AMPHIPODA 



Table XXIV 

 The depth distribution of Vibilia antarctica as shown by the N 70 V nets 



199 



* Excluding one exceptionally high catch of thirty-one in a single haul at St. 17. 



An association appears to exist between this Amphipod and the Salp Salpa fusi- 

 formis. Three distinct pieces of evidence support this assumption. Vibilia or Salpa 

 were taken by the N 100 H nets at sixty-one stations. The two occurred together at 

 forty-seven stations (77 per cent); at only ten stations (16-5 per cent) was Salpa taken 

 without Vibilia, and here the numbers of Salpa taken were small (1, 1, 1, 2, 3, 4, 4, 5, 

 14 and 16) and at only four stations (6-5 per cent) did Vibilia occur without Salpa, 

 and here again the numbers of Vibilia were small (i, 1, 2 and 5). This evidence may 

 be studied in detail in the table of N 100 H results in Appendix II. At St. WS 38 

 enormous quantities of Salpa fusiformis, estimated at 10,730, were taken in the surface 

 net; the material was carefully looked over before being thrown away, for only fractions 

 could be preserved, and ninety-one specimens of Vibilia were found. A second piece of 

 evidence may be found in the comparison of the vertical migration charts for Salpa and 

 Vibilia, Figs. 123 and 124, where it will be seen that the two curves follow one another 

 very closely. The third piece of evidence, and we believe the most important, comes from 

 a study of the patchiness in distribution of the two forms as revealed by the two consecu- 

 tive net series. These results are described and illustrated on p. 256 and in Fig. 135, 

 where it will be seen that the patches of the two organisms follow one another closely in 

 position and magnitude. Earlier in the voyage we witnessed the association of the Cope- 

 pod Sapphirina with Salpa democratica ; we saw these Copepods entering the Salps and 

 living inside them, feeding upon the food collected on the endostyle, and one is tempted 

 to imagine that there is either a similar association here or that Vibilia is definitely 

 preying upon the Salps themselves. Mr F. C. Fraser has kindly informed us that whilst 

 examining a plankton sample from a later collection (St. WS 376, N 70 V, 250-100 m.) 

 he has found a specimen of Vibilia inside one of Salpa fusiformis ; of course this inclusion 

 may have occurred accidentally in the close mixing of the material in the collecting bucket . 



Barnard (1932) describes Vibilia as a "typical Antarctic and sub-Antarctic species". 

 It has been taken in the Antarctic by the National Antarctic (Discovery), 1 Scotia, 2 

 Gauss 3 and Terra Nova 4 Expeditions. 

 1 Walker (1907). 2 Chilton (191 2). 3 Behning (1927). 4 Barnard (1930). 



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