How does the horn shark see?
The horn shark (Heterodontus francisci) is a shark or ray in the order Heterodontiformes. Its eyes belong to the vision type Shark, ray and warm-eyed ocean predator.
Measured in this species: motion (flicker fusion). 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.
What stands out
- It has three colour receptor classes, like most people.
- Its sharpest vision resolves 3.125 cycles per degree: the finest stripe pattern it can tell apart from grey.
- It stops seeing flicker at 20 Hz, against 60 Hz for people in this dataset, so fast motion looks choppier to it.[5][6]
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 3 receptor classes: 475 nm (SWS (blue)), 533 nm (MWS (green)), 562 nm (LWS (long)) receptor set of nearest measured relative Urobatis jamaicensis (same class Elasmobranchii) | Group default | [1][2] |
| Sharpness | Acuity 3.125 cycles per degree median of 1 relatives in genus Heterodontus: Heterodontus portusjacksoni | Estimated | [3] |
| Field of view | No value in the catalogue. | ||
| Sharp zones (foveas) | No value in the catalogue. | ||
| Night vision | No value in the catalogue. | ||
| Motion (flicker fusion) | Flicker fusion frequency 20 Hz median of 1 rows (no bright-light flag) (single-neuron rows; all rows: [20.0]) | Measured | [4] |
Related animals
- Port jackson shark same vision type
- Brownbanded bamboo shark same vision type
- Scalloped hammerhead shark same vision type
- Australian ghostshark same vision type
- Blacknose shark same vision type
- Blacktip reef shark same vision type
More sharks and rays: all sharks and rays with measured vision data.
Sources
- Hart NS, Lamb TD, Patel HR et al. 2020. Visual opsin diversity in sharks and rays. Mol Biol Evol 37:811-827. doi.org/10.1093/molbev/msz269
- 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
- Caves EM, Sutton TT, Warrant EJ, Johnsen S 2023. Measures and models of visual acuity in epipelagic and mesopelagic teleosts and elasmobranchs. Journal of Comparative Physiology A. zenodo.org/records/8251016
- 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
- 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
- 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
Every value cites its sources (all sources). Data: catalogue-v1, built 2026-09-29. Accuracy notes: how accurate is this?