FISHERY BULLETIN: VOL. 80, NO. 2 



species off the coast of southern California were 

 obtained for study from preserved plankton 

 samples taken on Scripps Institution of Ocean- 

 ography Expedition X and CalCOFI Cruises 

 6904 and 6905 during April and May of 1964 and 

 1965. 



At least five individuals of each developmental 

 stage were dissected in glycerine for study of 

 appendages. Some specimens of each stage were 

 prepared for study and dissection by digesting 

 away all soft tissue in heated aqueous KOH and 

 then staining with Chlorazol Black E. Drawings 

 were prepared with the drawing attachment of a 

 Wild M20 3 microscope. 



Measurements of reared and planktonic 

 larvae of S. similis were compared by Omori 

 (1979, table 6); the mean body lengths (with 

 standard deviation in parentheses) of larval 

 stages obtained at 14°C are repeated here by 

 stage for convenience. The larvae were mea- 

 sured along the midline from anterior margin of 

 forehead to posterior margin of telson. 



The postnaupliar developmental phases have 

 been named protozoea, zoea, and postlarva 

 following Omori (1979), and the terminology of 

 Gurney and Lebour (1940) has been followed in 

 describing the armature of carapace. In the 

 protozoeal phase the outgrowths of the carapace 

 are referred to as processes with secondary spines 

 and spinules, while in the zoeal and postlarval 

 stages the outgrowths are called spines with 

 secondary spinules. 



Segmentation of two of the appendages proved 

 difficult to determine. The basal segmentation of 

 the exopod of the second antenna in protozoeal 

 stages I-III was not clear. In S. similis it 

 appeared that there were incomplete sutures 

 within segments 1 and 3, giving 12 outer margin 

 and 10 inner margin sutures; we have numbered 

 the segments along the inner margin. The articu- 

 lation of coxa, basis, and endopod of the second 

 maxilla in protozoeal and zoeal phases also 

 proved confusing. We have followed Gurney 

 (1942) in referring to the medial lobes as bifid 

 endites of coxa and basis, and have assumed from 

 the morphology of the postlarval appendage that 

 the endopod consists of 5 segments, although the 

 articulation of segment 1 and basis was not clear. 



In the description of larval stages, only 

 changes in structure and armature of body and 

 appendages are discussed; if an appendage is not 



3 Reference to trade names does not imply endorsement by 

 the National Marine Fisheries Service, NOAA. 



mentioned, it may be assumed that there has 

 been no change from the preceding stage except 

 increase in size. 



In order to compare the basic pattern of 

 development between Sergestes similis and 

 Sergia lucens, we reexamined a number of larvae 

 and postlarvae of S. lucens from the rearing 

 experiment in July 1965. 



RESULTS 



The larval development of Sergestes similis 

 includes the following stages: nauplius I-IV, 

 protozoea I-III, and zoea I-II. The first two 

 postlarval stages are also described. 



Nauplius I (Fig. la, e) 



Body length: 0.34 mm (0.01). 



Body ovoid with two posterior spines which 

 curve posterodorsally and are slightly swollen 

 basally. 



Antennule (Fig. 2a) unsegmented with 4 

 smooth setae, 2 terminal and 2 subterminal, and 

 small terminal spine. 



Antenna (Fig. 3a) unsegmented; exopod with 5 

 setae; endopod with 3 setae, 2 terminal and 1 sub- 

 terminal; all setae smooth. 



Mandible (Fig. 4a) biramous and unseg- 

 mented, each ramus with 3 smooth setae. 



Nauplius II (Fig. lb) 



Body length: 0.38 mm (0.01). 



Body slightly longer and narrower posteriorly 

 than in stage I, with 2 pairs of spines on posterior 

 margin, outer pair very short, tiny rudiments of 

 third inner pair sometimes visible. 



Antennule (Fig. 2b) with 1 subterminal medio- 

 ventral seta and 3 terminal processes including 2 

 setae with setules and 1 small aesthetasc. 



Antenna (Fig. 3b) unsegmented; exopod with 6 

 setae and sometimes with small distal spine, 

 distolateral seta smooth and others plumose; 

 endopod with 2 plumose setae and 1 small spine 

 terminally. 



Mandible (Fig. 4b) with 3 plumose setae on 

 each ramus. 



Nauplius III (Fig. lc, f) 



Body length: 0.42 mm (0.02). 

 Body with posterior portion tapering, pos- 

 terior margin slightly indented medially with 4 



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