Flowchart

Lower Invertebrates

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Sponges
General Characteristics
- Multi-cellular but has no tissue
- Asymmetric body plan
- Sessile
- Habitat: marine
- Protect themselves by producing toxins or releasing spicules
Nutrition
- Filter feeders; water moves through body and microscopic food particles are sifter through Choanocytes and Amoebocytes
Digestion
- Intracellular; takes place inside cells
Circulation
- Takes place through diffusion when water enters the body through an incurrent (brings fluid inward) pore
Respiration
- Diffusion allows to get oxygen to the cell membrane
Excretion
- Diffusion of wastes including ammonia and carbon dioxide and is released through an excurrent pore of osculum
Reproduction
- Sexual and asexual. Sexual = hermaphrodites. Produce gametes depending on water temperature or photoperiod. Asexual = budding, fragmentation or gemmules (dormant specialized sponge cell).
- https://www.youtube.com/watch?v=xj-C52c9qlI
- photoperiod = the relative amount of light and darkness in a 24 hour period

- Spicules = structures that support a sponge's body
- Spongin = a protein that makes up flexible spicules
- Porifera = Sponges
- Cnidaria = Anemone, Corals, Hydras, Jellyfish
- Ctenophora = comb jellies
-Plathelminthes = flat worms; flukes, tape worms, turbellarians
- Nemertea = ribbon worms
Body Plans
Phylums
Basic Structure
1) Ostia (ostium) = holes in the body of sponges through which water enters.
2) Spongocoel = a cavity in the body of a sponge.
3) Osculum = an opening through which a sponge expels water.
Specialized Cells
- Collar Cells / Choanocytes = circulate water and trap food
- Pinacocytes = outer covering / provide protection
- Amoebocytes = transport food and other materials
- Archaeocytes (not in the picture) = repair and regeneration, transport food and reproduction
Ecological Roles
- Competition = sponges produce toxins to protect themselves
- Predator-prey = bony fish, molluscs and the hawksbill sea turtle
- Symbiotic = mutualistc relationship with cyanobacteria, providing a home and receiving nutriion
- Nutrition cycling = recycles calcium
https://www.youtube.com/watch?v=m8a0oNsDEx8
General Characteristics
- Have stinging cells
- Cnidocyte = a stinging cell | "Cnidos" = stinging nettle
- radial symmetry
- Two forms: polyp and medusa
- Most are marine
Nematocyte
- a specialized cell in the tentacles of a jellyfish
- containing a barbed or venemous coiled thread that can be projected in self defense or to capture prey
Cnidocil
- a short or bristle-like structure that acts as a trigger for a Cnidocyte
Body Plan
- epidermis = outer layer
- mesoglea = jelly-like substance in between inner and outer layer
- gastrodermis = inner layer
- gastrovascular cavity = empty space where digestion takes place
Cnidarian Stings
1) Box jellyfish - Chironex fleckeri
2) Portugese man-o-war
3) Box jellyfish - Carukia barnesi (causes Irukandji Syndrome)
4) Sea anemone - Lebrunia danae (Caribbean)
5) Sea anemone - Doplenia armata (Australia)
6) Sea anemone - Alicia mirabilis (Europe)
Painful Stings
- immediate intense stinging, burning pain with redness & burning
- weakness
-nausea
- headaches
-spasms
-dizziness
Irukandji Syndrome Symptoms
- severe headaches
- back ache
- muscle pains
- chest and abdominal pain
- nausea and vomiting
- sweating
- anxiety
-hypertension
- tachycardia
- pulmonary edema
Box Jellyfish (Chironex fleckeri)
- cube shaped medusae
- stings are extremely painful and fatal to humans
- death can occur 3-20 minutes after stinging
- non lethal stings can be severe and slow to heal
Box Jellyfish (Carukia barnesi)
- small (2.5 cm or 1 in) and extremely venemous
- found near Australia
4). Scyphozoa
- "true" jellyfish - perfect circle
- most, except for one species, is marine (200 species)
-medusa dominant stage
- specialized sense organs called rhopalia (percieves light and gravity) with ocelli (simple eye) and statocyst (maintain balance)
3). Anthozoa
- Largest group
- Stay polyps their whole lives
- Solitary or colonial
- Ex: Sea anemones, coral
Soft Coral vs Hard Coral
Soft Coral
- tentacles in multiples of 8
- no limestone skeleton
- bleach when stressed
- resiliant
-also known as octocorals
- no trace after death
- ex: gorgonians, sea pens, sea fans and sea feathers
Hard Coral
- tentacles in multiples of 6
- create limestone skeleton
- the main reef builders
- both colonial and solitary
- bleach when stressed
- ex: feather coral
- skeleton remains after death
Jellyfish
Nutrition
- digest their prey in a central gastrovascular cavity
Ecological Roles
1) Predator-prey = small fish, molluscs, sea turtles
2) Habitat formation = forms coral reefs
3) Symbiotic relationships = commensalism: provide home to many organisms; mutualism - sea anemones and clownfish
Cnidarians
2). Cubozoa
- Medusa dominant & cuboid
- All marine
- Strong swimmers which prey primarily on fish
- Tentacles arise at four corners from blade-like pendolium
- Stings are dangerous and can be fatal to humans
1). Hydrozoa
- very small
- predatory animals
- some solitary and most colonial
- most living in salt water
- colonial forms contain two types of polyps:
1) Gastrozooid = feeding polyp
2) Gonangium = reproductive polyp
- ex: Obelia (exhibit both polyp and medusa), Portugese Man o' War (this colony can be extremely dangerous), Hydra (exhibit only polyp stage and reproduce with buds).
Ctenophores
Characteristics
- cteno = comb
- phora = to carry
- radial symmetry
- closely resembles jellyfish
- transparent bodies
- lack stinging cells
- marine
- ciliated bodies = used for locomotion
- planktonics
-size ranges from few mm to 1.5 meters
- 100-150 recognized species
Structure
- 8 rows of combs or plates called ctenes
- statocyst = bubble-like structure; helps maintain equilibrium
- at night are luminescent to attract prey or mate, or to frighten predators
Nutrition
- carnivores; feed on zooplankton, larva fish, fish eggs
- some capture prey with their tentacles
- colloblast = specialized adhesive cells found on the tentacles of some ctenophores and used to capture prey
Reproduction
- Hermaphrodites
- Both gametes are released directly into the water; external fertilization
- Larva: cydipped
Ecological Roles
1) Control zooplankton populations
2) Control fish populations
Flatworms
Characteristics
- flatten bodies
- bilateral symmetry
- cephalization (head)
- most do not have a complete digestive system because they can absorb digested material
- respiration, circulation, and excretion: diffusion
- ganglia = is like a brain - group of cells that control the nervous system
- has a head
Ecological Roles
1) Funnels nutrients to higher trophic levels
2) Parasitic flatworms regulate population sizes
3) Important predators and prey for high-level consumers
4) Create spaces for other animals
5) Important mutualistic and commensal symbiants
Turbellarians
free living
Flukes & Tapeworms
parasitic (needs host)
Characteristics
- free living
- meiofauna = small benthic invertebrates that live in both marine and fresh water environments
- eyespot = group of cells that can detect light
- movement = cilia and muscles
- hermaphrodite
- carnivorous
- asexual reproduction through fission
Characteristics
- parasitic flatworms
- they are internal parasites of molluscs and vertebrates
- complex life cycle with at least two holes
- asexual and sexual reproduction
- lack a digestive tract of their own
- they gain nutrients from their host
Ribbon Worms
Characteristics
- mostly benthic
- found coiled under stones, empty shells, sea weed
- resemble flat worms
- pale or bright colors
Nutrition
- carnivorous; feed on annelids and crustaceans
- have a proboscis = a tube-like structure used by ribbon worms to capture prey
Ecological Roles
1) predators of annelids and crustaceans
2) moves nutrients from deeper sediments to the surface and aerate bottom sediments
3) burrows can act as habitats for organisms after they've been abandoned
Lophophorates
- A group of organisms that have a lophophore = a U shpae structure bearing ciliated tentacles around the mouth
- Fuction = gas exchange, protection, feeding
- Sessile
- Lacks distinctive head
Phylum Phoronids
- "horseshoe worms"
- secrete a tube leathery protein or chiton that can be attatched to rocks or shells
- feed on plankton and detritus
- sexual reproduciton
- asexual reproduction through budding and transverse fission
- has planktonic larva stage
Phylum Bryozoa
- pelagic
- size: 0.5 mm
- live in shallow water
- form colonies
- colonies appear as white encrustations composed of thousands of zooids
Phylum Brachiopoda
- lamp shells
- mostly benthic
- shallow water
- 5 mm to 8 cm
- shells with two valves that resemble clam shells
- the two shells differ in shape and size (dorsal and ventral)