Emerita analoga (Stimpson, ). Common name(s): Pacific sand crab, sand crab, mole crab. Synonyms: Hippa analoga, 3 cm preserved female. Scientific Name. Emerita analoga. Animal Type. Invertebrates. Diet. plankton, mostly dinoflagellates. Size. females: to 2 inches ( mm); males inches. Pacific Sand Crab (Mole Crab). Emerita analoga. Decapoda: Hippidae. Laguna Beach, Orange County, CA. 06/11/ © Peter J. Bryant. Back to Natural History.
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The Pacific sand emerlta is one of the few species specializing in the swash zone of wave-swept sandy beaches. Its body is approximately egg-shaped. The carapace has three teeth in front and is smooth except for small, transverse ridges on the anterior portion. The first 4 pereopods are flattened, not chelateand used for digging. The fifth pereopod is slender and chelateand is used for cleaning the gills rather than for digging.
The antennal flagellum is long and featherlike used for filter feedingbut is folded beneath the mouth parts emeriya not being used. Carapace length to 3.
The abdomen with its elongated telson photo is generally held reflexed underneath the thoraxbut is extended for rapid digging into the sand movie. Ansloga abdominal segments become successively smaller posteriorly photo but the elongated telson is large and arrowhead or long spade-shaped photo.
Both sexes have well-developed uropods but only females have pleopods 3 pairs. Carapace is gray or greenish in color.
Week # 5: Pacific Sand Crab, Emerita analoga
The underside is nearly white. How to Distinguish from Similar Species: This is the only local species of Emerita. It differs from the spiny mole crab, Blepharipoda occidentaliswhich has spines on its carapace and pereopods and typically lives lower in the swash zone in California. Alaska but analogaa north of Oregon to Chile; Argentina.
Migrate up and down with the tides on sandy, wave-swept beaches.
WoRMS – World Register of Marine Species – Emerita analoga (Stimpson, )
Inhabit the swash zone where the waves sweep up the beach and then retreat again. This species is abundant on some California sandy beaches but is not often found as far north as Washington. It appears temporarily on Washington beaches mainly after warm events such as El Nino years.
The species is a motile filter-feeder which inhabits the upper surf swash zone on sandy beaches. When a wave sweeps in, the animal pops up and rides the wave for a few feet; then it quickly burrows rear-first into the sand using its abdomen movie. As the wave retreats it extends its long, feathery antennae and captures plankton and detritus from the retreating wave. Within a wave or two it will again pop up and ride the wave to a new spot; thus remaining in the swash zone as the tide advances and retreats along the beach.
The species primarily inhabits beaches with clean, pebble and stone-free sand.
It can be detected when it pops up in shallow water behind the latest advancing wave, and also by the V-shaped wake its antennae make as it filters the retreating analiga. General Notes and Observations: Locations, abundances, unusual behaviors: I found many juveniles on the beach at Kalaloch, most less than 1 cm total length.
Two views of the ventral side of a 3 cm carapace length preserved female from Monterey Bay, CA. The left view shows the normal position of the abdomen and telson.
On the right, the telson is held out to reveal the eggs held on the pleopods. Note that the normal color has faded since this is a preserved specimen. Dorsal and ventral views of a preserved male, 2. In both views the abdomen has been artificially extended.
Note the lack of pleopods on the abdomen. Since this is a preserved specimen the true color has faded. A closeup view of the head of the 3 cm carapace length preserved female. Click Here for a movie of a 1. Total animal length is 4. Photos by Dave Cowles Dorsal view. Note how the carapace is egg-shaped and the animal keeps its legs and other appendages folded underneath, maintaining a 3-dimensional egg-like contour.
The head is to the right in this photo. Note how the abdomen with lits arge, pointed telson is folded loosely underneath the body. The abdomen and telson are used for rapid digging into the emeerita as each wave begins to recede. She is carrying a batch of orange eggs on her pleopods underneath the telson. Her head, with its feathery antennae, is on the right.
Emerita (genus) – Wikipedia
Authors and Editors of Page: Emerita analoga Stimpson, Common name s: A preserved female, 3 cm carapace length, collected at Monterey Bay. Note that the normal gray color has faded because this is a preserved specimen. This female is carrying eggs see photo below. Photos by Dave Cowles.