FISHERY BULLETIN: VOL. 83, NO. 3 



crangonid larvae, the peduncle of the antennule (Fig. 

 IB, ap) is unsegmented in Stage I and becomes three 

 segmented later, usually in Stage II. The exceptions 

 are Stage I Sderocrangon boreas, which has a 3-seg- 

 mented antennule; Stage II Eualiis suckleyi and E. 

 fabricii, which have 2-segmented peduncles; and 

 both Stages I and II Lebbeiis polaris and L. groenlan- 

 dicus, which have unsegmented peduncles. 



In Stage I pandalid and hippolytid larvae, the inner 

 flagellum (Fig. IB, if) of the antennule is usually a 

 plumose seta, whereas in Stage I crangonid larvae, it 

 is usually a setose spine. The only described excep- 

 tions are Stage I larvae of Pandaltis prensor, Sdero- 

 crangon boi'eas, S. salebrosa, and 5. zenkeiitchi. In 

 Stage I Pandalus prensor, the inner flagellum is 

 spine shaped and has a few simple setae medially. In 

 Stage I S. boreas, S. salebrosa, and S. zenkevitchi, 

 the inner flagellum is an oblong projection that is 

 naked except for a few minute, simple setae termi- 

 nally (Birshteyn and Vinogradov 1953; Makarov 

 1968; Haynes 1978b, 1981; Mikulich and Ivanov 

 1983). 



Antennae 



Segmentation of the tip of the antennal scale (Fig. 

 IC, sc, ss) is an important characteristic for distin- 

 guishing crangonid larvae from pandalid and hippo- 

 lytid larvae. In crangolid larvae, the scale tip is 

 unsegmented in all stages. In pandalid and hippolytid 

 larvae, the scale tip is unsegmented in only four 

 species: PayidalopRis coccinata, Pandalus kessleri, P. 

 prensor, and possibly Heptacarptis ( = Spirontocaris) 

 tridens (Needier 1934; Kurata 1955, 1964a, b; 

 Mikulich and Ivanov 1983). The absence of segmen- 

 tation of the scale tip of Pandalopsis coccinata, Pan- 

 dalus kessleri, and P. prensor is related to the ex- 

 tremely precocious development of these species. 

 Hepta<:arpus tridens, however, has unabbreviated 

 development (Needier 1934) and, presumably, a 

 segmented tip. Needier (1934) may not have ob- 

 served segmentation of the scale in H. tridens 

 because she based her description on unstained lar- 

 vae (staining emphasizes segmentation (Haynes 

 1976)). 



Mandibles 



Mandibles (Fig. ID) are described for most pan- 

 dalid larvae, but descriptions of mandibles for hippo- 

 lytid and crangonid larvae in the northern North 

 Pacific Ocean are usually limited to Stage I. I have 

 supplemented these limited descriptions with infor- 

 mation on larvae from other areas, particularly the 

 North Sea. Descriptions of late stage larvae from the 



northern North Pacific Ocean are needed, however, 

 to verify development of mandibles in hippolytid and 

 crangonid larvae. 



Zoeae of Pandalidae, Hippolytidae, and Crangoni- 

 dae have similar mandibles in all stages, and both 

 molar and incisor processes are present. In Stage I, 

 the incisor processes of the left and right mandibles 

 are typically biserrate or triserrate. The number of 

 teeth increases in later stages. In some species, the 

 left mandible also has a subterminal tooth and a 

 lacinia mobilis (movable spine adjacent to incisor pro- 

 cess; Fig. IE). The subterminal tooth and lacinia 

 mobilis are usually, if not always, absent on the right 

 mandible. In the Crangonidae, the incisor process 

 eventually becomes a molar process, usually at the 

 megalopa. 



The most distinctive character of the mandible is 

 the absence of a palp in the zoeal stages. This palp 

 first appears in the megalopa or first juvenile stage 

 of Pandalidae and in the megalopa or later stages of 

 the Hippolytidae. In one exception, Pandalopsis coc- 

 cinata, the palp is present and segmented as early as 

 Stage I (Kurata 1964a). The palp is absent in all 

 stages of Crangonidae, including the adults. 



The mandibular palp of the Hippolytidae may 

 develop somewhat later than the mandibular palp of 

 the Pandalidae. For instance, in some species of 

 Hippolytidae, the palp may not appear until as late as 

 the third or fourth juvenile stage (Lebour 1936), and 

 in some genera, such as Hippolyte, the absence of the 

 palp in the adult may mean the palp is absent in the 

 larvae also. The palp eventually becomes three 

 segmented in the Pandalidae and two segmented in 

 the Hippolytidae. 



Maxillules 



Lebour (1930) stated that Pandalus larvae have no 

 subterminal seta (Fig. IF, st) on the basipodite of the 

 maxillule (F^ig. IF, Mx,, b). Yet, the seta is present in 

 some or all larval stages of Pandalus kessleri, P. 

 tridens, P. stenolepis, P. borealis, P. goniurus, P. jor- 

 dani, P. hypsinotus, and Pandalopsis coccinata. The 

 seta is also present in the early stages of Pandalus 

 montagui, P. projnnquus, Pandalina brevirostris, 

 and Dichelopandahis bonnieri that were collected 

 from waters off Great Britain (Needier 1938; Kurata 

 1955, 1964a; Pike and Williamson 1964; Modin and 

 Cox 1967; Lee 1969; Haynes 1976, 1978a, 1979, 

 1980a). The subterminal seta is absent in hippolytid 

 and crangonid larvae described from the North 

 Pacific Ocean but is present in larvae of Hippolyte in- 

 ermis and H. varians from waters off Great Britain 

 (Lebour 1931). According to Gurney (1942) and Pike 



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