DEVELOPMENT OF THE LANTERNFISH, SCOPELOPSIS MULTIPUNCTATUS 



BRAUER 1906, WITH A DISCUSSION OF ITS PHYLOGENETIC 



POSITION IN THE FAMILY MYCTOPHIDAE AND ITS ROLE IN A 



PROPOSED MECHANISM FOR THE EVOLUTION OF PHOTOPHORE 



PATTERNS IN LANTERNFISHES 



H. Geoffrey Moser and Elbert H. Ahlstrom^ 



ABSTRACT 



The larval and transformation stages of the unusual myctophid, Scopelopsis multipunc- 

 tatus Brauer, are described. A character that the larvae of Scopelopsis share with a 

 number of other genera in the Lampanyctinae is the sequential development of three or 

 more pairs of early forming photophores. The sequence of development of early forming 

 photophores is shown to be an especially useful character in revealing phylogenetic affini- 

 ties when used in conjunction with other larval characters, such as body shape and pig- 

 ment pattern. From our study of the development of Scopelopsis, a possible mechanism 

 for the evolution of photophore patterns within the family Myctophidae is presented. 



Brauer (1906) , in his elegant report on the fishes 

 collected during the German Deep-Sea Expedi- 

 tion of 1898-99, described for the first time a 

 remarkable lanternfish, for which he established 

 the genus Scopelopsis. His single specimen, a 

 newly transformed juvenile, was unique in hav- 

 ing the head and body studded with minute light 

 organs, all of approximately the same size. All 

 other lanternfish known to him were character- 

 ized by a specific pattern of photophores on the 

 head and on the ventral and lateral regions of 

 the body. These he grouped into the single genus 

 Myctophum, under which he recognized four 

 subgenera: Myctophum, Diaphus, Lampanyctus, 

 and Lampadena. These two genera, along with 

 Neoscopelus, a genus with an undiflFerentiated 

 pattern of ventral photophores, and five other 

 genera were included in the family Scopelidae. 

 Regan (1911) modified drastically this taxo- 

 nomic arrangement by distributing Brauer's 

 eight genera of scopelids into a scheme of three 

 suborders. He placed the family Myctophidae 

 within one of these suborders and included with- 



^ National Marine Fisheries Service, Southwest Fish- 

 eries Center, La Jolla, CA 92037. 



Manuscript accepted April 1972, 



FISHERY BULLETIN: VOL. 70, NO. 3, 1972. 



in it seven genera: Scopelopsis, Neoscopelus, 

 Scopelengys (a genus related to Neoscopelus but 

 lacking photophores) , and the four subgenera of 

 Brauer raised to generic rank. Parr (1928) 

 further differentiated the family Myctophidae 

 to include three subfamilies: Scopelengini for 

 Scopelengys, Neoscopelini for Neoscopelus, and 

 Scopelopsis, and Myctophini for Myctophum, 

 Lampanyctus, Diaphus, and Lampadena. 



Taning (1932) noted that in a number of well- 

 preserved specimens of Scopelopsis, certain pho- 

 tophores were larger and better developed than 

 others, and that the scales covering these organs 

 were equipped with the same lens-like modifica- 

 tion typical of other members of Parr's Myctoph- 

 ini. He observed further that these larger photo- 

 phores formed a pattern that corresponded with 

 the kinds of photophore patterns found in the 

 Myctophini and concluded, accordingly, that 

 Scopelopsis belonged with Myctophum, Lampa- 

 nyctus, and relatives in the subfamily Myctoph- 

 ini, 



Fraser-Brunner (1949) reduced the number of 

 subfamilies in the Myctophidae to two: The 

 Neoscopelinae, to include Neoscopelus, Scopelen- 

 gys, and Solivomer, and the Myctophinae, to in- 



541 



