Author: (Rudman, 1990)

Order: Nudibranchia  Family: Chromodorididae

Maximum Size: 25 mm

Sightings: Sunshine Coast

_____________________________________________________________

Ardeadoris angustolutea  (Rudman, 1990)

There are a number of dorid nudibranchs that although not brightly coloured or bizarrely patterned are a delight to record photographically due to a simplicity, almost elegance, of presentation. This not-so-common species is just such an example, its translucence and complimentary colours reflecting a most pleasing image into the camera’s lens.

Ardeadoris angustolutea is an elongated oval shaped nudibranch of the Chromodorididae family. Amongst the Ardeadoris it is at the smaller end of the size range at 25 mm. The mantle is sufficiently wide to cover the foot completely although the tail protrudes posteriorly. The edge of the mantle is formed into a few modest convolutions but with a particularly distinctive indentation located on both sides at approximately halfway between rhinophores and gill. The mantle is (most usually) translucent creamy-white with a wide midline opaque white band extending from anterior to the rhinophores to just posterior to the gill being pinched at the midpoint fold. Some specimens exhibit a diffuse bluish colour to the mantle. There is a bright opaque white band around the entire mantle margin with the very edge carrying a thin yellow to orange line. This line may sometimes be interrupted. A band of small defensive mantle glands are situated around the edge of the mantle but these are not usually obvious. The foot is coloured similarly as the mantle but at times lacks the yellow/orange line to the edge. The foot is widest anteriorly where it forms distinct corners.

The rhinophores taper to a tip. The lamellae are tan to red in colour and bear a white line on both the anterior and posterior face of the club up to the tip. The stalk is translucent. The rhinophores can retract into raised pockets. The gills too are tan to red in colour with white on the inside face of each branch. They are organized around the anal papilla as an almost complete circle being incomplete posteriorly. They can contract completely into a pocket below the mantle surface. The gills are simple in arrangement and can be observed to vibrate especially so when the animal is on the move.

Like all the Chromodorididae this species preys upon sponges. Sponges of the Darwinellidae family are the most likely candidates.

Distribution of Ardeadoris angustolutea is quite broad but not necessarily common throughout the Western and Central Pacific.

Ardeadoris angustolutea was originally described as Noumea angustolutea by Rudman in 1990. Later, in a wide ranging molecular sequencing of the Chromodorididae family in 2012 (Johnson & Gosliner), it was shifted to Ardeadoris, a genus raised by Rudman in 1984. It joined Ardeadoris egretta (Rudman’s type species for the genus) and Ardeadoris scottjohnsoni, but going across with it were ten other species all from the Glossodoris genus. This group of ten 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 difficult to place definitively. This was resolved by that molecular sequencing. There are a number of species in the Chromodorididae family, and across several genera, that have a substantially white mantle trimmed with a yellow/orange line to the mantle margin or sub-margin. Nearly all of the current thirteen Ardeadoris species fall into that general description. The phylogram in Johnson & Gosliner’s 2012 paper shows Ardeadoris angustolutea to be most closely related to A. averni followed by A. scottjohnsoni and A. egretta.

The name of the genus Ardeadoris is derived from the Latin for heron. Ardea is a genus of birds – the Herons. This is a reference by the author to Heron Island, Capricorn Group, southern Great Barrier Reef, Queensland “….where the type species is commonly found.” Regarding his choice of angustolutea for the specific epithet of this species he states: “The name ‘angustolutea’ is from the Latin for a narrow orange-yellow line, a reference to the colour of the mantle border.”

Originally described as: Noumea angustolutea.

David A. Mullins – October 2020

References:

– 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(2): 115-273.

– 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: 263-326.

– Rudman, W. B. & Bergquist, P. R. (2007). A review of feeding specificity in the sponge-feeding Chromodorididae (Nudibranchia: Mollusca). Molluscan Research, 27(2): 60-88.

– 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)

– This Species Profile has been modified from a previously published article in Dive Log Magazine’s – NudiNotes Column, Issue: #383 (August 2020): 18 by David A. Mullins.