Polycera chilluna
Marcus, 1961

Order: NUDIBRANCHIA
Suborder: DORIDINA
Superfamily: ANADORIDOIDEA
Family: Polyceridae
Subfamily: Polycerinae

PHOTO

off Morehead City, North Carolina, USA]. Depth approx 110 ft. 15 August 2003. Approx 2" in length. Photos: Sandy Smith

Note added 9 Feb 2007: See message #19387 and earlier messages suggesting Polycera chilluna is found in Sth Africa and is a colour form of Polycera capensis.
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Sandy Smith's photos [copied alongside] of a species of Polycera from North Carolina, on the Atlantic coast of Nth America, suggest that the eastern Atlantic species, Polycera aurantiomarginata García Gómez & Bobo, 1984 is a junior synonym of Polycera chilluna Marcus, 1961, which was described from North Carolina.

Unfortunately, like many of the species described by the Marcuses, the description is based on a single preserved specimen and there is little information on the colour and shape of the living animal. The following useful information on the shape and colour can be extracted from Marcus's description:
"Colors in life fitting typical pattern of Polycera quadrilineata; light brown when preserved with interrupted dark marks. Velar appendages long, pointed, three on left, two on right (one evidently lost}..... the colour agrees with narrow-striped P. quadrilineata...."

In an accompanying drawing of the preserved animal, longitudinally arranged rows of dark elongate spots are illustrated. I assume they represent the yellow-orange colour found in the living animal. Although not mentioned in the text, there are a row of these spots along the edge of the foot, which would suggest that this animal has the orange-yellow border to the foot, so characteristic of P. aurantiomarginata.

Polycera quadrilineata is quite variable in colour, with both white and dark blue colour forms. As shown in earlier photos on the Forum, one lined colour form, with a dark blue background, is very similar in colour to P. aurantiomarginata. Marcus' comment that the colour of his specimen had the 'typical pattern of Polycera quadrilineata' could easily apply as well to P. aurantiomarginata. There are some external differences which separate the two species. One of these, which I have already mentioned, is the orange border to the foot in P. aurantiomarginata, and a second is the presence of 6 velar tentacles in P. aurantiomarginata, and only 4 in P. quadrilineata. In the description of P. chilluna, Marcus describes 5 (and one lost} velar tentacles. Another difference, the yellow tipped rhinophores in P. quadrilineata, and blue rhinophores in P. aurantiomarginata, cannot be determined for P. chilluna from the original description. From published anatomical descriptions of the jaw plates and radula, there is little to distinguish this group of species from one another.

On the available information, it would seem that P. chilluna is an earlier name for P. aurantiomarginata. This would suggest that P. chilluna is a warm water amphi-Atlantic species. It would be interesting to know if its distribution extends into the Caribbean. I would welcome comments on this suggestion.

References:
• Garcia-Gomez, J.C. & Bobo, A (1984) Una nueva especie de Polycera Cuvier (Mollusca: Nudibranchia) del litoral iberico. Cah. Biol. Mar., 25: 361-373.
• Marcus, Er. (1961) Opisthobranchia from North Carolina. Journal Elisha Mitchell Scientific Society, 77(2): 141-151.
• Ortea, J. & Rolan, E. (1989) Descripcion de una nueva especie del genero Polycera Cuvier, 1816 (Mollusca, Nudibranchia) del Archipielago de Cabo Verde. Publicaçoes Ocasionais da Sociedade Portuguesa de Malacologia, 14: 23-28.
• Valles, Y., Valdes, A. & Ortea, J. (2000) On the phanerobranch dorids of Angola (Mollusca, Nudibranchia): a crossroads of temperate and tropical species. Zoosystema, 22(1): 15-31.

Authorship details
Rudman, W.B., 2003 (September 15) Polycera chilluna Marcus, 1961. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/polychil

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