The genus Robsonella Adam, 1938 belongs to the family Octopodidae and can only be identified by some characters present in males. In this work the species Robsonella fontaniana is redescribed from morphological and morphometric characters of 33 specimens (21 males and 12 females) collected on the central-south coast of Chile, during the years 2003 and 2004, and of 11 specimens (three males and eight females) obtained from the Zoological Museum of Hamburg. New diagnoses for the genus Robsonella and the species R. fontaniana are provided. Sexual dimorphism in R. fontaniana is evident by adult males having enlarged suckers and a shorter third right arm compared to the females. Some morphological characters such as ligula, radula and terminal organ diverticulum make it possible to distinguish this genus clearly from other genera. The ligula of the hectocotylized arm in Robsonella is characterized by a longitudinal groove, rounded tip, large calamus and seven copulatory lamellae. In addition, the first lateral tooth in the radula is crescent-shaped; this allows the identification of Robsonella regardless of sex.

The syntypes of the endemic Southern Ocean octopodid Pareledone polymorpha (Robson, 1930) were re-examined and measurements, counts and indices are presented. The two forms described by Robson, namely oblonga and affinis, are determined to have no taxonomic validity. The species polymorpha shows morphological similarities with Pareledone adelieana (Berry, 1917) but differs in relative arm lengths, sucker counts, external colouration and size at maturity. Both species are transferred to the new genus Adelieledone, which is separated from the genus Pareledone s.s. by the transverse ridges in the ligula groove of the hectocotylus, the sharp tip of the lower beak, the enlarged posterior salivary glands, the absence of stylets and by skin sculpture, especially by the presence of two longitudinal integumentary ridges on the dorsal mantle. A new species, Adelieledone piatkowski, is described from the Antarctic Peninsula. Beak morphology can discriminate the genera in predator studies.

The most familiar examples of erectile tissue are the genitalia of mammals, notably the penis and clitoris. Among the soft-bodied invertebrates, erectile tissue is virtually unknown, even in sex organs. Here we report that the ligula, the copulatory organ that is a modification of an arm tip of male octopuses, is erectile in Octopus bimaculoides. The normally minute ligula was observed during an unsuccessful mating attempt to be engorged. Histological sections of the ligula reveal striking structural convergences with mammalian erectile tissue: large, well-vascularized internal cavities subdivided by networks of collagen fibres and enclosed by an array of collagen fibres. This internal structure differs markedly from the dense, three-dimensional array of muscles and connective tissues seen in the other octopodid ligulae examined. Erectile tissue may represent an evolutionary compromise between opposing selective forces. Small ligulae may be advantageous because O. bimaculoides hunts in daylight and the white-faced ligula may be conspicuous to predators. Large ligulae, however, may be advantageous if the intense sexual selection thought to occur among octopodids selects for large ligulae, which can transfer larger spermatophores that carry more sperm. An erectile ligula may minimize the impact of these opposing selective forces.

The gut contents of a female specimen of Graneledone cf. boreopacifica collected from the caldera wall of Axial Volcano, near an active hydrothermal vent in the Northeast Pacific Ocean are reported. At least 30 individual gastropods and 46 individual polychaetes are represented in the gut contents by hard parts. Shell fragments and shells removed from the gut allow ready identification of the gastropods Provanna variabilis and Lepetodrilus fucensis, both of which are known only from North Pacific hydrothermal vents. Jaws of polychaete worms are identified as those of the nereidid, Nereis piscesae, and the predatory polynoids, Levensteiniella kincaidi and an unidentified species in the subfamily Branchinotogluminae. Not only was a considerable volume of prey hard parts ingested, the gastropod shells had been crushed before being ingested. The large size of the beaks in this genus of octopus and the increased area they offer for insertion of the superior mandible muscle, the prime mover in beak closure, support the hypothesis that these beaks exert sufficient force to crush the gastropod shells. Although cephalopods had been reported to be absent from hydrothermal vents, the data presented here demonstrate that not only do they occur in vent habitats, they actively prey on vent fauna.