Cnidaria

Coelenteron

gastrovascular cavity opens to the exterior via a mouth surrounded by more whorls of tentacles

Polyp

one of two different body forms occurring in cnidarian life cycles; resembles a flower and its stalk; chiefly attached, sessile, benthic animals with a mouth-up orientation

Manubrium (hypostome)

opposite end of the column from the pedal disc; an elevation with the mouth at its summit; situated in the center of an oral disc

Periderm

a chitinous exoskeleton excreted by the pedal disc and column of the polyp which provides protection and attachment to the substratum

Medusa

has the shape of an umbrella or a bell

Epidermis

an outer epithelium

Gastrodermis

lines the gutlike coelenteron and joins the epidermis at the mouth

Stolon

tubular body wall outgrowth that includes the coelenteron, from which zooids bud at intervals along its length

Coensarc

common flesh; a continuous sheet of tissue (also called a stolonal mat) that unites the zooids and attaches the colony to the substratum

Solenia

a network of hollow gastrodermal tubes located between the upper and lower epidermal surfaces of the coenosarc

Fixed-length budding

one form of zooidal budding in which the first zooid grows to a fixed length and then buds another zooid from its column below the whorl of tentacles

Axial-polyp budding

lateral zooids, which are often numerous and dense, cover the sides of the main stem and branch stems

Ganglion

concentration of neurons that serves as a brainlike, integration center; receives sensory input, integrates that information with other inputs, and generates motor output

Cnidocyte

a combined sensory-effector cell that plays a central role in capture and defense

Cnida

a fluid-filled membranous capsule containing a long tubular invagination of the capsule wall

Nematocysts

one of the three types of general cnidae; thick-walled cells that often have spines or barbs on the surface of the everted tubule

Operculum

a hinged lid that may cover the firing site

Cnidocil

the sensory cilium of the nematocyte that is mechanoreceptive; nonmotile and stiff

Ciliary cone

the sensory cilium of the nematocyte that is mechanoreceptive; motile

Septa

vertical partitions that divide the coelenteron, mesenteries

Bleaching

loss of pigmented algae which leaves the white calcareous skeleton visible through now transparent tissue

Septal funnel

found in the septa; also known as the subumbrellar funnel; originates as the invagination of the oral disc and extends deeply into the septa

Strobilation

the process in which, at the appropriate time of the year, under the influence of hormonal and environmental factors, scyphistomae asexually reproduce young medusae

Hydranth

water flower; the 'flower' of the hydropolyp

Pedicel

stem or stalk; slender column of the hydropolyp

Hydroids

sessile, benthic colonies

Monomorphic colony

consists of only gastrozooids

Gastrozooids

the feeding hydranth of a colony

Medusa buds

from which free-swimming medusae originate within monomorphic colonies

Polymorphic colonies

have gastrozooids and at least one other form of permanently attached zooid

Gonophore

widespread medusa zooid; indifferentiated from medusae that produce gonads, but lack some or most other medusan traits

Gonozooids

specialized gastrozooids that bear medusa buds and gonophores

Coral Reef Formation

Growth on calcareous skeletons, coenosarc connections, reef-building colonies.

Bleaching in Coral Reefs

• Stress-induced expulsion of symbiotic algae.

• Causes: Temperature changes, UV exposure, salinity changes.

• Impact: Can lead to coral mortality and ecosystem damage.

scyphozoa

• Jellyfish group including stalked and free-swimming forms.

• Characteristics: Tetramerous symmetry, bell-shaped body, sensory rhopalia.

Cubozoa

• Jellyfish group including box jellies.

• Characteristics: Cubic, colorless bell, potent venom, developed eyesight.

Reproduction in Scyphozoa and Cubozoa

• Sexual reproduction, often with unusual mating behaviors.

• Methods: External fertilization, brooding, release of embryos into the water column.

hydrozoa

• Group including fire coral, hydra, and Portuguese man-o-war.

• Characteristics: Mostly colonial, both freshwater and marine species, polymorphic colonies.