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Invertebrates Sponges, Cnidarians, & Comb Jellies Ch. 7 Objecitves 1. Understand the most important morphological characters of the major groups of marine invertebrates (inverts). 2. Suspension vs. deposit feeding 3. Compare and contrast body structures between gastropods, bivalves, and cephalopods. 4. Compare and contrast body structures between sea stars and sea urchins ✓ ✓ ✓ ✓ ✓ ✓ Sponges • Structurally simplest multicellular animals • Cellular level of organization – No true tissues or organs • Amazing variety of shapes, sizes, colors, but simple body plan Sponges: simple body plan • Sessile: live permanently attached to bottom • Numerous pores (ostias)—allow water to enter • water filtered through collar cells, food ingested, water leaves through osculum Sponges: feeding • Suspension feeders: – Eating food particles suspended in water • Filter feeders: – Actively filter food particles Sponges feeding Sponge Sex: They do it all! • Hermaphrodites: – Male and female gonads • Asexual – Branches or buds break off, grow into identical sponge • Sexual – Broadcast spawning Cnidarians • Sea anemones, jellies, corals, and realatives • Tissues that perform specific functions – Huge evolutionary step! – Able to swim, respond to stimuli, engulf prey, and more. • Radial symmetry – Like a pizza-all slices similar Mexican Anemone Cnidarians: aboral vs. oral • Oral surface – Mouth located here • Aboral – Opposite side Nematocysts • Microscopic needles housed within a tiny cell • Both mechanical and chemical stimuli may trigger needles • Fire from housing and drill into victim • Needles contain a neurotoxin, designed to paralyze the prey. Nematocysts in action! Polyp vs. Medusa Cnidarians are usually one or the other---but sometimes spend time as both. Types of Cnidarians: Hydrozoans • Feathery or bushy colonies or tiny polyps • Interesting life cycle • Life cycle animation Types of Cnidarians: Siphonophores • Form drifting colonies of polyps • Some have specialized gas filled float • Portuguese manof-war • Up to 165 ft tentacles! • Deadly Types of Cnidarians: Cubozoa • Box jellies – a.k.a. sea wasps • Venom attacks heart, nervous system, and skin cells dead w/in minutes • One of the deadliest venoms on earth • Northern Australia, Southeast Asia, and the Indian Ocean Box Jellies Comb Jellies • a.k.a. ctenophores • Have 8 rows of ciliary combs – Refracts light, creates a prism-like multicolor effect • Carnivores
