February 26, 2007
From: Alvin Alejandrino
Dear Dr. Rudman,
I wanted to share some of my Learchis poica pictures. They show three color forms of the species. I collected them all at one site from a plane wreckage just north of South Bimini Island in the Bahamas (N25d 42.008 min, W79d 15.162 min).
There were a total of 5 specimens. One had black cerata, another had whitish cerata, and the remaining three had brown cerata. During my observations, I kept them in the same petri dish. Sure enough the three color forms tried to mate. I kept them separate overnight, but it was too late because I woke up finding egg masses in the dishes.
My molecular analysis of their DNA is indicating that they are closely related to each other with small divergence in their sequences.
Locality: South Bimini Island, 2 meters, Bahamas, Caribbean, 21 March 2006, Plane wreckage on sandy bottom. Length: 6-15 mm. Photographer: Alvin Alejandrino.
Alejandrino, A., 2007 (Feb 26) Learchis poica colour forms. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19532
It would be nice to know what your research project is. This species certainly shows a lot of colour variability, but the black-brown-whitish ceratal colour variation is not a result of genetic differences but a rsult of the colour of the contents of the digestive gland duct in each ceras. In your photos the upper one with black cerata suggests it has fed on hydroids very recently while the brownish cerata in the lower left photo suggests the animal is at the end of its digestive cycle and only a bit of undigested food is left. The lower right photo which shows black just at the base of the cerata probbaly indicates that the animal has recently started feeding and the cerata are beginning to fill up with food.
If you are looking for genetic colour variations then you should look for differences in the orange-red markings on the head, the orange rings on the cerata, the amount of opaque white patching on the ceratal wall, and the nature of the white band down the dorsal midline of the body