Introduction to Animalia and Porifera

• Animals are multicellular, eukaryotic, lack cell walls, heterotrophic, motile (at some point), and most have muscles and nervous tissue. Animals are categorized by tissues, symmetry, body cavity, segmentation, cephalization, and vertebral column presence

Sponges

• Sponges are sessile, lack symmetry and tissues, are suspension feeders, and vary in shapes, sizes, and colors
• Water enters through tiny pores (ostia), goes through water canals, exits through a large opening (osculum)
• Choanocytes (collar cells) create water current
• Pinacocytes form an outer covering
• Amoeba-like cells present
• Spicules (CaCO3 or SiO4) support sponges
• Asconoid sponges have a simple tubular body form, found in clusters
• Leuconoid sponges have a high degree of folding with choanocyte-lined chambers, most common
• Sponges capture small food using flagella-generated currents through ostia and osculum
• Asexually reproduce via fragmentation or budding
• Sexually reproduce via external fertilization with male and female gametes, being hermaphroditic
• Sponges compete for space with bryozoans and corals
• Sponges have symbiotic relationships (cyanobacteria) and predator-prey relationships (fish, mollusks, turtles)
• Nutrient cycling for Ca++ occurs

Cnidarians and Ctenophores

• Cnidarians include jellyfish, coral, anemone, and hydra
• Cnidarians have radial symmetry and a gelatinous layer
• Cnidarians possess a gastrovascular cavity surrounded by tentacles, and two tissue types
• Nematocysts are the most common cnidae, being a stinging organelle
• Cnidocil triggers nematocyst discharge upon touch, most common on tentacles
• Medusa (free-floating) is what people think of when they think of jellyfish, polyp (benthic) like coral
• Some Cnidarians exhibit both stages (like coral and anemone)
• Mesoglea forms most of the animal's body and is BETWEEN cell layers, is gelatinous
• Hydrozoans include hydroids and siphonophores (Portuguese Man of War)
• Most Hydrozoans are colonial with 2 polyps (reproductive and feeding)
• Hydrozoan Medusa is small and continuously swims up
• Scphozoans are jellyfish with both life stages, medusa-dominant
• Scphozoans swim vertically and horizontally
• Anthozoans (only polyp stage) include coral, anemones, and sea fans, which are colonial or solitary
• Coral has a polyp form skeleton
• Cnidarians feed via gastrovascular cavity, digesting prey
• Capture prey through the mouth into the gastrovascular cavity
• Hydrozoans and anthozoans filter feed, some are carnivorous, and paralyze prey with toxin
• Cnidarians reproduce asexually in the polyp stage by budding medusa-like buds released into water
• Cnidarians reproduce sexually in the medusa stage, releasing gametes for fertilization, leading to larval development to adult
• Cnidarians feed on many animals but are not often preyed upon
• Coral provides habitat important for marine environments
• Coral has symbiotic relationships with zooxanthellae and anemones with clownfish and shrimp
• Ctenophores have over 100 planktonic species with radial symmetry, gelatinous bodies and bioluminescence
• Ctenophores have mouth and anal pores, rows of fused cilia for locomotion, long sticky tentacles for food (copepods, fish eggs, larvae)

Ribbon, Round Worms and Lophophorates

• Ribbon worms have bilateral symmetry
• Ribbon worms are the earliest animals with advanced completed digestive, circulatory, and bilateral nervous systems
• Ribbon worms are successful predators with a proboscis to stab prey and inject toxin
• Acoelomates lack a body cavity (ex: flatworms/ribbon worms)
• Pseudocoelomates have a fluid-filled cavity but are not fully lined with mesoderm (false body cavity)
• Coelomates have a true coelom fully lined with mesoderm (ex: Mollusks, Echinoderms, and Chordates)
• Roundworms have a false body cavity (pseudocoelom)
• They are the earliest animal with organs and a complete digestive tract
• They inhabit bottom sediment/estuaries and are very abundant (millions)
• Feeding modes include predators, parasites, and scavengers
• Lophophorates are the earliest animals to have a true body cavity
• Lophophore: ring of tentacles around a tubular mouth
• Lophophorates are filter feeders, food for mollusks and crustaceans, impacted by humans
• Bryozoans are in the phylum of lophophorates and have a true body cavity
• Bryozoans are shallow, benthic, extremely abundant, forming large colonies in shallow waters (rocks, mangroves, algae, ship bottoms)
• Brachiopods are benthic, shallow, and found rocky to muddy substrates
• Brachiopods have a CaCO3 shell with two halves and resemble clams
• Most Brachiopods have a stalk (pedicle) to attach to substrate/bury in sand and feed on detritus/algae

Mollusks

• Mollusks are one of the largest and most successful group of animals with a true body cavity
• Mollusks have an unsegmented worm-like body and a soft body, often covered with a calcium carbonate shell
• Mollusks have internal fertilization and platonic larval stages
• Important features include: body cavity, muscular foot, visceral mass, radula (many have but not all), shell (many have but not all, it is formed from the mantle)
• Radula is a toothed organ that most mollusks use (minus bivalves) that is used as a drill (gastropods) or scraper for feeding
• The five common classes are: Chitons, Gastropods, Bivalves, Cephalopods, Scaphopoda (tusk shells)
• Chitons are marine molluscs that vary in size of the class polyplacophora, have a flattened body covered with 8 plates
• Chitons are found attached tightly to rocks in the intertidal zone and feed on said algae
• Gastropod mollusks are named the "stomach foot" and consist of snails, sea slugs, limpets, and abalone
• They are mostly benthic, many have shells and when alarmed withdraw into shell with an operculum covering
• Low broad shells are for clinging to waves (abalone and limpets)
• Nudibranchs DO NOT have shells, are called "naked gills" and are brightly colored, and have cerata to increase gas exchange
• Many nudibranchs are poisonous or distasteful to other organisms
• Detecting chemical cues from prey 100ft away, cone snails use a harpoon shaped radula coated with a toxin to hunt
• Mollusks feed on other gastropods, bivalves, starfish, algae, and cnidarians
• Trochophore larvae are primitive mollusks that release eggs directly into the water and are MOST COMMON!
• Villager larvae are free-swimming and can disperse long distances
• Tusk shells are a shovel-footed small class of shelled marine mollusks that have a tusk near the animal's foot that resembles a boat hull ("boat foot")
• Bivalve mollusks have two shells (mussels, clams, oysters, scallops) and a hinged, two-piece hall
• They have no radula or head, and the adductor muscle holds the shell closed
• They open and close for oxygen and food with external fertilization
• Cephalopod mollusks = “head foot” (squid, octopus, cuttlefish, nautilus) with advanced structure, locomotion, circulatory and sensory systems, and reproductively
• Cephalopods consist of nautiloids and coleoids
• Nautiloids have large coiled shells and gas-filled chambers in the rigid shell
• Nautiloids have 60-90 tentacles covered in a sticky substance
• Coleoids (squid, octopus, cuttlefish) have 8-10 arms, produce ink, swim with jet propulsion, and have the most advanced sensory systems of any invertebrates
• Cephalopods reproduce through internal fertilization where males deliver sperm to the mantle cavity via a modified arm
• Cephalopods have no larval stages, depositing eggs into substrate with parental care and courtship behaviors
• Cephalopods are more advanced because their foot is modified into a head-like structure with tentacles for prey capture, defense, reproduction, and locomotion
• They use arms or jet propulsion with a siphon for locomotion
• Three hearts and a closed circulatory system makes up circulatory system - high level of activity
• They are advanced with large eyes, and intelligent brains
• Mollusks are food for other animals
• They lead to competition in community structure shoreline habitats, and have extensive predator-prey relationships
• Snails have parasitic relationships, are calcium for marine birds

Annelids

• Annelids (segmented worms) have segmented bodies (internally and externally), many bristles (setae), and a hydrostatic skeleton
• Polychaete worms are the most common annelids which consists of marine invertebrate fauna, (40-80% of soft bottom) that can be free-moving or sessile
• Polychaete worms vary with feeding habits, some have jaws and teeth, active predators, and others are deposit feeders
• Reproduction also varies between asexual (budding) and sexual reproduction (swarming)
• The major ecological roles of annelids include nutrient cycling (burrowing worms bring nutrients from sediment to surface)
• They help marine food chain by being food for other animals and engage in symbiosis and symbiotic relationships with other marine organisms

Arthropods

• Common marine anthropods include: Crustaceans (crabs, lobsters, etc.) and chelicerata (horseshoe crabs and sea spiders)
• Chelicerata = horseshoe crabs and sea spiders are not true crabs, have 2 body sections, and no antenna
• Major groups of marine crustaceans include decapod crustaceans, mantis shrimp, krill, amphipods, copepods, and barnacles
• Decapods are crustaceans with 5 pairs of legs (crabs, lobster, shrimp)
• Crustaceans reproduce sexually, the female stores eggs in brood chambers or modified appendages, where the eggs will eventually be ready to hatch
• Mantis Shrimp: Stomatopods, specialized predators, smash prey with appendage and lives in burrows, under rocks, and crevices
• Krill: euphausids, bioluminescent, filter feeders, form swarms, main diet of a lot of marine organisms
• Amphipods: sand fleas, shrimp-like, 3 pairs of appendages used for jumping, swimming, and burrowing, common in wet sands
• Copepods: largest group of small crustaceans, zooplankton, creates swarms, food for many marine organisms, vertically migrate
• Barnacles: only sessile crustacean, attach to pretty much any surface, shell of calcium carbonate, filter feed with feathery appendages, hermaphroditic
• Echinoderms eat phytoplankton and are a food sources for marine organisms and humans
• Barnacles create competition and community structure, and cause fouling. Some crustaceans have symbiotic relationships, algae and grasses also contribute, nutrient cycle to food webs

Echinoderms

• Echinoderms have radial symmetry and spiny skin, deuterostome body cavity development, are mostly benthic, and live in a wide range of depths
• Echinoderms endoskeleton is below the epidermis
• Echinoderms have plates of calcium carbonate with outward projecting spines, and they have a water vascular system
• A water vascular system filled tubes inside the body, and a hollow sac structure on the end, used for locomotion and catching prey
• Sea stars are carnivores with 5-10 arms, can wrap around shells of bivalves, pry shells open, and insert stomach to digest prey
• They can reproduce asexually but most reproduce with external fertilization and have regenerative abilities
• Brittle stars swim with 5 arms, are carnivorous, have the largest # of species, wide depth range, mostly burrow into substrate, and have tube feet but no suckers
• Sea urchins and relatives have hard exoskeletons with many spines, includes heart urchins and sand dollars, herbivores, and long spines used for protection and movment
• Sea urchins use an Aristotle's Lantern to eat
• Sea cucumbers have elongated bodies, leathery body wall, and modified tube feet around mouth
• Crinoids: sea lilies/feather stars resemble flowers, most primitive, filter feeders
• Echinoderms are not preyed on due to their endoskeleton, but they are major predators to many other marine invertebrates and control algae, coral, and other invertebrates

Invertebrate Chordates

• Hemichordates are acorn worms with invertibrate chordate characteristics, but have a different notochord from true chordates
• Hemichordates are sessile bottom dwellers and inhabit mud or sediment
• Hemichordates use proboscis for collecting food or digging
• Cephalochordates: lancelets, true chordates with slender eel-like bodies
• Cephalochordates are benthic found in shallow areas, head projects above sand, and they have a swimming larval stage
• Urochordates: tunicates, body covering similar to cellulose, true chordates with notochord, pharyngeal gill slits, post anal tail, and dorsal hollow nerve tube
• Urochordates are mostly sessile
• Sea Squirts are sessile, solitary, colonial with round/cylindrical bodies, squirt water from siphon (incurrent and excurrent siphons), filter feeders, inhabit tropical shallow bottoms
• Salps are free swimming, and have incurrent and excurrent siphons on opposite sides of body
• Larvaceans are free swimming and produce enclosures of mucus used in feeding, new ones are formed every few hours when clogged, and abundant when food is plentiful