Domain: Natural Science — Ecology & Evolutionary Biology
Target concept: Signal Variation in the Ghost Crab: Left-Right Claw Oscillation in Europe and Up-Down Claw Oscillation in North America

Video generation prompt: Left panel: European species performing repeated claw waving. Right panel: North American species performing repeated claw waving. Static camera, clearly demonstrating the movement of the claws.

Evaluation guide:
(i) Target concept: An illustrative left-right vs. up-down claw-waving contrast between two ghost crab (Ocypode) populations, used to test whether a model can render two similar-looking crabs performing visibly different oscillation patterns.
Minimum mechanism: Claw waving must be voluntary, rhythmic, and produced by the major cheliped; motion axis must be constrained to one primary plane (horizontal for the left-side crab, vertical for the right-side crab); no locomotion or body rotation may accompany waving; the signal must be clearly visible and repeated over multiple cycles.
(ii)Storyline: Frame 0–1s: Static wide shot reveals two crabs side-by-side on sand, fully visible, front-facing, no motion. Frame 1–3s: Left crab initiates horizontal oscillation (left→right→left); right crab remains still. Frame 3–5s: Right crab initiates vertical oscillation (up→down→up); left crab continues horizontal motion. Frame 5–9s: Both crabs sustain their own characteristic oscillation synchronously, no deviation in plane or posture. Frame 9–10s: Motion continues uninterrupted to end. Perspective: Fixed frontal view, eye-level, no occlusion, uniform ambient light, no camera motion or zoom.

Manual:
Experimental Procedure
1. Position two live adult ghost crabs (genus Ocypode) side by side on a uniform sandy substrate: one representing a Mediterranean/European coastal population on the left, one representing a North American population (e.g., Ocypode quadrata) on the right.
2. Fix the camera directly frontal and static, framing both crabs side-by-side in equal halves of the frame.
3. Record several seconds, allowing each crab's natural claw-waving display to proceed without interference.
Observation of Experimental Phenomena
Left panel: the crab repeatedly moves its major cheliped horizontally — leftward then rightward — with minimal vertical lift.
Right panel: the crab repeatedly moves its major cheliped vertically — upward then downward — with minimal lateral sway.
Summary of Experimental Principles
Ghost crabs (genus Ocypode) use rhythmic waving of the major cheliped in territorial and courtship displays; the plane of oscillation can differ between populations and display contexts. This scenario uses a left-right vs. up-down contrast between two regional Ocypode populations as an illustrative example of population-level signal variation, not as a report of one specific published study; no invented taxon name (e.g., 'Crabius europaeus') should be treated as a real species.

Prompt Grounding rubric:
level_1: Neither a left crab nor a right crab appears in a side-by-side layout; no claw-waving motion is shown by either crab; the camera is not static; or there is no clear visual separation between a left group and a right group.
level_2: A side-by-side layout appears, but the crabs are swapped or mismatched relative to the prompt (e.g., the North American-type crab appears on the left); or only one crab performs claw-waving while the other is inactive; or the camera pans, tilts, or zooms instead of staying static.
level_3: Two ghost crabs appear side by side, one on the left and one on the right, with an unambiguous visual separation between them; both crabs perform a repeated claw-waving motion with the major cheliped; the camera stays static throughout the shot.
level_4: Everything required for score 3 is present, and in addition: the two crabs are visually distinguishable from one another (e.g., differing claw proportions, coloration, or size) so a viewer could tell them apart as two separate individuals/populations; the waving motion is repeated across multiple cycles rather than a single isolated movement; nothing occludes either crab or breaks the left/right framing.
level_5: Everything required for score 4 is present, and in addition: the left-side crab is fully visible, front-facing, and centered within its half of the frame while performing left-right claw waving; the right-side crab is fully visible, front-facing, and centered within its half of the frame while performing up-down claw waving; no duplicated limb, flickering body part, or other visual artifact appears on either crab.

Scientific and Causal Correctness rubric:
level_1: The oscillation axis is swapped relative to the intended left-right/up-down contrast (e.g., the left crab waves up-down or the right crab waves left-right); or both crabs wave along the identical axis; or no waving motion occurs at all.
level_2: One crab shows the correct oscillation axis for its side, but the other does not (e.g., the right crab also waves left-right instead of up-down); or the oscillation axis is impossible to tell because of occlusion, unusual rotation, or blur.
level_3: The left crab's claw motion is predominantly left-right (horizontal), and the right crab's claw motion is predominantly up-down (vertical); both motions repeat over multiple cycles and look like a plausible display movement rather than random twitching.
level_4: Everything required for score 3 is present, and in addition: across at least three repeated cycles, the left crab's motion shows essentially no vertical drift and the right crab's motion shows essentially no horizontal drift; the movement clearly originates from the major (larger) claw rather than a walking leg or the minor claw; neither crab's motion freezes or reverses direction mid-sequence.
level_5: Everything required for score 4 is present, and in addition: the left crab's motion is a clean back-and-forth horizontal sweep with no twisting, lifting, or forward reaching mixed in; the right crab's motion is a clean up-down vertical sweep with no side-to-side sway or twisting mixed in; neither crab walks, turns its body, or otherwise relocates while waving — the waving is the only motion each animal performs.

Spatiotemporal Consistency rubric:
level_1: One crab vanishes from its half of the frame and reappears elsewhere, or one crab visibly changes proportions between frames; the boundary between the left and right areas breaks or dissolves; the lighting jumps abruptly partway through the clip; or the claw motion stutters/freezes for a noticeably long pause (roughly a second or more).
level_2: The dividing line between the left and right areas shifts or flickers; a crab briefly leaves its half of the frame and re-enters; background sand appears to shift or drift with no matching motion blur; the lighting brightens or dims without an apparent cause; or the claw motion shows more than a couple of visible jump/skip artifacts (the claw seems to relocate without passing through the positions in between).
level_3: Neither crab leaves its assigned half of the frame; no jump-cuts, dissolving boundaries, or abrupt lighting changes occur; no limb or claw appears to detach, distort, or vanish; the claw motion in each half looks continuous rather than stepped or interrupted; both crabs stay within their half of the frame for the full duration.
level_4: Everything required for score 3 is present, and in addition: the left and right halves keep a fixed size and position relative to each other (neither scales up, shifts, or rotates relative to the other); the sand texture and lighting look the same in both halves (no mismatched shadow direction or grain between sides); the claw movement in each half runs at a steady, natural speed without sudden speed-ups or halts.
level_5: Everything required for score 4 is present, and in addition: the camera view stays completely still with no detectable drift, sway, or wobble for the whole clip; the two crabs stay in sync with each other in terms of frame timing (neither half appears to lag or skip relative to the other); the vertical line separating the two halves (if any) stays straight and unbroken in every frame.