FISHERY BULLETIN: VOL. 71. NO. 3 



lucida. The left appendage is shown in the 

 figures. When setae were plumose, the fact 

 is noted in the text but is not always shown 

 in the drawings; this omission made it possible 

 to show other details. At least 10 specimens 

 each of prezoeae and stage I zoeae of C. bairdi 

 and C. opilio were dissected and studied in 

 detail with respect to appendage setation and 

 other characteristics. 



An ocular micrometer was used to measure 

 the following body dimensions of the larvae: 

 Carapace length — straight-line distance from 

 posterior margin of orbit to middorsal posterior 

 margin of carapace; dorsal-rostral length — 

 straight-line distance from tip of dorsal spine 

 to tip of rostral spine; width between tips of 

 lateral spines of carapace — horizontal straight- 

 line distance between tips of spines; total body 

 length— distance from tip of rostrum to poste- 

 rior margin of telson, not including telson 

 spines (except in prezoeae, in which it is 

 distance from folded rostrum to posterior mar- 

 gin of telson). Total body length is difficult to 

 measure accurately in preserved larvae be- 

 cause the abdomen is generally flexed beneath 

 the carapace; the measurement therefore 

 requires the summation of several straight- 

 line measurements or chords of the arch formed 

 by the dorsal margin of the body. 



Nomenclature of the larval appendages fol- 

 lows that of Gurney (1942). The setation formula 

 of the endopodite is the number of setae per 

 segment from the distal to the proximal 

 segment. 



DESCRIPTION OF LARVAL STAGES 



Chioiioecetes buirdi 

 Prezoeae (Figure la) 



Cuticle of antennules, antennae, and telson 

 delicately plumed. Antennule (Figure lb) has 

 two projections, one appreciably shorter than 

 the other; shorter projection nonpulmose. Exop- 

 odite of antenna (Figure Ic) has four plumose 

 projections; endopodite has a simple nonplumose 

 projection, no projection arising from area of 

 rudimentary flagellum. Endopodites and exop- 

 odites of first maxilliped (Figure Id) and 



second maxilliped (Figure le) consist of simple 

 sheaths. .Telson (Figure If) has seven pro- 

 jections on each side; following Lebour (1928), 

 these are numbered from the inside 1 to 7; 

 fourth projection short and nonplumose and 

 covers spine that in zoea forms tip of telson 

 fork; seventh projection also nonplumose but 

 may occasionally have a few hairs. 



The average carapace length (50 specimens) 

 is 0.39 mm (range 0.32 to 0.46 mm) and the 

 average total body length is 2.48 mm (range 

 2.22 to 2.80 mm). 



Stage I Zoeae 



General shape (Figure 2a, b) characteristic 

 of larvae of subfamily Oregoniinae. All spines 

 well developed and armed with fine spinules 

 on at least the distal half of their length. Dorsal 

 and rostral spines long, tapering, and usually 

 slightly "s" shaped; dorsal spine slightly longer 

 than rostral. Lateral spines large; at right 

 angles to carapace and curved downward 

 slightly. Eyestalks short, not articulated, and 

 each bears a minute protuberance about mid- 

 way between eye and carapace. Carapace has 

 slight medial crest with noticeable hump on 

 front of head. Distinct protuberance on cara- 

 pace posterior to dorsal spine. A minute hair 

 on each side of carapace between lateral spine 

 and base of dorsal spine. Total of six setae 

 along posterior edge of carapace all arising 

 from inner side of carapace; posterior three 

 setae longer and stouter than anterior three 

 setae. Lateral margin of carapace strongly 

 indented just posterior to eye. 



The averages for the following measurements 

 (50 specimens) are: carapace length 0.54 mm 

 (range 0.45 to 0.73 mm); dorsal-rostral length 

 4.17 mm (range 3.96 to 4.55 mm); width 

 between tips of lateral spines 2.73 mm (range 

 2.52 to 2.97 mm); and total body length 5.15 

 mm (range 4.96 to 5.60 mm). 



ANTENNULE (FIGURE 2c).— Antennule 

 conical and uniramous, with five terminal 

 processes — three long aesthetes and two shorter 

 setae; two aesthetes about equal in length, 

 but third only slightly longer than longest 

 setae. 



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