''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. Sexual maturity is reached at around 9 to 14 weeks and populations and individuals may vary during development. It can be found in the mudflats and soft sediments of estuaries and coastal waters. 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. Additionally, ''S. benedicti'' can tolerate a broad range of temperatures and salinities. Due to its tolerance of high organic contents, ''S. benedicti'' is a pioneer organism of new habitats that it settles in. Furthermore, despite its small size, only reaching a maximum of in length, S. benedicti plays an important role in estuarine food webs as it can reach high population densities and is a substantial grazer of phytoplankton.

Distribution

''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 Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

. ''Streblospio benedicti'' was first found in San Francisco bay where it was most abundant in the soft sediments of the bay. It was then reported to be found in Elkhorn Slough, South of

San Francisco Bay San Francisco Bay is a large tidal estuary in the U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the big cities of San Francisco, San Jose, and Oakland. San Francisco Bay drains water from a ...

, and even further South in Mexico, in the Topolobampo lagoon on the Gulf of California and the Urias estuary near Mazatlan. The distribution range of ''Streblospio benedicti'' also includes the Northeast Atlantic such as Ireland, France, and Belgium. There have also been reports of ''Streblospio benedicti'' from the

Caribbean The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean Se ...

and the Mediterranean Sea, and the Black and Caspian Seas.

Habitat and ecology

''Streblospio benedicti'' is common in estuarine habitats. They are typically found in muddy or soft-sediment areas, such as mudflats,

seagrass beds A seagrass meadow or seagrass bed is an underwater ecosystem formed by seagrasses. Seagrasses are marine (saltwater) plants found in shallow coastal waters and in the brackish waters of estuaries. Seagrasses are flowering plants with stems and ...

, and marshes. The species is also adapted to rapid colonization, due to its capacity for small-scale dispersal following larval development. ''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. Much of the ability to traverse these environmentally altered areas, is due to S. benedicti's tolerance for pollution. The species is also generally able to tolerate a broad range of salinity. However, population levels are known to decrease with the decrease of salinity levels in their environment. The same is true for temperature, as the species is generally able to tolerate a large range of temperatures. Though, it is speculated that cold water temperatures can limit the occurrence of ''S. benedicti'' in some habitats during winter and spring. ''Streblospio benedicti'' is also a relatively long-lived species, as individuals tend to exhibit lifespans ranging from 30 to 75 weeks.

Competition and predation

''S. benedicti'' is a specialist when it comes to finding resources, and is a

generalist A generalist is a person with a wide array of knowledge on a variety of subjects, useful or not. It may also refer to: Occupations * a physician who provides general health care, as opposed to a medical specialist; see also: ** General pract ...

in terms of discovering habitats. However, if resources are limited, the species has proven to be a capable competitor. Due to its tendency to reside in sediment surfaces, ''Streblospio benedicti'' is quite vulnerable to epibenthic predators. These include organisms such as

blue crabs Blue crab may refer to: * Blue Crab 11, an American sailboat design * ''Callinectes sapidus'' – Chesapeake or Atlantic blue crab of the West Atlantic, introduced elsewhere * ''Cardisoma guanhumi'' – blue land crab of the West Atlantic * '' Disc ...

, grass shrimp, and

flounder Flounders are a group of flatfish species. They are demersal fish, found at the bottom of oceans around the world; some species will also enter estuaries. Taxonomy The name "flounder" is used for several only distantly related species, thou ...

Morphology

''Streblospio benedicti'' is a small ( in length) polychaete. It is segmented and looks like a tube or worm. It has a cone-shaped head with four eyes, feeding palps and gills. Usually rusty, red-brown color, its gills have green bands. It's morphologically very similar to S. gynobranchiata, a closely related species. It's morphology is similar to many

spionidae Spionidae is a family of marine worms within the Polychaeta. Spionids are selective deposit feeders that use their two grooved palps Pedipalps (commonly shortened to palps or palpi) are the second pair of appendages of chelicerates – a grou ...

polychaetes (a family of marine worms). Other species that ''Streblospio benedicti'' are mistaken for include ''Streblospio shrubsoli'' and ''Streblospio benedicti japonica''. The morphology of feeding palps and

cilia The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...

were found to be shared between both ''Streblospio benedicti'' and ''Streblospio shrubsoli''. However, they did have different morphological functions of

papillae Papilla (Latin, 'nipple') or papillae may refer to: In animals * Papilla (fish anatomy), in the mouth of fish * Basilar papilla, a sensory organ of lizards, amphibians and fish * Dental papilla, in a developing tooth * Dermal papillae, part of ...

Reproduction

''Streblospio benedicti'' reproduces sexually and has two separate sexes. They typically experience high rates of reproduction and high growth rates. Females have pouches, called dorsal brood pouches, which are used to incubate the embryos during the early stages of development. The species is poecilogonous, which means that the females exhibit two distinct reproductive strategies during early larval development. These strategies are genetically determined and differ in their brood development. Both forms of development can also occur within the same population. In

planktotrophic Marine larval ecology is the study of the factors influencing dispersing larvae, which many marine invertebrates and fishes have. Marine animals with a larva typically release many larvae into the water column, where the larvae develop before met ...

brood development, some females will produce large amounts of small eggs, which are around 60-70 μm in diameter. These developed

larvae A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

typically have long swimming setae and will live in and feed on plankton for a period of up to seven weeks. Lecithotrophic brood development occurs when the females produce fewer amounts of large eggs, which are around 100-200 μm in diameter. In contrast to the planktotrophic offspring, the lecithotrophic larvae lack the swimming setae. 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.

Usage

''Streblospio benedicti'' is commonly used as an indicator organism for marine nutrient pollution.

References

{{Taxonbar, from=Q2518497 Canalipalpata