152 



S. KARAYTUG AND G.A. BOXSHALL 



Leg 5 (Figure 34C) comprising single free segment, armed with 1 

 long (almost twice as long as inner spine) well developed outer 

 spinulose seta, 1 serrate-like strong inner spine, one spinulose seta in 

 middle (slightly shorter than outer seta). Leg 6 (Figure 34A) repre- 

 sented by 1 plumose seta and 2 tiny spinules dorsolaterally 



ADULT MALE. Unavailable for redescription. 



Differential diagnosis. This endemic Baikalian species can 

 easily be distinguished from other Paracyclops species by the 

 absence of the fringe of elongate setules (arrowed in Figure 34A) 

 usually present around the posterior margin of the fifth pedigerous 

 somite in the female; by its very short caudal rami (Figure 34A,B), 

 by the structure of leg 5 (Figure 34C) and by the highly ornamented 

 setal elements on the female antennule (Figure 35 A, B). 



Remarks 



This species is remarkable by virtue of the highly ornamented setal 

 elements on nearly all the appendages. Mazepova (1961) described 

 this Baikalian endemic as a subspecies but later (Mazepova. 1978) 

 treated it as a distinct species. 



Distribution. P. baicalensis is endemic to Lake Baikal. 



Paracyclops yeatmani Daggett & Davis, 1974 



(Figures 38-42) 



non Paracyclops yeatmani: Mahoon & Zia, 1985. 



Original DESCRIPTION. Paracyclops yeatmani Daggett & Davis, 

 1974: Can. J. ZooL, 52, (2) : 301-304. ' 



Type LOCALITY. Canada, Newfoundland, Highway 5 between 

 Bay Bulls and Witless Bay. 



TYPE MATERIAL. Type material of P. yeatmani was obtained from 

 the Canadian Museum of Nature. CMNC1984-1 121, paratypes, 2 

 microscope slides of 2cf cfdissected between prosome-urosome. 

 CMNC 1984- 1122, paratypes, 1 vial, 4 9 9. 1 9 dissected. 



Other material. 1 9 undissected and mounted on one slide; 

 1 9 dissected and mounted on one slide from the type locality. Dr. H. 

 Yeatman collection, 11 September 1972. 



Redescription of adult female 



Body length (um), not including caudal setae, 778-798 (given by 

 Daggett & Davis as 750-860), mean = 785, n = 3. Body width 301- 

 331, mean = 319, n = 3. Prosome (Figure 38C) with cephalothorax 

 longer than 3 free pedigerous somites. Genital double-somite, sec- 

 ond and third abdominal somites without surface ornamentation 

 and posterior margins of abdominal somites more conspicuously 

 serrated ventrally than dorsally (Figure 38A,B). Seminal receptacle 

 divided into broad anterior and posterior lobes as figured (Figure 

 38B). Anal somite with spinular row ventrally extending dorsally 

 midway along either side of anal operculum (Figure 38A,B). Anal 

 operculum smooth; row of spinules present in anal cleft, either side 

 of midline. Caudal rami (Figure 38A,B) about 3.1 times longer than 

 broad; anterolateral seta (II) plumose with spinules originating at 

 base, extending midway along dorsal surface (Figure 38A); terminal 

 accessory seta naked (VI) and about 3 times longer than posterola- 

 teral seta (III). Outer terminal seta (IV) and inner terminal seta (V) 

 well developed and heterogeneously ornamented (Figure 38C). 



Antennule 11 -segmented (Figure 40A). Segment 3 with partial 

 suture line. Segment 5 with spiniform seta. Segment 8 with short 

 aesthetasc (see inset Figure 40A). Apical segment with aesthetasc 

 fused to adjacent seta at base, and another aesthetasc located distally 

 on anteroventral margin on segment 10. Setal formula 8, 4, 8, 4, 2, 2, 



3, 2 + aesthetasc, 2, 2 + aesthetasc, 7 + aesthetasc. Coxobasis of 

 antenna (Figure 40D,E) with complex ornamentation on caudal and 

 frontal surfaces as figured. 



Proximal segment of maxillulary palp ornamented with 3 minute 

 spinules (arrowed in Figure 39F). Syncoxa of maxilliped (Figure 

 39A,B) without spinules near setal bases (arrowed in Figure 39B). 

 Basis ornamented with 2 transverse spinular rows near outer distal 

 angle and with 2 irregular spinular rows near bases of medial setae 

 (arrowed in Figure 39A). First endopodal segment with 4 spinules. 



Coxaofleg 1 (Figure 4 1C) with spinular row near outer margin on 

 posterior surface; intercoxal sclerite without spinular rows on ante- 

 rior and posterior surfaces. Intercoxal sclerite of leg 2 (Figure 42A) 

 ornamented with spinular rows on anterior and posterior surfaces; 

 coxa with spinular row near outer margin on posterior surface; first 

 endopodal segment with spinular row on posterior surface. Intercoxal 

 sclerite of leg 3 (Figure 42B,C) with spinular row on anterior surface 

 and with 3 spinular rows on posterior surface; coxa with spinular 

 row near outer margin on posterior surface; first endopodal segment 

 with spinular row on posterior surface. Intercoxal sclerite of leg 4 

 with few spinules on anterior surface (Figure 41 B) and with 3 long 

 spinular rows on posterior surface (Figure 41 A); inner coxal seta 

 with group of setules mainly originating posteriorly; coxa with 

 complex ornamentation on posterior surface as figured (Figure 

 41 A); basis with setules along inner margin. 



Spine and seta formula as follows: 



Coxa 



Basis 



Exopod 



Endopod 



Legl 



0-1 



1-1 



1-1:1-1 ;III,5 



0-1:0-2:1.1.4 



Leg 2 



0-1 



1-0 



1-1:1-1 ;III,I.5 



0-1:0-2:1.1,4 



Leg 3 



0-1 



1-0 



1-1:1-1:111.1,5 



0-l;0-2;l,I,4 



Leg 4 



0-1 



1-0 



1-1:1-1 ;II,I,5 



0-1:0-2:1,11,2 



Leg 5 (Figure 38D) comprising single free segment, armed with 

 short outer plumose seta (shorter than inner spine), 1 serrate-like 

 strong inner spine, and 1 plumose seta in middle about twice as long 

 as inner spine. Base of middle seta produced. Leg 6 (Figure 38A) 

 represented by 1 long plumose seta and 2 tiny spinules dorsolaterally. 



Description of adult male 

 Antennule (Figure 40C) 16-segmented. The poor condition of the 

 slides and the orientation of the antennule made it impossible to 

 confirm all details of the setation pattern. 



Differential diagnosis. P. yeatmani can easily be differentiated 

 from other Paracyclops species by the combination of the following 

 characters: the produced base of the middle seta of leg 5 (Figure 

 38D). the spinules originating at the base of the anterolateral seta 

 (II), extending midway along the dorsal surface of caudal rami 

 (Figure 38 A), the very long, naked terminal accessory seta which is 

 about 3 times longer than the posterolateral seta (Figure 38A), the 

 three rows of long spinules on the posterior surface of intercoxal 

 sclerite of leg 4 (Figure 41A) and its 1 1-segmented antennule. 



Remarks 



Paracyclops yeatmani Mahoon & Zia, 1985 is a junior primary 

 homonym of P. yeatmani Dagget & Davis, 1974 and therefore an 

 invalid name (ICZN Article 57 (b)). This species was based on 

 juvenile stages and belongs to a species not related to P. yeatmani 

 Dagget & Davis, 1974. It is regarded here as species incertae sedis 

 in the Cyclopidae. 



There are only three species with 1 1-segmented antennules in the 

 genus Paracyclops; the other two being P. affinis and P. canadensis. 

 However, the 1 1-segmented state is not homologous in P. yeatmani 

 and in P. affinis-canadensis group. Segments 3 and 4 (ancestral 



