1

LSM3254 Ecology of Aquatic Environments

Practical 1: Aquatic Diversity

23 August 2011

PROGRAMME

This schedule lists key material being demonstrated across eight (8) stations during this

lab session. While some aspects of this practical complement the lecture topics, it can also

be treated as a standalone lesson.

The stations are organised on various themes related to diversity, ecology, and/or form

and function, and may feature exclusively freshwater or marine organisms or a mixture of

both. The theme of each station will not be revealed initially. Instead, you should try to

deduce what the theme is based on what material is on display, and what is being

discussed at the station.

Visit stations to view various representatives of selected groups of organisms. Discuss the

distinguishing features, morphological adaptations, and ecology of the organisms, and the

rationale for the station groupings.

At each station, your TAs will brief you on salient points of the demonstrated material

only. Following that, you should examine the material yourselves, take notes, and clarify

any doubts you might have with your TAs.

For Stations 2-8, there will be a few key specimens (highlighted in bold and marked

with an asterisk in this list) that will be emphasised. Other specimens should

nevertheless be examined to broaden your perspective and general knowledge.

The practical session will include a tutorial exercise in the construction of dichotomous

keys for identification.

OBJECTIVES

To observe and learn through a survey of representative specimens about:

o diversity of aquatic organisms and their distinguishing features

o selected ecological themes

o selected functional themes

Thus for all the stations, keep the following in mind:

o the key distinguishing characteristics of major groups/subgroups

o the theme of each station and how the demonstrated animals reflect/are associated

with that theme

o how the demonstrated materials at each station are similar or different from one

another with respect to the ecological or functional theme of the station

To learn how to use and construct dichotomous keys to identify organisms

2

BACKGROUND

Aquatic biodiversity is a major component of global biodiversity. The diversity of phyla in

marine and freshwater environments outnumbers that of terrestrial environments by more

than three to one (47 phyla versus 14 phyla). At the next taxonomic level, the number of

classes of aquatic organisms is more than four times greater than the number of terrestrial

organism classes. Within the aquatic realm, the respective diversities of marine and

freshwater environments reflect the overwhelming size and scale of marine environments

compared to freshwater environments. For example, there are more than twice as many

marine phyla and classes as there are freshwater equivalents.

Aquatic animals can therefore illustrate many of the same ecological and functional patterns

and processes that are seen on land. Can you list some examples below?

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

At the same time, however, aquatic animal diversity also reflects in morphological forms,

ecological processes, and life histories, the uniqueness of the aquatic environment—

especially the watery medium, compared to the terrestrial environment and the medium of

air. Can you list some examples below?

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

Dichotomous keys

Keys are important tools for identifying organisms. The most common type of key is the

dichotomous key. A dichotomous key is an analytical tool consisting of a series of paired

contrasting statements requiring the user to make comparisons and decisions based on these

statements in relation to the material to be identified. Some keys are Indented Keys while

others are Bracketed Keys. Some keys use more than two contrasting statements (e.g.,

trichotomous key using triplets of statements instead of pairs). This is less ideal, but why do

you think this is so? Can you think of circumstances that might necessitate the use of

trichotomous keys?

When using a key to identify an organism, bear in mind:

1) Determine relevance

2) Realise imperfections can and do exist in published keys

3) Familiarise yourself with the terminology

4) Read all leads at each stage or couplet of the key

5) Where possible, examine more than one feature in more than one specimen before

making a decision

6) ―Back-track‖ when lost

7) Verify your identification

3

STATIONS

STATION 1: Using a dichotomous key

- At this station you will attempt to identify one or more crustacean specimens using the

following dichotomous key in conjunction with the provided terminology diagrams.

- Your TA will guide you in the use of the key, interpretation of the terminology, and

handling of the specimens. Note: When lifting and holding any specimen, please pick

up the whole specimen with your hand or lift it up by the carapace (body) and DO

NOT pick up any specimen by its appendages (antennae, pincers, legs, etc.) or soft or

mobile parts (abdomen).

1. Antennae long, well developed ………........................................................................................... 2

– Antennae reduced ............................................................................................................................. 4

2. Rostrum present. Abdomen laterally flattened ................................................................... Penaeus

– Rostrum absent. Abdomen cylindrical or dorsoventrally flattened ……….………........................ 3

3. Three pairs walking legs present. Abdomen reduced, dorsoventrally flattened, folded under

carapace ……………..................................................................................................... Petrolisthes

– Two pairs walking legs present. Abdomen elongate, cylindrical ………......................... Coenobita

4. Last two pairs of walking legs ending in pincers. Carapace covered with fine felt ..... Lauridromia

– Last two pairs of walking legs not ending in pincers. Carapace not covered with fine felt …….... 5

5. Last pair of walking legs paddle-like. Carapace with single elongate lateral spine on either side

.......................................................................................................................................................... 6

– Last pair of walking legs undifferentiated. Carapace without single elongate lateral spine on either

side ......................................................................................................................................................... 7

6. Carapace circular in shape. All walking legs paddle-like ................................................... Ashtoret

– Carapace transversely hexagonal in shape. Only last pair of walking legs paddle-like ..... Portunus

7. Carapace dome-shaped. Posterior margin lined with teeth ................................................. Calappa

– Carapace not dome-shaped. Posterior margin not lined with teeth ………...................................... 8

8. Carapace as broad as long (appearing square-shaped). Eyes located at anterolateral corners of

carapace .......................................................................................................................... Episesarma

– Carapace distinctly broader than long. Eyes located at front of carapace ....................................... 9

9. Abdomen with five movable sections ........................................................................................... 10

– Abdomen with seven movable sections ........................................................................................ 11

10. Fingertips of pincers spatulate. Anterolateral margin of carapace dentate (with teeth) .......... Etisus

– Fingertips of pincers pointed. Anterolateral margin entire (smooth) ……………….......... Atergatis

11. Carapace and upper and outer surface of pincers smooth. Anterolateral margin of carapace with

low, poorly-developed teeth. Moveable finger of pincer with modified tooth (―can opener‖) at the

base ........................................................................................................................................... Ozius

– Carapace and upper and outer surface of pincers granulate. Anterolateral margin of carapace with

sharp, well-developed teeth. Movable finger of pincer without modified tooth …...... Myomenippe

4

STATION 2: Theme:

___________________________________________________________________________

___________________________________________________________________________

Representative taxa

- Anemone

- Barnacles

- Coral*

- Crab

- Cuttlefish

- Feather star

- Giant clam

- Sea snake*

- Sea star

- Sea urchin

- Shark

- Sponge*

- Stonefish

- Top shell

STATION 3: Theme:

___________________________________________________________________________

___________________________________________________________________________

Representative taxa

- Baler shell (marine gastropod)*

- Horseshoe crab

- Sea star

- Sea Slug

- Jellyfish

- Coral*

- Big head carp*

- Butterflyfish

- Frog

- Puffer fish

- Scallop

- Sea snake

- Stingray*

- Chinese softshell turtle

- Squid

5

STATION 4: Theme:

___________________________________________________________________________

___________________________________________________________________________

Representative taxa

- Asian Toad

- Flower crab

- Filefish

- Giant clam*

- Octopus*

- Porcupine fish*

- Stonefish

- Sea snake

- Sea turtle

STATION 5: Theme:

___________________________________________________________________________

___________________________________________________________________________

Representative taxa

- Anemone fish

- Snapping shrimp

- Remora

- Sea cucumber*

- Anglerfish

- Lamprey*

- Mudskipper*

STATION 6:

___________________________________________________________________________

___________________________________________________________________________

Representative taxa

- Alligator gar*

- American bullfrog

- Arowana* - Cane toad

- Chinese softshell turtle*

- Tilapia*

6

STATION 7: Theme:

___________________________________________________________________________

___________________________________________________________________________

Representative taxa

- Giant clams*

- Anemones

- Hermatypic corals*

- Zoanthids

- Crustose coralline algae*

- Calcareous algae

- Sea grapes

- Sargassum*

- Sea grasses*

- Freshwater floating macrophytes*

- Freshwater submerged macrophytes

- Freshwater emergent macrophytes

STATION 8: Theme:

___________________________________________________________________________

___________________________________________________________________________

Representative taxa

- Freshwater cyanobacteria*, diatoms, and chlorophytes

- Marine diatoms and dinoflagellates

- Harmful freshwater cyanobacteria

- Harmful dinoflagellates*

- Freshwater cladocerans*, copepods*, rotiferans (rotifers)

- Marine holo________: copepods, amphipods, ghost shrimp*, arrow worms*

- Marine meso________: various larvae

o Hydroids

o Jellyfish or medusae

o Crab zoeae* (s. zoea)

o Crab megalopae (s. megalopa)

o Sea star