A Unique Case of Bilateral Hectocotylization in the North Pacific Giant Octopus (Enteroctopus dofleini)

Abstract

Life-history information regarding most cephalopod species is somewhat scarce, and information relating anatomical anomalies of cephalopods is even more limited. For octopus species, the few anomalies that have been reported include: arm bifurcations (Smith, 1907; Okada, 1965; Gonzalez & Guerra, 2006), fourtharm hectocotylus (Robson, 1929), hexapody (Toll & Binger, 1991), septapody (Gleadall, 1989), decapody (Toll & Binger, 1991), and double hectocotylization (Robson, 1929; Palacio, 1973). Most male octopus have a modified third right arm or hectocotylus that is specialized for passing sperm packets to females. The tip of this specialized arm, known as a ligula, is spoon-shaped bearing a seminal groove ending in a rounded calamus. There are only three species of octopus that typically have the hectocotylized arm on the third left arm instead of the third right: Scaeurgus unicirrhus, Euaxoctopus panamensis and Pteroctopus tetracirrhus (Palacio, 1973). In over one hundred years of research, double hectocotylization has been reported in only six individual cases in six different species of octopus including: Eledone cirrhosa (by Appellof, 1892), Octopus briareus (by Robson, 1929), Octopus vulgaris (by Palacio, 1973), Octopus selene (by Palacio, 1973), Octopus chierchiae (by Roy Caldwell, personal communication) and Octopus minor (by Higashide et al., 2007). In each case, the third right arm was hectocotylized, along with an additional arm from the right side of the body (unilateral hectocotylization) or a left arm (bilateral hectocotylization). mentation of double hectocotylization for the Enteroctopus dofleini cephalopod having double hectocotylization not including either the third right or left arm. MALACOLOGIA, 2013, 56(1 2): 297 300