Bobtail squid

They have eight suckered arms and two tentacles and are generally quite small (typical male mantle length being between 1 and 8 cm (0.39 and 3.15 in)).

The organ contains filters which may alter the wavelength of luminescence closer to that of downwelling moonlight and starlight; a lens with biochemical similarities to the squid's eye to diffuse the bacterial luminescence; and a reflector which directs the light ventrally.

[2] Sepiolida are iteroparous and a female might lay several clutches, each of 1–400 eggs (dependent on species), over her estimated one-year-long lifetime.

[2] Symbiosis with A. fischeri from the surrounding seawater is initiated immediately upon hatching, and the bacteria's colonisation of the juvenile light-organ induces morphological changes in the squid that lead to maturity.

Sepiolid taxonomy within the coleoid cephalopods is currently controversial, thus their position is subject to future change.

Diagram showing how the light organ in a bobtail squid emits light downwards to obscure its silhouette
Light from the light organ of a bobtail squid obscures its silhouette