FISHERY BULLETIN: VOL. 71, NO. 3 



"teeth"; second type small and hairlike; first 

 type extends about three-fourths the length of 

 the seta and decreases in size proximally; 

 second type covers distal one-fourth of seta; 

 spinules in both rows fit this description, although 

 those on one row are considerably smaller than 

 those on the other. Pleopods and uropods 

 developing, but not evident at this stage. 



Chioiioecetes opilio 



Prezoeae of C. opilio are identical in all 

 respects to those of C. bairdi. Stage I zoeae are 

 identical except for a few subtle differences in 

 abdominal morphology. The most obvious dif- 

 ference is in the length of the posterior lateral 

 spines on the third and fourth abdominal seg- 

 ments. In C. bairdi (Figure 2j, 1), the spines 

 overlap the adjacent segments by about one-third 

 the length of the spines. In C. opilio (Figure 

 2k, m), the spines on third segment barely 

 extend past the posterior margin of the fourth 

 segment, and those on the fourth segment do 

 not quite reach the posterior margin of the 

 fifth segment. Another, but small, difference is 

 the thickness and shape of the abdomen. In 

 C. bairdi the abdomen appears slightly deeper 

 than in C. opilio, especially in the areas of the 

 developing pleopods. Finally, the telson furca- 

 tions of C. opilio are about one-sixth longer than 

 those of C. bairdi. This last difference may be 

 difficult to distinguish clearly because the degree 

 of curvature of the furcations may vary con- 

 siderably among specimens of both species. 



COMPARISON OF 



NORTH PACIFIC ZOEAE OF 



THE SUBFAMILY OREGONIINAE 



The subfamily Oregoniinae comprises three 

 genera, Oregonia, Hijas, and Chionoecetes 

 (Garth, 1958). Zoeae of only a few species of 

 the Oregoniinae that occur in the North Pacific 

 are known. Hart (1960) reared and described the 

 zoeae of 0. gracilis and H. lyratus and showed 

 that they were separable from each other by 

 slight differences in size, color, and spinulation. 

 Aikawa (1937) and Kon (1967) described pre- 

 zoeae and Kurata (1963) described the first 



zoeal stage of C. o. elongatus, all from speci- 

 mens of known parentage. Kurata also described 

 zoeal stages of H. coarctatus alutaceus, but the 

 specimens were obtained from the plankton. In 

 the following discussion, I compare the mor- 

 phology of the first zoeal stages of C. bairdi 

 and C. opilio with the first zoeal stages of each 

 of the species mentioned above, emphasizing the 

 differences among them. 



Ron's (1967) prezoeae of C. o. elongatus were 

 nearly identical to my prezoeae of C. bairdi and 

 C. opilio except that he described the short 

 embryonic spine of the antennule as plumose, 

 whereas I did not. Aikawa's (1937) prezoeae 

 differed in several respects from mine and from 

 Kon's: his specimens did not have an embryonic 

 cuticle; the appendages and carapace spines 

 were partially or fully extended; and a lateral 

 knob was present only on the second abdominal 

 somite. Apparently, Aikawa described a prezoea 

 that had just cast its embryonic cuticle and was 

 in the process of metamorphosing to stage I. 



The stage I zoeae of C. o. elongatus described 

 by Kurata (1963) differed slightly from my 

 stage I zoeae of C. bairdi and C. opilio: the 

 lateral knobs on the third abdominal segment of 

 Kurata's stage I zoeae almost reached the pos- 

 terior margin of the segment, but in my larvae 

 they were considerably shorter. Also, in Kurata's 

 specimens the posterior lateral spines on the 

 abdomen were covered with spinules, whereas 

 I found only one or two minute spinules on 

 the lateral spines. Finally, the maxilla of 

 Kurata's larvae had 15 setae along the outer 

 margin of the exopodite in addition to the 

 single stout seta at the proximal end; the 

 larvae I studied had only 11 setae (rarely 12) 

 along the outer margin in addition to the stout 

 setae. This last difference may include pheno- 

 typic variation. J. Watson of the Fisheries 

 Research Board of Canada (pers. comm.) has 

 informed me that C. opilio in Atlantic waters 

 have 12 (rarely 13) setae in addition to the 

 stout seta. Unfortunately, Kurata did not 

 mention whether any variation of the number 

 of setae on the exopodite of the maxilla 

 occurred in his specimens. 



A comparison of Hart's (1960) specimens of 

 O. gracilis and H. lyratus with my specimens 

 of C. bairdi and C. opilio shows that morpho- 



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