Chordata: Subphylum Tunicata
THE ASCIDIANS, or sea squirts, are the most common representatives on the shore of that interesting group of early chordates, the Tunicata. As forerunners of the vertebrates, or backboned animals, all of the chordates have at some time a stiffening rod of cartilaginous material, an evolutionary forecast of the vertebral column which all the higher animals were to possess. The adult ascidian paradoxically suggests a creature of low and simple organization, with a physiology somewhat like that of oysters or clams. It is only in the larva that the chordate characteristics are clear. Though minute, the larva strongly resembles the tadpole of a frog, possessing a notochord and a tail and swimming actively. At the end of the larval period it settles down, becomes attached, and undergoes metamorphosis to the much simpler adult form, in which the chordate characters are lost. This is a curious phenomenon of evolution, which seems to be degenerative rather than progressive, with the larva displaying more advanced characteristics than the adult.
The adult sea squirt is shaped like a bag with two tubular openings or siphons for water intake and outgo, and a pharynx perforated with many slits through which water is strained. The common name refers to the fact that when the animal is disturbed it contracts sharply, forcing jets of water out through the siphons. In the so-called simple ascidians the animals live as separate individuals, each enclosed in a tough covering or test of material chemically akin to cellulose. Sand and debris often adhere to this test, forming a mat in which the actual shape of the animal is seldom apparent. In this form they often grow profusely on wharf pilings, floats, and rocky ledges. In the compound, or colonial, type of ascidian many individuals live together, embedded in a tough gelatinous substance. Unlike a group of simple ascidians, the various individuals of a colony are derived by asexual budding from one individual, the founder of the colony. One of the commonest compound sea squirts is the sea pork, Amaroucium, named from the usually gray, gristly appearance of its colonies. These may form a thin mat on the under side of a rock or, offshore, grow erect, forming thick slabs that may break off and be carried in to shore. The individuals composing the colony are not easily seen, but under a lens pits in the surface appear, each the opening through which a single sea squirt communicates with the outside world. In the beautiful compound sea squirt Botryllus, however, the individuals form flowerlike clusters, easily visible.
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Index
Acmaea testudinalis, [>], [>], [>]–[>]
Actinopyga agassizi, [>]–[>]
Agarum turneri, [>]
Alaria esculenta, [>]–[>], [>]
Alcyonarians, [>]–[>]
Alcyonium digitatum, [>], [>]
Algae, [>]–[>]; coralline (sp. Lithothamnion), [>]–[>], [>], [>], [>] (see also Seaweeds)
Amaroucium sp., [>], [>]
Ammodytes americanus, [>]
Amphipods, [>], [>]–[>], [>]
Amphithoë rubricata, [>]–[>]
Amphitrite figulus, [>]
Anadara ovalis, [>]
Anadara transversa, [>]
Anemone, sand (Cerianthus americanus), [>] (see also Sea anemone)
Angel wing (Barnea costata), [>], [>]–[>]
Anomia simplex, [>]
Anthozoans, [>]
Anurida maritima, [>], [>], [>]
Aphrodite aculeata, [>]
Aplysia dactylomela, [>], [>]–[>], [>]
Apuleius, [>]
Area zebra, [>]
Arenicola marina, [>], [>], [>]–[>]
Argonauta argo, [>]
Aristotle, [>]
Arks, [>]
Arthropods, [>]–[>]
Ascidians, [>]–[>]
Ascophyllum nodosum, [>], [>]–[>], [>]
Asterias forbesi, [>]
Asterias vulgaris, [>], [>]–[>]
Astrophyton muricatum, [>]–[>]
Atlantic coast, geologic history of, [>]–[>], [>], [>]–[>]; topography of, [>]–[>], [>]–[>]
Atrina rigida or Atrina serrata, [>]
Amelia aurita, [>], [>]–[>]
Balanus balanoides, [>], [>]–[>]; enemies, [>]; habitat, [>]–[>], [>], [>]–[>], [>], [>]; reproduction, [>]–[>]
Barnacle, acorn or rock (see Balanus balanoides); gooseneck (Lepas fascicularis), [>]–[>]
Barnea costata, [>], [>]–[>]
Barracuda, [>]
Basket star (Astrophyton muricatum), [>]–[>]
Beach fauna, [>]–[>]
Beach flea (Talorchestia longicornis), [>], [>]–[>]
Bears Bluff, [>]
Bêche-de-mer, [>]
Bird Shoal, [>], [>]
"Black sands," [>]
Black zone of shore, [>]–[>]
Blackfish, [>]
Blenny, beach-hopping, [>]
Boat shell (Crepidula fornicata), [>]–[>]
Boreal zone, [>]–[>]
Botryllus schlosseri, [>], [>]–[>]
Brevoortia tyrannus, [>]
Bristle worms, [>], [>]–[>]
Brittle star, [>]; daisy (Ophiopholis aculeata), [>]–[>], [>]; West Indian (Ophiocoma echinata), [>]
Bryozoans, [>], [>]–[>], [>], [>], [>], [>]
Buccinum undatum, [>]
Busycon canaliculatum, [>]–[>], [>]
Busycon carica, [>]–[>], [>]
By-the-wind sailor (Velella mutica), [>]–[>]
Byssus cord, [>], [>], [>], [>], [>]–[>], [>]
Callianassa stimpsoni, [>], [>]–[>]
Callinectes sapidus, [>]
Cancer borealis, [>]–[>]
Cape Cod, [>], [>], [>]
Cape Hatteras, [>]
Cape Lookout, [>]–[>]
Carcinides maenas, [>], [>]
Cardinal fish, [>]
Cardisoma guanhumi, [>]
Caretta caretta, [>]–[>]
Cask shell (Tonna galea), [>], [>]
Cat's eye, [>]
Cerianthus americanus, [>]
Cerithidea costata, [>], [>]
Chaetopterus variopedatus, [>]–[>], [>]–[>]
Chelonia mydas, [>]–[>]
Chiton, [>]; West Indian (Chiton tuberculatum), [>]–[>]
Chondrus crispus, [>], [>], [>]–[>]
Cistenides gouldi, [>]–[>]
Clam, bloody (Anadara ovalis), [>]; coquina (Donax variabilis), [>]–[>]; razor, [>]; red-nose or rock-borer (Hiatella arctica), [>]–[>]; soft-shell (Mya arenaria), [>], [>], [>]
Clam worm (Nereis virens), [>]
Clava leptostyla, [>]–[>]
Cloth of gold, [>]–[>]
Clupea harengus, [>]–[>]
Clypeaster subdepressus, [>]
Cod (Gadus callarias), [>]
Coelenterates, [>]–[>]
Coenobita clypeatus, [>]–[>]
Coffee-bean shell (Melampus bidentatus), [>]
Comb jelly (Pleurobrachia pileus or Mnemiopsis leidyi), [>]
Conch, [>]; fighting (Strombus alatus), [>]; horse (Pleuroploca gigantea), [>]; king crown or common crown (Melongena corona), [>]; queen (Strombus gigas), [>]–[>]
Coral, [>]–[>], [>], [>]–[>], [>], [>], [>]
Coral coast, intertidal life, [>]–[>]
Coral reef flats, life of, [>]
Coral reefs, life of, [>]–[>]
Coralline algae (sp. Lithothamnion), [>]–[>], [>], [>], [>]
Cowfish (Lactophrys trigonus), [>], [>]
Crab, blue (Callinectes sapidus), [>]; fiddler (Uca pugilator, Uca pugnax), [>], [>]–[>]; gall (Cryptochirus corallicola), [>]; ghost (Ocypode albicans), [>], [>], [>]–[>]; green (Carcinides maenas), [>], [>]; hermit, [>]; hermit, purple-clawed (Coenobita clypeatus), [>]–[>]; horseshoe (Limulus polyphemus), [>], [>], [>], [>]–[>]; Jonah (Cancer borealis), [>]–[>]; mole (Emerita talpoida), [>], [>], [>]–[>]; pea (Pinnixa chaetopterana), [>], [>]–[>], [>]; spider (Stenorynchus seticornis), [>]; stone (Menippe mercenaria), [>]; white (Cardisoma guanhumi), [>]
Crepidula fornicata, [>]–[>]
Cryptochirus corallicola, [>]
Ctenophore,
[>]–[>] (see also Comb jelly)
Cucumaria frondosa, [>], [>]–[>]
Currents, relation to shore life, [>]–[>]
Cuvier, [>]
Cyanea capillata, [>], [>]–[>]
Cymodocea manitorum, [>]
Cyphoma gibbosum, [>]–[>]
Diadema antillarum, [>]–[>]
Diatoms, [>]
Diopatra cupraea, [>], [>]
Dodecaceria, [>]
Donax variabilis, [>]–[>]
Duke University, [>]
Dulse, [>], [>]
Echinoderms, [>]–[>]
Echinometra lucunter, [>]–[>]
Ectocrines, [>]
Eels, rock (Pholis gunnellus), [>]–[>]; sand or launce (Ammodytes americanus), [>]
Emerita talpoida, [>], [>], [>]–[>]
Enteromorpha intestinalis, [>]
Equatorial Current, [>]
Erectmochelys imbricata, [>]–[>]
Etrumeus sadina, [>]
Eucidaris tribuloides, [>]
Eunice fucata, [>]–[>]
Evolution toward land life, examples of: beach flea, [>]–[>]; coffee bean shell, [>]; ghost crab, [>]–[>]; periwinkles, [>], [>]–[>]; hermit crab, [>]; white crab. [>]
Fasciolaria hunteria, [>], [>]
Fierasfer bermudaensis, [>]–[>]
"Fireworms," [>]–[>]
Florida Keys, geologic history, [>]–[>]; life of, [>]–[>]; sands, [>]–[>]
Flotsam, shells in, [>]–[>]; strays found in, [>]–[>]
Flustrella hispida, [>], [>]
Foraminifera, [>], [>]
Fossil records, [>]–[>]
Fucus edentatus, [>]
Fucus spiralis, [>]
Fucus vesiculosis, [>]–[>]
Gadus callarias, [>]
Geologic history of Atlantic seacoast, [>]–[>], [>], [>]–[>]
Gerard, John, [>]–[>]
Gigartina stellata, [>]
Glauconite, [>], [>]
Gorgonia flabellum, [>]
Gorgonians, [>]; Leptogorgia sp., [>]; Pterogorgia acerosa, [>]–[>] Xiphigorgia anceps, [>]–[>]
Grasses, sea, [>], [>]–[>]; inhabitants of, [>]–[>]
Gray snapper, [>]
Gulf Stream, [>]–[>], [>]–[>]
Gulls, [>], [>], [>], [>]–[>], [>], [>]
Halichondria panicea, [>], [>], [>]
Hawk Channel, [>], [>], [>]
Henricia sanguinolenta, [>], [>]
Herring, round (Etrumeus sadina), [>]; sea (Clupea harengus), [>]–[>], [>]
Hiatella arctica, [>]–[>]
Hibernation of shore animals, [>], [>], [>]
Hippocampus hudsonius, [>]–[>]
Holdfasts, laminarian, inhabitants of, [>]–[>]
Holothurians, 277–[>], [>] (see also Sea cucumber)
Horn shell (Cerithidea costata), [>], [>]
Horny corals (see Gorgonians)
Horse conch (Pleuroploca gigantea), [>]
Horse mussel (Volsella modiolus), [>], [>]–[>]
Hydroid, club-headed (Clava leptostyla), [>]–[>]; pink-hearted (Tubularia crocea), [>], [>]; sertularian (Sertularia pumila), [>]–[>]
Hydroids, [>], [>], [>], [>]–[>]
Irish moss (Chondrus crispus), [>], [>]; inhabitants of, [>]–[>]
Janthina janthina, [>]–[>]
Jellyfish, red or arctic (Cyanea capillata), [>], [>]–[>]; white or moon jelly (Aurelia aurita), [>], [>]–[>]
Jingle shell (Anomia simplex), [>]
Jupiter Inlet, [>]
Kelp, [>], [>]; arctic, [>]; horsetail (Laminaria digitata), [>], [>]; long-stalked (Laminaria longicruris), [>]; sugar (Laminaria saccharina), [>]; winged (Alaria esculenta), [>]–[>], [>]
Lactophrys trigonus, [>], [>]
Laminaria digitata, [>], [>]
Laminaria longicruris, [>]
Laminaria saccharina, [>]
Laminarian seaweeds, [>], [>]–[>]
Laver, purple (Porphyra umbilicalis), [>]
Leathesia difformis, [>]
Lepas fascicularis, [>]–[>]
Lepidonotus squamatus, [>], [>]
Leucosolenia botryoides, [>]
Lichen, bearded (Usnea barbata), [>]; wall (Thelochistes parietinus), [>]
Ligia exotica, [>]
Limpet (Acmaea testudinalis), [>], [>], [>]–[>]
Limulus polyphemus, [>], [>], [>]
Linkia guildingii, [>]
Lithophaga bisulcata, [>], [>]
Lithothamnion sp., [>]–[>], [>], [>], [>]
Littorina angulifera, [>]
Littorina littorea, [>], [>], [>]
Littorina neritoides, [>]
Littorina obtusata, [>], [>]–[>]
Littorina saxatilis, [>], [>]–[>]
Lobster, spiny (Panulirus argus), [>]
Lugworm (Arenicola marina), [>], [>], [>]–[>]
Luidea clathrata, [>]
Lunatia heros, [>], [>], [>], [>]–[>]
Manatee grass (Cymodocea manitorum), [>]
Mangrove (Rhizophora mangle), [>], [>]–[>]
Mannitol, [>]
Marl, [>], [>], [>]
Martesia cuneiformis, [>]
Melampus bidentatus, [>]
Mellita testudinata, [>], [>]–[>]
Melongena corona, [>]
Membranipora pilosa, [>], [>]
Menhaden (Brevoortia tyrannus), [>]
Menippe mercenaria, [>]
Merluccius bilinearis, [>]
Metridium dianthus, [>], [>]–[>], [>]–[>]
Miami oölite, [>]
Microporella ciliata, [>]
Minnows, salt-water, [>]
Mnemiopsis leidyi, [>]
Moira atropos, [>], [>]
Mollusks, [>]–[>]
Monhegan Island, [>], [>]
Moon, influence on tides, [>]; on vegetation, [>]–[>]
Moon jelly (Amelia aurita), [>], [>]–[>]
Moon snail (Polinices duplicatus or Lunatia heros), [>], [>], [>], [>]–[>]
Mount Desert Island, [>]–[>]
Murlin (Alaria esculenta), [>]–[>], [>]
Mussel, common or blue (Mytilus edulis), [>], [>]–[>]; enemies of, [>]; habitat and life cycle, [>], [>]–[>]; and Sertularians, [>]–[>]
Mussel, date (Lithophaga bisulcata), [>], [>]
Mussel, horse (Volsella modiolus), [>], [>]–[>]
Mya arenaria, [>], [>], [>]
Myrtle Beach, [>]–[>]
Mytilus edulis (see Mussel, common or blue)
Nautilus, paper (Argonauta argo), [>]
Needlefish (Tylosura raphidoma), [>]
Nemerteans, [>], [>]–[>]
Nereid worms, [>], [>]–[>], [>], [>]
Nereis virens, [>]
Nerite (Nerita peloronta or Nerita versicolor), [>]–[>]
Noetia ponderosa, [>]
Nomeus gronovii, [>]
Oarweeds, [>], [>]
Octopus (Octopus vulgaris), [>], [>]
Ocypode albicans, [>], [>], [>]–[>]
Old man's beard (Usnea barbata), [>]
Onchidium floridanum, [>]–[>]
Oölitic limestone, [>]
Opercula, [>]–[>]
Ophiocoma echinata, [>]
Ophiopholis aculeata, [>]–[>], [>]
Oreaster reticulatus, [>]–[>]
Ostracods, [>], [>]
Ostrea frons, [>]
Oysters, [>]–[>]; larval, [>]–[>]; mangrove (Ostrea frons), [>]; pearl (Pteria colymbus), [>]
Palolo worm, Atlantic (Eunice fucata), [>]–[>]
Panulirus argus, [>]
Parchment worm (Chaetopterus variopedatus), [>]–[>], [>]–[>]
Pearl fish (Fierasfer bermudaensis), [>]–[>]
Pen shell (Atrina rigida or Atrina serrata), [>]
Periwinkle, beaded (Tectarius muricatus), [>]; common (Littorina littorea), [>], [>], [>]; European rock (Littorina neritoides), [>]; mangrove (Littorina angulifera), [>]; rough or rock (Littorina saxatilis), [>], [>]–[>]; smooth (Littorina obtusata), [>], [>]–[>]
Petalo
conchus, [>]–[>]
Phaeophyceae, [>], [>]
Pholis gunnellus, [>]–[>]
Physalia pelagica, [>]–[>]
Piddock, wood (Martesia cuneiformis), [>]
Pinnixa chaetopterana, [>], [>]–[>], [>]
Pipefish (Syngnathus sp.), [>]–[>]
Platyhelminths, [>]
Pleurobrachia pileus, [>]
Pleuroploca gigantea, [>]
Pliny, [>]
Plumed worm (Diopatra cupraea), [>], [>]
Polinices duplicatus, [>], [>], [>], [>]–[>]
Polysiphonia lanosa, [>]
Ponderous ark (Noetia ponderosa), [>]
Porphyra umbilicalis, [>]
Portuguese man-of-war (Physalia pelagica), [>]–[>]
Pourtalès Plateau, [>]
Protophytes, [>]
Protozoans, [>]–[>]
Purple sail (Veletta mutica), [>]–[>]
Purpurin, [>], [>]
Radula, dog whelk, [>]; limpet, [>]–[>]; periwinkle, [>]
Ralfsia verrucosa, [>]–[>]
Ramshorn shell (Spirula spirula), [>]–[>]
Red tides, [>]
Redi, [>]
Renilla reniformis, [>]–[>]
Rhizophora mangle, [>], [>]–[>]
Rhodymenia palmata, [>], [>]
Ribbon worms, [>], [>], [>]–[>]
Rock tripe (Umbilicaria sp.), [>]
Rocks as records of history, [>]–[>]
Rockweed (see Wrack)
Rocky shores, life of, [>]–[>]
Sand, fauna of, [>]–[>]; types of, [>]–[>]
Sand anemone (Cerianthus americanus), [>]
Sand dollar (Mellita testudinata), [>], [>]–[>]
Sand hopper (see Beach flea)
Sangamon interglacial period, [>]–[>]
Sanibel Island, [>], [>], [>]
Scale worm (Lepidonotus squamatus), [>], [>]
Scaphanders, [>]
Screwshell snail (Terebra), [>]
Scyphozoans, [>]
Sea anemone, arctic, [>]; plumose (Metridium dianthus), [>], [>]–[>], [>]–[>]
Sea birds, [>]–[>], [>] (see also Gulls)
Sea biscuit (Clypeaster subdepressus), [>]
Sea bottle (Valonia macrophysa), [>]
Sea colander (Agarum turneri), [>]
Sea cucumber, [>]–[>]; northern (Cucumaria frondosa), [>