Chapter 13: Cnidarians and Ctenophorans

Nematocysts (cnidae) are

organelles that require stimulation to fire a toxin projectile

What is the fastest animal motion recorded

nematocysts

Cnidaria means

knide (nettle) and aria (suffix for plural)

Why is the Latin suffix plural?

corals are colonial

What environment do Cnidaria live in?

aquatic

Mutualism

both benefit

Commensalism

one benefits, one experiences nothing

Parasitism

one benefits, one experiences a loss

Reefs provide

food and tourism

Are cnidarians radially or bilaterally symmetric?

radially

Are cnidarians triploblastic or diploblastic?

diploblastic with mesoglea

What type of digestion do Cnidarians have?

extracellular but internal

What do Cnidarians lack?

execratory/respiratory system and coelomic cavity

What life cycles do Cnidarians go through?

polyp and medusa

Polyp

asexual (budding, fission, pedal laceration)
sessile
phenotypic plasticity

Medusa

sexual
mobile
tetramerous symmetry

statocyst and ocelli

Statocysts and ocelli of medusae are used for?

orientation and light reception

Why is there variation between polyps and medusas?

phylogenetic constraint

niche

loss of character state

What did hydrozoans lose that affected variation?

medusa

What is the body wall made of?

endodermis, gastrodermis, mesoglea

Mesoglea

acts like an elastic skeleton and covers body
thickest in stalk, thinnest in tentacles

Types of Cnidocytes

adhesive, recoiling, nematocysts

Cnidocil

a modified cilium that acts as a trigger

How does a nematocyst operate?

hydrostatic pressure differences

What type of consumer are polyps?

carnivores

How do polyps capture prey

tentacles

Medusa are

filter feeders

Manubrium

mouth tube

What do corals supplement their diet with?

symbiotic algae

Coral bleaching is when

algae inside corals die which causes corals to turn white

When is it expected for most coral reefs to die?

2050

What type of transmission does a nerve net have?

two-way

What do nerve net NOT have?

myelin

What is the function of the neuromuscular system in annelids? Mammals?

digestive and nerve plexuses

Do Cnidarians have centralization?

No, some have rhopalia

What are covered polyps called

thecate

What are naked polyps called

athecate

Polyp life cycles include

Obelia and Tubalaria

Hydrorhiza

base of polyp

Hyrocauli

stalks of polyp

Velum

margin of bell that projects inward of medusa

What is unique to Hydrozoa in the medusa phase?

entocodon

Entocodon

a developmental layer from ectoderm

How many species of Hydra sp. are in North America?

16

Where do Hydra sp. live?

underside of aquatic leaves

Size of Hydra sp.

> 3 cm

Where is Hydra sp. mouth located?

on top of hypostome

How do Hydra sp. catch prey?

nematocysts on tentacles

Do Hydra sp. reproduce sexually or asexually?

both

Hydra sp. use epitheliomuscular (EM) cells to

cover and contract

Hydra sp. use interstitial cells to

make everything but EM cells

Hydra sp. use gland cells to

secrete adhesive that allows them to attach
found near foot

Where are cnidocytes located on Hydra sp?

whole epidermis

Where are sensory cells located in Hydra sp?

epidermis (synapse and flagellum)

What type of transmission are Hydra sp’s nerve cells?

one way and two way

Man O’ War is in what class?

Physalia

What do Man O’ War use to float?

Pneumatophore

Dactylozooids in Man O’ War

fishing tentacles

Gonozooids or gonophores in Man O’ War

sacs containing empty space and ovaries/testes

What class are most jellyfish in?

Scyphozoa

Class Scyphozoa has what with four arms?

manubrium

What side is the mouth located in Class Scyphozoa?

sumbrellar

What does Class Scyphozoa not have?

velum

How many gastric pouches does Class Scyphozoa have?

four

What leads to a ring canal in Class Scyphozoa?

radial canals from each pouch

Does Class Scyphozoa posses nerve nets?

yes

Where is rhopalia located in Class Scyphozoa?

between lappets

Strobilation

Aurelia makes ephyrae and becomes a strobila

Cassiopeia is known as

upside down jellyfish

What does Cassiopeia not have?

tentacles on umbrella

What is a characteristic feature of Cassiopeia?

oral arm

What organism contains energy producing symbiotic algae (zooxanthellae)

Cassiopeia

Does Class Staurozoa have an absence of polyp or medusa?

medusa

How many arms does Class Staurozoa have?

eight

What develops into a polyp in Class Staurozoa?

nonswimming planula

Class Cubozoa contains

box jellyfish

What life cycle is predominant in Class Cubozoa?

medusa

Pedalium in Class Cubozoa is

flattened tentacle base

How many eyes are on rhopalia in Class Cubozoa?

six

In Class Cubozoa, sumbrella edge turns inward to form a

velarium

Example of Class Cubozoa

Sea wasp in Australia (Chironex)

Class Anthozoa known as

flower animals

What are the three subclasses of Class Anthozoa

Hexacorallia/Zoantharia, Ceriantipatharia, Octocorallia

Anemones and hard corals are in what subclass?

Hexacorallia or Zoantharia

Ceriantipatharia contain

tube anemones and thorny corals

Soft and horny corals are in what subclass

Octocorallia

What partitions the gastrovascular cavity of Class Anthozoa?

septa

The mesoglea in Class Anthozoa is a

mesenchyme containing ameboid cells

Order Actiniaria contain

sea anemones

Order Actiniaria are shaped like

cylinders

Where are the crown of tentacles in Order Actiniaria?

around an oral disc

What shape is the mouth of Order Actinaria?

slit

Slits leading into pharynx to create water flow are called

siphonoglyps

The pharynx in Order Actiniaria lead to

gastrovascular cavity with six chambers

Anemones form mutualistic relationships with

zooxanthellate, hermit crabs, and fish

Order Alcyionaria are

octocorallia corals

What type of symmetry does Order Alcyonaria have?

octomerous

What is order is known as the most beautiful corals?

Alcyonaria

Communication via gastrodermal tubes in Order Alcyonaria

solenia

Photosynthesize, fix carbon, recycle phosphorus and nitrogen, and enhance ability of coral to deposit calcium carbonate are all functions of

zooxanthellae