Caldukia affinis (Burn, 1958)

Description

A small arminoid. Body reddish-fawn with the median dorsum coloured orange or red; the pericardium is bright vermilion outlined in yellow, and the rhinophore-sheaths are joined by a yellow patch which connects forward to the yellow ring around the pericardium by a short, broad yellow line. Foot pale pink, long, rounded and thickened anteriorly and pointed posteriorly, extending beyond the cerata; tail crest bare. The head is small and lacks a noticeable veil; the head corners are produced into short digitiform tentacles. The cerata are fawn, externally speckled with minute red dots so that they appear reddish, and dark brown internally; the rhinophores are clear with greenish-yellow speckling.

Distribution

Southeast Australia, Bass Strait. The type locality is Torquay, Victoria, where specimens were collected under stones at and below mid-tide in October 1956 and October-December 1957.

Etymology

The specific epithet affinis is the Latin for "related" or "similar to", typically used in zoology when a new species closely resembles an existing one. Burn chose it because the rhinophore form recalls that of Madrella.

Remarks

The combination of a bright vermilion pericardium ringed in yellow, an orange-to-red dorsal midline, and an under-stone intertidal microhabitat distinguishes this species among Australian arminoids.

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References

• Proctonotus? affinis, Burn R. (1958). Further Victorian Opisthobranchia. Journal of the Malacological Society of Australia, 1(2): 20-36, pls. 6-7.
• Caldukia affinis, Burn. (2015). Nudibranchs and Related Molluscs.