Animal Diversity Lab

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Source used:

• The Online Biology Book by Estrella Mountain Community College.

Introduction

The kingdom Animalia is characterized by multicellular organisms that are heterotrophic (obtaining energy through consuming other organisms as opposed to generating their own, like plants do with photosynthesis) and lack cell walls. They are motile (capable of movement) during at least one stage of their life cycle. They may also have skeletons for support, skin to prevent water loss, muscles for movement, brains and nervous systems for responding to stimuli in complex ways, and digestive systems; these characteristics are present in the most complex animals, but are absent or limited in others.

The predominant animal body plan consists of a tube, with one opening for food to enter the body and another for waste products to exit. Many animals are formed from three embryonic tissue layers in early development: the endoderm, the mesoderm, and the ectoderm. The endoderm layer produces the digestive and respiratory systems; the mesoderm layer produces the muscular, skeletal, integumentary (skin and hair), and reproductive systems; and the ectoderm produces the integumentary and nervous systems. However, more simple animals may lack some or all of these layers. In the marine realm, sponges lack all three tissue layers, while cnidarians lack the mesoderm layer. 

Animals can be classified by whether or not they possess a coelom, a fluid-filled body cavity completely lined by mesoderm-derived tissue. The animals lacking this tissue layer are acoelomates or, if they have a body cavity that has formed from a different tissue layer, they are pseudocoelomate. Coelomate animals are either protostomes or deuterostomes depending on what the first opening in the blastula becomes. If this opening develops into the mouth, the animal is a protostome. If the opening develops into the anus, the animal is a deuterostome. Vertebrates fall into this category.

In addition, animals are categorized by what planes of symmetry their bodies can be divided along to form mirror images. Asymmetrical animals (such as sponges) do not have an axis of symmetry. Radially symmetrical animals (such as corals and sea stars) have bodies that are organized about a central point and can be divided along multiple planes of symmetry. Bilaterally symmetrical animals have a single axis of symmetry and can only be divided into mirror images along one central plane. 

Activity: Observe and Describe Specimens

Explore the phyla that are typically seen in benthic (seafloor) ocean environments by observing and dissecting specimens according to the instructions below. Draw your observations and answer the questions on the provided worksheet (also linked here). Turn your worksheet in to your TA or instructor before the end of the lab.

The phylogenetic tree below displays the evolutionary relationships of animal phyla.  We will start our exploration of them with the phylum Porifera.

Figure 1. Phylogenetic tree for kingdom Animalia with phylum Porifera highlighted. Image credit of Jonathan R. Hendricks, licensed under a Creative Commons Attribution-NonCommercial ShareAlike 4.0 International License.

PORIFERA

Materials Needed

• Three species of sea sponge

• Bleach

• Eye droppers

• Dissecting scalpels or razor blades

• Light microscopes

Sea sponges belong to the phylum Porifera, described in this video. Sponges are asymmetrical animals that lack specialized tissues, consisting of cells arranged to form a sack-like body around a central cavity. They feed by filtering water through pores along the body into the central cavity and out the osculum, an opening at the top of the animal. Sponges can reproduce asexually through budding or sexually by releasing eggs and sperm into the central cavity to form a motile larvae. As adults, sponges are stationary. Sponges are differentiated based on the composition of their spicules, small pointed structures embedded in their tissue to provide support to the body and deter predation. In the lab footage, we will observe sponges in class Hexactinellida. Hexactinellids are commonly known as glass sponges because their spicules are made of silica–the primary ingredient of glass.

Figure 2. Several examples of Hexactinellida (glass sponges): A, Dictyaulus sp.; B, Farreidae; C, Regadrella sp. Images credit of NOAA Ocean Exploration, in the public domain.

Instructions

1. Obtain a sponge sample, a scalpel, and a dissecting tray. Record the name of your sponge on your worksheet. 

2. After observing your sponge with the naked eye, use your scalpel to take a thin slice from it. 

3. Place your sample under the dissecting scope at your lab bench and draw what you see.

Next, obtain a glass dish. Use an eyedropper to place enough bleach on top of the sample to entirely submerge it, and use your scalpel to break it up. Allow the bleach to dissolve the tissue in the sample for 5 minutes before using the light microscope to observe it. You should see the spicules; if you are unable to find them, allow the sample to sit for several more minutes before returning to it. Use the diagram below to determine what kind of spicules your sponge sample has before drawing what you see under the microscope.

Figure 3. Examples of sponge spicules; top labels correspond to number of axes, bottom labels to number of growth directions. Image credit of Jaleigh Q. Pier, licensed under a Creative Commons Attribution ShareAlike 4.0 International License.

CNIDARIA

Materials Needed

• Cnidarians (Aiptasia recommended)

• Glass Slides

• Glass Coverslips

• Light microscopes

• Petri dishes 

• Forceps 

• Dissecting scissors

The phylum Cnidaria includes animals that have radial or bilateral symmetry that develop from two tissue layers, the ectoderm and endoderm. They lack advanced organs or organ systems but possess a gastrovascular cavity, muscle fibers, and a nerve net. Though all species have planktonic larvae, adult cnidarians are formed along one of two body plans: sessile polyps whose gastrovascular cavities have upward-facing openings that are surrounded by tentacles, or motile medusas, with downward-facing mouth and tentacles. In some species, sessile polyp-type adults may produce motile medusa-type adults through budding.

The class Anthozoa is composed of sea anemones and corals. Anemones consist of a single polyp that is anchored to its substrate by a disc, while corals have numerous polyps that function as a single individual. Both corals and anemones are heterotrophic. Larger anemones consume small fish and arthropods while corals feed on smaller planktonic organisms. Some shallow-water corals have symbiotic relationships with dinoflagellate algae called zooxanthellae, which reside within their tissues. Algae receive protection and CO2 to use in the process of photosynthesis, and they provide the coral with the excess nutrients that they produce. 

The deep-water corals that we will observe are primarily from the order Alcyonacea and are also known as gorgonian or soft corals. Coral polyps cover skeletons consisting of calcium carbonate sclerites, which are alternated with soft proteins; the degree of hardness and rigidity of skeletons varies between species, but they are all flexible enough to bend in ocean currents without breaking. Larger colonies serve as habitats for a range of marine organisms, from other cnidarians like anemones or hydrozoans to arthropods and gastropods.

Figure 4. Several examples of Cnidarians: A, Keratoisidinae; B, jellyfish in water column; C, Kulamanamana haumeaae; D, Anthomastus sp. Images credit of NOAA Ocean Exploration, in the public domain.

Cnidarians are characterized by their possession of stinging cells called cnidocytes on their tentacles. The barb-like nematocysts inside cnidocytes are deployed when a hairlike projection experiences tactile stimulation, and they can be used for obtaining food or defense against predators.

Figure 5. A: Diagram showing the cnidocyte (a) prior to deployment and (b) with the nematocyst released. Image taken from the Biology 2e OpenStax textbook, licensed under Creative Commons Attribution 4.0 International (CC BY 4.0) License. B: Light microscope image of a discharged nematocyst. Image credit of Marc Perkins, licensed under Creative Commons Attribution NonCommercial 2.0 Generic (CC BY-NC 2.0) License.

Instructions

1. Obtain your cnidarian sample.

2. Record the name on your worksheet and observe its color and behavior. Remember that animal tissue is clear; what could be creating the color you see in your sample?

3. Use scissors and forceps to cut off one tentacle from the polyp. Polyps will retract their tentacles when touched, so this may be difficult. Ask your instructor for assistance if you need it. 

4. Place the tentacle on a glass slide and squash it with a glass cover slip, then use the light microscope to locate and observe the nematocysts. 

5. Draw what you see on your worksheet.

MOLLUSCA

Materials Needed

• Dissecting scope and/or hand lens if snails are small

• Beakers or petri dishes for placing snail in for observation

• Snails (can be marine or freshwater)

Phylum Mollusca consists of animals that possess a true coelom containing internal organs, contained in a region called the visceral mass and partially covered by a mantle. In some species, the mantle secretes a hardened calcium carbonate shell. The respiratory structures, typically gills, are located between the mantle and the visceral mass while the mouth is found on the muscular foot that is used for movement. Inside the mouth is a tongue-like organ covered with rows of teeth called a radula. The nervous system consists of neural ganglia and nerve cords, and the open circulatory system is characterized by a heart that pumps blood throughout the body before it returns by diffusion. Class Aplacophora consists of worm-like animals with no outer shell. Class Gastropoda consists of animals with asymmetrical bodies that are typically protected by a coiled shell.

Figure 6. Several examples of mollusks: A, gastropoda; B, Epimenia sp. on a coral; C, gastropoda and Aplacophora. Images credit of NOAA Ocean Exploration, in the public domain.

Instructions

1. Begin by watching this video about phylum mollusca. 

2. Obtain a living gastropod. Record the name on your worksheet. 

3. Observe the animal’s movement, appearance, and response to stimuli

4. Draw the snail in the space provided. Use the image below to label the anatomical structures that you can see.

Figure 7. Anatomy of a snail. Image taken from the Biology 2e OpenStax textbook, licensed under Creative Commons Attribution 4.0 International (CC BY 4.0) License.

ANNELIDA

Materials Needed

• Dissecting tray and dissecting kit

• Preserved earthworms

Phylum Annelida consists of segmented worms. They have a large coelom with internal organs. They have a closed circulatory system, with blood vessels carrying blood to the different body segments. Their nervous system has a brain, nerve cord, and neural ganglia, while the digestive system has a pharynx, stomach, intestine, and other organs. 

Class Polychaeta is composed of annelids with parapodia (paddle-like appendages) and setae (bristles to anchor the worm to a substrate). Class Clitellata consists of leeches with anterior and posterior suckers that suck blood and contain the anticoagulant hirudin in their saliva.

Figure 8. Several examples of annelids: A, Hirudinea feeding on a Coryphaenoides longicirrhus; B, Teuthidodrilus sp. Images credit of NOAA Ocean Exploration, in the public domain.

Instructions

1. Obtain an earthworm, dissecting tray, scalpel, and gloves. 

2. Record the name on your worksheet and draw its exterior appearance. 

3. Follow this link for instructions on how to dissect your worm. 

4. Draw and label your dissected specimen.

ARTHROPODA

Materials Needed

• Beakers

• Arthropods: some examples include hermit crabs (land or marine), isopods (or rolly polly bugs), shrimp (freshwater or marine), or any collected bugs from your region

Phylum Arthropoda, the largest phylum in the kingdom Animalia, consists of animals with segmented bodies bearing pairs of jointed appendages and nervous systems containing a brain, nerve cord, and sensory organs. The exoskeleton is periodically shed and replaced in a process called ecdysis, which allows the body to grow. Class Malacostraca contains shrimps and crabs, while class Pycnogonida contains sea spiders characterized by long legs and small bodies.

Figure 9. Several examples of arthropods: A, Lebbeus sp.; B, Paralomis sp.; C, Uryoptochus sp.; D, Poecilasmatidae; E, Homeryon asper; F, Munidopsis sp. Images credit of NOAA Ocean Exploration, in the public domain.

Instructions

1. Obtain a living arthropod. 

2. Record its name on your worksheet and draw it in the provided space. 

3. Observe its appearance and movements. How does it move? How does it obtain energy?

   
   

ECHINODERMATA

Materials Needed

• Beakers or petri dishes

• At least one example echinoderm, options include sea stars and sea urchins

Phylum Echinodermata consists of marine animals with a bilaterally symmetrical larval phase and radial symmetry as adults. They have a water vascular system for movement, a calcareous endoskeleton, and a nervous system with a nerve ring and five radial nerves that run into the arms or along the length of the body. Class Crinoidea contains stalked sea lilies and motile feather stars, which have branched arms used for filter feeding. Class Holothuroidea consists of sea cucumbers with long bodies and feeding tentacles near their mouths. Class Echinoidea consists of sea urchins with long spikes used for movement and defense. Class Ophiuroidea contains brittle stars, which possess five, or a multiple of five, arms radiating out from a central disc containing their internal organs. Class Asteroidea consists of sea stars, which differ from brittle stars in that their internal organs extend into the arms.

Figure 10. Several examples of echinoderms: A, Euryalidae; B, stalked Crinoidea (foreground) and Brisingidae (further back); C, Benthothuria sp.; D, Hippasteria muscipula feeding on Keratoisidinae. Images credit of NOAA Ocean Exploration, in the public domain.

Instructions

1. Obtain an echinoderm. 

2. Record its name on your worksheet and, while observing its appearance and reaction to stimuli, draw it in the space provided. How does it move? How do you think it obtains energy? 

CHORDATA

Materials Needed

• Fish tank for observation (could be marine or freshwater), with limited resources consider obtaining a betta fish

Phylum Chordata is characterized by the possession of a notochord (a dorsal hollow nerve cord), pharyngeal slits and a post-anal tail, all of which are present in the embryonic form of an animal. Subphylum Vertebrata consists of chordates with backbones. Class Actinopterygii consists of ray-finned fish, which have bones in their fins to hold them out and away from the body. They also have scales, gills, and a gas-filled swim bladder to help change and maintain their depth in the water column.

Figure 11. Several examples of chordates: A, Setarches sp.; B, Aldrovandia affinis; C, Kumba sp.; D, Chaunacops coloratus. Images credit of NOAA’s Office of Ocean Exploration and Research, in the public domain.

Instructions

1. Go to one of the aquariums in the lab. Observe one of the chordates in the tank. 

2. Describe its appearance and behavior

   1. Movement: How does it move? How frequently does it move, and does it seem to prefer being out in the open or hiding? 

   2. Diet: What do you think it eats? Do you think it eats organisms from the benthic (seafloor) or pelagic (open water) environment, and why do you think this? 

3. Draw the chordate, provide its name if you can, and answer the questions on the worksheet.

Before leaving lab, turn in your worksheet to your instructor.

Assignment

1. Watch the coral anatomy portion (10:30 to 14:30) of the documentary Chasing Coral, which can be found on Netflix. In addition, write a 500-word reflection on the assigned segment; if you watch the whole film, include information from the entirety of it. Inform your instructor if you do not have access to Netflix.

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