WIGLRV and BURNS: DISTRIBUTION AND BIOLOGV OF MVSIDS 



Myst's stenolepis S. I. Smith, 1873 



This large American mysid is distributed in 

 coastal waters of northeastern North America 

 from the Gulf of St. Lawrence to New Jersey. 

 Though very common to this regfion it is rep- 

 resented by only a few specimens in the NMFS 

 collection because biological samples were rarely 

 collected in the intertidal and shallow subtidal 

 zones. 



The NMFS collection contains 13 specimens 

 from six samples (Figure 15; Burns and Wigley, 

 Table 16) . all from a rather small area off east- 

 ern Massachusetts and eastern Rhode Island. 

 The specimens were collected with a dip net 

 along shore in water dejiths of about 1 m. Four 

 samples were taken in beds of Zostem or algae, 

 and one sample was from a sandy tjottom (bot- 

 tom type for the other sample is unknown). 



M. stevolepis is one of the largest shallowwater 

 species in the NMFS collection. Body lengths 



of these specimens range from 13.0 to 2(5.0 mm, 

 and average 20.4 mm. 



According to Smith (1879) the life span of 

 this species is one year. Their life cycle is as 

 follows: (1) adults spawn in winter and early 

 spring, (2) the young ap]iear in late sjiring and 

 summer, and (3) they mnture in the fall and 

 winter. Material in the NMFS collection sub- 

 stantiates this life-cycle plan. Body lengths of 

 specimens, by months, are: 



Figure 15. — Geographic distribution of Mysis steiiolriiis 

 based on specimens in the collection at the NMFS Bio- 

 logical Laboratory, Woods Hole. 



Three larvigerous specimens collected in Feb- 

 ruary and March range in size from 25.0 to 

 25.5 mm. 



Fecundity of this species is very high com- 

 pared with other east coast mysids. An oviger- 

 ous-larvigerous specimen 25.0 mm long, collected 

 in late February, held 94 eggs and 50 stage III 

 larvae in the brood pouch. Average diameter of 

 the eggs is 0.4 mm and average length of the 

 larvae is 1.4 mm. A 25.5-mm long larvigerous 

 female from the same sample was carrying 188 

 stage IV larvae; their average length is 1.4 mm. 

 A 25.0-mm larvigerous female collected in March 

 was carrying 171 stage VII larvae; their aver- 

 age length is 1.86 mm. 



A rather high water temperature was noted 

 when the September 4, 1961, sample of M. ste- 

 nolopis was collected. The temperature was 

 23.9° C at a depth of 1 m in an eelgrass bed in 

 Waquoit Bay, Falmouth, Mass. This is the 

 highest temperature recorded for the NMFS 

 samples of this species. 



Prautius flexuosus (O. F. Miiller, 1776) 



This species is very common in shallow coastal 

 waters of Great Britain and along the northern 

 coast of France, Holland, and southern Scandi- 

 navia (Tattersall and Tattersall, 1951). In 1960 

 it was discovered in the harbor at Barnstable, 



735 



