FISHERY BULLETIN; VOL 



rostral tip, which in my larva is bifid but in Sars' is 

 styliform, and the chela of the first pereopod, 

 which is completely developed in my larva but not 

 in Sars'. 



Stephensen ( 1912) described zoeal Stages I to V 

 from plankton that he provisionally identified as 

 "P. propinquus (?)" and Stage III zoeae (1916) as 

 "Spirontocaris-\ar\a No. 4." Berkeley (1931) not- 

 ed the close similarity of the "P. propinquus (?)" 

 specimens to zoeae of P. borealis from British Co- 

 lumbia waters. Stephensen (1935) later decided 

 that both "P. propinquus (?)" and "Spirontocaris- 

 larva No. 4" were actually zoeae of P. borealis. He 

 also compared his zoeae with fragments of a 

 specimen identified by Kr0yer as Dymas typus and 

 decided Kr0yer's specimen was a Stage IV zoea of 

 P. borealis. 



Comparing the description and figures of 

 Stephensen's ( 1912) zoeae and mine in general for 

 each stage, my zoeae are slightly more advanced 

 than Stephensen's. In my Stage I zoeae the anten- 

 nal scale bears 19 plumose setae; the basipodite 

 and coxopodite of the maxillule bear 9 + 1 and 9 

 spines, respectively; the endopodite of the first 

 maxilliped is segmented; and the exopodites of 

 maxillipeds 1, 2, and 3 bear 6. 14, and 16 natatory 

 setae, respectively. In Stephensen's Stage I zoeae 

 the antennal scale bears only eight or nine 

 plumose setae; the basipodite and coxopodite of 

 the maxillule bear five and six spines, respec- 

 tively; the endopodite of the first maxilliped is not 

 segmented; and the exopodites of maxillipeds 1, 2, 

 and 3 bear 4, 10, and 10 natatory setae, respec- 

 tively. In Stage II, the relative difference in 

 number of setae and spines between my zoeae and 

 Stephensen's remains essentially the same, except 

 in my zoeae the exopodites of pereopods 1, 2, and 3 

 bear 16, 16, and 12 setae, respectively, whereas in 

 Stephensen's zoeae they each bear 18 setae. In 

 Stage III, the rostrum of my zoeae bears only a 

 single tooth and the antennal flagellum is eight- 

 jointed, but in Stephensen's zoeae the rostrum 

 bears as many as three teeth and the antennal 

 flagellum is notjointed. In Stage IV, the rostrum of 

 my zoeae bears six or seven teeth, the antennal 

 flagellum is 15-segmented, and the telson bears 

 eight pairs of spines whereas in Stephensen's 

 zoeae the rostrum bears only four teeth, the an- 

 tennal flagellum is still unsegmented, and the tel- 

 son bears only seven pairs of spines. In Stage V, 

 the most obvious difference is that the pleopods 

 are segmented in my zoeae but not in Stephen- 

 sen's. 



In his 1916 report, Stephensen described an ad- 

 ditional larva which he considered the sixth stage 

 oi P. propinquus G. O. Sars; later (1935) he decided 

 it was P. borealis. According to Stephensen, this 

 stage closely resembles his Stage V zoeae, differ- 

 ing primarily in the left second pereopod being con- 

 siderably longer than the right, and, for both sec- 

 ond pereopods, the joint at the distal end of the 

 carpopodite being complete. In my larvae, mor- 

 phological change from Stage V to Stage VI is 

 sufficiently pronounced that I consider the sixth 

 stage to be the megalopa. If Stephensen was cor- 

 rect in assuming his specimen to be a sixth stage 

 zoea, then P. borealis in Greenland waters has at 

 least six zoeal stages compared with only five zoeal 

 stages in Alaska waters. 



In her classic study of pandalid larvae from 

 British Columbia waters, Berkeley (1931) de- 

 scribed and figured P. borealis Stage I zoeae reared 

 in the laboratory and Stages II-VI collected from 

 plankton. Her larvae follow a pattern of develop- 

 ment similar to my larvae but each stage is less 

 well developed. For instance, she described the 

 antennal flagellum in her Stage I zoeae as tipped 

 by a simple seta whereas in my zoeae it is tipped by 

 a spinulose spine, and she neither figured nor de- 

 scribed the spinous seta which my zoeae bear on 

 the protopodite at the base of the flagellum. Also, 

 the exopodite of the maxilla of her Stage I zoeae 

 bears 8-10 long simple setae and has no trace of a 

 proximal expansion whereas in my zoeae the 

 exopodite of the maxilla bears 11 long plumose 

 setae as well as one longer, thicker seta at the 

 proximal end which is slightly expanded. In Stage 

 II, the outer flagellum of the antennule of Berke- 

 ley's zoeae is figured as bearing only three aes- 

 thetascs distally whereas my zoeae bear eight. The 

 proximal expansion of the exopodite of the maxilla 

 is "just appearing" in Berkeley's Stage II but in 

 mine it is distinctly expanded. Moreover, she de- 

 scribed the telson as being still indistinctly seg- 

 mented from the sixth abdominal somite but in my 

 zoeae it is always distinctly segmented at Stage II. 

 Berkeley's Stage III zoeae are essentially identical 

 to mine as far as can be determined from her de- 

 scription. Her Stage IV zoeae have four small 

 teeth at the base of the rostrum, the pleopods are 

 without joints, and there is no epipodite on the 

 second maxilliped. In my Stage IV zoeae, the ros- 

 trum usually has six teeth, the pleopods are 

 jointed, and an epipodite occurs on the second 

 maxilliped. In Stage V, the rostral tip of Berke- 

 ley's zoeae is still styliform. There is no evidence 



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