Megasyllis nipponica

Invasion History

First Non-native North American Tidal Record: 1997
First Non-native West Coast Tidal Record: 1997
First Non-native East/Gulf Coast Tidal Record:

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General Invasion History:

Megasyllis nipponica was described from Japan, and known from many locations around the islands, including the East China Sea, Seto Inland Sea, Pacific Ocean, Sea of Okhotsk, and Sea of Japan. The type locality is Funadomari Bay, off Rebun Island, Northwest of Hokkaido in the Sea of Japan (Imajima 1966; Imajima 1967). This worm has been found on the south (East China Sea) and west coasts of South Korea (Lee and Rho 1996). Megasyllis nipponica was first reported from southern California in 1997 (Cohen et al. 2002; Ranasinghe et al. 2005) and by 2000 was abundant and widespread in San Francisco Bay (California Academy of Sciences 2002; California Academy of Sciences 2014).

North American Invasion History:

Invasion History on the West Coast:

Cohen et al. (2002) list 1997 as the date of first collection for Megasyllis nipponica in Southern California. In 1998, this polychaete was found in Los Angeles-Long Beach Harbors and San Diego Bay (Ranasinghe et al. 2005) and in 2000-2001, it was found in Mission Bay, Newport Bay, Marina del Rey, and Port Hueneme (Fairey et al. 2002). In 2000, the worm was found in Sausalito, San Francisco Bay, and in 2001-2004 it was found to be widespread in San Pablo Bay, the central Bay, and the South Bay. Fairey et al. (2002) listed M. nipponica as rare in Morro Bay, but it was not found by Needles and Wendt (2013) in a 2004-2006 survey. Ballast water and fouling are likely vectors for this polychaete.

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Description

Megasyllis nipponica is an epibenthic polychaete. It belongs to the Syllidae, a family that is extremely diverse and taxonomically difficult, including more than 700 described species (San Martin et al. 2014). Subfamily and generic assignments within the family are in a state of flux (Aguado et al. 2006; Blake and Ruff 2007; San Martin et al. 2014). The genus Megasyllis was erected in 2008. A recent revision gives the genus 14 species, but the key characters are difficult to apply to M. nipponica (Erica Keppel, personal communication). Family characteristics include a relatively small and slender body, a prostomium with 2 pairs of eyes (and sometimes eyespots), three antennae and paired palps, an eversible pharynx, the anterior-most segment (peristomium) lacking chaetae, but bearing 1-2 pairs of tentacles, uniramous parapodia (biramous in reproductive individuals), dorsal and ventral cirri on each chaetiger (except in the Autolytinae subfamily), and a pygidium (anal segment) with 2-3 anal cirri (Pettibone 1963; Blake and Ruff 2007).

Most of the segments of M. nipponica, except for a few anterior ones are triannulated (separated by triple rings). The prostomium is kidney-shaped, with four red eyes in a trapezoidal arrangement. The posterior margin of the prostomium bears two small nuchal organs. The median antenna arises from the center of the prostomium, and is about 4 times as long as the prostomium, and has 14 annulations. The lateral antennae are at the anterior margin of the prostomium, with 8-10 annulations. The palps, broadly triangular, are fused at their bases, directed ventrally, and about as long as the prostomium. The pharynx, visible only when extruded, is thick and terminates in 10 soft papillae, and a large mid-dorsal tooth (Imajima 1966e). The dorsal tentacles of the first segment (peristomium) are slightly longer than the median antenna. The first dorsal cirri are about as long as the dorsal tentacular cirri and each has 13 to 14 annulations. On most of the subsequent segments, the dorsal cirri alternate between short (9-10 annulations) and long (14-17 annulations). The parapodia are blunt and conical, each with a bundle of chaetae between two lobes. The chaetae in these bundles have a secondary tooth near the tip (compound falcigers). The pygidium (anal segment) bears 2-3 anal cirri (Imajima 1966e; Blake and Ruff 2007; San Martin et al. 2014). This worm can reach 90 mm in length, with up to 167 chaetigerous segments. The color ranges from green to brown, varying with algae that the polychaetes consume. The 5th chaetigerous segment is marked by a distinctive black band (Imajima 1966e; Blake and Ruff 2007; Erica Keppel, personal communication 2014).

Syllid polychaetes vary greatly in their reproductive modes. In the genus Megasyllis, a number of the posterior segments become modified for reproduction, and packed with eggs or sperm. This modified section (stolon) develops biramous parapodia, with long notopodial chaetae, and a new, rudimentary head with four large lateral eyes. When the stolon is fully developed, it breaks off, and the stem portion of the animal regenerates a new posterior section. Three worms in a photograph had stolons of 11-20 segments- these were wider than the unmodified segments and orange-yellow instead of greenish or yellowish brown (California Academy of Sciences 2002). The stolons swim away, and swarm together in surface waters, bursting to release the gametes (Pettibone 1963; San Martin et al. 2014). The reproductive stolons (epitokes) form conspicuous swarms at the surface of the water at night (California Academy of Sciences 2002).

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Taxonomy

Ecology

General:

Megasyllis nipponica is a marine syllid polychaete. Its sexes are separate. Like other members of the Syllidae, it reproduces by epitoky, which means that the worm undergoes stolonization, and modifies posterior segments of the body for carrying gametes and swimming (with modified chaetae and enlarged eyes). The epitokous segments are modified and budded off. This epitokous section breaks off, swarms at the surface, and releases eggs and/or sperm (Barnes 1983; California Academy of Sciences 2002).

Details of reproduction and development have not been described for M. nipponica. Epitokes have been found in San Francisco Bay during September surveys over three years (2012-2014; Erica Keppel, personal communication). In the related Typosyllis pulchra, from the coast of Washington, spawning occurs from January to July and stolons consist of 22-30 chaetigers. Animals in culture at 10°C produced a new stolon every 25-30 days after release of the previous one. Animals were stimulated to produce stolons and spawn by a long daylight cycle. Eggs of T. pulchra float on the surface and develop into trochophores within 24 hours of fertilization. Larvae develop a second segment, becoming metatrochophores and settle within 75 hours of fertilization. By five days after fertilization, the larva begins to feed, and develops chaetae in the third week after fertilization (Heacox 1980). While larval development time of M. nipponica may be relatively short, the swimming epitoke stage provides a mechanism of both natural and man-made dispersal (via ballast-water).

Megasyllis nipponica has been collected from a wide range of habitats, ranging from intertidal to subtidal, on silt, mud, rocks, cobbles, seaweed, coral, tunicates, and a variety of manmade structures, including docks, pilings, and Styrofoam floats, (Imajima 1966e; Lee and Rho 1996; Cohen and Chapman 2005; Cohen et al. 2005; California Academy of Sciences 2014). Its geographical range, from northern Japan and southern Russia to southern South Korea (Imajima 1967; Lee and Rho 1996) indicates a wide temperature tolerance (Zvyagintsev et al. 2004). In California surveys, it was collected at 13-22°C and 25-35 PSU (Cohen et al. 2002; Cohen and Chapman 2004; Cohen et al. 2005). The diet of M. nipponica is not known. The Syllidae include carnivorous, herbivorous, omnivorous, and detritivorous worms (Giangrande et al. 2000).

Food:

Macroalgae, invertebrates

Trophic Status:

Omnivore

Omni

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Habitats

General Habitat	Unstructured Bottom	None
General Habitat	Marinas & Docks	None
General Habitat	Rocky	None
Salinity Range	Polyhaline	18-30 PSU
Salinity Range	Euhaline	30-40 PSU
Tidal Range	Subtidal	None
Tidal Range	Low Intertidal	None
Vertical Habitat	Epibenthic	None
Vertical Habitat	Endobenthic	None
Vertical Habitat	Nektonic	None

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Tolerances and Life History Parameters

Minimum Salinity (‰)	25	Field (Cohen et al. 2005)
Maximum Salinity (‰)	35	Field (Cohen et al. 2005)
Maximum Length (mm)	60	Imajima 1966e
Broad Temperature Range	None	Cold temperate-Warm temperate
Broad Salinity Range	None	Polyhaline-Euhaline

General Impacts

Megasyllis nipponica is an abundant polychaete in southern California harbors and San Francisco Bay (Cohen et al. 2002; Cohen et al. 2004; Ranasinghe et al. 2005). However, no impacts are known from California waters.

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References

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Blake, James A.; Ruff, R. Eugene (2007) The Light and Smith Manual: Intertidal invertebrates from Central California to Oregon (4th edition), University of California, Berkeley CA. Pp. 309-410

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California Academy of Sciences 2005-2015 Invertebrate Zoology Collection Database. <missing URL>



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Child, C. Allan (1979) Shallow-water pycnogonida of the isthmus of Panama and the coasts of middle america, Smithsonian Contributions to Zoology 293: 1-86

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Fauchald, Kristian; Jumars, Peter A. (1979) The diet of worms : A study of polychaete feeding guilds, Oceanography and Marine Biology, an Annual Review 17: 193-284

Giangrande, Adriana; Licciano, Margheritia; Pagliaria, Patrizia (2000) The diversity of diets in Syllidae (Annelida: Polychaeta), Cahiers de Biologie Marine 41: 55-65

Heacox, Albert E. (1980) Reproduction and Larval Development of Typosyllis pulchra (Berkeley &=Berkeley) (Polychaeta: Syllidae), Pacific Science 34(3): 245-259

Imajima, Minoru (1966e) The Syllidae (polychaetous annelids) from Japan (V) Syllinae, Publications of the Seto Marine Biological Laboratory 14(4): 253-294

Imajima, Minoru (1967) The Syllidae (polychaetous annelids) from Japan (VI) Distribution and literature, Publications of the Seto Marine Biological Laboratory 14(5): 351-368

Lee, Jong Wui; Rho, Boon Jo (1996) Syllid polychaetes of the genus Langerhansia and Typosyllis (Annelida) from South Sea and East Sea, Korea, Korean Journal of Systematic Zoology Molluscan Research 12(3): 265-280

Needles, Lisa A.; Wendt, Dean E. (2013) Big changes to a small bay: Introduced species and long-term compositional shifts to the fouling community of Morro Bay (CA), Biological Invasions 15(6): 1231-1251

Pettibone, Marian H. (1963) Marine polychaete worms of the New England region. 1. Aphroditidae through Trochochaetidae., Bulletin of the United States National Museum 227(Part 1.): 1-356

Ranasinghe, J. Ananda and 6 authors. (2005) The prevalence of non-indigenous species in southern California embayments and their effects on benthic macroinvertebrate communities, Biological Invasions 7: 679-686

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Salmon, Terry and 21 authors 2014-2022 California Fish Website. https://calfish.ucdavis.edu/



San Martin, Guillermo; Aguado, Maria Teresa; Alvarez-Campos, Patricia (2014) Revision of the genus Megasyllis (Annelida, Syllidae) with descriptions of four new species, Journal of the Marine Biological Association 94(2): 331-351

Zvyagintsev, A. Yu;. Korn, O. M.; Kulikova, V. A. (2004) Seasonal dynamics of pelagic larvae and settling of the fouling organisms in conditions of thermal pollution., Russian Journal of Marine Biology 30(4): 266-277

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