Crustaceans Flashcards Preview

2nd Year: Animal Biodiversity > Crustaceans > Flashcards

Flashcards in Crustaceans Deck (38):
1

Crustaceans are the most diverse group of animals on Earth. True or false?

True.

2

How many extant species are there?

~68,000.

3

Within the arthropods which group are the crustaceans a sistergroup to, under both the pancrustacea and mandibulata hypothesis?

The hexapods.

4

Define Orsten fauna.

Fossilised crustaceans preserved in Orsten lagerstätten from Sweden.

5

Why are Orsten fauna good for looking at crustacean growth and evolution?

They are preserved in nodules at different growth phases

6

What are yicaris dianensis and wujicaris muelleri?

Some of the earliest fossilised crustaceans from the Cambrian

7

Where were yicaris dianensis and wujicaris muelleri found?

China.

8

Why is the term Eucrustacea sometimes used?

It refers to all extinct and extant forms of the crustacean but excludes the trilobites

9

Give 3 features of eucrustacea.

1. The body is split into 3 distinct segments: head, thorax and abdomen

2. The head and thorax are often joined in the cephalothorax which is often covered by a carapace.

3. Each body segment has paired appendages.

10

What is another name for the abdomen of crustaceans?

The pleon.

11

How many pairs of appendage does the head have?

3: the antennula and antenna (sensory) and the mandibles (crushing mouth parts)

12

How many segments/pairs of appendages does the thorax have?

There are 5 segments each with a pair of limbs, hence the term 'decapod'.

13

The abdomen often pairs pleopods. What are these?

Swimming legs.

14

Define the terms a) pereiopods and b) maxillipeds - these are found on the thoracic segments.

a) Walking legs
b) Feeding legs

15

Define carcinisation.

When a crab-like form evolves from a non-crab-like ancestor. The crab-like form has evolved convergently multiple times.

16

There are 6 major groups of crustacean. What are they?

1. Malacostraca
2. Branchiopods
3. Ostracods
4. Maxillopods
5. Remipedia
6. Cephalocarida

17

Which group is the most diverse?

Malacostraca.

18

What are stomatopods?

Mantis shrimps, members of the malacostraca.

19

What is characteristic about the abdomens of shrimps?

They often have limbs on, unique in crustacea.

20

There are 2 types of mantis shrimp, each with different limb forms. What are they?

a) spearing limbs
b) smashing limbs

21

Describe how the smashing limbs of mantis shrimps work.

With an acceleration of 10,000g the limb creates a cavitation bubble (vacuum) in the water. The combined blow from the limb and from the bubble generate a force of up to 47,000 times their body weight. Helps to smash open prey like molluscs.

22

What is a snapping mantis shrimp?

Shrimps with modified smashing arms: from a distance of 3-4mm a shrimp can shoot a cavitation bubble at a target, causing a snapping sound.

23

The bubbles from snapping mantis shrimps are louder than whale and dolphin song. True or false?

True!

24

Stomatopods have highly evolved eyes.

a) How many photoreceptors have they got in each eye?

b) How many fields of vision can they see in?

c) They need both eyes for depth perception. True or false?

a) 12: 8 for colour, 4 for UV

b) 3: colour, UV and polarised light

c) False: they can see depth with only one eye

25

There are 6 major groups of crustacean. What are they?

1. Malacostraca
2. Branchiopods
3. Ostracods
4. Maxillopoda
5. Remipedia
6. Cephalocarida

26

What are the only crustaceans to display eusociality?

Stomatopods.

27

Where do stomatopod colonies live?

Inside sponges.

28

Branchiopods are tadpole shrimps. They have evolved androdioecy. What is that?

Whereby individuals are only ever larger hermaphrodites or smaller males. This is to prevent a loss of genetic diversity by ensuring sexual reproduction.

29

The maxillopodans are highly segmented and often parasitic. Give 2 examples.

1. Branchiura or 'fish lice'

30

The maxillopodans are highly segmented and often parasitic. Give 2 examples.

1. Branchiura or 'fish lice'

2. Pentastomids have no segments or brain but live in the tracheal system of amphibians and reptiles.

31

The maxillopodans are highly segmented and often parasitic. Give 2 examples.

1. Branchiura or 'fish lice'
2. Pentastomids have no segments or brain but live in the tracheal system of amphibians and reptiles.

32

Give an example of a maxillopodan that is not parasitic.

The thecostracans or 'barnacles'.

33

Describe the body structure of a thecostracan.

Descended from shrimp-like ancestors, their heads are secured to a rock surface and the thorax has been lost. Some also argue the abdomen has been lost because abdominal gene-B is missing.

34

Give a similarity between the remipedes and cephalocarids.

They are both homonomously segmented, meaning all their segments are identical as opposed to the other crustaceans.

35

What is unique about the remipedes?

They are the only crustaceans to produce venom.

36

Describe the toxicity of remipede venom?

It has 12 known toxins in it, one of which causes anaphylactic shock, another causing spastic paralysis of the muscles.

37

Why is it thought that remipedes have developed venom?

As an adaptation to the dark, they live in submarine caves.

38

Differentiate between a venom and a poison.

Venom = a chemical that causes harm when injected or by infecting a wound

Poison = a chemical that causes harm when ingested