Biology Lab 12 Biology lab | Lab Reports Chemistry

synapomorphies include a

complete

digestive

system

(runs

from

mouth

to

anus),

a double ventral

nerve

chord,

and

excretory

organs

called

the

Maphighian

tubes.

Sexes

are

separate:

arthropods

copulate

and

have

internal

fertilization.

Most

arthropods

care

for

the

eggs

in

some

way,

either

by

laying

eggs

with

protective

shells

in

or

on

a

food

source or

by

carrying

them

around

on

their

bodies

until

the

eggs

hatch.

Females

carrying

eggs

are

called

gravid

females.

Larvae

are

often

very different

from

adults

and

undergo

metamorphosis

in

a short

period

of

time.

ACTIVITY

1:

Arthropod Dissection

In

this

laboratory,

you

will

be

working

in

groups

of

two

on

the

dissection of

the

organism assigned

to

you

by

the

professor.

You

will

be

responsible

for identifying

the

external

and

internal features of your

organism

using

the

Photographic

Atlas

and

other

resources

as

provided

by

your instructor.

(NOTE:

Don't forget

to

check

out

the

other specimens

that

are

available

at

the

rear of

the

lab.)

Exercise

1:

Anatomy

of Crayfisb

As

a

member

of

the

Class

Crustacea,

the

crayfish

shares synapomorphies with other crustaceans.

This

includes

jointed,

paired

,

and

biramous

appendages,

two

pairs

of antennae,

and

three body

regions

(the

head,

thorax,

and

abdomen).

Crayfish

are

known

to

be

scavengers, but they

also

prey

ion

other invertebrates. The

mouth

is

surrounded

by

appendages modified for feeding,

and

there is a

well-developed digestive

tract.

Dorsal,

anterior,

and

posterior arteries carry hemolymph (blood plus

lymph)

to tissue spaces (hemocoel)

and

sinuses.

In

contrast

to

vertebrates, there is a ventral solid

nerve

cord.

Crayfish

are

adapted

to

an

aquatic existence.

External

Anatomy

148

1.

Obtain a preserved crayfish,

and

place

it

in

a dissecting

pan

.

You

will draw

the

exterior

and

interior of

the

crayfish

in

the

boxes

following

the

dissection instructions. Make sure

to

label

the balded structures

on

your drawings

as

you

go

though the dissection.

2. Identify

the

chitinous exoskeleton.

3.

Arthropods

are

distinguished

by

metameres (repeating body segments) that fuse

to

form

different body regions (tagmata;

tagma

sigular). There

are

two tagmata

in

the crayfish.

The

first

is

the

cephalothorax

(fusion of the

head

and

the

thorax),

which

is

covered

by

a

carapace.

The second

is

the

abdomen,

which consists of several metameres that go

all

the

way

down

to

the

tail.

Q:

Is

each

region

specialized for

its

function? -~

-+r

e..:

~5

___________

_

Q:

Which body

region

of the crayfish

is

most obviously segmented?

B

rvleN\e

~

4.

Find

the

antennae,

which project

from

the head. Crustaceans also contain a secondary

set of smaller antennae

(antennule).

At the base of

each

antenna, locate a small,

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ACTIVITY1:Arthropod Dissection

organism using the Photographic Atlasandother resourcesasprovided by your instructor.^ (NOTE:

Exercise1:Anatomy of Crayfisb

External Anatomy

2. Identify the chitinous exoskeleton.

The firstisthe cephalothorax (fusion of the^ head^ and^ the^ thorax),^ which^ is^ covered^ by

a carapace. The second is the abdomen, which consists of several metameres that go

4. Find the antennae, which project from the head. Crustaceans also contain a secondary

set of smaller antennae (antennule). At the base of each^ antenna, locate a small,

Identifythe three tagmata: head,^ thorax,^ and^ abdomen.

prothorax , themiddle^ rnesothorax,^ and^ the^ hind^ rnetathorax^.^ Identifythefirst pair of

straight, leathery^ forewings^ attachedto^ themesothorax^.^ Finally^ ,^ locate^ thethird pair of

legs and theinner,^ membranous^ hind^ wings^ attachedto^ themetathorax.^ Each^ leg

organs ofthe head.Identifythe^ antennae^ (apair^ oflong,jointed^ feelers),^ the^ compound

eyes, and the dot-like simple^ eyes^ ( ocelli)^.

Remove the mouthparts {palp)^ by^ grasping^ them^ with^ forceps^ and^ pulling^ them^ out.

Identify the tympana (singular,^ tympanum)^ ,^ one^ on^ each^ side^ of^ the^ first^ abdominal

Identify the internal structures of the grasshopper.

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