Scientific Name and Authority

Orchestia gammarellus   (Pallas, 1766)


Description:

Orchestia gammarellus is an amphipod of the family Talitridae. General features of this family include a laterally compressed, arched body; a short Antenna 1 and long Antenna 2; well-developed eyes and pereiopods (walking legs); hopping locomotion; and the ability to survive exposure to air in beach wrack-lines and debris. Orchestia gammarellus has a squarish-oval, medium-sized eye. Antenna 1 is short, with its tip reaching the distal end of peduncle segment 2 of Antenna 2. The peduncle of Antenna 1 has 4 segments, and the flagellum has 4-5 segments. Antenna 2 is about 1/3 body-length. The peduncle is more robust in the male than female, and the flagellum is slightly shorter than the peduncle. In both sexes, Gnathopod 1 is much smaller than Gnathopod 2. The dactyl (segment 7) of Gnathopod 1 barely overlaps the palm. The propodus of Gnathopod 2 is greatly inflated, especially in the male. The dactylus is shorter than the palm. Pereiopods 3 and 4 are relatively short. Perieopods 5-7 are progressively longer, and their coxal plates larger. The abdominal side plates 2 and 3 have angular corners. The urosome segments are distinct. Uropods 1 and 2 are biramous, while Uropod 3 is uniramous, with the distal segment blunt and spine-like. The telson is spade-like, formed of two medially fused lobes with stout lateral and apical spines. Adult males reach 16-18 mm, while females reach 14 mm. The color ranges from greenish brown to reddish brown. This description is based on: Bousfield 1973 and Lincoln 1979.

Taxonomic Classification:


Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Subclass: Eumalacostraca
Superorder: Peracarida
Order: Amphipoda
Suborder: Gammaridea
Family: Talitridae
Genus: Orchestia
Species: gammarellus

Synonyms:

Onicus gammarellus (Pallas, 1776)

Cancer gammarellus (J. F.W. Herbst, 1793)

Gammarus gammarellus (A.G. Olivier, 1791)

Porrassia mallorquensis (Marcus, 1912)

Orchestia gammarella

Talorchestia inaequalipes (Barnard, 1951)

Potentially Misidentified Species:

Orchestia grillus

Northwest Atlantic, Gulf of St. Lawrence to Gulf of Mexico (Bousfield 1973)


Orchestia uhleri

Northwest Atlantic, Casco Bay to Gulf of Mexico (Bousfield 1973)


Platorchestia platensis

Type species of a nearly cosmopolitan species complex, Gulf of St. Lawrence to Patagonia, range expansion in North Sea and Baltic, North Sea to South Africa (Bousfield 1973; Persson 2001; Spicer and Janas 2006). Populations in Japan, Australia, and Ascension Island-St. Helena have been described as separate species.