Hydra, jellyfish, coral, & sea anemones

I. radial symmetry

II. dimorphic development

III. nematocysts, specialized organelles produced by cnidocytes

Radial

Compass jellyfish

General Characteristics

• They are radially symmetrical; oral end terminates in a

mouth surrounded by tentacles.

• They have 2 tissue layers

• Outer layer of cells - the epidermis

• Inner gastrodermis, which lines the gut cavity or

gastrovascular cavity (gastrodermis secretes

digestive juices into the gastrovascular cavity)

• In between these tissue layers is a noncellular jelly-like

material called mesoglea

Characteristics• Diploblastic

– Epiderm & hypoderm

Polymorphism : more than one body form

1. Polyp

2. Medusa

Cnidarian Body Plans

Polyp form

• Tubular body, with the mouth directed upward.

• Around the mouth are a whorl of feeding tentacles.

• Only have a small amount of mesoglea

• Sessile

Medusa form

• Bell-shaped or umbrella shaped body, with the mouth is directed downward.

• Small tentacles, directed downward.

• Possess a large amount of mesoglea

• Motile, move by weak contractions of

body

Forms of Cnidarians

Polyp

• tentacles around the mouth

• Sessile

Polyp (Hydra)

Polyp (sea anemone)

Medusa

• Umbrella shape

• Tentacles around mouth

• Motile, Free-swimming

Dimorphic Life Cycle

Colonial hydrozoan

Tentacles

• Have nematocysts (stinging cells)

• Coiled thread discharges like a harpoon

• Contains neurotoxin

• Paralyzes prey

Stinging Organelles

• Prey capture is enhanced by use of specialized stinging cells called

cnidocytes located in the outer epidermis.

• Each cnidocyte has a modified cilium - cnidocil, and is armed with

a stinging structure called a nematocyst.

• The undischarged nematocyst is composed of a long coiled thread

• When triggered to release, either by touch or chemosensation, the

nematocyst is released from the cnidocyte and the coiled thread is

everted

• Some nematocysts function to entangle the prey; others harpoon

prey and inject a paralyzing toxin

Discharged nematocyst

Hydrazoan stinging and capturing prey

Habitat

Aquatic

Most Marine

Few fresh-water

Feeding

Lion’s mane eats another jelly

Carnivores (predators)

Process of feeding

1. Tentacles sting prey with nematocysts

2. Tentacles grab prey

3. Prey pulled into mouth

4. Prey stuffed into gastro-vascular cavity (GVC)*

5. GVC makes enzymes, extra-cellular digestion

6. Undigested food back out mouth

*incomplete digestive tract (no anus)

Digestive System

Nutrition

• Cnidarians are carnivores with hydras and corals consuming plankton and some of the sea anenomes

consuming small fishes

• They use tentacles to capture prey and direct it toward the mouth so that it can be digested in the

gastrovascular cavity via secretions from gland cells (extracellular digestion); some food is phagocytized by

special cells and digestion occurs intracellularly

• The gastrovascular cavity exists as 1 opening for food intake and the elimination of waste

• There is no system of internal transport, gas exchange or excretion; all these processes take place via

diffusion

Respiration

• Via diffusion

Excretion

• Via diffusion

Response

Sensory cells

1. Chemoreceptors (chemicals)

2. Thigmoreceptors (touch)

3. Photoreceptors (light)

Ocelli (eyespots)

4. Statocysts (balance)

Locomotion

A. Medusa motile, free-swimming

A. Polyps sessile

Exceptions:

1. Hydra tumbles on tentacles

2. Sea anemones glide on pedal disc

Reproduction

1. Asexual

budding from polyps or medusa

2. Sexual

a. Medusae release sperm & eggs

b. Some monoecious, some dioecious

Larvae free-swimming

Cnidarian Taxonomy

CNIDARIA

Phylum:

Cnidaria: (formerly called Coelenterata)

Class:

I. Hydrozoa: (hydroids)

II. Scyphozoa: (jellyfish)

III. Anthozoa: (corals)

Class Hydrozoa: The Hydras

• Polyp phase is dominant

Phylum: Cnidaria

Class: Hydrozoa: (hydroids)

the most part colonial species that have alternating medusa and polyp stages

This order has a chitinous exoskeleton

Hydrozoa are colonial and create an aragonite (calcium carbonate based) skeleton

The best known of these complex colonial organisms is the Portuguese man-of-war (Physalia physalis).

Colonial Hydrozoans

• Fire Corals– NOT TRUE CORAL

• Hydrozoan colony

– TRUE CORAL• Anthozoan colony

Phylum: Cnidaria: (formerly called Coelenterata)

Class:

Scyphozoa: (Jellyfish)

The class Scyphozoa is generally characterized by having a much larger medusa stage than polyp stage

Scyphozoan Life Cycle

Aurelia aurita (Moon jelly)

Class Anthozoa

Class Anthozoa: Anemones & Corals

• Appear like plants but are animals.

• Polyp form is dominant.

• Corals build calcium shells to protect themselves

• Have symbiotic relationship with algae.

• Can build extensive masses which can form land

masses.

Anemone

Coral Polyps

Class Anthozoa

• Exclusively marine; there is no medusa stage

• At one or both ends of the mouth is a ciliated groove called the

siphonoglyph; generates a water current and brings food to the gastrovascular

cavity

• Possess a well developed pharynx

• The gastrovascular cavity is large and septa or

mesenteries; increase surface area for digestion

or support

Class Anthozoa

Corals obtain much of their energy from microscopic photosynthetic algae (zooxanthellae) or dinoflagellates

that live symbiotically inside the cells of the coral

Zooxanthallae is a genus among the Dinoflagellata

It will loose its flagella and live in the tissue of corals

Phylum: Cnidaria

Class: Anthozoa: (corals)

In general, the class is comprised of the vast majority of species commonly referred to as sea anemones

and corals.

existing exclusively as polyps, completely without a medusa life stage

Anthozoa into three subclasses:

I. Octocorallia,

II. Hexacorallia,

III. Ceriantipatharia

Class: Anthozoa: (corals)

Sub class: Octocorallia (Soft corals)

Octocorallia: commonly known as soft corals

not very closely related to the true corals (Scleractinia)

The polyps of octocoralliarians have eight tentacles

divided into five or six orders (Telestacea, Alcyonacea, Gorgonacea, Pennatulacea, Helioporacea, and

sometimes Stolonifera)

(blue coral)Tubipora musica

Family Plexauridae:

Menella sp.

Colony shape: bushy

Habitat : depth above 10 , with clear water ( visibility 8 m)

Family Plexauridae :

Dendronepthya sp. Kukenthal, 1905

Family Plexauridae :

Echinomuricea sp. Verrill,1869

Class: Anthozoa: (corals)

Sub class: Octocorallia

Most do not develop skeletons

Most octocorals form spicules within their tissues, and some produce calcified holdfast structures or long, rodlike

internal supports.

All of the octocorals are colonial, including the sea fans and sea whips (Gorgonacea).

The scleractinians are the largest group of anthozoans, with approximately 3600 extant species

This prominent taxon provides the calcium carbonate building blocks for the world’s coral reefs

calcium carbonate skeleton is secreted by the epidermis and is present in all members of this order

The order Scleractinia is usually divided into 18 families

Class: Anthozoa: (corals) Sub class: Hexacorallia

Order: Scleractinia (True Stony Corals)

Class: Anthozoa: (corals) Sub class: Hexacorallia

Order: Scleractinia (True Stony Corals)

Scleractina are classified by morphological features of colony growth and various soft-tissue features

The Acroporidae are mostly in two genera, Acropora and Montipora. These are fast-growing forms with both asexual

and sexual reproduction.

Some scleractinians, like members of the genus Fungia, are solitary and can be relatively large: up to 50 cm in diameter

FungiaAcropora nasuta Montipora capricornis

Class: Anthozoa: (corals)

Sub class: Hexacorallia

Hexacorallia is comprised of six orders, two of which are extinct, order Rugosa and Tabulata.

I. order: Actinaria : sea anemones

II. order: Zoanthidia : colonial anemones

Class: Anthozoa: (corals) Sub class: Hexacorallia

Order: Actinaria (sea anemones)

I. Most of the soft-bodied anthozoans known as sea anemones are classified in the Actinaria

II. Actinarians generally have column-shaped bodies with the mouth at one end and a muscular pedal disk for

attachment to substrates at the other.

I. Actinarians have soft bodies and do not form hard parts, some coat themselves with sand grains and/or

mucuslike secretions.

Sea Anemones (with sea urchins)

Class Anthozoa: Sea Anemones

Class: Anthozoa: (corals) Sub class: Hexacorallia

Order: Actinaria (sea anemones)

I. Most actinarians are relatively sessile, either not moving or moving very slowly by contractions of the

pedal disk

II. Some anemones burrow into sand, and a few can swim short distances

III. Actinarian anemones can reproduce either sexually or asexually

IV. They do not form true colonies with permanent tissue connections between members, as seen in the

superficially similar zoanthiniarian anemones

Class: Anthozoa: (corals)

Sub class: Hexacorallia

Order: Zoanthidia

Small group of polypoid anthozoans that differ from most sea anemones (Actinaria) in details of internal

anatomy.

unlike most sea anemones, zoanthiniarians can form true colonies in which all members are connected by

common tissue.

Zoanthiniarians make no hard parts and leave no fossil record

However, they are more closely related to extinct coral taxa (Tabulata and Rugosa) than they are to other

soft-bodied anthozoans

Genus: Zoanthus

Class: Anthozoa: (corals)

Sub class: Hexacorallia

Order: Zoanthidia

Sub order: Brachynemina

Family: Zoanthidae

Genus: Zoanthus

This taxon is often referred to as intermediate in form between hard corals (Scleractinia) and sea anemones

(Actiniaria), as most species lack a skeleton and yet are colonial.

Zoantharians are widely distributed and are particularly common in subtropical and tropical regions, where

they are one of the major benthic components of coral reefs.

Some species contain unique chemicals such as palytoxin or norzoanthamine

Where seen?

Genus: Zoanthus

Like a carpet of tiny flowers, these animals are often seen on:

I. shores,

II. growing on stones

III. as well as under seagrasses in vast seagrass meadows.

IV. They may form a dense carpet that covers large areas of several square metres

Genus: Zoanthus

What do they eat?

Zoanthus spp. do not need to be fed directly, since they obtain much of their nutritional requirements

from their symbiotic zooxanthellae.

They must therefore be provided with adequate illumination to thrive.

They also ingest dissolved organic substances from the water, as well as fine particulate matter.

Some species do not take large particles of food, while others do take and eat such things as flake

food, blackworms, shrimp, and sea urchin eggs.

Zoanthids mainly reproduce asexually, although there is a limited amount of sexual reproduction

Genus: Zoanthus

Zoanthids differ from true sea anemones, which belong to the subclass Actiniaria, based on details of

their internal anatomy and the fact that zoanthids form true colonies in which the individual polyps

are connected by a common tissue, the coenenchyme.

Members of this genus are the most colourful of the zoanthids, being shades of green and brown

typically, but sometimes fluorescent red, orange, pink, blue, yellow, or gray, and usually two-toned

Genus: Zoanthus

These Anthozoans consist of a skeleton made from detritus and sand particles which is not hard enough to

sustain the currents, but it definitely helps in forming huge colonies in areas with high sediment rates.

The zoanthids form a major constituent of the rocky intertidal macro benthos

Genus: Zoanthus

Zoanthus sp. have soft bodies covered with a leathery skin, called the cuticle, which gives them

protection.

Their polyps have fairly short stalks topped with a small flat oral disc.

Tentacles radiate from the outside of the oral disc and are usually expanded day and night.

The results of the present study show that the nucleotide sequence of this mitochondrial gene fragment

is identical in all the examined samples and is consistent with the reported sequences of the species of

Zoanthus sansibaricus.

What this study obtained is undoubtedly a systematic report from the color variation of the available

samples in the Iranian islands of the Persian Gulf. Observation of brown, green, gray, red, pink and

purple polyps, green and brown tentacles, green, red, blue and pink oral color with oral disc green,

red, blue, pink and gray colors confirms a wide range of colors in this species.

Morphological and Genetic studies of Zoanthid Genus Zoanthus in some coral islands of the Persian Gulf: Qeshm, Larak and Kish

Atoosa Noori Koupaei* , Pargol Ghavam Mostafavi , Jalil Fallah Mehrabadi , Seyed Mohammad Reza Fatemi

Using in situ field examination integrated with 16S rDNA sequencing and phylogenetic analysis

In this study, diversity of shallow water zoanthids off the Qeshm Island, the largest island in the

Persian Gulf, was investigated for the first time.

the presence of three zoanthid species in the inter-tidal and shallow water zone of Qeshm

Island were demonstrated

Zoanthus sansibaricus (n = 12) with five morphotypes,

Palythoa cf. mutuki (n = 10) with two morphotypes

Palythoa tuberculosa (n = 4) with just one morphotype.

Natural Products Isolated from the Order Zoantharia

1. Zoanthusterone : is a representative ecdysteroid isolated from a Zoanthus

2. Prostaglandins like PGA2 : isolated from Palythoa

3. zoanthoxanthin: natural products based on the highly fluorescent

4. parazoanthoxanthin A : has shown significant anticholinesterase activity

5. Palytoxin