Flabellina nudibranch

Flabellina affinis is one of the most visually striking nudibranchs in the Mediterranean — vivid purple with cerata tipped in orange or white — and it is reliably encountered at Capo Testa on hydroids growing over posidonia matte and rock surfaces. It feeds selectively on specific hydroid species and sequesters their nematocysts into its own cerata for chemical defence. The species is a key target for macro photographers visiting the site and is especially abundant from spring through early summer.