Author: Undescribed

Order: Sacoglossa  Family: Plakobranchidae

Maximum Size: 4 mm

Sightings: Sunshine Coast

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Elysia sp. 33 Undescribed

In the Elysia genus of the sap-sucking Sacoglossa order most species carry their parapodia tightly closed or nearly so, or only partially open where the undulations don’t necessarily meet together. However there are a small number that- unusually – have them laid completely open flat. This undescribed species – Elysia sp. 33 in our list – is one of the latter.

The narrow body of Elysia sp. 33 is belied by the extent of the opened parapodia. The parapodia were observed to be open the entire time. The parapodia separate behind the head just anterior to the pericardial hump and remain open until petering out at the tapered tail. They are formed into two pair of extensions, the first and largest pair located posterior to the pericardial hump and a second smaller pair two-thirds along the length of the animal. The parapodial edges carry small evenly-spaced rounded white papillae. The rhinophores are rolled, relatively long and bear rounded white papillae along their length.

Elysia sp. 33 is light green in colour becoming darker green on the dorsal midline. Close examination of the green colour inside the parapodia reveals that the green colour is made up of small round discrete bodies possibly indicative of chlorophyll in the branches of the digestive gland. The rhinophores are speckled in white reaching the greatest concentration at their bases where they insert, side-by-side, into the head. The pericardial hump is also covered in a concentration of white specks. White specks also line the parapodial edges joining together the previously mentioned white papillae. Randomly scattered white specks can be seen over the dorsal surface of the parapodia. Black eye-spots are visible just lateral to the rhinophore bases. The body and head also carry scattered small white papillae.

Elysia sp. 33 was found upon a sea grape – the alga Caulpera racemosa, that is assumed to be its food.

David A. Mullins – December, 2021