The Ol1mpiad: concordance of behavioural faculties of stage 1 and stage 3Drosophilalarvae

Abstract

Mapping brain function to brain structure is a fundamental task for neuroscience. For such an endeavour, the larva is simple enough to be tractable, yet complex enough to be interesting. It features about 10,000 neurons and is capable of various taxes, kineses and Pavlovian conditioning. All its neurons are currently being mapped into a light-microscopical atlas, and Gal4 strains are being generated to experimentally access neurons one at a time. In addition, an electron microscopic reconstruction of its nervous system seems within reach. Notably, this electron microscope-based connectome is being drafted for a stage 1 larva - because stage 1 larvae are much smaller than stage 3 larvae. However, most behaviour analyses have been performed for stage 3 larvae because their larger size makes them easier to handle and observe. It is therefore warranted to either redo the electron microscopic reconstruction for a stage 3 larva or to survey the behavioural faculties of stage 1 larvae. We provide the latter. In a community-based approach we called the Olmpiad, we probed stage 1 larvae for free locomotion, feeding, responsiveness to substrate vibration, gentle and nociceptive touch, burrowing, olfactory preference and thermotaxis, light avoidance, gustatory choice of various tastants plus odour-taste associative learning, as well as light/dark-electric shock associative learning. Quantitatively, stage 1 larvae show lower scores in most tasks, arguably because of their smaller size and lower speed. Qualitatively, however, stage 1 larvae perform strikingly similar to stage 3 larvae in almost all cases. These results bolster confidence in mapping brain structure and behaviour across developmental stages.

The complete connectome of a learning and memory centre in an insect brain

“…Learning experiments were performed as described in refs 8, 10, 42, 67. The fly strain PGMR58E02-GAL4attP2 (Bloomington Stock Center number 41347) and the attP2 control strain were crossed to P20XUAS-IVS-CsChrimson.mVenusattP18 (Bloomington Stock Center number 55134).…”

“…1a). L1 are foraging animals capable of all behaviours previously described in later larval stages 10 , including adaptive behaviours dependent on associative learning 7,9 (Fig. 1b).…”

Segment-Specific Optogenetic Stimulation inDrosophila melanogasterwith Linear Arrays of Organic Light-Emitting Diodes

“…19,20 For excitation, we used CsChrimson, a cation channel with peak sensitivity in the red spectral region, 21 which has found widespread application in both flies and mice. [23][24][25][26] For inhibition, the anion conducting GtACR2 was used, which efficiently suppresses neural activity in response to blue light, 22 and has been used in previous studies to control Drosophila larval locomotion and to study the visual system. 27,28 In contrast to more traditional genetic inhibitors such as tetanus toxin, 29 and temperature sensitive dynamin proteins (shibire TS ), 30 GtACR2 enables fast, reversible inhibition at low light intensities from 2 µW mm -2 upwards.…”

The complete connectome of a learning and memory center in an insect brain

“…1a). L1 are foraging animals capable of all behaviors previously described in later larval stages 10 , including adaptive behaviors dependent on associative learning 7;9 (Fig. 1b).…”