Boy, these guys are tough to photograph; they're agile and fast as lightning. You'd be too if you were a tasty little pupu favored at luaus and graduation parties. This is the 'a 'ama crab, Grapsus tenuicrustatus, also known as the thin-shelled black crab, rock crab, or natal lightfoot crab. Like the nearly two-hundred types of crabs here in Hawaii, they are ten-leggers, with the front pair bearing stubby chelae, or claws. Their carapace is flattened, as are their legs, making it easier for them to slip into the cracks and crevices, and to flatten out against the rock when a big waves splashes in. Algae is what motivates them to brave the intertidal zone, but they'll scavenge as well, keeping the beach clean and tidy. It's not uncommon to find their reddish molted shells, which are this color because the chromatophores, or pigment-bearing cells are no longer alive, leaving the shell to reveal its natural coloration. People use an ahele to catch them, a V-shaped tool on the end of a long pole. Thin line connects the points of the V, and is used to snare the cautious but curious crabs by the eye stalks. |
4 Comments
6/20/2018 05:01:10 pm
Not sure if this site's still active, but since it's up I'll give it a go. Your post on 1-12-14, hot-rod decapod, has a photo at the bottom of some cream-colored shells in a tide pool. I was wondering if you know what they are as I'm trying to identify similar shells I photographed yesterday.
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Jeanne Lindgren
6/21/2018 12:18:01 am
Hi Graham,
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6/21/2018 03:40:00 pm
You're right, it is Padina japonica. I was down at the coast yesterday having a closer look and realizing they weren't shells, but your response has saved me some time trying to figure out what else they could be.
Michaela A. Hastings
12/11/2018 10:38:20 am
Hi! I'm doing a report on the 'A 'ama Crab and was wondering by any chance you knew the average size of them. Thank you!
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