Cnidaria

Question	Answer
Aboral surface	Side opposite mouth in a radially symmetric animal.
Acontia	Threadlike defensive organs composed largely of cnidae. Thrown out of the mouth or pores when irritated. Laden with numerous nematocysts. Found inside the complete septum of anthozoa.
Anthozoa	Colony forming cnideria that lives its life in the polyp stage. Tentacles surround the mouth at the center of the oral disk. Gonads are in gastrodermis. (Coral. sea anemone)
Biradial symmetry	Radial symmetry except for a pair of siphonoglyphs on either side of the mouth.
Blastula	Stage in the development of multicellular animals in which only 1 cell layer is present. Cell layer is called the blastoderm. The cavity inside is the blastocoel
Budding	Method of asexual reproduction where a piece grows on the cnideria and separates when it is a mature individual. Used by hydra.
Cnidaria	Radially symmetric and characterized by the presence of cnidocytes. Have true tissues with cell-cell communication and are diploblastic. without a mesoderm. Have a polyp with tentacels surrounding a central mouth. Has an epitheliomuscular layer.
Cnidocil	Modified flagellum that acts as a trigger for cnidocyte. Trigger is chemical. not touch.
Cnidocytes	Cells in cnideria that contain nematocystes filled with venom. and an operculum that acts as a spring to fire nematocyst.
Cnidoglandular lobe	Part of the anthozoan septal wall. In front of a ciliated band that creates a current inside the gastrovascular cavity so that the contents are constantly mixed.
Complete septa	Divides the gastrovascular cavity into six compartments connected to each other by septal ostia in the walls of the septa. Increase surface area in the gastrovascular cavity. and have retractor muscles that run along the oral and aboral surfaces. Length of trunk shortens when these muscles contract. and reinflation occurs through intake of water through the siphonoglyphs.
Connexon	Assembly of 6 proteins that form the gap junction.
Cubozoa	Box jellyfish. Have quadrilateral symmetry and have a deadly toxic sting. Polyp produces a single medusa which organizes itself as a free-swimming medusa. Short life cycle in the medusa phase. Has a very unique eye and pedalia. Complex rhopalia (suspended halfway up the upper surface)
Digestive epithelium	Internalized digestive epithelium found in cnideria. Tissue that lines the inside of the digestive tract.
Dimorphic life cycle	Life cycle of the animal includes 2 distinct and physically different body types.
Diploblastic	Organism that has 2 tissues layers. endoderm and ectoderm.
Ectoderm	Outer tissue of an animal. Forms epidermal layer and nervous systems.
Endoderm	One of the primary germ layers. Inner most layer. forms the lining of the digestive tract
Ephyra	Free swimming mini medusa of scyphozoans. Produced by asexual budding of scyphistome. Turns into medusa.
Epithelomuscular cells	Outer surface of cnideria. Have contractile elements as well.
Extracellular digestion	Final breakdown of ingested food to components small enough to be absorbed across a cell membrane. Occurs outside the cell.
Gap junctions	Connects cells together by making their cytoplasms continuous.
Gastric filaments	Part of the gastrovascular system of cniderians. Opening that releases enzymes to digest food. Found in scyphozoans.
Gastrodermis	Endodermal cells that line the gastrovascular cavity (coelenteron) of cnidarians. Nutritive muscular cells.
Gastrovascular cavity	Internal cavity of the cnidarians. Incomplete gut.
Gastrozooid	Polyps in colonial hydrozoans specialized for feeding. Connected to eachother by a branching of the digestive tract so that food can pass from one to the other. Can fracture and regrow.
Gastrulation	Stage in embryological development in which the blastula is converted into gastrula. Cells migrate toward the inside of the embryo from the region where the blastopore will form to create the second germ layer.
Gonozooid	Polyp in colonial hydrozoan specialized for producing medusa. Reproductive stage in the life cycle (gonangia) has a modified polyp inside which creates disk-like structures through which the medusae will be released.
Hydranth	Feeding zooid in a hydroid colony having an oral opening surrounded by tentacles. (gastrozooid)
Hydrostatic skeleton	Formed from a fluid filled and closed cavity surrounded by a body wall containing muscles oriented in different directions. Muscular contractions maintaining the rigid form or change the shape of the organism allowing movement. (gastrovascular cavity in hydrozoa)
Hydrozoa	Class of the phylum cnideria. Have both the polyp and medusa in their life cycle. Carnivorous and form colonies of interconnected polyps encrusted on the substrate. Grows by asexual budding and through gonozoids that produce medusae.
Incomplete digestive system	Only has a mouth and no anus.
Incomplete septa	Sheet of tissue that separates the colenteron of anthozoa. Attached to the body wall but has free ends suspended in the coelenteron. Armed with cnidocytes to immobilize ingested prey. Digestive glands secrete enzymes for initial breakdown. Also has gonads.
Medusa	Free swimming mobile stage of the cnidarian lifecycle. Reproductive stage of the life cycle has mature gonads that form either male or female medusa and are important in scyphozoa. cubozoa and hydrozoa.
Mesoglea	Jelly-like layer found between the ectodermal and endodermal cell layers of diploblastic organisms. Acts as a type of cement holding the two layers together. Only has a few cells.
Myoneme	Strands of contractile myofibers found in single cells. Allow the cell or portions of the cell to contract and change its shape. Arranged longitudinally in the outer epithelial muscular cells from the oral to the aboral side. Important in movement in the hydrostatic skeleton.
Nematocyst	The organelle found in cnidocyte cells that are unique to cnidarians. Stinging or eversible portion of the cell. Can drill into. entangle or stick to potential prey.
Nerve net	nerve cells formed from the ectoderm which wind between epitheliomuscular cells. Not centralized and no cephalization.
Nutritive muscular cells	Cells that form the gastrodermis lining the inner cavity of cnidarians. Absorb and digest food. and move and change shape of the myoneme portion of the cell.
Oral surface	Surface with mouth.
Oral-aboral axis	Line that goes through the mouth to the other side.
Pedalia	Flat. enlarged base of the tentacles in some cnidarians (cubozoans). Helps pass food into mouth.
Pigment cup	Along with pigment spot. sensory structure that detects light. The hood up above creates a shield. As the organism tips. different sets of pigments get lit up. which allows the organism to decide which way to move.
Planula larva	Larval. solid. free swimming stage of cnidarians. Has 2 cell layers. ciliated ectoderm and inner endoderm.
Polyp	Sessile. asexual stage in the cnidarian life cycle. Independent in some species. or form colonies. Can strobilize and produce medusa. Hydra spend their life cycle existing only as a polyp.
Rhopalium	Sensory structures found around the bell margin of the medusa. Contains a statocyst for balance. and ocelli for light detection. Allows medusa to be oriented.
Schyphozoa	Commonly called jellyfish. Most of life cycle is medusa. Has a short lived polyp that is called a scyphstome that undergoes strobilization to form the strobila from which ephyra are formed. Much larger than hydrozoans. Have an enlarged mesoglea.
Scyphistoma	Polyps settle to the ground. Strobilize to produce ephyra. Results from the settling of the planula.
Septa	Sheets of tissue that separate 2 compartments or cavities. Can be complete or incomplete (anthozoans). Increase the surface area of the gastrovascular cavity. Incomplete septa contain cnidocytes and digestive enzymes to help digest ingested prey.
Siphonoglyphs	Located on either side of the anthozoan mouth. Propels water in the gastrovascular cavity.
Spermaries	Organ in which male gametes are developed. These structures are present on hydra. Important for sexual reproduction.
Statocyst	Has at least 1 solid statolith surrounded by sensory cilia. As the position or the organism changes. the statolith rolls. stimulating different cilia.
Strobila	Stage in the scyphozoan life cycle formed from lateral fission of the scyphostome. Produces ephyra. Important in the life cycle of the scyphozoan.
Strobilization	Process that converts scyphostoma into strobila. Lateral fission produce small disk-like ephyra that develop into the adult medusa.
Tissue-grade	Animals that have tissues but no organ systems.
Triploblastic	Organisms with an endoderm. ectoderm and mesoderm.
Velum	Thing flap of tissue found around the inner surface of the bell of a hydrozoan's medusa. Improves swimming ability of hydrozoans. (hydrozoan autoapomorphy)

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	Created by Shareef Akbari about 7 years ago