS ABOUT DISCUS
Nicknamed "Kings of the Aquarium"
for their beauty and demanding care.
Selective breeding created many
colors.
Discus can change color: darker
under stress, brighter when breeding
or scared.
Discus carefully choose their
lifelong partner.
Discus are social fish and must be
kept in groups.
Despite being cichlids, discus are
peaceful
Discus prefer darker environments
but still need some daily sunlight.
Discus are intelligent, can recognize
their owner, and can be hand-fed.
Discus parents are monogamous and
very caring, feeding their young a
special mucus.
The Red Turquoise Discus is the
most expensive, reaching $550
(Admin, 2023).
15. RECENT RESEARCH FINDINGS (2021-
2024)
1. Identifying Genes for Parental Care in Discus Fish: A
Brain Transcriptome Approach
2. Characterizing amoebic diseases in discus fish: Molecular
and pathological analysis
3. Astaxanthin: Friend or Foe to Colorful Discus?
4. The Secrets of Discus Fish Parenting: Unveiling their
Immune Arsenal
5. Lipidomics Reveals Sex-Specific Mucus Alterations in
Parental Discus Fish
16. 1. Astaxanthin: Friend or Foe to Colorful
Discus?
• Microplastics harm discus fish by causing oxidative
stress, leading to duller coloration.
• Astaxanthin acts as an antioxidant, mitigating this
stress and protecting discus health.
• However, astaxanthin can also slightly reduce the
vibrancy of discus colors, creating a trade-off (Huang
et al., 2023).
17. 2. The Secrets of Discus Fish Parenting:
Unveiling their Immune Arsenal
• Discus fish feed their young a special mucus with immune
system components (CTLs) to fight germs.
• Researchers identified 186 different CTL genes in discus fish.
• They studied how these genes work and how much CTL is
produced during different stages of parenting.
• This suggests CTLs might change based on the stage and parent
(male/female).
• This research helps understand how discus fish protect their
young with their immune system (Ma, T. et al., 2024).
18. 3. Characterizing amoebic diseases in discus
fish: Molecular and pathological analysis
• Sick discus fish from farms were studied for amoeba.
• Skin, gills, and intestines were checked.
• A harmful amoeba (Acanthamoeba T4) was found on skin
and gills.
• Damaged gills and amoeba cysts suggest amoeba infection.
• This amoeba can infect humans.
• More study needed on discus fish as a potential infection
source for humans (Rahmati-Holasoo et al., 2024).
19. 4. Lipidomics Reveals Sex-Specific Mucus
Alterations in Parental Discus Fish
• Discus fish feed their young with special skin mucus.
• This mucus changes depending on if the fish are parents.
• Females' mucus changes more, with some fats increasing during
parenting.
• Males' mucus changes too, but less than females.
• Even when caring for fry, parents have different mucus fat mixes
based on sex.
• This suggests discus fish adjust their mucus for optimal fry
nutrition (Zhao et al., 2024).
20. Discus Fish Mucus Composition
Component Function Changes During Parental Care
Proteins Energy Provision
Levels of some proteins
increase
Lipids (Fats) Nutritional value for fry
Composition changes based on
sex and parental status
Sugar-binding protein
Protects parents & fry from
bacterial infections
Function likely remains
constant
Immunoglobulins (IgM) Protects fry
Levels increase after eggs are
laid
C-type lectins (CTLs) Fights germs and protects fry
Specific type might change
based on parenting stage and
parent's sex
Vitamins & Minerals Essential for fry development
Influenced by the discus fish's
diet
21. 5. IDENTIFYING GENES FOR PARENTAL CARE IN
DISCUS FISH: A BRAIN TRANSCRIPTOME APPROACH
• Unlike most fish, discus parents are super involved!
• After hatching, discus fry eat a nutritious mucus from their parents' skin,
like fish "milk".
• Scientists studied discus fish brains and found genes linked to this
behavior.
• Genes like LAPTM and FOXB might be important for discus "milk"
production.
• Study suggests hormones, inflammation response, and nerve signals play
a role too.
• This research helps us understand how discus fish care for their young in
such a unique way (Wei et al., 2021).
22. REFERENCES
1. Admin. (2023, July 4). All you need to know about Discus Fish. Intan.
https://intanaquariumfeeds.com/all- you-need-to-know-about-discus-fish/
2. Bearly, I. (2020, March 30). Care Guide for Discus Fish – the King of the Aquarium.
Aquarium Co-Op. https://www.aquariumcoop.com/blogs/aquarium/discus-care-guide
3. Crampton, W. G. (2020). Ecology and life history of an Amazon floodplain cichlid: the
discus fish Symphysodon (Perciformes: Cichlidae). Neotropical Ichthyology, 6, 599-612.
4. Discus Fish Feeding & Nutrition. (2019, July 31). Myrtle Beach Discus.
https://myrtlebeachdiscus.com/blogs/news/discus-fish-feeding-
nutrition#:~:text=Some%20of%20the%20best%20sources,and%2For%20freeze%2Ddried.
5. Farias, I. P., & Hrbek, T. (2021). Patterns of diversification in the discus fishes
(Symphysodon spp. Cichlidae) of the Amazon basin. Molecular phylogenetics and
evolution, 49(1), 32-43.
6. Hall, H. (2023, March 30). Discus. A-Z Animals. https://a-z-animals.com/animals/discus/
7. Huang, J. N., Wen, B., Li, X. X., Xu, L., Gao, J. Z., & Chen, Z. Z. (2023). Astaxanthin
mitigates oxidative stress caused by microplastics at the expense of reduced skin
pigmentation in discus fish. Science of The Total Environment, 874, 162494.
23. 8. Ma, T. F., Huang, J. N., Wen, B., Gao, J. Z., & Chen, Z. Z. (2024). Genome-wide
identification and expression analysis of C-type lectins in discus fish (Symphysodon
aequifasciatus) during parental care. Fish & Shellfish Immunology, 144, 109291.
9. Rahmati-Holasoo, H., Niyyati, M., Fatemi, M., Mahdavi Abhari, F., Shokrpoor, S.,
Nassiri, A., & Marandi, A. (2024). Molecular identification, phylogenetic analysis and
histopathological study of pathogenic free-living amoebae isolated from discus fish
(Symphysodon aequifasciatus) in Iran: 2020–2022. BMC Veterinary Research, 20(1),
54.
10. Stauffer, J. R. (2020, June 19). Why So Few Discus Species, and How Did They Arise?
TFH Magazine. https://www.tfhmagazine.com/articles/freshwater/why-so-few-discus-
species-and-how-did-they-arise
11. Wei, Y. L., Wen, B., Gao, J. Z., & Chen, Z. Z. (2021). Brain transcriptome analysis
reveals genes involved in parental care behaviour in discus fish (Symphysodon
haraldi). General and Comparative Endocrinology, 309, 113793.
12. Zhao, S., Wen, B., Liang, H., Gao, J., & Chen, Z. (2024). Sex-Dependent Lipid Profile
Differences in Skin Mucus between Non-Parental and Parental Discus Fish
(Symphysodon haraldi) Determined by Lipidomics. Fishes, 9(1), 27.
