Danionella cerebrum is a species of freshwater ray-finned fish from the family Danionidae endemic to Myanmar.Britz, R., Conway, K.W. & Rüber, L. (2021). The emerging vertebrate model species for neurophysiological studies is Danionella cerebrum, new species (Teleostei: Cyprinidae). Scientific Reports, 11, 18942. https://doi.org/10.1038/s41598-021-97600-0 The species was described by ichthyologists Ralf Britz, Kevin W. Conway, and Lukas Rüber in 2021.Britz, R., Conway, K.W. & Rüber, L. (2021). The emerging vertebrate model species for neurophysiological studies is Danionella cerebrum, new species (Teleostei: Cyprinidae). Scientific Reports, 11, 18942. https://doi.org/10.1038/s41598-021-97600-0 The fish also produces an exceptionally loud sound relative to its size, coming in at 140 decibels.Cook, V.A.N.O., Groneberg, A.H., Hoffmann, M., Kadobianskyi, M., Veith, J., Schulze, L., Henninger, J., Britz, R., & Judkewitz, B. (2024). Ultrafast sound production mechanism in one of the smallest vertebrates. Proceedings of the National Academy of Sciences, 121(10), e2314017121. https://doi.org/10.1073/pnas.2314017121 The species name, cerebrum, is derived from the Latin word for "brain", reflecting the unusually small size and unique features of this vertebrate's brain.Britz, R., Conway, K.W. & Rüber, L. (2021). The emerging vertebrate model species for neurophysiological studies is Danionella cerebrum, new species (Teleostei: Cyprinidae). Scientific Reports, 11, 18942. https://doi.org/10.1038/s41598-021-97600-0 In addition to its small brain size, the brain of this fish species is externally visible due to their open skull roof, making it a prime model organism for cellular-level neurophysiological research.Conway, K.W., Kubicek, K.M. & Britz, R. (2020). Extreme evolutionary shifts in developmental timing establish the miniature Danionella as a novel model in the neurosciences. Developmental Dynamics, 250, 601–611. Because of these traits, the species has become increasingly important for advancing studies in neuroscience.Haynes, E.M., Ulland, T.K., & Eliceiri, K.W. (2022). A Model of Discovery: The Role of Imaging Established and Emerging Non-mammalian Models in Neuroscience. Frontiers in Molecular Neuroscience, 15. https://doi.org/10.3389/fnmol.2022.867010
Species description The adult Danionella cerebrum ranges from 10-13.5 millimeters in length, with 13.5mm being the maximum size recorded. These measurements are based on ten specimens examined.Britz, R., Conway, K.W. & Rüber, L. (2021). The emerging vertebrate model species for neurophysiological studies is Danionella cerebrum, new species (Teleostei: Cyprinidae). Scientific Reports, 11, 18942. https://doi.org/10.1038/s41598-021-97600-0 The brain volume of this species is 0.6 mm3.Schulze, L., Henninger, J., Kadobianskyi, M. et al. (2018). Transparent Danionella translucida as a genetically tractable vertebrate brain model. Nature Methods, 15, 977–983. https://doi.org/10.1038/s41592-018-0144-6 In addition, the bodies of Danionella cerebrum are optically translucent, making it so most of their internal organs are visible directly through their skin even into adulthood.Schulze, L., Henninger, J., Kadobianskyi, M. et al. (2018). Transparent Danionella translucida as a genetically tractable vertebrate brain model. Nature Methods, 15, 977–983. https://doi.org/10.1038/s41592-018-0144-6 This unique characteristic allows researchers to have the ability to directly observe internal structures of this fish, such as the brain, heart, and swim bladder, without needing to do a dissection.Misyuk, M.K., Austin, J.L., Walechka, N.R., Peterka, J.A., Veldman, M.B., & Lam, P.Y. (2025). See-through science: Danionella cerebrum as a model for neuroregeneration. bioRxiv. https://doi.org/10.1101/2025.05.13.653880
Danionella cerebrum has an elongated body with a short dorsal fin. The dorsal fin is positioned opposite to the posterior half of the long anal fin. This species has a large head, large eyes, well-developed nostrils, and a supraterminal mouth, also known as a superior mouth. A supraterminal mouth is an upturned mouth where the lower jaw is longer than the upper jaw. The lateral line canals and pores on the head and body of this fish are absent as well.Britz, R., Conway, K.W. & Rüber, L. (2021). The emerging vertebrate model species for neurophysiological studies is Danionella cerebrum, new species (Teleostei: Cyprinidae). Scientific Reports, 11, 18942. https://doi.org/10.1038/s41598-021-97600-0
One particular identifier that separates this species from other Danionella species is the number of anal-fin rays. Danionella cerebrum has 15-18 anal-fin rays, whereas D. dracula possesses 12-14, D. translucida possesses 12-15, and D. priapus possesses 20-21 anal-fin rays. Not only is this species different in its number of anal ray fins, but this species is also unique in this genus in that it possesses 6 pectoral ray fins versus the 8 in D. priapus and 7 in D. dracula. In addition, another note on morphological distinctions of this species can be made by examining the number of vertebrae present, as D. cerebrum has 33-35 vertebrae, whereas other species of Danionella (D. mirifica, D. dracula, and D. priapus) have 36-38 vertebrae.Britz, R., Conway, K.W. & Rüber, L. (2021). The emerging vertebrate model species for neurophysiological studies is Danionella cerebrum, new species (Teleostei: Cyprinidae). Scientific Reports, 11, 18942. https://doi.org/10.1038/s41598-021-97600-0
Sexual dimorphism In terms of the sexual dimorphism of this species, their coloration is translucent and lacks an overall body color. However, they do exhibit a yellow coloration that covers the dorsal side of their skull. This coloration is caused by chromatophores, which are irregularly scattered on the top and sides of the head and are also in a row going back behind the shoulder. On the other hand, females of this species exhibit a slightly darker coloration, as females with eggs have large melanophores containing darker pigments that line their abdominal wall and make the eggs quite visible to the outside observer from within the body cavity.Britz, R., Conway, K.W. & Rüber, L. (2021). The emerging vertebrate model species for neurophysiological studies is Danionella cerebrum, new species (Teleostei: Cyprinidae). Scientific Reports, 11, 18942. https://doi.org/10.1038/s41598-021-97600-0
This species also exhibits well-developed Weberian ossicles, a series of bones that connect the swim bladder to the inner ear, and one such bone in this series, the os suspensorium, exhibits a strong sexual dimorphism between the sexes of this species. This os suspensorium, which is essentially the outer and inner arms that cover the roof of their swimbladders, is much more robust and developed in males. Males also have a drumming cartilage that is correlated with their swim bladder and their 5th rib. The cartilage is well ossified in males, but is weak and poorly ossified in females.Britz, R., Conway, K.W. & Rüber, L. (2021). The emerging vertebrate model species for neurophysiological studies is Danionella cerebrum, new species (Teleostei: Cyprinidae). Scientific Reports, 11, 18942. https://doi.org/10.1038/s41598-021-97600-0 All of these characteristics that males of this species possess and females lack lead to males having the ability to generate sounds capable of exceeding 140 decibels, which is comparable to a jet engine, causing immediate damage to human hearing. This behavior is not observed in the females of this species.Cook, V.A.N.O., Groneberg, A.H., Hoffmann, M., Kadobianskyi, M., Veith, J., Schulze, L., Henninger, J., Britz, R., & Judkewitz, B. (2024). Ultrafast sound production mechanism in one of the smallest vertebrates. Proceedings of the National Academy of Sciences, 121(10), e2314017121. https://doi.org/10.1073/pnas.2314017121 This loud burst of sound in males of this species is believed to be a factor in roles including but not limited to social communication and aggression in interactions between males.Cook, V.A.N.O., Groneberg, A.H., Hoffmann, M., Kadobianskyi, M., Veith, J., Schulze, L., Henninger, J., Britz, R., & Judkewitz, B. (2024). Ultrafast sound production mechanism in one of the smallest vertebrates. Proceedings of the National Academy of Sciences, 121(10), e2314017121. https://doi.org/10.1073/pnas.2314017121
Figure 1. Male (a) and Female (b) Danionella cerebrum. Male (10mm) and female (12mm) are shown live. Live specimens have translucent bodies with yellow chromatophores on the top of their head. Females possess large melanophores that line the abdominal wall and make the internal eggs visible externally. (e-h) Exhibit the differences in skeletal structure between the male (e and g) and the female (f and h), showing a more robust Weberian apparatus and the presence of drumming cartilage in males and the lack or weaker structures of those in females of this species.Britz, R., Conway, K.W. & Rüber, L. (2021). The emerging vertebrate model species for neurophysiological studies is Danionella cerebrum, new species (Teleostei: Cyprinidae). Scientific Reports, 11, 18942. https://doi.org/10.1038/s41598-021-97600-0
Geographic distribution Danionella cerebrum is distributed across a number of streams on both the southern and eastern slopes of the Bago Yoma mountain range of Myanmar. More specifically, these streams include Tandabin Chaung and Bala Chaung, located in the Yangon Division, and an unnamed stream northwest of Daikme Chaung in the Bago Division of Myanmar. The streams in which they are found are all relatively turbid, low-altitude freshwater streams and roadside canals near the town of Hmawbi. In addition, this species, D. cerebrum, was found to overlap with and co-occur with a close relative, D. translucida, at Hmawbi.Britz, R., Conway, K.W. & Rüber, L. (2021). The emerging vertebrate model species for neurophysiological studies is Danionella cerebrum, new species (Teleostei: Cyprinidae). Scientific Reports, 11, 18942. https://doi.org/10.1038/s41598-021-97600-0
Habitat In terms of the habitat conditions within these streams and roadside irrigation canals, all possessed shared characteristics such as visible flow, surface temperatures of around 30 degrees Celsius, a pH ranging from 7.4-7.5, and soft water of 20-100 micro Siemens. In terms of where the fish was found inhabiting within the water column, D. cerebrum was found at a depth below 30 centimeters rather than at the water's surface, and so the water was significantly cooler at this depth, at 25 degrees Celsius.Britz, R., Conway, K.W. & Rüber, L. (2021). The emerging vertebrate model species for neurophysiological studies is Danionella cerebrum, new species (Teleostei: Cyprinidae). Scientific Reports, 11, 18942. https://doi.org/10.1038/s41598-021-97600-0
Figure 2. (Upper left) shows a tree of genes of the five species of Danionella. (Upper right) shows a distribution sampling map. Note: D. cerebrum and D. translucida have some overlap. (Lower left) Hmawbi roadside canal (Lower right) Daikme ChaungBritz, R., Conway, K.W. & Rüber, L. (2021). The emerging vertebrate model species for neurophysiological studies is Danionella cerebrum, new species (Teleostei: Cyprinidae). Scientific Reports, 11, 18942. https://doi.org/10.1038/s41598-021-97600-0
Biology