svg marker : arrow

<style>
path#curve1 {
transform-origin:50% 50%;
animation:anim 5s ease-in-out infinite;

}
@keyframes anim {
0% {transform:rotateZ(0deg);}
100% {transform:rotateZ(359deg);}

}
</style>

<svg viewBox="0 0 20 20">
  <defs>
	<marker id="arrow" viewBox="0 0 10 10" refX="5" refY="5" markerWidth="6" markerHeight="6" orient="auto-start-reverse">
		<path d="M0,0 l10,5 -10,5z" />
	</marker>
  </defs>

  <path id="curve1" d="M10,10 c2,-5 3,-7 4,-3"  marker-start="url(#arrow)" marker-end="url(#arrow)" fill="none" stroke="green" stroke-width=".1"/>
</svg>