THE HISTOLOGICAL BASIS OF ADAPTIVE SHADES AND COLORS 

 IN THE FLOUNDER FARALICHTHYS ALBIGUTTUS. 



By ALBERT KUNTZ, PH. D. 



06 



Contribution from the United States Fisheries Biological Station, Beaufort, N. C, and the Anatomical 

 Laboratories of the St. Louis University School of Medicine. 



INTRODUCTION. 



Changes m shade, color, and pattern which, as is well known, occur in many bony 

 fishes are due primarily to changes in the distribution of the pigment granules in the 

 chromatophores in the skin and changes in the relationships of the guanophores (cells 

 containing guanin crystals) with these chromatic organs. 



The present investigation « is an attempt to determine as accurately as possible the 

 behavior of the chromatophores and other elements involved in the production of color 

 in the skin of the flounder Paralichthys albiguttus, as it undergoes changes in shade 

 or color or simulates as nearly as possible the color of a given background. 



MATERIAL AND METHODS. 



The material used in this investigation consisted of a large number of specimens of 

 Paralichthys albiguttus ranging from lo to 30 cm. in length. Many of these specimens 

 were kept in aquaria of chosen colors continuously for three weeks or longer, others 

 for briefer intervals. 



Observations were made largely on living and fresh material. Sections of pre- 

 served skin were used primarily for the study of the distribution of pigment in the 

 deeper layers of the skin and the relationships of the color producing elements with 

 each other and with other structural elements in the skin in a vertical plane. 



The chromatophores and guanophores lying immediately beneath the epidermis 

 can be observed very satisfactorily on detached scales on which the epidermis remains 

 intact. The removal of a few scales, if done carefully, causes little or no reaction on 

 the part of the fish, and, consequently, no changes in the distribution of the pigment in 

 the chromatophores. If these scales are mounted in sea water, no changes in the distri- 

 bution of pigment granules occur for a considerable interval. When preparations of the 

 whole skin were desired, the fish was killed instantaneously by chopping off the head 



oThis in vestigation was undertaken at the suggestion of Dr. S. O.Mast as a sequel to his work on "Changes in shade, color, 

 and pattern in fishes, and their bearing on the problems of adaptation and behavior, with especial reference to the flounders 

 Paralichthys and Ancylopsetta." Bulletin of the United States Bureau of Fisheries, vol. xxxiv, i9i4,p. 176-238. Paralichthys 

 albiijuttus was selected because it was found by Dr. Mast to be highly adaptable to backgrounds of various shades and colors and 

 was used extensively in his work. The author is indebted to Dr. Mast, also, for helpful suggestions and reading the manuscript. 



