Phylum: Cnidaria Nematostella vectensis Class: Anthozoa, Hexacorallia Order: Actiniaria, Nynantheae, Athenaria Starlet sea anemone Family: Edwardsiidae Taxonomy: Nematostella vectensis was 1975). There is a single ventral siphonoglyph described by Stephenson in 1935. (Williams 1975). Nematostella pellucida is a synonym (Hand Oral Disc: There is no inner 1957). In the larger taxonomic scale, the ring of tentacles, and there are no subclass Zoantharia has been synonymized siphonoglyphs, on the oral disc. with Hexacorallia (Hoeksema 2015). Tentacles: Tentacles are retractile, cylindrical, and tapered. They are Description not capitate, or knobbed. Though they can Medusa: No medusa stage in Anthozoans vary from 12-18, there are usually 16 Polyp: (Stephenson 1935; Fautin and Hand 2007). Size: The column (Fig. 1) can be up to There are 6-7 outer (exocoelic) tentacles that 15 mm long in the field, but can grow much are longer than inner (endocoelic) tentacles, longer (160 mm) when raised in the and are often reflexed down the column (they laboratory (Hand and Uhlinger 1992; Fautin can be longer than column). The inner and Hand 2007). The maximum diameter is 4 tentacles can be raised above the mouth (Fig. mm at the base near the bulb (physa) (Hand 1), and can have white spots on their inner 1957) and increases to 8 mm at the crown of edges (Crowell 1946). Nematosomes can be tentacles; the diameter is not often this large, seen moving inside the tentacles. and a more average diameter of the column is Mesenteries: Mesenteries are 2.5 mm. vertical partitions (eight in this species) below Color: The anemone is white and the gullet and visible through the column. transparent when expanded (Fautin and Hand Gonads appear as thickened bands on the 2007), while the internal color depends on mesenteries (Fig. 3) (Lindsay 1975). Eggs are food. produced from these partitions. The Body: Nematostella vectensis is mesenteries can be green, brown, black, etc., radially symmetrical, consisting of a tall depending on food (Williams 1975). cylinder and a crown of tentacles. Aberrant Pedal Disc: The physa is a forms (e.g., two headed, tentacleless) are swollen, bulb-like burrowing structure at the found as well (Williams 1976). The body is base of the column (Fig. 1), which replaces slightly worm-like, in that the column is longer the pedal disc of other anemones. It is than it is wide (Fautin et al. 1987). Usually, covered with rugae (ridges), which secrete the anemone is buried up to its oral disc and mucus and aid in digging and climbing tentacles (Fautin and Hand 2007). (Williams 1975). Nematostella vectensis does Mesenteries divide the internal structure and not attach to solid substrate, but rather cannot be seen through the body walls. On burrows into muddy habitats (Fautin et al. the oral disc, specimens occasionally have 1987). ciliated grooves to direct water Cnidae: According to Matus et al. (siphonoglyphs). (2007), there are three types of cnidae in this Column: The column is longer species: basitrichs, microbasic basitrichs, and than wide, cylindrical, and transparent. The spirocysts. eight mesenteries are visible through its walls. Nematosomes: These are rather There is a thin capitulum (collar) around the mysterious spherical, ciliated bodies, oral disc at the top of the column (Williams sometimes found in the coelenteron (digestive cavity) and in tentacles (Fautin et al. 1987) Piazzola, C.D. and T.C. Hiebert. 2015. Nematostella vectensis. 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. A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/12642 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] (Fig. 2). They contain nematocysts (Hand and anemones are sensitive to pollution, and so Uhlinger 1992), and their function is not will not be found in habitats that become known. contaminated (Williams 1976). Salinity: Nematostella vectensis can tolerate Possible Misidentifications a wide range of salinities, from less than 50% This is the only species of the genus seawater to over 100% in Coos Bay (Hand Nematostella known in the temperate 1957). It is an osmoconformer, has been northern hemisphere. Nematostella polaris, a found from 8 to 38, and is very adaptable to similar Arctic anemone, lives under conditions salinity changes (Inouye 1976). which N. vectensis could tolerate. They are Temperature: This species lives in a wide not believed to be the same species (Hand range of temperatures; in northern California 1957). There is certainly no other very small, alone, it can be found from 0-30° C (Hand mud-dwelling burrowing anemone in our area, 1957). It has been kept for long periods in the which could be confused with N. vectensis. lab at 21-22° C (Inouye 1976). In Coos Bay Flosmaris grandis is another elongate, mud- (South Slough), it ranges from 6-18° C (ibid). burrowing, translucent anemone, but it is Tidal Level: This anemone is generally found usually very large (to 50 cm), has over 24 in salt marsh tide pools above + 3 ft, but is tentacles, and instead of a physa, has a basal sometimes found living subtidal (Hand and disc attached to something solid (Fautin and Uhlinger 1992). Hand 2007). This species also has acontia Associates: It often lives in association with (defensive tentacles that extrude through the the algae Distichlis, Salicornia, and column), which N. vectensis lacks (Fautin and Enteromorpha; the diatom Vaucheria; and the Hand 2007). Diadumene sp. are often long invertebrates nemerteans, polychaete larvae, and pale, but they have pigmentation of some harpacticoid copepods, ciliates, sphaeromid sort and don't burrow. Only N. vectensis of isopods, and gammarid amphipods. these anemones has nematosomes. Abundance: A rarely occurring animal, it can be densely abundant over a small area where Ecological Information it does occur (Hand and Uhlinger 1992). Range: The type locality is the Isle of Wight, Because of its sensitivity to pollution, it quickly where it likely no longer exists due to retreats from areas where the habitat is destruction of habitat (Williams 1975). Its compromised. range covers the Atlantic coasts of Europe; from Florida to Louisiana in the Gulf of Life-History Information Mexico; the east coast of North America from Reproduction: This anemone propagates Nova Scotia to Georgia; and the west coast of using both sexual and asexual reproduction. It North America from California to Washington is dioecious (separate sexes) (Hand and (Hand and Uhlinger 1992; Fautin and Hand Uhlinger 1992), and its gonads on the 2007). mesenteries produce gametes. Animals are Local Distribution: Locally, N. vectensis is found with developed gonads in summer and found at five sites in Coos Bay, including in fall (Williams 1976), but in laboratory settings South Slough, near downtown Coos Bay, and they will reproduce year-round (Hand and at the mouth of Coos River. Uhlinger 1992). Egg production can be Habitat: This species is primarily estuarine (in induced in lab by lowering salinity (Lindsay temperate northern estuaries), and is 1975); the eggs are released in sticky, common in shallow pools of salt marshes gelatinous egg masses that also contain (Fautin et al. 1987; Fautin and Hand 2007). It nematosomes (Hand and Uhlinger 1992). In often lives in pondweed masses, like soft lab these anemones can maintain a schedule muds of Salicornia marshes; Ruppia, of spawning once a week (Hand and Uhlinger Cladophora, and Chaetomorpha ponds (New 1992). Sexual reproduction produces planula England); and Enteromorpha and Vaucheria larvae, which settle as new polyps. There is ponds (Coos Bay) (Williams 1976). These no medusoid stage. It takes two to three days Piazzola, C.D. and T.C. Hiebert. 2015. Nematostella vectensis. 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. for the fertilized egg to grow to a planula, and Behavior: Specimens are usually buried to seven days to setting into a juvenile (Hand the tentacles, but they are also found and Uhlinger 1992). Asexual reproduction is extended over the mud. The anemone can also possible by transverse binary fission move by short, peristaltic-like movements, or (Fautin and Hand 2007). This division can by throwing itself (Lindsay 1975). It secretes a occur in two ways. In the first (physal mucus "tube" to protect its epidermis (Crowell pinching), the column constricts until a piece 1946). This species has also become an of the physa is divided from the rest of the important specimen in genetic research due body. This piece develops into a full clonal to its short generation time and tolerance to anemone. In the second, less common way most conditions, among other reasons (Hand (polarity reversal), the aboral end of the and Uhlinger 1992; Darling et al. 2005), and anemone develops into an oral structure, and its genome has been mapped (Putnam et al. the anemone pinches off in the middle to yield 2007). two fully-formed anemones (Darling et al. 2005). Bibliography Larva: Spherical ciliated planula larvae develop 2 days after fertilization (Hand and 1. CROWELL, S. 1946. A new sea Uhlinger 1992). They will change shape as anemone from Woods Hole, they develop to become elongate and have Massachusetts. Journal of the an apical tuft (Hand and Uhlinger 1992). They Washington Academy of Sciences. actively swim using the cilia on their apical tuft 36:57-60. (Sadro 2001). 2. DARLING, J. A., A. R. REITZEL, P. M. Juvenile: When it settles, the juvenile has BURTON, M.