Author: Fahey & Gosliner, 2004

Order: Nudibranchia  Family:Aegiridae

Maximum Size: 8 mm

Sightings: Sunshine Coast

________________________________________________

Aegires hapsis Fahey & Gosliner, 2004

Some sea slugs are rare, or perhaps put more correctly, rarely sighted. Sometimes though this does not prevent their being described and named. This can be due to the current, and highly prudent, method of describing new species within a framework of a genus or family review. In some circumstances there may only be one or two specimens available of a rare species to include in that review, a situation that is not desirable, but nevertheless necessary in order to provide the broadest possible range of data upon which to base taxonomic decisions. Aegires hapsis is one such nudibranch.

First described in 2004 from just a single specimen collected from Okinawa, Aegires hapsis at the time was only known from that region and even then had only been sighted twice. Over the past thirteen years there have been minimal, widely scattered sightings recorded from Indonesia (two), Philippines (one) and SE Queensland, Australia (seven).

Aegires hapsis is a small elongate nudibranch of 6 to 8 mm in length. The dorsal surface has small regularly arranged raised tubercles along the sides, on the edge of the reduced mantle skirt, and in the midline behind the gills. These tubercles sprout fine spicules from their apices. The background colour is a dark cream with numerous very fine brown dots overlaid with a white reticulation. This combination gives it an appearance somewhat of a sponge’s texture and in fact the name hapsis, chosen by the authors, comes from the Greek meaning “mesh”. A few larger brown spots are usually evident between rhinophores and gills. The tripinnate gills are quite small, non-retractable, white and almost hidden by the three large, stubby protective appendages that are each branched into 4 or 5 lobes. The rhinophores are dark brown with fine white specks and as with all the Aegires species are smooth and arise from raised pockets. These pockets bear three large flat-topped tubercles (brown on top) to the lateral edge of their rims. All these features are readily discernable in the above image.

It feeds upon sponges like all the Aegiridae.

Of the photographic records currently available the specimens from SE Queensland most closely match the holotype from Okinawa.

If any sea slug could be considered rare, ephemeral even, Aegires hapsis, without doubt, also falls into that category.

References:
– Rudman, W.B. (1998). Family Aegiretidae. Pages 995–996 in P.L. Beesley, G.J.B. Ross, and A. Wells, eds., Mollusca: The Southern Synthesis. Fauna of Australia. 5, Part B. CSIRO Publishing, Melbourne.

– Fahey, S.J., Gosliner, T.M. (2004). A Phylogenetic Analysis of the Aegiridae Fischer, 1883 (Mollusca, Nudibranchia, Phanerobranchia) with Descriptions of Eight New Species and a Reassessment of Phanerobranch Relationships. Proceedings of the California Academy of Sciences 55(34): 613–689.

– This Species Profile has been modified from a previously published article in Dive Log Magazine’s – Critter ID with NudiNotes Column, Issue: #361 (August 2018): 12-13 by David A. Mullins

David A. Mullins, July 2019