time to maturity is fairly constant at about 30-40 d, thus emphasiz- 

 ing the importance of rapid maturation in opportunistic species, 

 even where resources permit production of only a few eggs. 



Sexes are normally separate and, according to Warren (1976). 

 occur in approximately equal proportions. Males are readily distin- 

 guished by large copulatory setae on the eight and ninth setigers. In 

 laboratory and field populations, Grassle and Grassle (1974) have 

 found that some genetically distinct individuals change sex from 

 male to female and may be self-fertilizing before the transition is 

 complete. This is an obvious advantage where the pattern of disper- 

 sal and the distribution of suitable habitats results in only a few indi- 

 viduals reaching a particular unexploited habitat. 



ADDITIONAL INFORMATION: The cosmopolitan distribu- 

 tion of C. capitata and its tolerance of wide ranges of temperature, 

 salinity, oxygen content, and a variety of other conditions inimical 

 to other organisms cannot fully be explained since laboratory stud- 

 ies do not show unusual ranges of tolerance to any of these environ- 

 mental variables. For example, Reish (1970) compared C. capitata 

 with three other species of polychaetes on the basis of their toler- 

 ance to different concentrations of nutrients, salinity, and oxygen. 

 Capitella capitata was most sensitive to increased concentrations 

 of silicates, second most sensitive to reduced oxygen conditions, 

 but most tolerant of increased phosphates and reduced salinities. 

 Henriksson (1969) found C. capitata to be less tolerant of low oxy- 

 gen conditions than Nereis diversicolor or Scoloplos armiger. 

 Mangum and Van Winkle (1973) demonstrated that C. capitata had 

 no unusual regulatory ability in decreased oxygen concentrations 

 although C. capitata could repay an oxygen debt whereas Polydora 

 ligni could not. Laboratory studies do not reveal any unusual toler- 

 ance to detergents or to heavy metals (Kaim-Malka 1970; Bellan et 

 al. 1972; Reish et al. 1974). The Wild Harbor (Massachusetts) 

 studies (Sanders et al. 1972) indicate that C. capitata is more sensi- 

 tive to high concentrations of oil than Nereis succinea and Rossi et 

 al. (1976) found C. capitata to be more sensitive to three of four 

 test oils used than Nereis arenaceodonta. 



Results of these studies would seem to indicate that a synergistic 

 effect of several factors, e.g., the concentrations of organic matter, 

 dissolved oxygen, etc., may be responsible for determining popu- 

 lation levels of C. capitata in a given situation. Another explana- 

 tion might be that if C. capitata is indeed a complex of six sibling 

 species (Grassle and Grassle 1976), and if all or a few of these spe- 

 cies were present in a certain area, at a certain time, the most "fit" 

 or tolerant of existing conditions could be selected for. 



Mediomastus ambiseta (Hartman, 1947) 



DESCRIPTION: Small burrowing, motile worms; length to 

 about 38 mm in our collections. 



DISTRIBUTION: East coast of United States, southern Califor- 

 nia, and lower California (Hartman 1969; Hobson 1971). 



HABITAT: Intertidal and shelf depths (Hobson 1971). 

 Mediomastus ambiseta was collected in high numbers from coarse 

 sand and a serpulid polychaete assemblage in Delaware Bay 

 (Maurer, Watling, Leathern, and Kinner 1979; Haines and Maurer 

 1980). In the New York Bight apex, M. ambiseta reached very high 

 concentrations in high organic silty sediments (up to 8,820/m : in 

 summer). It was also abundant in medium to high organic content 

 fine sands (up to 840/m : in summer), but occurred in lower num- 



bers in coarse and medium sand and in lower organic areas (Fig. 

 36). 



FEEDING ECOLOGY: All members of this family (Capitelli- 

 dae) are deposit feeders (Day 1967; Gosner 1971). 



REPRODUCTION AND GROWTH: Although no specific 

 information is available on the reproduction and growth of M. 

 ambiseta , following the West Falmouth (Massachusetts) oil spill, it 

 exhibited some degree of opportunism (Sanders et al. 1972). 

 Therefore, it may be characterized by rapid development, many 

 reproductions per year, high recruitment, high death rate, and some 

 form of brood protection (McCall 1977). 



There were 5.9 times more M. ambiseta at the Bight apex stations 

 during summer months than in winter (Fig. 36). 



-■/'""" ': 

 r^- ■■■■:[ ,j«-~.J- : ) 



4 S: JP\ 



r*\\\wi< !i3«l jo. \ \ / 



»// i|340' v 10 



/ 



□.-»- 



□ ■ " 



Figure 36.— Distribution and abundance of Mediomastus ambiseta in the New 

 York Bight apex (top— summer, bottom — winter). 



Travisia carnea Verrill, 1873 



DESCRIPTION: A stout-bodied, grublike worm; length to 59 

 mm. width 8 mm, segments 25-29 (Pettibone 1954). (Only Alas- 

 kan specimens reach maximum size reported.) 



DISTRIBUTION: Northeastern United States to Chesapeake 

 Bay: Arctic Alaska (Verrill 1873; Pettibone 1954; Kinner and 

 Maurer 1978). 



HABITAT: Found at depths between 5.4 and 34.2 m. In the apex 

 of the New York Bight, Travisia carnea occurred in low numbers. 



26 



