Cell naming

My previous post introduced my adventures into C. elegans.

I've gone ahead and implemented my own little cell lineage browser using django-mptt. Once I've added more functionality, I'll put it online.

But for now, I'm intrigued by the naming of cells in the lineage. In particular, the majority of cells are named by appending either 'a' or 'p' to the parent cell. What do 'a' and 'p' stand for?

As an example:

P0 -> P1' -> P2' -> C

but then

• C divides into Ca, Cp
• Ca divides into Caa and Cap; Cp divides into Cpa and Cpp

Caa, Cpa then have a slightly different progression than Cap and Cpp:

• Caa and Cpa respectively split into Caaa, Caap and Cpaa and Cpap
• these then split into Caaaa, Caaap, Caapa, Caapp, Cpaaa, Cpaap, Cpapa and Cpapp
• these then split into the 16 you'd expect except that Cpapp splits into what are called Cpappd and hyp11, Caapp splits into Caappd and PVR and Caapa splits into Caapap and DVC.

Cap and Cpp progress as follows:

• they split into Capa, Capp, Cppa, Cppp as you'd expect
• these split into Capaa, Capap, Cappa, Cappp, Cppaa, Cppap, Cpppa, Cpppp as you'd expect
• these then split into Capaaa, Capaap, Capapa, Capapp, Cappaa, Cappap, Capppa, Capppp, Cppaaa, Cppaap, Cppapa, Cppapp, Cpppaa, Cpppap, Cppppa, Cppppp
• and finally the 32 you would expect except Cppppp splits into what are called Cpppppd and Cpppppv

This is just the C lineage which is less than 10%. But I'd love to know what the 'a' and 'p' stand for; what the 'd' and 'v' stand for; and why hyp11, PVR and DVR get such a distinct names.

UPDATE: I added a "cell type" field to my browser and it revealed a couple of useful things: the "leaf nodes" (i.e. final cells) from Cap and Cpp are all marked as of cell type "muscle". The leaf nodes from Cpa (including hyp11) are all marked cell type "hypodermis". The leaf nodes from Caa are a little more interesting: The Caaa... leaf nodes are all "hypodermis". The leaf nodes from Caap are the most interesting, though. Caappd is "hypodermis", Caapap is marked as dying, and PVR and DVC are neurons.

UPDATE 2: Just as a point of comparison, there is another founder cell D whose descendants are a lot cleaner. D results in 20 cells, all of type "muscle". All are named with a/p. The only reason it's not a power of 2 is the two D{a|p}pp split into 4 whereas the others at that level split into only 2.

UPDATE 3: Based on http://en.wikipedia.org/wiki/Anatomical_terms_of_location I'm now convinced a, p, d, and v refer to anterior, posterior, dorsal and ventral respectively.