larval thoracic NB5-6 primary interneuron apterous-expressing neuron of the lateral cluster of the thorax 2014-04-23T17:14:06Z VFB:FBbt_00110868 Ap cluster FBbt:00110868 Primary interneuron that expresses apterous and is found in a relatively lateral position within an embryonic or larval thoracic neuromere (Lundgren et al., 1995). There are four of these neurons per thoracic hemisegment and they are born at the end of the primary lineage of NB5-6T, with Ap1 generated at stage 13, followed by Ap2, Ap3 and Ap4 (Baumgardt et al., 2007; Baumgardt et al., 2009). They are generated directly from the neuroblast, without a ganglion mother cell intermediate (Baumgardt et al., 2009). Non-thoracic segments may have dorsal and ventral Ap neurons, but no lateral clusters. ap cluster Ap cluster neuron fly_anatomy.ontology