Author: Burn, 1966

Order: Sacoglossa  Family: Limapontiidae

Maximum Size: 8 mm

Sightings: Sunshine Coast

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Placida fralila Burn, 1966

I’ve discussed this sea slug with Bob Burn who has suggested Placida fralila as an identity. Bob is of the opinion that we cannot be entirely sure it is Placida fralila. However, that species, which he described in 1966 from specimens collected from Greenmount on the Gold Coast, Queensland, seems to be a good match (as far as photographic images can be), is local, lives on the same or similar Codium and has a name. I’m of the opinion it is a good opportunity to get this rarely used name known and out there. So …… Placida fralila it is. Hopefully stimulates discussion.

Bob also pointed out that there is another Placida, known locally, the ubiquitous Placida dendritica, that has a circumglobal distribution in tropical and temperate seas. It is not that species. Interestingly that species is believed to contain several cryptic species upon which research is still proceeding to separate.

There is some variation in appearance. I counted > 20 individuals on the one small algal plant and you will see the variations in the images herewith.

The algal plant it was found upon is Codium platyclados, often called the Deer-antler Codium, being of similar general appearance from images and well known in Moreton Bay and surrounds. This Codium species is multi branched, irregularly divided and quite flattened especially at the axils. It exhibits a dense covering of fine “hairs” and the sea slugs are to be found, with difficulty, crawling though those “hairs”.

The spawn of Placida fralila is visible in some of the above images. It is a tight (almost no gap) white spiral laid flat, of up to five whorls. (The specimen photographed on the spawn did not lay the spawn.)

David A. Mullins – November 2021

References:
– Burn, R. (1966). Some opisthobranchs from Southern Queensland. Journal of the Malacological Society of Australia, 1:9, 96-109.

– Jones, R. & Kraft, G. T. (1984). The Genus Codium (Codiales, Chlorophyta) at Lord Howe Island (N.S.W.). Brunonia, 7, 253-276.

– Davie, P. (2011). Wild Guide to Moreton Bay and Adjacent Coasts, Vol:2, 2nd Edition. Queensland Museum.

– Burn, R. (2015). Nudibranchs and related molluscs. Museum Victoria.