Lab Activity 11.3
Planktonic Animals

  Directions

Study the instructional material below. Be sure to click on each of the photographs for an enlarged view in a separate window. The larger version is necessary to complete the assignment. It opens in a separate window which can be resized by grabbing the bottom right corner and dragging it. It can also be moved by grabbing the top heading bar and dragging it. Be sure to close the extra window by using the X in IBM, or the close box in MAC when you are finished using them.

  Introduction


A single tow of a plankton net captures an astounding diversity and abundance of zooplankton. They vary in size from giagantic jellyfish to microscopic copepods. Zooplankton have an important position in many marine food webs. Many of them eat the tiny phytoplankton producers and are eaten by larger animals. In this way they pass on the sunlight energy captured by phytoplankton. In this lab activity you will introduce yourself to the world of zooplankton and some of the broad categories marine biologists use to make sense out of this dazzling array of animals.

Top  Instruction

Examine all of the photographs of the zooplankton by clicking each of the thumbnail pictures. Study the information that goes with each photograph and complete the observations by answering the questions in your notebook.

Be sure to write about what you are learning in the lab section of your notebook. You will be expected to answer questions about the lab activity during the lab self test and lab quiz. It helps to have your text and coloring books open beside you for support.

 
Supporting Information
Refer to the Assigned Readings Below:
Marine Biology Textbook Chapter 15, pages 328 to 336
Marine Biology Coloring Book Plates 24, 35, 78 to 81, 83 and 84
 

Holoplankton are species of invertebrates that spend their entire lives from hatching until death as plankton.

Some species of invertebrates have their embryonic development in the plankton and become planktonic adults. These species spend their entire lives in the plankton. They are the most abundant type of zooplankton.

 

Holoplanktonic Crustacea

 

Copepods are tiny holoplanktonic crustaceans. Copepods make up over 90% of the zooplankton by number and are the most abundant marine animals.

Observe the photograph of a copepod.

Observations:
  1. Describe the anatomy of the copepod.
  2. Describe the features that help it stay afloat and swim.

 

Holoplanktonic Crustacean Larvae

 

Nauplii are the first planktonic, larval stages in the development of many crustacea, including copepods. They hatch from eggs and begin to feed and grow immediately. They grow and develop into copepodites which ultimately develop into adult copepods.
Experimental Set Up: 
  1. We photographed copepod nauplii, copepodites, and adult copepods from a zooplankton sample taken off the coast of Southern California.
Observe the photographs of nauplii, copepodites and adult copepods.
 Nauplii  Copepodites  Adult Copepods
     
     

Observations:
  1. How do the nauplii differ from the copepodites and adult copepods you just observed?

 

Holoplanktonic Copepod Diversity

 

Copepods are diverse as well as abundant. A typical zooplankton sample will contain several different species.
Experimental Set Up: 
  1. We photographed several species of adult copepods from a zooplankton sample taken off the coast of Southern California.
Observe the photographs of adult copepod species.
Cyclops  
 Calanus  
 Eurytemora  

Observations:
  1. How do the adult copepods you just observed differ? How are they similar?

 

Holoplanktonic Predator

 

Arrow worms are holoplanktonic invertebrates which feed on copepods. They are fast swimmers and can easily capture their prey.
Experimental Set Up: 
  1. We obtained a preserved specimen of an arrow worm, placed it in a watchglass filled with water, and photographed it using a dissecting microscope.
Observe the photographs of the arrow worm.
 Whole Worm  Anterior End Head 
 

Observations:
  1. Describe the special structures near its mouth that are used to impale copepods.

 

Gelatinous Holoplankton

 

There are several types of holoplanktonic species whose bodies are jelly-like. They are called gelatinous zooplankton. These forms include medusae, siphonophores, salps and larvaceans.
Experimental Set Up: 
  1. We photographed several species of gelatinous zooplankton from a zooplankton sample taken off the coast of Southern California.
Observe the photographs of gelatinous zooplankton species.
Medusae    
 Siphonophores    
 Salps    
 Larvaceans    

Observations:
  1. Describe the differences between medusae, siphonophores, salps, and larvaceans.

 

Additional Gelatinous Plankton

 

Gelatinous zooplankton include medusae, ctenophores and siphonophores.
Experimental Set Up: 
  1. We photographed several additional species of gelatinous zooplankton obtained from various locations.
Observe the photographs of gelatinous zooplankton.
Medusae        
Ctenophores        
Siphonophores        

Observations:
  1. Describe the features that gelatinous zooplankton all share in common.

 

Meroplankton are the planktonic larvae of nektonic or benthic species.

Some species of invertebrates spend their adult lives on or in the benthos but their embryos develop in the plankton. Some species of fishes spend their adult lives as nekton but their eggs and embryos develop in the plankton. These planktonic larvae act as a dispersal stage being distributed by currents to new sites where they settle to the bottom and grow into adults.

Meroplanktonic Crustacean Nauplii

 

Barnacles live cemented to hard substrates as adults but their larval stages are meroplanktonic.

Experimental Set Up: 
  1. We obtained a prepared slide of a barnacle nauplius and photographed it at high power under a compound microscope.
   Observe the photographs of the nauplii.

Observations:
  1. How does a nauplius larvae differ from the adult?

 

Meroplanktonic Echinoderm Larvae

 

Starfish live on the benthos as adults but their embryos develop in the plankton. The embryo passes through two distinct stages before its final metamorphosis. The bipinnaria larva grows into a brachiolaria larva which is ideally suited to life in the plankton. These meroplanktonic larvae undergo dramatic changes as they metamorphose.
Experimental Set Up: 
  1. We obtained prepared slides of bipinnaria and brachiolaria larvae. We photographed both larval forms at high power under a compound microscope.
Observe the photograph of the bipinnaria larva.
Observe the photograph of the brachiolaria larva.

Observations:
  1. What does the bipinnaria have that the brachiolaria does not have?
  2. How does this feature benefit the bipinnaria for its temporary life in the plankton?

 

Meroplanktonic Larvae

 

Many meroplanktonic larvae look very different from the adult forms they develop into. Many were misidentified by marine biologists who described them as different species. These mistakes were corrected once developmental sequences were clarified.
Experimental Set Up: 
  1. We photographed several different meroplanktonic larvae from a zooplankton sample taken off the coast of Southern California.
Observe the photographs of the meroplanktonic larvae.
 Type of Larva Form  Photograph  Adult Form
 Veliger   1.
 Trochophore   2.
Zoea    3.
Bipinnaria  4.
Brachiolaria  5.
 Nauplius 6.
Fry    7.

Observations:  
  1. Use your books to help you identify the adult forms that produce the meroplanktonic larvae in the photographs above.
  2. You can print out this chart and add the names of the adults or make a similar chart in your notebook.

 

Demersal plankton are species that live in the sea bottom during the day but rise up into the plankton at night.

Demersal species are temporary members of the plankton and are taken by plankton nets in shallow waters throughout the night.

 

Demersal Crustacea

 
Amphipods are crustaceans which may be planktonic or benthic. Some species are demersal plankton.

Observe the photograph of an amphipod.

Observations:

  1. Describe the features of the amphipod that make it capable of living temporarily in the plankton.
  2. Describe the features of the amphipod that make it capable of living in the benthos.

Lab Activity 11.4 Zooplankton Identification