THE ALLURING ARDEADORIS – Some examples of the genus
Some nudibranchs are both a delight to find and undemanding to photograph. Every time I happen across a species of Ardeadoris, concerns of composition and exposure just melt away as I enjoy myself, capturing their image in all their glory. Here we have a group of medium to large nudibranchs that fill the camera lens without the requirement of excessive magnification. And how they fill that lens – the colouration is stark but at the same time elegant, the combinations stunning but complimentary and the patterning simple but consummate.
The nudibranch genus Ardeadoris was raised in the Chromodorididae family to hold just a single new species of cryptobranch (can retract gill into a protective pocket below the mantle surface) dorid nudibranch described in 1984 – Ardeadoris egretta. This made it the type species of the genus by monotypy. In raising Ardeadoris, Dr. W. (Bill) Rudman stated in his 1984 paper, The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: a review of the genera: “This is another monotypic genus but Ardeadoris egretta has a number of distinctive features which separate it from all the larger genera. The wide mantle overlap is most distinctive.” He also cites an extremely long oral tube, and differences in reproductive and radula morphology (in depth details of which do not concern us here), as defining the diagnosis. In explaining the choice of name for his new genus Rudman wrote: “The genus name Ardeadoris is from the Latin “ardea”, the heron, a reference to Heron Is, Great Barrier Reef, where the type species is commonly found.” Heron Island wasn’t the Type Location though, as the designated holotype was a specimen from Escape Reef, North Queensland, just north of the well-known tourist destination, Agincourt Reef, most usually accessed from Port Douglas.
Only one other species: Ardeadoris scottjohnsoni Bertsch & Gosliner, 1989, was placed in this genus (the authors expressing their conflict, at the time, about whether it belonged in Thorunna or Ardeadoris.) until the molecular sequencing, more than 20 years later, of the Chromodorididae family by Johnson R. & Gosliner, in 2012. That groundbreaking paper transferred eleven other species into Ardeadoris, ten from Glossodoris (five through molecular testing and a further five by hypothesis) and one from Noumea (a genus now known as Verconia). Those ten Glossodoris were known by taxonomists to be similar in some respects but at the same time to be varying in certain aspects from the other Glossodoris making them somewhat difficult to place definitively. It was almost as if they were temporarily parked in Glossodoris. This uncertainty was resolved by that molecular sequencing.
There are a number of species in the Chromodorididae family, and across several genera in fact, that have a substantially white mantle trimmed with a yellow/orange line to the mantle margin or sub-margin. Many of the current thirteen described Ardeadoris species fall into that general portrait.
This NudiNote presents eight species of Ardeadoris that have, so far, been found in south east Queensland waters but also have a broad west Pacific distribution some even further across the Indian Ocean as far as the Red Sea. While none could be considered common here, a couple are seen occasionally with the others only being recorded through persistent diving over many years on the offshore reefs. These brief descriptions do not do them full justice. There are a total of thirteen described species of Ardeadoris listed on WoRMS (2022).
Gosliner et al., (2018), list and illustrate a further five putative species of Ardeadoris from the Indo-Pacific.
David A. Mullins – June 2022
– Rudman, W. B., (1984) The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: a review of the genera. Zoological Journal of the Linnean Society 81: 115-273.
– Rudman, W. B., (1985). The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: Chromodoris aureomarginata, C. verrieri and C. fidelis colour groups. Zoological Journal of the Linnean Society 83: 241-299.
– Rudman, W.B. (1986) The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: The genus Glossodoris Ehrenberg (= Casella, H. & A. Adams). Zoological Journal of the Linnean Society 86(2): 101-184.
– Bertsch, H. & Gosliner, T. M. (1989). Chromodorid nudibranchs from the Hawaiian Islands. The Veliger, 32(3): 247-265.
– Rudman, W. B, (1990.) The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: further species of Glossodoris, Thorunna and the Chromodoris aureomarginata colour group. Zoological Journal of the Linnean Society, 100(3): 263-326.
– Johnson, R. F. & Gosliner, T. M., (2012). Traditional taxonomic groupings mask evolutionary history: A molecular phylogeny and new classification of the chromodorid nudibranchs. PLoS One 7 (4): e33479.
– Gosliner, T. M., Valde ́s, A ́. & Behrens, D. W. (2018). Nudibranch & Sea Slug Identification – Indo-Pacific, 2nd Edition. New World Publications, Jacksonville, Florida, USA.
– MolluscaBase eds. (2022). MolluscaBase. Ardeadoris Rudman, 1984. Accessed through: World Register of Marine Species at: https://www.marinespecies.org/aphia.php?p=taxdetails&id=549843 on 2022-06-03
– This NudiNote has been modified from a previously published article in Dive Log Australasia Magazine – NudiNotes Column, Issue: #393 (April 2022): pp. 10-12 by David A. Mullins.