Phylum Cnidaria
Classification Class Scyphozoa Jellyfish Class Anthozoa Sea Anemones & Corals Class Hydrozoa - Hydra
General Characteristics Stinging tentacles Arranged in ring around mouth Saclike digestive tract Radial symmetry Nerve net One part stimulated, all parts respond
Class Scyphozoa the jellies
Class Scyphozoa Medusa and polyp body forms
Body composed of epidermis, mesoglea, & gastrodermis Considered plankton Limited locomotion Contraction of muscular ring around medusa Gas exchange occurs by diffusion Sea Nettles Video Monterey Bay Aquarium
Feeding Tentacles covered in stinging cells called cnidoblasts Contain nematocysts Coiled threaded with barbs Discharged when mechanically and chemically triggered Most barbs contain paralyzing toxin Once discharged, cannot be reused Tentacles pull food to mouth Food enters gastrovascular cavity Enzymes secreted; extra and intracellular Waste expelled out mouth
Feeding (cont.) Sticky mucus on medusa also used to catch food Food sticks to surface Ciliated cells move it to the mouth Moon jelly The moon jelly has one of the weakest stings of any jellyfish. These jellies trap much of their food on the sticky mucus covering their bell, then transport it to their tentacle
sexual and asexual phases
7 ft. Lion's Mane jelly 120 ft. Not only the largest of all jellies but with tentacles that can reach over 100 feet, the lion's mane jelly is the longest animal on earth! Not all reach this size but even the small ones pack a powerful sting! Crystal jelly These seemingly harmless creatures can open their mouths wide enough to swallow jellies half their size. They light up when disturbed. People harvest them for the chemicals that make them glow.
Box Jelly (Sea Wasp) Found in shallow waters of N. Australia during summer months of Oct.- Aug. 5 to 25 cm across, with four groups of up to 15 tentacles. Venom from a single creature can kill up to 60 adults. Get stung by one and you have from 30 sec. to 4 min. to get help or die!
Class Anthozoa Sea Anemones & Adult polyp stage only Sessile (limited movement) Corals
Sea Anemone
Some symbiotic relationships--mutualism Sea anemone and clown fish Coral and algae
Life cycle Asexually Some split in half Regenerate base pieces Budding Sexually External fertilization in water Internal fertilization Sperm released out of males mouth Enters female and absorbed into ovary Larvae released into water by female
zooxanthalle algae
Class Hydrozoa Hydroids Intertidal and subtidal areas Some independent Some colonial - many polyps working together as a single organism Can also have medusa forms, although polyp form is dominant Some grow on and coat other ocean animals Hydractinia echinata Hydra oligactis Portuguese Man-of-War
Portuguese Man-of-War Hydroid colony Tentacles with stinging cells several meters Four different polyps make up organism The float (pneumatophore) is a single individual and supports the rest of the colony. The tentacles (dactylozooids) are polyps concerned with the detection and capture of food Digestive polyps (gastrozooids) break down the food. Reproduction is carried out by the gonozooids.
Portuguese Man-O-War are eaten by sea turtles (loggerheads and leatherbacks), and some fish have symbiotic relationships with the Man-O-War, living among the tentacles
Obelia Polyp colonies Dominant asexual polyp stage, but also has medusa stage
Phylum Ctenophora (sometimes confused with Jellyfish) Comb jellies 8 rows of fused cili (combs) for movement and feeding One species has nematocysts on tentacles Float near surface Bioluminescent
Sea Gooseberry When is a jelly not a jelly at all? When it is a comb jelly. Comb jellies are ctenophores, with rows of iridescent combs instead of stinging tentacles. Gooseberries also have two long tentacles for capturing prey. Comb Jelly