Phylum: Annelida Abarenicola pacifica Class: Polychaeta, Sedentaria, Scolecida Order: The lugworm or sand worm Family: Arenicolidae Description pendages (Fig. 2). Size: Individuals often over 10 cm long and Parapodia: (Fig. 3) Segments 1–19 with re- 1 cm wide. Present specimen is duced noto- and neuropodia that are reddish approximately 4 cm in length (from South and are far from the lateral line. All parapodia Slough of Coos Bay). On the West coast, are absent in the caudal region. average length is 15 cm (Ricketts and Calvin Setae (chaetae): (Fig. 3) Bundles of notose- 1971). tae arise from notopodia near branchiae. Color: Head and abdomen orange, body a Short neurosetae extend along neuropodium. mixture of yellow, green and brown with par- Setae present on segments 1-19 only (Blake apodial areas and branchiae red (Kozloff and Ruff 2007). 1993). Eyes/Eyespots: None. General Morphology: A sedentary poly- Anterior Appendages: None. chaete with worm-like, cylindrical body that Branchiae: Prominent and thickly tufted in tapers at both ends. Conspicuous segmen- branchial region with bunched setae. Hemo- tation, with segments wider than they are globin makes the branchiae appear bright red long and with no anterior appendages (Kozloff 1993). (Ruppert et al. 2004). Individuals can be Burrow/Tube: Firm, mucus impregnated bur- identified by their green color, bulbous phar- rows are up to 40 cm long, with typical fecal ynx (Fig. 1), large branchial gills (Fig. 2) and castings at tail end. Head end of burrow is a J-shaped burrow marked at the surface collapsed as worm continually consumes mud with distinctive coiled fecal castings (Kozloff (Healy and Wells 1959). Water is pumped 1993). through burrow by pulsating movements of Body: The body of arenicolids can be divid- the body (Ruppert et al. 2004). ed into three regions based on the presence Pharynx: Thin-walled pharynx is simple and or absence of branchiae. used for continually feeding on sediment. Anterior: A non-retractile prostomium Pharynx described as a large, eversible sack is without appendages (Blake and Ruff with mucus glands called buccal papillae 2007, Fig. 2). Anterior prebranchial region (Healy and Wells 1959) (Fig. 1). of six setigers without branchiae and with Genitalia: strong setigerous annuli. Nephridia: Five pairs of nephridia are naked Trunk: Posterior to the prebranchial (without hoods) and situated between parapo- region is a medial branchial region with large dia on segments 5–9 (Fig. 2). They are branchial gills from setigers seven to 19 (13 sometimes difficult to observe. pairs). Thoracic epidermis very thick, Abarenicola specific characteristics strongly aerolated (Fauchald 1977). Posterior: Caudal region is apodous, Esophageal caeca: Dissection is necessary asetigerous and without appendages. The to identify Abarenicola species. Abarenicola pygidium tapers gradually to anus, no ap- pacifica is distinct in having esophageal caeca A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: https://oimb.uoregon.edu/oregon-estuarine-invertebrates and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] Hiebert, T.C. 2014. Abarenicola pacifica. In: Oregon Estuarine Invertebrates: Rudys' Illustrated Guide to Common Species, 3rd ed. T.C. Hiebert, B.A. Butler and A.L. Shanks (eds.). University of Oregon Libraries and Oregon Institute of Marine Biology, Charleston, OR. comprised of one large anterior pair and 3–6 conformer and can tolerate a wide range of smaller pairs (Blake and Ruff 2007, Fig. 4). salinities (lower salinity limit 17.5) (Oglesby 1973). Possible Misidentifications Temperature: No information is available on Other Arenicolidae have the same temperature tolerance, though temperature bushy gills in the middle third of the body. fluctuation between 6 and 16° C has been Only the genus Abarenicola has well- found to significantly affect feeding rate separated neuropodia, a non-retractile pro- (Hymel and Plante 2000). stomium, more than one pair of esophageal Tidal Level: Individuals are common intertid- caeca, and five pairs of nephridiopores. ally, but no information on specific tide level is Both Arenicola marina and pusilla have available. Hobson (1967) suggests that distri- been found in Oregon estuaries. Abarenico- bution is instead based on sediment composi- la claparedii oceanica, has hooded nephri- tion. dial pores and esophageal caeca composed Associates: In a commensal relationship, of 7–9 smaller pairs. Abarenicola vagabun- Pinnixa schmitti is known to cohabit the bur- da, from Puget Sound (but possibly from row of A. pacifica (O’Clair and O’Clair 1998). Oregon) (Oglesby 1973), is usually larger Abundance: Often to 50/m2 (Kozloff 1974) and dark brown. It too, has hooded nephri- and very dense in specialized habitats. Proba- dial pores, and smaller esophageal caeca bly 2nd most abundant macroscopic animal in (11–18). Finally, the burrows of A. vagabun- Coos Bay (Porch 1970). A. pacifica was much da are less permanent than A. pacifica's, are less abundant than in preceding years-- it was found in deep sand and may be more sub- sparse (<1/m2) on Portside beach in April tidal (Hobson 1966). 2015 (Emlet pers com). Ecological Information Life-History Information Range: Type locality is Puget Sound (Healy Reproduction: Iteroparous. Eggs and sperm and Wells, 1959). Known range includes discharged from nephridiopores, while both Humboldt Bay, California to Alaska, Japan. sexes are in their burrows. Males release thin Local Distribution: A north Pacific form and membranous spermatophores (0.5–0.2 mm in the most common lugworm (family Are- diameter) which fall into female burrows and nicolidae) in Puget Sound area intertidally are ruptured by female setae (Okuda 1936; (Hobson 1966). Found in Coos Bay from Fernald et al. 1987). Oocytes are pink to pale estuary mouth to Coos River mouth (marker yellow and 160-190 µm in diameter with con- 15) and at Sunset Bay (Oglesby 1973). spicuous envelope (Fernald et al. 1987). Fer- Habitat: Individuals build substantial L- or J- tilization occurs in female's burrow. Broods shaped burrows in sand and mud, mixed are found within burrows January-early April gravel or mud sediments (South Slough of (Washington) and develop within gelatinous Coos Bay) (Kozloff 1974). Abarenicola masses (Fernald et al. 1987). pacifica tolerates a muddier, less Larva: Planktonic larvae are non-feeding and permeable, more poorly sorted sediment hatch from gelatinous masses within adult than does A. c. vagabunda (Hobson 1966), tubes as 2 setiger stages (Fernald et al. but does not live in very soft mud (Porch 1987). Only the larvae of two local Are- 1970). nicolidae species are known (Arenicola mari- Salinity: This species is not found in waters na and Abarenicola claparedii, Crumrine of low salinity or in heavily polluted anaero- 2001). bic conditions (Porch 1970), but is an osmo- A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: https://oimb.uoregon.edu/oregon-estuarine-invertebrates and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] Juvenile: Strathmann (ed.). University of Washing- Longevity: ton Press, Seattle, WA. Growth Rate: Relative growth rate of 0–6% 5. HEALY, E. A., and G. P. WELLS. 1959. per day, depending on age and food quality Three new lugworms (Arenicolidae, Poly- (Linton and Taghon 2000). chaeta) from the north Pacific area. Pro- Food: Primarily detritus, picked up by mu- ceedings of the Zoological Society of Lon- cus of proboscis (Fig. 1) and digested out of don. 133:315-335. sand and mud, which is then defecated. De- 6. HOBSON, K. D. 1966. Ecological oberva- pending on sediment type, A. pacificia may tions on Abarenicola species (Polychaeta) utilize a variety of feeding modes (deposit, of the north Pacific, M. S. University of suspension, direct dissolved organic matter Washinton, Seattle, WA. uptake) (Hylleberg 1975). Feeding activity 7. HOBSON, K. D. 1967. The feeding and by Abarenicola pacifica is instrumental in ecology of two North Pacific Abarenicola bioturbation and generation of clay laminae species. (Arenicolidae, Polychaeta). Bio- (Swinbanks 1981). logical Bulletin. 133:323-354. Predators: Arenicolids have many preda- 8. HYMEL, S. N., and C. J. PLANTE. 2000. tors including most estuarine creatures: man Feeding and bacteriolytic responses of the (for fish bait), birds, fish. deposit-feeder Abarenicola pacifica Behavior: Most research into the behavior (Polychaeta : Arenicolidae) to changes in of A. pacific is focused on bioturbation and temperature and sediment food concentra- particle selection (Hylleberg 1975). tion. Marine Biology. 136:1019-1027. 9. HYLLEBERG, J. 1975. Selective feeding Bibliography by Abarenicola pacifica with notes on 1. BLAKE, J. A., and E. R. RUFF. 2007. Abarenicola and a concept of gardening in Polychaeta, p. 309-410. In: Light and lugworms. Ophelia. 14:113-137. Smith manual: intertidal invertebrates 10. KOZLOFF, E. 1993. Seashore life of the from central California to Oregon. J. Carl- northern Pacific coast: an illustrated guide ton (ed.). University of California Press, to northern California, Oregon, Washing- Berkeley, CA. ton, and British Columbia. University of 2. CRUMRINE, L. 2001. Polychaeta, p. 39- Washington Press, Seattle, WA. 77. In: Identification guide to larval ma- 11. KOZLOFF, E. N. 1974. Keys to the marine rine invertebrates of the Pacific North- invertebrates of Puget Sound, the San west. A. Shanks (ed.). Oregon State Uni- Juan Archipelago, and adjacent regions. versity Press, Corvallis, OR. University of Washington Press, Seattle. 3. FAUCHALD, K. 1977. The polychaete 12. LINTON, D. L., and G. L. TAGHON. 2000. worms: definitions and keys to the or- Feeding, growth, and fecundity of ders, families, and genera. Natural Histo- Abarenicola pacifica in relation to sedi- ry Museum of Los Angeles County Sci- ment organic concentration. Journal of Ex- ence Series. 28:1-190. perimental Marine Biology and Ecology. 4. FERNALD, R. L., C. O. HERMANS, T. C. 254:85-107. LACALLI, W.