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Marine Invertebrates Chapter 7 Invertebrates- no backbones 97% of all animal species are invertebrate. Many are exclusively marine. All animals are: heterotrophs can reproduce sexually (many can reproduce asexually as well) motile at some point in their life cycle 2 Phylum porifera- the sponges Sponges do not have specialized tissues, but they do have specialized cells. Their body plan is asymmetrical. Adult sponges are sessile (attached to a surface). Because of their lack of tissues and organs, they can be separated through a strainer and reform new sponges. 3 Reforming of a sponge 4 Sponge Structure Ostia- numerous tiny pores that allow water to enter. Suspension feeders- sponges filter plankton and other food particles from seawater. Choanocytes- collar cells. Have flagella that trap the food and create a current. 5 Sponge Structure (cont’d) Osculum- opening where the water leaves the sponge. Spicules and spongin- either silica or calcareous that give the sponge support. Amebocytes- cells that move around and produce spicules. 6 Structure of a simple sponge 7 A complex sponge 8 Suspension vs. deposit feeding 9 Reproduction in sponges Asexual- Branches or buds break off and grow into new sponges- genetically identical. Sexual- reproduce by broadcast spawning of sperm. Eggs are usually protected in the sponge. Most sponges are hermaphrodites, but not all. Sponge larva is the only motile stage. 10 Sexual reproduction in sponges 11 Fire Sponge 12 Yellow Tube Sponge 13 Green Rope Sponge 14 Branching Tube Sponge 15 Azure Vase Sponge 16 Phylum Cnidaria- general info Radial Symmetry- several plains of symmetry. Oral surface- mouth side. Aboral surface- opposite side. Tentacles- slender extension used for capturing food. Nematocysts- stinging structures (inside cells of tentacles) Mesoglea- the ‘jelly’ that fills the body. 17 Body plans Polyp- tentacles on top, aboral surface attached to a substrate ex- sea anemone, coral Medusa- free swimming, tentacles on the bottom. Classic jellyfish plan. Many cnidarians have both body plans in their life cycle. 18 Radial symmetry and body plans in Cnidarians 19 Classes of Cnidarians Class Hydrozoa- often form colonies of polyps, which reproduce by making small medusas, or planula. Siphonophores- free swimming colonies that drift with the current. some have floats for buoyancy. Nematocysts produce very painful toxins Ex- Portuguese Man-of-war, fire corals (not true corals), Obelia sp. 20 Hydrozoans have both polyp and medusa stages in their life-cycles 21 22 Body plan of the Portuguese Man-of-war, a siphonophore 23 Portuguese Man-of-war 24 Portuguese Man-of-war on the beach 25 Portuguese Man-of-war swimming 26 Fire Coral 27 Classes of Cnidarians Class Scyphozoa- large medusae. Common jellyfish. Reproduce from a polyp which forms many tiny ephyra- grow into medusae. Class Cubozoans- the box jellies. The most lethal jellies in the world. They are a favorite food of many sea turtles. The sea wasp can cause heart failure in humans within minutes. 28 Jellyfish- Class Scyphozoa 29 Class Scyphozoa 30 Class Scyphozoa 31 Class Scyphozoa 32 Sea Wasp- Class Cubozoa 33 Class Cubozoa- Box Jelly 34 Classes of Cnidarians- (cont’d) Class Anthozoa- polyps that can be solitary or in colonies. No medusa stage (most have a larva called a planula) most diverse group of cnidarians. ex- sea anemones, corals Corals secrete calcium carbonate skeletons. 35 Octocoral 36 Sea Anemone 37 Giant Sea Anemone 38 Biology of Cnidarians Organization- tissue level- no organs. Feeding and digestion- carnivores; use nematocysts to sting and capture prey. . Behavior- no brain. Have a nerve net that transmits impulses. Some have primitive photoreceptors (‘eyes’). Respiration/circulation- all by diffusion through the body surface. No circulatory system. 39 Corals and Symbiosis Zooxanthellae- dinoflagellates that live inside coral polyps. Provide nutrients for the coral. Coral Bleaching- occurs when temperatures are too warm. Zooxanthellae die, eventually killing the coral. 40 Coral Bleaching 41 Phylum Ctenophora- Comb jellies Exclusively marine- only ~100 species. Have ciliary combs that allow it to move. The combs often reflect light in a prism effect. They are mostly pelagic, found in warm and cold water. Radial symmetry Feed with sticky colloblast cells. 42 www.imagequest3d.com 43 44 Phylum Mollusca There are more species of Molluscs in the ocean than any other animal group. Most have a soft body enclosed in a calcareous shell. The body is covered by the mantle- a thin layer of tissue that secretes the shell. A large muscular foot for locomotion. Some have a radula- a row of small teeth that scrapes food off a surface. 45 Classes of molluscs Class Gastropoda- Snails, abalones, limpets and nudibranchs- approx 75,000 species. Have a coiled shell over a very large, creeping foot. Use radula for scraping algae, but some are carnivores drill through the shells of other molluscs. 46 Figure 7.19 47 Tiger Cowrie 48 Gastropod egg case 49 Moon Snail- Class Gastropoda 50 Figure 7.20 51 Nudibranchs- sea slugs have bright coloration 52 Sea Slug 53 54 Class Bivalva- Clams, mussels, and oysters Characterized by their two sided shells. No radula, no head. Have very strong muscles for closing the shell. Filter feeders- use two siphons to draw a current of water through the gills. Gills- dual purpose; used for gas exchange as well as feeding. 55 Class bivalva Burrowers- clams use their muscular foot to bury themselves. Some attach to a substrate- mussels and oysters cement themselves rocks or another bivalve. Motile bivalves- scallops can swim by shooting water out of the mantle cavity and by clapping its shells. Pearl formation- some oysters secrete calcium carbonate to coat an irritating particle in the shell. 56 Figure 7.22a 57 Figure 7.22c 58 Figure 7.22d 59 Giant Clam 60 Giant Clam 61 Class Cephalopoda- ‘Head-footed’ Molluscs Octopus, squid, and cuttlefish. Mostly all agile swimmers, complex nervous system. Muscular foot- modified into arms and tentacles. Large, complex eyes- an octopus can see complex images like we do! Most lack a shell- except the chambered nautilus and chiton. 62 Class Cephalopoda Cephalopods swim by forcing water out the mantle cavity. Octopuses- commonly bottom dwellerslargest is the Pacific Giant (30ft.) Good hunters- use beak-like jaws to bite prey. Use radula to scrape flesh, some secrete paralyzing toxins. Like many squid, they can secrete ink to distract predators. 63 Class Cephalopoda Squid-Elongated body and fins adapted for swimming. Reduced shell- a ‘pen’ made of chiton that is embedded in its body for support. Giant squid- can get 30-40 ft in length! Cuttlefish- have an internal shell Chambered Nautilus- external shell 64 Figure 7.24a 65 Figure 7.24b 66 Figure 7.24c 67 Chambered Nautilus 68 69 Carribean Octopus 70 Carribean Octopus 71 Blue Ringed Octpus 72 Pacific Giant (14ft) 73 Carribean Squid 74 First Photos of live Giant Squid 75 First photos of a live Giant Squid 76 Giant Squid 77 Giant Squid 78 Biology of Molluscs Symmetry- bilateral Major characterisitcs- muscular foot, radula, mantle (not found in all species) Feeding and digestion- radula, filter feeding (bivalves) and complete digestive tract. Habitat- some are benthos, some are pelagic (nekton) Respiratory system- gills Circulatory system- open in many molluscs, some have closed circulation. 79 Phylum Arthropoda Largest phylum of all animals- over a million identified species. 3 out of 4 animals on earth are arthropods. In marine environments, most of these are classified in the Subphylum Crustacea. Ex- barnacles, shrimp and lobsters 80 Basics of Arthropods Bilateral symmetry Segmented body- head, thorax, and abdomen (or a cephalothorax- head thorax combined) Exoskelton- non living external skeleton made of chitin. Molting- must molt to grow. 81 The molted exoskelton of Galapagos shore crab. 82 Subphylum Crustacea Most are marine. Specialized for life in the sea- most have gills and appendages adapted for swimming and other life functions. Chitinous exoskelton is reinforced by calcium carbonate. Have two pair of antennae. ~ 68,000 identified species. 83 Copepods- Very abundant in plankton. Use large antennae for swimming. 84 Barnaclesattach to a surface. They are filter feeders. Have feathery feeding appendages. Favorite species of Charles Darwin! 85 Amphipods- Small crustaceans that live in seaweeds. Beach hoppers live in beach debris. 86 Isopods- have a more flattened body. Pill bugs are the only common land species. Marine species include sea roaches (but they are not roaches). 87 Decapods- ten legged crustaceans Shrimp, lobsters and crabs. Largest group of crustaceans. Five pairs of legs- the first pair adapted with claws for feeding and defense. Many have swimmerets on the abdomen to help them swim. Head and thorax fused into a cephalothorax. Protected by a carapace. Distinct abdomen in many (except crabs) 88 89 True crabs Have a reduced abdomen. It is small and concealed under the body. Well developed carapace. Males- abdomen is pointed Females- u-shaped for carrying eggs. Most are scavengers. Some are terrestrial- returning to sea to lay eggs. 90 Coconut crab- adult and juvenile 91 A View of the abdomens of male and female crabs. 92 Stages of Crustacean development 93 94 Biology of Crustaceans Feeding and digestion- planktonic ones are filter feeders. Bottom dwellers have specialized parts for food handling. Circulation- open circulation. Respiration- most use gills. Nervous system- small, simple brain. 95 Other Marine Arthropods Class Merostomata- horseshoe crabs. 5 species alive today, very similar to species extinct for millions of years. Sea spiders- not really spiders- they feed on sea anemones. Class Insecta- extremely rare in the ocean. Most ‘marine’ species live in seaweed debris on the beach. 96 Phylum Echinodermata Pentamerous radial symmetry- 5 planes of symmetry as adults. Their larvae are bilaterally symmetrical. Endoskelton- have an internal skeleton consisting of calcareous plates covered by a thin ‘spiny skin’. No head- have an oral and aboral surface. 7000 identified species- all marine. 97 Water vascular system A series of water filled canals. Used for locomotion when connected to the tube feet. Also used for circulation of oxygen and nutrient transport. Connected to the outside by the madreporite, or sieve plate. 98 Class Asteroidea- sea stars Five arms radiate from a central disc Oral side- has mouth and tube feet the protrude from ambulacral grooves. Endoskeleton- interconnected calcium carbonate plates make the arms flexible. Sea stars are predators of bivalves, snails, barnacles and other slow moving animals. 99 Aboral side of a sea star 100 Oral side of a sea star 101 Internal view of a sea star 102 Class Crinoidea- Feather stars and sea lilies Suspension feeders- use extended, feathery arms to filter food from the water. Body plan- like an upside down brittle star. Arms are adapted into feathery feeders. Fossils date back to the Paleozoic era. 103 Class Crinoidea- Sea Lilies 104 Class Crinoidea- a Feather Star 105 Class Ophiuroidea- Brittle Stars Also have ‘star shaped’ body. Very long, flexible arms Round central disk, and rapid, snake-like movement. Use tube feet for feeding. Very diverse- over 2000 identified species. 106 Class Ophiuroidea- Brittle Stars 107 Class Echinoidea- sea urchins and sand dollars Endoskeleton forms round, shell like shape. Moveable spines aid in locomotion, with tube feet in between. Unique mouth structure- jaws and muscles called Aristotle’s Lantern for biting food. Sand dollars shortened spines and flat bodies for living in soft sand. 108 Class Echinoidea- Sea Urchin 109 Class Echinoidea- Sand Dollars 110 Class Holothuroidea- sea cucumbers Look almost worm-like. No spines- lack obvious radial symmetry. Five rows of tube feet on one side for locomotion. Have spicule-like bits of skeleton. Deposit feeders. Some secrete sticky toxins, others use evisceration to ward off predators. 111 Biology of Echinoderms Most are carnivorous- many evert part or all of their stomach to digest outside the body. Have a central nerve ring- and nerve net similar to cnidarians. Respiration and circulation- through body wall and water vascular system. Separate sexes- reproduce sexually. Regeneration- dividing central disk into two can result in two new individuals in sea stars, brittle stars and some sea cucumbers. 112 Figure 7.48b 113 Figure 7.49 114