Ampithoe dalli Shoemaker, 1938

Common name(s): Speckled beach hopper

Synonyms: Ampithoe dalli (?)
Phylum Arthropoda 
Sybhylum Crustacea 
Class Malacostraca 
Subclass Eumalacostraca 
Superorder Peracarida 
Superfamily Corophioidea 
Family Ampithoidae  
A male Ampithoe dalli, 1.7 cm long, found on eelgrass in Padilla Bay
(Photo by:  Dave Cowles, July 2014)

Description:  As is characteristic of Family Ampithoidae, this gammarid amphipod has a biramous 3rd uropod, both rami of which are shorter than the peduncle (photo).  The outer ramus of uropod 3 has two curved teeth at the apex, while the inner ramus has setae plus spines (photo).  The outer lobe of the animal's lower lip has a deep cleft.  This species has no accessory flagellum on its antennules.  Antenna 2 is longer than antenna 1 and is not thickly covered with setae.  The palm of gnathopod 1 is definitely oblique and the gnathopod is subchelate (photo).  The second gnathopod (photo) is larger than the first, and its sixth article (palm) is ovate and oblique.  The second article of pereopods 3 and 4 are rectangular and less than 1/2 as wide as their coxal plates (photo).  The posteroventral corner of the second and third epimera are not toothed (photo).  The antennae and uropods have just a few short setae.  Uropods 1 and 2 do not have a distal tooth on the peduncle.  Greenish or brownish with darker speckles.  Males to 1.8 cm, females to 2 cm.

Note:  Although this individual is male, the 2nd gnathopod has only a shallow concave spot instead of being broadly concave as is expected of this species, so the identification is only tentative.

How to Distinguish from Similar Species:  A. sectimanus is similar but has many long setae on its antennae and uropods, plus gnathopod 2 has only a narrow excavation.

Geographical Range:  Alaska to California

Depth Range:  Intertidal and shallow subtidal;

Habitat:  Algae and eelgrass

Biology/Natural History:  This species can survive in less than full seawater salinity (eg in outer estuaries).  Females may be carrying eggs during March to August.



 

References:

Dichotomous Keys:
  Carlton, 2005
  Kozloff, 1987, 1996

General References:
  O'Clair and O'Clair, 1998

Scientific Articles:

Web sites:


General Notes and Observations: Locations, abundances, unusual behaviors:


Body
This closer view shows the strong green color with the darker spots.


Gnathopod 1

This view of gnathopod 1 shows that it is subchelate and has an oblique palm.


Gnathopod 2

Gnathopod 2 also has an angled palm and is subchelate.  It is larger than gnathopod 1.


Coxal plates

The coxal plates for pereopods 3 and 4 are much wider than the second articles of those pereopods, which are rectangular.


Epimera_2-4
This view shows epimera 2-4 (top of photo, left to right), which are dorsal to coxae 2-4 (bottom of photo).  The posteroventral borders of epimera 2 and 3 are rounded, not toothed.


Uropod 3

Uropod 3 (on the right) is biramous.  The outer ramus (in sharpest focus here) has two curved distal teeth.  The inner ramus (behind it, less sharp focus) has both teeth and setae.  Neither of the two rami is as long as the peduncle (basal article) of the uropod.



Authors and Editors of Page:
Dave Cowles (2014):  Created original page
CSS coding for page developed by Jonathan Cowles (2007)

Salish Sea Invertebrates web site provided courtesy of Walla Walla University