Our photo of the day comes from Middle Head, Sydney Harbour, Australia.
Photographer John Turnbull describes this striking photo of a sponge and a giant sea tulip ascidians (Pyura spinifera) as "Sponge and not sponge." He explains:
"The animal on the left is a simple one – a sponge, which has no distinct organs and merely filters water for its food. On the right in pink is an ascidian – more complex, with an animal living inside each "tulip." Ascidians have a rudimentary spinal cord in their larval stage (notocord) and body parts such as a heart, stomach, intestines and enlarged pharynx which they use to also filter food from seawater."
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