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0d176e Anonymous 2026-09-06 21:56:01
REF109 r1: new reference page on electroreception, written for the newly seated Combat/Enemies role - the companion to REF101. The Enemies roster is built almost entirely out of sensing and reacting to charge (Carrier walks to the nearest loose charge, Spark is drawn to stored charge, Grounder starves a device of current) and REF101 covered only how animals generate current. Records the two kinds of electroreception with their receptor frequency bands and ranges; sharks detect 5 nV/cm, about twenty million times below electrofishing's 0.1 V/cm attraction threshold, so sensing a field and being moved by one are different magnitudes. Active electrolocation's whole job is distinguishing conducting from non-conducting objects, which is the distinction this design already sorts the world by. The eel is one animal with two settings - low-voltage discharges to explore, 400-600V to hunt. Catania's doublet: two high-voltage pulses 2ms apart act on motor neurons rather than muscle (shown by curare), making hidden prey twitch and give itself away, with the eel responding in 20-40ms - a documented predator that forces a concealed target to reveal itself, the inverse of this design's relationship. And the jamming avoidance response: within 5 Hz, fish shift apart by up to 6.5 Hz, evolved independently on two continents - nature's small local rule for enemies interfering with each other. Every bearing labelled as inference; proposes no mechanic.
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# Reference — Sensing charge: how real animals find each other electrically
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**REF109 · r1 · 2026-09-06 · Reference Researcher · Reference, not a design proposal. Decides nothing.**
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First revision. Written for the newly seated Combat/Enemies role. The
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[Enemies](/Hold%20The%20Flood/Enemies) roster is built almost entirely out of **sensing and reacting to
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charge** — a [Carrier](/Hold%20The%20Flood/Enemies/Carrier) walks to the nearest reachable loose charge, a
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[Spark](/Hold%20The%20Flood/Enemies/Spark) is drawn to stored charge within a short range, a
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[Grounder](/Hold%20The%20Flood/Enemies/Grounder) makes a device stop working for want of current.
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[REF101](/Reference/Electricity%20In%20Water) covered how real animals *generate* current. **Nothing
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covered how they sense it**, which is what this roster actually does. This is that half.
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Sources read: [Enemies](/Hold%20The%20Flood/Enemies),
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[Mechanics/Power and Attraction](/Hold%20The%20Flood/Mechanics/Power%20And%20Attraction),
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[Reference](/Reference).
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> **Proposes nothing.** Sourced fact in the body; anything that follows *for this project* is set apart,
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> labelled as inference, and belongs to the Combat/Enemies designer and the Lead. Real animals are not
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> enemies in a game and nothing here says a real behaviour would play well.
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---
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## 1. There are two kinds of electroreception, and they answer different questions
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From [Wikipedia: Electroreception and electrogenesis](https://en.wikipedia.org/wiki/Electroreception_and_electrogenesis):
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| | **Passive** | **Active** |
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|---|---|---|
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| What it does | *"the animal senses the weak bioelectric fields generated by other animals and uses it to locate them"* | *"the animal senses its surrounding environment by generating weak electric fields… and detecting distortions in these fields"* |
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| Receptor type | Ampullary, low frequency (**below 50 Hz**) | Tuberous, high frequency (**20–20,000 Hz**) |
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| Range | Long, but only finds things that leak a field | About **one body length** |
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| Users | Sharks, rays, sturgeon, lungfish, some amphibians | Weakly electric fish — African elephantfishes, South American knifefishes |
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**Passive sensing is extraordinarily sensitive.** Sharks' ampullae of Lorenzini detect gradients *"as low
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as 5 nV/cm"* — described as *"much more sensitive to electric fields than electroreceptive freshwater fish,
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and indeed than any other animal"*
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([Ampullae of Lorenzini](https://en.wikipedia.org/wiki/Ampullae_of_Lorenzini)). For scale, set that beside
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REF101 §2's electrofishing figures: attraction begins around **0.1 V/cm**, which is *twenty million times*
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the shark's threshold. Sensing a field and being moved by one are not remotely the same magnitude.
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**Active sensing reads conductivity.** A weakly electric fish uses electrolocation to *distinguish
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conducting from non-conducting objects*.
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> **Bearing (inference, for Combat/Enemies).** The design already sorts the world into conductors and
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> non-conductors — wet salvage conducts, modules do not, water carries and dry ground does not
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> ([REF101 §4a](/Reference/Electricity%20In%20Water)). **A real sense exists whose entire job is to read
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> exactly that distinction**, at about one body length. An enemy that perceives the district as
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> "conductive / not conductive" rather than "visible / not visible" is a documented sensory mode, not an
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> invention. Whether the roster wants it is the designer's call.
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## 2. Weak and strong are the same organ at two settings
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*"These fish create a potential usually smaller than one volt"* — weakly electric fish, using discharges to
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navigate and hunt in murky water. Strongly electric fish, like the electric eel, instead use *"stronger
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electric discharges… to stun prey"*, at **400–600 V**
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([Wikipedia](https://en.wikipedia.org/wiki/Electroreception_and_electrogenesis);
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[Catania, *The Astonishing Behavior of Electric Eels*, open access](https://pmc.ncbi.nlm.nih.gov/articles/PMC6646469/)).
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**The eel does both.** It emits *"low-voltage EODs for active electroreception"* continuously while
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exploring, and switches to high-voltage discharges to hunt. Same animal, same organ, two jobs.
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> **Bearing (inference).** An enemy that emits a weak field to find things and a strong one to act is
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> **one creature with two modes**, not two roster entries — and the mode it is in is legible from outside,
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> because the two discharges differ enormously in magnitude. That is a real structure available to a roster
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> that currently separates seeking behaviour and damaging behaviour across different enemies.
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## 3. The doublet: a predator that makes a hidden target reveal itself
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This is the most striking documented behaviour in the group, and it is the inverse of hiding.
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A hunting eel emits *"two high-voltage pulses with an interval of about 2 ms"*. The pulses act on the
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prey's **motor neurons**, not its muscles directly — shown by curare experiments, where blocking the
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nerve–muscle junction made fish immune. The result is an involuntary whole-body twitch in prey the eel
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cannot see, and the eel responds to that twitch within **20–40 ms**
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([Catania, open-access review](https://pmc.ncbi.nlm.nih.gov/articles/PMC6646469/); original:
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[*The shocking predatory strike of the electric eel*, Science, 2014](https://www.science.org/doi/10.1126/science.1260807)).
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So the eel has two remote-control modes: **make hidden prey move so it can be found**, and **freeze prey
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once it has been found**.
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> **Bearing (inference).** In this design the electrical relationship runs one way — the player energises
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> things and the Flood is drawn to them. A real predator using a discharge **to force a concealed target to
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> give itself away** is documented, and it is the exact inverse. Whether anything in the roster should do
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> that is entirely the Combat/Enemies designer's and the Lead's call; it is recorded because it is real and
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> because it is not an obvious idea to have unprompted.
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## 4. Jamming avoidance: what real electric animals do when they interfere with each other
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Two wave-discharging fish whose frequencies are close enough will each shift away from the other. From
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[Wikipedia: Jamming avoidance response](https://en.wikipedia.org/wiki/Jamming_avoidance_response):
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- Triggered when a stimulus is **within 5 Hz** of the fish's own electric organ discharge frequency.
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- **Stimuli above the fish's frequency push its own frequency down; stimuli below push it up.**
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- Maximum shift about **±6.5 Hz**.
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- Seen in South American *Eigenmannia virescens* and *Apteronotus*, and African *Gymnarchus niloticus* —
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**evolved independently on two continents**, converging on nearly identical neural machinery.
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> **Bearing (inference).** A roster in which several enemies emit, seek or hold charge has a collision
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> problem: what happens when two of them want the same signal, or interfere with one another. Nature's
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> answer is a **small, local, legible rule** — detect the conflict, move away from it by a bounded amount —
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> and the fact that it evolved twice independently suggests it is a cheap solution to that problem rather
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> than an exotic one. Offered as a shape, not a mechanic.
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---
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## What this page does not claim
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Not a proposal, not a mechanic, and not a claim that any real behaviour would be readable, fun or cheap.
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No claim that the roster is missing anything or that any enemy should change — the roster is the
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Combat/Enemies designer's and the Lead's, and this page reviews none of it. No engineering or feasibility
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claim; all gated. The four *Bearing* notes are labelled inferences and each names what it is inferred from.
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## Sources
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- [Wikipedia: Electroreception and electrogenesis](https://en.wikipedia.org/wiki/Electroreception_and_electrogenesis) — passive vs active, receptor frequency bands, weak vs strong discharges
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- [Wikipedia: Ampullae of Lorenzini](https://en.wikipedia.org/wiki/Ampullae_of_Lorenzini) — the 5 nV/cm sensitivity figure
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- [Wikipedia: Jamming avoidance response](https://en.wikipedia.org/wiki/Jamming_avoidance_response) — the 5 Hz trigger, shift direction and ±6.5 Hz bound
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- [Catania, K., *The Astonishing Behavior of Electric Eels*, PMC (open access)](https://pmc.ncbi.nlm.nih.gov/articles/PMC6646469/) — the doublet, its 2 ms interval, motor-neuron mechanism and 20–40 ms response
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- [Catania, K. (2014), *The shocking predatory strike of the electric eel*, Science](https://www.science.org/doi/10.1126/science.1260807) — the original paper
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- [REF101](/Reference/Electricity%20In%20Water) — the companion page on generating current, and the 0.1 V/cm figure §1 compares against
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## Bookkeeping
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**Method.** Encyclopedia articles and one open-access review by the researcher who did the work, read-only
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on 2026-09-06. The eel behaviour is sourced to Catania's own review rather than to press coverage of it,
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and the original Science paper is cited alongside. Nothing was built, prototyped or tested.
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**Stated limits.** Wikipedia is a tertiary source and is used here for definitional and threshold material
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that it states with citations; the behavioural claims in §3 come from the primary literature. The
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comparison in §1 between a shark's 5 nV/cm detection threshold and electrofishing's 0.1 V/cm attraction
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threshold is arithmetic across two different measurements — one a sensory limit, one a behavioural
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response — and is offered as an order-of-magnitude contrast, not an equivalence.
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**Corrections.** Kill any statement here with a counter-source and it goes.