  The Dulfo-Serganova functors DS are tensor functors relating representations
of different Lie superalgebras. In this paper we study the behaviour of various
invariants, such as the defect, the dual Coxeter number, the atypicality and
the cores, under the DS-functor. We introduce a notion of depth playing the
role of defect for algebras and atypicality for modules. We mainly concentrate
on examples of symmetrizable Kac-Moody and Q-type superalgebras.
