Cnidaria

Gastrodermis

The layer of cells that forms the lining of the GVC

Epidermis

The outermost layer of cells in a cnidarian

Strobila

.The life cycle stage in scyphozoans that divides transversely to produce many ephyra through asexual reproduction

Gonophore

A structure that will develop into a medusa (this structure is produced by a hydrozoan polyp)

Medusa (life cycle)

Stage of life cycle responsible for sexual reproduction, has gonads - in hydrozoans it is called the hydromedusa while in scyphozoans it is called the scyphomedusa

Planula

The larval stage of both scyphozoans and hydrozoans

Gonozooid

A colonial hydrozoan polyp that is specialized for the production of gonophores

Scyphistoma

A scyphozoan polyp

Polyp

Adult life cycle stage of cnidarians that usually attaches to surfaces

Ephyra

A young medusa in scyphozoans

Medusa

Adult life cycle stage of cnidarians that is usually free-swimming in the water

GVC

A hollow digestive space that has only one opening

Mesoglea

A jelly-like matrix located in between the gastrodermis and the epidermis - there are no living cells contained in this matrix

Mesoenchyme

A jelly-like matrix located in between the gastrodermis and the epidermis - this matrix contains living cells

Gonad

An organ that produces gametes (eggs or sperm) - in females this organ is called an ovary while in males this organ is called a testis

Which three of the following five features are common to both Anthozoa and Medusozoa? Select all three correct answers. Cnidae (nematocysts) Radial symmetry A life cycle with both a polyp stage and a medusa stage A complete digestive tract (with a separate mouth and anus) A gastrovascular cavity (GVC)

Cnidae Radial symmetry A GVC

Consider the polyp stage of the life cycle in hydrozoans. Which three of the following six statements are TRUE? (Select all three correct options.) Gastrozooids are polyps within a colony that are specialized for feeding. In colonial hydrozoans, all the polyps within a single colony are genetically identical. Colonial polyps often have a chitinous exoskeleton called a perisarc. In all species of colonial hydrozoans, each individual polyp within the colony is capable of feeding and of producing gonophores. Solitary hydrozoan polyps (such as Hydra) have a thin layer of mesenchyme separating the epidermis and the gastrodermis. In all species of hydrozoans, the polyps remain connected to each other after asexual reproduction, forming large colonies.

Gastrozooids are polyps within a colony that are specialized for feeding. In colonial hydrozoans, all the polyps within a single colony are genetically identical. Colonial polyps often have a chitinous exoskeleton called a perisarc.

Which one of the following statements comparing the life cycles of anthozoans and medusozoans is TRUE? In medusozoans, the polyp stage of the life cycle reproduces both sexually and asexually, while in anthozoans, the polyp stage only reproduces asexually. Both medusozoans and anthozoans have a medusa stage in their life cycle. All medusozoans and anthozoans produce planula larvae that are capable of feeding. In both medusozoans and anthozoans, sexual reproduction results in the production of planula larvae.

In both medusozoans and anthozoans, sexual reproduction results in the production of planula larvae.

Consider the following two medusozoan taxa: scyphozoa and hydrozoa. Which one of the following statements is TRUE? Scyphozoans have a life cycle that includes both sexual and asexual reproduction, while hydrozoans only reproduce sexually. In the polyp stage of the lifecycle, scyphozoa have tentacles while hydrozoa do not. In the medusa stage of the life cycle, most scyphozoa have a velum while most hydrozoa do not. In the medusa stage of the lifecycle, the GVC in scyphozoa has only a few branches (just the ring canal and four radial canals), while the GVC in hydromedusa has many more branches. In the medusa stage of the life cycle, scyphozoa have rhopalia as their main sensory structures while hydrozoa have tentacular bulbs.

In the medusa stage of the life cycle, scyphozoa have rhopalia as their main sensory structures while hydrozoa have tentacular bulbs.

Which one of the following statements about nematocysts is FALSE? (Hint: see pages 39 and 46) Some nematocysts can be used for capturing prey. Nematocycts play a large role in cnidarian reproduction because they can function as sperm cells. When nematocysts are stimulated, they discharge, such that the capsule opens and rapidly shoots out one end of the thread while the other end of the thread remains attached to the capsule. When you view a microscope slide of nematocysts, you should be able to see the pale, shiny capsules of undischarged nematocysts and the blue stained capsules and threads of the discharged nematocysts. Some nematocysts can penetrate the skin of prey or potential predators to inject venom that can cause paralysis or death. There are different types of nematocysts. For example: glutinants produce a sticky adhesive, penetrants have a barbed base, and volvents have a tightly coiled thread.

Nematocycts play a large role in cnidarian reproduction because they can function as sperm cells.

Nematocysts

These highly specialized organelles are composed of a long thread that is tightly coiled within a capsule (they are a type of cnidae found in most cnidarians)