FLEMINGER: INTEGUMENTAL ORGANS IN GENUS EUCALANUS 



with four or more sites; 

 Abd.I-II with four or more 

 sites; Abd.III and IV with 

 two or more sites; Abd.IV 

 with one pleural site 



sites; 

 sites 



Abd.III with two 



B 



elongatus 



6. A. Mx2 somite with two or 

 more pairs of sites; ThI 

 with seven or more sites; 

 Thll and III with one 

 asymmetrical site within 

 arc of hair sensilla on left 

 of midline; Abd.I-II with 

 two sites 



B 



Mx2 somite lacking sites; 

 ThI with three sites; ThI I 

 and III lacking sites with- 

 in dorsal arc of hair sensil- 

 la; Avd.I-II with up to 

 one site 



C 



B. ThI with 15 sites; Mxl so- 

 mite with 10 sites includ- 

 ing a medial set of four; Al 

 somite with 10 sites includ- 

 ing a posterior set of four; 



Mnd somite with eight sites . subtenuis 



ThI with seven sites; Mxl 

 somite lacking four medial 

 sites; Al somite lacking 

 four posterior sites; Mnd 

 somite with four to six 

 sites 



C. Thll and III with three 

 pleural sites, Abd.IV-V 

 with three tergal sites .... 



Thll and III with two 

 pleural sites, Abd.IV-V 

 with one tergal site 



D. Mnd somite with six sites; 



Abd.I-II lacking tergal sites . . cmssus 



Mnd somite with four sites; 

 Abd.I-II with one tergal 

 site longiceps 



A. Thll and III with two pairs 

 of pleural sites; Mx2 somite 

 with two pairs of tergal 

 sites; Abd.I-II with three 



mucronatus 



mouachus 



D 



Thll and III with one pair 

 of pleural sites; Mx2 so- 

 mite lacking tergal sites; 

 Abd.I-II usually with one 

 site; Abd.III lacking tergal 

 sites pileatus 



B. Mxl somite with two pairs 

 of sites adjacent to the mid- 

 line; Abd.IV-V with one 

 site subcrassus 



Mxl somite with one pair 

 of sites adjacent to the mid- 

 line; Abd.IV-V with three 

 sites deyitatus 



USE OF INTEGUMENTAL ORGANS 

 IN STUDIES ON 

 GEOGRAPHICAL VARIATION 



A relatively high degree of variability in 

 perforation number was noted for the circum- 

 global, broadly tropical species, E. subte)iuis 

 (Table 4, Figures 9, 10). The conspicuous 

 variability was noticed after realization that 

 bilateral symmetry and arrangement in regular 

 patterns distinguishing species groups as well 

 as species is characteristic of integu mental 

 organs. The variation suggested that these 

 organs are a promising source to search for 

 evidence of genetic variation in field-collected 

 planktonic populations. Thus to cany out a 

 pilot study of this possibility the original sam- 

 pling of SKbteiiuis was supplemented by addi- 

 tional specimens sorted at random from zoo- 

 plankton samples selected to represent both 

 extreme and intermediate geographical loca- 

 tions within the known distribution in each 

 ocean (Figure 20). For each specimen pleural 

 perforations were tallied from both left and 

 right sides of the entire body and summed with 

 counts of the tergal perforations to obtain a 

 maximum estimate referred to as the perfora- 

 tion number (PN). TL was also measured 

 routinely using procedures described in the 

 section on Material and Methods. It should be 

 noted that no attempt was made to determine 

 the existence of geographical variation in any 



999 



