How does the four-eyed fish see?
The four-eyed fish (Anableps anableps) is a fish in the order Cyprinodontiformes. Its eyes belong to the vision type Shallow-water fish tetrachromat.
Measured in this species: foveas. One measured dial: a value other than colour or sharpness is measured in this species; colour and sharpness are not measured here. Every value below carries its evidence level and sources; nothing is typed by hand.
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What stands out
- It has 6 colour receptor classes, including ultraviolet; people have 3.
- Its sharpest vision resolves 6.7 cycles per degree: the finest stripe pattern it can tell apart from grey.
- Both eyes see the same 32.85° in front of it (binocular overlap), where depth is judged best.
- It stops seeing flicker at 52 Hz, against 60 Hz for people in this dataset, so fast motion looks choppier to it.[10][9]
- Activity pattern: diurnal.
The six dials
Evidence levels: how the tiers work. "Measured" means a value measured in this species; "Estimated" values come from a close relative or an eye-size formula.
| Dial | Value | Evidence | Sources |
|---|---|---|---|
| Colour | Colour receptors 6 receptor classes: 359 nm (UVS), 409 nm (VS/SWS (violet)), 465 nm (SWS (blue)), 529 nm (MWS (green)), 542 nm (LWS (long)), 573 nm (LWS (long)) receptor set of nearest measured relative Poecilia reticulata (same order Cyprinodontiformes) | Group default | [1][2] |
| Ultraviolet yes: at least one receptor peaks in the ultraviolet | Group default | ||
| Sharpness | Acuity 6.7 cycles per degree median of 1 relatives in order Cyprinodontiformes: Poecilia reticulata | Group default | [3] |
| Field of view | Binocular overlap 32.85° group default: median of tier-A values in vision type V18 within phylum Chordata (2 species: Danio rerio, Notemigonus crysoleucas) | Group default | [4] |
| Sharp zones (foveas) | Number of foveas 0 species-v1.csv text: split aerial/aquatic retina | Measured (not re-verified) | [5] |
| Fovea type split aerial/aquatic retina | Measured (not re-verified) | [5] | |
| Night vision | Activity pattern diurnal group default: mode of tier-A values in vision type V18 within phylum Chordata (224 species: Amphiprion ocellaris, Acanthochromis polyacanthus, Acanthurus bahianus, Acanthurus chirurgus, Acanthurus coeruleus… | Group default | [6][7] |
| Rods vs cones cone-dominated | Group default | [6][7] | |
| Motion (flicker fusion) | Flicker fusion frequency 52 Hz median of 3 relatives in order Cyprinodontiformes: Xiphophorus hellerii, Poecilia reticulata, Fundulus heteroclitus | Group default | [8][9] |
Related animals
- Guppy same vision type
- Mummichog same vision type
- Amazon molly same vision type
- Bluefin killifish same vision type
- Green swordtail same vision type
- Para molly same vision type
More fish: all fish with measured vision data.
Sources
- VPOD in-vivo (MSP / single-cell) lambda max compendium, file scp_cleaned.csv, VPOD GitHub (Frazer et al. 2025 bioRxiv 10.1101/2025.08.22.671864). github.com/VisualPhysiologyDB/visual-physiology-opsin-db/tree/main/scripts_n_notebooks/vpod_ML_workflows/mine_n_match/data_sources/lmax/vpod
- Schweikert LE, Fitak RR, Caves EM, Sutton TT, Johnsen S. 2018. Spectral sensitivity in ray-finned fishes: diversity, ecology and shared descent. J Exp Biol 221:jeb189761. Table S1. doi.org/10.1242/jeb.189761
- Caves EM, Sutton TT, Johnsen S (2017) Visual acuity in ray-finned fishes correlates with eye size and habitat. J Exp Biol 220:1586-1596. Table S1.. doi.org/10.1242/jeb.151183
- Pita D, Moore BA, Tyrrell LP, Fernandez-Juricic E. 2015. Vision in two cyprinid fish: implications for collective behavior. PeerJ 3:e1113.. doi.org/10.7717/peerj.1113
- species_v1:Schwab et al. 2001
- Froese R. & Pauly D. (eds). FishBase, snapshot v25.04 (morphmet, morphdat, species, families tables), distributed as parquet by C. Boettiger for rfishbase.. fishbase.org
- Moura et al. 2024. A phylogeny-informed characterisation of global tetrapod traits addresses data gaps and biases. PLoS Biol 22:e3002658. TetrapodTraits v3.0.1.. doi.org/10.5281/zenodo.22536349
- Haarlem CS, Hynes C, Jackson AL, Mitchell KJ, O'Connell RG, Healy K. 2026. Pace of ecology drives the tempo of visual perception across the animal kingdom. Nature Ecology & Evolution (doi:10.1038/s41559-026-02994-7). Figshare dataset 10.6084/m9.figshare.30556475. doi.org/10.6084/m9.figshare.30556475
- Inger R, Bennie J, Davies TW, Gaston KJ. 2014. Potential biological and ecological effects of flickering artificial light. PLoS ONE 9(5): e98631. Table 3. doi.org/10.1371/journal.pone.0098631
- Healy K, McNally L, Ruxton GD, Cooper N, Jackson AL. 2013. Metabolic rate and body size are linked with perception of temporal information. Animal Behaviour 86:685-696. Table 1. doi.org/10.1016/j.anbehav.2013.06.018
Every value cites its sources (all sources). Data: catalogue-v1, built 2026-09-29. Accuracy notes: how accurate is this?