ON THE 



STRUCTURE OF THE PHOTOPHORES 



OF SOME DECAPOD CRUSTACEA 



By Ralph Dennell, D.Sc. 

 (Plates XXIV-XXVI ; Text-figs. 1-3 1) 



I. INTRODUCTION 



rj^HE first authentic account of the presence of numerous well-defined photophores in 

 i a member of the Crustacea Decapoda appears to have been given by Hansen (1903). 

 In a new species of Sergestes obtained by the Challenger Expedition and named by him 

 S challengeri he described the structure of a large number of small dermal bodies 

 equipped with chitinous lenses, and expressed the view that their function was one of 

 light production. It is true that before this, in 1886, Perrier had mentioned the existence 

 of photophores in Acanthephyra pellucida, but his account appears to be of doubtful 

 reliability (see Kemp, 1910^ p. 642, and Hansen, 1903, p. 76)- Since then further 

 observations on the structural details of Decapod photophores have been made, notably 

 by Kemp (19106), Terao (1917), and Ramadan (1938), but in general the available 

 information on photophores is scattered throughout the literature relating to taxonomy. 



It was with the object of examining the detailed structure of some of the many organs 

 in the Penaeidea and Caridea which have either been suspected or have been definitely 

 shown to be luminous that the present investigation was undertaken at the suggestion 

 of Dr S W Kemp. To him I am deeply indebted, not only for the gift of all the 

 material used and for the loan of his notes made on board the 'Discovery' and the 

 ' Discovery IF, but for much valuable advice and encouragement during the course of 

 the work. My sincere thanks are also due to Professor H. Graham Cannon for his 

 continued interest and helpful criticism, and for his kindness in photographmg for me 

 the sections represented in Plate XXIV, figs. 2-5, and Plate XXVI, figs, i, 3, 4- and 6. 

 Dr M. D. Burkenroad has kindly described to me the appearance of the liver photo- 

 phores of living species of Sergestes and has given me much valuable information. 



The work has been carried out in the Departments of Zoology of the University of 

 Manchester and the Imperial College of Science and Technology. 



II. MATERIAL AND METHODS 



The material on which this work was begun consisted of a number of specimens 

 from the Discovery Expeditions. They included species of Sergestes, one possessing 

 a new type of superficial photophore, and the remainder with organs of Pesta, or 

 luminous liver tubules; a number of specimens of Parapandalus richardi, also with 



1-3 



