Zebrafish (Danio rerio) are small shoaling cyprinid fish. Although details of the distribution are unclear, D. rerio may be widely distributed in shallow, slow-flowing waters on the Indian subcontinent. They are most commonly encountered in shallow ponds and standing water bodies, often connected to rice cultivation. Where they are found, they tend to be among the most abundant fish species. (Spence et al. 2008 and references therein)

Danio rerio are omnivorous, feeding primarily on zooplankton and insects, although phytoplankton, filamentous algae and vascular plant material, spores and invertebrate eggs, fish scales, arachnids, detritus, sand, and mud have also been reported from gut content analyses (Spence et al. 2008 and references therein).

For many decades, D. rerio has been both a very popular aquarium fish and an important research model in several fields of biology (notably, developmental biology and toxicology). The development of D. rerio as a model organism for modern biological investigation began with the pioneering work of George Streisinger and colleagues at the University of Oregon (Streisinger et al. 1981; Briggs 2002), who recognized many of the virtues of D. rerio for research. Streisinger developed methods to produce homozygous strains by using genetically inactivated sperm, performed the first mutagenesis studies, and established that complementation methods (in which heterozygous mutant fish are paired) could be used to assign mutations to genetic complementation groups. Subsequently, the use and importance of D. rerio in biological research has exploded and diversified to the point that these fish are extremely important vertebrate models in an extraordinary array of research fields (see review by Runkwitz et al. 2011; Vascotto et al. 1997).

A number of features make D. rerio tractable for experimental manipulation. It is a small, robust fish, so large numbers can be kept easily and cheaply in the laboratory, where it breeds all year round. Females can spawn every 2 to 3 days and a single clutch may contain several hundred eggs. Generation time is short (for a vertebrate), typically 3 to 4 months, making it suitable for selection experiments. Danio rerio eggs are large relative to other fish (0.7 mm in diameter at fertilization) and optically transparent, the yolk being sequestered into a separate cell. Furthermore, fertilization is external so live embryos are accessible to manipulation and can be monitored through all developmental stages under a dissecting microscope. Development is rapid, with precursors to all major organs developing within 36 hours, and larvae display food-seeking and active avoidance behaviors within five days after fertilization, i.e., 2 to 3 days after hatching. Mutagenesis screens have now generated many thousands of mutations and have led to the identification of hundreds of genes controlling vertebrate development (Rinkwitz et al. 2011 report that as of their writing there was information on embryonic and larval expression of over 12,000 genes and just under 1000 mutant phenotypes). (Spence et al. 2008 and references therein) The D. rerio genome has now been largely sequenced (see http://www.sanger.ac.uk/Projects/D_rerio/), making it an even more valuable research organism. Although D. rerio is extremely well studied as a lab organism, the ecology and behavior of these fish in the wild has been far less well studied.

Adults inhabit streams, canals, ditches, ponds and beels (Ref. 1479). Occur in slow-moving to stagnant standing water bodies, particularly rice-fields (Ref. 4832); and lower reaches of streams (Ref. 58912). Common in rivulets at foot hills (Ref. 41236). Feed on worms and small crustaceans (Ref. 7020); also on insect larvae. Breed all year round (Ref. 58913). Appears to be primarily an annual species in the wild, the spawning season starting just before the onset of the monsoon (Ref. 72224). Domesticated zebrafish live on average 3.5 years, with oldest individuals surviving up to 5.5 years (Ref. 58923). Spawning is induced by temperature and commences at the onset of the monsoon season (Ref. 58913). Food availability also acts as cue for breeding (Ref. 58913). Growth rate is a vital guiding environmental factor for sexual differentiation for this species as observed in a study (Ref. 58948). In this same study, frequency and amount of food prior to and throughout gonadal differentiation period resulted in more individuals differentiating to become females and is more pronounced in hybrid than pure bred groups (Ref. 58948). Often used for mosquito control (Ref 6351). Popular for aquarium purposes (Ref. 44325). Used as a model system (=organism) for developmental biology (Ref. 47810). Aquarium keeping: in groups of 5 or more individuals; minimum aquarium size 60 cm (Ref. 51539).

Zebrafish (Danio rerio) are small shoaling cyprinid fish native to the flood plains of the Indian subcontinent. The natural range of D. rerio is centered around the Ganges and Brahmaputra river basins in north-eastern India, Bangladesh, and Nepal, although in the past specimens have also been collected in the Indus, Cauvery, Pennar, Godavari, and Mahanadi river basins. There are also reports of occurrences from the Krishna river basin and the states of Rajasthan, Gujarat, and Andra Pradesh (river basins draining into the Arabian Sea) as well as northern Myanmar and Sri Lanka, but locality details are lacking. Although details of the distribution are unclear, D. rerio may be widely distributed in shallow, slow-flowing waters on the Indian subcontinent. Based on results from several studies, D. rerio occur in shallow water bodies with visibility to a depth of approximately 30 cm, frequently in unshaded locations with aquatic vegetation and a silty substratum. They are most commonly encountered in shallow ponds and standing water bodies, often connected to rice cultivation. Where they are found, they tend to be among the most abundant fish species. (Spence et al. 2008 and references therein)

Danio rerio are omnivorous, feeding primarily on zooplankton and insects, although phytoplankton, filamentous algae and vascular plant material, spores and invertebrate eggs, fish scales, arachnids, detritus, sand, and mud have also been reported from gut content analyses (Spence et al. 2008 and references therein).

The ‘‘leopard’’ danio, which displays a spotted color pattern rather than stripes, was originally thought to be a separate species, described as Brachydanio frankei (at one time, small Danio species with short dorsal fins and a reduced lateral line, including the species now known as Danio rerio, were segregated from the larger Danio species and placed in Brachydanio). However, neither molecular nor morphological analyses have differentiated between the two forms and hybrids have been shown to produce fertile progeny. The leopard danio is now known to be a spontaneous mutation of the wild-type D. rerio color pattern, with homozygotes displaying a spotted pattern and heterozygotes having a disrupted stripe pattern. Another aquarium variant is the ‘‘longfin’’ D. rerio, which is a dominant mutation resulting in elongated fins. The commonly used wild-type strain, TL (Tübingen long-fin) displays both the ‘‘leopard’’ and ‘‘longfin’’ mutations. (Spence et al. 2008 and references therein)

For many decades, D. rerio has been both a very popular aquarium fish and an important research model in several fields of biology (notably, toxicology and developmental biology; see, e.g., Creaser 1934). The development of D. rerio as a model organism for modern biological investigation began with the pioneering work of George Streisinger and colleagues at the University of Oregon (Streisinger et al. 1981; Briggs 2002), who recognized many of the virtues of D. rerio for research. Streisinger developed methods to produce homozygous strains by using genetically inactivated sperm, performed the first mutagenesis studies, and established that complementation methods (in which heterozygous mutant fish are paired) could be used to assign mutations to genetic complementation groups. Subsequently, the use and importance of D. rerio in biological research has exploded and diversified to the point that these fish are extremely important vertebrate models in an extraordinary array of research fields (see review by Runkwitz et al. 2011; Vascotto et al. 1997).

A number of features make D. rerio tractable for experimental manipulation. It is a small, robust fish, so large numbers can be kept easily and cheaply in the laboratory, where it breeds all year round. Females can spawn every 2 to 3 days and a single clutch may contain several hundred eggs. Generation time is short (for a vertebrate), typically 3 to 4 months, making it suitable for selection experiments. Danio rerio eggs are large relative to other fish (0.7 mm in diameter at fertilization) and optically transparent, the yolk being sequestered into a separate cell. Furthermore, fertilization is external so live embryos are accessible to manipulation and can be monitored through all developmental stages under a dissecting microscope. Development is rapid, with precursors to all major organs developing within 36 hours, and larvae display food seeking and active avoidance behaviors within five days after fertilization, i.e. 2 to 3 days after hatching. The large-scale random mutagenesis screens of D. rerio were the first to be conducted in a vertebrate. Danio rerio used for mutagenesis and screening are from lines that have been inbred for many generations in order to maintain a stable genetic background. Mutagenesis screens have now generated many thousands of mutations and have led to the identification of hundreds of genes controlling vertebrate development (Rinkwitz et al. 2011 report that as of their writing there was information on embryonic and larval expression of over 12,000 genes and just under 1000 mutant phenotypes). As a vertebrate, D. rerio has special value as a model of human disease and for the screening of therapeutic drugs (Chakraborty et al. 2009) and is often more tractable for genetic and embryological manipulation and cost effective than other vertebrate models such as mice. Hundreds of labs around the world now routinely use D. rerio in both basic and applied research, leading to the creation of a centralized online resource for this research community (http://zfin.org). Some researchers have even used D. rerio to investigate the genetic basis of vertebrate behavior (see, e.g., Miklósi and Andrew 2006; Norton and Bally-Cuif 2010). (Spence et al. 2008 and references therein) The D. rerio genome has now been largely sequenced (see http://www.sanger.ac.uk/Projects/D_rerio/), making it an even more valuable research organism.

Laale (1977) reviewed the D. rerio literature to date, with a focus on physiology. Wixon (2000) provides an overview of the current state of knowledge and resources for the study of D. rerio. Although D. rerio is extremely well studied as a lab organism, the ecology and behavior of these fish in the wild has been far less well studied. Spence et al. (2008) reviewed the ecology and behavior of D. rerio (see also McClure et al. 2006; Spence et al. 2006; Engeszer et al. 2007), as well as its taxonomic history, morphology, and many other aspects of its biology.

Asia: India, Nepal and Bangladesh; introduced elsewhere.

Asia: Pakistan, India, Bangladesh, Nepal and Myanmar (Ref. 41236). Reported from Bhutan (Ref. 40882). Appearance in Colombian waters presumably by escape from an aquarium fish rearing facility (Ref. 1739).

Danio rerio is a widely distributed species, known througout India to Nepal in the north and from Sutlej River in the west and in the east in West Bengal and Arunachal Pradesh.

Danio rerio is native to inland streams and rivers of India. Its has a broad geographic range in the Indian subcontinent, ranging from the Ganges and Brahmaputra river basins of Bangladesh, India, and Nepal. A few introduced populations of the species inhabit inland waters in the United States (California, Connecticut, Florida and New Mexico) and Columbia, South America.

Biogeographic Regions: nearctic (Introduced ); palearctic (Native ); oriental (Native ); neotropical (Introduced )

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Exotic

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Native to eastern Asia (Pakistan, India, Bangladesh, and Nepal (Fuller et al. 1999). Introduced and established in McCauley Spring, Sandoval County, New Mexico; reported from Florida, California, and Connecticut (Fuller et al. 1999).

Vertebrae: 31 - 32

Zebrafish have fusiform, laterally compressed bodies that reach an average length of 25 mm. The largest recorded zebrafish reached 64 mm in captivity. They have centrally located eyes and thin elongate mandibles with a protrusive lower jaw that causes the mouth to point upwards. Like other cyprinids, zebrafish are stomachless and toothless. As a result, they rely on gill rakers to break up food. Additionally, they are obligate suction feeders. Zebrafish have several defining features including an incomplete lateral line, two pairs of barbels, and several (usually 5 to 7) longitudinal stripes along the sides of their body. The degree of sexual dimorphism in zebrafish is minimal, as males tend to have more yellow coloration and tend to have larger anal fins than females.

Range length: 64 (in captivity) (high) mm.

Average length: 25 mm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: male more colorful; sexes shaped differently

Maximum size: 60 mm ---

3.8 cm SL (male/unsexed; (Ref. 41236))

Five uniformly, pigmented, horizontal stripes on the side of the body, all extending onto the end of caudal fin rays. Anal fin distinctively striped. Lateral line absent. Rostral barbels extend to anterior margin of orbit; maxillary barbels end at about middle of opercle. Branched anal fin rays 10-12. Vertebrae 31-32.

benthopelagic; freshwater; pH range: 6.0 - 8.0; dH range: 5 - 19

Habitat and Ecology

Systems

• Freshwater

Zebrafish live in freshwater streams and rivers but are more often considered floodplain species. They are most often found in shallow, slow-moving water near the edge of streams or in ditches. Because of monsoon season in their native geographic range, zebrafish have adapted to a broad range of temperatures, from 6 degrees C during winter to 38 degrees C in summer. Rice cultivation by humans has had a significant impact on zebrafish habitat. Rice farming requires damming of waterways and creation of irrigation systems. Since rice farming is common in India, many natural habitats of zebrafish have been dramatically altered by damming and irrigation. Fortunately, zebrafish are relatively tolerant of human disturbance and are able to survive and reproduce well in altered habitats.

Habitat Regions: temperate ; tropical ; freshwater

Aquatic Biomes: rivers and streams

Other Habitat Features: agricultural

Habitat Type: Freshwater

Comments: Known from canals in California and Florida, from a spring in New Mexico, and from streams in Connecticut; these fishes probably came from fish farms or aquarium releases (Fuller et al. 1999).

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Inhabits streams, canals, ditches, ponds and beels (Ref. 1479). Occurs in slow-moving to stagnant standing water bodies, particularly rice-fields (Ref. 4832, 58912). Water highly transparent (Ref. 58912). Feeds on worms and small crustaceans (Ref. 7020); also on insect larvae and can be used for mosquito control (Ref 6351).

Zebrafish are omnivores. They get most of their food from the water column, mainly eating zooplankton and aquatic insects. Zebrafish also surface feed, eating terrestrial insects and arachnids. Zebrafish commonly eat mosquito larvae.

Animal Foods: eggs; insects; terrestrial non-insect arthropods; zooplankton

Plant Foods: algae; phytoplankton

Foraging Behavior: filter-feeding

Primary Diet: omnivore ; planktivore

Zebrafish consume a number of insect species, including mosquito larvae. As a result, they likely help control insect pests throughout their geographic range. In addition, zebrafish are prey for a number of different piscivorous fish and bird species. There is no information available regarding parasites of this species.

The main predators of zebrafish are snakeheads and freshwater garfish. Other predators include catfish, knifefish, spiny eels, Indian pond heron, and common kingfisher. Zebrafish show alarm in response to visual and olfactory predatorial cues. Anti-predator behavior is also triggered by injury pheromones. Alarm behaviors include increased agitation, aggression, and decreased feeding rates. Zebrafish have three pigment cell types that contribute to their stripes. One of the pigment cells, dark blue melanophores, can be altered in response to stimuli. This is believed to help zebrafish evade potential predators.

Known Predators:

• snakeheads Channa
• freshwater garfish Xenentodon cancila
• catfish Mystus bleekeri
• knifefish Notopterus notopterus
• spiny eels Mastacembelids
• Indian Pond heron Ardeola grayii
• common kingfisher Alcedo atthis

Anti-predator Adaptations: cryptic

Plistophora Disease in neon fish. Parasitic infestations (protozoa, worms, etc.)

Ichthyobodo Infection. Parasitic infestations (protozoa, worms, etc.)

Bacterial Infections (general). Bacterial diseases

Olfaction, vision, and motion detection via the lateral line system help zebrafish perceive their local environment and evade potential predators. Movement in the surrounding water is detected by the lateral line, which can detect small changes in pressure in the immediate environment. Zebrafish respond to a broad range of chemical cues detected by the olfactory bulb. Olfaction is particularly important for reproduction in zebrafish. Female zebrafish must come in contact with male gonadal pheromones in order to ovulate. Meanwhile, male zebrafish must come in contact with female pheromones in order to initiate spawning behavior.

Communication Channels: chemical

Other Communication Modes: pheromones

Perception Channels: visual ; acoustic

Breed all year round (Ref. 58931). From Johnson (1932), 'a female never extrudes eggs during active courtship until the genital organ comes in contact with that of the male, whereupon a small stream of eggs is ejected' (Ref. 205). Violent dashing and chasing characterise courtship finally culminating in eggs being shed a few at a time, settling freely without adhering to the bottom surface (Ref. 205).

Immediately after hatching, all zebrafish develop into females. Once they become five to seven weeks old, gonadal differentiation begin to occur, Males take approximately 3 months to fully develop their testes. Sex determination is not fully understood; however, evidence suggests that food supply and growth rates play a key role in sex determination as slow-growing individuals become males and fast-growing individuals become females.

In the wild, most zebrafish live to be one year old. In captivity, zebrafish have a mean lifespan of 42 months. The maximum age observed in captivity was 66 months. Captive zebrafish develop spinal curvature after their second year, which is not observed in natural populations.

Range lifespan

Status: captivity: 66 (high) months.

Average lifespan

Status: wild: 1 years.

Average lifespan

Status: captivity: 42 months.

Maximum longevity: 5.5 years (captivity) Observations: Outbred zebrafish have a mean lifespan of 3.5 years and can live up to 5.5 years. They exhibit a gradual ageing process. A spinal curvature was reported to be a common age-related phenotype (Gerhard et al. 2002). The zebrafish heart appears to have a robust capacity for regeneration based on the proliferation of cardiomyocytes which can avoid scar formation and allow cardiac regeneration (Poss et al. 2002).

Zebrafish are promiscuous and breed seasonally during monsoon season. Mating behavior is also heavily influenced by photoperiod, as spawning begins immediately at first light during breeding season and continues for about an hour. In order to initiate courtship about 3 to 7 males chase females and try to lead female towards a spawning site by nudging her and/or swimming around her in a tight circle or figure eight. Spawning sites consists of bare substrate that tends to be well vegetated. In captivity, gravel spawning sites are preferred to silt spawning sites. In the wild, zebrafish breed in silt-bottomed habitats. When a breeding pair reaches the spawning site, the male aligns his genital pore with the female's and begins to quiver, which causes the female to release her eggs and the male to release his sperm. The female releases 5 to 20 eggs at a time. This cycle repeats for about an hour. While the presence of female pheromones is required for initiation of courtship behavior in the male, male gonadal pheromones are required by the female for ovulation to occur. There is limited evidence for male-male competition and female mate preference.

Mating System: polygynandrous (promiscuous)

Zebrafish breed seasonally during the monsoons, which occur from April to August. Spawning has also been recorded outside wet season, suggesting that breeding may be seasonal as a result of food availability. They tend to breed in silt-bottomed and well vegetated pools. Zebrafish lay non-adhesive eggs without preparing a nest, and are considered to be group spawners and egg scatterers. Although time to hatching depends on water temperature, most eggs hatch between 48 and 72 hours after fertilization. Chorion thickness and embryo activity also impact incubation time. Zebrafish are approximately 3 mm upon hatching and are immediately independent. They are able to swim, feed, and exhibit active avoidance behaviors within 72 hours of fertilization.

Breeding interval: Zebrafish spawn every 1 to 6 days during spawning season, which occurs once yearly..

Breeding season: Zebrafish spawn during monsoon season, from April to August

Range number of offspring: 1 to 700 .

Average number of offspring: 185.

Range time to hatching: 48 to 72 hours.

Average time to independence: 0 minutes.

Key Reproductive Features: iteroparous ; seasonal breeding ; sequential hermaphrodite (Protogynous ); sexual ; induced ovulation ; fertilization (External ); broadcast (group) spawning; oviparous

Adult zebrafish provide no parental care to young. Zebrafish are independent immediately upon hatching.

Parental Investment: no parental involvement

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There are 4 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.


Download FASTA File

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 20
Specimens with Barcodes: 35
Species With Barcodes: 1

Zebrafish have a broad geographic range and are locally abundant. They breed easily in their native habitat and in 2007, increasing catch rates suggested increasing abundance. Other than potential over exploitation for the aquaria trade, there are no known threats to the long-term persistence of this species. Zebrafish are classified as a species of least concern on the IUCN's Red List of Threatened Species.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

United States

Rounded National Status Rank: NNA - Not Applicable

Rounded Global Status Rank: G5 - Secure

Population

Population Trend

Least Concern (LC)

Major Threats

Conservation Actions

fisheries: of no interest; aquarium: highly commercial

There are no known adverse effects of Danio rerio on humans

In 1981, George Streisinger and his colleagues began to use zebrafish as a model organism for research. Since then, they have become a popular model organism for biomedical research. Zebrafish primarily have been used to study vertebrate development, evolution, genetics, and disease. Zebrafish are popular as pets and genetically modified, glow-in-the-dark zebrafish have been developed for the aquaria trade as well.

Zebrafish have many attributes that make it a popular model organism for biomedical research. They are small, have a short generation time, and are easy to raise in captivity. Additionally, in comparison to other vertebrates, zebrafish produce a large number of eggs per mating event. Zebrafish undergo external fertilization which allows all stages of development to be easily observed and manipulated. Zebrafish embryos are transparent, making them particularly useful for developmental and embryological research.

Positive Impacts: pet trade ; research and education

Comments: Aquarium fish. Used in carcinogenesis testing (Metcalfe 1989).