The velvet worm brain unveils homologies and evolutionary novelties across panarthropods

Martin, Christine; Jahn, Henry; Klein, Mercedes; Hammel, Jörg U.; Stevenson, Paul A.; Homberg, Uwe; Mayer, Georg

doi:10.1186/s12915-021-01196-w

Table 1 Glossary of neuroanatomical terms for studies of Onychophora. Terms that are highlighted in bold and preceded by arrows are defined in corresponding fields. Novel introduced terms are indicated by asterisks (*). Languages of foreign synonyms are specified in square brackets. Note that correspondent terms do not necessarily imply homology with homonymous structures in arthropods and other animals. Whenever possible, the nomenclature follows the terms and definitions suggested by Ito et al. [49] for insects and Richter et al. [20] for invertebrates in general

From: The velvet worm brain unveils homologies and evolutionary novelties across panarthropods

Suggested term for neuroanatomical structure (of one brain hemisphere or body side)	Reference(s) for suggested neuroanatomical term	Abbreviation	Figures	Description	Synonyms (plural and singular forms were adapted to terminology used herein)	Reference(s) for synonyms
Antennal nerve cord	[33]	ANC	1a, c, 11a, c, 12a–c, 13 and Additional file 1: Fig. S1a–c and Additional file 5: Fig. S5a–d	Prominent neuropil and bundle of fibres supplying each antenna; it begins in antennal tip, traverses antennal shaft and continues as →antennal neuropil in →brain; it is true neuropil, as it contains synapses revealed by transmission electron microscopy [32] and anti-synapsin immunolabelling (this study), and shows medullary organisation, as it is accompanied by somata [13]; this combination of neuropil and medullary organisation speaks against designation of this structure as nerve but rather as nerve cord	Antennalnerv [German]	[27, 28, 31, 50,51,52,53]
					Antennal nerve	[15, 32, 34, 40, 43, 48, 54,55,56,57,58,59,60,61,62,63,64,65,66,67,68]
					Antennal neuropil	[57]
					Antennal tract	[18, 32, 38, 39, 43, 47, 48, 69,70,71,72]
					Antennalstrang [German]	[27, 28, 30, 31, 51]
					Antennary nerve	[25, 73,74,75,76]
					Antennennerv [German]	[73, 74]
					Anterior appendage tract	[13]
					Dorsolateral lobe/horn	[25]
					Frontal appendage nerve	[45]
					Frontal appendage nerve bundle	[75]
					Fühlernerv [German]	[76]
					lobe antennaire [French]	[26]
					Lobus antennalis + Tractus antennalis [Latin]	[27]]
					nerf antennaire [French]	[26, 77]
					Nerve strand of the antenna	[65]
					nervo antenna [Portuguese]	[78]
					Nervus antennalis [Latin]	[30, 53, 79]
					Tentakelnerv [German]	[80]
Antennal neuropil	[57]	ANP	2, 4a–c, 5b, 6b, 7a', b', 8a, d, 10b–e, 1a–d, 12a–c, 13 and Additional file 1: S1a–c, Additional file 2: Fig. S2b and Additional file 5: Fig. S5a, b, d	Dorsolateral neuropil in →brain, part of each brain hemisphere; it is continuation of →antennal nerve cord within brain; it is fused ventrally with →subantennal neuropil and posteriorly with →posterior dorsal neuropil and sends off fibres to →auxiliary neuropil of →central body	Antennalfaserstrang [German]	[51]
					Antennal lobe	[32, 34, 39, 43, 47, 48, 54, 56, 65, 69]
					Antennal nerve	[15, 34, 40, 48, 55, 57,58,59, 66,67,68]
					Antennal nerve cord	[33]
					Antennalstrang [German]	[27, 28, 30, 31, 51]
					Antennal tract	[18, 34, 38, 39, 43, 47, 56, 59, 69,70,71,72]
					Antennennerv [German]	[52]
					Anterior appendage tract	[13]
					crête dorso-laterale [French]	[26]
					Dorsolateral lobe/horn	[25, 81]
					Frontal appendage ganglion	[45, 75]
					Lateral brain neuropil	[17, 48, 69]
					lobe antennaire [French]	[26]
					Lobus antennalis + Tractus antennalis [Latin]	[27]
					Nerve cord of pre-ocular frontal appendage	[45]
					Postglomerular lateral neuropil	[13]
					Ventrolateral horn	[25]
Anterior division (of central body)	[38]	CBA	2, 3, 5a, b and 13	Anterior subunit of →central body, which contains looping neurites forming →outer lamina and →inner lamina; fuses laterally with →posterior division at ventral part of central body	Anterior lamina	[17, 48, 69]
					Lame antérieure du bourrelet dorsal [French]	[26]
					lamina anterior [Latin]	[32, 54, 65]
					Lamina anterior des Zentralkörpers [Latin + German]	[31]
					vordere Lamelle des gestreiften Körpers [German]	[28]
					vorderer Zentralkörperteil [German]	[27]
Auxiliary neuropil*	–	CB-AN	3, 13 and arrowheads in 5a, d, e	Small cylindrical neuropil located on ventral side of →central body and enclosed by →inner lamina; it receives fibres from →antennal neuropil	–	–
Brain	[13, 17, 25, 32,33,34, 37,38,39,40, 42, 43, 45, 47, 48, 54,55,56,57, 59, 61,62,63, 65,66,67,68,69,70,71,72, 75, 81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98]	BR	1a and Additional files 1: Fig. S1a–c	Anterodorsal part of central nervous system consisting of left and right brain hemispheres, including cell body rind and brain neuropils; it is composite, bipartite structure (=syncerebrum sensu [20]) composed of →protocerebrum (belonging to 1st body segment) and →deutocerebrum (belonging to 2nd body segment); it accordingly innervates two pairs of cephalic appendages, including antennae (via → antennal nerve cords), and jaws (via → jaw nerves); it is associated posteriorly with →circumpharyngeal nerve cords	Bilobed cephalic ganglion	[99]
					Bilobed supra-oesophageal ganglia	[63]
					Cephalic ganglia	[100]
					Cephalic ganglia [Russian: головные узлы]	[101]
					Cerebral ganglion	[102]
					cerebro [Portuguese]	[78]
					cerveau [French]	[26, 103, 104]
					ganglion céphalique [French]	[101, 102]
					ganglions céphaliques [French]	[26]
					ganglions sus-œsophagiennes [French]	[105]
					ganglions cérébroïdes [French]	[106]
					gánglios cerebroídes [Spanish]	[107]
					Gehirn [German]	[27, 28, 30, 31, 51,52,53, 73, 79, 108,109,110,111]
					Kopfganglion [German]	[112]
					Oberschlundganglion [German]	[51]
					Oberschlundganglionmasse [German]	[29]
					paarige Gehirnganglien [German]	[76]
					paarige Oberschlundganglien [German]	[50]
					paarige Schlundganglien [German]	[76]
					paire de gros ganglions sus-œsophagiens [French]	[77]
					paired cerebral masses	[100]
					Schlundganglion [German]	[113]
					supra-oesophageal ganglia	[82, 114]
					supra-œsophageal ganglia	[25, 81, 115]
					supra-oesophageal ganglion	[63]
Brain commissures 1–3*	–	BRC 1–3	2, 3, 7a–c, 11c, d, 13 and arrowheads and arrows in Additional file 3: Fig. S3a–f	Bundles of contralateral fibres crossing →protocerebrum; brain commissures 1 and 2 link both →antennal neuropils; they, circumvent →pedunculus and follow →lobes of →mushroom body to →brain midline where they cross to contralateral brain hemisphere; brain commissure 3 is situated anterior to brain commissures 1 and 2 and links both →subantennal neuropils; it then splits in two branches before proceeding to contralateral brain hemisphere	Accessory lobes	[32, 33, 48, 69]
					Accessory stalks	[32, 54, 65]
					Heterolateral commissures	[33, 42]
					Heterolateral mushroom body lobes	[33]
					Nebentrabekel [German]	[30]
Central body	[17, 32, 38,39,40, 48, 54, 56, 62, 65, 67,68,69, 84, 86]	CB	2, 3, 4b, 5a–e, 6a, 10a, d, e, 11a, b and 13	Dorsalmost, midline neuropil located posterior to →frontal body; it is arcuate in shape and consists of →outer lamina and →inner lamina, resulting in stratified appearance; inner lamina encloses→auxiliary neuropils; →anterior division and →posterior division fuse at ventral part of central body; posterior division is associated posteriorly with additional posterior stratum, which receives fibres from →optic neuropil	Arcuate body	[33, 42, 57, 84, 96]
					bourrelet dorsal [French]	[26]
					Central complex	[75]
					corpo central [Portuguese]	[78]
					corpo estriado [Portuguese]	[78]
					corpus centrale [Latin]	[43]
					corpus striatum [Latin]	[32, 54, 56]
					Corpus striatum [Latin]	[27, 28, 30]
					dorsal cap	[90]
					gestreifter Körper [German]	[27, 28, 30]
					Posterodorsal lobe	[25]
					Zentralkörper [German]	[27, 30, 31, 52, 53, 110, 111]
Central neuropil	[13, 17, 32, 34, 37, 38, 47, 48, 55, 56, 59, 65, 69, 70, 86, 98]	CN	5e, 11b, 12a–c and Additional file 5: Fig. S5a	Midline-spanning neurite region, which is located anterior to →posterior dorsal neuropil and →posterior ventral neuropil and receives fibres from →antennal neuropil	Central brain neuropil	[15, 48, 55, 59, 70]
					Central fibrous mass	[56]
					Central lobe	[25, 81, 82]
					Median lobe	[25]
					Zentralfasermasse [German]	[51]
Circumpharyngeal nerve cord*	–	CNC	1a, 2, 11a–d, 12a–c, 13 and Additional file 1: Fig. S1a, c and Additional file 5: Fig. S5a–d	Dorsoventral medullary nerve cord connecting brain hemispheres with →ventral nerve cords; it entirely lacks →dorsal commissures and is medially associated only with →subpharyngeal commissure; it laterally gives rise to →slime papilla nerves that lie posterior to →lip nerve 3, and anterior to →salivary gland nerve; circumpharyngeal nerve cord consists of outer cell body rind and inner neuropil	Circumoesophageal connective	[13, 32, 34, 56, 66, 91, 97]
					Circumpharyngeal connective	[92]
					Circumpharyngeal medullary connective	[68]
					commissure œsophagienne [French]	[26]
					Connecting cord	[38, 39, 55, 69, 86]
					Connecting piece	[40, 48, 72]
					Connective of the brain	[93]
					Connective to the ventral nerve cord	[65]
					Hinterschlundkommissur [German]	[31]
					Konnektivstrang der Schlundganglien [German]	[27]
					longitudenal connective	[66]
					Oesophageal commissure	[25, 81]
					Oesophageal commissure	[114]
					Schenkel des Mundringes/Nervenringes [German]	[76]
					Schlundkommissur [German]	[27]
					Schlundkonnektiv [German]	[28,29,30,31, 53, 74, 110]
					Stomodeal connective	[43]
Deutocerebral neuropil*	–	DN	11a, b, 12a–c, 13 and Additional file 5: Fig. S5b	Midline-spanning neurite region, which is located posterior to →posterior dorsal neuropil and appears as bump-like structure on posterior surface of brain neuropils; it is assigned to →deutocerebrum, as it receives fibres from neurons associated with →jaw nerves [15]	–	–
Deutocerebrum	see e.g. [15, 30, 48, 69]	DE	13 and Additional file 1: Fig. S1b, c	Part of →brain associated with →jaw nerves and belonging to second head segment; it consists of cell body rind and neuropil and is located posterior to →protocerebrum; it contains →deutocerebral neuropil as its only neuropil region	Frequently used term; synonyms not listed, as deutocerebral borders are ambiguous and inconsistent throughout the literature	–
Dorsal commissures*	–	DC	1d	Serially repeated bundles of neurites connecting →ventral nerve cords; each dorsal commissure projects laterally and proceeds dorsally, where they connect ventral nerve cords of both hemispheres; dorsal commissures link →dorsolateral trunk nerves and →heart nerve	Dorsal nerv	[43]
					Interpedalnerv [German]	[51]
					Interpedal nerve	[43]
					Interpedalnerv + Postpedalnerv + Präpedalnerv [German]	[29, 31, 51]
					Interpedal nerve + postpedal nerve + prepedal nerve	[56]
					Lateral commissure	[90]
					Lateral nerve	[82]
					Laterodorsal nerve	[95]
					motorischer Randnerv + Ringenerv + Postpedaler Nerv 1 und 2 [German]	[28]
					Nerve to segment	[91]
					Peripheral nerve	[41]
					Ring commissures	[14, 17,18,19, 37,38,39,40, 48, 68, 69, 116]
					Ringkommissur [German]	[111]
Dorsolateral trunk nerve*	–	DTN	–	Anteroposterior axon bundle proceeding in each dorsolateral region of trunk; it is crossed by and probably associated with numerous →dorsal commissures; its anterior and posterior extents are unknown	Dorsolateral bundle	[65]
					Dorsolateral nerve	[37, 48, 69]
					Dorsolateralnerv [German]	[111]
					Lateral bundle of nerve fibres	[117]
Fascicles of globuli cells*	–	FBC	2, 3, 6a, 7a–c, 11a, c, d, 13; arrows in 6a and Additional file 5: Fig. S5b; arrows in Fig. S2b	Fascicle-like, anteriormost neurite subunit of →mushroom body receiving fibres from →globuli cells; digitiform branches converge to four major branches, which then join →pedunculus; we refrain from using the term calyx because mushroom body fascicles of onychophorans apparently lack synaptic terminals and differ substantially in their morphology from calyces described for insects [118, 119]	Calyx	[17, 32, 33, 42, 48, 54]
					Globulibündel [German]	[27]
					Neurite der Globulizellen [German]	[31]
					masse médullaire [French]	[26]
					Stalks	[32]
					Stiele [German]	[51]
					Stiele der Globulizellen [German]	[31]
					Stielkomplex [German]	[30]
Frontal body*	–	FB	2, 3, 4a, 5c–e, 11a, b, 13 and Additional file 5: Fig. S5a, b	Peanut shaped, anteriormost midline neuropil located anterodorsally within →protocerebrum anterior to →central body; it contains prominent anterior and posterior strata with relatively high numbers of synapses	Anterior brain neuropil	[48, 69]
					Anterior neuropil	[38]
					Bridge	[32, 54, 62, 65]
					bourrelet médullaire antérieur [French]	[26]
					Dorsal superior protocerebrum	[33]
					Frontal brain neuropil	[55]
					Frontal brain neuropil	[17]
					Protocerebralbrücke [German]	[30, 53]
Globuli cells	[33, 42, 48]	GC	arrowheads in Additional file 2: S2a, c	Dense accumulation of somata within anterior cell body rind at anterior border of →brain; their axons innervate corresponding →fascicles of globuli cells of →mushroom body	Anterior cell masses	[56]
					Globule cells	[32]
					Globuli	[43, 56]
					Globuli [German]	[28, 50, 51, 53, 110]
					Globuligruppen [German]	[31]
					Globulipartie [German]	[27]
					Globulizellen [German]	[30]
					masse ganglionnaire antérieur [French]	[26]
Heart nerve	[14, 17, 37, 38, 68, 69]	HAN	–	Anteroposterior, dorsomedian axon bundle associated with dorsal wall of heart within trunk; it is linked with →dorsolateral trunk nerves and →ventral nerve cords via → dorsal commissures; its anterior and posterior extents are unknown	Dorsal bundle of nerve fibres	[117]
					Dorsal nerve	[48]
					Dorsal nerve bundle	[65]
					Median cardiac nerve	[120]
					Herznerv [German]	[111]
Hypocerebral organ	[15, 34, 38,39,40, 48, 57, 61, 69,70,71, 97, 121]	HO	1c, 4c and Additional file 1: Fig. S1a	Vesicle-like structure attached to ventral surface of each brain hemisphere; its function is unknown, although it has been suggested to play endocrine role (e.g. [97, 104, 122])	Anhang des Kopfganglions [German]	[112]
					Appendage of the ventral surface of the brain	[25]
					Brain appendage	[60]
					Cerebral grooves	[123]
					Hypocerebral gland	[98]
					Hypocerebralorgan [German]	[50, 79, 111]
					Infracerebral organ	[34, 56, 63, 124,125,126]
					Infracerebral vesicle	[126]
					Infracerebral organ [Russian: инфра-церебральный орган]	[127]
					Infracerebralorgan [German]	[28, 50, 53]
					Infrazerebralorgan [German]	[51]
					kleiner Körper [German]	[76]
					organe ventral [French]	[26]
					organ ventraux du cerveau + ganglion intermediare [French]	[128]
					organe infracérébral [French]	[104, 122, 129]
					organe infra-cérébral [French]	[130]
					pear-shaped body	[43]
					spherule inférieure	[77]
					spherule infra-cervicale [French]	[131]
					Ventral appendage	[25, 81, 82]
					Ventral appendage of the brain	[28]
					Ventral body	[114]
					ventraler Gehirnanhang [German]	[91]
					Ventral lobe	[13, 34, 56]
					Ventral organ	[34, 43, 60]
					Ventralorgan [German]	[30, 52, 53, 73, 80, 108, 110, 132]
					Ventral protuberance of brain	[25, 81]
Inner lamina*	–	CB-IL	2, 3, 4c, 5a, c–e and 13	Neurite network in central part of →central body surrounded by →outer lamina; it shows inverted anteroposterior arrangement in →anterior division and →posterior division and encloses ventrally →auxiliary neuropils	–	–
Jaw nerve	[15, 39, 40, 48, 67,68,69]	JAN	1d, 2, 12a–c, 13 and Additional file 5: Fig. S5a–d	Axon bundle innervating each jaw (i.e. specialised limb of 2nd head segment) and associated with →deutocerebrum; it projects laterally at transition between →brain and →circumpharyngeal nerve cord, then finally bifurcates and runs ventrally to enter jaw	Jaw retractor muscle nerve	[95]
					Kiefernerv [German]	[28]
					Mandibelnerv [German]	[27, 31, 53, 74, 110]
					Mandibularnerv [German]	[28, 51]
					Mandibular nerve	[56]
					nerf des muscles mandibulaires [French]	[77]
					nerf mandibulaire [French]	[26]
					Nerve 11	[13]
					Nerve of feeding claw	[61]
					Nerve of the jaw	[25, 43, 81, 82, 126]
					Nerve to jaw	[25, 81, 82, 114]
					Nerve to jaw muscle	[91]
					Nervus mandibulairs [Latin]	[31, 53, 79]
Leg nerves	[3, 14, 17,18,19, 37,38,39, 41, 48, 68, 69, 116, 133, 134]	LEN	1c and d	Axon bundles innervating trunk limbs; each leg is supplied by anterior and posterior leg nerves that originate laterally from →ventral nerve cord and are segmental structures; associated somata are located on opposite side of nerve cord to bases of leg nerves [18]	Extremitätennerv [German]	[53, 79]
					Fußnerv [German]	[28, 29, 51, 135]
					nerf de patte [French]	[77]
					Nerve of walking leg	[40]
					Nerve to feet	[25, 81, 114, 115]
					Pedal nerve	[25, 43, 56, 82]
					Pedalnerv [German]	[29, 31]
Lip nerve 1*	–	LIN 1	1c, d and 2	Axon bundle innervating one of two anteriormost lip papillae; it originates at dorsal side of →brain, proceeds anteriorly, bends ventrally anterior to brain and finally innervates lip papilla; its associated somata are located within posterior →protocerebrum [40]	Anterior labial nerve	[56]
					First pair of lip papillae nerve	[48]
					hinterer Nerv des Mandibularsomits [German]	[28, 51]
					Lateral dorsal nerve	[43]
					Lip papillae nerve 1	[39, 40, 48, 69]
					nerf sympathique allant au papille du plafond buccal [French]	[77]
					nerve 7	[13]
					Nervus labialis anterior [Latin]	[30, 53]
					oral nerve	[38]
Lip nerve 2*	–	LIN 2	1d, 2, 12a–c, 13 and Additional file 5: Fig. S5c	Axon bundle innervating lateral lip papillae; it originates ventrolaterally from →protocerebrum and proceeds ventrally to innervate lip papillae 2–5 of corresponding hemisphere (in E. rowelli); it is exclusively sensory [40]	Labialnerv [German]	[28, 51]
					Labralnerv + oraler Ringnerv [German]	[74]
					Labral nerve + oral ring nerve	[91]
					Lateral labial nerve	[56]
					Lip papillae nerve 2	[39, 40, 48, 69]
					Lippennerv [German]	[28]
					Mundlippennerv [German]	[27, 31, 110]
					nerf labial [French]	[77]
					Nerve 8	[13]
					Nerve to circumoral fold	[43]
					Nervus labialis lateralis [Latin]	[30, 53]
					Oral nerve	[38]
					Second pair of lip papillae nerve	[48]
Lip nerve 3*	–	LIN 3	12c and 13	Axon bundle innervating posterior lip papillae; it originates from →circumpharyngeal nerve cord anterior to →slime papilla nerves, proceeds anterior and innervates lip papillae 2–8 (8^th is unpaired in E. rowelli); its associated somata are located in →deutocerebrum and along circumpharyngeal nerve cord [40]	Lip papillae nerve 3	[39, 40, 48, 69]
					nerf de parois périlabiales [French]	[77]
					Nerve 12	[13]
					Nerve leading tot o the mouth lips	[68]
					Oral nerve	[38]
					Third pair of lip papillae nerve	[48]
Lobes (of the mushroom body)	[17, 33, 38, 42, 48, 86]	LO	2, 3, 4b, c, 6a, c, 8a, 13 and Additional file 3: Fig. S3a	Stipe of →mushroom body associated with →pedunculus; lobes are composed of four subcompartments including δ-lobe, λ-lobe, μ-lobe, and v-lobe	Columns	[32]
					Gehirntrabekel [German]	[27, 28, 30, 31]
					Gehirn-Trabekel [German]	[51]
					lames ventrales [French]	[26]
					Peduncle	[43]
					Stalk	[32, 54, 65]
					Trabeculae [Latin]	[53, 110]
					Trabekel [German]	[28]
					ventral lamellae	[90]
Macroglomerulus*	–	MG	4a, 8a, c and 13	Largest spherical subunit of →olfactory lobe; it is medianmost →olfactory glomerulus located in posterior part of olfactory lobe	Large glomerulus	[32]
Median lobe*	–	ML	11d, 12a, c and Additional file 5: Fig. S5a–d	Neuropil in the anterior ventral median brain; it emanates from →subantennal neuropil as a protrusion with tapered tip and receives fibres from →olfactory fascicles 1–3	–	–
Microglomeruli*; singular: microglomerulus	–	MIG	2, 3, 8a, b, e, f, 13 and Additional file 4: Fig. S4c, d	Diminutive, point-like accumulations of neurite terminals situated anterior to →olfactory lobes; they are embedded within →subantennal neuropil; synapsin staining reveals presence of multiple synaptic sites in each microglomerulus	–	–
Mushroom body	[13, 17, 32, 33, 38, 39, 45, 48, 54, 55, 57, 68,69,70, 108, 111, 112]	MB	2, 3, 4b, c, 6a–c and 13	Ventralmost neuropil of →brain associated with →subantennal neuropil and consisting of →fascicles of globuli cells, →pedunculus and four →lobes; fascicles receives fibres from →globuli cells; it is linked via → ponticulus to →central body	corpus pedunculatum [Latin]	[30,31,32, 43, 56, 65, 68, 96]
Mushroom body		MB	2, 3, 4b, c, 6a–c and 13		Pilzkörper [German]	[111]
Nephridial nerves	[14, 48, 69]	NEN	–	Axon bundle innervating nephridia; it arises from →ventral nerve cord, follows proximally specific →ventral commissure, and finally turns back distally to pass beneath ventral nerve cord and to join nephridial duct; nephridial nerves show bilateral and segmental arrangement [14]	–	–
Olfactory fascicles 1–4*	–	OLF	2, 3, 4a, 8a, b and 13	Neurite bundles emanating from →olfactory lobes, olfactory fascicles 1–3 circumvent →mushroom body and join →median lobe of brain neuropil region of ipsilateral brain hemisphere, whereas olfactory fascicle 4 connects to v-lobe and δ-lobe of mushroom body	faisceau de fibrilles [French]	[26]
					Fasciluli [Latin]	[110]
					fasciculi glomeruli [Latin]	[27]
					Fasciculi glomeruli [Latin]	[28]
					Projections	[33]
					Verbindungen [German]	[31, 53, 110]
Olfactory glomeruli; singular: olfactory glomerulus	[33, 38, 42]	OLG	2, 3, 4a, 5a–d, f, 13 and Additional file 4: Fig. S4a, b	Synaptic complexes, ball- or knot-like subunits of →olfactory lobe containing terminals of olfactory receptors with numerous other synaptic sites; most olfactory glomeruli are of similar size except for →macroglomerulus	Antennal glomeruli	[15, 17, 32, 34, 40, 42, 43, 48, 54, 65, 66, 68, 69]
					Antennalglomeruli [German]	[30, 31, 50, 53, 110, 111]
					Anterior appendage glomeruli	[13]
					glomérules olfactifs [French]	[26]
					Glomeruli	[33, 42, 51]
					Glomeruli [German]	[27, 28, 51]
					Glomeruli of the anterior appendage	[13]
Olfactory lobe	[33, 38, 42, 48, 57, 69, 71, 72, 96]	OLL	2, 6b, 8d, 11c and Additional file 2: S2b and Additional file 3: S3a	Entirety of →olfactory glomeruli of one brain hemisphere located anterolateral within →brain and embedded in →antennal neuropil and →subantennal neuropil; it is connected with →median lobe of brain neuropils via → olfactory fascicles 1–3 and with δ-lobe and v-lobe of →mushroom body via → olfactory fascicle 4	antennal lobe	[17, 48]
					Glomerulargebiet [German]	[30]
					Glomerulipartie [German]	[28]
					Glomeruli-Partie [German]	[51]
					Glomeruli-Teil [German]	[51]
					Glomerulusteil [German]	[27]
					lobe olfactif [French]	[26]
					Olfactory neuropil	[57]
optic neuropil	[17, 38, 48, 55, 68]	ONP	2, 3, 4c, 10a–e and 13	Neuropil associated with eye and consisting of cup-shaped extracerebral part and tract-like intracerebral part, both of which consistently exhibit anti-synapsin immunoreactivity; it bifurcates into anterior and posterior branches; while anterior branch passes between →antennal neuropil and →subantennal neuropil to anteromedian position and vanishes in anti-acetylated α-tubulin and anti-synapsin stained brains (present study), posterior part passes through antennal neuropil and fuses with posterior stratum of →posterior division of →central body	Augennerv [German]	[28, 51]
					Augen-Nerv [German]	[51]
					Eye nerve [Russian: нерв глаза]	[101]
					lobe optique [French]	[26]
					nerf optique [French]	[26, 99, 101, 102, 109]
					Nerve 5	[13]
					nervus opticus [Latinised from Greek]	[30, 31, 73]
					Optic nerve	[25, 33, 40, 60, 81,82,83]
					Opticus [Greek]	[27, 53, 110]
					Optic ganglion	[25, 32, 65, 81, 83]
					Optic lobe	[43]
					Optic neuropils 1 and 2	[33, 42, 45, 75]
					Optic tract	[17, 32, 33, 38, 45, 47, 48, 54, 65, 69, 75, 136]
					pédicule optique [French]	[26]
					Sehmasse [German]	[30, 31]
					Sehnerv [German]	[31, 73]
					Tractus opticus [Latinised from Greek]	[30, 31, 52, 53, 79]
					Visual neuropil	[69]
					Visual neuropils 1 and 2	[33]
Outer lamina*	–	CB-OL	2, 3, 4c, 5a, c–e and 13	Neurite network and peripheral part of →central body surrounding →inner lamina; it shows inverted anteroposterior arrangement in →anterior division and →posterior division	–	–
Pedunculus; plural: pedunculi	[33]	PED	3, 4a, 5a, 7a–c, 13 and Additional file 2: Fig. S2b	Subunit of →mushroom body connecting →fascicles of globuli cells and →lobes; it gives rise to →ponticulus from its dorsomedian side	–	–
Pharyngeal nerve 1*	[39, 69]	PHN 1	1, 2, 11a–d, 12a, b, 13 and Additional file 5: Fig. S5c	Axon bundle associated with →deutocerebrum and innervating pharynx; it emerges posteriorly at indentation/fusion point of both brain hemispheres; it first proceeds anteriorly, then turns posteriorly and joins dorsolateral wall of pharynx; it extends to posterior end of pharynx, where pharyngeal nerves of both sides merge, forming loop; they are supplied by somata of serotonergic neurons distributed along pharyngeal wall [85] and are thus medullary structures	Eingeweidenerv [German]	[31]
					Frenal nerve	[56, 91]
					Frenalnerv [German]	[74]
					nerf viscerale [French]	[26]
					Nerve	[13]
					Nervus recurrens [Latin]	[28, 51,52,53]
					Nervus stomodeales [Latin]	[53]
					Nervus stomodealis [Latin]	[31]
					Paired stomodeal nerve	[56]
					Pharyngeal loop nerve	[48, 69]
					Stomatogastricus [Latin]	[27, 53, 110]
					Stomodaeal nerve	[43, 56]
					Sympathetic nerve	[25, 81, 82, 114]
Pharyngeal nerve 2*	[39, 69]	PHN 2		Diminutive axon bundle innervating pharynx; it originates from median part of →circumpharyngeal nerve cord anterior to →subpharyngeal commissure and innervates lateroventral wall of pharynx; most somata associated with this nerve are located in →deutocerebrum and only few in circumpharyngeal nerve cord [39]	hinterer Nerv des Mandilbularsomits [German]	[28]
					Stomodealnerv [German]	[74]
					Stomodeal nerve	[91]
Ponticulus*; plural ponticuli	–	PNT	2, 3, 4a, b, 6a, 7a–c and 13	From Latin pontis (=bridge); ponticulus connects →pedunculus of →mushroom body with →outer lamina of →central body; it shows neuropil-like organisation (with synapses) near pedunculus, but progressively turns into tract (without synapses) towards central body	Brücke [German]	[27]
					pédoncule [French]	[26]
					Peduncle	[90]
					Pedunculus [Latin]	[27, 28, 30, 31, 51, 53, 110]
					pedunculus	[32, 48, 54, 65, 69]
Posterior division (of central body)	[38]	CBP	2, 3, 5a, b and 13	Posterior subunit of →central body, which contains looping neurites forming →outer lamina and →inner lamina; →anterior division and →posterior division fuse laterally at dorsal part of central body; posterior division is associated with additional posterior stratum, from which it is separated by a discontinuous layer of somata and which is connected to posterior branches of →optic neuropils	hintere Lamelle des gestreiften Körpers [German]	[28]
					hinterer Zentralkörperteil [German]	[27]
					lame postérieure du bourrelet dorsal [French]	[26]
					Lamina posterior [Latin]	[32, 54, 65]
					Lamina posterior des Zentralkörpers [Latin + German]	[125]
					Posterior lamina	[17, 48, 69]
Posterior dorsal neuropil*	–	PDN	2, 4b, c, 5b–e, 11a, b, 12a–c, 13 and Additional file 5: Fig. S5b	Midline-spanning neurite region, which is part of brain neuropils; it is located in posterodorsal part of →protocerebrum posterior to →central body and anterior to →deutocerebral neuropil; it merges ventrally with →posterior ventral neuropil	Antennalkommissur [German]	[53, 110]
					Antennal commissure	[62]
					Central brain neuropil	[15, 17, 37, 48, 55, 59, 69, 70, 72, 98]
					Central commissural mass	[32, 54]
					Central fibrous mass	[56]
					Central lobe	[25, 81]
					Central neuropil	[13, 17, 32, 34, 38, 47, 48, 56, 59, 65, 69, 86]
					Central protocerebral commissure	[57]
					kommissurale dorsale Fasermasse [German]	[27]
					Median lobe	[25]
					obere Schlundkommissur [German]	[108]
					protocerebral commissure	[57]
					Zentralfasermasse [German]	[51]
					zentrale Kommissuren-Masse [German]	[51]
Posterior ventral neuropil*	–	PVN	2, 4b, 7a', c’, 11c, d, 12a–c, 13 and Additional file 3: Fig. S3d and Additional file 5: Fig. S5c	Midline-spanning neuropil of brain neuropil; it is located posteroventrally within →protocerebrum dorsal to →mushroom body and consists of neurite fibres emanating from →subantennal neuropil	Central brain neuropil	[15, 48, 55, 59, 70]
					Central fibrous mass	[56]
					Central lobe	[25, 81, 82]
					Central neuropil	[13, 17, 32, 34, 37, 38, 48, 55, 56, 59, 65, 69, 70, 86, 98]
					Median lobe	[25]
					Zentralfasermasse [German]	[51]
Protocerebrum	[15, 30, 48, 69]	PR	13 and Additional file 1: Fig. S1b	Part of →brain associated with →antennal nerve cord and belonging to first head segment; it is located anterior to →deutocerebrum and consists of cell body rind and following neuropils: →frontal body, →central body, →mushroom bodies, →olfactory lobes, →optic neuropils, → microglomeruli and large unitary neuropil complex comprised of →antennal neuropils, →subantennal neuropils, →median lobes, →central neuropil, →posterior dorsal neuropil, →posterior ventral neuropil and →ventral horns	Frequently used term; synonyms not listed, as protocerebral borders are ambiguous and inconsistent throughout the literature	–
Salivary gland nerve*	–	SGN	13	Axon bundle supplying salivary gland; it emanates from →ventral nerve cord posterior to →slime papilla nerve, then turns posteriorly and innervates salivary gland [13]	Nerve 12	[13]
Slime papilla nerve	[15, 38,39,40, 48, 59, 66, 68, 69]	SPN	–	Paired axon bundle innervating each slime papilla (i.e. specialised limb of 3rd head segment); anterior and posterior slime papilla nerves emanate between →lip nerve 3 and →salivary gland nerve at junction of →circumpharyngeal nerve cord and →ventral nerve cord and then turn anteriorly to enter slime papilla; associated somata are located within nerve cord opposite to bases of anterior and posterior slime papilla nerves [15]	nerf de tentacule buccal [French]	[77]
					Nerve 12	[13]
					Nerve of oral papilla	[43, 82]
					Nerve to oral papilla	[25, 81, 114, 115]
					Nervus papillaris [Latin]	[79]
					Papillar nerve	[61]
					Papillarnerv [German]	[28, 51]
					Papillennerv [German]	[74]
					Stomodeal commissure	[91]
Subantennal neuropil*	–	SAN	4a–c, 11b, c, 12a–c, 13 and Additional file 5: Fig. S5a, c, d	Neuropil, which situated laterally in each brain hemisphere; it is located ventral to →antennal neuropil and fuses posteriorly with →posterior ventral neuropil; it encompasses →microglomeruli, part of →mushroom bodies and →olfactory lobes and gives rise to →brain commissure 3	crête dorso-laterale [French]	[26]
					Lateral brain neuropil	[17, 48, 69]
					Postglomerular lateral neuropil	[13]
					Subantennalstrang [German]	[31, 51, 53, 110]
					subantennal lobe	[13, 32, 33, 54, 56, 62, 65]
					Subantennal tract	[32, 56]
					Subantennaltrakt [German]	[27]
					Subantennary tract	[56]
					Tractus subantennalis [Latin]	[27, 30, 31]
					Ventro-lateral horn	[25, 81]
Subpharyngeal commissure*	–	SPC	2, 12a–c, 13 and Additional file 1: Fig. S1a, c and Additional file 5: Fig. S5a, c, d	Neurite bundle, which is anteriormost →ventral commissure; sole commissure associated with →circumpharyngeal nerve cords	1. Kommissur [German]	[52]
					Commissural cord	[99]
					Commissure 1	[25, 82]
					commissure sous-œsophagienne [French]	[77]
					First ventral commissure	[43]
					Kommissur des Mandibularsomits [German]	[28, 51]
					Postoral commissure 1	[39]
					premiere commissure anterieure [French]	[102]
					Schlundkommissur [German]	[73]
					Sub-oesophageal commissure	[60]
					Tritocerebralkommissur [German]	[74]
					untere Schlundkommissur [German]	[80]
Suprarectal commissure*	–	SRC	1a, b	Posteriormost commissure linking →ventral nerve cords from both sides and forming loop above hindgut	Anal commissure	[82]
					Posterior dorsal commissure	[25, 81]
					Posterior-most commissure	[48]
Tongue nerve	[38]	TON		Axon bundle innervating tongue; it originates medial to →hypocerebral organ and proceeds into tongue [13]	Nerve 6	[13]
Ventral commissure	[43, 63]	VC	1c, d, 13 and Additional file 1: Fig. S1b and Additional file 5: Fig. S5b	Serially repeated median bundle of neurites connecting →ventral nerve cords from both body sides; anteriormost ventral commissure, which links →circumpharyngeal nerve cords, is specified as →subpharyngeal commissure	Commissur [German]	[31, 73, 76]
					commissura transversae [Portuguese]	[78]
					Commissural axons	[66]
					Commissure	[25, 33, 60, 81, 82, 102, 105, 114, 115]
					commissure [Russian: коммиссуры]	[101]
					commissure ventral [French]	[77]
					Communcationsnerven [German]	[76]
					cross commissure	[90]
					Kommissur [German]	[27, 29, 50, 74, 79]
					Median commissure	[3, 14, 17,18,19, 37, 39, 41, 48, 68, 69, 116, 121]
					Nerve commissure	[43]
					Postoral commissure	[39, 69]
					Tract-like commissure	[134]
					Transversal commissure	[100]
					Transverse commissure	[89]
					Transverse cord	[115]
					Quercommissur [German]	[112]
					Querkommissuren [German]	[28]
					Quernerven [German]	[76]
Ventral horn*	–	VH	4c, 11c, d and 12a–c	Cone-shaped neuropil; it emanates medially from →posterior ventral neuropil and extends anterior to level of →median lobes	–	–
Ventral nerve cord	[3, 13,14,15, 17,18,19, 25, 32, 34, 38,39,40,41,42,43, 48, 54, 56, 59, 61,62,63, 65, 67,68,69,70,71,72, 82, 83, 86, 90, 91, 93,94,95,96, 98, 100, 115, 116, 121, 137, 138]	VNC	1a–d, 13 and Additional file 1: Fig. S1c	Ventrolateral medullary nerve cord of trunk, which consists of peripheral cell body rind and central neuropil and anteriorly joins →circumpharyngeal nerve; ventral nerve cords of both sides are connected medially via → ventral commissures, laterally via → dorsal commissures and posteriorly via → suprarectal commissure; each ventral nerve cord gives rise to lateral segmental →leg nerves at basis of each leg and to median segmental →nephridial nerves	Bauchkette [German]	[28, 29]
					Bauchmark [German]	[52, 53, 79, 110]
					Bauchnervenstrang [German]	[73]
					Bauchstrang [German]	[31, 51, 76, 113]
					cadeia nervosa ventral [Portuguese]	[78]
					chaîne ventrale [French]	[104]
					Connective	[33]
					cordon nerveux [French]	[77, 103]
					Längsnervenstrang [German]	[51, 80]
					Längsnervenstamm [German]	[28, 73, 80, 109]
					longitudinal connective	[66]
					Markstamm [German]	[139]
					Markstrang [German]	[111]
					Nervenstamm [German]	[29]
					Nervenstrang [German]	[76, 135, 140]
					Nerve-cord	[25, 60, 81, 99, 114, 141]
					Nerve-strand	[32, 54, 60]
					Nerve trunk	[89]
					Seitennerv [German]	[112]
					tronc ventral/nerveux [French]	[102]
					Ventral cord	[14, 25, 114]
					Ventral cord [Russian: брюшной ствол]	[101]
					Ventral nervous system	[33]

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