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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. 2. 3. 4. 5. Why is classification important? Name of Phylum and main characteristics. Methods of feeding Different kinds of symmetry and the advantages of each. 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 Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 1 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 2 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. Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES Phylum Class Order Family Genus Specie ANIMAL KINGDOM NON-LIVING WORLD 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 Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 3 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 Jellies Soft Corals and Sea Fans Hydroids PHYLUM: PLATYHELMINTHES Flat worms Bilateral symmetry Not segmented 4 PHYLUM: SIPUNCULIDA Bilateral symmetry Flatworms Bluebottles Not segmented Introvert and trunk Eye spots Peanut worm Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES PHYLUM: ANNELIDA Ring – like external bands - segmented Bilateral symmetry Bristle worms Jaws or modified mouth parts Free living worms Sedentary (live in tubes) 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 Isopods and Amphipods Hermit crabs True crabs Barnacles Shrimps, Lobsters, Prawns PHYLUM: MOLLUSCA Limpets Soft body Bilateral symmetry Most examples have a shell Bivalves Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 5 Chitons Sea snails Sea slugs or Nudibranchs Octopus Squid PHYLUM: BRYOZOA PHYLUM: CHORDATA Look like seaweeds, corals or hydroids Build colonies Include all Vertebrate classes All have similar features in larval stage = tadpole like Dorsal Nerve chord Stiff dorsal rod (notochord) Moss or lace animals Bilateral symmetry Pharyngeal gill slits Sea squirts Individual or colonial Cellulose casing = tunic PHYLUM: ECHINODERMATA Spiny skin Pentaradial (5 part ) symmetry Endoskeleton ( on the inside) Tubefeet Sea urchin Starfish Sea cucumber Brittle star Feather star 6 Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 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) Central point Fig 11. Showing radial symmetry of sea anemone Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 7 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 animals Radial symmetry Animals with a circular body plan Herbivore Animals without a backbone which eats other 2. In the table below number the names given from highest classification to lowest classification. Genus Class Order Phylum Family Species 3. Why is classification so important in the naming of animals? 8 Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES PHYLUM: PORIFERA (pori = pores and fera = bearer) SPONGES 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 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 animallike 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. Flagella beat to create water movement for feeding Living Shores: Figure 175 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. Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 9 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. 10 Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES PHYLUM: CNIDARIA (COELENTERATA) Cnida = nettle (stinging) 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. Living Shores: Figure 180 A Detail of the body wall of a cnidarian Living Shores: Figure 180 B Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 11 PHYLUM CNIDARIA CLASS ORDER HYDROZOA HYDROIDA SIPHONOPHORA Hydroids Bluebottles Polyps solitary or bud to form colonies 12 Floating colonies of several polyplike or jelly-like individuals that are attached to a stem or disc. Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES SCYPHOZOA ANTHOZOA Jellyfish or jellies Sea anemones, zoanthids, sea fans, soft coral, hard coral 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. 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 curtainlike 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. Clownfish living amongst the tentacles of a sea anemone Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 13 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 14 Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 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. Living Shores: Figure 198 Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 15 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. 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. 16 Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 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. Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 17 18 Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES HYDROIDS Polyps 2mm to hydroid colonies of 25cm 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. Microscopic image of hydroid polyps 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 multiheaded goddess of Greek mythology because they multiply by budding. The Goddess grew two heads in place of every one Hercules cut off. Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 19 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. Structure of the bluebottle or Portuguese man-o’-war Living Shores: Figure 186 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. 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. 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. 20 Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES Quick review 1. Identify the animals shown in the table below by giving the Phylum and the common name. Phylum: Phylum: ________________________ Common name: ______________________ Common name: 2. List three characteristics that all Cnidarians have in common. 3. Label the following parts on the animal below. b a 4. Name one interesting thing you would share with a visitor at the touch pool ________________________________________________________________________________ ________________________________________________________________________________ Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 21 PHYLUM: PLATHYHELMINTHES 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 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. 22 Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 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. Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 23 PHYLUM: SIPUNCULIDA PEANUT WORMS 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. 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. A B Figure: (A) withdrawn and (B) extended view of a peanut worm. Did you know? 24 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. Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 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. PHYLUM: ANNELIDA Annule = ring shaped markings- segmented CHARACTERISTICS Segmented worms. Bilaterally symmetrical. There is a distinct head formation (cephalization). The heads have a variety of frills, jaws and feelers. 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). Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 25 PHYLUM: ANNELIDA CLASS: POLYCHAETA 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. 1. FREE-LIVING WORMS Habitat and description (structure) Mussel 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. Wonder worm Common under boulders, especially where gravel allows them to burrow. Large jaws inflict a painful bite Used as a bait species. Scale worm 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. 26 Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 2. SEDENTARY WORMS 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. Habitat and description (structure) Tangle worm 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 Spiral fan worm Abundant everywhere, dotting most rocks in the shallow subtidal pools, on shells or sea plants. Filterfeeders Reef worms 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. Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES 27 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: Phylum: __________________________ Common name: Phylum: __________________________ Common name: __________________________ 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. 28 Two Oceans Aquarium Volunteer Manual – Module 4 – INVERTEBRATES