Vol. XLI. September, iQ2i. No. j 



BIOLOGICAL BULLETIN 



ANOTHER MALE COPEPOD OF THE GENUS 



SALMINCOLA FROM THE GILLS OF 



THE CHINOOK SALMON. 



NATHAN FASTEN, 



DEPARTMENT OF ZOOLOGY, OREGON AGRICULTURAL COLLEGE, 

 CORVALLIS, OREGON. 



The only male copepod known to exist in the genus Salmincola 

 of the family Lernaeopodidfe is that of Salmincola edwardsii 

 (Olsson) Wilson, which parasitizes the brook trout Salvelinus 

 fontinalis Mitchill of many of the states of the middle West and 

 East. This male has been described and figured by the writer 

 in the BIOLOGICAL BULLETIN, Vol. XXVII. , for August, 1914. 

 During the latter part of the summer of 1919, the author obtained 

 large numbers of another species of Salmincola, namely, Sal- 

 mincola beani Wilson, parasitic on the gills of the chinook salmon 

 Oncorhynchus tschawytscha Walbaum of Green River, Auburn 

 Washington, and a careful search amongst these parasites, 

 resulted in the discovery of three mature males. 



The size of these new male Salmincola is much larger than 

 that of Salmincola edwardsii (compare Figs.. I and 3 with 4). 

 The former (Figs. I and 3) measure a>out i.o mm. in length 

 and about 0.17 mm. in width in the region of the reproductive 

 organs; whereas the latter (Fig. 4) are about 0.7 mm. long and 

 o.i mm. wide in the region of the gonads. Otherwise their 

 structure seems to be similar. 



The organs which are of particular interest and importance in 

 the male are the reproductive organs. These are paired struc- 

 tures, located laterally in the posterior region of the body (Fig. i, 

 r), between the digestive tract and the body w T all. They consist 

 essentially of the following three main parts: (i) the testes 

 (Fig. 2, /), (2) the coiled vas deferens (Fig. 2, i'), and (3) the 



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