Nephtys incisa Malmgren, 1865 



DESCRIPTION: A mobile, burrowing, large species, reaching a 

 maximum length of 150 mm. width to 15 mm, segments to 75 (Pet- 

 tibone 1963). 



DISTRIBUTION: Greenland. Davis Strait. Ireland. Norway, 

 Sweden. North Sea. Baltic to Portugal. Mediterranean. Gulf of St. 

 Lawrence to Virginia. Chesapeake Bay. North Carolina (Pettibone 

 1963: Gardiner 1975). 



HABITAT: Intertidal to 1.745 m; found on bottoms of soft or 

 sticky mud, muddy sand, very fine or coarse sand, mud which con- 

 tains gravel, shells, worm or amphipod tubes, or decaying debris 

 (Pettibone 1963: Day 1967). Pettibone (1963) reported Nephtys 

 incisa to be "the most common and abundant species on muddy 

 bottoms along the New England coast, in bays and sounds as well 

 as off the open coast." In these situations, it is usually associated 

 with the bivalves Nucula proximo and Yoldia limatula, members of 

 a distinct deposit-feeding soft bottom community (Sanders 1958. 

 1960). From Cape Cod to Cape Hatteras, Kinner (1978) found N. 

 incisa to be a dominant on the mid-outer shelf in silt-clay. Pearce 

 (1972) found N. incisa in greater abundance around sludge deposits 

 in the New York Bight apex than in relatively unpolluted habitats. 



In the present New York Bight apex study, N. incisa was present 

 in all sediment types but was clearly most abundant in fine sand or 

 silty areas having the highest percentages of sediment organic 

 material (Fig. 32; Table 1). 



4020- 



Figure 32. — Distribution and abundance of Nephtys incisa in the New York 

 Bight apex. 



FEEDING ECOLOGY: Until recently, it was thought that all 

 nephtyids were strict carnivores, probably because they possess 

 large jaws, but Sanders (1956, 1960) found N. incisa in Long 

 Island Sound and in Buzzards Bay. Mass., to be nonselective 

 deposit feeders. Sanders, however, did not deny that N. incisa was 

 capable of acting as a carnivore under certain conditions. Con- 

 versely. Clark (1962) believed N. incisa is, at best, a facultative 

 detritus feeder, primarily because its gut is almost always empty 

 indicating a carnivorous diet and rapid digestion. Day (1967) 

 believed them to be selective omnivores because they are found in 

 such large numbers in certain areas. 



Nephtys incisa is also important as a prey item. Wigley and The- 

 roux (1965) found it to be a principal annelid, along with Aphrodita 

 hastata, in the diet of haddock. 



Tyler (1973) found Canadian specimens to have no seasonal 

 trend in caloric value; the annual mean for N. incisa was 3.984 g 

 cal/g dry weight. 



REPRODUCTION AND GROWTH: N. incisa spawns year- 

 round in Long Island Sound with peaks in early spring and late sum- 

 mer (Sanders 1956). Specimens of N. incisa with coral-pink eggs 

 have been found in August in Massachusetts and young specimens 

 of 28-32 segments have been found in August in Maine (Pettibone 

 1963). Nephtys incisa does not brood its young, but produces large 

 numbers of planktotrophic larvae (lO'-lO 6 per female) which 

 undergo a long pelagic development. Time to maturity is unknown 

 (Thorson 1946; Sanders 1956; Clark 1961. 1962). 



Relative to more opportunistic species. N. incisa exhibits slow 

 development, few reproductions per year, low recruitment, and low 

 death rate. Because of these factors, because they do not brood 

 developing young, and because they produce large numbers of 

 planktotrophic larvae, they are classified as an "equilibrium" spe- 

 cies, present early in colonization, but remaining at low and con- 

 stant abundance (McCall 1977). 



ADDITIONAL INFORMATION: There is some evidence, 

 including that provided in this study, that Nephtys spp. are highly 

 tolerant of some environmental stresses (Jones 1955; Weber 1971). 

 They are also physiologically equipped for infrequent feeding and 

 long periods of starvation (Clark 1964). Mobility and size could 

 also aid these polychaetes in both escape from predators and migra- 

 tion to more favorable microenvironments. 



Nephtys picta Ehlers, 1868 



DESCRIPTION: A mobile species, length to 60 mm. width to 4 

 mm, segments to 100 (Pettibone 1963). 



DISTRIBUTION: New England to Florida, Gulf of Mexico 

 (Gardiner 1975). 



HABITAT: Intertidal to 40 m (Pettibone 1963); 8-141 m. usually 

 <50 m (Kinner 1978). Found at low water in muddy sand, sandy 

 rubble, gravelly sand. Collected on bottoms of sand and muddy- 

 sand, with shells and sea weeds (Pettibone 1963). In the New York 

 Bight apex, Nephtys picta was found in all grades of sand, most 

 commonly in medium to fine sand. It was not found in high organic 

 sediments and was rare in medium organic sediments (Fig. 33: 

 Table 1). Kinner (1978) found N. picta to be a dominant species in 

 sand on the inner shelf from Georges Bank to Cape Hatteras. while 

 Kinner and Maurer (1978) reported increasing numbers of N. picta 

 associated with sediments containing increasing amounts of silt- 

 clay in Delaware Bay. 



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