POWELL and GORDY: EGG AND LARVAL DEVELOPMENT OF THE SPOT 

 Pter>'giophore Development and Arrangements 



Fully developed spot had three predorsal bones 

 which did not support spines (Figure 7): One such 

 bone was located between the skull and first 

 neural spine, one between the first and second 

 neural spines, and one between the second and 

 third neural spines. They began to develop at 5.7 

 mm SL, anteroposteriorly, and the full comple- 

 ment was recognizable at 8.2 mm SL (Figure 8). 



There were two fewer pterygiophores than dor- 

 sal fin elements (spines and soft rays) on fully 

 developed spot. The anteriormost pterygiophore 

 was associated with three spines (Figure 7). It was 

 secondarily associated with the first two spines 

 and serially associated with the third spine. All 

 other pterygiophores were serially associated with 

 one dorsal fin element and secondarily associated 

 with a preceding element. 



Dorsal fin pterygiophores were first apparent at 

 5.1 mm SL between neural spines 9 through 14 and 

 development proceeded anteriorly and posteriorly 

 simultaneously (Figure 8). The adult complement 

 was achieved at 8.2 mm SL. 



Although there was a variable number of dorsal 

 pterygiophores between neural spines (Table 3), a 

 nearly consistent pattern was observed (Figure 7). 

 The formula^ 



P/P/P+1/2/ 1/2/ 1/2/2/ 



12 3 4 5 6 7 6 9 10 1112 1314 1516 17 1819202122232425 



— r — I r — I — 1 T 1 — 1 1 — r- 



I I r r" 



I I I r 



rrrrrrrrr. 



^ ^ T ^ VVrVrVrrVrVVVV--^ 



nrvnTrTTTTTT 



5.1 mm SL 



, .rrrrr^rc 



'mms<;^,-^^,m^ 



.^, 



rr/:r/:rrr/;r/^r/-r/^rmr 



5.5 mm SL 



T W' V \ \ \ \ \ \ \ \ \\ '■! ' " \ ' " ' V ' V 



\^:^:i;i^\. 



5.7 mm SL 





VN^JL^NiNiNiNi* 



6.7 mm SL 



' ' ' ' 'v 'v 'v -V\ \\ \ \\ \ \ \ \ \\ \ \\ \\ \\ \ \ ' ■" 



OXnTTTTT 



8.0 mm SL 



^ N.N.V\^.NwN^^wV\. >8.2 mm SL 



FIGURE 8. — Schematic representation of the development of 

 predorsal bones (unshaded), and dorsal and anal fin 

 pterygiophores ( darkened) in Leiostomus xanthurus. 



*Each P represents a predorsal bone, each slant a neural spine 

 and the numerals indicate the number of pterygiophores be- 

 tween neural spines. 



Pdl 



Nsl 



FIGURE 7. — Arrangement of predorsal bones, and the first 11 

 dorsal fin pterygiophores in relation to neural spines for Leio- 

 stomus xanthurus (19.6 mm SL). Spine Sll is the first spine of the 

 second dorsal fin. Ps3, represents the pterygiophore in serial 

 association with the third dorsal spine; Pr2, the pterygiophore in 

 serial association with the second ray of the second dorsal fin; SI, 

 the first spine on the first dorsal fin: Rl, the first ray on the second 

 dorsal fin; Nsl, the neural spine on the first centrum; and Pd, the 

 predorsal bones. 



Table 3. — Frequencies of dorsal fin pterygiophores between 

 neural spines in 23 Leiostomus xanthurus (8.2-48.0 mm SL). 



occurred in 87% of our 23 specimens. We also ob- 

 served that in 96% of those specimens the an- 

 teriormost pterygiophore between neural spines 7 

 and 8 was serially associated with the last spine of 

 the first dorsal fin (Figure 7). 



Fully developed spot had two fewer pterygio- 

 phores than anal fin elements. Like the dorsal fin, 

 the anteriormost anal fin pterygiophore was as- 



709 



