4Phylum SipunculaThe Phylum Sipuncula (from Latin: meaning “little pipe”) consists of approximately 250 species of benthic, marine wormlike animals, most from cm in length (range 2mm to 70cm).Sipunculids produce a trochophore larva similar in structure to that of the annelids.
5Phylum SipunculaSometimes 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
8Phylum SipunculaThe 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.
10Phylum SipunculaSipunculids 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
11Phylum SipunculaThe 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.
12Sipunculid clip Sipunculid burying itself one minute
14Phylum EntoproctaAKA 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.
16Phylum EntoproctaEntoproct 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.
17Phylum EntoproctaEntoprocts 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.
18Phylum EntoproctaReproduction 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.
20Phylum RotiferaRotifers are named for their characteristic ciliated crown or corona, which when it beats looks like a rotating wheel.Rotifers are tiny animals (most are µm 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.
22Phylum RotiferaThe 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.
24Phylum RotiferaOne 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.
26Phylum RotiferaBecause 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.
28Phylum 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.
30Phylum Acanthocephala Bilaterally symmetricalNo gutBody unsegmentedProminent spiny proboscisBody cavity is a pseudocoelom (mesoderm lines only outer edges of blastocoel, body cavity not lined with peritoneum).No respiratory or circulatory systemSimple nervous system single anterior ganglion with connecting nerves to organs.
33Phylum 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.
34Phylum 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.
35Phylum 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.
36Phylum 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.
37Phylum 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.
39Phylum EctoproctaAlso 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.
41Phylum 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
42Phylum EctoproctaThe 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).
43Phylum EctoproctaOther 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.
45Phylum EctoproctaColonies 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.
46Phylum EctoproctaEctoprocts 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).
49Phylum 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.
51Brachiopod characteristics The body is enclosed within a symmetrical bivalve shell as is the case in molluscs. However, unlike molluscs brahiopods have a dorsoventrally oriented shell with two unequally sized valves unlike molluscs which have left and right valves.
52Phylum BrachiopodaBrachipods possess a stalk or pedicle (1-30cm in length), which is typically attached to rock or anchored in sedimentA large, anterior mantle cavity contains the lophophore which is used for suspension feeding.
53Brachipod cross section: http://aalliiffaazzeellii. googlepages Principal organs of a brachiopod as typified by Terebratulina. (After R. C. Moore, ed., Treatise on Invertebrate Paleontology, pt. H, Geological Society of America, Inc., and University of Kansas Press, 1965)
54Phylum BrachiopodaThe lophophore occupies much of the internal space of the brachipod and has a branched rather than circular structure (hence the name as brach means a branch) with complex folding of the lophophore being common.
58Phylum PhoronidaSometimes called horseshoe worms they build tubes of chitin and filter feed using a lophophore.The are marine and occur in sediments between the intertidal and about 400m depth.
59Phylum PhoronidaMost phoronids range in length from 2-20cm, but can reach 50 cm.They secrete a tube of chitin and the lower end of the animal is swollen into an ampulla, which anchors the animal and allows it to quickly retract its lophophore into the tube.
60Phylum PhoronidaPhoronids can be extremely abundant numbering thousands of individuals per sq. meter. They are unpalatable to many predators and that likely explains the high densities.
61Phylum PhoronidaPhoronids feed on a variety of small filterable prey including algae, small invertebrates and flagellates which are caught using the lophophore.
62Phylum PhoronidaSome species are hermaphroditic and the rest dioecious. Eggs are in many species brooded for a while before being released into the water.Most species develop free-swimming larvae that feed on plankton that they catch using tentacles.
64Phylum PhoronidaAfter a larval period of about 20 days the larva settles on the bottom and in about 30 minutes undergoes a rapid metamorphosis in which the larval hood and tentacles are reabsorbed, the adult lophophore is formed and the gut forms a u-bend with the anus opening outside the tentacles.
65Phylum PhoronidaThere are only a dozen described species, but this is certainly an underestimate as more than 25 larval forms have been described.