Category Archives: Marine Invertebrates

Morning swim

A spotted eagle ray swims in the waters off Hawaii
Spotted eagle ray swimming
A spotted eagle ray hunts in the waters off Hawaii
Spotted eagle ray hunting

On a morning swim with my wife a couple of days ago, we were lucky enough to see a spotted eagle ray cruising around looking for breakfast. It stopped often, to probe the sand and rocks for food, and was successful at least once, since it emerged from its efforts chewing and swallowing. This eagle ray looked a bit battered, with damage to its tail fins and a chunk missing from its right wing, but it didn’t seem to be affected by this at all.

As we continued swimming, I saw the ray heading the same way. For a while it followed us, got ahead, then we followed it. On the way we saw a couple of flowery flounders, a couple of day octopuses, a crowned jellyfish as roughed up as the ray, and an oriental flying gurnard. It’s not a great photo of that, but it’s the first one I’ve seen here.

Near the spot where we planned to turn around and head back, I passed over a hole in the rocks and, glancing down, saw the distinctive shape and colors of a green turtle. I think it must have chosen this spot to take a rest, but my appearance startled it and it clambered out of the hole and swam away.

  • A Green turtle resting in a hole in the waters off Hawaii
  • A Green turtle emerges from a hole in the waters off Hawaii
  • A Green turtle swims in the waters off Hawaii

Shortly after that, the turtle encountered the eagle ray. The two of them crossed paths a couple of times before going their separate ways.

A Green turtle and spotted Eagle Ray in the waters off Hawaii

Cushion stars

A cushion star in the waters off Hawaii
A red cushion star in the waters off Hawaii

Cushion stars (Culcita novaeguineae) look just like their name implies – small but comfy-looking cushions that would not look out of place on your couch. However, these cushions would move around on their little tube feet, which might be a bit disconcerting.

They come in several colors including red, yellow, and tan and there’s often quite a bit of variety in their markings. Cushion stars feed on living coral, which they eat by pushing their stomach out and consuming the coral where it sits.

Seven-eleven crab

A Seven-eleven crab off Hawaii

I’ve only seen one or two seven-eleven crabs (Carpilius maculatus) before, and not for several years. My wife had never seen one. One reason for this is that the crabs are active at night. But we saw this one a few days ago, scuttling over the rocks and sand. It was quite early in the morning, so the crab was probably headed for its home.

These crabs are quite large and have the distinctive markings that give it its name. There are the two spots alongside each eye and three across the center of the shell. Four more spots are less obvious on the back edge of the shell.

In Hawaii, these crabs are called ‘alakuma. Legend has it that a god caught an ‘alakuma, but the crab struck back and drew blood. This happened a second time, before the god finally snagged the crab. But the crab’s descendants continue to bear the markings of the god’s bloody fingerprints.

Stick swimming crab

A stick swimming crab in the waters off the Big Island, Hawaii

This month, Becky’s April Squares challenge theme is ‘Bright.’ (See more responses here.) First up I thought I’d share something very unusual, which I consider myself lucky to have seen.

You’ve probably heard of stick insects, but the stick swimming crab is a far less often encountered creature. Most crabs scuttle about on the sea floor, but swimming crabs have flattened segments on their legs, which they use to propel them through the water. But even with this different method of propulsion, swimming crabs tend to stay close to the bottom.

The stick swimming crab (Charybdis baculum) has a different approach. It heads for the bright light at the surface where it paddles along, maneuvering with its spindly legs. It will sometimes snag bits of floating debris and attach them to its body to enhance its appearance. Its goal is to look like a small, drifting haven for juvenile fishes and other marine organisms that often gather under such floating islands, which offer them some protection from predators. With the stick swimming crab, that safety is an illusion. Instead, they’re part of the crab’s lunch box, to be picked off at its leisure.

Stick swimming crabs spend most of their time at the surface, but return to the sea floor for periodic molts. This one looks like it has recently molted.

Oh wait, it’s just a stick.

Also posted in response to this week’s Friendly Friday challenge theme of “Something Learned.” See more responses here.