module 4 : marine invertebrates · 2 two oceans aquarium volunteer manual – module 4 –...

Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 1

Module 4 : Marine Invertebrates TABLE OF CONTENTS

Invertebrates 2

Introduction 2

Meaning of Important Biological terms 7

Phylum Porifera 9

Phylum Cnidaria (Coelenterata) 11

Phylum Platyhelminthes 21

Phylum Sipunculida 23

Phylum Annelida 24

Phylum Arthropoda 29

Phylum Bryozoa 42

Phylum Mollusca 43

Phylum Echinodermata 60

Phylum Chordata 68

Two Oceans Microscope 70

Key Concepts Underline or highlight the concepts as you read through the notes.

1. Why is classification important? 2. Name of Phylum and main characteristics. 3. Methods of feeding 4. Different kinds of symmetry and the advantages of each. 5. Identify species found at touch pool and microscope

o Interesting facts about the species o method of feeding o habitat, o parts of the animal and its function


What is an Invertebrate?

An invertebrate is an animal without a backbone (vertebral column). The majority of animals in the animal kingdom are invertebrates.

INTRODUCTION

ORGANISMS: THEIR VARIETY AND CLASSIFICATION

Imagine having over a million living animals around without names, which are not grouped in any way. If this were the case it would be impossible to remember the details of the organisms. If they were systematically ordered, one would only need to remember the basic construction pattern and the common characteristics of each group to make sense of the animals.

Why is classification important?

helps us enormously to identify the animal or plant and give it an acceptable scientific name

to work out the relationships between the different groups of animals and plants

to enable scientists to communicate and share information about organisms

to show interesting evolutionary phenomena

to help understand patterns of development of life on earth.

The science of classifying organisms, whether plants or animals into groups, is known as taxonomy.

CREATING ORDER OF THE LIVING WORLD

Certain animals have certain characteristics in common and they are grouped together in a hierarchical system (from many to few characteristics)

The highest ranks in the animal kingdom are called PHYLA (singular: phylum). This rank is called a DIVISION in the plant kingdom.

Because of ever increasing differences in the external and internal structures between organisms, they are further grouped into lower ranks that are called CLASS, ORDER, FAMILY, GENUS AND SPECIES in ‘descending’ order.

For instance, a species is a specific animal, which belongs to a genus (of very similar animals), which belongs to a family (of very similar animals), etc.

In the table below a comparison is made between the way that animals are classified and the way that supermarket products such as coffee is classified and arranged on the supermarket shelves.


ANIMAL KINGDOM NON-LIVING WORLD

Phylum

Class

Order

Family

Genus

Specie

Arthropoda

Crustacea

Decapoda

Grapsidae

Grapsus

Grapsus fourmanoiri (Green rock crab)

Beverages

Coffee

Instant Coffee

Pure Instant coffee

Nescafé

Nescafé classic

NAMES The strange sounding names of living organisms are derived from Greek or Latin and are continuously given to organisms as new species are discovered and technology developed. They describe a common, outstanding characteristic of each phylum, class, order, family, genus and species. For example the phylum Arthropoda comes from the Greek arthron - joint and podos - foot and all animals belonging to this phylum have jointed legs.

GENUS and SPECIES names

It is by these two names that all the different recorded organisms on earth are distinguished from each other.

In scientific papers and books these two names are usually printed in italics, first the (Genus) generic name (with capital letter) and then the species name with small letter e.g. Grapsus fourmanoiri (Green rock crab).

Below is a key to indicate animals which might be found at the Touch pool and Microscope.

KEY

Touch Pool

Microscope


The table below illustrates PHYLA that contains examples of marine invertebrate animals

PHYLUM: PORIFERA

Has pores

Skeleton made of spicules

Asymmetrical (no symmetry)

No tissues or organs

Sponges

PHYLUM: CNIDARIA

Stinging cells (nematocysts)

Hollow gut with a single opening

Hydrostatic skeleton

Radially symmetrical

2 body forms: polyp and medusa

Anemones and Zoanthids

Hard Corals

Soft Corals and Sea Fans

Jellies

Hydroids

Bluebottles

PHYLUM: PLATYHELMINTHES

Flat worms

Bilateral symmetry

Not segmented

Eye spots

PHYLUM: SIPUNCULIDA

Bilateral symmetry

Not segmented

Introvert and trunk

Flatworms

Peanut worm


PHYLUM: ANNELIDA

Ring – like external bands - segmented

Bilateral symmetry

Bristle worms

Jaws or modified mouth parts

Sedentary (live in tubes) worms

Free living worms

PHYLUM: ARTHROPODA

Jointed limbs

Exoskeleton made of chitin

Moults to grow bigger

Bilateral symmetry

Sea spider

PHYLUM: ARTHROPODA – Subphylum: Crustacea

Exoskeleton form a shield = carapace

2 pairs of antennae

Hermit crabs True crabs

Isopods and Amphipods

Barnacles

Shrimps, Lobsters, Prawns

PHYLUM: MOLLUSCA

Soft body

Bilateral symmetry

Most examples have a shell

Limpets

Bivalves


Sea snails

Chitons

Sea slugs or Nudibranchs

Octopus Squid

PHYLUM: BRYOZOA

Look like seaweeds, corals or hydroids

Build colonies

PHYLUM: CHORDATA

Bilateral symmetry

Include all Vertebrate classes

All have similar features in larval stage = tadpole like

Dorsal Nerve chord

Stiff dorsal rod (notochord)

Pharyngeal gill slits

Moss or lace animals

Sea squirts

Individual or colonial

Cellulose casing = tunic

PHYLUM: ECHINODERMATA

Spiny skin

Pentaradial (5 part ) symmetry

Endoskeleton ( on the inside)

Tubefeet

Starfish

Sea urchin

Brittle star

Sea cucumber

Feather star


Fig 11. Showing radial symmetry of sea anemone

Central point

Meaning of Important biological terms

1. Types of Feeding Methods

Filter feeders – An animal that uses some body part to strain very small animals or plants (plankton ) from water

Herbivore- An animal that eats plants or algae

Detritus feeder or detritivore – animal that feeds on dead material (detritus). This is mainly plant material.

Carnivores – An animal that eats other animals. There are two methods by which they acquire their prey viz. Hunting or scavenging for dead remains of animals

Predators – Animals which catches, kills and eats its prey. Scavengers – Opportunistic animals that will attack and eat prey that are injured or dead. Omnivores – Animals that eat both plant and animal material.

2. Types of body shapes = Symmetry

Symmetry in biology is the balanced distribution of duplicate body parts or shapes. The body plans of most multicellular organisms exhibit some form of symmetry.

Asymmetrical – No symmetry. A small number of animals show no symmetry (are asymmetric).

Radial Symmetry

The arrangement of the body of an animal in which parts are arranged around a single central point.

Most animals with a circular body plan are radially symmetrical e.g. sea anemones(see fig 11)


Bilateral Symmetry The body of the animal can be divided into two equal halves. The left half is exactly the same shape as the right. It has a definite front and back, and a left and right side e.g. crabs.

Colonial- descriptive of organisms produced asexually which remain associated with each other – may retain tissue contact. Also describes sexually produced organisms that form semi permanent aggregations in space

Quick review 1. Match the term with the correct explanation.

Column A Column B

Invertebrates Describes the body plan of the animal

Symmetry Animals which eats small microscopic animals or plants

Filterfeeder Animals which eats plants

Carnivore Animal where the left side is exactly the same as the right side

Bilateral symmetry Animals which eats other animals

Radial symmetry Animals with a circular body plan

Herbivore Animals without a backbone

2.

In the table below number the names given from highest classification to lowest classification.

Genus Phylum

Class Family

Order Species

3. Why is classification so important in the naming of animals?


CHARACTERISTICS

Has pores

No upper or lower side, no front or back - grows in any direction.

No true tissues or organs present.

All members are sessile ( attached) and exhibit little detectable movement.

No symmetry = asymmetrical

PHYLUM: PORIFERA

(pori = pores and fera = bearer)

SPONGES

Habitat Sponges prefer to grow on a solid base such as rocks in the infratidal/intertidal zone where they may be exposed at a very low tide. They are found under rock ledges and in caves away from direct sunlight. Many are found sub-tidally along the South African coast.

Description Sponges are the least animal-like of all marine animals. They look like bits of coloured bath sponge. They can be red, orange, blue, purple, brown or grey in colour and are easily recognised by many small holes in their surface. The body shape is variable, e.g.

Did you know?

A sponge has a three-dimensional scaffolding or lattice that supports the jelly-like body.

This lattice is formed of little spikes of silica, calcium carbonate or a tough fibre called spongin. A natural bath sponge is the skeletal remains of a sponge supported by spongin.

Living Shores: Figure 175

Flagella beat to create water movement

for feeding


flat encrusting, tubular, globular.

Feeding They obtain their food by filtering particles of organic matter and microorganisms e.g. bacteria out of the water. Sponges are thus very important ecologically as they filter the shallow coastal water. Reproduction Gametes form in the mesenchyme. Eggs are fertilised and then released. The resulting multicellular larvae swim for a few days, then settle and crawl to a favourable substrate. Some sponges are hermaphroditic. Asexual reproduction can also occur, through fragmentation or budding.

Predators Animals such as flat worms and bristle-worms eat some sponges. The varying bright colours of the sponges may act as a warning to predators that they are unpalatable (the spicules may act as an irritant).

Sponge Bob and his friends are characters in a cartoon called Sponge Bob Square Pants . Sponge Bob walks. He talks. He flips perfect Krabby patties. Of course real sponges can’t do any of that – they don’t have eyes, lungs, a heart, or other organs. A sponge is made up of a collection of individual cells that work together. That is why a sponge can grow back together after being broken into small pieces, which sometimes happens to sponge Bob. Chances are the sponges you clean with – the kind that look like Sponge Bob – aren’t from the sea but are made from a material called cellulose.


PHYLUM: CNIDARIA (COELENTERATA) Cnida = nettle (stinging)

Living Shores: Figure 180 A

Detail of the body wall of a cnidarian

Living Shores: Figure 180 B

CHARACTERISTICS Multicellular animals. Body is essentially a sac with two cell layers in the body wall and a single opening, the

mouth. The mouth is surrounded by tentacles, which contain stinging cells (nematocysts)

that assist in capturing the prey. They are built on a circular body plan and are radially symmetrical. There are two common forms: (also see next section figure 180 A)

o the polyp which attaches itself to the rock for example the sea anemone and o the medusa which is bell shaped and floats mouth downwards in the water

for example the jellyfish.


PHYLUM CNIDARIA

CLASS HYDROZOA SCYPHOZOA ANTHOZOA

Jellyfish or jellies Sea anemones, zoanthids, sea fans, soft coral, hard coral

ORDER HYDROIDA SIPHONOPHORA

Hydroids Bluebottles

Polyps solitary or bud to form colonies

Floating colonies of several polyp-like or jelly-like individuals that are attached to a stem or disc.

Umbrella shaped jellies These animals have a barrel shaped body with a mouth at one end. The mouth is surrounded by a set of tentacles used for catching food. Medusoid stage completely lacking.


Clownfish living amongst the tentacles of a sea anemone

CLASS: ANTHOZOA

ANEMONES

Habitat Some anemones, such as the plum anemones live in small holes and cracks in intertidal zone in rock pools. Others live in caves and on reefs below the low tide. Sandy anemones crowd into sandy gullies.

Description Anemones are simple solitary polyps. They look like brightly coloured flowers and show a great variety of sizes and colours. Their bodies’ look like thin sacs filled with water – like water balloons. Its mouth is surrounded by tentacles and a curtain- like pharynx that hangs down inside the body and acts like a valve. This allows food to enter without water loss. When exposed to air they withdraw their tentacles, preventing them from drying out or being damaged.

Feeding They feed on small animals such as shrimps and fish, which they catch with the aid of the stinging cells in their tentacles. Many stinging cells (nematocysts) contain venomous liquid that subdues the prey. Some types of stinging cells are barbed and sticky, some actually wrap around the prey.

Predators They are eaten by some fish e.g. Butterfly fish and by some nudibranchs.

Did you know? Nemo and his dad Marlin – two clownfish- are exceptions to this, they live symbiotically with the giant anemone. The clownfish – also known as anemone fish - shelter amongst the tentacles of the sea anemone and are protected from the stings by a special coating of slime.


SOFT CORAL

Habitat Soft coral is abundant in sub-tidal zones with a wide depth range off both the west and East Coast.

Description They form colonies of polyps with eight feathery tentacles and are sometimes brilliantly coloured to warn of their stinging capabilities. No solid limestone skeleton.

Feeding Sunburst soft coral showing the individual polyps

They catch zooplankton (small microscopic animals) with the stinging cells in their tentacles.

Predators

Soft corals cannot be very nutritious because much of their bulk is made up of watery mesoglea (jelly) and their energy content is among the lowest of all animals.

SEA FANS (Gorgonians)

Habitat Sea fans occur in deeper water growing in caves, on rocky reefs and in crevices where they are protected from the force of waves. They are common around the Cape Peninsula and along the south Coast.

Description The branched tree-like, colony has a stiff central rod made up of a flexible material known as gorgonia. They are usually coloured white, pink, orange or red. Tiny cup-like polyps are visible on the branches when they are feeding.

Feeding The tentacles catch microscopic animals drifting in the water. They are predators.

Predators Free-living anemones.

Open polyps


HARD CORAL

Habitat Hard or stony corals grow best in clear, warm waters and their occurrence is limited to the depth to which light can penetrate the water for the algae that are found associated with the hard coral. Coral growth is seldom found deeper than 60 metres.

Description The polyps of corals produce a limestone skeleton, secreted by the outer layer of the body wall. A few hard corals occur around the Cape for example Noble and Cup coral. Hard corals function as the main builders of coral reefs. As hard corals lay down more of their underlying limestone or calcium carbonate skeleton the reef grows. They are also important in providing both food and shelter to a large number of reef organisms.

Feeding Colonial corals cannot always obtain enough food from the water and in order to survive they have great numbers of microscopic algae (zooxanthellae) in their body walls. The algae use sunlight to make food for themselves and their hosts by means of photosynthesis. Through digestion, coral polyps release these nutrients to the algae. Coral and algae then apparently cycle these nutrients between them, reducing nutrient loss to the water. The coral also protects the algae. This relationship is called mutualism as both these organisms benefit from this arrangement. CO2 + H2O Food (Carbohydrates) + O2 + H2O

Predators Some species of fish such as parrotfish and butterfly fish, as well as some sea snails and sea slugs, feed on corals.



Coral bleaching Coral reefs have recently been affected by bleaching i.e. the discoloration or loss of its symbiotic algae. The cause of these widespread bleaching incidents is uncertain but recent research indicates that the cause may be unusually warm waters. The optimum temperature for coral growth is between 26°C and 27°C. Temperatures above 29°C cause the stressed coral polyps to actively expel the algae giving the coral a bleached appearance. Bleached corals have difficulty recovering; a reef can take years to recover, and subsequent bleaching incidents may make it impossible. Without their symbiotic algae, corals are unable to deposit the calcium carbonate skeleton that makes up the foundation of a coral reef. Not only corals, but also all reef organisms could potentially lose their habitat because of bleaching incidents, as the calcium carbonate structure of the reef erodes away.

Did you know? The activity of the zooxanthellae also assists in the release of lime for the

construction of a coral skeleton. The biggest threat to corals, apart from humans who collect them and pollute the

sea, is coral bleaching.


JELLYFISH

Habitat Ocean drifters found mainly in the open ocean, but often wash ashore.

Description Jellies have rounded bell-shaped bodies (medusae), which contain a layer of jelly that consists of approximately 95% water. This layer varies in thickness in different jellies. They have tentacles at the open end of the bell that is armed with stinging cells. There is a square mouth with oral arms called the manubrium.

Feeding They feed on small fish, shrimps and plankton e.g. fish larvae.

Predators They have very few predators of their stinging tentacles. However, they are an important source of food for some species of turtle and the ocean sunfish. Plastic bags drifting in the ocean are often mistaken for jellyfish by these animals resulting in them eating it by mistake.

Did you know?

Some species are considered a delicacy in Japan.

That the box jellyfish can give a painful sting and that it’s Australian relative can kill a human being in 3 minutes.


HYDROIDS

Habitat Many of the tufts growing on rocks are hydroids and not seaweeds at all. Some hydroids are found growing on shells of snails. The hydroids protect the snail by deterring predators while the hydroids eat the scraps or waste products from the snail. This relationship is commensalism as the one organism benefits while the other organism is not harmed.

Description Hydroids form colonies, which often look like delicate trees or feathers. Other species of hydroids are branched in an orderly and elegant fashion. The tiny polyps are borne on the branches and may be housed in small cups. The polyps can extend for feeding and can retract into the cups after feeding. Some hydroids have an external sheath or perisarc made of chitin and protein. Divers avoid hydroids as they have a fairly powerful sting.

Feeding Hydroids are carnivorous and use their tentacles to catch minute shrimps, crabs, fish and eggs floating in the water. The digestive enzymes of hydroids are able to handle large prey.

Predators Predators are nudibranchs (sea slugs), flat worms and butterfly fish.

Did you know? Hydroids are named after Hydra, the multi-headed goddess of Greek mythology because they multiply by budding. The Goddess grew two heads in place of every one Hercules cut off.

Microscopic image of hydroid polyps

Polyps 2mm to hydroid colonies of 25cm


BLUEBOTTLES

Habitat Bluebottles live on the surface of the open ocean, but are often blown ashore by onshore winds.

Description They are unusual hydroid colonies, which consist of highly specialised individuals that are all interdependent.

Feeding They prey on small fishes that they catch with their tentacles.

Predators Marine turtles and sea swallows prey on bluebottles. Plough snails and sea slugs (nudibranchs) may eat bluebottles washed ashore.

Cnidarian Reproduction

Asexual reproduction can occur through fragmentation (polyp splits into two) or budding. For sexual reproduction, gametes are released from interstitial cells. Resulting ciliated Planula larvae swim or crawl to a favourable site. You have already seen that some classes (hydroids and jellies) have a complex multi-stage life cycle involving polyps and medusa.

Did you know? The painful stings of a bluebottle should be washed off with salt water and are best treated with sap from the leaf of a sour fig plant or vinegar. A medical practitioner using antihistamines should treat severe cases.

The smaller raft hydroid with a circular raft and the by-the-wind sailor with an oval raft and vertical sail are smaller colonies similar to the bluebottle. They set sail to the wind as a colony, producing a thin bright blue membrane of stiff material, orientated diagonally across the colony’s body.

Structure of the bluebottle or Portuguese man-o’-war



Quick review

1.

Identify the animals shown in the table below by giving the Phylum and the common name.

Phylum: ________________________ Common name:

Phylum: ______________________ Common name:

2. List three characteristics that all Cnidarians have in common.

3. Label the following parts on the animal below.

4. Name one interesting thing you would share with a visitor at the touch pool ________________________________________________________________________________

________________________________________________________________________________

a b


PHYLUM: PLATHYHELMINTHES

FLATWORMS

Habitat Flatworms can be found gliding over rocks in rock pools. One species lives under the foot of the ocular limpet. Parasitic species include flukes and tapeworms. Flatworms generally remain hidden under rocks.

Description Free-living marine forms are very flat leaf-like worms. They range in size from almost microscopic to 60 cm in length. Some are drab and others are very colourful. Flat worms are often mistaken for sea slugs.

Feeding They prey on anything that is small enough or slow enough for them to catch e.g. small molluscs, crustaceans. Some flat worms eat sponges and hydroids. They are able to swallow the stinging cells of the hydroids without triggering the sting capsule. They may also scavenge on dead animals. Reproduction Asexually- by fragmentation or budding; Sexual reproduction- Gametes formed in gonads. Most are hermaphroditic. Fertilisation is internal and eggs hatch as mini-adults or planktonic larvae.

Predators Fishes are the main predators of flatworms.

CHARACTERISTICS Free living (living independently i.e. not attached) Bilaterally symmetrical with a definite front and back, and with left and right sides. Mobile creeping animals. Concentration of sensory organs at the front of body = eye spots


Did you know?

Flat worms store food reserves in their cells and can go without food for long periods.

When starved they begin to digest their own tissues, starting with their reproductive organs.

The animal can shrink to a hundredth of its original size and still remain alive. When food is once again available, the worm grows bigger and regenerates the

missing organs.


PHYLUM: SIPUNCULIDA

PEANUT WORMS

Habitat Sandy areas between rocks and shells. The majority are bottom-dwellers in shallow water.

Description Peanut worms tend to have a dull appearance. They are light brown worms, which look remarkably like a peanut. The body consists of two main parts:

- a cylindrical, bottle-shaped or sac-like structure, the trunk; - a more slender extendable introvert which can be completely withdrawn into the trunk.

Feeding They feed on detritus (dead organic matter) that settles out under the rocks, algae and diatoms. The tentacles are used for gathering food.

Predators Fishes eat peanut worms.

Figure: (A) withdrawn and (B) extended view of a peanut worm.

CHARACTERISTICS Soft bodied. Worm-like. Unsegmented. They have an enormously extensible front part of the body (the introvert), which can

be shot out or rolled back into the body with equal ability.

Did you know?

The introvert is used for both feeding and locomotion. The introvert can be extended up to four times the length of the worm’s body.

A B


PHYLUM: ANNELIDA Annule = ring shaped markings- segmented

CLASS: POLYCHAETA

(poly = many; + chaetae = stiff hairs)

This class includes the bulk of the marine worms and are characterised by having many bristle-like stiff hairs called chaetae.

Two types of worms are described here - the active and free-living worms (e.g. the mussel worm) and the sedentary or tube dwelling worms (e.g. reef worms).

CHARACTERISTICS

Segmented worms.

Bilaterally symmetrical.

There is a distinct head formation (cephalization).

The heads have a variety of frills, jaws and feelers.

LONG, LONG AGO . . . . . . Six hundred million years ago, three kinds of animals appeared in the seas:

Segmented creatures; Shelled animals; And others with five rays.

They established four great groups of today’s animals:

Segmented Annelida and Arthropoda; Shelled Mollusca; And five rayed Echinodermata.


CHARACTERISTICS Active. Uniformly segmented bodies. A pair of large paddle-shaped appendages (parapodia)on each segment with long

bristles (called chaetae) Internal jaws. Well-developed sensory organs on head.

PHYLUM: ANNELIDA

CLASS: POLYCHAETA

1. FREE-LIVING WORMS

Habitat and description (structure)

Mussel worm Wonder worm Scale worm

Lives on rocks among mussels and seaweeds in the intertidal zone. Used as bait species but its collection destroys large areas of mussel beds.

Common under boulders, especially where gravel allows them to burrow. Large jaws inflict a painful bite Used as a bait species.

Common in rocky-shore pools, rock crevices and beneath boulders from low shore to the shallow sub tidal.

Feeding Shoot out their jaws to catch small animals such as shrimps and other small worms.

Predators They are eaten by fish and crabs or even by other species of polychaetes.


CHARACTERISTICS Normally inactive, tube dwelling, with small parapodia. Head often modified with elaborate appendages that extend into the water for filter

feeding. Lack (no) jaws.

2. SEDENTARY WORMS

Habitat and description (structure)

Tangle worm Spiral fan worm Reef worms

Lives in a mucous tube, which is decorated with sand or pieces of shell. Grooved tentacles extend to capture food particles that settle on them. They feed on detritus - detritivores

Abundant everywhere, dotting most rocks in the shallow subtidal pools, on shells or sea plants. Filterfeeders

Form extensive reefs on rocks at the mid-tide region, especially along the Atlantic coast. Cements sand grains to its tubes. Filterfeeders

Feeding Most of them are filter feeders. Others spread their long feeding tentacles over the sand or rock in a sticky web to catch small animals.

Predators Whelks and butterfly fish eat these sedentary worms.


Reproduction

Some asexual regeneration of segments or budding can occur.

Generally unisexual, with specialised sex organs or segments dedicated to gamete production.

Often have synchronised spawning. First released gametes produce a scent (gamone) stimulating other individuals to spawn. Swarming may also occur.

Eggs hatch as Trochophore larvae, which float as plankton before sinking to metamorphose into adults.

Quick Review

1.Provide the Phylum and common name of the animals illustrated in the table below.

Phylum: __________________________ Common name:

Phylum:

__________________________ Common name:

Phylum: __________________________ Common name:

Phylum:

__________________________ Common name:

2. List TWO interesting facts for each of the following three worms.

2.1 Flatworm

a.

b.

2.2 Wonder worm

a.

b.

2.3 Spiral fan worm

a.

b.

module 4 : marine invertebrates · 2 two oceans aquarium volunteer manual – module 4 –...

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