JO-U|l|l|l|l|l|IJI| 



lii.l^i^i.i.i.l I. Li. 1,1,1,1,1, 1. 1,1, 1, 1, 1, 1,1,1 



Figure 36. — Stations at which larvae and pelade juveniles of Pon- 

 tirms Type A were collected on CalCOFI cruises (triangles) during 

 1956 and 1957, EASTROPAC expeditions (closed circles) during 1967 

 and 1968, and Scripps Tuna Oceanography cruises (open circles) dur- 

 ing 1958 and 1959. Open square represents a station from the Scripps 

 Institution of Oceanography fish collection and closed square a sta- 

 tion from the University of California, Los Angeles, flsh collection. 



EASTROPAC plankton tows. The mean number of 

 specimens for all plankton tows was 3.4 ± 6.36 SD with a 

 range of 1 to 34; 50% of all plankton tows had only a 

 single specimen. 



In the tropical waters surveyed during the EAS- 

 TROPAC expedition, the number of occurrences was 

 about equal on the winter cruises (February to April) and 

 the summer cruises (July to September). 



Pontinus Type B, Figure 37 



Literature. — None. 



Distinguishing features. — The smallest larva 

 available is a 5.0-mm specimen undergoing notochord 

 flexion. Dorsal pigment saddles are already beginning to 

 form at this size, and well-formed saddles are present in 

 specimens as small as 10 mm. In Pontinus Type A the 

 pigment saddles begin to form at about 15 mm, a size 

 chosen for convenience as the beginning of the pelagic 

 juvenile stage. Since pigment saddles begin to form in 

 midstage larvae of Pontinus Type B it is more ap- 

 propriate to consider the appearance of scales at about 10 

 mm as the event marking the beginning of the pelagic 

 juvenile stage. The largest pelagic juvenile in our collec- 

 tion is 23.1 mm. The size at transformation into benthic 

 juveniles is not known since the smallest benthic juvenile 

 of Pontinus Type B in our collection is 29.0 mm. 



The smallest larva in our collection, 5.0 mm long, has 

 almost completed notochord flexion indicating that 



notochord flexion is probably initiated in 4-mm larvae. 

 At 6.0 mm, notochord flexion is completed. Notochord 

 flexion occurs at a smaller size in larvae o{ Pontinus Type 

 A and is completed when the larvae reach about 5.0-mm 

 length. 



Larvae of Pontinus Type B are deeper-bodied than 

 those of Pontinus Type A. Body depth at the pectoral fin 

 base in Pontinus Type B larvae undergoing notochord 

 flexion is 45 to 46'^"c of the body length (Table 37). In post- 

 flexion larvae the mean is 43%, and in pelagic juveniles it 

 is 41% . The more slender-bodied larvae oi Pontinus Type 

 A show an opposite trend. Body depth increases from a 

 mean of 33% of the body length in larvae undergoing 

 notochord flexion to a mean of 39% for postflexion larvae 

 and pelagic juveniles. 



The compact gut is already masked by trunk mus- 

 culature in the smallest larva in our collection. Snout- 

 anus length is relatively longer in Pontinus Type B than 

 in Pontinus Type A. It averages 64% of the body length in 

 Pontinus Type B larvae undergoing notochord flexion 

 and 67% in postflexion larvae and pelagic juveniles while 

 in comparable stages of Pontinus Type A the means are 

 54% and 62%. 



The head is larger in Pontinus Type B than in Pon- 

 tinus Type A. Head length in the former averages 45% of 

 the body length during notochord flexion and in post- 

 flexion larvae and 42% in pelagic juveniles. Relative head 

 length shows an opposite trend in Pontinus Type A, 

 averaging 32% in larvae undergoing flexion and 40% in 

 postflexion larvae and pelagic juveniles. The eye is 

 relatively larger in Pontinus Type B compared with Pon- 

 tinus Type A; eye diameter averages 32% of head length 

 for larvae and pelagic juveniles of the former and 27% in 

 comparable stages of Pontinus Type A. Snout length is 

 relatively shorter in Pontinus Type B compared with 

 Pontinus Type A. In the former it averages 30% of the 

 head length in larvae undergoing notochord flexion, 28% 

 in postflexion larvae, and 24% in pelagic juveniles. At 

 comparative stages of Pontinus Type A it averages 41%, 

 33%, and 29% of the head length. 



Pectoral fin length averages 33% of the body length in 

 Pontinus Type B larvae undergoing notochord flexion 

 and 27% in postflexion larvae and pelagic juveniles. In 

 comparable stages of Pontinus Type A, fin length 



Measurements (nm) of larvae of Pontinus Type B. (Specimens between dashed lines 

 are undergoing notochord flexion. ) 



•Pelagic Juvenile, 



64 



