CALANOID COPEPODS OF THE GENERA 

 SPINOCALANUS AND MIMOCALANUS FROM THE 

 CENTRAL ARCTIC OCEAN, WITH A REVIEW OF 

 THE SPINOCALANIDAE 



DAVID M.DAMKAER' 



ABSTRACT 



The family Spinocalanidae includes small to medium-sized marine calanoid copepods 

 belonging to the genera Spinocalanus, Monacilla, Mimocatanus, and Teneriforma. All species 

 are deep-living and often comprise a large proportion, or even a majority, of the copepods in 

 deep samples. In spite of their prevalence, definitive knowledge of the Spinocalanidae has lag- 

 ged behind that of other copepod groups because adequate collections from deep water have 

 been few, and specimens from widely separated localities have seldom been compared. Most im- 

 portant, however, is the fact that the fragility of the specimens makes them very difficult to 

 study; most investigators attempting to describe or identify Spinocalanidae have indicated that 

 their specimens were damaged and incomplete. 



The present study is based on collections of zooplankton from Fletcher's Ice Island, T-3, in the 

 Canadian Basin of the Arctic Ocean in 1967-68. The seven species of Spinocalanidae from these 

 collections are redescribed, and their vertical distributions are discussed, based on series of 

 samples from discrete depth intervals to 3,000 m. 



The systematics of the Spinocalanidae has been reconsidered, using characters in addition to 

 those most commonly lost in sampling. All published descriptions and records are discussed. 

 Several critical type specimens and specimens forming the bases of widespread records have 

 been examined and are redescribed. Keys to the genera and all of the species have been 

 prepared, with the goal of enabling an investigator to identify even damaged specimens. Many 

 named species or forms have been placed in synonymy, and two new species {Spinocalanus 

 terranovae and Mimocalanus heronae) are described. The family is now considered to comprise 

 .12 species, distributed as follows: Spinocalanus (19), Monacilla (4), Mimocalanus (8), and 

 Teneriforma (1). 



INTRODUCTION 



The family Spinocalanidae includes small to 

 medium-sized marine calanoid copepods belonging to 

 the genera Spinocalanus (42 named species or forms), 

 Monacilla (8), Mimocalanus (8), and Teneriforma (1). 

 The Spinocalanidae have been difficult to study 

 because they are prone to damage in sampling, 

 resulting typically in the loss of the first antennae and 

 most swimming legs. Grice and Hulsemann (1965) 

 said that "the identification of species of 

 Spinocalanus was difficult as almost all the 

 specimens examined were damaged .... This appears 

 to be the case for other collections also because most 

 previous descriptions are accompanied by few il- 

 lustrations .... Most of the species in this genus need 



'Systematics Laboratory, National Marine Fisheries Service. 

 NOAA, Washington, D.C. 20560; present address: Pacific Marine 

 F^nvironmental Laboratory, NOAA, University of Washington 

 WB-10. Seattle, WA 9819.5. 



to be restudied and redescribed, a task which will be 

 difficult unless specimens in better condition than the 

 present ones can be obtained." This fragility and 

 rather generalized body form have given the 

 Spinocalanidae a potential to be overlooked or ig- 

 nored in surveys of deep-living copepods, even though 

 they often comprise a large proportion, or even a ma- 

 jority, of the copepods in deep samples. Also, as in 

 many other calanoids, adult males are scarce. John- 

 son (1963a), in discussing this group, said that "the 

 clarification of the position of these males and the 

 whole complex of Spinocalanus species requires ad- 

 ditional material and much more thorough study." 



Definitive knowledge of the Spinocalanidae has also 

 lagged behind that of other copepod groups because 

 the species are mostly deep-living; adequate collec- 

 tions have been few, and specimens from widely 

 separated localities have seldom been compared. 

 Most have been collected by towing plankton nets 

 vertically from great depths to the surface, so that 

 depth limits of the species are difficult to define. 



