SHEA, E.K.: Morphology of the Fused Tentacles in Three Ommastrephid Squids.

Newly-hatched ommastrephid squids have fused tentacles. The fusion, which initially runs the entire length of the tentacles, divides during ontogeny to form two separate tentacles, the common condition in squids. The fused tentacles of Ommastrephes bartramii(Lesueur, 1821), Stenoteuthis oualaniensis (Lesson, 1830) and Hyaloteuthis pelagica (Bosc, 1802) are examined in detail for the first time using light and scanning electron microscopy. Measurements of the fused tentacles and the developing proximal split were taken to describe this ontogenetic event quantitatively. In all species examined, a proximal split originated at 2-3 mm dorsal mantle length (DML). In O. bartramii and S. oualaniensis, the fused tentacle length reached a maximum when the specimens were 4-5 mm DML, whereas in H. pelagica the maximum was reached between 3-4 mm DML. After the maximum is reached, the total length of the fused tentacles decreases as the split increases. In S. oualaniensis, the tentacles were fully separated in all specimens >7 mm DML. Scanning electron micrographs show no indication of torn tissue at the point of separation and reveal that some distal suckers are lost during separation.