Diving the Kona Coast: July 2010

Monday, July 26, 2010

Rainbow Swimming Crab

I know I haven't been posting much in the way of fish photos recently, but I've just been having great luck finding fascinating invertebrates. This past weekend the surf was almost non-existent at Honaunau Bay which allowed me to explore some lava tubes along the northern shoreline. In the last tube I found a pair of these vividly colored Rainbow Swimming Crabs. Swimming crabs are unique in having a flattened pair of hindmost legs. When pumped furiously, these legs propel the crab awkwardly up into the water column although this action only loosely resembles swimming. It is probably an adequate defense against some of the slower predators it may encounter.

I found two of these crustaceans in separate locales within the same lava tube. Unfortunately, another bad aspect of my new SeaLife DC1200 camera is that it drains batteries very quickly. Battery power died during my session with these creatures, but I did get a couple decent images.

Wednesday, July 21, 2010

Hawaiian Swimming Crab

I just wanted to share this image of a tiny juvenile Hawaiian Swimming Crab I took last weekend. I've often seen photos like this on the web or in magazines but never thought I'd actually take one myself. The odds of getting the flash on the critter just seemed beyond my level and luck. Anyway, I'm just happy with this result.

This photo was taken with a new SeaLife DC1200 camera. I'm not too thrilled with it just yet. Macro shots (like this) are pretty good, the "normal" focus is mediocre and getting good photos of big animals is almost impossible. Maybe things will get better with more experience. Anyway, I'm pleased with this pic!

Sunday, July 18, 2010

Tiger Cowrie encounter

Last week I was lucky enough to come upon a Tiger Cowrie actively making its way across the reef during daylight hours. I often find Tiger Cowries during the day but the animals themselves are all drawn up into the shells. The few times I've seen the actual living animal has been on night dives years ago.

When the animal is active, a thin layer of tissue slides up over the shell. This is called the mantle and is greyish in color having many little projections called papillae. In the photo above, The mantle is extended from the underside and a small slice of uncovered shell is visible on top. The mantle is responsible for the glossiness of the cowrie shell as it protects and polishes the surface.

Here, the shell is completely enveloped by the mantle as the snail cruises among the coral peaks.

Looking at the animal head-on in this photo, you can see that on the left side, the mantle is almost all the way up, while on the right side a good part of the shell is exposed. Note the bright white line down the shell's center. This is the point where the two halves of the mantle meet.

In this last photo you can see the "spiky" appearance the papillae give the cowrie. These projections serve a sensory function giving the snail additional information about its environment.