Histoctopus

Lore & Background

The genus Histoctopus was described in 2009 by Mark D. Norman, Renata Boucher-Rodoni and F. G. Hochberg in the Journal of Molluscan Studies. The name combines octopus with the Greek word histos, meaning 'web' or 'tissue', referring to the membrane on the outside of the arms. The type species, Histoctopus zipkasae, was named after the senior author's wife, Karen Zipkas, while H. discus derives from the Latin discus, meaning 'plate', in reference to its large suckers.

Histoctopus are small to medium-sized octopuses with an orange-brown colouration. Each muscular arm bears two rows of large suckers. Nothing is known about the life history of either species. They are found at depths between 200 and 750 metres (660 and 2,460 ft). Histoctopus zipkasae occurs in the south-west Pacific Ocean, while Histoctopus discus is found in the Indian Ocean.

The genus is most similar to Scaeurgus and Galeoctopus based on morphology, though its phylogenetic relationship to other genera is unknown. The web margins on the arms, the genus's most distinctive feature, also occur in three other octopus genera (Velodona, Graneledone, and Pteroctopus), but those genera are readily distinguished by other characteristics. All four genera inhabit the benthic zone of deep water habitat, typically deeper than 200 metres (660 ft), leading Norman et al. to propose that the presence of the margins is the result of convergent evolution. Their function is unknown; possibilities include aiding in ensnaring prey or in swimming.

Reader's Guide

Histoctopus contributes to the understanding of deep-water octopus diversity and convergent evolution. Its most distinctive feature—the web margins on the arms—is shared with three other genera (Velodona, Graneledone, and Pteroctopus), all of which inhabit deep benthic environments. Norman et al. propose that this similarity arose through convergent evolution rather than common ancestry, as the genera are readily distinguished by other characteristics. The function of these margins remains unknown, with hypotheses including prey capture or swimming assistance. The genus was described in 2009, adding two species to the known octopus fauna: one from the south-west Pacific and one from the Indian Ocean. Despite its morphological distinctiveness, the phylogenetic relationship of Histoctopus to other octopus genera is unresolved. The lack of any known life history for either species highlights how little is understood about deep-water cephalopods. The genus name itself—derived from the Greek for 'web'—directly reflects its most notable anatomical trait, and the species names honor the describer's wife (H. zipkasae) and the large suckers (H. discus).