Comparative ionoregulation: which animals defend ions versus conform
The volume's human model is one species that regulates ions precisely. Across the animal kingdom, whether an animal defends its ions or conforms to the environment is set by a single loop gain on the same R19 substrate: conformers run low gain and track the environment, regulators run high gain and hold the internal milieu against it.
Every other object in this volume models one species — the human mineral / acid-base / electrolyte loops. That leaves a question the volume could not answer: across the animal kingdom, which animals use ions precisely and which do not? This section adds that axis on the SAME R19 substrate, reusing the volume's own closed-loop law (step error = load/k) with a single knob — the loop gain that defends the internal milieu against the environmental salinity load.
One gain separates regulators from conformers
High gain holds the internal state and rejects the environment (a precise ion regulator); low gain lets the internal state track the environment (a conformer). Assigning each clade to its strategy is cited comparative physiology [L]; the reproduced result is the direction and ordering [V]. Osmoconformers (most marine invertebrates) sit at the low-gain limit; marine elasmobranchs osmoconform via urea+TMAO yet iono-regulate their inorganic ions; teleosts and tetrapods are progressively tighter regulators, with the terrestrial mammal (this volume's baseline) at the top.
| osmotic strategy | clade / exemplar | loop gain k | environment tracked |
|---|---|---|---|
| osmoconformer | most marine invertebrates (mussel, sea star, jellyfish) | 1.0 | 100% |
| urea-retaining elasmobranch | marine sharks & rays | 2.0 | 50% |
| hyperosmotic regulator | freshwater teleosts & amphibians | 3.0 | 33% |
| hypoosmotic regulator | marine teleosts | 3.0 | 33% |
| terrestrial regulator | mammals incl. human (this volume's baseline) | 4.0 | 25% |
What is reproduced
Under a fixed salinity load the conformer's internal milieu is dragged to 1.00 while the terrestrial regulator holds at 0.25 — a ratio of 4.0× that equals the gain ratio k_regulator/k_conformer (4.0), the volume's own load/k law. Sweeping a range of environments, the conformer tracks 100% of the environmental swing and the regulator only 25% — the regulator is the precise ion user. The internal excursion is monotone in loop gain across all five strategies, so a single substrate parameter orders the whole animal kingdom from conformer to tight regulator.
What stays open (the next task)
The absolute loop gains and the tolerated salinity ranges (euryhaline versus stenohaline) are [O]. Crucially, the human axis grounds its loop stiffness in a MEASURED master-gene gamma (kidney SIX2 gamma=1.5556 atop the ladder, barrier b=gamma²/4 → stiffness k); grounding each species' gain in its own measured osmoregulatory master-gene gamma is not yet done — that is the next-task obstacle [O]/[H]. The separation shown here is the reproduced direction, never a species-specific quantitative claim.