Tropical Marine Invertebrates CAS BI 569 Phylum Chordata by J. R. Finnerty Porifera Ctenophora Cnidaria Deuterostomia Ecdysozoa Lophotrochozoa Chordata Arthropoda Annelida Hemichordata Onychophora Mollusca Echinodermata *Nematoda *Platyhelminthes Acoelomorpha Calcispongia Silicispongiae PROTOSTOMIA Phylum Chordata subPhylum VERTEBRATA subPhylum UROCHORDATA class Ascidaceae—the “sea squirts” class Larvaceae—the larvaceans class Thaliaceae—the salps subPhylum CEPHALOCHORDATA—the “lancelets” Subphylum Subphylum Subphylum Phylum Phylum Vertebrata Urochordata Cephalochordata ECHINODERMATA HEMICHORDATA Phylum CHORDATA Notochord Blastopore -> anus Dorsal hollow nerve cord Radial / equal cleavage Pharyngeal gill slits Coelom forms by enterocoely Endostyle Cross-section through a Chick embryo During Neurulation Subphylum Vertebrata Ordovician Origins—Jawless fishes vertebral column paired appendages post-anal tail Jawed fishes, gnathostomes late Ordovician, early Silurian jaws early Devonian / late Devonian tetrapods / amniotes Permian (299-251) Carboniferous subphylum VERTEBRATA (359-299) gnathostomes (with jaws) 1. Vertebral column Devonian 2. Paired appendages (416-359) 3. Jaws 4. Post anal tail Silurian (444-416) Bony fishes Cartilaginous fishes Paleozoic (543-225) Fishes with jaws & paired fins Ray-finned & Lobe-finned fishes Ordivician Jawless fishes (488-444) Vertebrate origins Jawless fishes phylum CHORDATA Cambrian 1. Dorsal nerve cord (542-488) Non-vert chordates “Cambrian explosion” 2. Notochord Rapid appearance of most 3. Gill slits Animal phyla in fossil record Including Phylum Chordata 4. Endostyle Permian (299-251) 4 3 2 1 1.Pre-mammal-like reptiles 2. Snake-lizard ancestor 3.Crocodile-Bird-Dino ancestor 4. Turtles Carboniferous (359-299) amphibians Early reptiles. Devonian (416-359) Vertebrates invade land “Age of amphibians” Silurian (444-416) Bony fishes AMNIOTES Cartilaginous fishes Paleozoic (543-225) Fishes with jaws & paired fins 1. Terrestrial Ray-finned & Lobe-finned fishes 2. Amniotic sac in egg. Ordivician Jawless fishes (488-444) Vertebrate origins Jawless fishes Cambrian (542-488) Non-vert chordates “Cambrian explosion” Rapid appearance of most Animal phyla in fossil record Including Phylum Chordata Subphylum Vertebrata Archetypal vertebrate (lamprey-like) Subphylum Vertebrata Tetrapod Subphylum Cephalochordata 30 described species known as “lancelets” Blade-shaped (laterally-compressed, tapered at both ends) 4-8 cm long Looks like a skinless, headless, boneless fish Rapid undulatory swimmers Burrow in porous sediments Reach high densities in favorable environments (5000/m2) Harvested for food in southeast Asia. Thirty-five tons (=1 billion individuals) were once harvested from an area of 6 square miles in a single year. Subphylum Cephalochordata Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Subphylum Urochordata Most diverged from the basic chordate body plan. Except for one group (the larvaceans), the adults lack a notochord, a dorsal hollow nerve cord, and a post anal tail. The larva, called a tadpole, possesses all of the diagnostic chordate features. Coelom is lacking. The gut is U-shaped. Many colonial species—the only colonial chordates. Class Ascidacea—the ascidians—are sessile filter feeders. Class Thaliacea—the salps—are planktonic filter feeders. Class Larvacea—the larvaceans—are planktonic filter feeders. Urochordates make use of mucous nets in feeding. Subphylum Urochordata Class Ascidiacea (ascidians or tunicates) incurrent siphon excurrent siphon pharynx Source: Biology 7e by Raven et al. Subphylum Urochordata Class Ascidiacea (ascidians or tunicates) Source: Ruppert et al. Invertebrate Zoology Subphylum Urochordata Class Ascidiacea (ascidians or tunicates) Source: Biology 7e by Raven et al. Subphylum Urochordata Class Ascidiacea (ascidians or tunicates) Ruppert et al., Invertebrate Zoology, figure 29-25 Salp Anatomy Subphylum Urochordata Class Thaliacea (“salps”) Ruppert et al., Invertebrate Zoology, figure 29-28 Salp Feeding "We had long thought that salps were about the most efficient filter feeders in the ocean,” said Laurence P. Madin, WHOI Director of Research and one of the investigators. “But these results extend their impact down to the smallest available size fraction, showing they consume particles spanning four orders of magnitude in size. This is like eating everything from a mouse to a horse." Salps capture food particles, mostly phytoplankton, with an internal mucous filter net. Until now, it was thought that their menu was limited to particles only as large as or larger than the 1.5-micron-wide holes in the mesh. But a mathematical model suggested salps somehow might be capturing food particles smaller than that, said Kelly R. Sutherland, who wrote the paper as part of her PhD thesis at the MIT/WHOI Joint Program for graduate students. In the laboratory at WHOI, Sutherland and her colleagues offered salps food particles of three sizes: smaller, around the same size as, and larger than the mesh openings. http://www.whoi.edu Salp Feeding “We found that more small particles were captured than expected,” said Sutherland, now a postdoctoral researcher at Caltech. “When exposed to ocean-like particle concentrations, 80 percent of the particles that were captured were the smallest particles offered in the experiment." .....it helps explain how salp--which can exist either singly or in “chains” that may contain a hundred or more--are able to survive in the open ocean, their usual habitat, where the supply of larger food particles is low. Madin, who served as Sutherland’s advisor at WHOI, adds: “Their ability to filter the smallest particles may allow them to survive where other grazers can't.” http://www.whoi.edu Salps & Carbon Cycling? “Free-floating sediment traps were suspended at 200 and 900 m in the northern North Pacific Ocean during 20-21 May, 1974. A considerable amount of large, dark-green particles, larger than 1 mm in diameter, was collected at both depths. These large particles corresponded morphologically with fecal pellets of salps. Vertical carbon flux was estimated to be 10.5 and 6.7 mg C m-2 d-1 at 200 and 900 m, respectively. This suggests that vertical transport of salp fecal pellets could play an important role in meeting the energy requirements of bathypelagic organisms in the open ocean.” K. Iseki (1981) Particulate organic matter transport to the deep sea by salp fecal pellets. Mar. Ecol. Prog. Ser. 5:55-60. Quoted at: http://whyevolutionistrue.wordpress.com Salps & Carbon Cycling? ....it enhances the importance of the salps’ role in carbon cycling. As they eat small, as well as large, particles, “they consume the entire 'microbial loop' and pack it into large, dense fecal pellets,” Madin says. The larger and denser the carbon-containing pellets, the sooner they sink to the ocean bottom. “This removes carbon from the surface waters,” says Sutherland, “and brings it to a depth where you won’t see it again for years to centuries.” And the more carbon that sinks to the bottom, the more space there is for the upper ocean to accommodate carbon, hence limiting the amount that rises into the atmosphere as CO2, explains co-author Roman Stocker of MIT’s Department of Civil and Environmental Engineering . http://www.whoi.edu Subphylum Urochordata Class Larvacea (“larvaceans”) PHOTO BY: Russ Hopcroft, Institute of Marine Science, University of Alaska Fairbanks (UAF) Ascidian vs. Larvacean development Ruppert et al., Invertebrate Zoology, figure 29-34 Hemichordata: Enteropneusta Hemichordata: Enteropneusta cleavage Radial Radial Radial Radial Radial mouth form. deut deut deut deut deut coelom form. entero- entero entero entero entero pharyngeal no yes yes yes yes slits (sometimes) D nerve cord no yes yes yes yes (sometimes) echinoderms hemichordates cephalochordates urochordates vertebrates ? Dorsal hollow nerve cord Notochord Pharyngeal gill slits Deuterostomy Endostyle Radial cleavage Enterocoely.