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Species Name: Marphysa sanguinea Montagu, 1815
Common Name: Rockworm
Synonymy: Leodice opalina Savigny in Lamarck, 1818
Lysidice multicirrata Claparède, 1863
Marphysa acicularum Webster 1884
Marphysa acicularum brevibranchiata Treadwell, 1921
Marphysa californica Moore, 1909
Marphysa haemasoma Quatrefages, 1866
Marphysa iwamushi Izuka, 1907
Marphysa leidii Quatrefages, 1866
Marphysa nobilis Treadwell, 1917
Marphysa parishii Baird, 1869
Marphysa sanguinea americana Monro, 1933
Nereis sanguinea Montagu, 1815

    Kingdom Phylum/Division Class: Order: Family: Genus:
    Animalia Annelida Polychaeta Aciculata Eunicidae Marphysa

    Species Description

    The rockworm, Marphysa sanguinea is a large, often conspicuous benthic polychaete. Like other worms belonging to the phylum Annelida, the opalescent body of M. sanguinea is divided into numerous segments. Several of these divisions are called setigers, so named because of the presence of small hairs called setae located on either side of the segment. In M. sanguinea, long scarlet-red gill filaments arch up over the body, beginning at the 21st to 24th setiger (Ruppert & Fox 1988). Each gill may contain several filaments.

    Potentially Misidentified Species

    Although the rockworm is one of over 55 species described in the genus Marphysa (Hutchings & Karageorgopoulos 2003), other species are either absent or scarce in the Indian River Lagoon. Several other annelid worms can be found in sediments and rocks within the IRL, but the large size and conspicuous gill structure of M. sanguinea makes the worm easily distinguishable.


    Regional Occurrence

    M. sanguinea is recorded as a cosmopolitan species, distributed globally at temperate to tropical latitudes (e.g. Hutchings & Karageorgopoulos 2003; Prevedelli et al. 2007). However, voucher specimens for many populations do not exist or were poorly identified. Taxonomists have recently reexamined many of these specimens, concluding that they may be a few to several different species (Prevedelli et al. 2007).

    M. sanguinea can be found in a variety of benthic environments, including soft muddy sediments around oyster reefs, sandy or muddy tidal flats, among other fouling organisms on dock pilings and buoys, and inside holes of calcareous rocks (Ruppert & Fox 1988). When inhabiting sediments, these worms use their muscular bodies to create burrows in the sand or mud.

    IRL Distribution

    M. sanguinea can be found throughout the lagoon in all of the habitats listed above.


    Age, Size, Lifespan

    The rockworm is a large polychaete, reaching lengths of up to 40 cm with a lifespan of approximately 90 days (Prevedelli et al. 2007). As with other organisms, growth and lifespan may vary with food availability, water temperature, salinity, predator abundance, and additional environmental factors.


    The rockworm is a gonochoric species, with individuals being either male or female (Prevedelli et al. 2007). Populations reproduce sexually and are capable of producing multiple egg clutches throughout their lifetime, a process called iteroparity. Scientists speculate that copulation between the male and female occurs within the burrow, where eggs remain until they reach the free-swimming larval stage. At this time, larvae are released from the burrow into the water column. Individuals from the same population are known to have synchronous spawning events. While published information is scarce concerning populations of M. sanguinea within the IRL, rockworms from the Venice Lagoon in Italy have been documented to spawn throughout April and May (Prevedelli et al. 2007).


    After hatching in the parental burrow, rockworm larvae progress through two planktonic stages and one benthic stage before metamorphosing into juveniles (Prevedelli et al. 2007).

    The first planktonic stage is called the trochophore. At this phase, the round to oblong, yolk-bearing larvae measure approximately 300 μm in length. A band of beating projections called cilia circle the body and are used to propel each larva through the water column. Like many other species of zooplankton, rockworm trochophore larvae are phototactic (attracted to light), drawing them out of their burrows and toward the water’s surface.

    After approximately 24 hours, the larvae enter the planktonic metatrochophore stage. During this time, the body becomes posteriorly flattened and grows to approximately 350 μm. The yolk is relocated from the pharynx to the posterior part of the body, and the first two defined segment pairs appear. These segments are called chaetigers because they bear specialized bristles, or chaelae, characteristic of annelid worms.

    About one week after hatching, larvae enter the nectochaete stage. At this time, each larva begins to lose its cilia and form a 3rd pair of chaetigers. The yolk is lost and mouthparts are formed, along with the first limbs, called parapodia. Larvae grow rapidly over this time period to a final length of 900 μm.

    Juvenile worms develop two weeks after hatching and take approximately 45 days to reach adulthood. During this time, individuals feed, produce additional segments and structures, and grow to about 27 mm in length.


    No information is available at this time


    Trophic Mode

    The rockworm is an omnivore (Ruppert & Fox 1988).


    Although information concerning predators of M. sanguinea is scarce, the rockworm is likely a prey item of several species of wading birds, larger invertebrates and bottom-feeding fishes. Additionally, the planktonic larval stages of the worm are probably ingested by countless predators, including fishes, other zooplankton, and benthic filter feeders such as barnacles.

    Associated Species

    Like many burrowing organisms, M. sanguinea has been known to share its home with other invertebrates. One of these species is the scaleworm, Lepidontus inquilinus, which has been found in the burrows of rockworm populations in North Carolina (Ruppert & Fox 1988). L. inquilinus is approximately 3cm long and pale with small purple spots, one of which is located on the anterior portion of the head. The body bears about 24 pairs of scales marked with singular reddish-brown and white bars.

    In addition to closely-associated species like the scaleworm, M. sanguinea shares habitats with a host of other organisms. For extensive lists of these species, please visit the Habitat pages of this website.


    No information is available at this time


    Hutchings, PA & P Karageorgopoulos. 2003. Designation of a neotype of Marphysa sanguinea (Montagu, 1813) and a description of a new species of Marphysa from eastern Australia. Hydrobiologia 496: 87-94.

    Prevedelli, D, N’Siala, GM, Ansaloni, I & R Simonini. 2007. Life cycle of Marphysa sanguinea (Polychaeta: Eunicidae) in the Venice Lagoon (Italy). Mar. Ecol. 28: 384-393.

    Ruppert, EE & RS Fox. 1988. Seashore Animals of the Southeast: A guide to common shallow-water invertebrates of the southeastern Atlantic coast. Univ. South Carolina Press. Columbia, SC. 429 pp.

Report by: LH Sweat, Smithsonian Marine Station at Fort Pierce
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Page last updated: 28 September 2010

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