Diversity of the squid family Brachioteuthidae in Aotearoa New Zealand and the Southern Ocean

The deep-sea squid family Brachioteuthidae is one of the most systematically
unstable cephalopod taxa in need of a global revision. The general lack of adult
specimens in research collections, incomplete and inaccurate species descriptions,
descriptions based on paralarvae or early juveniles only, and sexual dimorphism
have all contributed to the instability of this family. As part of a global revision, a local
review of the New Zealand and Southern Ocean brachioteuthids is being undertaken
using integrative taxonomy. While the family was founded in 1881, Brachioteuthis
was only formally reported from New Zealand waters in 2019. In the meantime, four
genetically distinct species from around New Zealand have been identified, some of
which may represent unnamed/new species. One of these species (‘Brachioteuthis
sp. Ker 2’, sensu Braid & Bolstad 2019) forms a clade with low variation with
individuals from the northern Atlantic, which suggests that some brachioteuthids may
have very wide geographic ranges. The key morphological characters for species
level delimitation include tentacle-club morphology including carpal (fixing) apparatus
[when present], skin sculpture (useful in sexual dimorphism cases), arm
modifications in males, liver morphology, eye photophore morphology and the
general habitus based on shape analysis. This project represents a step forward in
the systematic resolution of this complicated family. However, an integrative
taxonomic approach will be required to resolve the global systematics of
brachioteuthids.