How does the wharf roach see?
The wharf roach (Ligia exotica) is a crustacean in the order Isopoda. Its eyes belong to the vision type Crustacean (mantis shrimp, crab).
Measured in this species: colour and night vision. 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 three colour receptor classes, like most people, but one of them sees ultraviolet.
- Its sharpest vision resolves 0.05 cycles per degree: the finest stripe pattern it can tell apart from grey.
- It stops seeing flicker at 120 Hz, against 60 Hz for people in this dataset, so fast motion looks about 2 times slower to it.[6][5]
- Activity pattern: nocturnal.
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: 340 nm (UVS), 460 nm (SWS (blue)), 520 nm (MWS (green)) measured in this species | Measured | [1] |
| Ultraviolet yes: at least one receptor peaks in the ultraviolet | Measured | ||
| Sharpness | Acuity 0.05 cycles per degree median of 1 relatives in order Isopoda: Natatolana borealis | Group default | [2] |
| Angle between facets 1.6° median of 1 relatives in class Malacostraca: Phronima sedentaria | Group default | [3] | |
| Eye type compound eye | |||
| Field of view | No value in the catalogue. | ||
| Sharp zones (foveas) | No value in the catalogue. | ||
| Night vision | Activity pattern nocturnal mode of 1 rows (of 1 rows): nocturnal | Measured | [4] |
| Rods vs cones no rods (invertebrate photoreceptors) nocturnal -> rod-dominated; crepuscular / cathemeral / mixed -> mixed; diurnal -> cone-dominated | Derived | [4] | |
| Motion (flicker fusion) | Flicker fusion frequency 120 Hz median of 1 relatives in genus Ligia: Ligia occidentalis | Estimated | [5] |
Related animals
- Isopod (Booralana tricarinata) same vision type
- Isopod (Glyptonotus antarcticus) same vision type
- Rock louse same vision type
- Water louse same vision type
- Peacock mantis shrimp same vision type
- Caridean shrimp same vision type
More crustaceans: all crustaceans with measured vision data.
Sources
- Porter ML. Crustacean photoreceptor lambda max compilation, Table 1-1 (dissertation, "Porter_2005" in VPOD); extracted from PDF by VPOD with tabula. 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
- Bagheri Z, Jessop A, Partridge J et al. 2022. A new computational model illuminates the extraordinary eyes of Phronima. PLOS Computational Biology. doi.org/10.1371/journal.pcbi.1010545
- Longcore T. 2023. A compendium of photopigment peak sensitivities and visual spectral response curves of terrestrial wildlife to guide design of outdoor nighttime lighting. Basic Appl Ecol 73:40-50. doi:10.1016/j.baae.2023.09.002. doi.org/10.5281/zenodo.8432720
- 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?