A barnacle cyprid is the non-feeding, substrate-searching larval stage. It does not simply drift down and stick — it crawls over the surface on its antennules, testing local chemistry with each step before committing to permanent cement. This model reproduces the two behaviours that drive that search:
Klinokinesis (area-restricted search). Turning rate and speed are modulated by the locally sensed cue concentration C:
turn_rate(C) = turn₀ · (1 + 1.5·C)
speed(C) = speed₀ · (1 − 0.6·min(C,1))
Higher cue → slower, twistier walking → the cyprid stays near a good patch instead of wandering off, without needing to sense a gradient directly. This is the same non-directed kinesis mechanism documented in cyprid exploratory behaviour.
Dose-response settlement. Cue comes from two additive sources: a patchy bacterial biofilm field (the classic settlement-inducing signal) and a conspecific "gregariousness" field seeded by every barnacle already settled — the real cue in nature is a surface-bound protein complex barnacles detect from already-settled adults. Per-step settlement probability follows a Hill (cooperative dose-response) function of the combined cue C:
P(settle in dt) = 1 − exp( −k · Cⁿ/(Cⁿ+K²) · dt )
k = 1.2 s⁻¹, K = 0.35, n = 2
Each larva that settles cements in place and itself becomes a new source of gregarious cue — a positive feedback loop that produces the clumped, "living together" spatial pattern real barnacle beds show, purely from local rules with no global coordination.
- Biofilm cue density / Patch scale — reshape the underlying bacterial-film field larvae are walking over.
- Gregariousness — how strongly already-settled barnacles attract further settlement nearby.
- Exploration vigor — scales baseline walking speed and turning rate for the whole cohort.