Buries itself in sand by day and emerges at night. A common night-dive subject on silt.
A compact, rounded little cephalopod with eight arms and two tentacles and small rounded fins set high on the mantle like ears. The body is translucent and densely covered in dark chromatophores that read underwater as a blend of small dark, electric blue and green dots. The sexes differ in size: males reach about 3 cm mantle length and females about 5 cm. Sepiolids are told from small cuttlefish by the absence of a cuttlebone and by those rounded ear-like fins. Several Euprymna species overlap in range and are not reliably separable underwater, so the genus is usually as far as a photograph will take you.
Benthic on sand and fine sediment, and it buries — both to rest by day and as an escape, kicking sand over itself with the arms and fins until only the eyes remain. Nocturnal, emerging at night to feed on small benthic crustaceans. It carries a bilobed light organ in the mantle cavity housing luminous bacteria; the accepted function is counter-illumination, emitting just enough downward light to erase its own silhouette against the moon. That symbiosis has been studied exhaustively in a Hawaiian relative and is generally assumed here rather than demonstrated. No published depth range for this species could be found; shallow coastal soft sediment is as much as can honestly be said.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
