Author: (Ruppell & Leuckart, 1830)

Order: Nudibranchia  Family: Hexabranchidae

Maximum Size: 250 mm

Sightings: Sunshine Coast

_____________________________________________________________________

Hexabranchus sanguineus has long been considered the only species of Hexabranchus in the Indo-Pacific. A recent paper (see reference below) has separated the Indo-Pacific specimens into five species. The Sunshine Coast of southern Queensland, Australia, hosts two of those species – Hexabranchus sanguineus and Hexabranchus lacer.

Across its regions of distribution Hexabranchus sanguineus is believed to present as four lineages that exhibit different colours that also change with development. On the Sunshine Coast specimens fall into Lineage 4 as outlined in the recent paper. This is a putative lineage as no specimens underwent molecular sequencing. The colour patterning is intermediate between the Indian Ocean and French Polynesia lineages. Significant characteristics include: a white vertical line up the anterior face of the rhinophores with lamellae often white-flecked, white to gill rachis, clusters of white flecks on the notum and juvenile specimens are pale with a white to yellow marginal band and white flecks to the notum.

Hexabranchus sanguineus would appear to be uncommon on the Sunshine Coast.

David A. Mullins – June 2023

References:
Tibiriçá, Y., Pola, M., Pittman, C., Gosliner, T. M., Malaquias, M. A. & Cervera, J. L. (2023). A Spanish dancer? No! A troupe of dancers: a review of the family Hexabranchidae Bergh, 1891 (Gastropoda, Heterobranchia, Nudibranchia). Organisms Diversity & Evolution. Published online: 20 June 2023, https://doi.org/10.1007/s13127-023-00611-0