Phylum Cnidaria and Ctenophora

Symbiosis/mutualism of corals

- Corals are rainforests of the sea and covers < .5% of the earth's surface - Corals are home to 25% of all marine species - Corals created the most massive biogenic structure, the Great Barrier Reef along the NE Coast of Australia - Zooxanthellae a type of algae that (~10 microns) lives inside membrane-bound vacoules in gastrodermis of corals, they make up 50% of biomass *20-95% of carbon fixed by algae is released to the coral polyp (glycerol+glucose) *MUTUALISM: uptake of CO2 by algae drives a chemical reaction in salt water that increases the rate of CaCO3 production by the polyp *Corals respire CO2 + releasing nitrogen <ammonia>

Colonialism

Ability to form colonies via asexual reprod. Individuals can specialize and catch larger prey, compete for space

What is an acontium and where is it found?

Acontia is found in the gastric cavity, it is an extension of a nematocyst bearing-mesentery, used for defense/protrude from the mouth to capture prety

Planula Larvae

After external fertilization, a swimming planula is produced

What is a Millepora?

Aka fire coral it is a common inhabitant of reefs , an unusual hydrozoan bc of its calcified skeleton, *not a true coral

Is the number of tentacles on the slide of southern soft coral diagnostic of alcyonarians?

All have 8 (octo), all have 6 or multiples of 6 (hexa)

Cnidaria assumed drawbacks

All undigested food material passes out through the same opening through which the food enters the mouth, they must expel before ingesting food

Strobilation

Also known as transverse fission, asexual reproduction where transverse segmentation of the body occurs

Metagenesis

Alterations of generations of between sexual and asexual reproduction

Compare and contrast anthozoan vs. hydrozoan polyps

Anthozoan polyps: possess siphonoglyphs, acontia, polyp not protected, more complex structures Hydrozoan Polyp: polymorphic polyps (gastro, gono, dactyl- zooids), simpler structure but has perisarc that protects polyp

Ctenophores body plan

Bi-radial symmetry, nervous system in form of nerve net but more specialized than cnidarians

What are the 8 differences between Cnidarians and Ctenophores?

Cnidarian: - Adults are often dimorphic - Often colonial - Have muscle like cells (epidermis + gastrodermis) - swimming by muscle contractions and jet propulsion - Tentacles don't retract - Has cnide inside cnidocyte toxins - Gastrovascular cavity has one opening - Most medusa and all anthozoans are dioecious, separate sexes Ctenophores - Adult stage only has one form (medusa) - Never colonial - Has genuine smooth muscle cells (triploblastic?) - Ctenes that help ctenophora species swim - If they have tentacles they are retractable - Colloblast inside collocytes are adhesive - Has a complete digestive tract - Most are hermaphroditic

Ctenophora

Comb jellies, most are predators & planktonic, exclusively marine. Includes class tentaculata and nuda. Was once in the Phylum Coelenterata with Cnidarians.

Primary and Secondary Mesenterial Septae

Complete/ Incomplete sheets of tissue connecting the mesoglea surrounding the pharynx to the gastrodermis. Primary: structural support and increase SA for digestion Secondary: loaded w nematocysts

Subphylum Medusozoa (scyphozoa, cubozoa, hydrozoa )

Containing all cnidarians except sea anemones/corals/

Aboral sense organ

Coordinates movement with apical sense organ (swims mouth first)

Hermatypic

Corals in the order Scleractinia that build reefs by depositing hard calcareous material for their skeletons

Perisarc

Covering made up of polysaccharide, protein, chitin to protect the colony.

Class Cubozoa

Cube animals, each has 4 tentacles emerging from the 4 corners, unusually active and strong swimmers, restricted to tropical/subtropical areas (Australia), developed nervous system & complex eyes. *Differs from true jellyfish as the polyp stage does not strobilate.

Class Scyphozoa

Cup animals, true jelly fish, all marine species, dominant life stage is the medusa, swimming bell has thick mesoglea, life cycle has separate sexes e.g. lion's mane (2m diameter bell, 30m long tentacles)

Dactylozooids

Defensive polyp loaded with nematocysts or cnidae, no mouth

Gonozooids

Designed for reproduction, produce medusae asexually by budding. They are incapable of feeding and depend on others for nutrition.

Gonads

Develop in gastric pouches, surround the gastric pouches

Ephyra

Each individual polyp (genetically the same) created after strobilation and breaks off one by one

Epidermis

Ectoderm in embryo lines the outer surface, contractive (muscle) protective layer

Diploblastic

Endoderm + Ectoderm, not totipotent like sponges, it is a fixed form and function

Gastrodermis

Endoderm in embryo lines the gut in larva/juvenile and adults

Siphonoglyphs

Extends down the pharynx from the mouth, each groove is ciliated which helps move food + water down the pharynx

Gastrozooids

Feeding polyp that collect small animals w/ tentacles

Colloblasts

Feeding structures that are adhesive properties unlike nematocysts, adhesive cells = collocytes

Subphylum Anthozoa

Flower animals, exclusively marine, polypoid (simple life cycle), mitochondrial DNA is circular whereas other cnidarians are linear

How do gonozooids get nutrition in the absence of feeding tentacles?

Food caught by gastrozooid provides for the gonozooids as well

Pedal Disc

Foot of anthozoan

Acontia/Acontium

Found near the base of an anthozoan, thin filaments loaded with nematocysts. Can be defensive feature or feeding structure (shot out of small pores)

Radial Canals

From the gastric pouches, water circulates to the periphery of the bell and through a complex series of narrow canals

Pneumatophore

Gas filled floats (carbon monoxide), derives from basic medusoid architecture

Subclass Zoantharia

Hexacorallia: does not create CaCO3 skeleton, no protective surface, mostly solitary. Sceleractinia: true (hard & stony) corals, either reef building or not (hermatypic or ahermatypic)

Difference between hydra (freshwater) & most hydrozoans

Hydra: FW, solitary, polypoid stage only Most hydrozoans: SW, colonial, polyp + medusa stage, polymorphic

Ramet

Independent individual of a clone

Gastrovascular cavity

Internal space for extracellular digestion. *simple in polyps and complex in medusa (radial canals)

Mesoglea

Jelly-like material between epidermis and gastrodermis, mostly acellular in the extracellular matrix, made up of protein (8%), polysaccharides (1%), rest is h2o. *If thick = skeleton

Gastric Pouches

Jellyfish generally have 4, they are radial divisions of the stomach and help to increase surface area

Limitations of corals

Light- hermatypic corals must be in shallow waters aka margins of continents and islands. - Sediments/algal blooms block light. - Rivers bring sediment which can clog polyps. - Temperature: cold water reduces CaCO3, reef builders need warm water between 20 degrees to 30 degrees N&S of equator - Deepwater trawling <equivalent of clear cutting a forest but in an ocean>

Ctenes

Long cilia in bands (3.5mm long), helps ctenophores to swim, typically eight rows and controlled by apical sense organs

Cnidaria

Means stinging thread, 11,000 species including sea anemones, jellyfish, corals, box jellies, Portuguese man-of-war Diploblastic body plan, lack cephalization.

What is the difference between metagenesis and polymorphism?

Metagenesis is where one generation of organisms found in the same animal (from polyp to medusa) life cycle Polymorphism is where two or more forms exist in the same species within the same population (could involve polyp and medusa, can also be different polyps zooids)

Nematocysts

Most common type of cnidae, aka thread bag

Manubrium

Muscular cylinder that encloses oral arms, the mouth of jellyfish is also found at the end of the manubrium

Oral Arms

Muscular tube, thick neck (located under the cup of the jelly fish, tentacles surround it)

Why are there no hermatypic corals in New England waters?

New England waters are too cold for reef building

Subclass Alcyonaria

Octocorallia: sea fans, soft corals, sea pansies. Known as colonies, most don't produce CaCO3 skeletons, loaded w spicules

Scyphistoma

Polyp that settles at the bottom

Nerve net

Primitive nervous system that they possess

Polymorphism

Referring to 2 generations each with a different adult form, e.g. polyp and medusa

Polyp

Reproduces asexually, usually benthic and rooted, mesoglea is thin

Medusa

Reproduces sexually & planktonic, dispersive form, mesoglea is thick

Rhopalia

Sensory organs that contain statocysts (balance organs), ocellus (light sensing organs), sensory lappets (touch receptors) *To orient themselves while they swim

Cnidae

Stinging/Adhesive structures on the tentacles, captures food, defensive, compete for space. Capsules inside cells are called cnidocytes. Can uncoil as fast as a bullet out of a rifle

Which phase dominates in this class?

The medusa stage

How is Hydra atypical of most hydroids?

They are found in freshwater, solitary and only has the polypoid stage

How do colloblasts operate to capture prey?

They have adhesive cells called collocytes that help capture prey

Oral Disc

Top base of a polyp

Pharynx

Tube in the middle of the polyp that captures food

Class Hydrozoa

Water animals, 3,000 species, only group with freshwater species but most are marine, more delicate, less mesoglea (no cells found), nematocysts restricted to epidermis

How does the septate gastrovascular cavity in anthozoan polyps affect the efficiency of digestion, structural support, and polyp size relative to hydrozoan polyps?

hydrozoan polyps smaller, less efficient in digestion as they don't have those structures in their gastrovascular cavity

Compare and contrast morphology of hydrozoan and scyphozoan medusae

hydrozoan; thinner mesoglea scyphozoan: more complex, has oral arms that surround manubrium, thicker mesoglea