Meeting Abstract
The Histioteuthidae are a family of deep-sea oegopsid squids with a striking morphological feature: their left eye can be up to twice the diameter of their right eye, earning them the name of the “cock-eyed” squids. These strange eyes are thought to serve different visual functions in the dim waters of the mesopelagic ocean. The larger eye may be adapted to viewing dim downwelling light from above, while the smaller eye may be specialized for detecting flashes of bioluminescence. However, the in situ posture of histioteuthids and the orientations of their eyes have not been previously reported. We used ROV video to document depth, posture, body orientation, and eye orientation in two histioteuthid squids from the Monterey Submarine Canyon: Histioteuthis heteropsis (n=152) and Stigmatoteuthis dofleini (n=9). We found that both histioteuthids are consistently found in either a j-pose posture with the arms curled up around the mantle or a straight-arm posture with an oblique mantle. The large left eye orients upward between 15° and 75° from a horizontal axis (n=32, mean=45, SD=12), and the small right eye orients slightly downward 10° to 70° below a horizontal axis (n=25, mean=33, SD=11). We also noted the presence of a yellow pigment in the large left lenses of some adult individuals. Preliminary investigation of this pigment indicates that it acts as a long-pass cutoff filter and may develop late in life. The implications of observed in situ histioteuthid orientation and lens pigmentation are discussed in the context of vision and camouflage in the twilight zone of the deep sea.
