Social structure of Dyopedos bispinis on the masts
Among 1057 masts identified in underwater photos, 757 structures were inhabited (72%) and sorted into the following groups (Table 1): (1) masts occupied by one or several juveniles (195 masts, 26% inhabited); (2) masts occupied by a single adult (or subadult) female, often with several juveniles (402 masts, 53%); (3) masts occupied by 1 adult or subadult male, rarely with juveniles (30 masts, 4%); (4) masts occupied by two adults (female and male), often with juveniles (125 masts, 17%); (5) masts occupied by three adults (5 masts, less than 1%), typically two females and one male.
During dives, masts occupied by three or more (up to 23) adults were also observed (Table 2), and in one case, all 15 females inhabiting one mast were ovigerous. Such masts were rarely observed, but they were unusually long, measuring approximately 15-20 cm, and were easily detected. Ordinary masts are typically not more than 10-12 cm in length.