FISHERY BULLETIN: VOL. 71. NO. 4 



Table 7. — Comparison by Student's /-test of mean TN values of samples of adult female subtenuis 

 grouped regionally as in Figure 21 in segments of 60° of longitude. 



The nine sets appear to vary independently 

 of one another, some showing unusually high 

 or low frequencies of absence in one or two of 

 the three oceans. In some sets the frequency of 

 absence in one ocean differs significantly from 

 that elsewhere (Figure 22a, b; Table 8). Within 

 each set perforations tend to be absent at simi- 

 lar frequencies. Genetic linkage is suggested by 

 the similar deviations in the Pacific sample 

 affecting the following sets: Mxl-T-a-/3, 4, r3, 4; 

 Mxp-T-/1, 2, rl, 2; ThII-P-/al, ral; Thlll-P- 

 ?al, ral; and ThIV-P-/al. ral. 



Also unique to the Pacific sample is the more 

 frequent occurrence of four perforations on the 

 somite of the first maxilla (Mxl-T-d-/l, 2, rl, 2). 

 The Indian Ocean sample is distinguished by a 

 relatively infrequent appearance of the set of 

 perforations on the somite of the second antenna 

 (A2-T-a-/l, 2, rl, 2). The Atlantic sample shows 

 relatively few absences on the Mxl somite (Mxl- 

 T-C-/1, 2, rl, 2) and on Thll (ThII-T-a-/2, 3, r2, 

 3). 



In an individual specimen perforations are 

 often absent in pairs rather than in full sets 

 though right and left pairs in a set tend to show 

 similar frequencies in the sample. Absences of 

 peg and pore combinations are usually bilateral 

 and affect both the right and left sides of a parti- 

 cular set. Absences of pairs consisting of a pit 

 sensillum and a pore may be bilateral but more 

 frequently affect only one side in a specimen. 

 An appreciable portion of the variability in 

 subtenuis emanates from losses among such 

 tergal pairs occurring sequentially on the two 

 maxillary somites. An individual specimen may 

 show losses that alternate in successive sets 

 from either left to right or the reverse. A notice- 

 able trend in losses toward unbalanced symme- 

 try was found only in the case of Mxl-T-b-/l, 2, 



rl, 2. Indian and Atlantic samples showed more 

 absences on the right side and Pacific samples 

 had a higher frequency of absence on the left 

 side, but the differences are significant ( X - test 

 for homogeneity) only in the case of the Indian 

 Ocean sample (Table 9). Critical examination 

 for patterned variation among specimens using 

 larger samples may prove to be especially useful 

 for genetic studies on natural and laboratory 

 populations of planktonic copepods. 



Despite the relatively frequent absences, each 

 of the 110 specimens of subtenuis comprising 

 the combined global sample exhibited a re- 

 presentative perforation pattern permitting 

 identification to species by this feature alone. 

 Also noteworthy is the qualitative resemblance 

 in characters distinguishing the geographical 

 populations of subtenuis and differences separa- 

 ting parki from langae. As in subtenuis few 

 perforations distinguish these allopatric tem- 

 perate species of the attenuatus group from one 

 another, and the sites involved are also restricted 

 to a limited portion of the body (i.e., the abdo- 

 men and especially Abd.IV-V). The parallels 

 emphasize the likelihood of appreciable genetic 

 discontinuity separating Atlantic, Indian, and 

 Pacific populations of subtenuis that deserves 

 more intensive study. 



SIZE AND PERFORATION NUMBER 



The perforation number (PN), i.e., the num- 

 ber of designated sites in the species observed 

 on each specimen is derived from a meristic 

 complex of integumental organs. The two organ 

 systems, sensilla and glandular pores, are 

 arranged in serially homologous sets that are 

 distributed on all body segments. Showing 

 phylogenetic and species specific patterns, they 



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