I saw this crown-of-thorns star working its way across the rocks in shallow water. Those spiky spines are venomous so this is not something to handle. Also visible in this photo are some equally spiky, though not poisonous, rock-boring urchins
Posted in response to Becky’s October Squares challenge theme of ‘Past Squares – Spiky.’ See more responses here.
According to my marine invertebrates book, collector urchins (Tripneustes gratilla) gather algae, shells, and other material on their spines. Why they do this is not entirely clear. It might be for disguise, protection from the light, or even to store food. These urchins are quite common in the shallows and their adornments are many and varied.
Posted in response to Becky’s October Squares challenge theme of ‘Past Squares – Spiky.’ See more responses here.
I was amused by this sign on the beach in front of the Four Seasons Resort Hualalai. Spiny urchins in the rocks are like white lines on the highway. But of course, a visitor is not necessarily aware of this and the Four Seasons wouldn’t want any of its guests impaling themselves on spiky marine life, especially if they were likely to complain about it later.
This sign wasn’t far from another one that basically said you’d die if you set foot on the beach (here). Perhaps this was why the very lovely beach was deserted when I was there.
This scene drew my attention because of the smooth, round rock nestled into a matching recess in the shore (bottom left in the top photo). It was when I zoomed in (bottom photo) that I noticed the large number of helmet urchins stuck to the shoreline. These cheerful-looking purple blobs live in the harsh tidal zone, and area of crashing waves and surging water. They feed on algae that grows there.
In the middle photo, an a’ama crab skirts a colony of urchins. When the tide comes in, the crab will move to higher ground, but the urchins will stay put, tenaciously defying everything the ocean throws at them.
A bright-eye damselfish guards its territory, which includes this red pencil urchin, against intruders.
A little snapshot of things tucked into the rocks along the Big Island. There’s a red pencil urchin and blue-black urchin, a patch of cauliflower coral, and a cowry, probably a reticulated cowry. And if you look closely, there’s a bright-eyed damselfish swimming between the coral and red pencil urchin.
Achilles tangs are surgeonfish, with a scalpel near the base of the tail, in the aft end of the large orange-red spot. They’re quite common in shallow waters near the surge zone. This one is passing over a patch of coral, dotted with red pencil urchins.
Redbarred hawkfish, like other hawkfish, spend most of their time perched motionless on a rock or coral head, waiting to dart out at passing prey, usually little fish or small crustaceans. On some fish, the bars are more of a brick red, similar to the color of the red pencil urchin on the left of the photo.
Graham's Island 