PATTERN, NUMBER, VARIABILITY, AND TAXONOMIC 



SIGNIFICANCE OF INTEGUMENTAL ORGANS 



(SENSILLA AND GLANDULAR PORES) IN THE GENUS 



EUCALAMS (COPEPODA, CALANOIDA) 



Abraham Fleminger' 



ABSTRACT 



Methods for study of bilaterally symmetrical, serially homologous sets of integumental organs 

 comprising hair, peg, and pit sensilla and the pores of integumental glands as well as their 

 number and distribution in the genus Eiicalanus are described. 



A survey of these organs was carried out on geographically representative samples of the 

 17 discrete populations I recognize as valid species in the genus. The survey concentrated on 

 adult females, but smaller numbers of adult males and some younger copepodid stages were 

 also examined. Numbers and arrangement of these organs, estimates of variability, and their 

 relationship to total length were established for each species. Phenetic similarity in integu- 

 mental organ arrangement is shown to concur with other morphological features within the 

 genus. Comparison is also made between number and arrangement of integumental organs 

 and the geographical relationships among the members in each species group. Several new 

 species in the attenuatus group are described on the basis of integumental organs and geo- 

 graphical distribution. A preliminary study of geographical variation in the circumglobal, 

 broadly tropical species £. suhtenuis is used to estimate the general complexity of genetic 

 control and the use of these organs to study gene flow and population variability in plank- 

 tonic species. 



The integument of arthropods bears numerous 

 organs that fall into two general classes: 

 sensory receptors or sensilla, and glands. Sen- 

 silla are composed of one to several sensory 

 neurons and generally two accessory cells, the 

 latter forming the external features which may 

 be in the form of an outgrowth, i.e., a hair, a 

 cone, or a peg, or an ingrowth such as a pit or 

 plate organ with sensory cell bodies located 

 underneath (Laverack, 1969; Schneider, 1969; 

 Stiirckow, 1970). The regular presence of sen- 

 silla containing nerve fibers has been demon- 

 strated histologically in a variety of different 

 copepods (e.g., Fahrenbach, 1962; Elofsson, 

 1971). 



In terrestrial arthropods integumental glands 

 are highly variable in number, in distribution, 

 and in morphological detail (Eisner and Mein- 

 wald, 1966). Integumental glands described 

 from copepods tend to be rather simple sacs 



' Scripps Institution of Oceanography, University of 

 California at San Diego, La Jolla, CA 92037. 



underlying the integument and communicate 

 with the environment via a simple pore penetrat- 

 ing the integument (e.g., Clarke et al., 1962; 

 Fahrenbach, 1962; Park, 1966). 



On the body of copepods as in mystacocarids 

 and other arthropods, sensilla and glands are in 

 general distributed in bilaterally symmetrical 

 patterns that are somewhat redundant on suc- 

 cessive body segments, i.e., they appear to be 

 serially homologous (Sewell, 1929, 1932, 1947; 

 Fahrenbach, 1962; Hessler, 1969). It is highly 

 probable that chemical communication via integ- 

 umental organs, a widespread means for ex- 

 changing information among arthropods and 

 vertebrates (e.g., cf. Johnston, Moulton, and 

 Turk, 1970) is essential to copepods. Dioecious 

 and nonparthenogenetic copepods must locate 

 and correctly identify a potential mate without 

 visual aids. This search and contact procedure is 

 mediated by pheromones in Eiinjtemora and 

 called "mate-seeking behavior" (Katona, 1973). 

 Moreover successful culmination of the mating 

 act requires attachment of the spermatophore 



Manuscript accepted May 1973 



FISHERY BULLETIN: VOL. 71, NO. 4, 1973. 



965 



