a: Supposed endosymbiosis of an organism containing type-2 lipases. As a result the allosteric regulation mechanism controls the concentration of products of hydrolysis and fat can be accumulated. This is a mutualistic symbiosis, as the effect is beneficial to both endo- and exosymbiont.; b: A new kind of organism results from genetic combination of the symbionts. The ability to accumulate and mobilize storage fat is maintained and provides a major benefit due to energy homeostasis.