Anatomical Dictionary |
a b c d e f g h i j k l m n o p q r s t u v w x y z
| anatomical name | abbrebiation | definition |
| 2nd Ascidian Stage | 2nd | |
| A/A*4.1 derived cells (Undefined cells) | Undefined tissue at lateral side of the anterior sensory vesicle. It express Ci-TK (tachykinin gene) at the tailbud stage. Reported also in Halocynthia roretzi (Taniguchi and Nishida, 2014) | |
| absorbed tail tissues | abs. tail | |
| Accessory cells | Cellular egg envelopes, constituted of Inner follicle cells, outer follicle cells and test cells. | |
| Adhesion Period | Ad | |
| Adult Stage | Adult | |
| ampullae | amp | |
| Animal Death | Death | |
| anterior pharynx | ant pha | |
| Anterior sensory vesicle | Part of the sensory vesicle located anterior to the ocellus. The anterior sensory vesicle corresponds to forebrain of vertebrate (Manni and Pennati 2015). It includes a couple of antenna cells and associated antenna interneurons. | |
| Anus | Aperture of the intestine into the atrial chamber | |
| Apical trunk epidermal neurones (ATEN) | Epidermal sensory neurons located in the apical part of the trunk. | |
| Ascidian dendritic network in tunic, ASNET | Sensory cilia network extending in the tunic outer compartment, outward from numerious pairs of caudal primary sensory cells, in rows, within the dorsal and ventral parts of the epidermis. | |
| Atrial cavity | In larva period, there are two atrial primordia anterior to the notochord at about the level of the hindbrain (rudiments of the peribranchial chamber and the atrial siphon) deriving from a pair of invaginations from the dorsal trunk epidermis. In the juvenile, the two paired evaginations fuse each other ain a single cavity on the dorsum and lateral sides of the pharynx and then they open to the exterior by means of a single dorsal atrial siphon. | |
| atrial chamber | ac | |
| Atrial pigment spot | Pigment spots round the tip of the atrial siphon. They are characteristically six, located in the notches between the siphon lobes. Synonym: ocellus | |
| atrial placode | Rudiments of the atria, in the form of two dorsal, symmetrical ectodermal thickenings, one on the left and one on the right, located posterior to the stomodeum. They differentiate: peribranchial/atrial cells, atrial secreting tunic cells, primary sensory neurons, supporting cells secreting the cupula, stigmatal ciliated and parietal cells. | |
| Atrial siphon | as | Dorsal, cylindrical body extension by which the dorsal aperture is projected; it typically possesses six lobes. In metamorphosing larva, there are two atrial siphons, in continuity with the atrial cavities, deriving from a pair of invaginations from the dorsal trunk epidermis (atrial siphon primordia). In the juvenile they fuse each other and become a single siphon. Synonym: excurrent (or branchial) aperture. See also atrial siphon muscles. |
| atrial siphon left | asl | |
| Atrial siphon muscle | asm | Atrial sphincter muscles responsible of atrial siphon contraction. Atrial siphon muscle exists from tailbud stage (st 28); functioning in stage 36 |
| Atrial siphon primordia | asp | Rudiment of the atrial siphon, peribranchial chamber and cloacal cavity in the form of two dorsal, symmetrical invaginations of the ectoderm, one on the left and one on the right, located posterior to the stomodeum. |
| atrial siphon right | asr | |
| Bipolar tail neurones | Neurons of the tail epidermis with a large (15?20 m), fusiform soma and both an ascending and a descending projection. They were observed only on the dorsal side, lying in close proximity to neighboring bipolar neurons, spaced at intervals of 10?20 m, although in some preparations the somata of adjacent bipolar neurons lay close to each other. | |
| blood cells | bc | |
| Blood sinuses | Spaces among organs and in the mantle in which haemocytes flows | |
| Body Rotation Period | BodyRotation | |
| Body wall | Space delimited by the epidermis and the peribranchial/atrial walls; it contains connective tissue, muscles, neural complex, nerves, haemocytes, haemocele, and heart. Synonym: manle. | |
| Body wall muscles | Somatic, smooth musculature extending throughout most of the mantle to form numerous longitudinal and circular (latitudinal) bands. | |
| Branchial cavity | Branchial zone cavity, delimited by the branchial epithelium | |
| branchial chamber | brc | |
| Branchial epithelium | Epithelium delimiting the branchial zone. Synonyms: pharyngeal epithelium, pharyngeal wall | |
| Branchial zone | First fissured tract of the alimentary canal; area comprised between the perypharyngeal band and the esophagus; it contains the endostyle, the stigmata and the dorsal lamina (synonyms: branchial chamber, pharynx) | |
| central nervous system | CNS | |
| cephalenteron | ceph | |
| cerebral ganglion | cg | |
| Cerebral ganglion | it is organized in a cortex of neuronal somata and an inner medulla of neurites continuous with nerrves. Synonym: brain. | |
| cilia of ATEN | cilATEN | |
| cilia of CESN | cilCESN | |
| cilia of RTEN | cilRTEN | |
| ciliated duct | cilduc | |
| ciliated duct of neural gland | cil duc | |
| Ciliated funnel | funnel-like duct of neural gland opening into the prebranchial pharynx on the dorsal tubercle. | |
| cilium of an anterior trunk epidermal neuron | ATEN | |
| cilium of dorsal caudal epidermal neuron | DCEN | |
| cilium of rostral trunk epidermal neuron | RTEN | |
| cilium of ventral caudal epidermal neuron | VCEN | |
| Circular System | System of slender transverse and oblique muscles forming a net encirlyng the body. | |
| Cloacal cavity | Dorsal part of the atrial cavity lying above the roof of the pharyns and extending into the atrial siphon. | |
| Coronal organ | Mechano-sensory organ constitued of a continuous line of ciliated secondary sensory cells along the margin of velum and tentacles. | |
| Coronet cells | cor | Cells constituting a hydropressure organ; there are 18 coronet cells characterised by bulbous protrusions into the lumen of the vesicle’s left side. They are associated to ciliated interneurons (cor-ass BVIN: ciliated coronet associated brain vesicle interneurons). |
| Cupular organ | Mechanoreceptor of the atrial siphon consisting of a pad of tissue (macula) containing supporting cells and sensory cells (primary sensory neurons) whose cilia project into a finger-like process composed of tunic-like material, the cupula. Synonym: cupula organ. | |
| cuticle | cut | |
| Definitive tunic | Tunic covering the juvenile and the adult. It corresponds to the Inner layer of larval tunic and cuticle. | |
| degenerating papilla | deg pp | |
| degenerating tail | deg tail | |
| Distal intestine | terminal intestine (rectum) | |
| Dorsal caudal epidermal neurones (DCEN) | Up to ten pairs of sensory neurons located in the dorsal caudal epidermis. | |
| Dorsal lamina | dl | longitudinal fold of the mid-dorsal branchial wall |
| Dorsal plexus | Tubular epithelial structure originating from the posterior end of the neural gland and running running back within the dorsal blood sinus. | |
| dorsal sinus | ds | |
| Dorsal strand | dst | Plexus of neurons associated to the dorsal strand. It is a classical nerve net, composed of bi- and multi-polar neurons with their cell bodies in the periphery. |
| Dorsal Tubercle | Tubercle on which the duct of the neural gland opens as a ciliated opening. Horse-shoe shaped aperture of the neural gland duct; other name: ciliated funnel | |
| Egg | Female gamete. The mature egg is about 150 micron in diameter. It prduces an acellular vitelline coat. | |
| Eminens cell | A large (20?25 μm) fusiform neuron is present on the dorsal side, called ‘eminens cell’ for its large size and prominent position. | |
| Endodermal strand | est | Strand of endodermal cells located in the tail, ventrally to the notochord. |
| Endostylar appendix | Posterior end of the endostyle projecting in a modified form as a short appendix. | |
| Endostyle | es | deep groove along the ventral mid-line of the branchial chamber, consisting of eight major longitudinal cellular bands (zones). It is homologous to the vertebrate tyroid glabd (Wiley, 1893). Recognizable anatomically at stage 34 as subdivided in bands; functioning at stage 36. |
| endostyle primordium | esp | |
| Ependymal cells | They are non-nervous cells in the larval nervous system. They are in the neck, in the posterior sensory vesicle, in tail nerve cord and in visceral ganglion. In the tail nerve cord, they are four in cross-section: the right and left lateral cells, dorsal capstone cell, and ventral keel floor cell. | |
| Epicardiac cavity | Paired endodermal sacs that evaginate from the postero-vetnral part of the pharynx. The right and the left epicardiac cavities form the perivisceral cavities. The left epicardiac cavity contains the intestine and the ovary; the esophagus, the stomach, and the heart lie between the two cavities; the stomach and the heart protrude into the left cavity. Synonym: epicardiac sac. | |
| Epidermis | epi | Ectodermal monolayered leaflet enveloping the individual and covered by tunic. |
| Esophagus | First segment of the postpharyngeal tract, consisting mainly of ciliated cells secreting mucus; it contains also endocrine cells. It possesses two longitudinal groves, on of which in continuity with the retropharyngeal band. | |
| Female reproductive system | It consists of the ovary, furnished of oviduct. | |
| Gastrula Period | Gst | |
| Germ cells precursor | Cells giving rise to gametes. Potential Primordial Germ Cells are B/B*9.23 and B/B*9.24 after the cell division of B/B*8.12. | |
| gill slits | gs | |
| Gut primordium | gp | Endodermal tissue posterior to protostigmata rudiments. Synonym: gut rudiment. |
| <h2 id="h"></h2> Haemocele | space in which haemocytes flow | |
| haemocyte | hc | (Or Hemocytes) Blood cells are circulating cells, including two main hemocyte types categories: 1. agranular hemocytes, including hemoblasts, circulating lymphocyte-like cells, hyaline amebocytes; 2. granular hemocytes including granulocytes with small granules, granulocytes with large granules, unilocular refractile granulocytes and morula cells. TLCs give rise to adult blood cells after metamorphosis. TLCs are exclusively derived from the A7.6 cell pair of 64-cell embryos. Synonym: blood cells. |
| Heart | ht | Curved, short, double-walled tube between the stomach and the posterior end of endostyle. In stage 32 it is in form of a ventral group of cells at level of atrial primoridia; in st. 33 it is a ventral vesicle. Heart beating at st. 36. |
| hemocyte | hc | |
| Inner compartment of tunic | ICT | Layer of larval tunic located beneath the outer compartment. It is covered by a cuticle (called inner cuticular layer, C2). In all species C2 becomes the surface of the juvenile when C1 and the outer compartment are discarded, soon after the onset of metamorphosis. |
| Inner cuticular layer (C2) | ICLT (C1) | C2 forms the outermost surface of juvenile and adult |
| inner cuticular layer of tunic (C2) | iclt (C2) | |
| Inner follicle cell | Inner follicle cells remain on the vitelline coat. | |
| Intestine | int | Alimentary tract posterior to stomach; subdivided in three segments: proximal, mid and terminal (distal or rectum) intestine; it contains also endocrine cells. It forms a loop where the ovary lies. It derives from B7.2 according to Hirano and Nishida, 2000 in Halocynthia roretzi. Intestine is functioning at st. 36 |
| Juvenile Period | Juvenile | |
| Juvenile/adult nerves | bundles of neuritis (both sensory and motors); principlal nerves are: the paired anterior nerves, the paired posterior nerves, and the umpaired visceral nerve. | |
| Larva Period | Lv | |
| larval brain remnants | lbr | |
| larval central nervous system | LCNS | |
| Larval central nervous system | Main structures of the central nervous system are: sensory vesicle, the neck, the visceral ganglion, and the tail nerve cord. It includes contrapelo cells. | |
| Larval nervous system | Central and peripheral nervous system in larva | |
| Larval Nervous System Remnants | Residual larval nervous system during metamorphosis metaperiod | |
| Larval peripheral nervous system | Epidermal sensory neurons populating the dorsal and ventral axes of the larva in a rostrocaudal sequence. It includes the peripheral nervous system relay neurons associated to photoreceptors. | |
| Larval pharynx | Rudiment of the pahrynx. | |
| larval tail remnant | ltr | |
| Larval tunic | Tunic covering the larval trunk and tail; in the tail, it forms continuous fins. The larval tunic of the trunk consists of two cuticular layers and two compartments with filamentous matrices (Cloney and Cavey, 1982; Cavey and Cloney, 1984; Lubbering and Goffinet, 1991). | |
| left atrial siphon | las | |
| left atrial siphon muscles | lasm | |
| left atrial siphon primordium | lasp | Left, dorsal invagination of the ectoderm, contributing to the formation of the atrial siphon, peribranchial chamber and cloacal cavity. |
| left protostigmata | lpsm | |
| Lens cells | There are three cells within the ocellus. | |
| Longitudinal bar | Longitudinal bar of tissue delimiting rows of adjacent gill-slits; it contains the longitudinal sinus of the branchial sac. | |
| Longitudinal System | System of longitudinal muscles lying external to the circular system, organized into defined bands. | |
| Longitudinal vessel | internal longitudinal blood sinus of the inner surface of the branchial wall, running parallel to its long axis | |
| Male reproductive system | It consists of the testis. | |
| mantle | man | |
| medium intestine | mint, mi | |
| Mesenchyme | mech | mesenchyme cells derive from B8.5 and B7.7; TLCs derives from A7.6 lines (Tokuoka et al., 2004 Dev Biol). Mesenchymal cells are located bilaterally in the trunk region of the mid-tailbud embryo. They are mostly spherical and can migrate. |
| Mid intestine | intermediate tract of intestine encrosted by tubules and pmpullae of the pyloric gland | |
| Motor neurones | Five pairs of presumed ventrolateral neurons in the visceral ganglion. | |
| Myocardium | mc | contractile, monostratified myo-epithelium forming the inner heart tube (synonym: endomyocardium) |
| Neck | ne | The neck is corresponding to midbrain of vertebrate (Manni and Pennati 2015). The neck includes dorsal neck ependymal cells. |
| nerve cord | nc | |
| Neural complex | It is constituted of the cerebral ganglion and the neural gland complex (ventral to the former); it is located, in the dorsal mantle between the two siphons | |
| Neural crest | In Halocynthia roretzi, two undefined cell pairs(b7.13 derived) were reported in the posterior-dorsal region of the tail (Nishida and Satoh, 1985). These cells belong to neither the spinal cord nor the epidermis. It was found that, in Ciona (Nakamura et al., 2012), the same cells also seemed to be present under the dorsal epidermal cell layer. Synonym: bipolar tail neurons. Stolfi et al., 2015 Nature recognized as neural crests the cells derived from b/b*7.13 (Undefined cells). According to Abitua et al., 2012, the cephalic melanocyte lineage (a9.49) is similar to neural crest that can be reprogrammed into migrating ectomesenchyme. According to Jeffery et al. 2008, Neural crest-like cells are derived from the A7.6 cells, the precursors of trunk lateral cells (TLC), one of the three types of migratory mesenchymal cells in ascidian embryos. | |
| neural gland | ng | |
| Neural gland body | Elongated gland body constituted of spongeous cells | |
| Neural gland complex | gland in form of a blind sac located in the dorsal mantle ventral to the cerebral ganglion and opened in the branchial chamber. Synonym: hypophysis | |
| neurohypophyseal duct | nd | |
| neurohypophyseal placode | See Neurohypophysis. It differentiates motor neurons, GnRH+ neurons, neural gland cells, epithelial cells of the dorsal strand, GnRH+ neurons of the dorsal strand plexus. | |
| Neurohypophysis | Neural complex rudiment recognizable as blind tube from st. 25 (Manni et al., 2005). it opens at st. 26. Synonyms: neurohypophysial duct, neurohypophysial placode, neurohypophysial canal. | |
| Neurula Period | Neu | |
| Notochord | noto | The ascidian notochord is a flexible rod that extends outward from the posterior part of the larval trunk, near the branchial basket, and forms the axis of the tail. The notochord is a skeletal device that provides support for the fins, the epidermis, the skeletal muscle, the endodermal strand, and the nerve cord. This support is lost through at least two distinct mechanisms during metamorphosis, when the tail is retracted (Cloney 1972, 1978, 1982, 1990b). The C. intestinalis notochord in the tailbud stage embryo consists of 40 cells. The notochord is located at the tail midline and surrounded by the dorsal hollow of the nerve cord, the bilateral sideof the muscle and endoderm in the ventral side. |
| Ocellus | oc | Light sensory organ. |
| Ocellus remnants | Residual ocellus during metamorphosis metaperiod | |
| oesophagus | oes | |
| Oral cavity | Lumen of the oral siphon, extending till the rim of velum and tentacles. | |
| Oral pigment spot | Pigment spots round the tip of the oral siphon. They are characteristically eight, located in the notches between the siphon lobes. Synonym: ocellus | |
| Oral siphon | os | Cylindrical body extension by which the anterior aperture is projected. Synonym: branchial aperture; mouth;incurrent opening. See also oral siphon muscles. |
| Oral siphon muscles | osm | Oral sphincter muscles responsible of oral siphon contraction. Oral siphon muscle exists from tailbud stage (st 28); functioning in stage 36. In C. intestinlis they derive from A7.6. |
| Oral siphon primordium | osp | Rudiment of the oral siphon. Synonym: stomodeum |
| oral tentacles | ten | |
| os | oral siphon | |
| osp epidermis | osp epi | |
| Otolith | ot | Gravity-sensing organ. The organ is formed of pigmented cells, sensory cells and specialized ependymal cells. Synonym: statocyte |
| Otolith remnants | Residual otolith during metamorphosis metaperiod | |
| outer compartment layer | Tunic layer covering both the trunk and tail. It contains filaments and grounds substance. | |
| outer compartment of the tunic/tail fin | oct/tf | |
| outer compartment of tunic | oct | |
| outer cuticular layer of tunic (C1) | oclt (C1) | The outer cuticular layer (C1) is usually in the range of 15-35nm in thickness. It forms the fins, including the major folds, minor plications, and convolutions that facilitate bending. The outer compartment also contains sensory cilia that extend outward from numerious pairs of caudal primary sensory cells, in rows, within the dorsal and ventral parts of the epidermis (Torrence and Cloney, 1982; Crowther and Whittaker, 1994). |
| Outer follicle cell | Outermost layer of accessory cells. At ovulation, they remain in the ovary. | |
| Ovary | Pear-shaped body lying in the intestinal loop. | |
| Oviduct | Long and narrow duct, leading from the anterior end of the ovary, extending anteriorly to the anus. | |
| Palp neurons | Sensory neurons in palps most likely playing a role in substrate sensing/selection. Synonym: papillary neurons. | |
| Papilla | pp | According to Grppelli et al. 2001, the papillae are simple, coniform, noneversible and are constituted of secreting cells, axial columnar cells, primary sensory neurons and undifferentiated ectodermal cells. Synonim: palps. CHECK: cuboidal palp cells (dorsal cuboidal palp cells(a8.18line) and ventral cuboidal palp cells(a8.20line)) and palp neurones (dorsal palp neurones (a8.18line) and ventral palp neurones (a8.20line)). |
| Peribranchial cavity | Two lateral and symmetrical cavities lying to each side of the pharynx, jointed dorsally into the cloacal cavity and communicating with the pharynx by means of stigmata. In metamorphosing larva, the two peribranchial cavities open to the exterior independently at st. 29, one on each side of the body. Synonym: peribrancial chamber. | |
| peribranchial chamber | pbc | |
| Peribranchial epithelium | Epithelium delimiting the peribranchial cavities; it can be subdivided in an inner component (taking part to the branchial wall), and an outer component delimiting the mantle; synonym: peribranchial wall. It derives from the atrial primordia | |
| Pericardial cavity | space delimited by pericardium and myocardium | |
| Pericardium | pc | simple, non contractile epithelium forming the outer wall of heart tube |
| Peripharyngeal band | pb | ciliated band on inner surface of the pahrynx, delimiting the prebranchial region from the branchial one. Synonym: pericoronal groove, peripheral pharynx (CiAID) |
| Pharyngo-epicardial openings | Openings connecting the epicardiac cavities with the pharyngeal cavity. | |
| Pharynx | pha | Organ extending from the rings of tentacles to the mouth of the esophagus. Synonym: branchial cavity, branchial sac. |
| pharynx anterior | pha ant. | |
| pharynx lumen | pha lum | |
| pharynx posterior | pha post. | |
| Photoreceptors | There are 37 photoreceptors within the ocellus (type I, II and III). Photoreceptors are associated to several types of neurons (interneurons, relay neurons, and peripheral nervous system relay neurons). | |
| Pigment cup cells | There is a single cup-shaped pigment cell with many small melanin granules (0.5?2 μm) forming the ocellus. |
|
| Placode | Placodes in vertebrates are defined as transient specialized regions of the embryonic ectoderm that give rise to a variety of nonepidermal cell types and are subject to morphogenetic movements, such as invagination of cell sheets and epithelial-mesenchymal transactions. | |
| posterior brain | post. brain | |
| posterior pharynx | post pha | |
| Posterior sensory vesicle | Part of the sensory vesicle located posterior to the ocellus. It includes dorsal and ventral neuron clusters and ependymal cells. | |
| Prebranchial zone | area comprised between the velum/tentacles and the perypharyngeal band; it contains the dorsal tubecle. | |
| Preoral lobe | pl | Wide anterior body-cavity in the larva, comprised between the pharynx and the anterior epidermis. At metamorphosis,it elongates in the stalk sustaining the animal body. |
| primary muscle lineage | It comprises the following lines: B7.5, B7.8, B9.29 to B9.32, and B7.4. | |
| Primary notochord lineage | The anterior 32 'primary' notochord cells are derived from blastomeres A7.3 and A7.7. Fate mapping experiments in the ascidian Halocynthia have suggested that the A7.3 and A7.7 blastomeres that give rise to the anterior 32 notochord cells both contribute randomly to the primary notochord (Nishida, 1987). These observations implied that ascidian notochord intercalation is highly stochastic. | |
| Protostigmata | psm | Elliptical fissure permitting comunication between the branchial and the peribranchial chambers; delimited by seven rows of ciliated cells, with cilia forming a single row in each cell. Definitive gill-slits will form by the three pairs of protostigmata by subdivision of these six primary stigmata . Gill-slits will form several, parallel rows on the lateral walls of the branchial chamber; their number will undergo a gradual increase as the animal grows. They are not perforeted at st. 35. |
| Proximal intestine | prox. int | first tract of inestine (preglaundular intestine) |
| Pyloric caecum | pyc | Short, blindly ending pouch arising from the junction of the stomach and the intestine, on the posterior side, and projecting in a dorsal direction. Acording to Nakazawa et al., 2013, the lumen of the gut duct becomes divided into two: one duct located ventrally will form the main digestive tract, the other located dorsally will form the duct of pyloric gland. Synonym: hepatopancreas; gastric caecum. |
| pyloric gland | pg | System of anastomosing and bindly ending tubules spread over the surface of the rectum and a small part of the intestine. In continuity with the gut at the junction between the stomach and the intestine. |
| rafe | longitudinal lips at the border between pericardium and myocardium | |
| raphe | rph | |
| remnant of larval brain | rmn lv brain | |
| Reproductive system | It consists of a separate ovary and testis. | |
| Retropharyngeal band | Band connecting the postero-ventral end of endostyle with the esophageal opening | |
| right atrial siphon | ras | |
| Right atrial siphon primordium | rasp | Right, dorsal invagination of the ectoderm, contributing to the formation of the atrial siphon, peribranchial chamber and cloacal cavity. |
| right protostigmata | rpsm | |
| rostral placode | Rostral ectoderm thickening destined to form the adhesive organ, and epidermal sensory neurons. This region also forms epidermal derivatives, such as the preoral lobe. It differentiates epidermal cells, axial columnar cells, secreting cells, primary sensory neurons. | |
| Rostral trunk epidermal neurones (RTEN) | RTEN | Sensory neurons located in the rostral trunk epidermis. They derive from a8.26 line. |
| secondary muscle lineage | It comprises the following lines: b8.17 and A9.31. | |
| Secondary notochord lineage | The posterior 8 'secondary' notochord cells are derived from B8.6. | |
| Sensory organ | Organ involved in perception of external stimuli. | |
| Sensory vesicle | sv | Vesicle containing a mineralized statolith, sensory neurons, and coronet cells that are considered to be homologues of the coronet cells in the saccus vasculosus of fishes. |
| siphon primordia | They consist of the atrial and oral siphon primordia. | |
| Spermatozoon | Male gamete. | |
| Stage 0, Unfertilized egg | U | |
| Stage 1, Fertilized egg | F | |
| Stage 6, 32 cell | 32 | |
| Stage 8, 64 cell | 64 | |
| Stalk | stk | Peduncle by which the individual is attached to the substratum; it possesses haemocyte circulation. Synonym: holdfast (Hirano and Nishida, 2000 Dev Genes Evol). |
| Stigmata | Branchial fissures | |
| Stomach | stom | Large, ovoid sac of the alimentary canal whose wall is folded in up to about 40 longitudinal ridges.Its posterior part is surrounded by the testicular network. |
| stomach primordium | stom primrod | |
| stomodeal placode | Typical ectodermal invagination contributing to the formation of the oral siphon, the velum and the tentacles. It differentiates oral secreting tunic cells, sensory ciliated cells of the tentacles and epidermal sensory neurons. | |
| tail | tail | |
| Tail Absorption Period | Absorption | |
| Tail epidermis | Epidermis of the larval tail. During tail absorption period, tail epidermis is shrinked and absorbed within the trunk, becoming tail remnants. | |
| tail fin | tf | |
| tail muscle cells | tmc | In the tail, the ntochord is flanked by 18 pairs of muscle cells. |
| Tail nerve cord | There are midtail neurons, short descending neurons. Synonym: caudal nerve cord. | |
| Tail nerve cord remnants | Residual tail nerve cord during metamorphosis metaperiod | |
| tail remnants | tail remn | |
| Tailbud Period | TB | |
| Tentacle | ten | Siphon tentacles are symmetrical extensions at the base of oral siphon; they are of different lenghts: the longest ones (first order tentacles) almost reach to the centre of the siphon; alternating with them, are shorter ones forming series (second, third, fourth orders). Synonyms: branchial tentacle, oral tentacle |
| terminal intestine | term int | |
| test cells | tc | Test cells are encased in superficial depression of the oocyte. In spawned eggs, they allow buoyancy. |
| Testis | Diffuse system of branching tubes spreaded over the intestine and the posterior part of the stomach. | |
| Transverse bar | Transverse bar of tissue delimiting rows of adjacent gill-slits; it contains the transverse sinus of the branchial sac | |
| Trunk | trunk | Synonym: cephalenteron. |
| Trunk epidermis | Epidermis of the larval trunk. During metamorphosis metaperiod, trunk epidermis becomes the juvenile epidermis. | |
| trunk ventral cells (B7.5 line) | Trunk ventral cells (TVCs) are descendants of B7.5 and are located in the recesses of the ventral side of the trunk endoderm. | |
| tunic | tun | Tissue external to the epidermis, containing free cells, fibers, and ground substance, produced by the epidermis. It anchors adults to solid substrata, supports and protects the underlying tissues and organs. Synonym: test. |
| tunic - cuticular layer of tunic (C1) | CLT | |
| tunic - inner compartment of tunic | ict | |
| tunic - inner compartment of tunic | ICT | |
| tunic - inner cuticular layer of tunic (C2) | iclt (C2) | |
| tunic - inner cuticular layer of tunic(C2) | ICLT (C2) | |
| tunic - outer compartment of tunic | oct | |
| tunic - outer compartment of tunic (fin of the tunic) | OCT | |
| tunic - outer cuticular layer of tunic (fin of the tunic) C1 | oclt (C1) | |
| Tunic cells | tun, tunc | Cells including: large granular cells, morula cells, granulocytes I and II, phagocytes |
| tunic cuticle | cut | |
| tunic fin | tf, tun fin | |
| Velum | ve | short, circular fold at the base of oral siphon connecting the tentacle base |
| Ventral caudal epidermal neurones (VCEN) | VCEN | Up to ten pairs of sensory neurons located in the ventral caudal epidermis. |
| Visceral ganglion | vg | The VG is corresponding to hindbrain of vertebrate (Manni and Pennati 2015). There are several motor ganglion interneurons, including ascending motor ganglion interneurons and descending decussating motor ganglion interneurons. There are ependymal cells. |
| Zone I | mid ventral zone with particularly long cilia | |
| Zone II | fan shaped protein secreting zone with short cilia | |
| Zone III | zone formed by thin, columnar cells bearing a cilium accompanied by microvilli (resembling coanocytes) | |
| Zone IV | fan shaped protein secreting zone with short cilia | |
| Zone V | zone formed by prismatic cells bearing several cilia | |
| Zone VI | zone formed by columnar, monociliated, protein secreting cells | |
| Zone VII | zone formed by cuboidal non ciliated cells, able to accumulate iodine, secerning glycoproteins | |
| Zone VIII | marginal zone formed by cuboidal cells with numerous cilia; the zone is continuous with the peripharyngela bands |