FISHERY BULLETIN: VOL. 76, NO. 4 



Mandibles: (Figure 6C). Molar and incisor pro- 

 cesses acutely spinous, otherwise unchanged from 

 earlier stages; no palp. 



Maxilliile: (Figure 6D). Endopodite un- 

 changed, but may have small seta at base of seg- 

 ment. Basal endite with 7 stout spines, 3 setae; 

 coxal endite with 5 or 6 long spines, 3 strong setae, 

 and occasional small tooth. 



Maxilla: (Figure 6E). Endopodite unchanged. 

 Basal endite distal lobe with 6 spines, 2 setae, 

 proximal lobe with 7 or 8 spines and strong setae 

 intermixed; coxal endite distal lobe with 4 termi- 

 nal spines, 1 lateral seta, proximal lobe with 11 

 spines, placed 5 terminally, 4 subterminally, 2 

 laterally. Scaphognathite with 17-20 marginal 

 setae, including 2 or 3 anteriorly near base, plus 

 usual long apical plumose seta, as shown. 



Maxilliped 1: (Figure 6F). Basipodite adds a 

 single small seta proximally, ventral formula now 

 3, 3, 3, 3. Endopodal and coxal setae unchanged; 8 

 exopodal natatory setae. 



Maxilliped 2: (Figure 6G). Coxal and basipodal 

 setae unchanged. Endopodite setal formula 2,2 + 

 I, 2 + I, 5 + I. Exopodal natatory setae 8. 



Maxilliped 3: (Figure 6H). Endopodite over- 

 reaches basipodite, bearing 3 setae. Exopodite 

 with 8 natatory setae. 



Pereiopods: (Figure 2D). Chelation and segmen- 

 tation more or less apparent, progressing rapidly 

 throughout stage; entire pereiopodal mass hangs 

 from beneath posterolateral carapace region in 

 later stage. 



Abdomen: (Figure 2D, d). Lateral spine present 

 only on somite 5; dorsal spinulation on posterior 

 margins of somites nearly absent; paired dorsal 

 setae remain. A short, sharp spine on pos- 

 terolateral margin of somite 6, just above inser- 

 tion of uropodal basipodite. Pleopod primordia 

 may be present in some specimens, but develop- 

 ment is weak and occurs slowly, if at all, through- 

 out stage. 



Telson: (Figure 61, i). Uropods completely de- 

 veloped, exopodite distal outer tip produced into 

 long spine, 8-11 long marginal setae present; en- 

 dopodites with 4 or 5 setae; with shorter setae on 



796 



both rami. Telson marginal setal formula 8 + 8, 

 fused fourth process now heavily spinulose, other 

 movable processes (except process 2, which, as in 

 other anomurans, remains a simple seta) carry 

 distinctive, sharp, separated, spinules along their 

 length (Figure 6i; 40 x objective), these spinules 

 much more hooklike distally, more spinous prox- 

 imally. Other dorsal and ventral setae on telson as 

 illustrated. 



Color: Similar to stage III; quite developed and 

 noticeable along anterior and internal margin of 

 eyestalks; interiorly on midgut, and bases of 

 maxillipeds; single red chromatophores now bas- 

 ally on antennular protopodite, on posterior mar- 

 gin of maxillipedal basipodites, and laterally on 

 abdominal somites 3-5; eyes blue, reflecting green 

 highlights. 



Remarks: This stage, with limited aesthetasc 

 numbers, reduced antennular endopodite and un- 

 segmented protopodite, lacking mandibular palps, 

 and with developing pereiopods and usually only 

 pleopodal primordia, always molted to zoeal stage 

 V. 



Fourth Zoea (Advanced) 



Carapace length: 1.6 mm. 



Number of specimens examined: 12. 



Carapace: Differs little from regular stage IV 

 except being larger, more inflated; armature simi- 

 lar to regular stage zoea. 



Antennule: (Figure 6a). Endopodite about 

 0.75 X to nearly equal to length of exopodite; latter 

 with four rows of aesthetascs laterally, as 1, 3, 3, 2, 

 plus usual 3, plus 3 setae terminally. Other setae 

 as illustrated. 



Antenna: (Figure 6b). Endopodite distinctly 

 overreaches (1.2x) scaphocerite; latter with 12-14 

 marginal setae; larger ventral propodal spine 

 about 0.25 X endopodite length, remaining half 

 again as long as smaller propodal spine. 



Mandibles: (Figure 6C). Large, heavily 

 toothed processes, distinguished now by undivided 

 simple palp. 



Maxillule: May add one more process on basal 

 endite; tooth on coxal endite usually distinct. 



