Two-Fold Bay, Eden, southern New South Wales, Australia. March 1986. Upper photo showing animal with its bryozoan food Mucropetraliella ellerii. Photos: Bill Rudman.
Madrella sanguinea (Angas, (Jan) 1864), originally described from Sydney, eastern Australia, differs from M. ferruginosa Alder & Hancock, (April) 1864, described from southern India, only in coloration and greater size. M. sanguinea is seldom grows longer than 15mm. Specimens from around southern Australia have a bright red or orange-red background colour (M. sanguinea) while specimens from tropical Australia and the Indo-West Pacific have an orange-brown, partially translucent colour. In all cases the background colour matches the bryozoan colonies on which they feed. In southeastern Australia it feeds exclusively on Mucropetraliella ellerii (personal observations, Klemke & Keough, 1991). Specimens from Japan would appear to match the brighter red southern Australian form. I can find no anatomical differences between these colour forms. Two development types have been reported for this species, Rose (1985) describing specimens from Sydney with small numerous planktotrophic eggs & larvae, while Burn (1989) reports large direct developing eggs in specimens from Victoria, southern Australia. The two reported development types may indicate that the two names refer to different species, a widespread tropical M. ferruginosa with planktotrophic larvae and a southern Australian direct-developing species, M. sanguinea. Unfortunately no information is available on what colour form Rose's specimens were. As Sydney is a region in which tropical and south temperate faunas overlap, it is possible that if there are two species, both occur sympatrically in Sydney, and Rose's egg-mass was from `M. ferruginosa'. However, I have only ever collected the typical red M. sanguinea in Sydney. Clearly further study is required.
Both species exude a yellow, possibly defensive ecretion from a gland at the base of each ceras.
Angas, G.F. (1864). Description d'espèces nouvelles appartenant à plusieurs genres de Mollusques Nudibranches des environs de Port-Jackson (Nouvelles-Galles du Sud), accompagnée de dessins faits d'après nature. Journal de Conchyliologie, 12: 43-70.
Rudman, W.B., 2001 (January 7) Madrella sanguinea (Angas, 1864). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/madrsang