PARACYCLOPS REVISION 



137 



on 1 slide, lcf dissected and mounted on 1 slide, 2d" cfundissected 

 and mounted on 2 slides. Dr H. Yeatman collection. These 

 specimens are deposited in USNM. 



Redescription of adult female 



Body length and width not including caudal setae given in Table 4. 

 Genital double-somite, second and third abdominal somites with 

 more dorsal surface ridges extending round sides onto ventral 

 surface than P. affinis (Figure 21A.B). Seminal receptacle divided 

 into broad anterior and posterior lobes, anterior lobe slightly nar- 

 rower than posterior (Figure 2 IB). 



Anal cleft with irregularly arranged spinules (Figure 21 A, D) and 

 with spinular row extending either side (arrowed in Figure 2 ID). 

 Caudal rami short about 2 times longer than broad (Figure 21 A, B); 

 terminal accessory seta (VI) longer than posterolateral seta (III) 

 (Figure 21 A). 



Antennule 1 1 -segmented. Segment 6 with spiniform seta. Setal 

 formula 8, 4, 2, 6, 4, 2, 2, 3, 4 + aesthetasc, 2 + aesthetasc. 7 + aesth- 

 etasc. Coxobasis of antenna (Figure 22C.D ) with complex ornamenta- 

 tion on caudal and frontal surfaces as figured; lacking spinular row 

 near base of inner setae on caudal surface (arrowed in Figure 22D). 



Basis of maxilliped with one spinular row on anterior surface and 



2 groups of spinules on posterior surface (Figure 22B). First 

 endopodal segment with 1 tiny spinule on anterior surface. 



Coxae of legs 2-4 with 2 spinular rows on anterior surface 

 (arrowed in Figures 23D, 24A.D) and with inner spine bearing 2 or 



3 large spinules posterolaterally (arrowed in Figure 24A); basis 

 without spinular row on anterior surface near inner margin. Coxa of 

 leg 3 with two mid-distal spinules on posterior surface. Intercoxal 

 sclerite of leg 4 with well developed spinular row (stronger than that 

 of P. affinis) along free margin and with spinular rows on anterior 

 and posterior surfaces (Figure 24C,D) 



Spine and seta formula as follows: 



may vary (cf. Figures 21 A and 2 ID). 



Coxa 



Basis 



Exopod 



Endopod 



Leg I 



Leg 2 

 Leg 3 



Leg 4 



I -I 



1-0 

 1-0 

 1-0 



I-1;I- 

 1-1:1- 

 1-1:1- 



1:111,5 

 1:111,1.5 

 1:111,1.5 

 1:111,5 



0-1:0-1:1.1,4 

 0-1:0-1:1,1.4 

 0-1:0-2:1.1,4 

 0-1:0-1:1,11.2 



Leg 5 with long inner spine about 4 times as long as segment; 

 outer spinulose seta simple, about half as long as inner spine and 

 without spinules at base (arrowed in Figure 21C). 



Description of adult male 



Differing from adult female as follows: Genital somite with 5 or 6 

 irregular dorsal surface ridges and 5 incomplete ventral surface 

 ridges; first to third free abdominal somites each with 3 complete 

 dorsal and ventral surface ridges (best seen in Figure 25 A, B). 



Antennule digeniculate (Figure 25CD). indistinctly 16-seg- 

 mented. Segment 1 armed with 8 setae plus an aesthetasc. Segment 

 10 (= ancestral segment XV) produced on one side into sheath 

 enclosing segment 11 ventrally: armed with 2 setae, one of which 

 pear-shaped and constricted at end in P. affinis but simple in P. 

 canadensis (arrowed in Figure 25D). 



VARIABILITY, FEMALES. Arrangements of spinules in the anal cleft 



Differential diagnosis. P. canadensis is distinguished from 

 other Paracyclops species by the combination of 11 -segmented 

 antennule, the surface ridges on the urosomal somites, the spinular 

 ornamentation on the anal cleft and by the possession of only 1 seta 

 on the second endopodal segment of leg 4. 



P. canadensis and P. affinis are very closely related but P. cana- 

 densis can easily be differentiated from P. affinis by the possession 

 of 4 spines on the terminal exopodal segment of leg 3 (Figure 24A), 

 the lack of spinules at the base of the outer seta of leg 5 (Figure 21 C); 

 by the presence of more surface ridges on the genital and following 

 2 free somites (Figure 21A.B); by the extent of the spinular row 

 either side of the anal cleft (Figure 21A.D); by the structure of inner 

 coxal spines of legs 2 to 4 (Figures 23D; 24A.D) and by the absence 

 of spinular rows near the inner margin of the basis of legs 2 to 4 

 (Figures 23D; 24A.D) 



Remarks 



P. canadensis has been reported from North America under the name 

 P. affinis by Yeatman (1959), Pennak ( 1963) and Smith & Fernando 

 (1977, 1978). However, comparison between European and North 

 American specimens of P. affinis led to the recognition here of P. 

 canadensis as valid species in North America. P. canadensis was 

 first recorded from North America in 1934 by Willey as a variety of 

 P. affinis ( Willey, 1 934). According to the rules of zoological nomen- 

 clature this taxon when raised to species rank must take Willey's 

 original variety name, becoming P. canadensis (Willey, 1934). 



DISTRIBUTION. P. canadensis occurs in the Eastern parts of Canada 

 and United States. 



Paracyclops dilatatus Lindberg, 1952 



(Figures 26-27) 



Platycyclops dilatatus Sars. 1927a [nomen nudum] 

 Paracyclops dilatatus ivanegai Monchenko, 1977 



ORIGINAL DESCRIPTION. Paracyclops dilatatus Lindberg, 1952: 

 Bull. Soc. zool. France, 77. 1 : p.8(). fig. 1 



TYPE locality. Caspian Sea. 



MATERIAL EXAMINED. Syntypes:ZoologiskMuseum. Oslo; 3 slides 

 F6236, F6237a and F62376 contain parts of 1 dissected &. One tube 

 F6237c contains female fragments. F6237a, 6237b and 6237c were 

 separated from one original slide by Dr. P. Frenzel in 1979. 



The type specimens of P. dilatatus Lindberg, 1952 were obtained 

 on loan from the Zoologisk Museum, Oslo. Unfortunately the 3 

 slides are not very informative and the available fragments of just 

 one female were insufficient to redescribe P. dilatatus in detail. 



REDESCRIPTION OF ADULT FEMALE 



Body length (Figure 26H) not including caudal setae is 840 um 

 (given by Lindberg, 1952 as approximately 770pm to 810pm). 

 Genital double-somite, second and third abdominal somites without 

 surface pits on dorsal and ventral surfaces (Figure 26H). Anal somite 

 with spinular row ventrally extending dorsally. Caudal rami (Figure 

 26K) short, about 2 times longer than broad. 



Table 4 Body length (BL) and width (BW) measurements (in pm) off! 



canadensis (N = nun 



iber of 



specimens measured). 







Locality Sex 



BL(mean ± SD) 





Range 





BL(mean ± SD) 



Range 



N 



Canada, Ontario 9 

 U.S.A. (West Virginia) 9 



684 ±45.2 

 713 ±47.6 





652-716 

 642-783 





257 ± 3.5 

 251 ±8.3 



254-259 

 242-264 



2 

 8 



