biology

Glossary of tunicate anatomy

Glossary of tunicate anatomy is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Glossary of tunicate anatomy rather than just read about it. In short: Tunicates (subphylum Tunicata) are a group of filter-feeding marine invertebrates. As chordates, they have been proposed to be the closest relatives of vertebrates.

Key takeaways

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Reference excerpt

Tunicates (subphylum Tunicata) are a group of filter-feeding marine invertebrates. As chordates, they have been proposed to be the closest relatives of vertebrates. Tunicates are divided into three classes: the sessile Ascidiacea, and the free-swimming Thaliacea and Appendicularia. Some anatomical features are shared between classes, while others are specific to a lineage or to a life stage.

A adhesive organ 1. An organ present at the anterior end of ascidian larvae, serving to attach the larva to the substrate during its metamorphosis. It is usually made of three papillae. 2. The individual papillae.

atrium

atrial pore

atrial siphon

Also excurrent siphon or exhalant siphon. Opening through which water exits the branchial basket in ascidians.

B blastozooid

Sexual generation in the life cycle of salps. They grow from the parent oozooid before budding off and sexually reproducing, with internal fertilization. In most species, females are viviparous and grow a single oozooid.

branchial basket

Also branchial sac, gill sac, pharyngeal sac or pharynx. Main pumping and filtering cavity of the tunicate body. It is lined with stigmata through which water is filtered. In ascidians, the branchial basket can be flat, or folded in various arrangements.

brooding

Method of reproduction in ascidians, where zygotes are incubated inside the body of the individual. In some species, a dedicated brood pouch is present.

budding

Method of reproduction in colonial tunicates, where new zooids, or "buds", grow from the body of existing zooids or from stolons.

cadophore

Stolon-like posterior extension of the doliolid nurse comprising three pairs of rows from which phorozooids and trophozooids develop.

cerebral ganglion

coronal organ

Sensory organ present in the oral aperture of ascidians and most thaliaceans (except salps). Made of a row of secondary sensory cells (hair cells), it monitors the flow of incoming water and prevents large particles from entering. It has been suggested to be homologous to the circumoral ring of larvaceans.

D dorsal strand

Posterior extension of the neural gland.

dorsal tubercle

Ciliated funnel connecting the neural gland to the branchial basket. Its shape varies between species, from a simple U-shaped funnel to a longer slit-like or more elaborate structure.

E endostyle

Mucus-secreting organ located inside the branchial basket. The mucus net it produces lines the inner branchial basket, and captures food particles. It is believed to be homologous to the thyroid in vertebrates.

gonozooid

Sexual generation in the life cycle of doliolids. They grow from a stalk connecting the phorozooid to its parent oozooid. After the phorozooid breaks off, the gonozooids keep growing attached to its ventral peduncle, until themselves breaking off and becoming free-living. Gonozooids are hermaphroditic and reproduce by internal fertilization.

house

A structure secreted by larvaceans, composed of oikosins and cellulose. It comprises several chambers, and fully surrounds the body in some species. Houses are used for filter-feeding and to provide buoyancy, and are repeatedly discarded and replaced after becoming clogged.

hyaline cap

Glue reservoir positioned at the anterior tip of the papillae, secreting adhesive material upon contact with the substrate.

M mantle

Also epidermis or mantle epithelium. Epidermal epithelium layer located below the tunic.

N neural gland

Gland connected to the brain, together forming the neural complex. Its exact function is unclear. It is believed to be homologous to the anterior pituitary in vertebrates.

nurse

Mature stage of the oozooid in doliolids, capable of producing phorozooids and trophozooids.

O ocellus

Light-sensing organ inside the sensory vesicle. It is multicellular, containing a cup-shaped pigment cell, three lens cells, and various kinds of photoreceptor cells.

oikoplast

Also oikoplastic epithelium. Oikosin-producing layer of epithelium surrounding the trunk of larvaceans. The secreted oikosins form a pre-house above the epithelium before being inflated into the house. It is divided in multiple cellular fields, varying in cell morphology and involved in the formation of different parts of the house.

oikosin

Glycoproteins constituting the larvacean house, secreted from the oikoplast.

oozooid

Asexual generation in the life cycle of salps and doliolids. In both groups, oozooids reproduce by budding from a ventral stolon.

oral siphon

Also buccal siphon, incurrent siphon or inhalant siphon. Opening through which water enters the branchial basket in ascidians.

otolith

Also statocyst or statocyte. Gravity-sensing organ inside the sensory vesicle. It usually consists of a single large cell, with a foot extending to the ventral wall of the sensory vesicle and a round body containing a melanin granule.

papillae

Also adhesive organs or palps. Adhesive protrusions helping ascidian larvae to attach to their substrate. They are located at the anterior end of the larva, below the tunic. In most species, three papillae are present. They are made of three types of cells: collocytes secreting an adhesive material, ciliated neurons playing a role in triggering metamorphosis, and axial columnar cells possessing sensory properties. The papillae end in a hyaline cap. They are usually conical in solitary tunicates, and eversible in colonial tunicates. The set of papillae is also referred to as the adhesive organ.

peripharyngeal band

phorozooid

Asexual generation in the life cycle of doliolids. Phorozooids develop from buds produced by the oozooid having migrated to the paired central rows of the cadophore. They detach from the oozooid while carrying developing gonozooids on their ventral peduncles, before later releasing them.

S sensory vesicle

Main neural concentration in ascidian larvae. It contains the ocellus and otolith, while its posterior part is involved in brain activity.

siphon

stigmata

Also gill slits or stigmatal openings. Orifices in the branchial basket. They are lined with bands of cilia that help filter water. In ascidians, they can vary in shape, with some species having elongated or spiral stigmata.

stolon

Structure connecting zooids to each other or to buds in a colony.

T trophozooid

Also gastrozooid. Asexually produced zooids in the life cycle of doliolids. They develop from buds produced by the oozooid having migrated to the lateral rows of the cadophore. Their role is to feed the colony, including the oozooid.

trunk ganglion

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Glossary of tunicate anatomy

Start with the simplest possible case. Write down what Glossary of tunicate anatomy claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Glossary of tunicate anatomy before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Glossary of tunicate anatomy ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Glossary of tunicate anatomy

In research: Glossary of tunicate anatomy appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Glossary of tunicate anatomy in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Glossary of tunicate anatomy is common in secondary-school and first-year university syllabi. It links to neighbouring topics Glossaries of zoology, Tunicates, so understanding it makes those chapters shorter.
In everyday life: Look for Glossary of tunicate anatomy outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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Frequently asked questions

What is Glossary of tunicate anatomy in simple terms?

Tunicates (subphylum Tunicata) are a group of filter-feeding marine invertebrates. As chordates, they have been proposed to be the closest relatives of vertebrates.

Why does Glossary of tunicate anatomy matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Glossary of tunicate anatomy?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

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