Tag: Larva

2-2I of thorax [FBbt_00001470]

Primary interneuron that develops from NB2-1 of the thorax. These neurons form a fascicle of about 10 axons that projects contralaterally through the anterior commissure. Unlike the 2-2I of abdomen, the 2-2I fascicle of thorax does not turn anteriorly after reaching the contralateral connective. See Bossing et al., (1996) for a diagram.

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3-1I of thorax [FBbt_00001480]

Primary interneuron that develops from neuroblast NB3-1 of the thorax. The projections of these interneurons form a fascicle that projects through the anterior commissure. Unlike the fascicle formed by abdominal 3-1I, it does not show any appreciable bifurcation in the contralateral connective. See Bossing et al., (1996) for a diagram.

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3-2Mar [FBbt_00001549]

Any larval motor neuron that develops from NB3-2 and fasciculates with the intersegmental nerve, exiting the ventral nerve cord via the anterior root. According to Schmid et al. (1999) there are 4 motorneurons which project to muscles: DA2, DO2, DO3, DO4 and DO5. According to Landgraf et al. (1997), the 4 motorneurons innervate: DO3-5 and DT1.

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5-2Ica1 [FBbt_00001497]

Primary interneuron originating from the neuroblast NB5-2 lineage whose projections form a bundle that projects through the anterior commissure, along its anterior border and immediately turns anteriorly upon reaching the contralateral connective. See Bossing et al., (1996) for a diagram.

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7-1M [FBbt_00001558]

Any embryonic/larval motor neuron (FBbt:00007675) that develops from some neuroblast NB7-1 (FBbt:00001380). According to Landgraf et al. (1997) and Schmid et al. (1999), several motorneurons are produced from NB7-1: MN-DA2/DA3, MN-DO1/DO2, MN-LL1, MN-VO4-6 and MN-VO4/5. This term was obsoleted because neurons classes were made for each of these motorneurons.

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A-subperineurial glial cell [FBbt_00001259]

A large subperineural glial cell of the embryo or larva that lies anterior to the anterior segment border and anterior commissure and medial to the longitudinal connective in each abdominal and thoracic neuromere, (Klambt and Goodman, 1991; Ito et al., 1995). It sends a process to the dorsoventral channel (Ito et al., 1995). These cells have different neuroblasts of origin in different neuromeres (Beckervordersandforth et al., 2008).

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A1-7 DA1 motor neuron [FBbt_00110220]

Motor neuron that innervates the internal dorsal acute muscle 1 of larval abdominal segments A1 to A7. Its dendritic arborization occupies the lateral domain of the ventral nerve cord neuropil. It exits the ventral nerve cord via the anterior root of the intersegmental nerve and innervates the DA1 muscle with type Ib boutons (Landgraf et al., 1997; Hoang and Chiba, 2001). By embryonic stage 16, it has a short contralaterally projecting neurite extending into the posterior commissure. It receives input from the contra- and ipsilateral larval A27h neuron. There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7. These neurons were identified in a EM reconstruction of a volume that includes the posterior half of abdominal segment 2 and abdominal segment 3, of a 12-24h old first instar larva. The number of connections was estimated from the publication figures. The number of input synapses was the following (number in brackets ipsilateral/contralateral): from A27h (10/10) (Schneider-Mizell et al., 2016).

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A1-7 DA2 motor neuron [FBbt_00002311]

Motor neuron that innervates the internal dorsal acute muscle 2 of larval abdominal segments A1 to A7 (Landgraf et al., 1997). Its dendritic arborization occupies the lateral and intermediate domains of the ventral nerve cord neuropil. It exits the ventral nerve cord via the anterior root of the intersegmental nerve and innervates the DA2 muscle with type Ib boutons (Landgraf et al., 1997; Hoang and Chiba, 2001). The muscle it innervates is one segment posterior to its soma (Zarin and Labrador, 2019). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7. This motor neuron is an exception to the class of motorneurons that innervate the internal dorsal muscles whose dendrites occupy the lateral neuropil; it has dendrites in the intermediate and lateral regions (Mauss et al., 2009). Based on cell body position, the DA2 motor neuron appears to correspond to the U2 neuron (personal communication by Matthias Landgraf - FBrf0221138), however, Zarin et al. (2019) report that the DA2 motor neuron corresponds to U3.

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A1-7 DA3 motor neuron [FBbt_00110233]

Motor neuron developing from the fourth ganglion mother cell that differentiates from neuroblast NB7-1. It innervates the internal dorsal acute muscle 3 (DA3) of larval abdominal segments A1 to A7. Its dendritic arborization occupies the lateral domain of the ventral nerve cord neuropil. It exits the ventral nerve cord via the anterior root of the intersegmental nerve and innervates the DA3 muscle with type Ib boutons (Landgraf et al., 1997; Hoang and Chiba, 2001). Its soma is in the segment anterior to the muscle it innervates (Kohsaka et al., 2012). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7. The DA3 motor neuron is likely to correspond to the U4 neuron. This is suggested by the cell body position and by extrapolating the observation that these neurons that extend their axons the furthest differentiate the earliest (personal communication by Matthias Landgraf - FBrf0221138).

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A1-7 DO1 motor neuron [FBbt_00002303]

U1 neuron of A1-7. It innervates dorsal oblique muscle 1 (DO1). Its dendritic arborization occupies the lateral domains of the ventral nerve cord neuropil. It exits the ventral nerve cord via the anterior root of the intersegmental nerve and innervates the DO1 muscle of the next posterior segment with type Ib boutons (Landgraf et al., 1997; Hoang and Chiba, 2001; Zarin and Labrador, 2019). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7. Based on cell body position, the DO1 motor neuron corresponds to the U1 neuron (personal communication by Matthias Landgraf - FBrf0221138).

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A1-7 DO2 motor neuron [FBbt_00110230]

Motor neuron that innervates the internal dorsal oblique muscle 2 of larval abdominal segments A1 to A7. Its dendritic arborization occupies the lateral domain of the ventral nerve cord neuropil. It exits the ventral nerve cord via the anterior root of the intersegmental nerve and innervates the DO2 muscle with type Ib boutons. There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7. Based on cell body position, the DO2 motor neuron appears to correspond to the U3 neuron (personal communication by Matthias Landgraf - FBrf0221138), however, Zarin et al. (2019) report that the DO2 motor neuron corresponds to U2.

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A1-7 DO3 motor neuron [FBbt_00110237]

Motor neuron that develops from the neuroblast NB3-2 lineage (Landgraf et al., 1997). It innervates the internal dorsal oblique muscle 3 (DO3) of larval abdominal segments A1 to A7. Its dendritic arborization occupies the lateral domain of the ventral nerve cord neuropil. It exits the ventral nerve cord via the anterior root of the intersegmental nerve and innervates the DO3 muscle with type Ib boutons (Landgraf et al., 1997; Hoang and Chiba, 2001). These neurons (at least in A1 to A4) die during metamorphosis (Banerjee et al., 2016). Its soma is in the segment anterior to the muscle it innervates (Kohsaka et al., 2012). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7.

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A1-7 DO4 motor neuron [FBbt_00110240]

Motor neuron that develops from the neuroblast NB3-2 lineage (Landgraf et al., 1997). It innervates the internal dorsal oblique muscle 4 (DO4) of larval abdominal segments A1 to A7. Its dendritic arborization occupies the lateral domain of the ventral nerve cord neuropil. It exits the ventral nerve cord via the anterior root of the intersegmental nerve and innervates the DO4 muscle with type Ib boutons (Landgraf et al., 1997; Hoang and Chiba, 2001). These neurons (at least in A1 to A4) die during metamorphosis (Banerjee et al., 2016). Its soma is located in the segment anterior to the muscle innervated (Kohsaka et al., 2012). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7.

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A1-7 DO5 motor neuron [FBbt_00110241]

Motor neuron that develops from the neuroblast NB3-2 lineage (Landgraf et al., 1997; Schmid et al., 1999). It innervates the internal dorsal oblique muscle 5 (DO5) of larval abdominal segments A1 to A7. Its dendritic arborization occupies the lateral domain of the ventral nerve cord neuropil. It exits the ventral nerve cord via the anterior root of the intersegmental nerve and innervates the DO5 muscle with type Ib boutons (Landgraf et al., 1997; Hoang and Chiba, 2001). These neurons (at least in A1 to A4) die during metamorphosis (Banerjee et al., 2016). Its soma is found in the segment anterior to the muscle it innervates (Kohsaka et al., 2012). Muscle DO5 is only present in A1-7. There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al ., 1999), we infer A1 motor neuron innervation patterns from those of A2-7.

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A1-7 dorsal motor neuron [FBbt_00002207]

Motor neuron that innervates the internal dorsal acute, dorsal oblique and LL1 muscles of larval abdominal segments A1 to A7 (Landgraf et al., 2003). It exits the ventral nerve cord via the posterior root of the intersegmental nerve. It is one of the common exciters of the A1-7 muscles, innervating the dorsal and LL1 muscles via type Is boutons (Mauss et al., 2009). It receives input from the ipsilateral larval A02b, A27j, eIN-4 (A03a1) and A27e and contralateral larval A08e1-3 local neurons and A31k neuron. Unlike other ISN neurons, its soma is located in the same segment as the muscles it innervates (Zarin and Labrador, 2019). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7. These neurons were identified in one EM reconstruction of abdominal segment 3 of a 12-24h old first instar larva (Heckscher et al., 2015; Schneider-Mizell et al., 2016). For Heckscher et al. (2015) only bilateral connections are reported. The number of identified input synapses was the following (number in brackets left/right): from A08e1 (1-4/1-7), A08e2 (1-4/1-7), A08e3 (1-4/1-7) (Heckscher et al., 2015). For Schneider-Mizell et al. (2016), the number of connections was estimated from the publication figures. The number of input synapses was the following (number in brackets left/right where available): from A02b (12/12), A27j (12/25), A03a1 (20/23), A27e (21), A31k (35/35) (Schneider-Mizell et al., 2016).

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A1-7 dorsal oblique muscle 5 [FBbt_00000613]

The ventral-most of the dorsal oblique muscles of A1-7. Following Bate (1993), larval hypodermal muscles are named for their orientation and numbered based on their order from dorsal to ventral or anterior to posterior. So, except where musculature is essentially identical between segments (as for A1-7, with a couple of exceptions for A1), serial homology should not be assumed on the basis of a shared name.

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A1-7 dorsal VUM motor neuron [FBbt_00002239]

Neuromodulatory motor neuron that innervates the internal dorsal acute and oblique muscles of larval abdominal segments A1 to A7 via type II boutons. It exits the ventral nerve cord via the posterior root of the intersegmental nerve and fasciculates with the ISNb or ISNd intersegmental nerve branches. These neurons have a virtually identical arborization pattern, shared with the lateral and ventral VUM neurons of A1-7. They arborize along and dorsal to the dorsal median fascicle and laterally along the dorsal lateral fascicle, invading the next anterior neuromere. In the dorsomedial neuropil, arborizations are sent into at least two (usually three) anterior neuromeres and the adjacent posterior neuromere (Selcho et al., 2012). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7.

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A1-7 DT1 motor neuron [FBbt_00110278]

Motor neuron developing from neuroblast NB3-2 lineage that innervates the dorsal transverse muscle 1 (DT1) of abdominal segments 1 to 7 (Landgraf et al., 1997). It exits the ventral nerve cord via the anterior intersegmental nerve root, fasciculates with the intersegmental nerve, and innervates the DT1 muscle with type Ib boutons (Landgraf et al., 1997; Hoang and Chiba, 2001). Although it innervates an external muscle, its soma is clustered with those of the internal muscle-innervating neurons in the segment anterior to the muscle innervated (Landgraf et al., 2003). Its dendritic arborizations are found with those of other external muscle-innervating neurons, connected via a long posterior projection (Landgraf et al., 2003). Following Landgraf et al., 1997, larval motor neurons are named according to the muscle they innervate. The same caveats therefore apply regarding inference of serial homology from nomenclature as for the muscles: Following Bate (1993), larval hypodermal muscles are named for their orientation and numbered based on their order from dorsal to ventral or anterior to posterior. So, except where musculature is essentially identical between segments (as for A1-7, with a couple of exceptions for A1), serial homology should not be assumed on the basis of a shared name.

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A1-7 lateral VUM motor neuron [FBbt_00002255]

Neuromodulatory motor neuron that innervates the lateral transverse muscles of larval abdominal segments A1 to A7 via type II boutons. It exits the ventral nerve cord via the segmental nerve and fasciculates with the SNa segmental nerve branches. These neurons have a virtually identical arborization pattern, shared with the dorsal and ventral VUM neurons of A1-7. They arborize along and dorsal to the dorsal median fascicle and laterally along the dorsal lateral fascicle, invading the next anterior neuromere. In the dorsomedial neuropil, arborizations are sent into at least two (usually three) anterior neuromeres and the adjacent posterior neuromere (Selcho et al., 2012). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7. In A2-7, these might also synapse to muscles 26 (VA1), 27 (VA2) and 29 (VA3) (Selcho et al., 2012).

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A1-7 LL1 motor neuron [FBbt_00110235]

Motor neuron developing from the fifth ganglion mother cell that differentiates from neuroblast NB7-1. It innervates the internal lateral longitudinal muscle 1 of larval abdominal segments A1 to A7. Its dendritic arborization occupies the intermediate domain of the ventral nerve cord neuropil. It exits the ventral nerve cord via the anterior root of the intersegmental nerve and innervates the LL1 muscle with type Ib boutons (Landgraf et al., 1997; Hoang and Chiba, 2001). Its soma is found in the segment anterior to the muscle it innervates (Kohsaka et al., 2012). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7. The LL1 motor neuron is likely to correspond to the U5 neuron. This is suggested by the cell body position and by extrapolating the observation that these neurons that extend their axons the furthest differentiate the earliest (personal communication by Matthias Landgraf - FBrf0221138).

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A1-7 LO1 motor neuron [FBbt_00110274]

Motor neuron developing from neuroblast NB3-3 lineage that innervates the external lateral oblique muscle 1 of abdominal segments 1 to 7. The motor neuron exits the ventral nerve cord via the segmental nerve root nerve fasciculating with the SNa nerve branch and innervates the LO1 muscle with type Ib boutons. There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7.

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A1-7 LT1 motor neuron [FBbt_00110263]

Motor neuron developing from neuroblast NB2-2 lineage that innervates the external lateral transverse muscle 1. It exits the ventral nerve cord via the segmental nerve root, fasciculating with the SNa nerve branch and innervates the LT1 muscle with type Ib boutons. There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7.

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A1-7 LT2 motor neuron [FBbt_00110266]

Motor neuron developing from neuroblast NB2-2 lineage that innervates the external lateral transverse muscle 2. It exits the ventral nerve cord via the segmental nerve root nerve fasciculating with the SNa nerve branch and innervates the LT2 muscle with type Ib boutons. There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7.

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A1-7 LT3 motor neuron [FBbt_00110269]

Motor neuron developing from neuroblast NB3-2 lineage that innervates the external lateral transverse muscle 3. It exits the ventral nerve cord via the segmental nerve root nerve fasciculating with the SNa nerve branch and innervates the LT3 muscle with type Ib boutons. There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7.

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A1-7 LT4 motor neuron [FBbt_00110272]

Motor neuron developing from neuroblast NB3-2 lineage that innervates the external lateral transverse muscle 4. It exits the ventral nerve cord via the segmental nerve root nerve fasciculating with the SNa nerve branch and innervates the LT4 muscle with type Ib boutons. There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7.

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A1-7 SBM motor neuron [FBbt_00110276]

Motor neuron developing from the neuroblast NB2-4 lineage that innervates the external segment border muscle of abdominal segments 1 to 7 (Schmid et al., 1999). It exits the ventral nerve cord via the segmental nerve SNa branch and innervates the SBM muscle of the same segment with type Ib boutons (Hoang and Chiba, 2001; Zarin and Labrador, 2019). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7.

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A1-7 V motor neuron [FBbt_00110302]

Neuromodulatory motor neuron that develops from the neuroblast 5-2 and innervates the ventral longitudinal muscle 1 (Landgraf et al., 1997). It fasciculates with the ISNb intersegmental nerve branch, innervating VL1 via type III boutons (Hoang and Chiba, 2001; Zarin et al., 2019). It soma is one segment anterior to the muscle it innervates, in the contralateral hemineuromere (Landgraf et al., 1997). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7.

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A1-7 VA1 motor neuron [FBbt_00110254]

Motor neuron that innervates the external ventral acute muscle 1 of larval abdominal segments A1 to A7. It exits the ventral nerve cord via the segmental nerve root, fasciculating with the SNc nerve branch. These neurons (at least in A1 to A4) die during metamorphosis (Banerjee et al., 2016). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7.

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A1-7 ventral motor neuron [FBbt_00002231]

Motor neuron that innervates the ventral oblique muscles VO1, 2, 4 and 5 and ventral longitudinal muscles VL1-4 of larval abdominal segments A1 to A7 via type Is boutons (Hoang and Chiba, 2001; Mauss et al., 2009). It exits the ventral nerve cord via the anterior root of the intersegmental nerve, fasciculating with the ISNb branch, and innervates muscles in the next posterior segment to its soma (Zarin and Labrador, 2019). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7.

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A1-7 ventral VUM motor neuron [FBbt_00002247]

Neuromodulatory motor neuron that innervates the internal ventral oblique and longitudinal muscles of larval abdominal segments A1 to A7 via type II boutons. It exits the ventral nerve cord via the posterior root of the intersegmental nerve and fasciculates with the ISNb or ISNd intersegmental nerve branches. These neurons have a virtually identical arborization pattern, shared with the dorsal and lateral VUM neurons of A1-7. They arborize along and dorsal to the dorsal median fascicle and laterally along the dorsal lateral fascicle, invading the next anterior neuromere. In the dorsomedial neuropil, arborizations are sent into at least two (usually three) anterior neuromeres and the adjacent posterior neuromere (Selcho et al., 2012). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7.

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A1-7 VL1 motor neuron [FBbt_00047470]

Motor neuron that innervates ventral longitudinal muscle 1 (VL1; muscle 12), in one of larval abdominal segments A1 to A7, via type Ib boutons (Hoang and Chiba, 2001). Its cell body is located contralateral to the muscle it innervates, the next anterior neuromere, and it fasciculates with the ISNb nerve branch (Hoang and Chiba, 2001; Kohsaka et al., 2012). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7.

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A1-7 VL2 motor neuron [FBbt_00110292]

Motor neuron of the larva that synapses to the ventral longitudinal muscle 2 (muscle 13) of A1-7 with a type Ib bouton. Its cell body is ipsilateral to the target muscle at the distal edge of the CNS (Hoang and Chiba, 2001). It fasciculates with the intersegmental nerve branch b (ISNb), which also contains other neurons that innervate ventrolateral internal muscles (Kohsaka et al., 2015). It innervates the muscle of the segment immediately posterior to its soma (Kohsaka et al., 2015).

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A1-7 VL3/4 motor neuron [FBbt_00002215]

RP3 motor neuron that innervates the internal ventral longitudinal muscles 3 and 4 of A1-7. Its dendritic arborization occupies the intermediate domain of the ventral nerve cord neuropil. It exits the ventral nerve cord via the anterior root of the intersegmental nerve fasciculating with the ISNb nerve branch. Its soma is located in the segment anterior to the muscle it innervates (Landgraf et al., 1997). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7.

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A1-7 VO1 motor neuron [FBbt_00002223]

RP4 neuron that innervates the internal ventral oblique muscle 1 (VO1; muscle 30) of segments A1-7. Its dendritic arborization occupies the intermediate domain of the ventral nerve cord neuropil. It exits the ventral nerve cord via the anterior root of the intersegmental nerve fasciculating with the ISNb nerve branch. Its soma is located in the segment anterior to the muscle it innervates (Landgraf et al., 1997). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7.

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A1-7 VO2 motor neuron [FBbt_00002199]

RP1 motor neuron of A1-7. Its dendritic arborization occupies the lateral domain of the ventral nerve cord neuropil. It exits the ventral nerve cord via the anterior root of the intersegmental nerve and innervates the VO2 muscle (Mauss et al., 2009) via type Ib boutons. Its cell body is located in the segment anterior to the muscle it innervates (Landgraf et al., 1997). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7. Innervation of muscle 14 makes this equivalent to the MN14-Ib neuron of Hoang and Chiba, 2001.

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A1-7 VO3 motor neuron [FBbt_00110284]

Motor neuron that develops from the neuroblast NB4-2 lineage. It innervates the internal ventral oblique muscle 3 of larval abdominal segments A1 to A7. Its dendritic arborization occupies the medial domain of the ventral nerve cord neuropil. It exits the ventral nerve cord via the anterior root of the intersegmental nerve, fasciculating with the ISNb nerve branch and innervates the VO3 muscle with type Ib boutons. These neurons (at least in A1 to A4) die during metamorphosis (Banerjee et al., 2016). There is little or no published literature specifically on innervation in A1 and so where equivalent muscles are present between A1 and A2-7 (Landgraf et al., 1997; Schmid et al., 1999), we infer A1 motor neuron innervation patterns from those of A2-7.

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A2-7 VT1 motor neuron [FBbt_00110281]

Motor neuron developing from neuroblast NB4-1 lineage that innervates the ventral transverse muscle 1 of abdominal segments 2 to 7. It migrates medially and posteriorly during embryonic development (Schmid et al., 1999). It follows the transverse nerve and synapses to the VT1 muscle in the anterior part of the of the next posterior segment via type Ib boutons (Landgraf et al., 1997; Zarin et al., 2019). VT1 is only found in A2-7 segments (Zarin et al., 2019). Following Landgraf et al., 1997, larval motor neurons are named according to the muscle they innervate. The same caveats therefore apply regarding inference of serial homology from nomenclature as for the muscles: Following Bate (1993), larval hypodermal muscles are named for their orientation and numbered based on their order from dorsal to ventral or anterior to posterior. So, except where musculature is essentially identical between segments (as for A1-7, with a couple of exceptions for A1), serial homology should not be assumed on the basis of a shared name.

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