DISTRIBUTION, VARIATION, AND SUPPLEMENTAL DESCRIPTION 



OF THE OPOSSUM SHRIMP, NEOMYSIS AMERICANA 



(CRUSTACEA: MYSIDACEA) 



Austin B. Williams/ Thomas E. Bowman,^ and David M. Damkaer' 



ABSTRACT 



Neomysis americana ranges from the Gulf of St. Lawrence to northeastern Florida in estuaries 

 and nearshore ocean and to depths of 100 m on Georges Bank. Samples studied from localities 

 between Nova Scotia and Georgia show no consistent geographic variation. Specific characters 

 are illustrated and discussed. 



Neomysis americana (S. I. Smith, 1873) is the most 

 common mysid in shallow marine waters of 

 eastern North America. In his monograph, W. M. 

 Tattersall (1951) gave the range as "from the 

 Gulf of St. Lawrence to the coast of Virginia in 

 shallow water." Since then its known distribution 

 has been extended south to North Carolina (Wig- 

 ley and Burns, 1971) and recently to South 

 Carolina and Georgia (Sikora, Heard, and Dahl- 

 berg, 1972; Williams, 1972). Further details of its 

 distribution are given below. 



Published and unpublished distributional data 

 available to us before the present study was 

 undertaken suggested the possible existence of 

 two isolated populations of Neomysis: 1) a popu- 

 lation north of Cape Henry, Va., mostly in coastal 

 waters but also occurring in large numbers on 

 Georges Bank; 2) a population confined mainly 

 to sounds and estuaries from North Carolina to 

 Georgia. We suspected that there might be taxo- 

 nomic differences between these or other popu- 

 lations, a likelihood that had occurred inde- 

 pendently to other investigators (Bousfield, in 

 litt.; Heard, in \itt.). Neomysis americana develops 

 two or more generations per year, at least in the 

 United States (Hopkins, 1965), small summer 

 animals and large winter animals. The latter 

 from North Carolina estuaries showed apparent 

 differences that we felt merited further investi- 

 gation. We decided to determine variation and 

 geographic distribution more precisely in A^. 

 americana. 



•Systematics Laboratory, National Marine Fisheries Service, 

 NOAA, U.S. National Museum, Washington, DC 20560. 



^Department of Invertebrate Zoology, National Museum of 

 Natural History, Washington, DC 20560. 



The study is a complement to current ecological 

 investigations in coastal environments. A/^eom>'s is 

 americana is probably an omnivore like its near 

 relative A'^. integer (Mauchline, 1971) or Mysis 

 relicta (Lasenby and Langford, 1973), consuming 

 organic detritus, smaller crustaceans, and diatoms 

 and fitting the trophic role attributed to other 

 mysids preyed upon by fishes in Florida estuaries 

 (Odum and Heald, 1972) and Japan (li, 1964). 

 It is known to be a significant element in the diet 

 of fishes such as flounder, shad, mackerel, and 

 anchovy (Hopkins, 1965), Paralichthys dentatus 

 andP. lethostigma (Powell, in litt.), and the hakes, 

 Urophycis regius and U . floridanus (Sikora et al., 

 1972) as well as other fishes (Taylor, in litt.). 



MATERIALS AND METHODS 



Our materials for study were both reliable 

 literature records and museum specimens. Cana- 

 dian occurrences have been reported by Bous- 

 field (1955, 1956a, b, 1958, 1962), O. S. Tattersall 

 (1955a), Bousfield and Leim (1960), Prefontaine 

 and Brunei (1962), and Brunei (1970). Records 

 from the United States included those of White- 

 ley (1948), Hulbert (1957), Herman (1963), and 

 Wigley and Burns (1971) in addition to others 

 cited previously. Southern range limits and off- 

 shore distribution were partly established by 

 examination of plankton samples taken in waters 

 between Cape Hatteras, N.C., and Jupiter Inlet, 

 Fla., during cruises 4, 5, 7, 8, 9 of MV Theodore 

 N. Gill (October 1953-December 1954), concen- 

 trating on nearshore samples where the species 

 was expected to occur (station data in Anderson, 

 Moore, and Gordy, 1961a, b). Specimens studied 



Manuscript accepted October 1973. 

 FISHERY BULLETIN: VOL. 72, NO. 3, 1974. 



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