ECOL /14/2016. Evolution of Animal Form & Function. Dr Alex Badyaev. Lecture The interaction of egg and sperm:

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1 Evolution of Animal Form & Function Dr Alex Badyaev Lecture ECOL 330 The interaction of egg and sperm: 1. Chemo attraction of the sperm to the egg by soluble molecules secreted by the egg The interaction of egg and sperm: 2 or 3. Exocytosis of the acrosomal vehicle to release its enzymes 3 or 2. The binding of sperm to the extracellular envelope of the egg The interaction of egg and sperm: 4. The passage of sperm through the extracellular envelope 5. Fusion of egg and sperm membranes 1

Not just activation, but also attraction When sperm added to oocytes that had not completed

sea urchin Arbacia punctulata a chemotactic 14 amino acid peptide resact.

attraction and activation Drastic and immediate increase in mitochondrial respiration and,

Sperm Exceptionally rapid evolution of binding sites Mostly sperm evolution Mostly brain

2 Not just activation, but also attraction When sperm added to oocytes that had not completed 2 nd meiotic division no attraction, but great attraction to mature oocytes (Miller 1978) In sea urchin Arbacia punctulata a chemotactic 14 amino acid peptide resact. Adding 1 nl of resact strongly modifies sperm movement and taxis (Ward et al 1985) Sperm attraction and activation Drastic and immediate increase in mitochondrial respiration and, thus, motility. Different peptides for different species. Resact only attracts sperm of A. punctulata. Exceptionally rapid evolution of binding sites before 20 sec after 40 sec after 90 sec after Sperm attraction and activation Drastic and immediate increase in mitochondrial respiration and, thus, motility. Different peptides for different species. Resact only attracts sperm of A. punctulata. Exceptionally rapid evolution of binding sites Mostly sperm evolution Mostly brain evolution 2

many other animals) but on the side of the

Gene knockout experiments on interaction

infertile because their eggs fail to fuse

microinjection of mrna from either human

mammals second meiotic division is after

block The FAST block (sea urchin) Changing

3 Gamete fusion in mammals 1. Once sperm traveled to the egg the fusion can begin 2. Sperm contact egg not at its tip (as in many other animals) but on the side of the head 3. Gene knockout experiments on interaction between a sperm and CD9 protein produced by an egg. Female mice carrying knockout for CD9 are infertile because their eggs fail to fuse with sperm (Evans 2001) Reversed by microinjection of mrna from either human or mice CD9 (Kaji et al 2002) in most mammals second meiotic division is after sperm entry 1) The FAST block 2) The SLOW block The FAST block (sea urchin) Changing the electric potential of the egg cell membrane (for about 1 min) Resting membrane potential: 70mV (inside is negatively charged). Within 1 3 sec of sperm entry shifts to +20mV (Jaffe 1976) The FAST block (sea urchin) Polyspermy can be induced is eggs are supplied with an electric current that keeps the membrane potential negative. 3

The SLOW block (within minutes of fertilization The fast block is not sufficient to

Cortical granules of egg (analogous to acrosomal vehicles of sperm).

space between the egg membrane and the extracellular envelope of the egg.

2) Mucopolysaccharines produce osmotic gradient and that causes water to rush in

3) Peroxidase enzyme hardens the envelope forming shell 4) Hyalin protein that

noticeable (very early) spontaneous abortion.

After implantation (i.e., when pregnancy can be detected) rates much lower: 1-2% in

independently of copulation - most -Induced by either copulation or other external

4 The SLOW block (within minutes of fertilization The fast block is not sufficient to prevent polyspermy permanently. Removal of sperm from the egg surface. Cortical granules of egg (analogous to acrosomal vehicles of sperm). Cortical granules fuse with the egg membrane and release their contents into the space between the egg membrane and the extracellular envelope of the egg. Release: 1) A protease dissolves the protein binders of sperm (clips off the sperm) 2) Mucopolysaccharines produce osmotic gradient and that causes water to rush in and forms swelled fertilization envelope. 3) Peroxidase enzyme hardens the envelope forming shell 4) Hyalin protein that forms coating around the egg Major selection on pre-implantation stage: >30% of not noticeable (very early) spontaneous abortion. You are pregnant 30% times more frequently than you think you are. After implantation (i.e., when pregnancy can be detected) rates much lower: 1-2% in women years 7-10% in women over 35 years Ovulation mammals -Spontaneous and independently of copulation - most -Induced by either copulation or other external factors Flowers for ovulation Montane vole (Microtus montanus).. need copulation to ovulate Sanders, E. P. et al methoxybenzoxazolinone: a plant derivative that triggers ovulation in Microtus montanus. Science 214,

5 Reproductive variations in mammals 1. Delayed fertilization many bats Young born in early summer when insects are abundant Reproductive variations in mammals 2. Delayed development many bats the blastocyst implants but develops very slowly (7 months and more). Synchronization of birth of multiple kids and fruit season Reproductive variations in mammals 3. Delayed implantation many species blastocyst development and implantation is arrested (many months) Both: 12 months 5

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Development: is the growth of an individual organism from a simple to a more complex or mature level. A slow process of progressive change

Development: is the growth of an individual organism from a simple to a more complex or mature level. A slow process of progressive change 1. Define the following terms (use your own words): development, growth, differentiation, histogenesis, organogenesis, morphogenesis, reproduction, tissue, organ, organ system, and organism. Development: