See‑through fish highlights midwater vision arms race

New 4K ROV footage from MBARI captured a barreleye (Macropinna microstoma) about 2,000 feet deep, showing its transparent forehead and upward‑looking eye anatomy. The observation gives direct evidence of optical specializations in the twilight zone and of evolutionary strategies (e.g., stealing siphonophore prey, shadow‑detection) that shape midwater ecology. — Rare, verifiable deep‑sea sightings provide concrete evidence to argue for sustained ROV monitoring, inform conservation priorities for the twilight zone, and illustrate how sensory evolution mediates deep‑ocean food webs.