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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.
Brittle stars, which have varying diets, have a blind gut with no intestine or anus; they expel food waste through their mouth. [34] Sea urchins are herbivores and use their specialised mouthparts to graze, tear and chew their food, mainly algae. They have an oesophagus, a large stomach and a rectum with the anus at the apex of the test. [35]
It has since been revealed that even if galeaspidans have just one external opening, it has two internal nasal organs. [5] [6] After the appearance of jawed fish (placoderms, acanthodians, sharks, etc.) about 420 million years ago, most ostracoderm species underwent a decline, and the last ostracoderms became extinct at the end of the Devonian ...
Many have fluid-filled, hydrostatic skeletons, like jellyfish or worms. Others have hard exoskeletons , outer shells like those of insects and crustaceans . The most familiar invertebrates include the Protozoa , Porifera , Coelenterata , Platyhelminthes , Nematoda , Annelida , Echinodermata , Mollusca and Arthropoda .
Anthozoa is a class of marine invertebrates which includes sessile cnidarians such as the sea anemones, stony corals, soft corals and sea pens.Adult anthozoans are almost all attached to the seabed, while their larvae can disperse as planktons.
Chitons have a shell composed of eight separate shell plates or valves. [3] These plates overlap slightly at the front and back edges, and yet articulate well with one another. Because of this, the shell provides protection at the same time as permitting the chiton to flex upward when needed for locomotion over uneven surfaces, and even allows ...
Agnatha (/ ˈ æ ɡ n ə θ ə, æ ɡ ˈ n eɪ θ ə /; [3] from Ancient Greek ἀ-(a-) 'without' and γνάθος (gnáthos) 'jaws') is a paraphyletic infraphylum [4] of non-gnathostome vertebrates, or jawless fish, in the phylum Chordata, subphylum Vertebrata, consisting of both living (cyclostomes) and extinct (conodonts, anaspids, and ostracoderms, among others).
Compared to shallow-water snailfish, Pseudoliparis swirei has several unusual adaptions for its dark and high pressure habitat, including transparent skin that lacks pigment, certain organs and eggs that are enlarged, the muscles are thinner, the ossification of its bones (notably the skull) is incomplete, it appears to have little or no ...