Diagonal and off-diagonal flavor and conserved charge susceptibilities
reveal the prevalent degrees of freedom of heated strongly interacting matter.
Various volume independent ratios of susceptibilities are explored and related
by the Gell-mann Okubo formula. Results obtained from lattice simulations are
compared with various model estimates in an effort to weed down various possible
pictures of a quark gluon plasma. We argue that the vanishing of the off-diagonal
quark flavor susceptibilities and its derivatives with respect to chemical
potential, at temperatures above 1.5 Tc, can only be understood in a picture of a
gas or liquid composed of quasi-particles which carry the same quantum numbers as
quarks and antiquarks. A potential new observable, blind to neutral and non-strange
particles, is introduced and related via isospin symmetry to the ratio of
susceptibilities of baryonic strangeness to strangeness generated in the
excited matter created at RHIC.