Chapoton introduced an interesting family of polytopes called arbor polytopes, where a polytope Qτ is associated to any arbor τ. Chapoton conjectured that the polynomial h(τ) which counts lattice points in Qτ
Nearby in the stack
by number of nonzero entries is palindromic and unimodal. Athanasiadis, Xiao, and Yan recently proved that
h(τ)
is gamma-positive for a certain class of arbors they call octopuses. Since their proof was computational, they asked for one that is bijective. We present such a proof. We also extend their results by showing that
h(τ)
is gamma-positive for a larger class of arbors we call lopsided octopuses.