s ▁usually ▁requires ▁interaction ▁with ▁gen es ▁encoded ▁in ▁the ▁plant ▁cell ▁nucle us . ▁ ▁This ▁almost ▁seems ▁to ▁suggest ▁that ▁the ▁gen es ▁have ▁been ▁later ally ▁transferred ▁from ▁alg ae ▁to ▁the ▁animals . ▁DNA ▁ampl ification ▁experiments ▁on ▁E ly s ia ▁ch lor ot ica ▁adult s ▁and ▁eggs ▁using ▁V au cher ia ▁lit ore a ▁derived ▁prim ers ▁revealed ▁the ▁presence ▁of ▁ps b O , ▁an ▁alg al ▁nuclear ▁gene . ▁These ▁results ▁were ▁likely ▁an ▁arte fact , ▁as ▁most ▁recent ▁results ▁based ▁on ▁trans cript omic ▁analysis ▁and ▁sequ encing ▁of ▁genom ic ▁DNA ▁from ▁the ▁sl ug ' s ▁eggs ▁reject ▁the ▁hypothesis ▁that ▁later al ▁gene ▁transfer ▁supports ▁kle ptop last ▁lon ge vity . ▁Sac og loss ans ▁are ▁able ▁to ▁choose ▁which ▁method ▁of ▁feed ing ▁they ▁use . ▁The ▁switch ▁from ▁active ▁feed ing ▁to ▁photos yn thesis ▁in ▁sac og loss ans ▁is ▁triggered ▁by ▁the ▁short age ▁of ▁food ▁resource , ▁and ▁typically ▁not ▁preferred . ▁If ▁food ▁is ▁readily ▁available , ▁the ▁animal ▁will ▁act ively ▁consume . ▁Star v ation ▁periods ▁( period s ▁of ▁photos yn thesis ▁and ▁no ▁active ▁feed ing ) ▁vary ▁between ▁species ▁of ▁sac og loss ans ▁from ▁less ▁than ▁a ▁week ▁to ▁over ▁four ▁months , ▁and ▁photos yn thesis ▁is ▁used ▁as ▁a ▁last ▁resort ▁mechanism ▁to ▁avoid ▁mort ality . ▁Another ▁unclear ▁step ▁in ▁the ▁process ▁is ▁how ▁the ▁ch lor op last s ▁are ▁protected