EEB267H1 Lecture Notes - Lecture 6: Collagen, Ichthys, Endoskeleton
24 Jan 2017
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Oviparous + lecithotropic (some sharks, all skates, all ratfishes: oviparous. Ovum [egg] + parere [to bring forth] Deposit egg outside of female into case made of keratin called the mermaid"s purse covers and protects egg: lecithotrophic ( yolk-eating ) Each egg has lots of yolk embryo eats the yolk: pups are relatively small at birth no parental care of egg cases or pups. Viviparous + lecithotropic (many shark species: viviparous. Viva [alive] + parere [bring forth: developing embryos are retained inside mother, but she provides no additional nutrition other than the yolk, mother gives birth to relatively small pups. Vivaporous + matrotrophic (most sharks and all rays: matrotrophi. Pup lives off of yolk for a few weeks. When yolk is almost gone, yolk sac elongates and forms a connection with the uterus yolk sac placenta. Nutrients transferred from mother to pup via placenta: oophagy (threshers, whites, makos) Pup lives off of yok for a few weeks.
