10 1.5 2.0 2.5 3.0 3.5 4.0 4.5 W 

 I 1 1 1 1 1 1 1 1 



S. timucu N=47 



S. marina N = 28 



S. notata N -30 



S. strongylura N =7 



S. incise 



N = 8 



S. exills 



N = 12 



L 



X 



_L 



_L 



X 



_L 



_L 



J 



FiGTiKE 187. — Total length (in m) "f ovigerous female Lemanthropus belones from six species 

 of Strongylura arranged from W. Atlantic east to E, Pacific. The horizontal line 

 represents the range, the vertical line the mean, the filled-in rectangle two standard 

 errors on each side of mean, and open rectangle one standard deviation on each side of 

 mean. 



The total length of ovigerous female Leman- 

 throjnis heloTies also varies: copepods from the 

 three western Atlantic hosts are significantly 

 smaller than those from the two Pacific hosts (fig. 

 187). Strongylura strongylura is geographically 

 intermediate (Indo-West Pacific) and has inter- 

 mediate-sized L. helones. The Pacific hosts {S. 

 incisa and S. exilis) do reach a greater lengtli than 

 the other four species of hosts, but the possible 

 host-parasite size correlation breaks down: S. 

 strongylura, the smallest of the six host species, 

 does not have the smallest copepods. 



The relative lengths of the two setae on leg 5 

 in Parahomolochiis have been examined by area 

 (fig. 188) and by host (fig. 189). The first set of 

 Hubbs-Perlmutter diagrams in each figure is of 

 a sample of 50 P. hellones taken from one collection 

 of Strongylura notata. at Sarasota, Fla. This dia- 

 gram gives a measure of the amount of variation 

 to be expected in setae lengths of a single popula- 

 tion from one host species at one time and place. 

 The smaller ratio of seta 1 to 2 distinguishes the 



eastern Pacific P. constrictus from its probable 

 ancestor P. hellones. The higher ratio distinguishes 

 P. sinensvs from either of these. The difference 

 in the ratio is primarily due to the much greater 

 length of seta 2 in P. constrictus and the shorter 

 length of seta 2 coupled with a longer seta 1 in 

 P. sinensis. Neither the absolute lengths of seta 1 

 and seta 2 nor their ratio varies significantly 

 among the populations living on the three hosts of 

 P. con^tricttts in the eastern Pacific Ocean. Varia- 

 tion is extensive, however, among populations of 

 P. hellones. The populations in the five subareas 

 of the western Atlantic all have similar absolute 

 lengths of both setae, and their ratios are nearly 

 identical. The (xulf of Guinea and Mediterranean 

 populations have seta 1 somewhat longer, resulting 

 in a significantly higher ratio of seta 1 to seta 2. 

 Setae lengths differ among three western Pacific 

 populations— Japan, Australia, and Philippines — 

 but their ratios are nearly identical. 



Thus, in CcHigodes laciniatus at least, intra- 

 specific variation in the copepod is related to host 



COPEPODS AND NEEDLEFISHES 



423 



