KNIGHT: DEVELOPMENT OF EUPHAUSIA GIBBOIDES 



1 setae respectively, one of the endopods of pleo- 

 pod 5 had rudiment of 2nd seta. 



Furcilia VI (Figures 3F, 5B) 



Rostrum usually with small median spine. 



Antennule with lateral spine of peduncle seg- 

 ment 1 about as long as segment 2; outer flagellum 

 may have additional proximal aesthetasc; one 

 apparently intact inner flagellum with 10 

 segments. 



Antennal scale (Figure 7F) with approximately 

 15 or 16 setae; one intact flagellum with 3 

 peduncular and 11 flagellar segments. 



Right mandible (Figure 7K) now without 

 dentate process near incisor teeth; toothed plates 

 relatively smaller; rudimentary palp may begin 

 to increase in size. 



Maxillule (Figure 8G) with 9(15) or 10(9) setae 

 on coxal endite; basal endite with 9(4) or 10(20) 

 marginal spines and 1(8) or 2(16) small setae on 

 proximal margin. Endopod of 1 segment with 1 

 proximal lateral seta; terminal and medial seta- 

 tion unchanged. Coxa now with rudiment of 

 pseudexopod. 



Maxilla (Figure 8M) usually with setation of 

 8-6-6-6-3; lobe 2 variable with 4(2), 5(4), or 6(18) 

 setae. Exopod represented by 1 (22) or 2(2) setae; 

 endopod rounder. 



Maxilliped (Figure 9G) modifying to adult 

 form; coxa with 5-9 setae, long seta on posterior 

 face no longer present; basis with 8(22) or 9(2) 

 setae. Endopod of 5 segments with variable 

 setation; articulation with basis not clear. Exopod 

 still with 4 terminal setae. 



Leg 2 (Figure lOF, G) with endopod more 

 setose, dactyl with a few more "cleaning" comb 

 setae; exopod with 6 setae; gill trilobed. Leg 3 

 (Figure lOL, M) with long terminal setae on 

 dactyl of endopod; exopod with 6 setae; gill with 

 bud of 3rd lobe or trilobed. Leg 4 (Figure lOQ) 

 with endopod reflexed; exopod with 5(1) or 6(14) 

 setae; gill with bud or larger rudiment of 3rd 

 lobe. Leg 5 (Figure llC) with endopod 5- 

 segmented and setation variable, terminal seg- 

 ment with more than 2 setae; exopod with 

 1(2), 2(4), 3(2), or 4(10) setae; gill trilobed. Leg 6 

 (Figure HE) with endopod unsegmented and non- 

 setose; exopod without setae; gill trilobed; exopod 

 and gill may be rudimentary. Legs 7 (Figure 

 IIK) and 8 (Figure IIH) with increasing num- 

 ber of gill lobes. 



Pleopods with setation as follows: pleopod 1 

 (Figure HP) — endopod 4(5), 5(10), or 6(7), 

 exopod 9(7) or 10(12); pleopod 2 — endopod 4(14), 

 5(7), or 6(2), exopod 9(2), 10(13), or 11(3); pleopod 

 3 — endopod 4(17), 5(1), or 6(3), exopod 9(2), 

 10(13), or 11(1); pleopod 4 — endopod 4(21) or 

 6(2), exopod 9(10) or 10(7); pleopod 5 — endopod 

 3(1) or 4(20), exopod 8. 



Telson (Figure 12F) quite slender with 1 termi- 

 nal spine and 3 pairs posterolateral spines; 

 posterolateral spine 2 was missing on one side 

 in 5 of 12 larvae dissected. Developing telson 

 of next instar is without spine 2 on either side. 



VARIANT FORMS. — In furcilia VI with 2 and 

 3 telson spines, basis of maxilliped sometimes 

 with 7 setae and exopod of leg 2 with 6, 7, or 8 

 setae. Once in furcilia with 3 telson spines, lobe 3 

 of maxilla with 7 setae and right mandible with 

 tiny remnant of dentate process. 



Measurements 



The eggs assumed to be those of E. gibboides 

 have a relatively wide perivitelline space. The 

 measurements, in millimeters, of 100 eggs from 

 one sample (6304- 110. 70) are: diameter of capsule, 

 range = 0.61-0.75, x = 0.69, SD = 0.03; peri- 

 vitelline space, range = 0.13-0.19, x = 0.16, 

 SD = 0.01. 



The measurements of developmental stages 

 are given in Tables 5-8. The growth factor (mean 

 length in stage divided by mean length in pre- 

 ceding stage) for dominant forms is as follows: 



There was variation in size of comparable 

 developmental stages between the different areas 

 from which samples were studied. The lengths 

 of calyptopis stages are compared in Table 9. 

 The larvae sampled in April 1963 (Cruise 6304) 

 in the eastern North Pacific became larger, on 

 the average, during the calyptopis phase in the 



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