KNIGHT: DEVELOPMENT OF EUPHAUSIA GIBBOIDES 



Leg 4 (Figure ION) rudimentary, with bud of 

 exopod and small bilobed or simple bud of gill; 

 endopod usually without terminal setae, 0(22) or 

 1(2) seta were observed. Leg 5 present as bud. 

 Leg 7 rudimentary with gill bud and developing 

 photophore. 



Setation of pleopods on abdominal segments 1-4 

 as follows: pleopod 1 (Figure UN) — endopod 2, 

 exopod 6(8), 7(11), or 8(1); pleopods 2-4 — endopod 

 1, exopod 6. Non-setose pleopod of segment 5 as in 

 furcilia L Endopod of pleopod 1 with appendix 

 interna, a small medial lobe with tiny hooks. 



Telson (Figure 12C) narrower; posterolateral 

 spine 3 quite broad, inner margin smooth except 

 for 1 or 2 tiny distal spinules near larger dorsal 

 spinule. Five terminal spines of furcilia IV may 

 often be seen beneath integument. 



Furcilia IV (Figures 3D, 4D) 



Rostrum of carapace usually with smooth 

 margin, there may be tiny remnants of marginal 

 spines but no median spine. Abdomen with 5 

 pairs of setose pleopods; photophores on segments 

 1, 2, and 4 pigmented and functional; developing 

 photophore on segment 3 sometimes with faint 

 pigment. 



Antennular flagella (Figure 6J) with about 6 or 

 7 segments, segmentation usually indistinct; 

 outer flagellum with 3 aesthetascs, 1 proximal 

 to pair on medial margin, 1 aesthetasc no longer 

 bifurcate. 



Maxillule with 8(12) or 9(10) setae on coxal 

 endite (Figure 8F); basal endite with 8(1) or 

 9(21) marginal spines and 1 seta on proximal 

 margin. 



Maxilla usually unchanged, with setation of 

 8-4-6-5-3; lobe 4 variable with 5(20) or 6(2) 

 setae. 



Maxilliped (Figure 9E) with 5(4) or 6(18) setae 

 on coxa; basis with 6(9) or 7(10) setae. Endopod 

 becoming 3-segmented as small terminal segment 

 forms wdth setation of 3-2-4 for segments 1-3. 



Leg 2 (Figure lOD) with endopod larger, more 

 setose, and becoming geniculate with terminal 

 3 segments reflexed as in adult; exopod with 4(3) 

 or 5(6) setae (seldom intact); gill bilobed. Leg 3 

 (Figure lOJ) with endopod 5-segmented, some- 

 times slightly reflexed, articulation with basis 

 indistinct, setation variable, terminal segment 

 with more than 2 setae; exopod with 2(1), 3(1), 

 or 4(12) setae; gill bilobed. Leg 4 (Figure lOO) 

 endopod with few (less than 5) weakly delineated 



segments, terminal segment with 2 setae, other 

 setation variable; exopod usually without setae, 

 1 of 15 appendages examined with 1 seta; gill 

 bilobed. Leg 5 (Figure llA) rudimentary with bud 

 of exopod and bilobed or simple bud of gill. Bud 

 of leg 6 present. Leg 7 (Figure 111) with gill 

 bilobed or with small bud of 3rd lobe, photophore 

 may have pigment. Leg 8 (Figure 1 IF) represented 

 by bilobed or trilobed gill. 



Pleopod setation as follows: pleopod 1 (Figure 

 110) — endopod 3(2) or 4(17), exopod 8; pleopod 2 

 — endopod 2, exopod 7(1) or 8(19); pleopod 3 — 

 endopod 2, exopod 7(3) or 8(15); pleopod 4 — 

 endopod 2, exopod 7(8) or 8(9); pleopod 5 — endo- 

 pod 1, exopod 6. 



Telson (Figure 12D) with 5 terminal spines, 

 the 3 terminal spines of next instar often visible 

 beneath cuticle. 



VARIANT FORMS. — A small furcilia IV with 

 6 telson spines was less mature in that leg 4 had 

 1 terminal seta and exopods of pleopods 3 and 4 

 had only 6 setae. A furcilia IV with 4 telson spines 

 showed bud of 3rd lobe of gill on leg 2. 



Furcilia V (Figures 3E, 5A) 



Rostrum usually wdth smooth margin, there 

 may be a very small median spine. Photophores 

 on abdominal segments 1-4 now pigmented. 



Antennule with lateral spine of peduncle seg- 

 ment 1 extending to about midpoint of segment 

 3, none of the specimens available had flagella 

 intact. 



Antenna (Figure 7E) transformed, no longer 

 natatory; basal segment with distolateral spine; 

 endopod with 8 segments, 3 peduncular and 5 

 flagellar, division of terminal segment not always 

 distinct; exopod (scale) with 13 or 14 plumose 

 marginal setae. 



Mandible (Figure 7J) with anterolateral pro- 

 cess now considerably reduced in size. 



Maxillule with 8(1) or 9(22) setae on coxal 

 endite; basal endite with 9(21) or 10(2) marginal 

 spines and 1(21) or 2(2) small setae on proximal 

 margin. Endopod with segmentation weak or 

 indistinct; in 6 of 21 appendages examined 1- 

 segmented v^dth 1 seta on lateral margin as figured 

 for furcilia VI (Figure 8G). 



Maxilla usually with setation of 8-4/5-6-6-3; 

 lobe 2 (Figure 8L) variable with 4(15) or 5(9) 

 setae and lobe 4 with 4(1), 5(4), or 6(19) setae. 



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