FLEMINGER: INTEGUMENTAL ORGANS IN GENUS EUCALANUS 



of the species emanate largely from the absence 

 of distinctive sexually modified appendages, 

 the few available meristic characters in setation 

 and the widespread dependence of the existing 

 taxonomic system upon relatively subtle shapes 

 and i)ro))ortions of segments and tagmata un- 

 supported by rigorous estimates of variability. 

 Difficulties and inconsistencies associated with 

 the rank of the taxa in the genus Eucalaiiiis, 

 notably in the elongatus group, might be the 

 product of several factors: e.g., the lack of accu- 

 rate data on geographical distribution, uncer- 

 tainties about the significance of morphological 

 differences among the subspecies, the wide- 

 spread lack of an adequate basis for viewing the 

 planktonic taxon in the perspective of a biologi- 

 cal population. 



For example, questions or expressed doubts 

 challenge the validity of separating E. pileatits 

 from sKbcrassKs, and the two have often been 

 confused with niouachus (Deevey, 1960; Grice, 

 1962; Vervoort, 1963; Lang, 1965). Confusion 

 about sitbteuiiis appears to trouble some 

 (Fukase, 1957). Awareness of variation and 

 taxonomic complexity within the nominal 

 species atteimatiiK has been noted frequently 

 (Sewell, 1947; Tanaka, 1956; Brodsky, 1962; 

 Lang, 1965; Park, 1968), and similar questions 

 must be raised regarding dcutatits (Fleminger, 

 unpublished data). Finally, a point must be 

 made with regard to the elongatus complex. 

 Three decades have passed since Johnson's 

 (1938) perspicacious revision based on so few 

 data, decades of increasing oceanographic activ- 

 ity and the accumulation of geographical and 

 morphological observation on these common 

 forms. Considering our increased experiences 

 and understanding the logic of justification for 

 the general practice of regarding inerniis as 

 a full species but continuing the two subspecies 

 of elongates and the two subspecies of bniigii 

 escapes me. On the basis of both morphology 

 and geography the known similarities and dif- 

 ferences between iucrmis and its two cognates 

 and those between the subspecies of each of 

 these cognates are about equal. 



As part of an unpublished doctoral disserta- 

 tion, Lang (1965) presented a taxonomic review 

 and study of the distribution of Encalaniis in 

 the Pacific Ocean based on plankton samples 



from the Scripps Institution of Oceanography 

 Zooplankton Collections. Lang's data on the 

 elongatus complex, published in 1967, contrib- 

 uted appreciably to our knowledge of geo- 

 graphical relationships among its jjopulations. 

 Though providing considerable evidence favor- 

 ing extension of the revision initiated by 

 Johnson (1938), his use of subspecies was 

 retained. Expressed dissatisfaction with separa- 

 tion of pileatuH and subcrassus and the con- 

 siderable variation encountered in attenu- 

 ati(s s.l. were noted in the unpublished portion 

 of Lang's dissertation. 



My attempts to strengthen the Eiicahuius 

 section of Lang's manuscript for publication 

 using the material on hand to clarify unresolved 

 issues were unsuccessful. Two issues emerged: 

 Resolution of the difficulties depended on 1) 

 expanding geographical representation to en- 

 compass the world ocean and 2) the need to 

 develop more reliable morphological characters 

 for distinguishing the reproductively isolated 

 populations within the genus. As conditions 

 permitted, I gathered geographic records and 

 specimens of Encalaiitis in conjunction with 

 global studies on other calanoid genera includ- 

 ing ClaKsocakunis and Pout ell iiia (Frost and 

 Fleminger, 1968; Fleminger and Hulsemann. in 

 press). In addition, I began to examine various 

 structures of Eucalanus at relatively high mag- 

 nifications (200 X to 600 X). Useful characters 

 were found in the female genital segment, es- 

 pecially in the shai^e and arrangement of the 

 seminal receptacles, and in the male fifth legs. 

 For example, general similarities in the semi- 

 nal receptacles provided a jiromising basis for 

 phylogenetic groupings within the genus and 

 a dependable means for sei)arating at least 

 some of the species of the jiileatus grouji (Fig- 

 ure 1). 



In the course of my survey, distinctive 

 patterns in the distribution of integumental 

 organs on the urosome became apparent. Recall 

 of Sewell's (1947) use of these features to sup- 

 port his separation of attcniiatiis and pscKclat- 

 tenHati(s prompted development of procedures 

 described below to map integumental organs on 

 dorsal and lateral surfaces of all body segments. 

 The results provided the means for separating 

 regional jiopulations. species, and species 



967 



