Chapter 8 Reptiles: Morphology, Reproduction, and Development



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楊懿如 第 頁 2017/2/6

Chapter 8 Reptiles: Morphology, Reproduction, and Development

INTRODUCTION

16150 of 53000 species of vertebrates

turtle: 230 species

tuataras: 2 species

lizards: 3900 species

snakes: 2400 species

crocodilians: 21 species

birds: 9600 species

TURTLES, TUARARAS, LIZADS, AND SNAKES

MORPHOLOGY

Integumentary System

Scales: from epidermal layers, protection and reduce water loss

Scute: aid in locomotion (bellies)

Shell of dermal plate of turtle Fig. 8.1,

Shields or scutes (horny scales cover)

Fig. 8.2, 8.3 ecdysis : the stratum corneum is lossened, stratum germinativum produce new cells

Few glands: musk, femoral, pre-anal, cloacal, and nuchodorsal gland, for species and sex recognition (pheromones)

Modification of epidermis: scales, claws, rattles, horny protuberance, and spine

Fig. 8.4a, b toe pads of geckos

C rattle

Turtle: carapace (dorsal), plastron (ventral), lateral bridge

Chromatophores: color pattern

Coloration: protective (camouflage and warning), dominant social status, sex recognition, thermoregulation

Spotted pattern: feign immobility

Stripes: flee

Skeletal System

Modifications for muscle attachment, varied dietary habits, and terrestrial locomotion

Fig. 8.5 snake vertebrae up to 500

Caudal autotomy: defense mechanism, regenerate

Ribs of turtles fused with carapace

Ribs of tuatatas bear uncinate process

Methods of locomotions

Fig. 8.6(a) sprawled posture (b)placental mammal

Modification of aquatic reptiles Fig.8.7

Snakes evolved from lizards

Fig. 8.8 Boidae possess vestigial pelvic girdles and/or rear legs

Different stages of reduction and loss of limbs in lizards

Snake locomotion Fig. 8.9

Horizontal undulations

Concertina

Rectilinear

Sidewinding

Muscular System

More differentiated and better adapted to terrestrial life

Cardiovascular System

Three different modes of circulation Fig. 8.10

Reptilian erythrocytes are oval and nucleated

Respiratory System

Formation of secondary palate

Snakes have a glottis that can be protruded

Most reptiles are voiceless

Lung of turtles and lizards Fig. 8.12 Faveoli

Lungs of snakes are elongate and may be paired or unpaired

Force-pump system

Backward and forward movements of the ribs

Other gas exchange membrane

(1)Pharyngeal (buccopharygeal )

(2)Cloacal

(3)Cutaneous

deepest diver: high oxygen-carrying capacity

cobra: inflate their neck via a large saclike divertidulum of the left lung

sea snake: submerged for 8 hours, take oxygen through skin

salt gland: desert species, assist in humidifying incoming air

inflating lungs: defense

Digestive system

Numerous modifications

Turtles: beak

Oral Cavity

Possess teeth on the palate and jaws

Homodont dentition

Tooth attachment:Fig. 8.13



  1. Acrodont

  2. Pleurodont

  3. Thecodont

Fig. 8.14 snakes’ mandibles joined by elastic ligament, lower jaw are suspended from the skull by quadrate, alternately engaging and disengaging the teeth on each side of the mouth

Threadsnakes: mandibular raking, lower jaw rotate rapidly in and out

BIO-NOTE 8.1 Living on Large Prey Fig. 8.15 consume 50-160% of their own body weight

Venomous lizards: Gila monster and Mexican beaded lizard, neurotoxic

Venom: salivary gland

Opisthoglyphs: rear-fanged snakes

Proteroglyphs: grooved fang, Elapidae, neurotoxin

Solenoglyphs: hollow elongated fangs, Viperidae, hemolytic poison

Envenomation

Geographical variation in venom composition

Reptilian tongue Fig. 8.17 paired vomeronasal (Jacobson’s organ)

Fig. 8.18 ficking

Esophagus

Fig. 8.19 egg-eating snake have esophageal teeth

Stomach

Elongate in lizards and snakes Fig. 8.20 Cecum contains specific bacteria



BIO-NOTE8.2 Insights from Gastroliths

Fig. 8.21 stomach stones

Nervous System

Table 8.1 weights of brain and body in a variety of vertebrates

Hypothalamus acts as a thermostat to control body temperature: basking poikilothermy Fig. 8.22

Sense Organs

Cutaneous Receptors

Loreal pits: Viperidae and boas, heat-sensing structures

Ear

Snake have no external ear openings, quadrate bone acts as receiving surface for the aerial sounds



Eye

Fig. 8.23 spectacle: upper and lower eyelids are permanently united

Nictitating membrane

Lacrimal gland

Chameleon eyes move independently

Parietal eye: temperature regulation, daily and annual body rhythms

Nose

Vomeronasal organs Fig. 8.24



Taste

Poor


Endocrine System

Fig. 8.25(a) oviduct-albumen, egg shell, spermathecae

Fig. 8.26 hemipene: lizard and snake

Fig.8.27 turtles have an unpaired penis

Reproduction

Reproductive behavior is influenced by temperature and photoperiod

Vision and olfaction

Courtship behavior

Fig. 8.28 Dewlap of male anole

Lipids extracted from the skin of female garter snake Fig. 8.29

Lipid stored in abdominal fat body

Oviparous

Viviparous

Multiple copulations

Breeding cycle

Parthenogenesis: all female

BIO-NOTE 8.4 Courtship in a Unisex Lizard

GROWTH AND DEVELOPMENT

Parental Development

Fig. 8.30 deposit eggs on land

Fig. 8.31 most reptilian eggs are enclosed in a leathery shell

Duration of Embryonic Development

Incubation period: 5 weeks to 16 months

Hatching and Birth

Caruncle: egg tooth

Temperature-dependent sex determination

Type A: male, high temperature

Type B: female, high temperature

Type C: female, high and low temperature

Parental Care

Parental care is rare in reptiles

Fig. 8.32 Indian pythons coiled around eggs, increase body temperature by contracting their body muscles



Attainment of Sexual Maturity 4 months-11 years

Longevity: Table 8.2 over 150 years


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