NATURAL HISTORY OF AMERICAN LOBSTER. IQI 



COLOR IN THE ADULT LOBSTER. 



The color of the adult lobster is due primarily to the presence of pigments, either in 

 a state of solution in the blood or in the form of granules in the protoplasm of certain 

 cells, particularly the chromatoblasts, which lie beneath the cuticular epithelium. The 

 chromatoblasts are richly supplied with blood, which flows in a system of irregular 

 anuses through the spongy tissues underlying the epidermis. 



In the adult lobster the hard shell is an opaque lifeless substance, and the pigments 

 to which it owes its characteristic coloring are excreted by the chromatoblasts of the 

 soft underlying skin. These are immediately exposed upon removing the shell. The 

 delicate skin is seen to be flecked or mottled with scarlet, and with the aid of a simple 

 magnifying glass it is readily perceived that its color is due to branching pigment cells, 

 groups of which correspond to the blotches of color on the shell itself. The excreted 

 pigments undergo physical and possibly chemical changes in the hard cuticular shell 

 and may thus come to differ markedly in color from the parent chromatoblasts. Since 

 the colors of the lobster reside in a lifeless body, the pigment layer of the shell, it is 

 evident that no changes of a vital nature can take place after this is definitely formed. 



The coloration of the lobster is fairly uniform in plan, but extremely variable in 

 details, even more so than we find in the case of the color patterns of many insects. 

 The brilliancy and purity of the shell pigments depend largely upon the age of the shell 

 or upon its condition with respect to the molting period. These pigments are usually 

 most brilliant just after the molt, when the cuticle is thin and translucent, and dullest 

 before ecdysis begins, when the old shell still encumbers the body. 



The pigment cells themselves, as we have seen, reside in the soft skin, and when 

 the shell is once hardened the color of the animal is more or less fixed and permanent. 

 It is certain, however, that under the action of light and possibly from other natural 

 causes the shell pigments undergo molecular or chemical changes. Men who handle 

 lobsters have frequently observed that when they are exposed in shallow cars to unusually 

 intense light they become decidedly bluer in color. 



According to MacMunn (iS^) the coloring of the skin of the lobster is due to the 

 presence of chromogens, which may be converted on slight provocation, as by dehy- 

 dration, oxidation, or some molecular change, into a red Upochrome resembUng rhodo- 

 phan. Everyone is familiar with the wonderful change in color which the hving lobster 

 undergoes when boiled, and according to the same writer the beautiful pigment of the 

 larval lobster is converted by alcohol into a true Upochrome. 



Alcohol quickly converts the chromogens in the lobster's shell into lipochromes 

 and dissolves them at the same time. This is seen when a recently molted lobster with 

 brilliant coloring is placed in alcohol for preservation. The soft shell is first reddened, 

 and then in a short time completely bleached, while a hard lobster treated in the same 

 way will retain much of its shell pigment for years, if not indefinitely. 



Lipochromogens are found in a natural state in the gastric glands, blood, soft skin 

 (as the blue prismatic cyano-crystals, which are reddened by alcohol or by boiling), 



