NOTES 



DISTRIBUTION OF MELANIN IN THE 



COLOR PATTERN OF DELPHINUS DELPHIS 



(CETACEA; DELPHINIDAE) 



Previous studies of cetacean pigmentation have 

 been concerned with the description of color pat- 

 terns and the possibilities for their evolutionary 

 production and their adaptive significance. 

 Mitchell (1970) identified four basic color patterns 

 among the Delphinidae: saddled, as exemplified by 

 some species of Stenella; spotted, as seen in 

 Stenella plagiodon; striped, as seen in Stenella 

 coeruleoalba; and crisscross, as seen in Delphinus 

 del-phis. Naming the crisscross pattern as the most 

 complex, Mitchell used it to establish a ter- 

 minology for elements of the color patterns. One 

 of his conclusions concerning the evolutionary 

 development of the patterns was that the saddled 

 pattern is most primitive, since it is closest to 

 generalized countershading and because one may 

 hypothetically derive the other three patterns 

 from it by addition of certain features, emphasis 

 of some features, and de-emphasis of others. 



Perrin (1972) compared the color pattern of a 

 partially albinistic whitebelly spinner (S. lon- 

 girostris) with that of a normally pigmented in- 

 dividual and showed that the normal color pattern 

 may be described in terms of two independently 

 produced but interacting pigmentation systems or 

 components, only one of which had developed in 

 the partially albinistic individual. Using the two- 

 component approach, he analyzed the color pat- 

 terns of other delphinids, including Delphinus 

 spp., and proposed pattern homologies among the 

 species. He suggested that the more generalized of 

 the two pigmentation systems involves the cape 

 (terminology of Perrin 1970) and its accessory 

 stripes, eye and gape marks, and dorsal fin and 

 fluke colorations. This is overlaid by a second 

 component system that he named the "dorsal 

 overlay system." He proposed that partial 

 overlapping of the two produces the four-part 

 crisscross pattern in Delphinus. 



If two discrete interacting pigmentation sys- 

 tems are involved in the color pattern of 

 Delphinus, that fact should be evidenced in the 

 microstructure of the skin. Previous histological 

 study of Delphinus skin provides only a descrip- 

 tion of the general microscopic anatomy. Stigl- 



bauer (1913) described the microstructure of the 

 skin of Delphinus delphis in great detail, including 

 the existence of large dermal papillae and epider- 

 mal pegs with granular inclusions of pigment that 

 he identified as melanin. His sample, however, was 

 from the back of a single animal, and he did not 

 have the opportunity to compare the distributions 

 of pigment in different parts of the color pattern. 

 Sokolov (1962) commented very briefly on the pig- 

 mentation of two specimens of Delphinus, stating 

 that the epidermis on the back and below the dor- 

 sal fin was moderately pigmented, on the side of 

 one animal was lightly pigmented, and along the 

 side of the other animal and on the bellies of both 

 was unpigmented. This paper reports the results 

 of comparative microscopic examination of skin 

 samples taken from various areas of the color 

 pattern. 



Materials and Methods 



Skin samples, each about 5 cm square, were 

 taken from various areas of the bodies of two 

 animals as shown in Figure 1. The porpoise were 

 collected at San Diego, Calif. One animal (field no. 

 WFP 125, adult female, 176 cm, 61 kg) had been 

 frozen for several months before dissection, and 

 the other (WFP 221, adult male, 185 cm, 83 kg, 

 Figure 2) was sampled about 1 h after death. 



One centimeter-square specimens were fixed in 

 10% Formalin,' and imbedded in paraffin. Sections 

 were cut 8 ixm thick and stained with Schmorl's 

 ferricyanide for malinin. This method stains 

 melanins a dark blue or blue-green, while other 

 epidermal and dermal tissue is stained light 

 green. 



The prepared sections were examined under a 

 light microscope. Pigment densities were scored at 

 125 diameters magnification. 



Results 



General microscopic anatomy of the skin of 

 Delphinus is simple when compared with that of 

 terrestrial mammals and fits the description of 

 cetacean skin given by Simpson and Gardner 



'Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



439 



