Microeledone mangoldi n. gen. and n. sp., a deep-water pygmy octopus from the Norfolk Ridge, New Caledonia (Cephalopoda : Octopodidae)

Abstract

Microeledone mangoldi n. gen. and n. sp. is described from a male specimen collected from approximately one kilometre deep on the Norfolk Ridge south of New Caledonia in the south-west Pacific Ocean. This tiny octopus is characterised by a single row of suckers that are functional to the tips of the arms, the absence of an ink sac, the presence of a pair of chitinous stylets, a UU-shaped funnel organ, a copulatory organ with distinct ligula and calamus, and a distinctive radula. The radula has seven teeth per row. The unique central (rachidian) tooth has a long, sharp mesocone with a curved and grooved tip. The remaining rows of teeth are also unique, being flattened and plate-like. Marginal plates are absent. The body is smooth, without papillae, cartilaginous tubercles, or a lateral ridge. Functional chromatophores are absent. This octopus appears related to several other genera of deep-sea octopods with a single row of suckers, namely Thaumeledone Robson, 1930, Bentheledone Robson, 1932 and Graneledone Joubin, 1918, to which the new genus is compared. Definitions of the genus Thaumeledone are reviewed.