How does the horseshoe crab see?
The horseshoe crab (Limulus polyphemus) is a animal in the order Xiphosurida. Its eyes belong to the vision type .
Measured in this species: colour and sharpness. Measured colour or sharpness: a measured receptor set or acuity in this species; other dials come from relatives or group defaults. Every value below carries its evidence level and sources; nothing is typed by hand.
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What stands out
- It has two colour receptor classes (a dichromat): reds and greens fall on one axis, as in red-green colour blindness in people.
- Its sharpest vision resolves 0.23 cycles per degree: the finest stripe pattern it can tell apart from grey.
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 2 receptor classes: 360 nm (UVS), 525 nm (MWS (green)) measured in this species | Measured (not re-verified) | [1][2] |
| Ultraviolet yes: at least one receptor peaks in the ultraviolet | Measured (not re-verified) | ||
| Sharpness | Acuity 0.23 cycles per degree median of 1 compilation rows (method priority rule) | Measured | [3] |
| Field of view | No value in the catalogue. | ||
| Sharp zones (foveas) | No value in the catalogue. | ||
| Night vision | Rods vs cones no rods (invertebrate photoreceptors) | Group default | |
| Motion (flicker fusion) | No value in the catalogue. | ||
Related animals
- Tuatara same vision type
- Australian lungfish same vision type
- Brine shrimp same vision type
- Coelacanth same vision type
- Commander same vision type
- Common owl-moth same vision type
More other: all other with measured vision data.
Sources
- Values stated in abstracts of PMC OA papers: 10.1085/jgp.54.5.636; 10.1007/s00114-021-01774-6; 10.1085/jgp.56.3.392; 10.1085/jgp.66.2.193; 10.1085/jgp.37.6.825; 10.1085/jgp.51.2.125. doi.org/10.1085/jgp.54.5.636
- Porter ML et al. 2006 Table 1 (opsin accessions with lambda max; mostly cephalopod/arthropod) as extracted by VPOD. github.com/VisualPhysiologyDB/visual-physiology-opsin-db
- Feller KD, Sharkey CR, McDuffee-Altekruse A, Bracken-Grissom HD, Lord NP, Porter ML, Schweikert LE 2021. Surf and turf vision: patterns and predictors of visual acuity in compound eye evolution. Arthropod Structure & Development 60:101002. doi.org/10.1016/j.asd.2020.101002
Every value cites its sources (all sources). Data: catalogue-v1, built 2026-09-29. Accuracy notes: how accurate is this?