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Identifying internal structures of dissected fish

Identifying internal structures of dissected fish


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Note : Images displayed below might be disturbing to some people.

I have dissected a fish for the first time ! I have some idea of what some of the structures might be but I am not sure and so would like your help.

1.Here is the fish I dissected. Are the white structures (towards the dorsal surface) muscles ? They are beautifully arranged.

2.I want to know what the yellow coloured structure (towards the ventral side) is. I guess it's the intestine. It looks "noodly". Here is a close up.

3.I have pointed at two different parts in the following images. I want to know whether they are part of the same structure - ie swim bladder or whether they are two different structures altogether. When I poked one of the parts the other part increased in size ,so I guess it's one structure but I just wanna make sure.


Since I can't actually look at and handle the yellow structures, it is difficult for me to provide any information on them.

As far as the white structures you mention on the first picture, I believe those are most likely muscles. As for your third question. That does appear to be all one structure; and yes, going on that assumption, the entire structure would be the swim bladder.


Dissection and Structures of Different Types of Fishes | Zoology

Cut a small piece of skin from the dorsal surface of a shark (Scoliodon). Put it in a hard glass test tube containing 5 to 10% KOH solution. Boil with constant stirring till the skin dissolves. Pour the contents of the test tube in a large watch glass. Allow to cool. The scales settle at the bottom. Decant the fluid. Repeat decantation with water till the last trace of KOH is removed.

Pipette a drop of water with the scales and put it on a slide. Remove the water with a piece of blotting paper and mount in glycerine. Staining, if required should be done in a small watch glass. Mount following routine procedure.

i. The scale has a base and a body.

ii. The basal plate is somewhat diamond shaped with a pulp cavity on the ventral sur­face, at the centre.

iii. The proximal end of the body attached to the basal plate is narrow. It widens distally.

iv. A few spines are present in the body which project a little beyond the distal margin.

2. Cycloid and Ctenoid Scales of Fishes:

These scales are present in teleosts or bony fishes.

Remove a few cycloid scales from a carp or a few ctenoid scales from a koi (Anabas) fish. Put them in a watch glass containing 10% KOH solution. Stir slowly with a needle till the covering epithelium dissolves. Wash thoroughly with water to remove the last trace of KOH. Make a temporary or stained permanent prepa­ration, as required.

i. A thin, nearly rectangular plate of bone with a semicircular free border.

ii. Concentric rings representing annual growth present.

The free end bears nume­rous short, bony spines.

3. Ampulla of Lorenzini (Dog Fish):

Ampullae of Lorenzini are identified by the large number of pores, arranged in groups, on the dorsal surface of the snout and the sides of the head of a shark (Scoliodon). On pressing the region a sticky fluid oozes out through the pores.

Cut a portion of the skin with underlying tissue from the dorsal surface of the head or snout with a group of such pores. Put it on a slide with a small amount of water. Ventrally, the ampulla is connected with fine nerves. Identify the ampulla in the tissue. Isolate it from the surrounding tissue with the help of two needles. Wash with water, stain with borax carmine in a watch glass, dehydrate, clear and mount.

i. A tubule with an opening at one end.

ii. The ampullary sac attached to the other end of the tubule.

iii. The sac is with eight radially arranged chambers around a central axis.

iv. The sac is connected with fine nerves.

4. Accessory Respiratory Organ of Magur Fish:

Clarias sp. (Magur fish):

The accessory organs are two, one in each branchial chamber.

Clarias can be killed by any of the following methods:

i. By asphyxiation with chloroform.

ii. Striking the head with a hard object.

iii. Putting the fish in warm water. The method is unsatisfactory.

Fix the specimen on a dissecting tray in a lateral position with the help of large pins. Cut the operculum with a pair of stout scissors along the border of the branchial chamber, keeping the pointed arm outside. The branchial chamber, except the region occupied by the gills is enclosed in a highly vascularized membrane. Cut the membrane in the form of a cross (+), turn the flaps and pin those down. The arborescent organ is exposed.

It consists of two components:

i. A highly branched, vascularised arbo­rescent organ associated with second and fourth gill arches and located on their dorsolateral aspect.

a. Due to profuse branching and deep red colour it appears like a beautiful flower.

ii. A heavily vascularised, membranous diverticulum of the branchial chamber enclosing the arborescent organ.

5. Accessory Respiratory Organ of Singi Fish:

Heteropneustes sp. (Singi fish):

The accessory respiratory organs are two, one on either side of the body. These are air tubes growing out from branchial chamber and extending to very near the tail being situated close to the vertebral column.

The methods of killing Clarias are equally applicable to Heteropneustes.

Expose the branchial chamber of one side following the procedure adopted for Clarias. Give a deep incision with a sharp scalpel along the lateral line taking care it is not that deep to damage the air tube. Separate the muscles along the incision to expose the air tube. Working from the tail end trace the air tube up to its anterior end in the branchial chamber.

i. It is a long air tube extending from the posterodorsal corner of the branchial chamber to very near the tail.

ii. The anterior end communicates with the branchial chamber by a large opening.

iii. The posterior end is slightly narrow and closed.

iv. Four narrow ridges, made up of highly vascularised, small folds on the inner walls run along the whole length of the air tube.

6. Pituitary Gland of Rohu Fish:

Labeo sp. (Rohu fish):

In carps, the pituitary gland or hypophysis is an oval body attached to the ventral surface of the brain, just posterior to the crossing of optic nerves (Fig. 29.6A). It is connected to the brain by infundibulum and covered with Dura mater.

Collection of Pituitary Gland:

Two methods of collection are practiced:

A. Collection from whole fish:

The head of the fish is firmly hold with left hand in a dorsoventral position (Fig. 29.6B). To expose the brain a fairly large window is cut in the roof of the cranium with a stout scalpel or a sharp, pointed bone cutter. The fatty matters meninges around the brain is removed with a fine brush or cotton wool moistened with water. The residue of the fatty substances are washed away with clean water.

The medulla oblongata and the cranial nerves are cut close to their origin. The brain is lifted up from the anterior end, holding the olfactory lobe with a pair of fine forceps and removed from the cranium. In the process, the pituitary gland is left behind in the floor of the cranium. The membrane covering the gland is gently removed and the pituitary (Fig. 29.6B) is taken out with a blunt, bent needle.

B. Collection from severed head:

The foramen magnum is enlarged by cutting the supraoccipital bone with a bone cutter. The brain is either pushed forward with a narrow, blunt rod or pulled out with a pair of fine forceps, operating through the hole. The pituitary gland remains in its original position in the floor of the cranium. It is taken out with a blunt, bent needle.

Preservation of Pituitary Gland:

Pituitary gland is successfully preserved in any absolute solvent precipitant, viz. ethyl alcohol, isopropanol, acetone, etc. Immediately after collection the glands are put in the precipitant and the container tightly stoppered.

Later, the glands are transferred to containers with fresh precipitant, tightly stop­pered and stored in a refrigerator at 4°C. Exposure to atmospheric temperature in transit or at the time of use, following preservation does not greatly affect the potency of the hormone in the gland.


Lesson: Fish Dissection – Senior Secondary

Students will conduct a fish dissection to examine and identify the internal anatomy of a bony fish and learn how these features enable the fish to survive.

Preparation

Background information on fish anatomy and fish adaptations can be found in the Fact Sheet: Fish Anatomy.

This activity may be carried out by students either individually, in pairs, or in small groups (3-4 students).

It is recommended that you carry out a demonstration of the dissection with your class before allowing them to dissect their fish.

There are a number of related resources available to you including Virtual Fish Dissection video, interactive anatomy posters and PDF anatomy posters.

Each student, pair or group will require a fish. Source whole fish specimens from your fish monger. Species that are relatively easy to dissect and determine the internal organs of include:

  • Sand or school whiting
  • Yellowfin whiting
  • Mullet
  • Stripey snapper/tropical snapper/brown stripe snapper (no larger than

When purchasing your fish, remember to note their name if you are unfamiliar with them.

You can purchase your fish in advance and freeze them, however ensure they are fully defrosted before attempting to dissect them. It is recommended that you keep your fish on ice prior to dissecting them to keep the fish firm.

Each student/pair/group will require a:

  • fish to dissect
  • Shallow plastic tray, cutting board or mat or newspaper (to protect their work surface)
  • pair of sharp, blunt tipped scissors
  • pair of sharp, sharp scissors
  • pair of sharp tweezers
  • pair of blunt tweezers.

In addition, each student will require a:

  • Pair of disposable gloves
  • Copy of Student Worksheet: Bony Fish Anatomy – SS for your chosen species (or similar species)
  • Copy of Student Worksheet: Fish Anatomy – SS

Choose the worksheet for the species you have chosen or that exhibits a similar body shape to that you have chosen. The Student Worksheet: Fish anatomy is a question sheet which is applicable to most species of bony fish. You may also find Teacher Resource Sheet: Bony Fish Anatomy (for your chosen species or similar species) of assistance.

For clean-up you will require:

  • Warm, soapy water for cleaning trays and dissecting equipment
  • Heavy duty bin liners for disposing of dissected fish and disposable gloves – we recommend freezing until bin collection day.
  • Surface spray
  • Air freshener (optional)

Recommended resources

Poster: Bony fish – external anatomy (thinglink)

Poster: Bony fish – internal anatomy (thinglink)

Additional resources

Western Australian curriculum

Senior Secondary – Biology Year 11 General

Senior Secondary – Biology Year 11 ATAR

Senior Secondary – Integrated Science Year 11 General

Steps

  1. Explain to students the purpose of their fish dissection – e.g. identifying external/internal organs comparing external/internal organs with another species previously dissected identifying adaptations and their purpose.
  2. Conduct a demonstration of how you would like students to dissect their fish, identifying all labelling you wish for students to complete.
  3. Remind students of laboratory safety and safe use of dissection tools.
  4. Distribute equipment and fish to students. Ask students to record the common name of their fish and the total length from the tip of the nose (snout) to the tip of the tail (unstretched, in a relaxed position) on their worksheet.
  5. Examine the external features of the fish, including:
    • Dorsal fin
    • Lateral line
    • Caudal fin
    • Anal fin
    • Vent (anus)
    • Ventral (pelvic) fin
    • Pectoral fins
    • Operculum
    • Mouth
    • Nostrils
    • Eyes
Points for discussion:

Use the information provided in the Poster: Bony fish – external anatomy as discussion material for each of the features. Particular points of interest may be:

Points for discussion:

Use the information provided in the Poster: Bony fish – internal anatomy as discussion material for each of these features. Particular points of interest may be:

Points for discussion:

Is the swim bladder still intact? If it is, it will appear as an air filled sac.

Points for discussion:

Use the information provided in the Poster: Bony fish – internal anatomy as discussion material for the liver and kidney.

Points for discussion:

The structure of the gills is made up of three components – the gill filaments, gill arches and the gill rakers. Refer to the Poster: Bony fish – internal anatomy.

What is the purpose of the gill filaments?

What is the advantage of having multiple layers of gill filaments?

Also note – in the marine environment, the body fluids of fish are less salty than the surrounding environment so water diffuses out through the skin and gills. As a result, marine fish have to ‘drink’ continuously to avoid dehydration. They also only produce a small amount of urine.

To remove the otoliths:
  1. Place thumb in cavity where gills were and hold remainder of body firmly with other hand. Gently pull head back (towards fish’s dorsal surface) until you feel the spine break. Take care not to pull head off the remainder of the body.
  2. Using sharp, blunt scissors, cut the (now separated) first vertebrae parallel to the bone (i.e. scissors facing towards the mouth of the fish), about half way down the depth of the bone.
  3. Pull the cut piece of bone upwards to expose the otolith cavities. Sitting inside each cavity (there are 2) will be a single otolith.
  4. Using the sharp tweezers, carefully remove the otoliths from each of the cavities, taking care not to push them down into the cavity when you insert the tweezers.
Points for discussion:

The otolith is the fish’s inner ear, enabling them to listen to sound waves that travel through the water. Researchers can determine the age of bony fish by studying their otoliths. As a fish grows, tiny white and clear bands of calcified material are laid down in the otolith, similar to growth rings in a tree. The growth bands are counted under a microscope to determine the age of the fish.


Starfish Dissection

Echinoderms are radially symmetrical animals that are only found in the sea (there are none on land or in fresh water). Echinoderms mean “spiny skin” in Greek. Many, but not all, echinoderms have spiny skin. There are over 6,000 species. Echinoderms usually have five appendages (arms or rays), but there are some exceptions.

Radial symmetry means that the body is a hub, like a bicycle wheel, and tentacles are spokes coming out of it (think of a starfish). As larvae, echinoderms are bilaterally symmetrical. As they mature, they become radially symmetrical. Most adult echinoderms live on the bottom of the ocean floor. Many echinoderms have suckers on the ends of their feet that are used to capture and hold prey, and to hold onto rocks in a swift current.

  • Asteroideas are the true sea stars and sun stars.
  • Ophiuroideas are brittle stars and basket stars.

The differences between the two sub-types lies in how the arms connect to the central disk. Ophiuroids have arms that do not connect with each other. There is a distinct boundary between arm and central disk. Asteroids have arms that are connected to each other. Also, it is harder to tell with asteroids where the central disk ends and the arms begin. The sea star’s top surface (or skin) looks spiny if you examine it. If you look very closely you will notice that there are different types of growths on the surface. Some bumps are used to absorb oxygen, they are called dermal branchiae. Pedicellaria are pincher-like organs used to clean the surface of the skin. Barnacle larvae could land on a sea star and start growing if it were not for these organs.

How Do Sea Stars Move?

Materials:
Preserved starfish, dissecting pan, scissors, scalpel, forceps, T-pins, pencil, lab apron, safety glasses


Lesson: Fish Dissection

Students will conduct a fish dissection to examine and identify the internal anatomy of a bony fish and learn how these features enable the fish to survive.

Preparation

Background information on fish anatomy and fish adaptations can be found in the Fact Sheet: Fish Anatomy.

This activity may be carried out by students either individually, in pairs, or in small groups (3-4 students).

It is recommended that you carry out a demonstration of the dissection with your class before allowing them to dissect their fish.

There are a number of related resources available to you including Virtual Fish Dissection video, interactive anatomy posters and PDF anatomy posters.

There are two Student Worksheet variations associated with this lesson, depending on your focus for your dissection (external anatomy only or internal and external anatomy). Choose the worksheet for the species you have chosen or that exhibits a similar body shape to that you have chosen. There is also an associated question sheet (Student Worksheet: Fish Anatomy) which is applicable to most species of bony fish (optional). You may also find Teacher Resource Sheet: Bony Fish Anatomy (for your chosen species or similar species) of assistance.

Each student, pair or group will require a fish. Source whole fish specimens from your fish monger. Species that are relatively easy to dissect and determine the internal organs of include:

  • Sand or school whiting
  • Yellowfin whiting
  • Mullet
  • Stripey snapper/tropical snapper/brown stripe snapper (no larger than

When purchasing your fish, remember to note their name if you are unfamiliar with them.

You can purchase your fish in advance and freeze them, however ensure they are fully defrosted before attempting to dissect them. It is recommended that you keep your fish on ice prior to dissecting them to keep the fish firm.

Each student/pair/group will require a:

  • fish to dissect
  • Shallow plastic tray, cutting board or mat or newspaper (to protect their work surface)
  • pair of sharp, blunt tipped scissors
  • pair of sharp, sharp scissors
  • pair of sharp tweezers
  • pair of blunt tweezers.

Each student will require a:

  • Pair of disposable gloves
  • Copy of Student Worksheet: Bony Fish External Anatomy or Bony Fish Anatomy for your chosen species (or similar species)
  • Copy of Student Worksheet: Fish Anatomy (optional)

For clean-up you will require:

  • Warm, soapy water for cleaning trays and dissecting equipment
  • Heavy duty bin liners for disposing of dissected fish and disposable gloves – we recommend freezing until bin collection day.
  • Surface spray
  • Air freshener (optional)

Recommended resources

Poster: Bony fish – external anatomy (thinglink)

Poster: Bony fish – internal anatomy (thinglink)

Additional resources

LEARNING AREA STRAND SUB-STRAND CODES
Science Science Understanding Biological sciences ACSSU150, ACSSU175
Science Inquiry Skills Planning and conducting ACSIS140, ACSIS165
Processing and analysing data and information ACSIS145, ACSIS170
Communicating ACSIS148, ACSIS174

Steps

    1. Explain to students the purpose of their fish dissection – e.g. identifying external/internal organs comparing external/internal organs with another species previously dissected identifying adaptations and their purpose.
    2. Conduct a demonstration of how you would like students to dissect their fish, identifying all of the labelling you wish for students to complete.
    3. Remind students of laboratory safety and safe use of dissection tools.
    4. Distribute equipment and fish to students. Ask students to record the common name of their fish and the total length from the tip of the nose (snout) to the tip of the tail (unstretched, in a relaxed position) on their worksheet.
    5. Examine the external features of the fish, including:
      • Dorsal fin
      • Lateral line
      • Caudal fin
      • Anal fin
      • Vent (anus)
      • Ventral (pelvic) fin
      • Pectoral fins
      • Operculum
      • Mouth
      • Nostrils
      • Eyes
    Points for discussion:

    Use the information provided in the Poster: Bony fish – external anatomy as discussion material for each of the features.
    Particular points of interest may be:

    • Caudal fin shape and what this tells us about the way the fish moves
    • Mouth positioning and shape – use tweezers to pull open the mouth to show how widely it can (or cannot) open. Does the fish have a tongue? Does the species have teeth? What does all of this information tell us about the diet of the fish?
    Points for discussion:

    Use the information provided in the Poster: Bony fish – internal anatomy as discussion material for each ofthese features.Particular points of interest may be:

    • Can you identify if the fish is male or female? Note – you may not be able to if the fish is juvenile or spawned just prior to capture.
    • Can you identify any of the stomach contents?
    • Is the intestine short or long and coiled?
    Points for discussion:

    Is the swim bladder still intact? If it is, it will appear as an air filled sac.

    Points for discussion:
    Points for discussion:

    The structure of the gills is made up of three components – the gill filaments, gill arches and the gill rakers. Refer to the Poster: Bony fish – internal anatomy.


    The Anatomy of a Bony Fish

    • Contributed by Shannan Muskopf
    • High School Biology Instructor at Granite City School District
    • Sourced from Biology Corner

    I. Anatomy of a Fish (Coloring)

    Most vertebrates have the same basic body plan when it comes to internal organs. Like other vertebrates, fish have an esophagus which leads to the stomach where food is digested and passed to the intestine. Waste exits the fish at the anus. Some fish have a swim bladder which can help with flotation. Fish have a two chambered heart that is closely associated with the gills. The heart pumps blood over the gills where it becomes oxygenated and begins its path through the rest of the body, delivering that oxygen before returning the heart. This type of circulation is called single-loop circulation. Amphibians, mammals, and birds have double-loop circulation, where blood leaves the heart, goes to the lungs, and then returns to the heart before being pumped to the body.

    1. Caudal Fin (blue)
    2. Kidney (green)
    3. Dorsal Fin (yellow)
    4. Swim Bladder (blue)
    5. Esophagus (yellow)
    6. Operculum (brown)
    7. --- Lateral Line System (black)
    8. << Scales (purple)
    9. Gills (red)
    10. Heart (pink)
    11. Pelvic Fin (green)
    12. Liver (brown)
    13. Stomach (green)
    14. Intestine (dark blue)
    15. Reproductive Organs (orange)
    16. Anal Fin (pink)

    II. Fish Scales Tell the Age of a Fish

    Look at the image of the fish scale, like a tree, scales show rings that indicate periods of growth. Rings that are farther apart occur when the fish grows well and there is lots of food - in the summer season. Rings that are close together occur when the fish does not get much food and grows slowly. On the scale you can identify the summer growth and the winter growth. (There will be several rings in each). The core represents the fish when it was first born, as a fry. The rings near the edge are the most recent periods of growth.

    Color the summer growth periods green. | Color the winter growth periods blue.

    How old is this fish (in years)?

    III. Fish Fins Are Used for Swimming

    The fins of the fish are used for swimming but each one has a specific job. The dorsal fin is sometimes split into an anterior and posterior dorsal fin. Both are used to help the fish maintain its upright position in the water. The anal fin has the same function. Pectoral and pelvic fins are used for steering and the caudal fin is used to propel the fish forward. Fish swim in a side-to-side motion. Aquatic mammals swim with an up-and-down motion, which is consistent with their evolutionary relationship with land mammals.


    Inside the body cavity

    Look at the Fish Necropsy Manual before you start you'll find some good dissection images there.

    Open up the main coelomic cavity by making an incision from the vent forward to just behind the head. Note that you cut through several layers of tissue: skin, muscle, and the peritoneum, a smooth membrane lining the inside of the body cavity. You may want to remove one side of the body wall, exposing the internal organs.

    Liver

    The liver is large it secretes bile into the gall bladder, from which the bile passes into the intestine. The gall bladder usually looks like a small green blister on the surface of the liver.

    Digestive tract

    The digestive tract of fish is roughly similar to that of mammals. Food passes from the mouth down the esophagus to the stomach. You may be able to see pyloric ceca, which function as accessory digestive glands (mammals don’t have these). Look closely at the stomach. The pyloris, where partially digested chyme exits the stomach, is not at the posterior end it's closer to the anterior. You'll see small blood vessels at the posterior end of the stomach, but that's not where the chyme goes. Look for the pyloric ceca to find the beginning of the intestine. The intestine is fairly long. You may find remnants of food in the stomach. This is likely to smell bad I recommend cutting the stomach after you're done with everything else. You may also be able to find the pancreas near the pyloric ceca.

    Digestive System on the Fish Necropsy Manual

    Swim bladder

    The swim bladder is a large light-colored structure near the dorsal side of the body cavity. It is easy to find if it is filled with gas, but easy to miss if it is empty. Bony fish can adjust their buoyancy by putting gas into the swim bladder. The most abundant gas in the swim bladder is oxygen, which is released from the blood in the gas gland. The gas gland generates lactic acid, acidifying the blood in the gas gland and causing it to release its oxygen (remember the Bohr shift? In the gas gland, oxygen is released mainly by a related effect, the Root effect.). This gland is accompanied by a specialized countercurrent to maintain the incredibly strong gradient of oxygen partial pressure between the swim bladder and the blood. Some fish can have over 100 atmospheres of oxygen partial pressure in the swim bladder, but their blood can never contain more O2 pressure than the surrounding water, which never contains more O2 pressure than the air (0.2 atm).

    Since the swim bladder develops from the esophagus, it is covered under the Digestive System on the Fish Necropsy Manual.

    Gonads

    In a fish that is ready to reproduce, the gonads can be the largest organs in the body cavity otherwise these organs can be quite small. If your fish is a female, you should be able to see the small eggs in the single ovary in a male, the two testes will appear smooth and milky.

    Kidneys & urinary bladder

    Fish kidneys don't create a strong osmotic gradient, which is why fish can't make hyperosmotic urine. The kidneys of fish do not look at all like mammalian kidneys. They are long and thin and dark, and located along the very top of the body cavity, just ventral to the vertebral column. Most of the nitrogenous waste is secreted by the gills, not the kidney. Urine produced by the kidney enters the urinary bladder, which exits into the vent. See the Fish Necropsy Manual for good photos.

    In addition to its osmoregulatory functions, the kidney also performs hematopoiesis, the production of new blood cells. This might seem like a surprising function for a kidney, but the kidneys of mammals also secrete a hormone (erythropoietin, or EPO) that regulates hematopoiesis.

    Hematopoietic System on the Fish Necropsy Manual

    Heart

    The heart is located just beneath the gills the heart's entire output goes to the gills first, after which the oxygenated blood is sent to the rest of the body. After you've examined the other organs, try to cut away more of the surrounding tissues to reveal the heart. At first it may look like a dark blob, but feel it with your fingers. The firm, rubbery part is the ventricle, which pumps blood. The softer part is the atrium, which collects blood under lower pressure prior to pumping. Blood from the ventricle is pumped directly into the gills. Remember that in fish, the blood is pumped just once as it makes its way through the gills and systemic circulation. The fish heart is considered to be two-chambered, but you may observe more chambers than that see this article for a description. For more detail and an excellent illustration, see Cardiac morphology and blood pressure in the adult zebrafish.

    Circulatory system on the Fish Necropsy Manual

    Brain & Eyes

    It's possible, but difficult, to examine the brain in these fish. The best strategy is to cut off the head near the first vertebra. Then carefully remove the bony top of the head, revealing the top of the brain.

    If you dissect the eyes, you'll find the lens inside. Fish lenses are nearly spherical unlike mammals, fish focus their eyes by moving the lens back and forth rather than changing the shape of the lens. The lens, made of protein, is transparent when the fish is alive, but becomes white and almost opaque after the fish dies.

    Nervous System on the Fish Necropsy Manual


    Fish dissection online


    Virtual Fish Dissection: Island Kelpfish (Alloclinus holderi) Photo credit: MRI and 3D by UCSD Keck Center for fMRI CT data from Digimorph at the University of Texas at Austin Courtesy UCSD Keck Center for fMRI CT data from Digimorph at the University of Texas at Austin

    Students, scientists, or anyone with an internet connection will be able to digitally probe and dissect different kinds of fishes from anywhere in the world using their desktop computer. Researchers at the University of California , San Diego have applied magnetic resonance imaging technology, or MRI, to create a high resolution, 3-D online catalog of fishes from the Scripps Institution of Oceanography's Marine Vertebrate Collection. Scripps' Marine Vertebrate, or "Fish," Collection, is among the largest and most comprehensive collections of its kind, containing 90 percent of all known families of fishes. With more than 2 million specimens, the collection is used by researchers around the world to investigate the systematics, biodiversity, physiology, ecology and conservation of fishes. Through the Digital Fish Library project, coordinators will image at least one of every 482 fish families in the world.

    How can this collection be used?

    Hastings :With more than 2 million specimens, the collection is used by researchers around the world to investigate the systematics, biodiversity, physiology, ecology and conservation of fishes. The collection includes approximately six thousand species of fishes. One of the research goals of the Scripps Fish Collection is to study the evolution of fishes and we interpret the evolution and ecology to some extent of fishes based on their internal anatomy. Describing internal anatomy of fishes is relatively difficult. It requires tedious dissection of whole specimens, but this new technology will now allow us to go in and actually in a very much more rigorous way examine the internal anatomy of specimens without having to do these very tedious dissections.

    How are the fish digitized?


    Fish sections via MRI: Galapagos Shark (Carcharhinus galapagensis) Photo credit: UCSD Keck Center for fMRI

    The fish are scanned with a Magnetic Resonance Imager (MRI). A simplified explaination is that very strong magnetic force lines up many of the water molecules in the fish tissues. Various radio frequences can then be used to interpret how these spinning particles wobble on thier axies, and through analysis, be used to differentiate tissue types and locations. The scans, when interpreted mathematically, result in high resolution, three dimensional images which enable visualizaton of all the various internal organs and tissues. Different tissue types can be color coded enabling students to easily compare similar tisue structures within different fish. The scans are being done at the University of California at San Diego's (UCSD) Keck Center for Functional Magnetic Resonance Imaging (fMRI).


    Perch Dissection 2

    The fish in the class Osteichthyes have bony skeletons. There are three groups of the bony fish — ray-finned fish, lobe-finned fish, and the lung fish. The perch is an example of a ray-finned fish. Its fins have spiny rays of cartilage &/or bone to support them. Fins help the perch to move quickly through the water and steer without rolling. The perch also has a streamline body shape that makes it well adapted for movement in the water. All ray-finned fish have a swim bladder that gives the fish buoyancy allowing them to sink or rise in the water. The swim bladder also regulates the concentration of gases in the blood of the fish. Perch have powerful jaws and strong teeth for catching and eating prey. Yellow perch are primarily bottom feeders with a slow deliberate bite. They eat almost anything, but prefer minnows, insect larvae, plankton, and worms. Perch move about in schools, often numbering in the hundreds.

    The scientific name for the yellow perch, most often used in dissection, is Perca flavescens (Perca means “dusky” flavescens means “becoming gold colored”). The sides of the yellow perch are golden yellow to brassy green with six to eight dark vertical saddles and a white to yellow belly. Yellow perch have many small teeth, but no large canines. Yellow perch spawn from mid-April to early May by depositing their eggs over vegetation or the water bottom, with no care given. The eggs are laid in large gelatinous adhesive masses.

    Preserved perch, dissecting pan, scalpel, scissors, forceps, magnifying glass, dissecting pins, apron, gloves, eye cover, tape measure


    Identifying internal structures of dissected fish - Biology

    Starfish Dissection Lab

    Introduction:

    Echinoderms are radially symmetrical animals that are only found in the sea (there are none on land or in freshwater). The word "echinoderm" means "spiney-skin" in Greek. Many, but not all, echinoderms have spiney skin. There are over 6,000 species of echinoderms. Echinoderms usually have five appendages (arms or rays), but there are some exceptions.

    Radial symmetry means that the body is a hub, like a bicycle wheel, and tentacles are spokes coming out of it (think of a starfish). As larvae, echinoderms are bilaterally symmetrical. As they mature, they become radially symmetrical. Most adult echinoderms live on the bottom of the ocean floor. Many echinoderms have suckers on the ends of their feet that are used to capture and hold prey, and to hold onto rocks in a swift current.

    SPECIES: Asterias forbesi or Asterias rubens ( Asterias forbesi…however is the more widely accepted species name)

    Sea stars (group name Stelleroidea) are sometimes called starfish, though they are not real fish (they lack both vertebrae and fins). There are two sub-types of sea stars:

    Asteroideas : these are the true sea stars and sun stars

    Ophiuroideas : these are the brittle stars and basket stars

    Asteroideas
    Ophiuroideas

    The differences between the two sub-types lies in how the arms connect to the central disk. Ophiuroids have rays that do not connect with each other. There is a distinct boundary between the rays and the central disk. Asteroids have rays that are connected to each other. Also it is harder to tell with asteroids where the central disk ends and the rays begin. The sea star's top surface (or skin) looks spiny if you examine it. If you look very closely you will notice that there are different types of growths on the surface. Some bumps are used to absorb oxygen, these bumps are called dermal branchiae. Pedicellaria are pincher-like organs used to clean the surface of the skin. Barnacle larvae could land on a sea star and start growing if it were not for these organs.

    Each sea star had hundreds of tiny feet on the bottom of each ray. These are tube feet, or podia. These tiny feet can be filled with sea water. The vascular system of the sea star is also filled with sea water. By moving water from the vascular system into the tiny feet, the sea star can make a foot move by expanding it. This is how sea stars move around. Muscles within the feet are used to retract them. Each ray of a sea star has a light sensitive organ called an eyespot. Though it cannot see nearly as well as we do, sea stars can detect light and its general direction. They have some idea of where they are going.

    The diet of sea stars includes all types of mussels and other bivalves with clams and scallops being the most common meals for the sea star. The means of obtaining the food is quite unique in the animal kingdom. In order to make a meal out of a clam or scallop the sea star must use its tube feet as a way to "feel around" in order to find its food because they lack the ability to visually see. Once a clam has been designated for a meal, this is how the sea star will go about making a meal of a clam:

    The sea star will use its rays and suckers on its tube feet to pry open the clam shell.

    The sea star will then extend its stomach out of its mouth and into the clam's own shell.

    The hepatic caeca will produce powerful digestive enzymes that will dissolve the soft body of the clam allowing the sea star to absorb this with its stomach.

    When done feeding, the sea star will then use its retractor muscles to pull the stomach out of the clam and back into its mouth.

    Sea Star Eggs & Scientific Research

    Female sea stars produce large amounts of eggs and are readily available. Due to this, scientists have an almost endless supply of eggs available for research studies. Recently, scientists have studied the sea star eggs for their research in the areas of reproductive and development studies. The eggs (correctly called "oocytes") are harvested and stored in their pre-meiosis phase and then stimulated later to complete their division. This allows the scientists to study the development of the eggs at any point in the cell division. Scientists hope to learn more about the process of the cell division involved with the regenerative ability of the the sea stars.

    DISSECTION PROCEDURE:

    Part 1: External Anatomy

    1. Place the starfish on your dissection tray with its aboral surface facing upward.

    2. Using your diagram sheets and the pictures below to locate the following structures, and note their functions:

    ¨ Arms or Rays: these are the five extensions that you see projecting from the middle of the starfish. These are highly regenerative and are replaced easily when damaged. You might even see one of our starfish that has a ray that is significantly smaller than the rest of them. This is because the ray had been damaged or lost and it has regenerated a new one. The two rays which are closest to the madreporite are known as Bivium. The other three rays are referred to as the Trivium .

    ¨ Central Disk: this is the middle area of the starfish from which the rays extend. It is often poorly defined and difficult to locate the perimeters, but on some you may be able to distinguish a pentagon shaped area.

    ¨ Aboral Surface : the aboral surface is the surface that does not contain the mouth.

    ¨ Madreporite : this is a small, white, circular area that is located in the central disk area. It is usually off-center and is sometimes called the sieve plate . It is used by the starfish to take in water to fill its water-vascular system. If you scratch it with your probe you will notice that it is rather hard and feels like stone.

    ¨ Anus : the anus is rather minute and difficult (pretty close to impossible!) to see but it is also located on the central disk. Wastes are excreted through this opening to the outside of the starfish.

    ¨ Spines : the entire aboral surface is covered with many short, rough, limy spines

    ¨ Eyespot : the eyespot is located at the distal end of each ray. It is a collection of photosensitive cells which the starfish uses to detect light or absence of light.

    3. Now flip your starfish over so you can view the oral surface. Use your diagram sheets and the pictures below to identify the following structures:

    ¨ Ambulacral Groove : this is where the tube feet are located. They are found along each ray.

    ¨ Ambulacral Spines : these are slender rods located on the margins of the ambulacral grooves.

    ¨ Tube Feet : soft, slender, with expanded tips. There are two or more rows in each ambulacral groove.

    ¨ Mouth : opening in the middle directly beneath the central disk where all the arms connect.

    Part 2: Internal Anatomy

    1. Use the scissors to cut off the extreme tip of each arm of the bivium. Then cut along the lines labeled A, B, and C as shown in the diagram below. Do this to both of the rays of the bivium.

    2. In turn, lift and carefully remove the aboral surface of each arm, loosening the delicate mesentaries beneath by which the soft organs are attached. Also, cut around the central disk to expose the stomach underneath.

    3. Use your diagram sheets and the pictures below to identify the following structures:

    ¨ Coelom: space containing the internal organs lined with thin ciliated peritoneum

    ¨ Stomach: sack-like structure found underneath the central disk.

    ¨ Retractor Muscles : small, sinewy structures that connect to the stomach. These are used to pull the stomach back into its mouth once the starfish is done feeding.

    ¨ Hepatic caecum : long, greenish organs found in each ray. Has many finger-like lobes. These organs are used for secreting digestive juices and enzymes needed for feeding. The plural form of the word is "hepatic caeca".

    ¨ Gonads : small, bi-lobed structures found below the hepatic caeca in each arm. May be very small in some specimens due to the fact that the starfish may not be sexually mature yet.

    4. In order to determine the sex of your starfish, you must examine a small portion of the gonad with the microscope.

    5. Make a mounted slide by taking a SMALL PORTION of the gonad and placing it on the microscope slide. Cover this with a cover slip and observe under the low power objective.

    6. If your starfish is a female you will see the eggs. This resembles small circular-looking objects. Below is a picture of what starfish eggs will look like under magnification.

    7. If your starfish is a male you will see the sperm. Instead of seeing circular objects you will see something that resembles sand. These are the sperm cells. Your specimen may not be as clear as the one below, in fact it may just look like tiny grains of sand. but starfish sperm look like the picture below.

    Part 3: Water Vascular System

    1. Remove the stomach from the central disk area.

    2. You will now be able to see the calcite skeletal system of the starfish and also the parts of its water vascular system. Use you diagram pages to locate the following structures:

    ¨ Ring Canal : hard, calcium-based, ring-like structure around the mouth region.

    ¨ Tiedemann bodies: nine, small swellings in the ring canal.

    ¨ Ampullae : many, small, spherical structures in the floor of the coelom. These connect to the tube feet.

    ¨ Tube feet : the tube feet function in locomotion, feeding, and respiration. The tube feet in a starfish are arranged in grooves along the arms. They operate through hydraulic pressure. They are used to pass food to the oral mouth at the center, and can attach to surfaces.

    3. Dispose of your starfish in the garbage and clean up your trays and utensils.

    4. Complete your lab review worksheet. Click HERE for the Starfish Dissection Lab Companion that will detail what you will need to know for the quiz.


    Watch the video: Bony Fish Perch Anatomy (May 2022).