I am not so sure that the echinoderm people would appreciate having their
plutei referred to as trochophores! The echinoderm larvae have ciliary
bands running around the mouth; the trochophore prototroch is all on one
side of the mouth (dorsal if you will). I tend to limit the use of the term
trochophore, to the top-shaped larvae with a prototroch and on occasion a
telotroch and a metatroch. I am a little leary of calling for example the
cigar-shaped eunicid larvae, with their very wide, ciliary band a
trochophore, but then, the closely related onuphids at least in part has a
classical trochophore. After metamorphosis starts, i.e. when the first
segment has formed, I refer to these things as metatrochophores and then,
when they become really swimming larvae with segments and so forth, I
prefer to consider them as juveniles, especially if the prototroch has
become reduced by that time. I limit the term nectochaet to the scale
worms, where the name was originally proposed as a generic name. In
most polychaetes, as far as I can see, metamorphosis is very gradual and
does not necessarily involve the same processes in exactly the same
sequence in the different groups.
Echiurans have trochophores of course (they are probably annelids!); but
at least two non-annelid groups have them: the sipuncs and the mollusks;
in both groups the larvae tend to become very much more elaborated, and
the term trochophore should be limited to the early stages resembling the
annelid trochophores.
Kristian Fauchald
<Fauchald.Kristian at NMNH.SI.EDU>
>>> "Judith A. Fournier" <110275.1004 at compuserve.com> >>>
> That may be all right as far as annelid trochophores are concerned but >
> this is not the only phylum with trochophore larvae. Molluscs and
> echinoderms also have them. Maybe we need a different system of
> identifying annelid larvae?
-- ANNELIDA LIST
Discuss = <annelida at net.bio.net> = talk to all members
Server = <biosci-server at net.bio.net> = un/subscribes
Archives = http://www.bio.net/hypermail/annelida/
Resources = http://biodiversity.uno.edu/~worms/annelid.html
--
