It Identifies and expounds the external features of the specimen It identifies and expounds the internal features and systems It provides similarities between a toad and bony fish

1. FACULTY OF SCIENCE
DEPARTMENT OF BIOLOGY
BIO21O4: ICHTHYOLOGY AND HERPETOLOGY
COURSE ORGANISER: DR. SR. JANE YATUHA
AMPHIBIAN GROUP PRACTICAL REPORT
GROUP 4
.

2. STUDENTS NAMES REGISTRATION NUMBER
BUKENYA ANDREW 2020/BS/022
MUSEMEZA IGNATIUS 2020/BS/059
OWIDI BARBRA 2020/BS/102
KUSHEMERERWA CHRISTMAS 2020/BS/168/PS
KHAMALI SAMUEL 2020/BS/160/PS
SSENGALI SIMON PETER 2020/BS/084

3. INTRODUCTION
• TITLE: A PRACTICAL ON DISSECTION OF A SELECTED AMPHIBIAN TO
STUDY ITS PHYSIOLOGY (ANURAN)
• AIM:
To Identify the external features of the specimen
To identify the internal features and systems

4. INTRODUCTION
• The specimen in question was obtained five days before the practical and
taken to the laboratory for preservation.
• The specimen collected is an anuran.
• It was obtained in one of the drier marshes near river Rwizi.
• The specimen was so sensitive to being trapped and for that Matter a
combined effort of three group members took part in this activity.
• Due to poor techniques used we did not manage to obtain the specimen
while alive and this hindered us from seeing some parts after being
preserved for long time.
• Features like blood vessels were observed during the experiment though
not extensively since only the major blood vessels were seen.

5. Classification of the obtained specimen
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Anura
Family: Bufonidae
Genus: Bufo
Species: B. bufo

6. EXTERNAL FEATURES.
The specimen was laid on a dissecting board and clearly observed
externally with the dorsal view and ventral parts in much focus
The following features were examined:
• Eyes
• Skin
• External nares
• Ear drum
• Mouth
• Limbs

7. EXTERNAL FEATURES CONT’D
Fore limb
Upper Skin
Hind limb
Digit

8. EXTERNAL FEATURES CONT’D
 Head.
• The head is triangular shaped and directly attached to the trunk,
together with the body it gives the specimen a streamlined position.
This could be important in reducing air and water resistance during
locomotion on land and in water respectively.
• Eyes; Are dorso-laterally positioned on the head posterior to the
external nares and anterior to the ear drum. They are seen protruding
though covered in a skin due to the fact that the specimen was dead.
There positioning enables them to see through an increased angle
probably 360 degrees.

9. EXTERNAL FEATURES CONT’D
• External nares; two small openings positioned on the anterior side of
the head above the mouth. The positioning could be important in
being effective to collecting air and detecting smell
• Ear drum; the two membranes found soft and leathery dorso-
laterally positioned on the head posterior to the eyes. It is made up of
tough membrane when felt, this would be important in withstanding
external pressure. The positioning enables it to pick sound waves
from a wide field.
• Mouth; the opening that spans ¾ of the head by seeming to cut it
into two dorso-laterally but more to lateral. Its located below the
nares

10. EXTERNAL FEATURES CONT’D
External nare
Eye
Ear drum

11. EXTERNAL FEATURES CONT’D
Mouth

12. EXTERNAL FEATURES
 Skin:
• the skin was rough on the dorsal part with small protrusions from it.
This the roughness was extended to the limbs and head when viewed
dorsally, the skin was dark-brown in color, this could be important in
camouflage in most terrestrial environments.
• On the ventral part, the skin was less rough with loose attachment to
the body probably associated with easy diffusion of gases, it was more
white in color compared to the dorsal outlook.

13. DORSAL SIDE OF THE SPECIMEN
The dorsal view is
predominantly
composed of the
dark brown skin

14. VENTRAL SIDE OF THE SPECIMEN
The skin is whitish, this could be
associated with mimicking the
sky while resting in water to
confuse away the predators
whitish skin

15. EXTERNAL FEATURES CONT’D
 Limbs:
• Hind limbs; are attached to the posterior part of the
trunk, are long and muscular this would be probably
be useful, in generation of a strong thrust force
during jumping on land.
• The hind limb is divided into three regions with the
most posterior one having 5 digit divisions (fingers)
• The digits have webs in between them, this signifies
the specimen spends some time in water where the
webs aid in swimming.

16. EXTERNAL FEATURES CONT’D
 Fore limb: Are attached on the lateral
side posteriorly to the head and
anteriorly to the trunk.
• Are short and stout probably for shock
absorption during landing.
• The most posterior part has four digits
spread out from each other.

17. INTERNAL FEATURES OF THE SPECIMEN AFTER
DISSECTION
• The internal features of the specimen include;
The heart
The lungs
The gonads
The liver
The pancreas
The intestines
Tongue

18. The systems observed after dissection
• The circulatory system
• The nervous system
• The digestive system
• The muscular system
• The respiratory system
• The endocrine system
• The reproductive system
• The Skeletal system
• The excretory system

19. The digestive system
• The digestive system consists of the alimentary canal and its associated digestive
glands.
• The alimentary canal of the specimen is a long tube starting from the mouth in
the buccal cavity and ends in the cloaca,
• The layer lining the outer layer of the alimentary canal of the specimen is called
the serous coat.
• The mouth is bounded by upper and lower jaws. The mouth leads into the buccal
cavity.
• The buccal cavity bears a large fleshy tongue. The tongue is kept sticky, it is fixed
anteriorly but free behind.
• The buccal cavity narrow towards the pharynx which leads into the esophagus.
The esophagus opens into the stomach which is slightly curved.
• The broad anterior part of the stomach is called the cardiac end and the posterior
end is called the pyloric end.

20. The digestive system continued
• The pyloric part opens into the intestines. From the theory part the
opening is guarded by the cardiac sphincter muscles to regulate the
exit of food from the stomach.
• The large part of the intestines is called the large intestines which are
divided into the rectum and cloaca which opens to the outside.
• The digestive system is also accompanied by the pancreas, the liver
among others.

21. The digestive system
Stomach
Small intestine
Large intestine

22. The circulatory system
• The circulatory system consists of the blood vascular system and the
lymphatic system but in the practical carried out we were only able to
see some parts of the blood vascular system and the lymphatic
system was not seen. Double circulatory system occurs since blood
vessels are seen in body originating from the main pumping organ.
• The blood vascular system is the internal transport mechanism by
which nutritive materials, hormones, waste products, carbon dioxide
and oxygen are conveyed to different parts of the body.

23. The circulatory system cont’d
• The blood vascular system consists of the heart which is the pumping
machine blood and blood vessels.
• Blood is the main circulatory fluid.
• The heart is the central pumping organ in the cardiovascular system.
It is a pear shaped muscular structure situated in the anterior part of
the body cavity. The outer layer of the heart is the pericardium.
• The heart was lifted and turned anteriorly to expose major blood
vessels.
• Posterior venacava which is seen come out of the heart posteriorly,
returns blood from all over the body to the heart.
• The sinus venosus which is seen connecting the major blood vessels.

24. The circulatory system cont’d
Posterior venacava
Sinus venosus

25. The heart;
heart

26. Vascularized skin
Blood vessel in the skin

27. The nervous system
• The nervous system includes the central nervous system which combines the
brain and the spinal cord. The posterior part of the central nervous system is
called the spinal cord and the anterior is the brain.
• For this case a spinal cord is considered because it was the only one observed.
The spinal nerves originate from the ganglion.
• Nervous system in a toad appears as white thread like structures arising from the
central nervous system
• The small ganglia were observed giving rise to the spinal nerves.

28. Spinal cord
• 2. Spinal nerves
• A short dorsal branch to the skin and muscles of the back
• A large ventral branch to the skin and muscles of the abdomen and
others to limbs

29. Spinal cord;
Spinal nerve

30. The skeletal system
• The skeleton supports and protects toad body
• The toad has no ribs.
• The toad does not have a tail.
• The toad has a backbone

31. Skeletal system
vertebral column

32. The endocrine system
• This includes many ductless glands which secret hormones directly
into the blood stream.
• The glands which were seen during the conduction of the practical
include; the pancreas and the gonads.
• The pancreas contains two types of the glandular structures. The
exocrine part secrets the pancreatic enzymes and the endocrine part
secrets the hormones.
• The gonads besides production of germ cells, they produce sex
hormones.
• The liver is also important in hormone production.

33. The gonads under endocrine
gonads

34. The pancreas;
pancreas

35. The liver as an endocrine organ
Left lobe Right lobe
third lower lobe

36. The respiratory system
• This system allows intake of oxygen inside the body and carbon
dioxide and water are given out.
• According to the features possessed like lung lobes, aerobic
respiration occurs.
• Since the toads where caught from water to the land and they were
still alive before their death, that means terrestrial and aquatic
respiration occurs.
• Terrestrial respiration involves utilization of the oxygen in air and
aquatic respiration involves respiration of the oxygen in water.
• Due to the moist skin possessed by the specimen, it meant that
cutaneous respiration from the skin can occur. The respiration from
the lungs is called the pulmonary respiration.

37. Respiration continued
• Organs involved in pulmonary respiration include;
Nostrils or nares both internal and external.
Buccal cavity
Lungs
• The buccal cavity opens into a certain chamber which then opens into
the bronchi which then opens into the lungs alveoli.
• The skin acts as an additional respiratory organ.

38. Buccal cavity
Roof of buccal cavity
Eye socket
Buccal cavity
Tongue
Floor of buccal cavity

39. Buccal cavity
• The mouth opens to the outside at the edges and empties into a tube
which is hollow and is identified as the throat or gullet.
• The space between the edge of the mouth and the beginning of the
tube is the buccal cavity.
• There is a lower part which could be identified as the floor of the
buccal cavity.
• The upper part appears to be the roof with protrusions of the eye
sockets.
• We were unable to observe the vomerine and maxillary since in the
picture they are clearly not seen.

40. Buccal cavity
• Tongue.
• The posterior end of the tongue is attached anteriorly to the floor of
the buccal cavity. The anterior part of the tongue is left free and lies
towards the posterior side of buccal cavity floor.
• It is muscular, long, flat and broad, slippery, sticky and is capable of
protraction.
• The tongue is long to enable it to capture prey at long distances
• The tongue is attached anteriorly to easily capture prey at a long
distance.
• The tongue is sticky to stick on prey after capturing them.

41. Buccal cavity
• Eye sockets.
• There is a pair of protrusions seen originating from the roof of the
buccal cavity.
• The protrusions are in line with the eyes seen dorso-laterally
positioned on the outside. These enable eyes to turn properly while
trying to view different parts of the environments.
• There are small openings called nares in the roof.

42. Lungs of the specimen under respiration
Left lung lobe
Right lung lobe

43. Excretory system
• The organs responsible for excretion include the kidney(we were
unable to see them), the liver, lungs and the skin.
• The liver excretes bilirubin in bile.
• The lungs excrete carbon dioxide.
• The skin excretes carbon dioxide

44. The liver as an excretory organ (the three
liver lobes)
Left lobe Right lobe
third lower lobe

45. Lungs of the specimen under excretion
Left lung lobe
right lung lobe

46. Reproductive system
• The gonads were the two ovaries which is a much folded sac with an
irregular shape fixed to the ventral surface of the specimen.
• The specimen was a female and among the reproductive organs
gonads where seen.

47. The gonads under the reproductive
gonads

48. Muscular system
• The muscular system is composed of muscles which are used
primarily for movement of the body.
• The muscles were observed and seen in the thigh, limbs both fore
and hind. This enables the specimen to move.
thigh muscle

49. Similarities between a toad and a bony fish.
• Both have dorsal laterally positioned eyes.
• Both possess the vertebrae.
• Both possess paired nostrils.
• Both have nictating membranes on their eyes.

50. DIFFERENCES BETWEEN A TOAD AND A BONY FISH
toad
• Has a moist skin, scales are
absent.
• Lateral line absent.
• Have two lung lobes.
• Operculum absent.
• Three chambered heart.
• Tailless body.
Bony fishes
• Body covered with scales.
• Possess a lateral line.
• Possess gills, lungs absent.
Except in lung fishes with one
lung
• Possess operculum.
• Two chambered heart.
• Have a tail fin.

51. DIFFERENCES BETWEEN A TOAD AND A BONY FISH
Toad.
• External eardrum present.
• Swim bladder absent.
• Tetrapod with four limbs for
locomotion.
Bony fishes.
• External eardrum absent.
• Swim bladder present.
• Possess paired fins.

52. REFERENCE(S)
• HGQ Rowett with John Masaba & Muhangi Crispus: Guide To
Dissection, Hodder education.
• Extremophile Fishes by Rudiger Riesch, Michael Tobler, Martin Plath.