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Lecture Ctenophora(Comb Jellies)

Phylum Ctenophora

•The Comb jellies•Resemble cnidarian medusas.•Use cilia for locomotion.

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Phylum Ctenophora (Comb Bearers)

• Defining Characteristics– Plates of fused cilia

arranged in rows for swimming

– Adhesive prey capturing cells (colloblasts) ontentacles

• Comb jellies are delicate, transparent, non-stinging predators

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Ctenophore Structure• Body surface has two large tentacles and

eight rows of comb-like paddles• Comb paddle has thousands of cilia used

to swim• Their tentacles have the adhesive

colloblasts to capture prey and they have a stomach, mouth, pharynx, and anal pores.

• They have a nerve network that is rather complex and an apical sense organ.

• All ctentophores are hermaphrodites and most reproduce sexually.

• They generally range in size from .6 cm to 30.5 cm.

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Apical Sense Organ

• Apical sense organ located on the aboral surface controls beating of cilia– Statolith and

balancers

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Colloblasts

• Colloblasts are a cell type found in ctenophores. They are widespread in the tentacles of these animals and are used to capture prey.

• Sticky retractile tentacle used to catch prey – Colloblast discharge an adhesive

thread which is sticky to the touch• Some spp. lack tentacles and the

body is studded (=scattered) with colloblasts

Colloblasts (Morphology)

• Colloblasts are microscopic, sticky structures used to adhere to the prey of a ctenophore. Usually the classes Cydippida and Lobatahave colloblasts on their tentacles.

• After a prey is caught by a colloblast, the tentacle is contracted and the prey is brought by the predator’s mouth. There the prey is released and ingested.

CHARACTERISTICS• All ctenophores are bioluminescent, meaning they are capable of

producing light. Bioluminescence is caused by the activation of calcium-activated proteins named photoproteins in cells called photocytes, which are often confined to the meridional canals that underlie the eight comb rows.

• Two types of chemicals involved in light production, called luciferin and luciferase, are bound together in a photoprotein. This molecule can be triggered to produce light when calcium is added to the system. Photoproteins emit flashes of very bright light for a fraction of a second

CHARACTERISTICS• Ctenophores have two digestive openings, but rarely use the

anus for defecation• Bi-radial symmetry and three germ layers (epidermis,

gastrodermis, mesoglea if included)• Mesoglea holds muscle cells and amoebacytes• All Ctenophores have a distinct larval form before adulthood

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Ctenophore diversity

• Most species live in the open ocean and are not well studied– New studies use submersibles and divers to collect

specimens, eliminating specimen destruction by fast towed nets

• Phylum Ctenophora– Order Cyphidds– Order Lobata– Order Beroida

Order Cydippids (Morphology)

•Egg-shaped bodies (sea gooseberry)•Order includes pleurobrachia•Tentacles on opposite sides of body•Body can be flattened to increase range of tentacles•Tentacles have tentilla (small branched tentacles) with colloblasts•Generally coil around prey to kill•Combs are spaced evenly around the body

Lobata (Morphology)

•Order also called Lobates•Have pair of muscular lobes extending from mouth (Darth Vader?)•Two comb rows on each lobe and two on each side between lobes•Some can clap combs to push water rapidly and move opposite

Auricle : ciliated ribbon-like projections

•Tentacles in grooves on lobes, have auricles between lobes and mouth•Auricles have cilia to create current and flush prey into the mouth•Generally prey on plankton

Lobata (Morphology)

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Order Beroida

• Order also known as Nuda• No feeding appendages, but pharynxes

have macrocilia• Marcocilia are large bundles of cilia that

work to bite off pieces of whatever is being consumed

• Prey on other ctenophores• When not eating, a ridge shuts the mouth

by connecting with the other part of the ridge

• Can consume prey substantially larger than itself

(A) Pleurobrachia bachei deploys a web of sticky tentacles to capture active prey.

(B) Bathyctena chuni from the deep Pacific with its mouth.

(C) Dryodora glandiformis, a polar species that specializes in larvaceans. (D) The lobate Ocyropsis maculataimmaculata has no functionaltentacles as an adult and uses its muscular lobes to capture prey directly. (E) The ‘‘showercap’’ ctenophore Thalassocalyce inconstans from the aboralend. In this species, the lobes are fused and there are no auricles.(F) The lobate Leucothea pulchra viewed along the body axis from the oral end; it is swimming straight toward the viewer. Note the sinuous auricles (au) (G) Beroe forskalii, having ingested a large portion of a Leucothea. The comb rows(arrowheads) and orange papillae of the prey can be seen inside

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Digestion• Feed on plankton, other ctenophores and other Cnidarian

jellies• Gut extends through the entire body; mouth is at the oral end• Anal pore is at the aboral end• The prey of cydippid and lobate ctenophores in general

includes small crustaceans such as copepods, amphipods, and even euphausiids (krill), and larvae of other marine invertebrates such as clams and snails.

• the principal prey of beroid ctenophores is other ctenophores. In turn, ctenophores are eaten by many species of medusae(jellyfish) as well as by sea turtles and some fish.

Digestion

•Enzymes and contractions of pharynx liquidize prey•Cilia move the resultant mush into the stomach canal system•Nutritive enzymes break down the mush in the stomach•Ciliary rosettes in canal transfer nutrients to muscles in mesoglea•Most waste is ejected through the mouth, rarely through the anal pores.•Exact mode of excretion is unknown

Development (Embryology)

Development (Embryology)

Nature 510, 109–114Remarkably distinct from other animal genomes in their content of neurogenic, immune and developmental genes.

Ecological impacts• in the late 1980s the Western Atlantic

ctenophore Mnemiopsis leidyi was accidentally introduced into the Black Sea and Sea of Azov via the ballast tanks of ships,

• Mnemiopsis can breed very rapidly and tolerate a wide range of water temperatures and salinities.

• The impact was increased by chronic overfishing, and by eutrophication

Changes in the Black Sea pelagic foodweb due to overfishing and Mnemiopsis introduction

https://www.youtube.com/watch?v=pimIbTqJLZc&ebc=ANyPxKrstYQIQsHL7gTMWe_dROiDEG42HJDmBwC1KBgy1iXtSZCl-K0VuBTaPEPOPp577s3ydq54HpeJO8UrDlTJdycBBy4VeQ

http://highered.mheducation.com/novella/MixQuizProcessingServlet

https://www.youtube.com/watch?v=eDS_NMrPPKc&ebc=ANyPxKoeLK36eugOjCtHIiHFM77sBmkZmmC7riQ1mfxJSyITkml2nG85MQRgEwAxysXXcnCUc7h2zSGRTAgUwaL38KLsE2qbaQ

https://www.youtube.com/watch?v=d7DGsXLBORg

General characteristics of Phylum Ctenophora1) Biradial symmetry in most spp.2) Ellipsoidal body shape3) Mostly triploblastic4) Only one sp. having cnidocytes w/ nematocysts; All spp. have coloblasts = adhesive cells.5) GVC (gastrovascular cavity)6) Statocyst sense organs : controlling equilibrium.7) No polymorphism.8) Reproduction sexually in monoecious individuals (both male and female sex cells produced by some individuals.9) Luminescence (biochemical light production process involving enzymatic hydrolysis of ATP).