Placida cremoniana (Trinchese, 1892)
Placida cremoniana (Trinchese, 1892)
|Classification according to Bouchet et al. (2017)|
Taxonomic source: World Register of Marine Species (AphiaID: 141564).
- Ercolania trinchesii Pruvot-Fol, 1951
- Hermaea carminis Fez, 1962
- Hermaea cremoniana Trinchese, 1892 (original)
The specimens can reach a size of 10 mm in length. The coloration is very peculiar and distinctive from other saccglossans. The head, the rhinophores, the back and sides of the animal and the upper third of the cerata are dark purple, almost black, while the head veil, the foot, the basal third of the cerata and a band on each side of the body are yellow gold. The body is very slim, the head has a rounded fold or cephalic veil. The rhinophores are auriculate and slightly wider at the base, there is a grayish-white longitudinal band on the outside of the rhinophores that continues behind their base, forming a “V” feature near the eyes. The cerata are fairly numerous and evenly cover the back of the animal, showing no clear sign of grouping. Their size increases from the ones located in the sides to the ones located dorsally. The shape of the cerata is elongated, with an enlarged mittle part and a sharpened tip. The cardiac region is in the dorsal half, at the height of the first cerata, and right before it there is the anal papilla, colored deep purple but with a white top. The foot is narrow, the anterior part somewhat broadened and the tail is short and narrow.
This species usually lives in shallow waters between different photophilic algae as Halimeda tuna, several Rhodophycean and Phaeophycean algae and also in Posidonia oceanica meadows . In Japan this species have been found to eat the thalli of the chlorophycean algae Derbesia but with European specimens nothing else is really known about their food, as nothing is known about where or how it gets the decorating pigment for the body. The spawn is an egg ribbon in the shape of a crescent or a nearly complete circle, with a diameter of 2 mm; eggs are small, of about 50-60 microns in diameter.
- Placida. From Latin “placeō”, please, satisfy. Also means placid, gentle, quiet, still, calm, mild, peaceful.
- Cremoniana. From Cremona, city located in the North of Italy, between Pavia and Parma, near Genoa.
This species was originally described from the coast of Naples (Italy) but since then, it has been cited in the Mediterranean Sea (both in Eastern and Western coasts) and the near Eastern Atlantic (Canaries, Madeira and Azores). In the Iberian Peninsula it has been observed in most of its coastline, both Mediterranean and Atlantic and in the Balearic islands. In Catalonia it is easy to spot on seaweeds hanging from rocky walls in the Costa Brava and along the coast of Barcelona. According to McCarthy et al (2017) there are several similar species forming a cryptic group with Placida cremoniana:
- Placida cremoniana – Mediterranean Sea and NE Atlantic
- Placida brookae – California (USA) and Galapagos (Ecuador)
- Placida kevinleei – Japan and Hawaii (USA)
- Placida barackobamai – Australia, Hawaii (USA), Japan and Guam
They could be differentiated visually by using the following visual key:
| : OBIS|
: GROC 2010-2011
: Enric Madrenas
: João Pedro Silva
: Bernard Picton
| : OPK|
: Manuel Ballesteros.
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