Template:POTD/2012-06-16
The bigfin reef squid (Sepioteuthis lessoniana) is a commercially important species of loliginid squid. It is a small to medium-sized squid, averaging 3.8 to 33 cm (1.5 to 13.0 in) in length, and is characterised by a large oval fin that extends throughout the margins of its mantle, giving it a superficial similarity to cuttlefish. It also possesses iridophores (particularly in the head), a form of structural colouration that produces iridescent metallic greens and red when illuminated, as seen here. However, it does not have photophores, and is thus not truly bioluminescent.Photo: Nick Hobgood