FISHERY BULLETIN VOL 77. NO. 1 



the carapace, both of which persist to Stage V in P. 

 stenolepis but never occur in P. borealis. 



Larvae of P. jordani have been described from 

 specimens reared in the laboratory. Compared 

 with development of similar species, Modin and 

 Cox (1967) and Lee (1969) obtained more stages 

 (11-13 and at least 8, respectively) than expected 

 for larvae of P.jordani from plankton. Because of 

 the possibility of these extra stages, only Stage I 

 zoeae of P. borealis and P. jordani can be com- 

 pared. Upon hatching, zoeae of P. borealis are 

 slightly more developed than zoeae of P. jordani. 

 For instance, in Stage I P. jordani, the exopodites 

 of maxillipeds 1,2, and 3 bear 4, 9-11, and 11 or 12 

 natatory setae, respectively; the left mandible 

 bears no lacinia mobilis; the basipodite of the 

 maxillule bears six spines terminally; and the 

 scaphognathite of the maxilla bears seven to nine 

 setae along its outer margin. In Stage! P. borealis, 

 maxillipeds 1, 2. and 3 bear 5 or 6, 13 or 14, and 16 



natatory setae, respectively; the left mandible 

 bears a single lacinia mobilis; the basipodite of the 

 maxillule bears 9 spines terminally; and the 

 scaphognathite of the maxilla bears 12 setae along 

 its outer margin. Beyond Stage I, the most distin- 

 guishing difference between zoeae of P. jordani 

 and P. borealis seems to be the development of the 

 rostral tip which in zoeae of P. jordani remains 

 acuminate but in zoeae of P. borealis becomes bifid 

 in later stages. 



In an earlier report (Haynes 1978), I described 

 larvae of P. goniurus reared in the same manner 

 as larvae of P. borealis described here. Larvae of 

 both species are morphologically similar, espe- 

 cially in early stages, and often occur together in 

 plankton. To facilitate identification of larvae of 

 these two species, the most readily observable 

 morphological differences are listed by stage in 

 Table 1. Larvae of P. goniurus are characteristi- 

 cally smaller than those of P. borealis and in 



Table i.- 



-Morphological characteristics for distinguishing between larvae of Pandalus borealis and P. goniurus reared in situ in 



Kachemak Bav. Alaska. 



Stage and characteristic 



P borealis 



P goniurus 



Stage I zoea 



Mean total length (mm) 



No of plumose setae tnnging antennal scale 



No ot spines terminally on basipodite of 



maxillule 

 No ot plumose setae on scapliognathite (in 



addition to single proximal seta) 

 No of nalaory setae on exopodites 

 fVlaxillipeds 1, 2, 3, 

 Stage II zoea 

 Mean total length (mm) 

 No of plumose setae fringing antennal scale 

 No of natatory setae on exopodites: 

 Maxillipeds 1. 2. 3. 

 Pereopods 1. 2. 3. 

 Stage III zoea 

 Mean total length (mm) 

 Rostrum 



Antennal flagellum 

 Antennal scale 

 Stage IV zoea 

 Mean total length (mm) 

 Rostrum 

 Antennal flagellum 



Propodite of pereopod 2 



Pleopods 



Stage V zoea 

 Mean total length (mm) 

 Rostrum 



Chela ot pereopod 2 

 Pleopods 



Stage VI (megalopa) 

 Mean total length (mm) 

 Rostrum 



6 7 (range 6 5-7 3, 25 specimens) 



19 



5-6. 13-14, 16 



7 5 (range 6 7-8 2, 25 Specimens) 

 About 25 



7, 16, 18 

 16, 16, 12 



9 5 (range 9 0-100, 10 specimens) 



1-2 conspicuous teeth 



8- segmented 



About 30 setae 



13 (range 12 6-13 2; 10 specimens) 



6-7 dorsal teeth 



About 1'?  scale, extending past 



tips of plumose setae 



Projected antenorly about '2 length 



of dactylopodite 



Segmented, pleopod 2 about '; height 



ol abdominal somite 



16 (range 15 2-17 i. 10 specimens) 

 9-12 dorsal teeth, tip bifid. 4-5 

 partially developed ventral teeth 



Fully formed 



With appendices internae, fringed 



with plumose setae, pleopod 2 as 



long or longer than height of 



abdominal somite 



18 5 (range 17 4-20.2, 5 specimens) 

 13-15 dorsal teeth. 

 6-7 ventral teeth 



4 (range 3 7-4 2, 

 9 



10 specimens) 



5 9 {range 4 5-5 3. 10 specimens) 



About 19 



6, 12. 14 

 12, 8. 8 



6 2 (range 6 0-6 6, 10 specimens) 



1 inconspicuous tooth 

 3- segmented 

 About 20 setae 



7 7 (range 6 8-8 3. 10 specimens) 



2 dorsal teeth 



Longer than scale but not extending 



past tips ol plumose setae 



Projected antenorly only slightly 



Unsegmented, pleopod 2 about ^ a 

 height of abdominal somite 



10 3 (range 8 2- 11 .3: 10 specimens) 



5-6 dorsal teeth; tip not bifid (but 



may show slight protuberance), no 



ventral teeth 



Not fully formed, propodite extension 



about ^ 2 length of dactylopodite 



Without appendices internae; 2-4 



simple setae terminally, pleopod 2 



about 2 3 height of abdominal somite 



138 (range 11 1-15 8, 6 specimens) 

 8-9 dorsal teeth. 

 4-5 ventral teeth 



172 



