MORGAN and PROVENZANO; DEVELOPMENT OF SQUILLA EMPUSA LARVAE AND POSTLARVA 



while the postlarval appendages were illustrated 

 with the aid of a Bausch and Lomb microprojector. 



The descriptions of all larval stages were based 

 on five specimens; four specimens were used to 

 describe the postlarva. Carapace length (CL) indi- 

 cates the distance from the tip of the rostrum to the 

 median posterior margin of the carapace, exclu- 

 sive of the median spine; telson length itL), dis- 

 tance from the articulation with the sixth abdom- 

 inal somite to the median posterior margin of the 

 telson. The term pleotelson (Kaestner 1970) is 

 used to refer to the telson before the sixth abdomi- 

 nal somite has become completely articulated. 

 Pleotelson length (PL) indicates the distance from 

 the articulation with the fifth abdominal somite to 

 the median posterior margin of the pleotelson; tel- 

 son width iTW) and pleotelson width (PW), dis- 

 tance across the widest portion; rostral length 

 (RL) of the larva, distance from the tip of the ros- 

 trum to the base of the anterolateral spines of the 

 carapace; rostral length of the postlarva, distance 

 from the tip of the rostrum to the posterior margin 

 of the rostrum; rostral width (RW) of the post- 

 larva, distance from the tip of the rostrum to the 

 median posterior margin of the telson; and total 

 length (TL) of the postlarva, distance from the 

 anterior margin of the rostrum to the median 

 posterior margin of the telson. 



Maxillules, maxillae, pleopods. distal spinules 

 of the rostrum, and most epipods were omitted 

 from illustrations of the whole animal for the sake 

 of clarity. 



RESULTS 



The pelagic larval development of S. empusa 

 was found to include nine stages before the post- 

 larval stage. Juvenile stages reared for several 

 months after metamorphosis attained sizes of ap- 

 proximately 30 to 40 mm TL and could be posi- 

 tively identified with the adult. Although none of 

 the 576 larvae reared at the 16 different tempera- 

 ture and salinity combinations was reared 

 through the entire pelagic development to 

 metamorphosis, larvae survived well and molted 

 frequently at two of the test combinations. Of lar- 

 vae kept at 20'C, 25%o salinity, or at 25°C, 25%o 

 salinity, 47'* molted three or more times, 24% 

 underwent at least five ecdyses, and 'y^r molted 

 seven times over a 6-wk period. Thirty-four ani- 

 mals molted to postlarva. Great increases in size 

 from the first to the last stage necessitated ad- 

 justments in food size and quantity. Detailed re- 



sults of effects of various experimental conditions 

 are being prepared by Morgan for publication 

 elsewhere. 



The difficulty in rearing the larvae through the 

 lengthy pelagic development made it necessary to 

 reconstruct the developmental sequence by ob- 

 serving the larvae molt through successive stages. 



Stage I (Figure I A) 



Measurements (mm): RL, 0.70 to 1.10; PL, 0.4 

 to 0.8; TL. 2.9 to 3.3; CL, 0.80 to 1.30; PW, 0.3 to 

 0.6. 



Rostrum deflexed, extending slightly beyond 

 antennular flagella, ventral spinules absent. 



Carapace with one pair of supraorbital spines. 

 Lateral margins of carapace convex, armed ven- 

 trally with four spinules. Posterior margin of 

 carapace deeply notched, armed with a median 

 dorsal spine. Posterolateral spines, armed with 

 one ventral spinule, extending to fourth abdomi- 

 nal somite. 



Ocular somite articulated, armed with one spine 

 on median ventral margin. Antennular somite not 

 articulated. 



Antennule (Figure 2Al with long two- 

 segmented inner flagellum, apical segment armed 

 with one strong and one weak seta distally and a 

 pair of weak setae medially, proximal segment 

 armed with one strong and two weak setae dis- 

 tally. Outer flagellum armed with one large and 

 one small seta distally, followed by one weak seta 

 and six aesthetascs arranged 1-2-3 along inner 

 margin. Median flagellum absent. 



Antenna (Figure 3A) armed with nine plumose 

 setae, endopod absent. 



Mandible (Figure 4A) serrate, mandibular palp 

 absent. 



Maxillule ( Figure 5A ) with coxal endite bearing 

 three spinules and one seta, basal endite with one 

 strong tooth flanked by two strong setae, palp with 

 one long seta, endopod absent. 



Maxilla (Figure 6A) unsegmented. armed with 

 six setae. 



First maxilliped (Figure 7A) with dactylus 

 small, pointed. Propodus with two extremely mi- 

 nute spinules, inner margin bearing seven strong 

 setae arranged 2-3-2. Carpus with one strong seta 

 distally. merus without setae, epipod absent. 



Second maxilliped (Figure 8A) large, basis with 

 stout proximal spine. Propodus with 1 strong ter- 

 minal tooth followed by 17 to 20 denticles on inner 

 margin. Dactylus armed with spinules, distal 



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