Lophotrochozoa “Minor Phyla”

Lophotrochozoa “Minor Phyla”

Eutrochozoa: Rotifera, Acanthocephala, Entoprocta,Platyhelminthes, Nemertea, Mollusca, Sipuncula, Annelida Lophotrochozoa Lophophorata: Ectoprocta, Brachiopoda, Phoronida Protostomia Ecdysozoa: Onychophora, Tardigrada, Arthropoda, Nematoda, Nematomorpha, Kinorhyncha, Loricifera, Priapulida Cuticulata Gastrotricha

Platyhelminthes Parenchymia Nemertea Annelida Mollusca Sipuncula Entoprocta Rotifera Acanthocephala Lophotrochozoa Ectoprocta Lophophorata Brachiopoda Phoronida

Phylum Sipuncula • The Phylum Sipuncula (from Latin: meaning “little pipe”) consists of approximately 250 species of benthic, marine wormlike animals, most from 15-30 cm in length (range 2mm to 70cm). • Sipunculids produce a trochophore larva similar in structure to that of the annelids.

Phylum Sipuncula • Sometimes referred to as the “peanut worms” (probably for the gridlike pattern on their epidermis) most sipunculids burrow in sand or silt or occupy crevices or empty mollusc shells or worm tubes

http://www.glaucus.org.uk/Sipunculus-nudus-RL.jpg

Sipunculid clip • One minute clip of sipunculid • http://www.youtube.com/watch?v=S1zQCa5cfcQ

Phylum Sipuncula • The body is unsegmented and divided into an anterior introvert and a posterior trunk. • The introvert is a retractile structure at the anterior end of the animal and can be half the body length. • Sipunculids have a fluid filled coelom and a hydrostatic skeleton. The pressure of the fluid in the coelom is used to extend the introvert.

http://www.eol.org/pages/8871

Phylum Sipuncula • Sipunculids are generally non-selective deposit feeders and they use the ciliated tentacles or lobes surrounding the tip of the introvert to collect food. • They eat a variety of small easy to acquire food items: algae, unicellular organisms, larvae and detritus

Phylum Sipuncula • The introvert is also used to burrowing into sediments. • Coelomic pressure is used to extend the introvert into the sediment and anchor it in place. Retractor muscles then contract pulling the introvert forward and drawing the rest of the animal forward.

Sipunculid clip • Sipunculid burying itself one minute • http://www.youtube.com/watch?v=aq6kEX9igeI

Phylum Entoprocta • AKA the kamptozoans or the “goblet worms”, entoprocts are small (1cm), sessile marine animals most of which are colonial. • The body, which is covered by a thin external cuticle consists of a long mobile contractile stalk topped by a calyx, which contains the organs and a crown of tentacles.

http://www.biocyclopedia.com/index/general_zoology/phylum_entoprocta.phphttp://www.biocyclopedia.com/index/general_zoology/phylum_entoprocta.php

Phylum Entoprocta • Entoproct means “anus inside” and this refers to the fact that the mouth and the anus are surrounded by the ring of tentacles. • The tentacles are solid and non rectracile, Instead they can be rolled up and covered by the intertentacular membrane.

Phylum Entoprocta • Entoprocts occur in shallow water and feed on suspended particles that they trap using mucus covered cilia on their tentacles. • The food is directed down the tentacles to the mouth.

Phylum Entoprocta • Reproduction occurs either asexually by budding or sexually (they are hermaphroditic). • Fertilized eggs are incubated in a pouch within the calyx and the embryos are fed by parental cells. The embryo develops into a free-swimming trochophore larva that settles and metamorphoses into the adult form.

Phylum Rotifera • Rotifers are named for their characteristic ciliated crown or corona, which when it beats looks like a rotating wheel. • Rotifers are tiny animals (most are 100-300µm long and the largest only 3mm long) the majority of which live in freshwater and are benthic inhabitants (live on the bottom). • About 2000 species have been described.

9.1

Phylum Rotifera • The beating of the cilia in the corona draws in plankton-containing water for food. • The mouth opens to a modified muscular pharynx known as a mastax, which is a structure unique to rotifers. • The mastax has a set of complex jaws, which are used to grasp and chew food.

Rotifer video 1 minute • http://www.youtube.com/watch?v=cYNJOVDQexA

Phylum Rotifera • One group of rotifers, the Bdelloid rotifers, are very unusual in that there are no males, hermaphrodites, or evidence of meiosis. • Molecular evidence suggests that there has been only asexual reproduction in this group for several million years.

http://www.arcodiv.org/seaice/rotifers/Antarctic_rotifer_Philodina_gregaria_400x300.jpghttp://www.arcodiv.org/seaice/rotifers/Antarctic_rotifer_Philodina_gregaria_400x300.jpg

Phylum Rotifera • Because of the problem of accumulation of deleterious mutations in lineages of exclusively asexually reproducing animals (a process known as Muller’s ratchet) it is unclear how the bdelloids have been able to dispense with sexual reproduction entirely. • Other rotifers reproduce using a combination of sexual and asexual reproduction.

Phylum Acanthocephala • Acanthocephalans are commonly known as spiny-headed worms because of the spiny eversible proboscis they use to attach to the gut of their host. • All 1100 species of Acanthocephalan are endoparasitic and most parasitize fish, birds and mammals. Most small 1mm to 3-4cm a few up to 1m long.

http://rydberg.biology.colostate.edu/Dissections/acanthocephala/acanthfemmal.jpghttp://rydberg.biology.colostate.edu/Dissections/acanthocephala/acanthfemmal.jpg

Phylum Acanthocephala • Bilaterally symmetrical • No gut • Body unsegmented • Prominent spiny proboscis • Body cavity is a pseudocoelom (mesoderm lines only outer edges of blastocoel, body cavity not lined with peritoneum). • No respiratory or circulatory system • Simple nervous system single anterior ganglion with connecting nerves to organs.

9.3

http://upload.wikimedia.org/wikipedia/commons/9/99/Acanthocephala_Rhadinorhynchus.jpghttp://upload.wikimedia.org/wikipedia/commons/9/99/Acanthocephala_Rhadinorhynchus.jpg Acanthocephalan proboscis

Phylum Acanthocephala • Body wall covered with numerous minute depressions which increase the surface area of tegument and facilitate (as in cestodes) absorption of food from host’s gut. • As in cestodes, Acanthocephalans lack a gut.

Phylum Acanthocephala • Acanthocephalans have a lifecycle in which a vertebrate is the definitive host (in alimentary canal) and an invertebrate the intermediate host. • Acanthocephalans, as other parasites do, modify the behavior of the intermediate host to enhance the chances of its being eaten.

Phylum Acanthocephala • For example, acanthocephalans that parasitize Gammarus, a small freshwater crustacean, cause the Gammarus to alter its behavior in the presence of ducks, a common predator. • Instead of diving to the bottom when a duck appears, the Gammarus swims into the light and grasps tightly onto a piece of vegetation, greatly increasing its chances of being eaten.

Phylum Acanthocephala • The change in behavior appears to be caused by the Acanthocephalan pumping a serotonin-boosting molecule into the Gammarus’ brain. • This causes the Gammarus to think it’s having sex and cling as it would if mating. Interestingly, the parasite’s manipulation also causes female Gammarus to mimic the males mating behavior.

Phylum Acanthocephala • Another Acanthocephalan that parasitizes pill bugs causes them to reverse their normal behavior and avoid humid, dark areas. • Instead they wander in the open where they are much more vulnerable to birds, the acanthocephalans definitive host. • The parasite’s manipulations are very effective. Although fewer than 1% of pill bugs are typically infected with acanthocephalan parasites, 30% of pill bugs delivered to nestlings are infected.

Phylum Ectoprocta • Also known as the bryozoans or moss animals they are small (<0.5mm) colonial animals, but colonies can be up to 1 meter across (although most are 10cm or so) • Most are marine and form masses on rocks and other substrates where they feed on phytoplankton and other small organisms which they catch using cilia on their lophophore.

Lophopodella carteri lophophore http://www.bio.umass.edu/biology/conn.river/bryozoa.html

Phylum Ectoprocta • Individual zooids are genetically identical. • The zooids are connected to each other and surrounded by a protective calyx as in entoprocts. • Most zooids are feeding zooids called autozooids. These use the lophophore to feed. The tentacles are extended by hydrostatic pressure and prey is trapped using cilia

Phylum Ectoprocta • The lophophore and mouth are mounted on a tube called an invert that can be everted through an opening in the calyx and rapidly withdrawn if threatened. • The mouth is found within the ring of tentacles but the anus is outside the ring (in contrast to entoprocts).

Phylum Ectoprocta • Other types of zooids include spinozooids which possess protective spines, gonozooids, which act as brood chambers for developing eggs and modified autozooids called avicularia which use a modified operculum to snap at threatening organisms.

www.marlin.ac.uk

Phylum Ectoprocta • Colonies of ectoprocts in freshwater temperate habitats die in the fall, but leave behind statoblasts, which are groups of cells surrounded by a protective envelope. • Zooids emerge in the spring and a new colony forms by budding.

Phylum Ectoprocta • Ectoprocts have a rich fossil record and over 15,000 fossil species have been described. • Fossils are known from as far back as the Cambrian period (500mya).

Phylum Ectoprocta • Ectoproct video 1 minute • http://www.youtube.com/watch?v=tpifpqrQKRA

Phylum Brachiopoda • Greek: brachion:branch; pous: foot. • The living brachiopods are the remnants of a once much more diverse group. There are about 335 living species vs > 26,000 fossil species. • Superficially similar in lifestyle and external appearance to bivalve molluscs.

http://paleo.cortland.edu/tutorial/Brachiopods/Brachiopod%20Images/lingula.GIFhttp://paleo.cortland.edu/tutorial/Brachiopods/Brachiopod%20Images/lingula.GIF

Lophotrochozoa “Minor Phyla”