The control of the hatching process in barnacles

Abstract

The difficulty of obtaining in the laboratory massive liberation of barnacle nauplii comparable with that which occurs in nature led to an investigation of the effect of various factors on the hatching process. The hatching of egg masses in vitro is inhibited only at such low oxygen concentrations as to make the control of hatching by oxygen tension unlikely. Variations in salinity are similarly unlikely to be important in nature. Massive liberation of larvae from animals bearing fully developed embryos can be obtained as a result of feeding them. This effect seems largely independent of the nature of the food given. Extracts of barnacle tissue show activity as a stimulant of hatching when supplied to adult egg-bearing animals or to isolated egg masses in vitro. Extracts from both starved and fed barnacles are equally active, as are extracts from other species of barnacles. Liberation of nauplii by adult animals as a result of feeding is accompanied by the secretion of hatching substance into the water. No other plants or animals tested have yielded active secretions or tissue extracts. The activity of the hatching substance does not depend upon any detectable action on the walls of the egg cases or the matrix of the egg mass, but rather upon the stimulation of the embryo within the egg case. Preliminary chemical investigation of the nature of the hatching substance suggests that it is a product of barnacle tissue metabolism and is a relatively stable, easily diffusible molecule which forms a lactone, lactam, or similar inactive derivative at low pH.