larvae. Clawed frog larvae are filter feeders and collect nutrients from plankton, allowing adult frogs that consume the tadpoles to have access to these nutrients. This allows clawed frogs to survive in areas that have little to no other food sources. Clawed frogs are nocturnal and most reproductive activity and feeding occurs after dark. Male clawed frogs are very promiscuous and will grab onto other males and even other species of frogs. Male frogs that are grasped will make release calls and attempt to break free. If not feeding, clawed frogs will just sit motionless on top of the substrate or floating at the top with their heads sticking out. Biology Thyroid The X. laevis liver responds to low temperatures by increasing production of type II iodothyronine deiodinase . This in turn spurs the thyroid to increase T to increase body temperature. (This T increase also induces germ cell apoptosis, mediated through genes left over from tadpole metamorphosis.) The effects of provocation of T hormone release are broadly differentiated by where it starts: If centrally, within the mediobasal hypothalamus, then it stimulates seasonal testicular growth; if peripherally, then testicular regression and cold-season thermogenesis. These observations are regarded as widely applicable across vertebrate thyroid systems. Lipidomics The lipidomics of Xenopus oocytes has been studied by Tian et al 2014 and Phan et al 2015. In the wild In the wild, X. laevis are native to wetlands, ponds, and lakes across arid/semiarid regions of Sub-Saharan Africa. X. laevis and X. muelleri occur along the western boundary of the Great African Rift. The people of the sub-Saharan are generally very familiar with this frog, and some cultures use it as a source of protein, an aphrodisiac, or as fertility medicine. Two historic outbreaks of priapism have been linked to consumption of frog legs from frogs that ate insects containing cantharidin. X. laevis in the wild are commonly infected by various parasites, including monogeneans in the urinary bladder. Use in research Xenopus embryos and eggs are a popular model system for a wide variety of biological studies, in part because they have the potential to lay eggs throughout the year. This animal is widely used because of its powerful combination of experimental tractability and close evolutionary relationship with humans, at least compared to many model organisms. For a more comprehensive discussion of the use of these frogs in biomedical research, see Xenopus. Xenopus laevis