FISHERY BULLETIN VOL. 77. NO. 3 



during later stages, usually at the molt to the 

 megalopa. In Table 1, poorly developed pereopods 

 in Stage I are unsegmented pereopods that are 

 directed anteriorly under the cephalothorax. Usu- 

 ally pereopods become functional by Stage III. 



Denticles on the carapace and spines on the ab- 

 dominal somites are most prevalent in Stage I and 

 tend to disappear during larval development. 

 Thus, inPandaltis platyceros most ofthe denticles 

 and spines have disappeared by Stage III; in P. 

 stenolepis and P. tridens most have disappeared by 

 Stage VI. 



For most pandalid shrimp larvae, the typical 

 number of telsonic spines is 7 -I- 7 in Stage I and 8 

 -^ 8 in later stages. In the latest stage another pair 

 may be added. The total nurnber of telsonic spines 

 of P. kesslen varies from 30-34 (Stage I) to 14-15 

 (Stage V); Pandalopsis coccinata has 55-56 tel- 

 sonic spines inStageI(Kurata 1955, 1964). Stage I 

 Pandalus kessleri and Pandalopsis coccinata usu- 

 ally have 16 + 16 and 28 + 28 telsonic spines, 

 respectively (Table 1). 



The number of larval stages oi'Pandalopsis dis- 

 par, P. coccinata , Pandalus tridens. and P.jordani 

 has not been verified. Seven zoeal stages are 

 known for Pandalopsis dispar and Pandalus tri- 

 dens. Based on morphological development. Stage 

 VII ofPandalopsis dispar is probably the last lar- 

 val stage. Pandalus tridens probably has an addi- 

 tional stage before the larvae molt to the first 

 juvenile stage. Only the finst zoeal stage of Pan- 

 dalopsis coccinata is known, but development of 

 this stage is so far advanced that only one or, at the 

 most, two more stages probably appear before the 

 larvae molt to the first juvenile stage. For Pan- 

 dalus jordani . I have estimated six larval stages 

 based on development of larvae of morphological ly 

 similar species, P. borealis, P. goniurus. and P. 



tridens. rather than the 1 1-13 stages obtained by 

 ModinandCox ( 1967) or the 8+ stages obtained by 

 Lee (1969) in the laboratory. Modin and Cox 

 (1967) noted that the 11-13 larval stages of P. 

 jordani obtained by them in the laboratory were 

 nearly twice the number of larval stages of the 

 closely related P. borealis. Artificial laboratory 

 conditions may have caused a greater number of 

 larval stages than natural conditions. 



The numbers of larval stages cited in Table 1 

 include the megalopa stage because the transition 

 from zoea to megalopa is not always abrupt and 

 may extend over several molts. For example, P. 

 hypsinotus has functional pleopods in Stage VII, 

 but other morphological characteristics normally 

 associated with postzoea occur earlier (Haynes 

 1976). Also, the number of larval stages of some 

 species vary slightly depending on geographical 

 origin. Larvae of P. hypsinotus, P. goniurus, and P. 

 borealis from the western North Pacific Ocean and 

 P. borealis from British Columbia waters have one 

 or two more stages than larvae of these species 

 from Alaskan waters (Haynes 1976, 1978, 1979). 

 Geogi'aphical variation in larval morphology has 

 not been verified for other species of pandalids 

 from the North Pacific. 



The number of larva! stages given in Table 1 

 refers to development in the sea rather than in the 

 laboratory. Development in the laboratory often 

 results in molt retardation and extra stages. Al- 

 though the number of molts required to reach a 

 specific point in development may vary in wild 

 pandalid shrimp (Haynes 1978), the stages are, for 

 the most part, remarkably constant and limited in 

 number (Gurney 1942). 



For identification purposes, pandalid shrimp 

 larvae of the North Pacific Ocean can be catego- 

 rized into two groups on the basis of morphological 



Table l . — Principal morphological characteristics and number of larval stages of known larvae of pandalid shrimp ofthe North Pacific 

 Ocean. + = yes; - = no. (Only the most complete references on larval morphology are given.) 



Species 



Pereopods 



bearing 

 exopodites 



Pereopods poorly 

 developed 

 in Stage I 



Spines on 



abdominal 



somites 



Denticles 



on carapace 



margin 



No of telson 

 spines in 

 Stage I 



No of 

 larval 

 stages 



Pandalopsis coccinata 



P dispar 



Pandalus kesslen 



P danae 



P hypsinotus 



P platyceros 



P tridens 



P stenolepis 



P borealis 



P goniurus 



P lordani 



1-2 

 1-2 

 1-2 

 1-2 

 1-2 

 1-3 

 1-3 

 1-3 

 1-3 

 1-3 

 1-3 



' References 1 ) Berkeley ( 1 930) ; 2) Needier ( 1 938) . 3) Kurata ( 1 955) : 4) Kurata ( 1 964) : 5) Ivanov ( 1 965) , 6) Modm and Cox ( 1 967) , 7) Lee ( 1 969) . 8) Ivanov ( 1 971 ) . 

 9) Price and Chew |1972). 10) Haynes (1976), 11) Haynes (1978); 12) Haynes (1979). 13) this repon 



638 



