FISHERY BULLETIN: VOL. 76, NO. 3 



much of the anterior and slightly dorsal surface of 

 each organ. This pigment is also found in the walls 

 between some vesicles, tending to isolate them 

 from one another. Although the vesicles are mi- 

 nute in the larva and very small in the adults, a 

 small positive allometric growth of the vesicles 

 seems to occur. Screening pigment first appears on 

 the vesicles between about 20 and 30 mm ML. In 

 the adult, the screening pigment is most extensive 

 and covers the entire anteromedial surface of the 

 organ. 



Phasmatopsis fisheri (Berry 1909) 

 Vertical Distribution (Figure 34) 



Over 300 specimens of P. fisheri were captured 

 but most were larvae. Metamorphosis occurs at a 

 size of 40 to 50 mm ML. 



During the day, six larvae were captured be- 

 tween 150 and 250 m. Seventeen juvenile and 

 adult specimens were captured between about 625 

 and 800 m; most captures were made between 650 

 and 775 m. 



At night, larvae «30 mm ML were taken 

 primarily in the upper 50 m; larvae 31 to 40 mm 

 ML were found throughout the upper 200 m. Four- 

 teen juveniles and adults were taken at night be- 

 tween 90 and 225 m; most captures were made 

 between 100 and 200 m. 



Photosensitive Vesicles (Figure 35) 



Phasmatopsis fisheri has a single set of large 

 organs. Each organ consists of a broad, elongate 

 vesicle that extends from the optic gland on the 

 dorsal surface of the optic stalk ventrally over the 

 posterior surface of the peduncle complex onto the 

 side of the ventral subesophageal mass, where it 



A PIG 



PIG.S 



Figure 35. — Photosensitive vesicles oiPhasmatopsis fisheri. A. 

 Larva, 35 mm ML. B. Juvenile, 70 mm ML. C. Adult, 130 mm 

 ML. Abbreviations as in Figure 2. 



bends slightly dorsally. Each organ is thick later- 

 ally and medially. Most of the anterior, medial, 

 and lateral surfaces of each organ are covered by 

 dark brown pigment screen. The dorsal tip of each 

 organ lacks screening pigment on its lateral por- 

 tion and has limited pigment screen on its medial 

 portion. The curvature of each organ allows light 

 to enter various parts from a wide range of angles. 

 The anterior wall of each organ consists of little 

 more than a membrane backed by dense pigment. 

 The posterior wall and the walls of the dorsal and 

 ventral ends of each organ contain 4 or 5 layers of 

 sensory-cell bodies. Sensory processes are longer 

 (215 /Ltm) and thinner (inner diameter 2 to4/>tm) in 

 the ventral parts of the organ than in the dorsal 



200 - 



4 00 - 



Figure 34.— Vertical distribution of 

 Phasmatopsis fisheri. Symbols as in 

 Figure L 



600 - 



800 



m^//^)9om'////A^ ^ »!■ — ' — I — ' — I — ' — I — ' — t — ' — I — ' — r^'-T-'^ 



, • •«( • 



lOOo' I ' ll — ^- 



J J L 



10 20 30 



40 



50 60 70 



MANTLE LENGTH, mm 



80 



90 



I *f \ \ I L. 



100 130 170 



602 



