Streblospio benedicti (also called the Ram's horn worm) is a small polychaete native to the Western Atlantic, where its distribution ranges from the Gulf of Saint Lawrence to Venezuela.

Its general habitat includes oyster reefs, mangroves, grass beds, marinas, and docks while the tidal range where S. benedicti can be found is subtidal to intertidal.

[3] Streblospio benedicti is native to the Western Atlantic ranging from the Gulf of Saint Lawrence to Venezuela, but its distribution can reach as far as Japan.

S. benedicti is known to flourish in physical environments where there have been random or environmental disturbances, due to lessened competition in these areas.

The Ram's Horn Worm is known as an opportunistic pioneering species for this reason, as it tends to explore newly disturbed areas.

Streblospio benedicti is also a relatively long-lived species, as individuals tend to exhibit lifespans ranging from 30 to 75 weeks.

[5][6] The species is poecilogonous, which means that the females exhibit two distinct reproductive strategies during early larval development.

Lecithotrophic brood development occurs when the females produce fewer amounts of large eggs, which are around 100-200 μm in diameter.

They are physically capable of immediate settlement but they will typically remain in the water column for a period ranging from a couple of hours to one week.