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In cnidarians, the gastrovascular system is also known as the coelenteron, and is commonly known as a "blind gut" or "blind sac", since food enters and waste exits through the same orifice. The radially symmetrical cnidarians have a sac-like body in two distinct layers, the epidermis and gastrodermis , with a jellylike layer called the mesoglea ...
The eyes are situated on rhopalia (small sensory structures) which serve sensory functions of the box jellyfish and arise from the cavities of the exumbrella (the surface of the body) on the side of the bells of the jellyfish. [41] The two large eyes are located on the mid-line of the club and are considered complex because they contain lenses.
Jellyfish reproduce sexually. Males release sperm through their mouth into the water column and this is received into the female's mouth, where fertilization occurs. Development occurs quickly, as the lifespan of a jellyfish is only a few months. The eggs develop either inside the female, or in brood pouches located on the oral arms.
Pacific sea nettles, Chrysaora fuscescens. Cnidaria (/ n ɪ ˈ d ɛər i ə, n aɪ-/ nih-DAIR-ee-ə, NY-) [4] is a phylum under kingdom Animalia containing over 11,000 species [5] of aquatic invertebrates found both in fresh water and marine environments (predominantly the latter), including jellyfish, hydroids, sea anemones, corals and some of the smallest marine parasites.
Cnidarians have huge numbers of cnidocytes on their tentacles. In medusoid form, the body floats on water so that the tentacles hang down in a ring around the mouth. In polyp form, such as sea anemone and coral, the body is below with the tentacles pointed upwards. The tentacles of the lion's mane jellyfish may be up to 37 m (121 ft) long. They ...
Between ectoderm and endoderm is a supporting layer of structureless gelatinous substance termed mesoglea, secreted by the cell layers of the body wall. [1] The mesoglea can be thinner than the endoderm or ectoderm or comprise the bulk of the body as in larger jellyfish.
Coelenterata is a term encompassing the animal phyla Cnidaria (corals, true jellies, sea anemones, sea pens, and their relatives) and Ctenophora (comb jellies). The name comes from Ancient Greek κοῖλος (koîlos) ' hollow ' and ἔντερον (énteron) ' intestine ', referring to the hollow body cavity common to these two phyla.
a Beroe ovata, b unidentified cydippid, c "Tortugas red" cydippid, d Bathocyroe fosteri, e Mnemiopsis leidyi, and f Ocyropsis sp. [17]. Among animal phyla, the ctenophores are more complex than sponges, about as complex as cnidarians (jellyfish, sea anemones, etc.), and less complex than bilaterians (which include almost all other animals).