White blood cells..Mammals only?

[glover martin]

robertson jason vict (jroberts at ehsn12.cen.uiuc.edu) wrote:
: Are white blood cells present in mammals only?  I came across a reference that

No.  I know that at least birds have white cells also.

: implied that they were.  If so, what do non-mammals use to defend against
: microorganisms?

I think that almost all metazoans (somebody stop me if I'm wrong) have at 
least rudimentary phagocytic white cells.  And I think that in insects 
these cells may also act as carriers of gas transport molecules.

Trei