Animal Diversity (2)

Invertebrates - sponges, Cnidarians, and Lophotrochozoans

What are invertebrates?

Animals that lack a backbone

Occupy almost every habitat on Earth

Phylum Porifera

Informally known as “sponges.”

Most are marine

Sessile/sedentary (fixed in one place) as adults

• First thought of plants

Lack tissues (not true animals), but still have diverse cell types

• Groups of similar cells that act as a functional unit, as in muscle tissue and nervous tissue

• Not eumetazoans

Filter feeders

Phylum Porifera
Filter out generally large food particles that are commonly suspended in the water column

Spongocoel

Central cavity of a sponge

Osculum

Opening that connects spongocoel to environment

Choanocytes

Flagellated cells that engulf bacteria and other food particles by phagocytosis. Cells that create water currents and capture food

Amoebocytes

amoeba-like cell that moves by pseudopodia

They have many functions

They take up food from the surrounding water and from choanocytes, digest it, and carry nutrients to other cells

Totipotent

Amoebocytes are totipotent

Capable of becoming other types of sponge cells

Flexibility in the sponge body: adjust its shape in response to changes in its physical environment

Basal Animals

Diverged from other animals early in the history of the group

Hermaphrodites

Each individual functions as both male and female in reproduction by producing sperm and eggs

Sequential “hermaphroditism” - function first as one sex and then as the other (also seen in clownfish)

Sexual/Asexual

Produce sperm and eggs

Budding

Cribrostatin

Kills both cancer cells and penicillin -resistant strains of Streptococcus spp. Other sponge-derived compounds are being tested as possible anticancer agents

-Porifera - can produce antibiotics and defensive compounds, which can be used to fight human diseases!

Phylum Cnidaria

Eumetazoan - “true animals” (have tissues)

Includes (both sessile and motile) hydras, corals, jellies

Radial Body Plan

Diploblastic

Have a gastrovascular cavity - central digestive compartment

Polyps

large, sessile (hydras and sea anemones)

Medusae

Smaller, motile (free swimming jellies)

Some only exist as one, some have both stages during their lifecycle

Cnidocytes

Protection + capturing prey - Stinging cells.

Nematocysts

A stinging thread that can penetrate the body of prey: Found within the Cnidocytes

Since Cnidaria have no brain…

Movements are coordinated by a noncentralized nerve net that is associated with sensory structures distributed around the body: Nerve Net

Medusozoans

Cnidarians that produce a medusa

Anthozoans

Cnidarians that only exist as polyps

Class Medusozoa

Jellies (scyhozoans)

• Spends most of its life in medusa stage

Box Jellies (Cubozoans)

• Spends most of its life in the medusa stage “cube animals” box shaped medusa stage

Chironex fleckeri

Northern Australia

One of the deadliest organisms known

Its sting…

• Intense pain, respiratory failure, cardiac arrest, death

Obelia, Sipophores (hydrozoans)

Alternate between polyp and medusa

Spends most of their life in the polyp stage

What about the other two?

• Exhibit different types of polyps designed to perform different function

Class Anthozoa

Sea anemones and corals

Only occur as polyps

Many secrete exoskeletons made of calcium carbonate

Coral Bleaching

Increase in seawater temperatures clears out their algal symbionts

(Anthozoa)

The loss of symbiotic algae living within coral tissues

Bilateria - Lophotrochozoa

Bilateral symmetry

Tripoblastic

Most of them have a digestive track with two openings

Phylum Plathelminthes

“Flat worm”

Flatworms - do they have a body cavity?

Parasitic - flukes, tapeworms

• Not all are parasitic

Tripoblastic

• But still no body cavities

“Eye” spots to detect light

They mostly prefer dark environment

Since the phylum platyhelminthes do not have organs for gas exchange…

Instead, they have relatively simple excretory apparatus that function mainly to maintain osmotic balance with their surroundings

Planarians

Free-living flatworms found in ponds and streams

• Feed on dead animals

• Move by cilia on ventral side

Non-parasitic

Phylum Platyhelminthes can reproduce sexually and asexually

Sexually - hermaphroditic

asexually - separate into a head/tail end and regenerate

Phylum Platyhelminthes

Most are hermaphroditic

Mating can determine who looks after the eggs

ENERGY AND FOOD

Termatodes

Complex life cycles require an intermediate host before infecting the final host (usually a vertebrate)

Sexual and asexual

Ex: blood flukes

Intermediate host = snails

Final host = humans

Tapeworms

Adults live mostly in vertebrates (including humans)

Lacks a mouth and a gastrovascular cavity

Absorb nutrients released by digestion in their host’s intestine

-Absorption occurs across the tapeworm’s body surface

Scolex

“sucker” for attatchment to human intestinal lining

(Part of tapeworms)

Proglottids

Long “ribbon” units consist of thousands of fertilized eggs

• released from the posterior end of a tapeworm and leaves the host’s body in feces

Acquired by eating undercooked meat —> cysts within the meat develope into mature adults inside human intestines

(Part of tapeworms)

Phylum Syndermata

Rotifers (wheel-bearer)

Smaller than protists, but are still multicellular and have specialized organ systems

Crown of cilia that draws a vortex of water into the mouth

Trophi

Jaws grind up food

Rotifers

Rotifers exhibit some unusual forms of reproduction

Some species consist only of females that produce more females from unfertilized eggs, a type of asexual reproduction called parthenogenesis

Some rotifers can also reproduce sexually under certain conditions, such as high levels of crowding

Acanthocephalans

Sexually reproducing parasites in vert. (All of them)

• lack a complete digestive tract

• “Spiny-headed worms”

• Curved hooks on the anterior end

• Triploblastic

• They can manipulate the behavior of their intermediate hosts in ways that increase their chances of reaching their final hosts (generally vertebrates)

Part of Phylum Syndermata

Phylum Ectoprocta

Ectoproct - “outside anus.”

Common name = bryozoans (“moss animals”)

• Superficially resemble moss

Bilateral , lophophores, have a coelom

“Lamp shells”

Superficially resemble clams and hinged molluscs

All are marine

Bilateral

Lophophores

• Open the shell to let water flow through

Have a coelom

Part of Phylum Brachiopoda