CHAPETER 5 EARLY CRANIATE MORPHOGENESIS
Bianca Amisola
3Bio5
CHAPTER 5 – EARLY CRANIATE MORPHOLOGY
CRANIATE EGGS
Egg Types:
1. MICROLECITHAL – little yolk
Amphioxus and placental Mammals
2. MESOLECITHAL – moderate amount of yolk freshwater Lamprays, basal Actinopterygian and Neopterygian fishes, Lungfishes and Amphibians
3. MACROLECITHAL– massice amounts of yolk marine lampray. Elasmobranchs ,Teleosts, Reptiles and Monotremes
Egg Distribution:
1. ISOLECITHAL – yolk with even distribution of yolk (Microlecithal eggs)
2. TELEOLECITHAL – yolk tend to accumulate at opposite poles Vegetal pole – Mesolecithal & Macrolecithal the large yolk tends to be concentrated at one end Animal pole – containing the nucleus and relatively yolk-free cytoplasm
Oviparity and Viviparity
OVIPAROUS – animals that spawn and lay eggs eggs contain sufficient nourishment in the form of yolk, and sometimes albumen to support development into a free-living organism that is able to take food orally massive yolk: young hatch essentially fully formed (i.g. birds) less yolk: hatch in a larval stage (i.g. frogs) little yolk: the free-living, self-nourishing stage must be achieved very quickly after the egg is deposited (i.g. ampioxus egg)
VIVIPAROUS – animals that give birth to offspring embryo is dependent on the mother for all nourishment, for oxygen, and for carrying away waste products of metabolism (i.g. placental mammals) no viviparous crocodile and turtles
20% of lizards and snakes (squamata) are viviparous urodels and anurans are viviparous if on land
OVIVIPARITY – viviparous condition where the developing embryo receives maternal protection and oxygen from mother but nourishment has been stored in the egg
Shark, dogfish shark (Squalus acanthias) EUVIVIPARITY – the viviparous condition in which the embryo cannot develop without nourishment being constantly supplied by the mother from maternal tissue
Placental mammals
*HISTOPROTIC (embryotrophic) Nutrition – term applied to nutrition by glandular secretions
3Bio5
CHAPTER 5 – EARLY CRANIATE MORPHOLOGY
CRANIATE EGGS
Egg Types:
1. MICROLECITHAL – little yolk
Amphioxus and placental Mammals
2. MESOLECITHAL – moderate amount of yolk freshwater Lamprays, basal Actinopterygian and Neopterygian fishes, Lungfishes and Amphibians
3. MACROLECITHAL– massice amounts of yolk marine lampray. Elasmobranchs ,Teleosts, Reptiles and Monotremes
Egg Distribution:
1. ISOLECITHAL – yolk with even distribution of yolk (Microlecithal eggs)
2. TELEOLECITHAL – yolk tend to accumulate at opposite poles Vegetal pole – Mesolecithal & Macrolecithal the large yolk tends to be concentrated at one end Animal pole – containing the nucleus and relatively yolk-free cytoplasm
Oviparity and Viviparity
OVIPAROUS – animals that spawn and lay eggs eggs contain sufficient nourishment in the form of yolk, and sometimes albumen to support development into a free-living organism that is able to take food orally massive yolk: young hatch essentially fully formed (i.g. birds) less yolk: hatch in a larval stage (i.g. frogs) little yolk: the free-living, self-nourishing stage must be achieved very quickly after the egg is deposited (i.g. ampioxus egg)
VIVIPAROUS – animals that give birth to offspring embryo is dependent on the mother for all nourishment, for oxygen, and for carrying away waste products of metabolism (i.g. placental mammals) no viviparous crocodile and turtles
20% of lizards and snakes (squamata) are viviparous urodels and anurans are viviparous if on land
OVIVIPARITY – viviparous condition where the developing embryo receives maternal protection and oxygen from mother but nourishment has been stored in the egg
Shark, dogfish shark (Squalus acanthias) EUVIVIPARITY – the viviparous condition in which the embryo cannot develop without nourishment being constantly supplied by the mother from maternal tissue
Placental mammals
*HISTOPROTIC (embryotrophic) Nutrition – term applied to nutrition by glandular secretions