KNICHT and OMORL LARVAL DKVKLOI'MKNT OF SERGESTES SIMILIS 



Mandible unchanged. 



Anlagen of maxillules, maxillae, and first and 

 second maxillipeds visible. 



Nauplius IV (Fig. Id, g) 



Body length: 0.49 mm (0.03). 



Body with abdomen forming, posterior 

 margin with distinct medial indentation and 4 

 pairs spines, third pair still relatively long, rudi- 

 ments of fifth inner pair sometimes visible, 

 spinules present on spines 2-4, and sometimes on 

 1; third pair articulated, other spines fused with 

 telson. 



Antennule (Fig. 2d) with 2 inner setae, 

 terminal setation unchanged; proximal two- 

 thirds with indistinct segmentation most clearly 

 visible along inner margin; about 17 rows of tiny 

 spinules encircle antennule associated, in 

 segmented section, with distal margin of seg- 

 ment. 



Antenna (Fig. 3d) with protopod of 2 indistinct 

 segments; exopod with approximately 8 seg- 

 ments (basal segmentation unclear, specimens 

 cleared and stained have indication of 10 seg- 

 ments on outer margin and about 8 on inner 

 margin), with 8 or 9 setae and sometimes a small 

 distal spine, distal 3 setae with small setules, 

 others plumose; endopod at least 2-segmented, 

 small distinct distal segment with 4 terminal 

 setae, proximal segment with 2 setae on outer 

 margin and sometimes with incomplete basal 

 segmentation; both rami encircled with rows of 

 tiny spinules. 



Mandible (Fig. 4c) with basal portion swelling 

 with development of gnathal lobe, tissue with- 

 drawing from rami. 



Rudiments of maxillules, maxillae, and 2 pairs 

 of maxillipeds present posterior to mandibles. 



Protozoea I (Fig. 5a, b) 



Body length: 0.82 mm (0.02). 



Carapace with following processes: 1 pair 

 anterolateral, each branching to 3 large spines 

 and occasionally 1-3 small spines (5 of 20 reared 

 larvae with small spines on one or both processes, 

 20 larvae from the plankton with 3 large spines 

 only); 1 pair lateral with 1-3 large basal spinules; 

 1 posterodorsal with few large basal spinules, 

 usually 2; all processes with small spinules to tip. 

 Anterior margin of forehead with pair of small 

 papillae. Prominent, round dorsal organ present 

 in protozoeal phase. Thorax with evidence of 



segmentation, abdomen unsegmented. Telson 

 forked, each fork with 2 small smooth ventral 

 spines and 4 long curving processes armed with 

 spinules. 



Antennule (Fig. 2e) of 3 segments, proximal 

 segment subdivided into 5 small segments; 

 proximal and middle segments with 1 and 2 

 setae, distal segment with 8 processes including 

 5 setae, 3 terminal and 2 proximal, and 3 

 aesthetascs. Gurney (1942) noted that distal seg- 

 ment with aesthetascs is homologous with outer 

 flagellum of later stages and that peduncle is 

 therefore of 2 segments. 



Antenna (Fig. 3e) with exopod of 10 segments, 

 terminal segment with 3 setae, segments 2-9 

 with 1 distal seta on inner margin, segments 3 

 and 5 with 1 distal seta on outer margin as well; 

 endopod 2-segmented, distal segment with 5 

 terminal setae, long proximal segment with 5 

 setae on inner margin— 3 distal and 2 proximal 

 on slight protuberance; basis with 2 setae on 

 inner margin; structure unchanged in proto- 

 zoeal phase. 



Mandibles (Fig. 4d) without palp, gnathal lobe 

 of each mandible with 1 strong serrated spine on 

 cutting edge between incisor teeth and molar 

 area. Labrum (Fig. 4j) with long anteroventral 

 spine in protozoeal phase. 



Maxillule (Fig. 6a) with exopod a small round 

 lobe bearing 4 plumose setae; endopod 3- 

 segmented with 3-2-5 setae progressing distally; 

 basal and coxal endites with 4 and 5 setae, re- 

 spectively. 



Maxilla (Fig. 7a) with segmentation indistinct; 

 exopod small and oblong with 5 long plumose 

 setae; endopod 5-segmented with setation of 4-2- 

 2-2-3, segment 1 rarely with 3 setae; basal and 

 coxal endites bifid, the 4 median lobes with 8-4-4- 

 4 setae. 



First maxilliped (Fig. 8a) with exopod of 1 seg- 

 ment bearing 7 long plumose marginal setae; 

 endopod 4-segmented with 3-2-2-5 setae; basis 

 with 12 setae in groups of 3 along medial margin; 

 coxa with 5 setae; inner margins with fine setules 

 as well. 



Second maxilliped (Fig. 9a) with exopod of 1 

 segment bearing 6 marginal plumose setae; 

 endopod 4-segmented with 2-1-2-5 setae; basis 

 with 5 and coxa with 2 setae. 



Third maxilliped a small bud. 



Protozoea II (Fig. 10a, b) 



Body length: 1.21 mm (0.10). 



223 



