Description of a zoea of Lysmata

The anatomy of larval crustaceans is rather complex and hard to assess to non specialists.Yet it is fascinating to watch all the changes that decapod larvae,called ZOEA undergo until they finally settle as tiny replicas of their parents.They run thru different stages wich we call Z1,Z2,etc.
I want to use one of the very clear pictures of the 1st zoea of L.amboinensis,posted by Jim W.,to describe and explain the appendix of this first stage,which is the most primitive and simple.
A the front end we can see the antennulae in the center and the antennae to the sides.They are called A1 and A2.
And behind the eyes,we can see what looks like 4 pairs of legs.Which are not real legs, but maxillipedia,which will become mouth parts in the adult.And they are not 4,but only 2 pairs,which are called MP2 and MP3 (MP1 can not be seen without dissection).
But why we see 8 "legs"?.It happens that each of these appendix splits into two ranches,very close to their "root".The inner branch is called endopodite,and show some spines like fingers in Jim´s pics.The endopodite of MP2 is small,just close to the eyes.
For simplicity,I call the endopodites "walking legs"
And then we have the exopodites,with long "setae" (hairs)that are kept waving and afford propulsion to the larva.I call them "swimming legs".
The weird thing is that every appendix seems to be two different "legs",and one needs to check the pics carefully to see that both stem from the same root.
This bizarre condition will be repeated with all the real legs when they begin to show.They are called pereiopods (PP).With the exception of PP5,which doesn´t have a swimming branch.PP5 are the large conspicuous paddle legs of older zoea.


  
 

I can´t post Jim´s pics here