Reptiles Flashcards
Name and describe the 4 orders in the reptilia class.
Chelonia – tortoises and turtles
Crocodilian – caimans, crocodiles and alligators
Sphenodonta – tuataras. The most orimitive of the living reptiles. There are only 2 species left alive these days
Squamata – amphisbaenians (worm lizards), lizards and snakes
Distinguish boids and colubrids.
Colubrids are very diverse and 2 thirds of all snake species are in this family. Mostly non-venomous but there are exceptions. Venom of the boomslang, for example, is fatal to humans.
Boids are the constrictor snakes ad include boas and anacondas. Pythons also referred to as boids.
List the features of the snake skull.
Cranial kinesis
Quadrate bone
No mandibular symphysis
Heavily ossified braincase
No external ear/tympanic membrane
What is the advantage to snake skulls having cranial kinesis?
Flexible and mobile bones to allow movement
What is the advantage of snake skulls having quadrate bone?
Allows wide gape, almost 180 degrees. Located very caudally in the skull and articulates with both the mandible and the brain case itself.
What is the advantage of snake skulls having no mandibular symphysis?
Instead the 2 halves of the mandibles are joined by a very flexible elastic ligament, which allows width wise separation of the lower jaw.
What is the advantage of snake skulls having heavily ossified braincases?
Very rigid and protects the brain from damage while the snake is swallowing live prey.
How do snakes hear with no external ear/tympanic membrane?
Hear vibrations via quadrate and columella, equivalent to the stapes in mammals. As the snake moves along the ground, the quadrate bone is more or less in direct contact with the ground and can pick up vibrations and transmit them via the columella to the middle ear.
Describe the skeleton of the snake.
- 400 pre-cloacal vertebra
- All but first 2 cervical have ribs
- No sternum or costal cartilages and ends of the ribs attach via muscle to the inner surface of the ventral scales
- No pelvic girdle or forelimbs but some vestigial part of pelvic girdle may be present in boids in the form of external spurs.
Describe vision and hearing in the snake.
Vision is poor and do not have eyelids.
Hearing – no external ear, but pick up vibrations via quadrate and columella
Describe olfaction in the snake.
Highly developed:
- Vomeronasal organ (of Jacobson)
- Domed cavities lined with sensory epithelium – olfactory nerve
- Tongue acts as sensory organ, protrudes through lingual fossa to collect and bring odours to vomeronasal organ.
- Very sensitive system that blind snakes can use to detect prey.
Describe infrared detection in snakes.
In a pit viper, there is an additional structure between the eye and nostril called the pit organ. It contains specialised infrared receptors that are very sensitive and allow these snakes to detect warm-blooded prey. Boas and pythons have a less sensitive system where they have a series of slits in the same region.
Compare the lizard skull to the snake skull.
Mandibular symphysis present, so has a much narrow gape than the snake.
Describe vision in the lizard.
Large orbit and sclera present. Sclera supported by a ring of small bones called the scleral ossicles. Vision more developed than in snakes.
Describe hearing in the lizard.
No external ear but there is a shallow depression in which the tympanic membrane is present in some lizards. In general, hearing in lizards tends to be better than snakes and chelonia.
Describe olfaction in the lizard.
Vomeronasal organ present in some lizards.
Describe the parietal/3rd eye of lizards.
Present in most lizards and tuatara. Located in dorsal midline of the head between the regular eyes. Sensitive to change in light and dark, and can actually contain a lens and a retina, but does not form images. Associated with pineal gland and is involved in circadian rhythms.
Describe the tortoise skeleton.
- Mandibular symphysis present
- 8 cervical vertebrae and flexible to allow the head to be retracted into the shell
- 10 trunk vertebrae that are fused to the upper part of the shall/carapace
- Pectoral and pelvic gridles and inside ribs are fused to the carapace and are very slender.
- No sternum
- Tripartite shoulder arrangement: scapula fused to the carapace by a ligamentous attachment, an acromion process that projects medially and almost touches its counterpart on the other side, and a coracoid process that projects more caudally.
Describe vision, olfaction and hearing in the tortoise.
Vision – highly developed, more than lizards and snakes. Scleral ossicles present to support the sclera.
Olfaction – modified vomeronasal organ but is not quite as sensitive as snakes or lizards.
Hearing – poor. No external ear
What are the external features of snakes?
- Long tubular body, short tail
- Generally smooth and featureless so as to not impede movement on the ground
- No moveable eyelids
- No external ear
- No limbs, however some boids have vestigial pelvis/spurs
- Arboreal species can have prehensile tail to help grasp tree branches.
Describe snake integument.
- Epidermis thickens and folds to produce scales – allows great expansion when consuming prey
- Transparent spectacle/brille covers eye that protects the cornea
- Single wide scales ventrally gastropeges protect and give support to the ventral surface of the snake and are also important in locomotion.
- Paired subcaudal scales, caudal to vent
What is ecdysis?
Skin shedding. The process allows growth. Snakes will shed their complete skin and the folds in the epidermis allow this.
Describe the process of ecdysis.
- Loosen the skin around its mouth by rubbing the snout against any available surface.
- Lymph builds up between the new and old layers of the epidermis.
- Markings become obscure, and as the spectacle is continuous with the epidermis, the spectacle is shed as well. 4. The spectacle becomes opaque and the snake cannot see very well and can become irritable.
- Shed skin is colourless, as the pigment containing cells/chromatophores are found in the dermis.
- Snake will then crawl out of the shed skin and so the shed skin is inside out.
What is unique about ecdysis in rattle snakes?
The last scales are not shed in this process but are retained to form the rattle. This means at each successive moult, there will be an increase in length of the rattle.
What are the external features of lizards?
- Legs apart from slow worm (worm lizards/amphisbaenians)
- Short trunk long tail, opposite to snakes
- Moveable eyelids
- External ear openings
What are the properties of tails in different lizards?
- Prehensile in some lizards, like chameleons
- Fat storage in others, like geckos
- Autonomy – self amputation, like iguana
What is the purpose for tail autonomy?
They do this when threatened. It is thought that is a lizard is attacked, it will self-amputate its tail as a defence mechanism, in the hopes that a predator may still be distracted by eth still twitching tail while the lizard escapes. In this case while handling, bleeding is not a concern, as there is a sphincter surrounding the tail vein which will clamp down and prevent bleeding.
Describe the lizard integument.
- Modified epidermis for display purposes, such as gular pouch/fold that can be inflated with air to make the lizard appear larger, used for sexual display to attract females or a territorial display. Integument along the dorsal surface can also be modified to give nuchal dorsal crests.
- Ability to change colour – chameleons
- Ecdysis – skin shed in pieces, not whole like in snakes.
What are the external features of tortoises?
- Shell – bony plate covered in horny scales. The shell is part of the integument and is continuous with the integument that covers the appendages.
- Scales
- Moveable eyelids and nictitating membrane
Describe the structure of the tortoise shell.
- Domed upper shall is called the carapace
- Flat lower shell is called the plastron
- Carapace and plastron are joined at bridges laterally.
- There are 2 apertures – the more cranial aperture is known as the axillary aperture and the more caudal aperture is called the inguinal aperture.
- Shell made from fused dermal bone, which consists of 60 bones, which are derived from the modified pectoral, pelvic girdles, trunk vertebrae, sacrum and ribs, that are all fused together.
What are scutes?
- Dermal bone is covered in keratinised epidermal scales, called scutes.
- Scutes – undergo ecdysis in aquatic species, like turtles, but they shed piecemeal like lizard. Vulnerable period, as the skin becomes more permeable and may be more venerable to infection.
- Scutes and underlying dermal bone do not overlap. This gives added strength to the shell.
What are the different scute types on the carapace?
- Small cervical scute, just caudal to the head.
- Marginal scutes around the edges
- Pleural scutes, medial to the marginal scutes
- Vertebral scutes lie in a line where the vertebral column would be
What are the different scute types on the plastron (cranial to caudal)?
Gular scute, just caudal to the head
Humeral scutes
Pectoral scutes
Large abdominal scutes
Femoral scutes
Anal scutes
How can shell and tail morphology be used to sex male tortoises?
- Plastron lightly concave caudally to allow male to mount female easily
- Longer thicker tail
- Vent beyond carapace
- Scute over tail hooked/curved
How can shell and tail morphology be used to sex females?
- Plastron flattened
- Shorter, thinner tail
- Vent at tail base
- Scute over tail flattened
Describe the gross cardiorespiratory system in snakes.
- Elongation led to asymmetrical viscera
- With paired organs, organs on the right are cranial and larger than those on the left. In some cases, the organs on the left hand side are missing all together.
- Divide snake into cranial, middle third and caudal thirds
Describe the upper respiratory tract of snakes.
- Glottis easily visualised and so is easy to intubate. It is formed from the larynx and the first few tracheal rings. It is very mobile so can be laterally extended at the side of the mouth during feeding to allow breathing when eating large prey.
- External nostrils of the nares
- Internal nares/choanae that the glottis rests in when the mouth is closed.
- Snake has no vocal cords but can hiss by forcing air through the glottis.
What is contained in the cranial third of a snake?
- Cardiovascular system – heart lies cranioventral to tracheal bifurcation
- Respiratory system – trachea and cranial part lung. Lung extends down length of middle 3rd
- In most species of snake, the right lung is functional while the left lung is vestigial
- Oesophagus and part of the liver also present in this third
Describe the structure of the reptilian heart.
- 3 chambered heart – 2 atria, completely separated, 1 ventricle
- The ventricle is separated into 3 sub-chambers by the timing of ventricular contraction and muscular ridges. Means that oxygenated and deoxygenated blood never actually mix.
- Reptiles have 2 aortae, right and left, which go on to fuse caudal to the heart.
Describe the path of blood flow around the reptilian heart.
- Deoxygenated blood to the right atrium and this drains to the 1st sub-chamber in the ventricle, the cavum venosum.
- When the ventricle contracts, the deoxygenated blood is passed over this muscular ridge into the 2nd sub-chamber called the cavum pulmonale.
- When the ventricle contracts again, blood is pushed into the pulmonary artery to be taken to the lungs to be oxygenated.
- The oxygenated blood will return to the left atrium, which directs the blood into this third deepest sub-chamber, the cavum arteriosum.
- When the ventricle contracts, it pushes the oxygenated blood out through this interventricular canal. Located under the opening of the 2 aortae.
What is the function of the sphincter of the pulmonary artery?
Can close the artery off and divert blood away from the lungs. This is used in aquatic reptiles that are very good at holding their breath, in a reflex action called the diving reflex.
What are the venepuncture sites in snakes?
- Ventral coccygeal vein
- Cardiac puncture in large snakes
- Dorsal palatine vein, located in the oral dorsal cavity
- Jugular cutdown in anaesthetised snakes
Describe the venous and lymphatic systems in reptiles.
Renal portal system present, where any blood draining the caudal part of the body will drain to the kidney first.
Prominent lymph vessels, no nodes
Describe snake lungs.
- Usually 1 functional lung, the right lung
- Cranial lung/faveolate are respiratory where air exchange takes places. Have honeycomb appearance. Faveoli are little pockets or depressions in the lung wall tat open directly into a central airspace. Trachea also opens to this central air space.
- Highly branched bronchial tree system which terminates in the alveolar saccules
- Caudal/membranous part more like air sac and is non-respiratory. No faveoli present
- No diaphragm. But rib movement are important for respiration. Ribs attached to inner surface pf the integument via muscle attachments, and as the ribs move it will help draw air into the lungs.
Describe the lizard cardiorespiratory system.
- 2 faveolate lungs
- No diaphragm so rib movement are important for respiration
- 3 chambered heart
- Renal portal system
What are the venepuncture sites in lizards?
- Ventral coccygeal vein
- Axillary venous plexus – surrounds the shoulder
- Ventral abdominal vein
What is the vasovagal reflex in lizards?
If you apply gentle pressure to the eyeballs, heart rate and blood pressure decrease. Can be made use of when carrying out non-painful procedures such as radiography.
What are the 3 body cavities in tortoises?
- Small pericardial cavity containing the heart
- Larger dorsal cavity containing the lungs
- Larger ventral cavity containing the remaining viscera, including alimentary and urogenital tract structures
Abdominal cavities separated by post pulmonary septum
What are the features of the tortoise upper respiratory tract?
- External nostrils
- Internal nostrils/choanae
- Glottis at the base of the tongue
Describe the tortoise lower respiratory tract.
- Trachea bifurcates immediately caudal to head and is short before bifurcation
- Paired, spongy lungs occupy dorsal cavity
- Lungs attached dorsally to the periosteum lining the inside surface of the carapace and ventrally to post pulmonary septum
- No pleural cavity or diaphragm
What is unique about tortoise ventilation?
- No diaphragm
- No pleural cavity
- No expansion/contraction of ribcage
- So breath is taken by movement of the head and limbs in and out of the shell that aids movement of air
Describe tortoise ventilation.
- Very strong trunk muscles attaches to the limbs that help move them.
- When limbs and head move out of the shell, they alter the internal pressure of the ventral cavity, viscera re pulled downwards, pulling with them the attached post pulmonary septum.
- Lungs are also pulled down and so air is drawn into them.
- The opposite happen in expiration: when the limbs and head are pulled back into the shell, pushes on the viscera, which pushes up against the septum and so the lungs are compressed and air is pushed out.
- When the limbs and head are fully retracted into the shell, the lungs can be compressed to a fifth of their potential size.
What is the disadvantage of the tortoise ventilation?
When the limbs and head are fully retracted, the tortoise cannot breathe very well.
How does tortoise ventilation change in hibernation?
Reptiles, particularly chelonia being very good at breath holding, and being able to switch easily to anaerobic metabolism, have lower oxygen requirements. Obvious limbs and head movements are not needed to move the post pulmonary septum.
Summarise inspiration in tortoises.
- Lungs connected to post pulmonary septum
- Ventral cavity can be moved outwards by serratus and abdominal oblique muscles
- Pulls viscera and hence septum drawing in air
Summarise expiration in tortoises.
- Lungs connected to post pulmonary septum
- Ventral cavity can be compressed by rotating the limbs into shell using pectoralis and transverse abdominis
- Compresses viscera and hence septum expelling air
What are the venepuncture sites in tortoises?
- Jugular vein
- Dorsal coccygeal vein
- Dorsal occipital venous plexus
- Toenail vein
What are the adaptations of snakes for eating large prey?
Cranial kinesis
No mandibular symphysis
Retrograde teeth
Expandable skin
Extendable glottis
Mobile heart
How are retrograde teeth in snakes an adaptation for eating large prey?
Once snake bites into the prey, it is very difficult for prey to escape.
How is a extendable glottis in snakes an adaptation for eating large prey?
Can be extended out the side of the mouth so the snake does not suffocate.
How is a mobile heart in snakes an adaptation for eating large prey?
Can be moved to one side so that cardiovascular function is not compromised while eating large prey.
How do snakes consume large prey without swallowing?
Upper and lower jaws move independently of each other. Snakes walk their jaw along the prey to help them pull it into the mouth. So left side of upper and lower jaw can advance along the prey, bit down and then allow the right side of the jaw to move forwards. Then the left will advance again and then the right.
Why do snakes yawn after a large meal?
To help them reposition their jaw bones.
Describe the dentition of non-venomous snakes, such as boids.
- 1 row of teeth on each side of the mandible
- 2 rows of teeth on each side of the upper jaw
- Retrograde teeth
- Aglyph/restrictor dentition
What are the 3 possible dentition types in venomous snake species?
Ophistoglyph
Proteroglyph
Solenoglyph
Describe ophistoglyph dentition.
Some of the maxillary teeth are modified into rear grooved fangs. In example, the boomslang.
Describe proteroglyph dentition.
Front fangs which are hollow and fixed in position. Example in cobras
Describe solenoglymph dentition.
More complicated arrangement, have hinged front fangs, which can be raised for striking. Normally the fangs are folded away. Vipers are an example.
Describe alimentary system of the snake.
- Simple digestive system
- Oesophagus and stomach are very distensible
- Mechanical and chemical digestion as for mammals
- Elongated liver, can be divided into 2-3 lobes, mainly in middle third
- Prominent gall bladder for fat distension when eating large prey
What is in the cranial 3rd of the snake?
Oesophagus terminates at the stomach. Cranial liver in cranial third but most in the middle third.
What is contained in the middle 3rd of the snake?
- Liver
- Indistinct stomach
- Accessory digestive organs located caudal to the stomach. Sometimes the oval shaped pancreas can be seen caudally to the gall bladder.
- Spleen and pancreas fused in some species to form splenopancreas
- Organ triad – spleen, pancreas and gall bladder located close together
What is contained in the caudal 3rd of the snake?
- Uncomplicated small intestine after organ triad
- Caecum present in some boids
- Large intestine terminates at cloaca/coprodeum
Name the 3 chambers of the cloaca.
Coprodeum
Urodeum
Proctodeum
Describe the urodeum.
Middle chamber. Products of urinary and reproductive systems empty into the here. Ureters and genital tracts drain into the urodeum via opening in the dorsal wall.
Describe the proctodeum.
Most distal chamber. All waste and gonadal product will pass through here on the way to the exterior. Copulation also occurs in this chamber for females.
How does the rectum empty into the cloaca?
- 3 chambers are separated from each other by folds in the mucosal wall
- Receives products from the intestines, kidneys and gonads
- Open to exterior at vent/cloacal opening
- Found in all reptiles, birds, amphibians and monotremes
Describe the alimentary tract of the lizard.
- Most are omnivorous/herbivorous
- Mandibular symphysis so narrow gape unlike snakes but do have cranial kinesis
- Flexible tongue for prehension of food
- Bite off pieces of food unlike snakes
- Teeth simple conical structures so not sockets. Teeth shed regularly
- Simple digestive system
Describe the tortoise oral cavity.
- 25% of chelonia are herbivorous, many omnivorous
- No teeth, sharp ridges on palate to aid swallowing
- Horny beak with sharp edges to enable to bite off bits of food before swallowing
Describe the tortoise alimentary system.
- Oesophagus leads to a small spindle shaped stomach, which leads to the duodenum.
- A small pancreas is visible off the duodenum.
- Remainder of small intestine and then a small less developed caecum.
- Large intestine which narrows as it reaches the rectum.
- Rectum terminates at the copradeum of the cloaca.
- Waste products pass through the urodeum and proctodeum before exiting to the outside through the vent.
Describe the urinary system of the snake.
- Kidneys flank intestine in caudo-dorsal abdomen/caudal 3rd
- Each kidney is brown and elongated
- Right kidney is more cranial than the left so the right ureter is longer than the left.
- Lobulated with 25-30 lobes
- No bladder
- Ureters enter dorsally into uroderm portion of the cloaca
Describe the snake testis.
- Fusiform testes cranial to kidneys
- Right teste more cranial than the left
- Testes are pale structures which have a spindle like shape
- Enlarge and regress as season changes
- Male snakes also have sexual segment in kidney, which also enlarges in the breeding season and helps to produce seminal fluid.
Describe the structure of hemipenes.
- Paired, sac-like caudal extensions of cloaca
- Lie in the ventral tail base when not in use, caudal to the vent
- When they become engorged, they vert out of the cloaca and inserted into the proctodeum portion of the female cloaca.
- Each hemipene receives sperm from the testis on the same side of the body.
Describe adaptations of hemipenes for their function.
- At ejaculation, the sperm travels along a surface groove in the hemipene called the sulcus spermaticus.
- Retractor muscle withdraws hemipene after mating (lasts 20 hours) when engorgement subsides
- Barbs/ridges in some species, thought to allow to stay in female for such long periods. Some snakes will alternate hemipenes during successive copulations
Describe how the hemipenes is involved in sex determination of snakes.
Sexing using hemipenes by gently inserting a probe caudal to the vent. If it goes in approximately 6 subcaudal scales, it is male. If it goes in 2-3 subcaudal scales, it is female.
Describe the female reproductive system in the snake.
- Ovaries asymmetrically placed near pancreas
- Right more cranial than left
- Saccular, covered in follicles
- Oviducts provide egg transport and secrete albumin, protein and calcium for shell formation in tortoises. Have plated ribbon appearance.
- Some females can store sperm for months/years so can become pregnant under the right conditions even with no male present.
Describe the lizard urinary system
- Lobed kidneys, shorter ureter
- Modified cloaca
- Most have a thin bladder for urine storage
Describe the male reproductive system in the lizard.
- Testes cranial to kidney and intraabdominal
- Sexual segment of kidney in some species
- Paired hemipenes, seen as bulges proximal to the tail
Describe the female reproductive system in the lizard.
- Paired ovaries and oviducts with pleated ribbon appearance
- Cranial to kidneys
- Pleated oviduct
Describe the urinary system in the tortoise.
- Paired kidneys and large, flat, lobulated, symmetrically placed and located very caudally
- Urine drains via ureters and urogenital sinus to uroderm and then to bladder
- Bladder is large and bilobed
Describe the structure of the male reproductive system in tortoises.
- Pale, oval shaped testes
- Black pigmentation of peritoneum surrounding epididymis
- Engorgement of fibrous/vascular tissue on cloaca floor in proctodeum forms penis
- Protrudes out of vent
Describe the tortoise penis during coitus.
There are 2 strips of tissue with a groove in between. When these strips become engorged, they fold over and meet to form a tube-like structure. This protrudes out of the vent and can be inserted into the proctodeum of the female. Sperm will travel down the inside of the tube to reach the female. When engorgement subsides, there is a retractor penis muscle which helps pull it back inside the cloaca.
Describe the components of the female reproductive tract in the tortoise.
- Paired ovaries – cranial to kidney symmetrically
- Oviduct divided into various parts
- At egg laying, the vagina will relax to allow the passage of the ova out of the urogenital sinus and then into the urodeum portion of the cloaca and then through the vent.
Name and describe the parts of the oviduct in the tortoise.
Infundibulum – funnel shaped and covers part of the ovary
Magnum – longest part and has a characteristic twisted ribbon appearance. Secretes albumin.
Uterus – more cylindrical and muscular. Provides the membranous and calcareous parts of the egg.
Vagina – pronounced muscular wall. Holds the tract tightly closed until the tortoise is ready to lay its eggs.
Name and describe 2 possible reproductive problems in female tortoises.
Pre-ovulatory egg stasis – egg follicles are formed on the ovaries but not ovulated
Post ovulatory egg stasis – egg bound. Eggs stuck due to damage/disease of reproductive tract or stress
In lizards, which structures does the bladder drain into?
Urodeum
What is not an anatomical respiratory feature of reptiles?
Diaphragm
