Jellyfish, hydra, sea anemones, and corals {coelenterate}| {cnidaria} are Ecdysozoa protostomes, live in ocean, and have radial symmetry.
digestion
They have mouths with tentacles that push food into mouth. Chemicals digest food in sacs, and then pseudopods from endoderm make food vacuoles.
tissues
Tissues are epithelial, connective, muscular, nervous, and reproductive.
senses
Hydra and jellyfish can sense mechanical, thermal, and chemical stimuli.
nervous system
Coelenterates were first animals to have neurons, synapses, and nerve nets, as well as specialized sense organs, but coelenterates have no organized interneurons or ganglia.
Both neural and non-neural cells transfer electrical signals by electrotonic coupling, with no chemical synapses.
In hydra, mechanical stimulation releases acetylcholine, epinephrine, norepinephrine, serotonin, and histamine transmitters from neurons, which discharge nematocysts.
classes
Classes are watery hydroids or hydra (Hydrozoa), flowery anemones and corals (Anthozoa), and bowl-shaped jellies (Scyphozoa). Corals and anemones are polyploid and stationary. Bases are downward, and tentacles and mouth are upward. Jellyfish are medusoids, swimming with tentacles and mouth downward.
colonies
Portuguese man-o'-wars bud on top of each other to make colonies.
Coelenterates have stinging cells {cnidocyte}, whose tips contain one nematocyst.
Cnidocyte tips contain one coiled stinger filament {nematocyst}, which can have poison, uncoil through cnidarian skin to puncture small animals, and entwine prey before digestion.
Coelenterates have one hollow sac with gelatin matrix {mesoglea} between endoderm and ectoderm.
Bacteria {zooanthellae} live in polyps and make oxygen used to make carbonates.
Anemones {sea anemone} {anemone, coral} {coral} use vertical partitions in hollow sac to make chambers to increase digestive surface, have gullet between mouth and hollow sac, and secrete carbonates. Anemones have one stalk with top stinging-tentacle ring. Corals make reefs. Living parts are on top, and sand and dead algae and coral are below.
Reef coral can look like brain cortex {brain coral} (Meandrina).
Coral colonies can have horny flexible branching axial skeletons {gorgonian} (Gorgonacea). Sea whips are gorgonians with long single stems. Sea fans have fan-shaped or tree-shaped skeletons.
Class Hydrozoaregenerate {hydra}| (order Siphonophora) attach to substrates by epidermal-cell discs at opposite end from mouth, and are one centimeter long. They have asexual budding. In stagnant water, high carbon dioxide causes mating types. Hydra have nerve nets. Nervous system governs tissue patterns and regeneration. Hydra polypeptide also is in bovine and human hypothalamus.
Blue hydra {Portuguese man-o'-war} float and have tentacles.
Scyphozoa {jellyfish}| have tentacles that move body through water and have thick mesoglea. Largest jellyfish is Cyanea, with 30-meter tentacles and four-meter diameter. Jellyfish have a statocyte with granules on hair cells. Marginal ganglia supply jellyfish rhythmic beats.
Jellyfish can have diploid sexual polyps and then have diploid asexual forms {medusa}|.
Jellyfish can have diploid sexual forms {polyp, jellyfish}| and then have diploid asexual medusa.
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Date Modified: 2022.0225