Monocorophium insidiosum (Crawford, 1937)

Material examined: CNCR­20395; number of specimens: 1, 2; SM station; collection date: 16/10/98.

Type locality: Oakland, San Francisco, California.

Distribution: This species has been reported from Denmark, Germany, England (Shoemaker, 1947); Mediterranean Sea (Myers, 1983); from Chateur Bay to Chesapeake Bay (Shoemaker, 1947; Bousfield, 1973); Terminos Lagoon, Campeche, Mexico (Ledoyer, 1986); Cuba (Ortiz & Lalana, 1989); Pacific coast of North America, from Alaska to northern California in coastal marine and brackish waters (Bousfield & Hoover, 1997); Hawaii (Barnard, 1970) and Japan (Hirayama, 1984).

Range extension: Within the Gulf of Mexico, this species has only been recorded in Terminos Lagoon, Campeche, Mexico (Ledoyer, 1986), therefore the presence of these specimens at SM inlet extends its geographic distribution to Tamaulipas State, Mexico.

Remarks: Monocorophium insidiosum is associated with Halodule and Thalassia seagrasses, and algal beds (Ledoyer, 1986). Apparently, M. insidiosum is a widely distributed species that has been transported to different world regions (Barnard, 1970).

The salinity and temperature ranges measured at the collection site were 24 to 26 %o and 27 to 28 °C, respectively.