Planktotrophic pelagic larvae with from 4 to 22 setigers were col- 

 lected between mid-October and mid-February in Great Harbor. 

 Woods Hole, Mass. They metamorphosed generally at the 18-20 

 setiger stage. Following the spring spawning, development 

 occurred entirely within the parent tube. Benthic larvae metamor- 

 phosed at the 15-17 segment stage, leaving the parent tube and bur- 

 rowing into the surrounding substratum. In response to a lack of 

 suitable substratum, most S. setosa metamorphosed anyway, form- 

 ing tubes of mucus. However, some larvae did not metamorphose 

 for periods of up to 2 mo, increasing in size and sometimes in num- 

 ber of segments. Larvae survived and metamorphosed in 50, 75. 

 and 100% sea water. 



In the New York Bight apex, during summer months, we found 

 more widespread occurrence of S.filicomis, and higher numbers at 

 several scattered locations (Fig. 38). 



Prionospio steenstrupi Malmgren, 1867 



[Prionospio malmgreni var. dubia Day, 1961] 



DESCRIPTION: Length to 45 mm, 100 segments (Day 1967); 

 tubicolous. but can leave tubes (Remane 1933). 



DISTRIBUTION: North Atlantic from Norway to Greenland 

 and New Brunswick to Florida; Alaska to southern California: 

 Japan, South Africa (Day 1973). 



HABITAT: Intertidal to 1,745 m (Day 1973). Pearce (1972) 

 found Prionospio steenstrupi to be more abundant in marginally 

 polluted areas than in uncontaminated areas in the New York Bight 

 apex. In the present samples, we also found P. steenstrupi to be 

 most abundant in areas containing >3% organic material, occur- 

 ring in highest concentrations in high organic (>5%) areas. They 

 were abundant in all grades of sand and moderately abundant in 

 silty sediments (Fig. 39; Table 1). 



FEEDING ECOLOGY: The Spionidae are tentaculate, surface 

 deposit feeders. They are probably nonselective since their guts 

 contain many sand grains as well as detritus (Day 1967). Spionids 

 are a major food item in the diet of haddock (Wigley and Theroux 

 1965). 



REPRODUCTION AND GROWTH: Curtis (1977), in Green- 

 land, found that the seasonal trend in oocyte size favored a winter or 

 spring spawning period for Prionospio malmgreni. Hannerz ( 1 956) 

 reported that in the Gullmar Fjord, Sweden, mature ova measure 

 100 fim and development is planktotrophic with no brood protec- 

 tion. Day (1967) stated that various species of Prionospio must be 

 very abundant, for their larvae are present in enormous numbers in 

 neritic plankton samples. 



Polydora ligni Webster, 1879 



DESCRIPTION: Small, tubicolous worms; largest specimens 

 measure 32 mm in length and have up to 80 segments (Blake 1971). 



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Figure 39.— Distribution and abundance or Prionospio steenstrupi in lhi New 

 York Bight ape\. 



DISTRIBUTION: Cosmopolitan, in all oceans at all latitudes 

 (Hartman 1969). 



HABITAT: Intertidal to a few meters (Day 1973); Polydora ligni 

 is a common inhabitant of estuaries in North America. In the New 

 York Bight apex samples. P. ligni was found in depths to 46 m. 

 They were present in all sediment types but were most common in 

 medium to fine sand. Greatest abundance occurred in low organic 

 areas: however, they were also represented in higher organic sedi- 

 ments (Fig. 40). 



Hempel (1957) has studied the tubes of Spionidae and found that 

 substrate materials used for building are not chosen at random, but 

 are rather carefully selected. According to Kisseleva (1967), the 

 determining factors in the selection of building materials are weight 

 and quality of the substrate granules: for Polydora ciliata larvae, 

 the critical factor is particle size, not composition. 



FEEDING ECOLOGY: P. ligni, as all other spionids, is a sur- 

 face deposit feeder (Day 1967). Breese and Phibbs (1972) found P. 

 ligni in laboratory cultures feeding on larvae of the Manila clam. 

 Tapes semidecussata, and the oyster Crassostrea gigas. One worm 

 contained 20 larvae. The spionids entered the molluscan rearing 

 tanks as larvae, and presumably fed on the algae Monochrysis 

 lutheri and Isochrysis galliana. the food organisms used for cultur- 

 ing the molluscan larvae. 



REPRODUCTION AND GROWTH: P. ligni lays its orange 

 eggs (120 ;<m in diameter) in tough egg capsules. These may be 

 protected inside the burrow, the female remaining with the develop- 

 ing larvae, and producing a current of water through the burrow, 

 insuring continuous oxygenation. In Maine waters, these egg cap- 

 sules have been collected from April to July vsith up to 132 eggs 

 capsule (Blake 1969): in the Woods Hole. Mass.. area, the number 



