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Chapter 7 Marine Animals sans Backbone
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Where are we in geologic time?
As a class, we’ve moved from bacteria to plankton, and through some algae (seaweed). Now we’ll examine primitive animals without vertebrae.
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How are we related??
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Introduction Most (97%) of the amazing life located within the oceans (or anywhere else, for that matter) doesn’t have a backbone. Animals without backbones are called invertebrates (without vertebrae). In every class of invertebrate we can find a marine example.
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1. Sponges Sponges are really nothing but a loose aggregation of specialized cells. Of the 6,000 known spp. nearly all are marine. Amazingly enough, these cells don’t actually form organs, but do serve similar functions, keeping the animal(s) alive.
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Porifera-Sponges (the pore bearers)
Spicules are like calcium carbonate or silica re-bar for sponges, providing support for a larger congregation.
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Sponges Do they “sits and thinks, or do they just sits??”
Sponges are sessile and remain permanently attached to the substrate they alight upon.
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if you carve ‘em up, they come back!!
It’s more amazing than that. If you mix groups of sponges together, they will usually reorganize into their original groups. if you carve ‘em up, they come back!!
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Suspension feeding: natural water purification
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Reproduction: Asexual vs. sexual
Damage to a sponge can actually promote asexual reproduction, as “parts” can land elsewhere and form new sponges.
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Sexual reproduction Many sponges are hermaphrodites, containing male and female reproductive capabilities. They do not self-fertilize. Tube sponges, such as this Verongia Archeri which is common in Caribbean waters use broadcast spawning to disperse sperm and eggs in a flurry of activity that is often coordinated with lunar cycles.
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General Sponge Types Sponges fall into several basic categories, mostly depending on shape: branching tubular round encrusting glass boring (destructive) Hawaiian encrusting sponge Sclerosponge (CaCO3) Ceratoporella nicholsoni
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Sea anemones, jellyfishes, coral, etc.
2. Cnidarians Sea anemones, jellyfishes, coral, etc.
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Cnidarians Cnidarians actually exhibit radial symmetry in which similar body parts can be grouped around a central axis. Here we also observe a large jump on the evolutionary scale: tissues that perform specific functions.
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General Cnidarian Structure and Function
Macrorhynchia phillipina General Cnidarian Structure and Function Centrally located mouth Oral surface (mouth) Aboral surface (“mouth side” vs.“aboral side”) Tentacles Gut Nematocysts Polyp and Medusa: reproductive stages Beautiful, but deadly! This colonial hydrozoan still contains cnidae.
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Discharged nematocysts( stinging cells) used for defense
and prey capture, have been the plague of more than fish. Stings from certain jellyfish have resulted in death in a matter of hours, especially for infants.
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Carukia Barnesi: the bad-est of the bad!
A sting from this little guy can cause Irukandji Syndrome: “It begins with a mild sting, followed by severe lower back pain, muscle cramps in arms, legs, stomach and chest. It causes sweating, anxiety, nausea, vomiting, headaches and palpitations, and has also been known to cause cardiac failure.”
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Shapes 1. Polyp: a sac-like attached stage with a mouth and tentacles (mostly sessile) 2. Medusa: a mobile bell-like upside down polyp (jellyfish).
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Types of Cnidaria Cnidaria come in all shapes and sizes:
Hydrozoans- feathery hydroids Siphonophores- man-o-war Scyphozoans- large jellyfish Anthozoan-sea anemones and coral Almost all Cnidaria are carnivores. Sea fan
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Similar to cnidarians in most respects.
3. Ctenophores Similar to cnidarians in most respects. Nearly 100 spp. contain ciliary combs which assist in prey capture and mobility.
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Ctenophora vs. Cnidaria
Characteristic Cleavage Nematocysts Sexuality Ciliation CTENOPHORE Determinate Usually None Typically Hermaphroditic Multiciliated Cells CNIDARIA Indeterminate Typically Single-Sex Monociliated Cells
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4. Marine Worms, etc. Marine worms, and organisms hereafter, kick it up a notch, evolutionarily, exhibiting bilateral symmetry (just like humans). They have anterior, posterior, dorsal, and ventral sections. Bilateral symmetry, and all that goes with it, results in enhanced motion and sophisticated behaviors.
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Flatworms: Platyhelminthes
These simple organisms contain organs and systems. Nearly 20,000 spp. exist The most common are turbellarians, like this Pseudoiceros gratus from the Great Barrier Reef (lower right.) About 6,000 spp. are parasitic, like flukes (trematodes) and tapeworms (cestodes)
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Ribbon worms look like tapeworms, however they exhibit a complete digestive tract and a circulatory system. ~900 spp. exist
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Nematode Roundworm numbers are staggering in the marine world.
Many animals have them. Some even find their way into fish (which we ingest when we eat sashimi).
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Segmented Worms 20,000 spp. known as Annelids
First example of segmentation. Allows for flexibility and excellent burrowing ability.
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Polycheates-many bristles (setae) ~10,000 spp. Exhibit parapodia
Evolution of gills!!! Fireworm Hermodice carunculata
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Sandworm Nereis
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This feather-duster worm, Sabella melanostigma, is a perfect example of beauty, form, and function.
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Soft Bodied Marine Organisms
5. Molluscs Soft Bodied Marine Organisms
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Molluscan Variety Molluscs (mollusks) include snails, octopuses, clams, etc. Nearly 200,000 spp. exists. Many of them are eaten as food. Most have a common body design (or variations of it) CaCO3 shell, mantle (tissue), foot (locomotion), and a radula (rasping teeth) .
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Essentially, a mollusc is a coiled mass of vital organs wrapped
in a dorsal shell.
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Gastropods (Gastropoda), or stomach foot,
are the most common molluscs. Snails, abalone, and nudibranchs. 75,000 spp. red abalone Haliotis rufescens giant keyhole limpet Megathrua crenulata Cooper’s nutmeg snail Cancellaria cooperi nudibranch, Phidiana crassicornis Cone snail, Conus geographus
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Bivavles
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Clam or Mussel? In general, clams burrow and mussels don’t.
Clams burrow (foot) for protection and feeding- filter feeding (incurrent siphons). Mussels and oysters attach to whatever they can find, often causing destruction of bridge and pier pylons.
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Scallops also filter feed. Many have striking color patterns.
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Pearls Natural pearls are still found.
Occurs when irritating particles are lodged within the mantle cavity and covered by secretions (CaCO3) from oyster. Many other pearls are cultured (seeded).
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“Putting Your Head and Feet Together”
Cephalopods “Putting Your Head and Feet Together”
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Cephalopod (General Morphology)
While still following the basic body plan of a mollusc, octopuses, cuttlefish, squid, etc. are highly specialized.
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Cephalopod All cephalopods (650 spp.) can be considered as predatory.
Some have venomous bites which can be extremely painful. Octopuses lack a true shell, while other “cephs” have internalized it (squid-pen).
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Some cephalopods like this Pacific giant octopus, Octopus joubini,
reach amazing proportions (>30 ft). Octopus, squid, and cuttlefsh use suckers to help capture prey items.
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7. Arthropods: Crustaceans Crabs, Lobster, Shrimp, Barnacles
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Arthropods exhibit bilateral symmetry and an chitinous exoskeleton
Arthropods exhibit bilateral symmetry and an chitinous exoskeleton. Crustaceans (68,000 spp.) To grow they must shed the exoskeleton and absorb water to grow before the new exoskeleton hardens.
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Barnacles
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Amphipods and Isopods Orchestoidea, a beach hopper
are often found on marine mammals. Sea louse: a marine pill bug
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Decopods: Ten legs never tasted sooo good!
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Other decapods
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Male vs. female When choosing a crab, females exhibit a “U” shaped
abdomen while males exhibit a “V” shape.
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Sea stars, brittle stars, urchins
8. Echinoderms Sea stars, brittle stars, urchins
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General Structure Echinoderms
Echinoderms are examples of animals with pentaradial symmetry (although not all are pentaradial). Unlike arthropods, they have an endoskeleton (internal). They also evert their stomach to eat.
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Nearly 7,000 spp. of sea stars exist.
Tube feet along ambulacral grooves assist the starfish in moving.
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Other Echinoderms Brittle star Ophiothrix oerstdii Sand dollar
Sea Urchin Strongylocentrotus drobachiensis Sand dollar Mellita sexiesperforata
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