Animal Diversity Exam 3 Part I: Non-arthropod Ecdysozoans

What 6 phyla are classified under Ecdysozoa (that we need to know)?

1. Nematoda — nematodes

2. Nematomorpha — horsehair worms

3. Tardigrada — tardigrades

4. Onychophora — velvet worms

5. Arthropoda — arthropods

Ecdysozoans have ___ germ layers, making them ___.

3; triploblastic

Are ecdysozoans protostomes or deuterostomes?

Protostomes

Are ecdysozoans shizocoelous or enterocoelous?

Shizocoelous

Do ecdysozoan embryos exhibit radial cleavage or spiral cleavage?

Radial cleavage

***Are ecdysozoan embryos considered mosaic or regulative?

???

What type of symmetry do ecdysozoans have?

Bilateral

What is the main trait that sets apart Ecdysozoa from other taxa?

Ecdysozoans have a multilayered cuticle that goes through periods of ecdysis (shedding)

Nematodes are in phylum ____.

Nematoda

What is the body cavity of a nematode?

Pseudocoelom

Are nematodes segmented (do they exhibit metamerism)?

No; unsegmented

What maintains the cylindrical body shape of a nematode?

Hydrostatic pressure

The digestive tract of nematodes is ____.

complete

The exretory organ of nematodes is the ____.

protonephridia

Describe the protonephridia.

A pair of excretory ducts extending along the lateral margins of the body.

Describe the nervous system of a nematode.

Cerebral/anterior ganglia present with two nerve cords (dorsal and ventral) extending from the anterior ganglia throughout the body

Describe the circulatory system of a nematode.

Nematodes do not have a circulatory system.

Describe the respiratory system of a nematode.

Nematodes do not have a respiratory system (through diffusion)

What type of muscles do nematodes have?

longitudinal

T/F: nematodes have a tough, sclerotized cuticle.

False; nematodes have a soft, unsclerotized cuticle.

T/F: nematodes have a cellular epidermis called a hypodermis beneath their non-living cuticle.

False; nematodes do have a hypodermis, but it is syncytial, not cellular.

What primarily makes up the cuticle of a nematode?

Collagen fibers

(Reproduction) Nematodes are mostly ___ with ___ fertilization.

dioecious; internal

Describe the locomotion of nematodes.

Rely on hydrostatic pressure from fluid in the pseudocoel to move (no motile cilia or flagella). When longitudinal muscles contract, fluid pushes against the opposite side of the body, causing the body to move in waves.

Some nematodes exhibit ___ (special reproduction type) and ___ (genetic condition).

Parthenogenesis; haplodiploidy

Nematodes are sexually dimorphic. What sets apart the males from the females?

Males are smaller with a hooked tail/spicule.

What about nematodes may cause difficulties when reproducing/copulating?

The high hydrostatic pressure in the pseudocoel.

Describe the process of nematode copulation.

The male opens the female’s genital pore with his spicule to insert ameboid sperm.

How many molts do nematodes go through during development?

Four (L1 > L2 > L3 > L4 > adult)

What habitat(s) do free living nematodes live in?

Freshwater, marine, and soil habitats

What is the diet of free living nematodes?

Many detritivores/decomposers, some predators

Caenorhabditis elegans is a species of free-living nematodes used for what?

Used in genetic models for gene cancellation

What is the common name for the free-living nematode Turbatrix aceti?

Vinegar eel

What is the most abundant animal (in terms of # of individuals)?

Parasitic nematodes

Eutely:

Genetic condition where a species has a fixed number of cells; exhibited in nematodes

In what situation might you contract intestinal roundworms, Ascaris lumbricoides?

In places where human fecal matter may be accidentally ingested (ex. areas of poor hygeine or where human feces are used in fertilizer)

* Describe the life cycle of Ascaris lubricoides.

Condensed:

Feces >ingested> small intestine >penetrates intestinal wall> veins > heart > alveoli > bronchial tubes > esophagus >cough,swallow> returns to small intestine, matures into adult and sexually reproduces

List:

1. Adults sexually reproduce in intestine; eggs are shed through feces

2. Eggs are ingested by a human

3. Eggs reach the small intestine, where the juveniles hatch out

4. Juveniles penetrate small intestine and get into veins

5. Juveniles travel through the heart into the lungs

6. Juveniles penetrate the alveoli, go up bronchial tubes to reach esophagus

7. Host coughs due to irritation, which leads to a swallow response; response brings nematode back to intestine, where it matures

Name 3 hypotheses as to why intestinal roundworms (Ascaris lumbricoides) travel to the esophagus and back as juveniles.

1. Avoid immune response

2. Allows for larger growth = higher fecundity = higher fitness

3. Behavior is vestigial, inherited from common anscestor

What are the complications that may come from having intestinal roundworms (Ascaris lumbricoides)?

Intestinal blockage in high numbers, can cause colic in horses

Necatur americanus and Ancylostoma duodenale are examples of what?

Hookworms

T/F: Hookworms are “sloppy feeders” and cause a lot of intestinal bleeding and blood loss.

True

T/F: Intestinal roundworms are “sloppy feeders” and cause a lot of intestinal bleeding and blood loss.

False; they only cause damage in high numbers and do not feed on blood.

* Describe the life cycle of a hookworm.

1. Hatch and develop as juviniles in environment, molting twice (L1 > L2 > L3)

2. L3 is the infective stage; penetrates the foot of a human walking across infected soil barefoot

3. Same migration pathway as Ascaris; intestine → vascular → lungs → esophagus → cough, swallow → intestine → mature and lay eggs

What are the health complications caused by hookworms?

Can cause developmental issues, especially in children (stunted growth, low energy, impared brain function)

Horsehair worms belong to what phylum?

Nematomorpha

Are horsehair worms segmented?

No

Horsehair worms need to mate in ___.

Water

Horsehair worms are parasitoids on ___.

Arthropods

What is a parasitoid?

An organism that has a parasitic larval stage and a free-living adult stage

Are horsehair worms monoecious or dioecious?

Dioecious

What unique behavior of horsehair worms get them from their arthropod host to the water where they can mate?

They can take control of their host and drive it towards water, often at the expense of the host’s life.

What habitat(s) do adult horsehair worms live in?

Marine, freshwater, and terrestrial

What habitat(s) do velvet worms live in?

Tropical, subtropical, and rainforests with a few marine species

Velvet worms belong to phylum ___.

Onychophora

What do velvet worms eat?

Insects, snails, and other smaller worms

What do velvet worms use to hunt that make them such good predators?

They use slime glands that secrete paralyzing toxins, which immobilize prey

What secretes the paralyzing toxins used by velvet worms to hunt?

Slime glands

What is unique about how velvet worms molt?

They molt in patches instead of all at once

T/F: velvet worms have a soft, unsclerotized cuticle. Because of this, they rely on hydrostatic pressure to maintain their shape.

True

T/F: velvet worms have am open circulatory system.

True; they have a hemocoel.

Are velvet worms mostly monoecious or dioecious?

Dioecious

The respiratory system of velvet worms resembles that of what other phylum?

Arthropoda (tube/tracheal system)

Tardigrades belong to phylum ___.

Tardigrada

The most important feature of tardigrade habitat is ___.

Moisture

Where do terrestrial tardigrades live?

In the water films on lichens and mosses

What do tardigrades eat?

Plant cells, nematodes, rotifers, and other small invertebrates

Describe the mouthparts of a tardigrade.

Have stylets around the mouth and a straw-like pharynx to “pierce and suck”

T/F: tardigrades don’t have a hemocoel.

False; tardigrades do have a hemocoel.

What is cryptobiosis and to what taxa does it apply?

A state of inactivity an organism goes into to withstand extreme temperatures, dessication, and low oxygen levels; tardigrades

What animal is the only animal known to survive exposure to the vacuum of outer space? What is the condition that allows this outstanding feat?

Tardigrades; cryptobiosis